net_processing.cpp

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// Copyright (c) 2009-2010 Satoshi Nakamoto
// Copyright (c) 2009-2016 The Bitcoin Core developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.
 
#include <net_processing.h>
 
#include <addrman.h>
#include <avalanche/compactproofs.h>
#include <avalanche/peermanager.h>
#include <avalanche/processor.h>
#include <avalanche/proof.h>
#include <avalanche/stakecontender.h>
#include <avalanche/statistics.h>
#include <avalanche/validation.h>
#include <banman.h>
#include <blockencodings.h>
#include <blockfilter.h>
#include <blockvalidity.h>
#include <chain.h>
#include <chainparams.h>
#include <config.h>
#include <consensus/amount.h>
#include <consensus/validation.h>
#include <hash.h>
#include <headerssync.h>
#include <index/blockfilterindex.h>
#include <invrequest.h>
#include <kernel/chain.h>
#include <kernel/mempool_entry.h>
#include <merkleblock.h>
#include <netbase.h>
#include <netmessagemaker.h>
#include <node/blockstorage.h>
#include <node/miner.h>
#include <policy/fees.h>
#include <policy/policy.h>
#include <policy/settings.h>
#include <primitives/block.h>
#include <primitives/transaction.h>
#include <random.h>
#include <reverse_iterator.h>
#include <scheduler.h>
#include <streams.h>
#include <timedata.h>
#include <tinyformat.h>
#include <txmempool.h>
#include <txorphanage.h>
#include <util/check.h>
#include <util/strencodings.h>
#include <util/trace.h>
#include <validation.h>
 
#include <boost/multi_index/hashed_index.hpp>
#include <boost/multi_index/member.hpp>
#include <boost/multi_index/ordered_index.hpp>
#include <boost/multi_index_container.hpp>
 
#include <algorithm>
#include <atomic>
#include <chrono>
#include <functional>
#include <future>
#include <memory>
#include <numeric>
#include <typeinfo>
#include <utility>
 
static constexpr auto UNCONDITIONAL_RELAY_DELAY = 2min;
static constexpr auto HEADERS_DOWNLOAD_TIMEOUT_BASE = 15min;
static constexpr auto HEADERS_DOWNLOAD_TIMEOUT_PER_HEADER = 1ms;
static constexpr auto HEADERS_RESPONSE_TIME{2min};
static constexpr int32_t MAX_OUTBOUND_PEERS_TO_PROTECT_FROM_DISCONNECT = 4;
static constexpr auto CHAIN_SYNC_TIMEOUT{20min};
static constexpr auto STALE_CHECK_INTERVAL{10min};
static constexpr auto EXTRA_PEER_CHECK_INTERVAL{45s};
static constexpr auto MINIMUM_CONNECT_TIME{30s};
static constexpr uint64_t RANDOMIZER_ID_ADDRESS_RELAY = 0x3cac0035b5866b90ULL;
static constexpr int STALE_RELAY_AGE_LIMIT = 30 * 24 * 60 * 60;
static constexpr int HISTORICAL_BLOCK_AGE = 7 * 24 * 60 * 60;
static constexpr auto PING_INTERVAL{2min};
static const unsigned int MAX_LOCATOR_SZ = 101;
static const unsigned int MAX_INV_SZ = 50000;
static_assert(MAX_PROTOCOL_MESSAGE_LENGTH > MAX_INV_SZ * sizeof(CInv),
              "Max protocol message length must be greater than largest "
              "possible INV message");
 
static constexpr auto GETAVAADDR_INTERVAL{2min};
 
static constexpr auto AVALANCHE_AVAPROOFS_TIMEOUT{2min};
 
static constexpr size_t MAX_AVALANCHE_STALLED_TXIDS_PER_PEER{100};
 
struct DataRequestParameters {
    const size_t max_peer_request_in_flight;
 
    const size_t max_peer_announcements;
 
    const std::chrono::seconds nonpref_peer_delay;
 
    const std::chrono::seconds overloaded_peer_delay;
 
    const std::chrono::microseconds getdata_interval;
 
    const NetPermissionFlags bypass_request_limits_permissions;
};
 
static constexpr DataRequestParameters TX_REQUEST_PARAMS{
    100,                       // max_peer_request_in_flight
    5000,                      // max_peer_announcements
    std::chrono::seconds(2),   // nonpref_peer_delay
    std::chrono::seconds(2),   // overloaded_peer_delay
    std::chrono::seconds(60),  // getdata_interval
    NetPermissionFlags::Relay, // bypass_request_limits_permissions
};
 
static constexpr DataRequestParameters PROOF_REQUEST_PARAMS{
    100,                      // max_peer_request_in_flight
    5000,                     // max_peer_announcements
    std::chrono::seconds(2),  // nonpref_peer_delay
    std::chrono::seconds(2),  // overloaded_peer_delay
    std::chrono::seconds(60), // getdata_interval
    NetPermissionFlags::
        BypassProofRequestLimits, // bypass_request_limits_permissions
};
 
static const unsigned int MAX_GETDATA_SZ = 1000;
static const int MAX_BLOCKS_IN_TRANSIT_PER_PEER = 16;
static constexpr auto BLOCK_STALLING_TIMEOUT_DEFAULT{2s};
static constexpr auto BLOCK_STALLING_TIMEOUT_MAX{64s};
static const int MAX_CMPCTBLOCK_DEPTH = 5;
static const int MAX_BLOCKTXN_DEPTH = 10;
static_assert(MAX_BLOCKTXN_DEPTH <= MIN_BLOCKS_TO_KEEP,
              "MAX_BLOCKTXN_DEPTH too high");
static const unsigned int BLOCK_DOWNLOAD_WINDOW = 1024;
static constexpr double BLOCK_DOWNLOAD_TIMEOUT_BASE = 1;
static constexpr double BLOCK_DOWNLOAD_TIMEOUT_PER_PEER = 0.5;
static const unsigned int MAX_BLOCKS_TO_ANNOUNCE = 8;
static const unsigned int NODE_NETWORK_LIMITED_MIN_BLOCKS = 288;
static constexpr auto AVG_LOCAL_ADDRESS_BROADCAST_INTERVAL{24h};
static constexpr auto AVG_ADDRESS_BROADCAST_INTERVAL{30s};
static constexpr auto ROTATE_ADDR_RELAY_DEST_INTERVAL{24h};
static constexpr auto INBOUND_INVENTORY_BROADCAST_INTERVAL{5s};
static constexpr unsigned int INVENTORY_BROADCAST_PER_SECOND = 7;
static constexpr unsigned int INVENTORY_BROADCAST_MAX_PER_MB =
    INVENTORY_BROADCAST_PER_SECOND *
    count_seconds(INBOUND_INVENTORY_BROADCAST_INTERVAL);
static constexpr unsigned int INVENTORY_MAX_RECENT_RELAY = 3500;
static_assert(INVENTORY_MAX_RECENT_RELAY >= INVENTORY_BROADCAST_PER_SECOND *
                                                UNCONDITIONAL_RELAY_DELAY /
                                                std::chrono::seconds{1},
              "INVENTORY_RELAY_MAX too low");
 
static constexpr auto AVG_FEEFILTER_BROADCAST_INTERVAL{10min};
static constexpr auto MAX_FEEFILTER_CHANGE_DELAY{5min};
static constexpr uint32_t MAX_GETCFILTERS_SIZE = 1000;
static constexpr uint32_t MAX_GETCFHEADERS_SIZE = 2000;
static constexpr size_t MAX_PCT_ADDR_TO_SEND = 23;
static constexpr double MAX_ADDR_RATE_PER_SECOND{0.1};
static constexpr size_t MAX_ADDR_PROCESSING_TOKEN_BUCKET{MAX_ADDR_TO_SEND};
static constexpr uint64_t CMPCTBLOCKS_VERSION{1};
 
// Internal stuff
namespace {
struct QueuedBlock {
    const CBlockIndex *pindex;
    std::unique_ptr<PartiallyDownloadedBlock> partialBlock;
};
 
struct StalledTxId {
    TxId txid;
    std::chrono::seconds timeAdded;
 
    StalledTxId(TxId txid_, std::chrono::seconds timeAdded_)
        : txid(txid_), timeAdded(timeAdded_){};
};
 
struct by_txid {};
struct by_time {};
 
using StalledTxIdSet = boost::multi_index_container<
    StalledTxId,
    boost::multi_index::indexed_by<
        // sort by txid
        boost::multi_index::hashed_unique<
            boost::multi_index::tag<by_txid>,
            boost::multi_index::member<StalledTxId, TxId, &StalledTxId::txid>,
            SaltedTxIdHasher>,
        // sort by timeAdded
        boost::multi_index::ordered_non_unique<
            boost::multi_index::tag<by_time>,
            boost::multi_index::member<StalledTxId, std::chrono::seconds,
                                       &StalledTxId::timeAdded>>>>;
 
struct Peer {
    const NodeId m_id{0};
 
    const ServiceFlags m_our_services;
 
    std::atomic<ServiceFlags> m_their_services{NODE_NONE};
 
    Mutex m_misbehavior_mutex;
    bool m_should_discourage GUARDED_BY(m_misbehavior_mutex){false};
 
    Mutex m_block_inv_mutex;
    std::vector<BlockHash> m_blocks_for_inv_relay GUARDED_BY(m_block_inv_mutex);
    std::vector<BlockHash>
        m_blocks_for_headers_relay GUARDED_BY(m_block_inv_mutex);
 
    BlockHash m_continuation_block GUARDED_BY(m_block_inv_mutex){};
 
    std::atomic<int> m_starting_height{-1};
 
    std::atomic<uint64_t> m_ping_nonce_sent{0};
    std::atomic<std::chrono::microseconds> m_ping_start{0us};
    std::atomic<bool> m_ping_queued{false};
 
    Amount m_fee_filter_sent GUARDED_BY(NetEventsInterface::g_msgproc_mutex){
        Amount::zero()};
    std::chrono::microseconds m_next_send_feefilter
        GUARDED_BY(NetEventsInterface::g_msgproc_mutex){0};
 
    struct TxRelay {
        mutable RecursiveMutex m_bloom_filter_mutex;
        bool m_relay_txs GUARDED_BY(m_bloom_filter_mutex){false};
        std::unique_ptr<CBloomFilter>
            m_bloom_filter PT_GUARDED_BY(m_bloom_filter_mutex)
                GUARDED_BY(m_bloom_filter_mutex){nullptr};
 
        CRollingBloomFilter m_recently_announced_invs GUARDED_BY(
            NetEventsInterface::g_msgproc_mutex){INVENTORY_MAX_RECENT_RELAY,
                                                 0.000001};
 
        mutable RecursiveMutex m_tx_inventory_mutex;
        CRollingBloomFilter m_tx_inventory_known_filter
            GUARDED_BY(m_tx_inventory_mutex){50000, 0.000001};
        std::set<TxId> m_tx_inventory_to_send GUARDED_BY(m_tx_inventory_mutex);
        bool m_send_mempool GUARDED_BY(m_tx_inventory_mutex){false};
        std::atomic<std::chrono::seconds> m_last_mempool_req{0s};
        std::chrono::microseconds
            m_next_inv_send_time GUARDED_BY(m_tx_inventory_mutex){0};
 
        std::atomic<Amount> m_fee_filter_received{Amount::zero()};
 
        StalledTxIdSet
            m_avalanche_stalled_txids GUARDED_BY(m_tx_inventory_mutex);
    };
 
    /*
     * Initializes a TxRelay struct for this peer. Can be called at most once
     * for a peer.
     */
    TxRelay *SetTxRelay() EXCLUSIVE_LOCKS_REQUIRED(!m_tx_relay_mutex) {
        LOCK(m_tx_relay_mutex);
        Assume(!m_tx_relay);
        m_tx_relay = std::make_unique<Peer::TxRelay>();
        return m_tx_relay.get();
    };
 
    TxRelay *GetTxRelay() EXCLUSIVE_LOCKS_REQUIRED(!m_tx_relay_mutex) {
        return WITH_LOCK(m_tx_relay_mutex, return m_tx_relay.get());
    };
    const TxRelay *GetTxRelay() const
        EXCLUSIVE_LOCKS_REQUIRED(!m_tx_relay_mutex) {
        return WITH_LOCK(m_tx_relay_mutex, return m_tx_relay.get());
    };
 
    struct ProofRelay {
        mutable RecursiveMutex m_proof_inventory_mutex;
        std::set<avalanche::ProofId>
            m_proof_inventory_to_send GUARDED_BY(m_proof_inventory_mutex);
        // Prevent sending proof invs if the peer already knows about them
        CRollingBloomFilter m_proof_inventory_known_filter
            GUARDED_BY(m_proof_inventory_mutex){10000, 0.000001};
        CRollingBloomFilter m_recently_announced_proofs GUARDED_BY(
            NetEventsInterface::g_msgproc_mutex){INVENTORY_MAX_RECENT_RELAY,
                                                 0.000001};
        std::chrono::microseconds m_next_inv_send_time{0};
 
        RadixTree<const avalanche::Proof, avalanche::ProofRadixTreeAdapter>
            sharedProofs;
        std::atomic<std::chrono::seconds> lastSharedProofsUpdate{0s};
        std::atomic<bool> compactproofs_requested{false};
    };
 
    const std::unique_ptr<ProofRelay> m_proof_relay;
 
    std::vector<CAddress>
        m_addrs_to_send GUARDED_BY(NetEventsInterface::g_msgproc_mutex);
    std::unique_ptr<CRollingBloomFilter>
        m_addr_known GUARDED_BY(NetEventsInterface::g_msgproc_mutex);
    std::atomic_bool m_addr_relay_enabled{false};
    bool m_getaddr_sent GUARDED_BY(NetEventsInterface::g_msgproc_mutex){false};
    mutable Mutex m_addr_send_times_mutex;
    std::chrono::microseconds
        m_next_addr_send GUARDED_BY(m_addr_send_times_mutex){0};
    std::chrono::microseconds
        m_next_local_addr_send GUARDED_BY(m_addr_send_times_mutex){0};
    std::atomic_bool m_wants_addrv2{false};
    bool m_getaddr_recvd GUARDED_BY(NetEventsInterface::g_msgproc_mutex){false};
    mutable Mutex m_addr_token_bucket_mutex;
    double m_addr_token_bucket GUARDED_BY(m_addr_token_bucket_mutex){1.0};
    std::chrono::microseconds
        m_addr_token_timestamp GUARDED_BY(NetEventsInterface::g_msgproc_mutex){
            GetTime<std::chrono::microseconds>()};
    std::atomic<uint64_t> m_addr_rate_limited{0};
    std::atomic<uint64_t> m_addr_processed{0};
 
    bool m_inv_triggered_getheaders_before_sync
        GUARDED_BY(NetEventsInterface::g_msgproc_mutex){false};
 
    Mutex m_getdata_requests_mutex;
    std::deque<CInv> m_getdata_requests GUARDED_BY(m_getdata_requests_mutex);
 
    NodeClock::time_point m_last_getheaders_timestamp
        GUARDED_BY(NetEventsInterface::g_msgproc_mutex){};
 
    Mutex m_headers_sync_mutex;
    std::unique_ptr<HeadersSyncState>
        m_headers_sync PT_GUARDED_BY(m_headers_sync_mutex)
            GUARDED_BY(m_headers_sync_mutex){};
 
    std::atomic<bool> m_sent_sendheaders{false};
 
    std::chrono::microseconds m_headers_sync_timeout
        GUARDED_BY(NetEventsInterface::g_msgproc_mutex){0us};
 
    bool m_prefers_headers GUARDED_BY(NetEventsInterface::g_msgproc_mutex){
        false};
 
    explicit Peer(NodeId id, ServiceFlags our_services, bool fRelayProofs)
        : m_id(id), m_our_services{our_services},
          m_proof_relay(fRelayProofs ? std::make_unique<ProofRelay>()
                                     : nullptr) {}
 
private:
    mutable Mutex m_tx_relay_mutex;
 
    std::unique_ptr<TxRelay> m_tx_relay GUARDED_BY(m_tx_relay_mutex);
};
 
using PeerRef = std::shared_ptr<Peer>;
 
struct CNodeState {
    const CBlockIndex *pindexBestKnownBlock{nullptr};
    BlockHash hashLastUnknownBlock{};
    const CBlockIndex *pindexLastCommonBlock{nullptr};
    const CBlockIndex *pindexBestHeaderSent{nullptr};
    bool fSyncStarted{false};
    std::chrono::microseconds m_stalling_since{0us};
    std::list<QueuedBlock> vBlocksInFlight;
    std::chrono::microseconds m_downloading_since{0us};
    bool fPreferredDownload{false};
    bool m_requested_hb_cmpctblocks{false};
    bool m_provides_cmpctblocks{false};
 
    struct ChainSyncTimeoutState {
        std::chrono::seconds m_timeout{0s};
        const CBlockIndex *m_work_header{nullptr};
        bool m_sent_getheaders{false};
        bool m_protect{false};
    };
 
    ChainSyncTimeoutState m_chain_sync;
 
    int64_t m_last_block_announcement{0};
 
    const bool m_is_inbound;
 
    CNodeState(bool is_inbound) : m_is_inbound(is_inbound) {}
};
 
class PeerManagerImpl final : public PeerManager {
public:
    PeerManagerImpl(CConnman &connman, AddrMan &addrman, BanMan *banman,
                    ChainstateManager &chainman, CTxMemPool &pool,
                    avalanche::Processor *const avalanche, Options opts);
 
    void BlockConnected(ChainstateRole role,
                        const std::shared_ptr<const CBlock> &pblock,
                        const CBlockIndex *pindexConnected) override
        EXCLUSIVE_LOCKS_REQUIRED(!m_recent_confirmed_transactions_mutex);
    void BlockDisconnected(const std::shared_ptr<const CBlock> &block,
                           const CBlockIndex *pindex) override
        EXCLUSIVE_LOCKS_REQUIRED(!m_recent_confirmed_transactions_mutex);
    void UpdatedBlockTip(const CBlockIndex *pindexNew,
                         const CBlockIndex *pindexFork,
                         bool fInitialDownload) override
        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex);
    void BlockChecked(const CBlock &block,
                      const BlockValidationState &state) override
        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex);
    void NewPoWValidBlock(const CBlockIndex *pindex,
                          const std::shared_ptr<const CBlock> &pblock) override
        EXCLUSIVE_LOCKS_REQUIRED(!m_most_recent_block_mutex);
 
    void InitializeNode(const Config &config, CNode &node,
                        ServiceFlags our_services) override
        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex);
    void FinalizeNode(const Config &config, const CNode &node) override
        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, !cs_proofrequest,
                                 !m_headers_presync_mutex);
    bool ProcessMessages(const Config &config, CNode *pfrom,
                         std::atomic<bool> &interrupt) override
        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex,
                                 !m_recent_confirmed_transactions_mutex,
                                 !m_most_recent_block_mutex, !cs_proofrequest,
                                 !m_headers_presync_mutex, g_msgproc_mutex);
    bool SendMessages(const Config &config, CNode *pto) override
        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex,
                                 !m_recent_confirmed_transactions_mutex,
                                 !m_most_recent_block_mutex, !cs_proofrequest,
                                 g_msgproc_mutex);
 
    void StartScheduledTasks(CScheduler &scheduler) override;
    void CheckForStaleTipAndEvictPeers() override;
    std::optional<std::string>
    FetchBlock(const Config &config, NodeId peer_id,
               const CBlockIndex &block_index) override;
    bool GetNodeStateStats(NodeId nodeid, CNodeStateStats &stats) const override
        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex);
    bool IgnoresIncomingTxs() override { return m_opts.ignore_incoming_txs; }
    void SendPings() override EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex);
    void RelayTransaction(const TxId &txid) override
        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex);
    void RelayProof(const avalanche::ProofId &proofid) override
        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex);
    void SetBestHeight(int height) override { m_best_height = height; };
    void UnitTestMisbehaving(NodeId peer_id) override
        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex) {
        Misbehaving(*Assert(GetPeerRef(peer_id)), "");
    }
    void ProcessMessage(const Config &config, CNode &pfrom,
                        const std::string &msg_type, DataStream &vRecv,
                        const std::chrono::microseconds time_received,
                        const std::atomic<bool> &interruptMsgProc) override
        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex,
                                 !m_recent_confirmed_transactions_mutex,
                                 !m_most_recent_block_mutex, !cs_proofrequest,
                                 !m_headers_presync_mutex, g_msgproc_mutex);
    void UpdateLastBlockAnnounceTime(NodeId node,
                                     int64_t time_in_seconds) override;
 
private:
    void ConsiderEviction(CNode &pto, Peer &peer,
                          std::chrono::seconds time_in_seconds)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main, g_msgproc_mutex);
 
    void EvictExtraOutboundPeers(std::chrono::seconds now)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
    void ReattemptInitialBroadcast(CScheduler &scheduler)
        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex);
 
    void UpdateAvalancheStatistics() const;
 
    void AvalanchePeriodicNetworking(CScheduler &scheduler) const;
 
    PeerRef GetPeerRef(NodeId id) const EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex);
 
    PeerRef RemovePeer(NodeId id) EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex);
 
    void Misbehaving(Peer &peer, const std::string &message);
 
    void MaybePunishNodeForBlock(NodeId nodeid,
                                 const BlockValidationState &state,
                                 bool via_compact_block,
                                 const std::string &message = "")
        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex);
 
    void MaybePunishNodeForTx(NodeId nodeid, const TxValidationState &state,
                              const std::string &message = "")
        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex);
 
    bool MaybeDiscourageAndDisconnect(CNode &pnode, Peer &peer);
 
    void ProcessInvalidTx(NodeId nodeid, const CTransactionRef &tx,
                          const TxValidationState &result,
                          bool maybe_add_extra_compact_tx)
        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, g_msgproc_mutex, cs_main);
 
    struct PackageToValidate {
        const Package m_txns;
        const std::vector<NodeId> m_senders;
        explicit PackageToValidate(const CTransactionRef &parent,
                                   const CTransactionRef &child,
                                   NodeId parent_sender, NodeId child_sender)
            : m_txns{parent, child}, m_senders{parent_sender, child_sender} {}
 
        std::string ToString() const {
            Assume(m_txns.size() == 2);
            return strprintf(
                "parent %s (sender=%d) + child %s (sender=%d)",
                m_txns.front()->GetId().ToString(), m_senders.front(),
                m_txns.back()->GetId().ToString(), m_senders.back());
        }
    };
 
    void ProcessPackageResult(const PackageToValidate &package_to_validate,
                              const PackageMempoolAcceptResult &package_result)
        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, g_msgproc_mutex, cs_main);
 
    std::optional<PackageToValidate> Find1P1CPackage(const CTransactionRef &ptx,
                                                     NodeId nodeid)
        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, g_msgproc_mutex, cs_main);
 
    void ProcessValidTx(NodeId nodeid, const CTransactionRef &tx)
        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, g_msgproc_mutex, cs_main);
 
    bool ProcessOrphanTx(const Config &config, Peer &peer)
        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, g_msgproc_mutex);
 
    void ProcessHeadersMessage(const Config &config, CNode &pfrom, Peer &peer,
                               std::vector<CBlockHeader> &&headers,
                               bool via_compact_block)
        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, !m_headers_presync_mutex,
                                 g_msgproc_mutex);
 
    // Various helpers for headers processing, invoked by
    // ProcessHeadersMessage()
    bool CheckHeadersPoW(const std::vector<CBlockHeader> &headers,
                         const Consensus::Params &consensusParams, Peer &peer);
    arith_uint256 GetAntiDoSWorkThreshold();
    void HandleUnconnectingHeaders(CNode &pfrom, Peer &peer,
                                   const std::vector<CBlockHeader> &headers)
        EXCLUSIVE_LOCKS_REQUIRED(g_msgproc_mutex);
    bool
    CheckHeadersAreContinuous(const std::vector<CBlockHeader> &headers) const;
    bool IsContinuationOfLowWorkHeadersSync(Peer &peer, CNode &pfrom,
                                            std::vector<CBlockHeader> &headers)
        EXCLUSIVE_LOCKS_REQUIRED(peer.m_headers_sync_mutex,
                                 !m_headers_presync_mutex, g_msgproc_mutex);
    bool TryLowWorkHeadersSync(Peer &peer, CNode &pfrom,
                               const CBlockIndex *chain_start_header,
                               std::vector<CBlockHeader> &headers)
        EXCLUSIVE_LOCKS_REQUIRED(!peer.m_headers_sync_mutex, !m_peer_mutex,
                                 !m_headers_presync_mutex, g_msgproc_mutex);
 
    bool IsAncestorOfBestHeaderOrTip(const CBlockIndex *header)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
    bool MaybeSendGetHeaders(CNode &pfrom, const CBlockLocator &locator,
                             Peer &peer)
        EXCLUSIVE_LOCKS_REQUIRED(g_msgproc_mutex);
    void HeadersDirectFetchBlocks(const Config &config, CNode &pfrom,
                                  const CBlockIndex &last_header);
    void UpdatePeerStateForReceivedHeaders(CNode &pfrom, Peer &peer,
                                           const CBlockIndex &last_header,
                                           bool received_new_header,
                                           bool may_have_more_headers)
        EXCLUSIVE_LOCKS_REQUIRED(g_msgproc_mutex);
 
    void SendBlockTransactions(CNode &pfrom, Peer &peer, const CBlock &block,
                               const BlockTransactionsRequest &req);
 
    void AddTxAnnouncement(const CNode &node, const TxId &txid,
                           std::chrono::microseconds current_time)
        EXCLUSIVE_LOCKS_REQUIRED(::cs_main);
 
    void
    AddProofAnnouncement(const CNode &node, const avalanche::ProofId &proofid,
                         std::chrono::microseconds current_time, bool preferred)
        EXCLUSIVE_LOCKS_REQUIRED(cs_proofrequest);
 
    void PushMessage(CNode &node, CSerializedNetMsg &&msg) const {
        m_connman.PushMessage(&node, std::move(msg));
    }
    template <typename... Args>
    void MakeAndPushMessage(CNode &node, std::string msg_type,
                            Args &&...args) const {
        m_connman.PushMessage(&node, NetMsg::Make(std::move(msg_type),
                                                  std::forward<Args>(args)...));
    }
 
    void PushNodeVersion(const Config &config, CNode &pnode, const Peer &peer);
 
    void MaybeSendPing(CNode &node_to, Peer &peer,
                       std::chrono::microseconds now);
 
    void MaybeSendAddr(CNode &node, Peer &peer,
                       std::chrono::microseconds current_time)
        EXCLUSIVE_LOCKS_REQUIRED(g_msgproc_mutex);
 
    void MaybeSendSendHeaders(CNode &node, Peer &peer)
        EXCLUSIVE_LOCKS_REQUIRED(g_msgproc_mutex);
 
    void MaybeSendFeefilter(CNode &node, Peer &peer,
                            std::chrono::microseconds current_time)
        EXCLUSIVE_LOCKS_REQUIRED(g_msgproc_mutex);
 
    void RelayAddress(NodeId originator, const CAddress &addr, bool fReachable)
        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, g_msgproc_mutex);
 
    FastRandomContext m_rng GUARDED_BY(NetEventsInterface::g_msgproc_mutex);
 
    FeeFilterRounder
        m_fee_filter_rounder GUARDED_BY(NetEventsInterface::g_msgproc_mutex);
 
    const CChainParams &m_chainparams;
    CConnman &m_connman;
    AddrMan &m_addrman;
    BanMan *const m_banman;
    ChainstateManager &m_chainman;
    CTxMemPool &m_mempool;
    avalanche::Processor *const m_avalanche;
    InvRequestTracker<TxId> m_txrequest GUARDED_BY(::cs_main);
 
    Mutex cs_proofrequest;
    InvRequestTracker<avalanche::ProofId>
        m_proofrequest GUARDED_BY(cs_proofrequest);
 
    std::atomic<int> m_best_height{-1};
 
    std::chrono::seconds m_stale_tip_check_time GUARDED_BY(cs_main){0s};
 
    const Options m_opts;
 
    bool RejectIncomingTxs(const CNode &peer) const;
 
    bool m_initial_sync_finished GUARDED_BY(cs_main){false};
 
    mutable Mutex m_peer_mutex;
    std::map<NodeId, PeerRef> m_peer_map GUARDED_BY(m_peer_mutex);
 
    std::map<NodeId, CNodeState> m_node_states GUARDED_BY(cs_main);
 
    const CNodeState *State(NodeId pnode) const
        EXCLUSIVE_LOCKS_REQUIRED(cs_main);
    CNodeState *State(NodeId pnode) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
    std::atomic<std::chrono::microseconds> m_next_inv_to_inbounds{0us};
 
    int nSyncStarted GUARDED_BY(cs_main) = 0;
 
    BlockHash
        m_last_block_inv_triggering_headers_sync GUARDED_BY(g_msgproc_mutex){};
 
    std::map<BlockHash, std::pair<NodeId, bool>>
        mapBlockSource GUARDED_BY(cs_main);
 
    int m_outbound_peers_with_protect_from_disconnect GUARDED_BY(cs_main) = 0;
 
    int m_num_preferred_download_peers GUARDED_BY(cs_main){0};
 
    std::atomic<std::chrono::seconds> m_block_stalling_timeout{
        BLOCK_STALLING_TIMEOUT_DEFAULT};
 
    bool AlreadyHaveTx(const TxId &txid, bool include_reconsiderable)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main,
                                 !m_recent_confirmed_transactions_mutex);
 
    CRollingBloomFilter m_recent_rejects GUARDED_BY(::cs_main){120'000,
                                                               0.000'001};
 
    BlockHash hashRecentRejectsChainTip GUARDED_BY(cs_main);
 
    CRollingBloomFilter m_recent_rejects_package_reconsiderable
        GUARDED_BY(::cs_main){120'000, 0.000'001};
 
    mutable Mutex m_recent_confirmed_transactions_mutex;
    CRollingBloomFilter m_recent_confirmed_transactions
        GUARDED_BY(m_recent_confirmed_transactions_mutex){24'000, 0.000'001};
 
    std::chrono::microseconds
    NextInvToInbounds(std::chrono::microseconds now,
                      std::chrono::seconds average_interval)
        EXCLUSIVE_LOCKS_REQUIRED(g_msgproc_mutex);
 
    // All of the following cache a recent block, and are protected by
    // m_most_recent_block_mutex
    mutable Mutex m_most_recent_block_mutex;
    std::shared_ptr<const CBlock>
        m_most_recent_block GUARDED_BY(m_most_recent_block_mutex);
    std::shared_ptr<const CBlockHeaderAndShortTxIDs>
        m_most_recent_compact_block GUARDED_BY(m_most_recent_block_mutex);
    BlockHash m_most_recent_block_hash GUARDED_BY(m_most_recent_block_mutex);
    std::unique_ptr<const std::map<TxId, CTransactionRef>>
        m_most_recent_block_txs GUARDED_BY(m_most_recent_block_mutex);
 
    // Data about the low-work headers synchronization, aggregated from all
    // peers' HeadersSyncStates.
    Mutex m_headers_presync_mutex;
    using HeadersPresyncStats =
        std::pair<arith_uint256, std::optional<std::pair<int64_t, uint32_t>>>;
    std::map<NodeId, HeadersPresyncStats>
        m_headers_presync_stats GUARDED_BY(m_headers_presync_mutex){};
    NodeId m_headers_presync_bestpeer GUARDED_BY(m_headers_presync_mutex){-1};
    std::atomic_bool m_headers_presync_should_signal{false};
 
    int m_highest_fast_announce GUARDED_BY(::cs_main){0};
 
    bool IsBlockRequested(const BlockHash &hash)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
    bool IsBlockRequestedFromOutbound(const BlockHash &hash)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
    void RemoveBlockRequest(const BlockHash &hash,
                            std::optional<NodeId> from_peer)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
    bool BlockRequested(const Config &config, NodeId nodeid,
                        const CBlockIndex &block,
                        std::list<QueuedBlock>::iterator **pit = nullptr)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
    bool TipMayBeStale() EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
    void FindNextBlocksToDownload(const Peer &peer, unsigned int count,
                                  std::vector<const CBlockIndex *> &vBlocks,
                                  NodeId &nodeStaller)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
    void TryDownloadingHistoricalBlocks(
        const Peer &peer, unsigned int count,
        std::vector<const CBlockIndex *> &vBlocks, const CBlockIndex *from_tip,
        const CBlockIndex *target_block) EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
    void FindNextBlocks(std::vector<const CBlockIndex *> &vBlocks,
                        const Peer &peer, CNodeState *state,
                        const CBlockIndex *pindexWalk, unsigned int count,
                        int nWindowEnd, const CChain *activeChain = nullptr,
                        NodeId *nodeStaller = nullptr)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
    typedef std::multimap<BlockHash,
                          std::pair<NodeId, std::list<QueuedBlock>::iterator>>
        BlockDownloadMap;
    BlockDownloadMap mapBlocksInFlight GUARDED_BY(cs_main);
 
    std::atomic<std::chrono::seconds> m_last_tip_update{0s};
 
    CTransactionRef FindTxForGetData(const Peer &peer, const TxId &txid,
                                     const std::chrono::seconds mempool_req,
                                     const std::chrono::seconds now)
        LOCKS_EXCLUDED(cs_main)
            EXCLUSIVE_LOCKS_REQUIRED(!m_most_recent_block_mutex,
                                     NetEventsInterface::g_msgproc_mutex);
 
    void ProcessGetData(const Config &config, CNode &pfrom, Peer &peer,
                        const std::atomic<bool> &interruptMsgProc)
        EXCLUSIVE_LOCKS_REQUIRED(!m_most_recent_block_mutex,
                                 peer.m_getdata_requests_mutex,
                                 NetEventsInterface::g_msgproc_mutex)
            LOCKS_EXCLUDED(cs_main);
 
    void ProcessBlock(const Config &config, CNode &node,
                      const std::shared_ptr<const CBlock> &block,
                      bool force_processing, bool min_pow_checked);
 
    void MaybeSetPeerAsAnnouncingHeaderAndIDs(NodeId nodeid)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
    std::list<NodeId> lNodesAnnouncingHeaderAndIDs GUARDED_BY(cs_main);
 
    int m_peers_downloading_from GUARDED_BY(cs_main) = 0;
 
    void AddToCompactExtraTransactions(const CTransactionRef &tx)
        EXCLUSIVE_LOCKS_REQUIRED(g_msgproc_mutex);
 
    std::vector<CTransactionRef>
        vExtraTxnForCompact GUARDED_BY(g_msgproc_mutex);
    size_t vExtraTxnForCompactIt GUARDED_BY(g_msgproc_mutex) = 0;
 
    void ProcessBlockAvailability(NodeId nodeid)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main);
    void UpdateBlockAvailability(NodeId nodeid, const BlockHash &hash)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main);
    bool CanDirectFetch() EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
    bool BlockRequestAllowed(const CBlockIndex *pindex)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main);
    bool AlreadyHaveBlock(const BlockHash &block_hash)
        EXCLUSIVE_LOCKS_REQUIRED(cs_main);
    bool AlreadyHaveProof(const avalanche::ProofId &proofid);
    void ProcessGetBlockData(const Config &config, CNode &pfrom, Peer &peer,
                             const CInv &inv)
        EXCLUSIVE_LOCKS_REQUIRED(!m_most_recent_block_mutex);
 
    bool PrepareBlockFilterRequest(CNode &node, Peer &peer,
                                   BlockFilterType filter_type,
                                   uint32_t start_height,
                                   const BlockHash &stop_hash,
                                   uint32_t max_height_diff,
                                   const CBlockIndex *&stop_index,
                                   BlockFilterIndex *&filter_index);
 
    void ProcessGetCFilters(CNode &node, Peer &peer, DataStream &vRecv);
    void ProcessGetCFHeaders(CNode &node, Peer &peer, DataStream &vRecv);
 
    void ProcessGetCFCheckPt(CNode &node, Peer &peer, DataStream &vRecv);
 
    uint32_t GetAvalancheVoteForBlock(const BlockHash &hash) const
        EXCLUSIVE_LOCKS_REQUIRED(cs_main);
 
    uint32_t GetAvalancheVoteForTx(const avalanche::Processor &avalanche,
                                   const TxId &id) const
        EXCLUSIVE_LOCKS_REQUIRED(!m_mempool.cs,
                                 !m_recent_confirmed_transactions_mutex);
 
    bool SetupAddressRelay(const CNode &node, Peer &peer)
        EXCLUSIVE_LOCKS_REQUIRED(g_msgproc_mutex);
 
    void AddAddressKnown(Peer &peer, const CAddress &addr)
        EXCLUSIVE_LOCKS_REQUIRED(g_msgproc_mutex);
    void PushAddress(Peer &peer, const CAddress &addr)
        EXCLUSIVE_LOCKS_REQUIRED(g_msgproc_mutex);
 
    bool ReceivedAvalancheProof(CNode &node, Peer &peer,
                                const avalanche::ProofRef &proof)
        EXCLUSIVE_LOCKS_REQUIRED(!m_peer_mutex, !cs_proofrequest);
 
    avalanche::ProofRef FindProofForGetData(const Peer &peer,
                                            const avalanche::ProofId &proofid,
                                            const std::chrono::seconds now)
        EXCLUSIVE_LOCKS_REQUIRED(NetEventsInterface::g_msgproc_mutex);
 
    bool isPreferredDownloadPeer(const CNode &pfrom);
};
 
const CNodeState *PeerManagerImpl::State(NodeId pnode) const
    EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
    std::map<NodeId, CNodeState>::const_iterator it = m_node_states.find(pnode);
    if (it == m_node_states.end()) {
        return nullptr;
    }
 
    return &it->second;
}
 
CNodeState *PeerManagerImpl::State(NodeId pnode)
    EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
    return const_cast<CNodeState *>(std::as_const(*this).State(pnode));
}
 
static bool IsAddrCompatible(const Peer &peer, const CAddress &addr) {
    return peer.m_wants_addrv2 || addr.IsAddrV1Compatible();
}
 
void PeerManagerImpl::AddAddressKnown(Peer &peer, const CAddress &addr) {
    assert(peer.m_addr_known);
    peer.m_addr_known->insert(addr.GetKey());
}
 
void PeerManagerImpl::PushAddress(Peer &peer, const CAddress &addr) {
    // Known checking here is only to save space from duplicates.
    // Before sending, we'll filter it again for known addresses that were
    // added after addresses were pushed.
    assert(peer.m_addr_known);
    if (addr.IsValid() && !peer.m_addr_known->contains(addr.GetKey()) &&
        IsAddrCompatible(peer, addr)) {
        if (peer.m_addrs_to_send.size() >= m_opts.max_addr_to_send) {
            peer.m_addrs_to_send[m_rng.randrange(peer.m_addrs_to_send.size())] =
                addr;
        } else {
            peer.m_addrs_to_send.push_back(addr);
        }
    }
}
 
static void AddKnownTx(Peer &peer, const TxId &txid) {
    auto tx_relay = peer.GetTxRelay();
    if (!tx_relay) {
        return;
    }
 
    LOCK(tx_relay->m_tx_inventory_mutex);
    tx_relay->m_tx_inventory_known_filter.insert(txid);
}
 
static void AddKnownProof(Peer &peer, const avalanche::ProofId &proofid) {
    if (peer.m_proof_relay != nullptr) {
        LOCK(peer.m_proof_relay->m_proof_inventory_mutex);
        peer.m_proof_relay->m_proof_inventory_known_filter.insert(proofid);
    }
}
 
bool PeerManagerImpl::isPreferredDownloadPeer(const CNode &pfrom) {
    LOCK(cs_main);
    const CNodeState *state = State(pfrom.GetId());
    return state && state->fPreferredDownload;
}
static bool CanServeBlocks(const Peer &peer) {
    return peer.m_their_services & (NODE_NETWORK | NODE_NETWORK_LIMITED);
}
 
static bool IsLimitedPeer(const Peer &peer) {
    return (!(peer.m_their_services & NODE_NETWORK) &&
            (peer.m_their_services & NODE_NETWORK_LIMITED));
}
 
std::chrono::microseconds
PeerManagerImpl::NextInvToInbounds(std::chrono::microseconds now,
                                   std::chrono::seconds average_interval) {
    if (m_next_inv_to_inbounds.load() < now) {
        // If this function were called from multiple threads simultaneously
        // it would possible that both update the next send variable, and return
        // a different result to their caller. This is not possible in practice
        // as only the net processing thread invokes this function.
        m_next_inv_to_inbounds =
            now + m_rng.rand_exp_duration(average_interval);
    }
    return m_next_inv_to_inbounds;
}
 
bool PeerManagerImpl::IsBlockRequested(const BlockHash &hash) {
    return mapBlocksInFlight.count(hash);
}
 
bool PeerManagerImpl::IsBlockRequestedFromOutbound(const BlockHash &hash) {
    for (auto range = mapBlocksInFlight.equal_range(hash);
         range.first != range.second; range.first++) {
        auto [nodeid, block_it] = range.first->second;
        CNodeState &nodestate = *Assert(State(nodeid));
        if (!nodestate.m_is_inbound) {
            return true;
        }
    }
 
    return false;
}
 
void PeerManagerImpl::RemoveBlockRequest(const BlockHash &hash,
                                         std::optional<NodeId> from_peer) {
    auto range = mapBlocksInFlight.equal_range(hash);
    if (range.first == range.second) {
        // Block was not requested from any peer
        return;
    }
 
    // We should not have requested too many of this block
    Assume(mapBlocksInFlight.count(hash) <= MAX_CMPCTBLOCKS_INFLIGHT_PER_BLOCK);
 
    while (range.first != range.second) {
        auto [node_id, list_it] = range.first->second;
 
        if (from_peer && *from_peer != node_id) {
            range.first++;
            continue;
        }
 
        CNodeState &state = *Assert(State(node_id));
 
        if (state.vBlocksInFlight.begin() == list_it) {
            // First block on the queue was received, update the start download
            // time for the next one
            state.m_downloading_since =
                std::max(state.m_downloading_since,
                         GetTime<std::chrono::microseconds>());
        }
        state.vBlocksInFlight.erase(list_it);
 
        if (state.vBlocksInFlight.empty()) {
            // Last validated block on the queue for this peer was received.
            m_peers_downloading_from--;
        }
        state.m_stalling_since = 0us;
 
        range.first = mapBlocksInFlight.erase(range.first);
    }
}
 
bool PeerManagerImpl::BlockRequested(const Config &config, NodeId nodeid,
                                     const CBlockIndex &block,
                                     std::list<QueuedBlock>::iterator **pit) {
    const BlockHash &hash{block.GetBlockHash()};
 
    CNodeState *state = State(nodeid);
    assert(state != nullptr);
 
    Assume(mapBlocksInFlight.count(hash) <= MAX_CMPCTBLOCKS_INFLIGHT_PER_BLOCK);
 
    // Short-circuit most stuff in case it is from the same node
    for (auto range = mapBlocksInFlight.equal_range(hash);
         range.first != range.second; range.first++) {
        if (range.first->second.first == nodeid) {
            if (pit) {
                *pit = &range.first->second.second;
            }
            return false;
        }
    }
 
    // Make sure it's not being fetched already from same peer.
    RemoveBlockRequest(hash, nodeid);
 
    std::list<QueuedBlock>::iterator it = state->vBlocksInFlight.insert(
        state->vBlocksInFlight.end(),
        {&block, std::unique_ptr<PartiallyDownloadedBlock>(
                     pit ? new PartiallyDownloadedBlock(config, &m_mempool)
                         : nullptr)});
    if (state->vBlocksInFlight.size() == 1) {
        // We're starting a block download (batch) from this peer.
        state->m_downloading_since = GetTime<std::chrono::microseconds>();
        m_peers_downloading_from++;
    }
 
    auto itInFlight = mapBlocksInFlight.insert(
        std::make_pair(hash, std::make_pair(nodeid, it)));
 
    if (pit) {
        *pit = &itInFlight->second.second;
    }
 
    return true;
}
 
void PeerManagerImpl::MaybeSetPeerAsAnnouncingHeaderAndIDs(NodeId nodeid) {
    AssertLockHeld(cs_main);
 
    // When in -blocksonly mode, never request high-bandwidth mode from peers.
    // Our mempool will not contain the transactions necessary to reconstruct
    // the compact block.
    if (m_opts.ignore_incoming_txs) {
        return;
    }
 
    CNodeState *nodestate = State(nodeid);
    if (!nodestate) {
        LogPrint(BCLog::NET, "node state unavailable: peer=%d\n", nodeid);
        return;
    }
    if (!nodestate->m_provides_cmpctblocks) {
        return;
    }
    int num_outbound_hb_peers = 0;
    for (std::list<NodeId>::iterator it = lNodesAnnouncingHeaderAndIDs.begin();
         it != lNodesAnnouncingHeaderAndIDs.end(); it++) {
        if (*it == nodeid) {
            lNodesAnnouncingHeaderAndIDs.erase(it);
            lNodesAnnouncingHeaderAndIDs.push_back(nodeid);
            return;
        }
        CNodeState *state = State(*it);
        if (state != nullptr && !state->m_is_inbound) {
            ++num_outbound_hb_peers;
        }
    }
    if (nodestate->m_is_inbound) {
        // If we're adding an inbound HB peer, make sure we're not removing
        // our last outbound HB peer in the process.
        if (lNodesAnnouncingHeaderAndIDs.size() >= 3 &&
            num_outbound_hb_peers == 1) {
            CNodeState *remove_node =
                State(lNodesAnnouncingHeaderAndIDs.front());
            if (remove_node != nullptr && !remove_node->m_is_inbound) {
                // Put the HB outbound peer in the second slot, so that it
                // doesn't get removed.
                std::swap(lNodesAnnouncingHeaderAndIDs.front(),
                          *std::next(lNodesAnnouncingHeaderAndIDs.begin()));
            }
        }
    }
    m_connman.ForNode(nodeid, [this](CNode *pfrom) EXCLUSIVE_LOCKS_REQUIRED(
                                  ::cs_main) {
        AssertLockHeld(::cs_main);
        if (lNodesAnnouncingHeaderAndIDs.size() >= 3) {
            // As per BIP152, we only get 3 of our peers to announce
            // blocks using compact encodings.
            m_connman.ForNode(
                lNodesAnnouncingHeaderAndIDs.front(), [this](CNode *pnodeStop) {
                    MakeAndPushMessage(*pnodeStop, NetMsgType::SENDCMPCT,
                                       /*high_bandwidth=*/false,
                                       /*version=*/CMPCTBLOCKS_VERSION);
                    // save BIP152 bandwidth state: we select peer to be
                    // low-bandwidth
                    pnodeStop->m_bip152_highbandwidth_to = false;
                    return true;
                });
            lNodesAnnouncingHeaderAndIDs.pop_front();
        }
        MakeAndPushMessage(*pfrom, NetMsgType::SENDCMPCT,
                           /*high_bandwidth=*/true,
                           /*version=*/CMPCTBLOCKS_VERSION);
        // save BIP152 bandwidth state: we select peer to be high-bandwidth
        pfrom->m_bip152_highbandwidth_to = true;
        lNodesAnnouncingHeaderAndIDs.push_back(pfrom->GetId());
        return true;
    });
}
 
bool PeerManagerImpl::TipMayBeStale() {
    AssertLockHeld(cs_main);
    const Consensus::Params &consensusParams = m_chainparams.GetConsensus();
    if (m_last_tip_update.load() == 0s) {
        m_last_tip_update = GetTime<std::chrono::seconds>();
    }
    return m_last_tip_update.load() <
               GetTime<std::chrono::seconds>() -
                   std::chrono::seconds{consensusParams.nPowTargetSpacing *
                                        3} &&
           mapBlocksInFlight.empty();
}
 
bool PeerManagerImpl::CanDirectFetch() {
    return m_chainman.ActiveChain().Tip()->Time() >
           GetAdjustedTime() -
               m_chainparams.GetConsensus().PowTargetSpacing() * 20;
}
 
static bool PeerHasHeader(CNodeState *state, const CBlockIndex *pindex)
    EXCLUSIVE_LOCKS_REQUIRED(cs_main) {
    if (state->pindexBestKnownBlock &&
        pindex == state->pindexBestKnownBlock->GetAncestor(pindex->nHeight)) {
        return true;
    }
    if (state->pindexBestHeaderSent &&
        pindex == state->pindexBestHeaderSent->GetAncestor(pindex->nHeight)) {
        return true;
    }
    return false;
}
 
void PeerManagerImpl::ProcessBlockAvailability(NodeId nodeid) {
    CNodeState *state = State(nodeid);
    assert(state != nullptr);
 
    if (!state->hashLastUnknownBlock.IsNull()) {
        const CBlockIndex *pindex =
            m_chainman.m_blockman.LookupBlockIndex(state->hashLastUnknownBlock);
        if (pindex && pindex->nChainWork > 0) {
            if (state->pindexBestKnownBlock == nullptr ||
                pindex->nChainWork >= state->pindexBestKnownBlock->nChainWork) {
                state->pindexBestKnownBlock = pindex;
            }
            state->hashLastUnknownBlock.SetNull();
        }
    }
}
 
void PeerManagerImpl::UpdateBlockAvailability(NodeId nodeid,
                                              const BlockHash &hash) {
    CNodeState *state = State(nodeid);
    assert(state != nullptr);
 
    ProcessBlockAvailability(nodeid);
 
    const CBlockIndex *pindex = m_chainman.m_blockman.LookupBlockIndex(hash);
    if (pindex && pindex->nChainWork > 0) {
        // An actually better block was announced.
        if (state->pindexBestKnownBlock == nullptr ||
            pindex->nChainWork >= state->pindexBestKnownBlock->nChainWork) {
            state->pindexBestKnownBlock = pindex;
        }
    } else {
        // An unknown block was announced; just assume that the latest one is
        // the best one.
        state->hashLastUnknownBlock = hash;
    }
}
 
// Logic for calculating which blocks to download from a given peer, given
// our current tip.
void PeerManagerImpl::FindNextBlocksToDownload(
    const Peer &peer, unsigned int count,
    std::vector<const CBlockIndex *> &vBlocks, NodeId &nodeStaller) {
    if (count == 0) {
        return;
    }
 
    vBlocks.reserve(vBlocks.size() + count);
    CNodeState *state = State(peer.m_id);
    assert(state != nullptr);
 
    // Make sure pindexBestKnownBlock is up to date, we'll need it.
    ProcessBlockAvailability(peer.m_id);
 
    if (state->pindexBestKnownBlock == nullptr ||
        state->pindexBestKnownBlock->nChainWork <
            m_chainman.ActiveChain().Tip()->nChainWork ||
        state->pindexBestKnownBlock->nChainWork <
            m_chainman.MinimumChainWork()) {
        // This peer has nothing interesting.
        return;
    }
 
    // When we sync with AssumeUtxo and discover the snapshot is not in the
    // peer's best chain, abort: We can't reorg to this chain due to missing
    // undo data until the background sync has finished, so downloading blocks
    // from it would be futile.
    const CBlockIndex *snap_base{m_chainman.GetSnapshotBaseBlock()};
    if (snap_base && state->pindexBestKnownBlock->GetAncestor(
                         snap_base->nHeight) != snap_base) {
        LogDebug(BCLog::NET,
                 "Not downloading blocks from peer=%d, which doesn't have the "
                 "snapshot block in its best chain.\n",
                 peer.m_id);
        return;
    }
 
    // Bootstrap quickly by guessing a parent of our best tip is the forking
    // point. Guessing wrong in either direction is not a problem. Also reset
    // pindexLastCommonBlock after a snapshot was loaded, so that blocks after
    // the snapshot will be prioritised for download.
    if (state->pindexLastCommonBlock == nullptr ||
        (snap_base &&
         state->pindexLastCommonBlock->nHeight < snap_base->nHeight)) {
        state->pindexLastCommonBlock =
            m_chainman
                .ActiveChain()[std::min(state->pindexBestKnownBlock->nHeight,
                                        m_chainman.ActiveChain().Height())];
    }
 
    // If the peer reorganized, our previous pindexLastCommonBlock may not be an
    // ancestor of its current tip anymore. Go back enough to fix that.
    state->pindexLastCommonBlock = LastCommonAncestor(
        state->pindexLastCommonBlock, state->pindexBestKnownBlock);
    if (state->pindexLastCommonBlock == state->pindexBestKnownBlock) {
        return;
    }
 
    const CBlockIndex *pindexWalk = state->pindexLastCommonBlock;
    // Never fetch further than the best block we know the peer has, or more
    // than BLOCK_DOWNLOAD_WINDOW + 1 beyond the last linked block we have in
    // common with this peer. The +1 is so we can detect stalling, namely if we
    // would be able to download that next block if the window were 1 larger.
    int nWindowEnd =
        state->pindexLastCommonBlock->nHeight + BLOCK_DOWNLOAD_WINDOW;
 
    FindNextBlocks(vBlocks, peer, state, pindexWalk, count, nWindowEnd,
                   &m_chainman.ActiveChain(), &nodeStaller);
}
 
void PeerManagerImpl::TryDownloadingHistoricalBlocks(
    const Peer &peer, unsigned int count,
    std::vector<const CBlockIndex *> &vBlocks, const CBlockIndex *from_tip,
    const CBlockIndex *target_block) {
    Assert(from_tip);
    Assert(target_block);
 
    if (vBlocks.size() >= count) {
        return;
    }
 
    vBlocks.reserve(count);
    CNodeState *state = Assert(State(peer.m_id));
 
    if (state->pindexBestKnownBlock == nullptr ||
        state->pindexBestKnownBlock->GetAncestor(target_block->nHeight) !=
            target_block) {
        // This peer can't provide us the complete series of blocks leading up
        // to the assumeutxo snapshot base.
        //
        // Presumably this peer's chain has less work than our ActiveChain()'s
        // tip, or else we will eventually crash when we try to reorg to it. Let
        // other logic deal with whether we disconnect this peer.
        //
        // TODO at some point in the future, we might choose to request what
        // blocks this peer does have from the historical chain, despite it not
        // having a complete history beneath the snapshot base.
        return;
    }
 
    FindNextBlocks(vBlocks, peer, state, from_tip, count,
                   std::min<int>(from_tip->nHeight + BLOCK_DOWNLOAD_WINDOW,
                                 target_block->nHeight));
}
 
void PeerManagerImpl::FindNextBlocks(std::vector<const CBlockIndex *> &vBlocks,
                                     const Peer &peer, CNodeState *state,
                                     const CBlockIndex *pindexWalk,
                                     unsigned int count, int nWindowEnd,
                                     const CChain *activeChain,
                                     NodeId *nodeStaller) {
    std::vector<const CBlockIndex *> vToFetch;
    int nMaxHeight =
        std::min<int>(state->pindexBestKnownBlock->nHeight, nWindowEnd + 1);
    NodeId waitingfor = -1;
    while (pindexWalk->nHeight < nMaxHeight) {
        // Read up to 128 (or more, if more blocks than that are needed)
        // successors of pindexWalk (towards pindexBestKnownBlock) into
        // vToFetch. We fetch 128, because CBlockIndex::GetAncestor may be as
        // expensive as iterating over ~100 CBlockIndex* entries anyway.
        int nToFetch = std::min(nMaxHeight - pindexWalk->nHeight,
                                std::max<int>(count - vBlocks.size(), 128));
        vToFetch.resize(nToFetch);
        pindexWalk = state->pindexBestKnownBlock->GetAncestor(
            pindexWalk->nHeight + nToFetch);
        vToFetch[nToFetch - 1] = pindexWalk;
        for (unsigned int i = nToFetch - 1; i > 0; i--) {
            vToFetch[i - 1] = vToFetch[i]->pprev;
        }
 
        // Iterate over those blocks in vToFetch (in forward direction), adding
        // the ones that are not yet downloaded and not in flight to vBlocks. In
        // the meantime, update pindexLastCommonBlock as long as all ancestors
        // are already downloaded, or if it's already part of our chain (and
        // therefore don't need it even if pruned).
        for (const CBlockIndex *pindex : vToFetch) {
            if (!pindex->IsValid(BlockValidity::TREE)) {
                // We consider the chain that this peer is on invalid.
                return;
            }
            if (pindex->nStatus.hasData() ||
                (activeChain && activeChain->Contains(pindex))) {
                if (activeChain && pindex->HaveNumChainTxs()) {
                    state->pindexLastCommonBlock = pindex;
                }
            } else if (!IsBlockRequested(pindex->GetBlockHash())) {
                // The block is not already downloaded, and not yet in flight.
                if (pindex->nHeight > nWindowEnd) {
                    // We reached the end of the window.
                    if (vBlocks.size() == 0 && waitingfor != peer.m_id) {
                        // We aren't able to fetch anything, but we would be if
                        // the download window was one larger.
                        if (nodeStaller) {
                            *nodeStaller = waitingfor;
                        }
                    }
                    return;
                }
                vBlocks.push_back(pindex);
                if (vBlocks.size() == count) {
                    return;
                }
            } else if (waitingfor == -1) {
                // This is the first already-in-flight block.
                waitingfor =
                    mapBlocksInFlight.lower_bound(pindex->GetBlockHash())
                        ->second.first;
            }
        }
    }
}
 
} // namespace
 
template <class InvId>
static bool TooManyAnnouncements(const CNode &node,
                                 const InvRequestTracker<InvId> &requestTracker,
                                 const DataRequestParameters &requestParams) {
    return !node.HasPermission(
               requestParams.bypass_request_limits_permissions) &&
           requestTracker.Count(node.GetId()) >=
               requestParams.max_peer_announcements;
}
 
template <class InvId>
static std::chrono::microseconds
ComputeRequestTime(const CNode &node,
                   const InvRequestTracker<InvId> &requestTracker,
                   const DataRequestParameters &requestParams,
                   std::chrono::microseconds current_time, bool preferred) {
    auto delay = std::chrono::microseconds{0};
 
    if (!preferred) {
        delay += requestParams.nonpref_peer_delay;
    }
 
    if (!node.HasPermission(requestParams.bypass_request_limits_permissions) &&
        requestTracker.CountInFlight(node.GetId()) >=
            requestParams.max_peer_request_in_flight) {
        delay += requestParams.overloaded_peer_delay;
    }
 
    return current_time + delay;
}
 
void PeerManagerImpl::PushNodeVersion(const Config &config, CNode &pnode,
                                      const Peer &peer) {
    uint64_t my_services{peer.m_our_services};
    const int64_t nTime{count_seconds(GetTime<std::chrono::seconds>())};
    uint64_t nonce = pnode.GetLocalNonce();
    const int nNodeStartingHeight{m_best_height};
    NodeId nodeid = pnode.GetId();
    CAddress addr = pnode.addr;
    uint64_t extraEntropy = pnode.GetLocalExtraEntropy();
 
    CService addr_you =
        addr.IsRoutable() && !IsProxy(addr) && addr.IsAddrV1Compatible()
            ? addr
            : CService();
    uint64_t your_services{addr.nServices};
 
    const bool tx_relay{!RejectIncomingTxs(pnode)};
    MakeAndPushMessage(
        // your_services, addr_you: Together the pre-version-31402 serialization
        //     of CAddress "addrYou" (without nTime)
        // my_services, CService(): Together the pre-version-31402 serialization
        //     of CAddress "addrMe" (without nTime)
        pnode, NetMsgType::VERSION, PROTOCOL_VERSION, my_services, nTime,
        your_services, WithParams(CNetAddr::V1, addr_you), my_services,
        WithParams(CNetAddr::V1, CService{}), nonce, userAgent(config),
        nNodeStartingHeight, tx_relay, extraEntropy);
 
    if (fLogIPs) {
        LogPrint(BCLog::NET,
                 "send version message: version %d, blocks=%d, them=%s, "
                 "txrelay=%d, peer=%d\n",
                 PROTOCOL_VERSION, nNodeStartingHeight,
                 addr_you.ToStringAddrPort(), tx_relay, nodeid);
    } else {
        LogPrint(BCLog::NET,
                 "send version message: version %d, blocks=%d, "
                 "txrelay=%d, peer=%d\n",
                 PROTOCOL_VERSION, nNodeStartingHeight, tx_relay, nodeid);
    }
}
 
void PeerManagerImpl::AddTxAnnouncement(
    const CNode &node, const TxId &txid,
    std::chrono::microseconds current_time) {
    // For m_txrequest and state
    AssertLockHeld(::cs_main);
 
    if (TooManyAnnouncements(node, m_txrequest, TX_REQUEST_PARAMS)) {
        return;
    }
 
    const bool preferred = isPreferredDownloadPeer(node);
    auto reqtime = ComputeRequestTime(node, m_txrequest, TX_REQUEST_PARAMS,
                                      current_time, preferred);
 
    m_txrequest.ReceivedInv(node.GetId(), txid, preferred, reqtime);
}
 
void PeerManagerImpl::AddProofAnnouncement(
    const CNode &node, const avalanche::ProofId &proofid,
    std::chrono::microseconds current_time, bool preferred) {
    // For m_proofrequest
    AssertLockHeld(cs_proofrequest);
 
    if (TooManyAnnouncements(node, m_proofrequest, PROOF_REQUEST_PARAMS)) {
        return;
    }
 
    auto reqtime = ComputeRequestTime(
        node, m_proofrequest, PROOF_REQUEST_PARAMS, current_time, preferred);
 
    m_proofrequest.ReceivedInv(node.GetId(), proofid, preferred, reqtime);
}
 
void PeerManagerImpl::UpdateLastBlockAnnounceTime(NodeId node,
                                                  int64_t time_in_seconds) {
    LOCK(cs_main);
    CNodeState *state = State(node);
    if (state) {
        state->m_last_block_announcement = time_in_seconds;
    }
}
 
void PeerManagerImpl::InitializeNode(const Config &config, CNode &node,
                                     ServiceFlags our_services) {
    NodeId nodeid = node.GetId();
    {
        LOCK(cs_main);
        m_node_states.emplace_hint(m_node_states.end(),
                                   std::piecewise_construct,
                                   std::forward_as_tuple(nodeid),
                                   std::forward_as_tuple(node.IsInboundConn()));
        assert(m_txrequest.Count(nodeid) == 0);
    }
 
    if (NetPermissions::HasFlag(node.m_permission_flags,
                                NetPermissionFlags::BloomFilter)) {
        our_services = static_cast<ServiceFlags>(our_services | NODE_BLOOM);
    }
 
    PeerRef peer = std::make_shared<Peer>(nodeid, our_services, !!m_avalanche);
    {
        LOCK(m_peer_mutex);
        m_peer_map.emplace_hint(m_peer_map.end(), nodeid, peer);
    }
    if (!node.IsInboundConn()) {
        PushNodeVersion(config, node, *peer);
    }
}
 
void PeerManagerImpl::ReattemptInitialBroadcast(CScheduler &scheduler) {
    std::set<TxId> unbroadcast_txids = m_mempool.GetUnbroadcastTxs();
 
    for (const TxId &txid : unbroadcast_txids) {
        // Sanity check: all unbroadcast txns should exist in the mempool
        if (m_mempool.exists(txid)) {
            RelayTransaction(txid);
        } else {
            m_mempool.RemoveUnbroadcastTx(txid, true);
        }
    }
 
    if (m_avalanche) {
        // Get and sanitize the list of proofids to broadcast. The RelayProof
        // call is done in a second loop to avoid locking cs_vNodes while
        // cs_peerManager is locked which would cause a potential deadlock due
        // to reversed lock order.
        auto unbroadcasted_proofids =
            m_avalanche->withPeerManager([&](avalanche::PeerManager &pm) {
                auto unbroadcasted_proofids = pm.getUnbroadcastProofs();
 
                auto it = unbroadcasted_proofids.begin();
                while (it != unbroadcasted_proofids.end()) {
                    // Sanity check: all unbroadcast proofs should be bound to a
                    // peer in the peermanager
                    if (!pm.isBoundToPeer(*it)) {
                        pm.removeUnbroadcastProof(*it);
                        it = unbroadcasted_proofids.erase(it);
                        continue;
                    }
 
                    ++it;
                }
 
                return unbroadcasted_proofids;
            });
 
        // Remaining proofids are the ones to broadcast
        for (const auto &proofid : unbroadcasted_proofids) {
            RelayProof(proofid);
        }
    }
 
    // Schedule next run for 10-15 minutes in the future.
    // We add randomness on every cycle to avoid the possibility of P2P
    // fingerprinting.
    const auto reattemptBroadcastInterval =
        10min + FastRandomContext().randrange<std::chrono::milliseconds>(5min);
    scheduler.scheduleFromNow([&] { ReattemptInitialBroadcast(scheduler); },
                              reattemptBroadcastInterval);
}
 
void PeerManagerImpl::UpdateAvalancheStatistics() const {
    m_connman.ForEachNode([](CNode *pnode) {
        pnode->updateAvailabilityScore(AVALANCHE_STATISTICS_DECAY_FACTOR);
    });
}
 
void PeerManagerImpl::AvalanchePeriodicNetworking(CScheduler &scheduler) const {
    const auto now = GetTime<std::chrono::seconds>();
    std::vector<NodeId> avanode_ids;
    bool fQuorumEstablished;
    bool fShouldRequestMoreNodes;
 
    if (!m_avalanche) {
        // Not enabled or not ready yet, retry later
        goto scheduleLater;
    }
 
    m_avalanche->sendDelayedAvahello();
 
    fQuorumEstablished = m_avalanche->isQuorumEstablished();
    fShouldRequestMoreNodes =
        m_avalanche->withPeerManager([&](avalanche::PeerManager &pm) {
            return pm.shouldRequestMoreNodes();
        });
 
    m_connman.ForEachNode([&](CNode *pnode) {
        // Build a list of the avalanche peers nodeids
        if (pnode->m_avalanche_enabled) {
            avanode_ids.push_back(pnode->GetId());
        }
 
        PeerRef peer = GetPeerRef(pnode->GetId());
        if (peer == nullptr) {
            return;
        }
        // If a proof radix tree timed out, cleanup
        if (peer->m_proof_relay &&
            now > (peer->m_proof_relay->lastSharedProofsUpdate.load() +
                   AVALANCHE_AVAPROOFS_TIMEOUT)) {
            peer->m_proof_relay->sharedProofs = {};
        }
    });
 
    if (avanode_ids.empty()) {
        // No node is available for messaging, retry later
        goto scheduleLater;
    }
 
    Shuffle(avanode_ids.begin(), avanode_ids.end(), FastRandomContext());
 
    // Request avalanche addresses from our peers
    for (NodeId avanodeId : avanode_ids) {
        const bool sentGetavaaddr =
            m_connman.ForNode(avanodeId, [&](CNode *pavanode) {
                if (!fQuorumEstablished || !pavanode->IsInboundConn()) {
                    MakeAndPushMessage(*pavanode, NetMsgType::GETAVAADDR);
                    PeerRef peer = GetPeerRef(avanodeId);
                    WITH_LOCK(peer->m_addr_token_bucket_mutex,
                              peer->m_addr_token_bucket +=
                              m_opts.max_addr_to_send);
                    return true;
                }
                return false;
            });
 
        // If we have no reason to believe that we need more nodes, only request
        // addresses from one of our peers.
        if (sentGetavaaddr && fQuorumEstablished && !fShouldRequestMoreNodes) {
            break;
        }
    }
 
    if (m_chainman.IsInitialBlockDownload()) {
        // Don't request proofs while in IBD. We're likely to orphan them
        // because we don't have the UTXOs.
        goto scheduleLater;
    }
 
    // If we never had an avaproofs message yet, be kind and only request to a
    // subset of our peers as we expect a ton of avaproofs message in the
    // process.
    if (m_avalanche->getAvaproofsNodeCounter() == 0) {
        avanode_ids.resize(std::min<size_t>(avanode_ids.size(), 3));
    }
 
    for (NodeId nodeid : avanode_ids) {
        // Send a getavaproofs to all of our peers
        m_connman.ForNode(nodeid, [&](CNode *pavanode) {
            PeerRef peer = GetPeerRef(nodeid);
            if (peer->m_proof_relay) {
                MakeAndPushMessage(*pavanode, NetMsgType::GETAVAPROOFS);
                peer->m_proof_relay->compactproofs_requested = true;
            }
            return true;
        });
    }
 
scheduleLater:
    // Schedule next run for 2-5 minutes in the future.
    // We add randomness on every cycle to avoid the possibility of P2P
    // fingerprinting.
    const auto avalanchePeriodicNetworkingInterval =
        2min + FastRandomContext().randrange<std::chrono::milliseconds>(3min);
    scheduler.scheduleFromNow([&] { AvalanchePeriodicNetworking(scheduler); },
                              avalanchePeriodicNetworkingInterval);
}
 
void PeerManagerImpl::FinalizeNode(const Config &config, const CNode &node) {
    NodeId nodeid = node.GetId();
    {
        LOCK(cs_main);
        {
            // We remove the PeerRef from g_peer_map here, but we don't always
            // destruct the Peer. Sometimes another thread is still holding a
            // PeerRef, so the refcount is >= 1. Be careful not to do any
            // processing here that assumes Peer won't be changed before it's
            // destructed.
            PeerRef peer = RemovePeer(nodeid);
            assert(peer != nullptr);
            LOCK(m_peer_mutex);
            m_peer_map.erase(nodeid);
        }
        CNodeState *state = State(nodeid);
        assert(state != nullptr);
 
        if (state->fSyncStarted) {
            nSyncStarted--;
        }
 
        for (const QueuedBlock &entry : state->vBlocksInFlight) {
            auto range =
                mapBlocksInFlight.equal_range(entry.pindex->GetBlockHash());
            while (range.first != range.second) {
                auto [node_id, list_it] = range.first->second;
                if (node_id != nodeid) {
                    range.first++;
                } else {
                    range.first = mapBlocksInFlight.erase(range.first);
                }
            }
        }
        m_mempool.withOrphanage([nodeid](TxOrphanage &orphanage) {
            orphanage.EraseForPeer(nodeid);
        });
        m_txrequest.DisconnectedPeer(nodeid);
        m_num_preferred_download_peers -= state->fPreferredDownload;
        m_peers_downloading_from -= (!state->vBlocksInFlight.empty());
        assert(m_peers_downloading_from >= 0);
        m_outbound_peers_with_protect_from_disconnect -=
            state->m_chain_sync.m_protect;
        assert(m_outbound_peers_with_protect_from_disconnect >= 0);
 
        m_node_states.erase(nodeid);
 
        if (m_node_states.empty()) {
            // Do a consistency check after the last peer is removed.
            assert(mapBlocksInFlight.empty());
            assert(m_num_preferred_download_peers == 0);
            assert(m_peers_downloading_from == 0);
            assert(m_outbound_peers_with_protect_from_disconnect == 0);
            assert(m_txrequest.Size() == 0);
            assert(m_mempool.withOrphanage([](const TxOrphanage &orphanage) {
                return orphanage.Size();
            }) == 0);
        }
    }
 
    if (node.fSuccessfullyConnected && !node.IsBlockOnlyConn() &&
        !node.IsInboundConn()) {
        // Only change visible addrman state for full outbound peers. We don't
        // call Connected() for feeler connections since they don't have
        // fSuccessfullyConnected set.
        m_addrman.Connected(node.addr);
    }
    {
        LOCK(m_headers_presync_mutex);
        m_headers_presync_stats.erase(nodeid);
    }
 
    WITH_LOCK(cs_proofrequest, m_proofrequest.DisconnectedPeer(nodeid));
 
    LogPrint(BCLog::NET, "Cleared nodestate for peer=%d\n", nodeid);
}
 
PeerRef PeerManagerImpl::GetPeerRef(NodeId id) const {
    LOCK(m_peer_mutex);
    auto it = m_peer_map.find(id);
    return it != m_peer_map.end() ? it->second : nullptr;
}
 
PeerRef PeerManagerImpl::RemovePeer(NodeId id) {
    PeerRef ret;
    LOCK(m_peer_mutex);
    auto it = m_peer_map.find(id);
    if (it != m_peer_map.end()) {
        ret = std::move(it->second);
        m_peer_map.erase(it);
    }
    return ret;
}
 
bool PeerManagerImpl::GetNodeStateStats(NodeId nodeid,
                                        CNodeStateStats &stats) const {
    {
        LOCK(cs_main);
        const CNodeState *state = State(nodeid);
        if (state == nullptr) {
            return false;
        }
        stats.nSyncHeight = state->pindexBestKnownBlock
                                ? state->pindexBestKnownBlock->nHeight
                                : -1;
        stats.nCommonHeight = state->pindexLastCommonBlock
                                  ? state->pindexLastCommonBlock->nHeight
                                  : -1;
        for (const QueuedBlock &queue : state->vBlocksInFlight) {
            if (queue.pindex) {
                stats.vHeightInFlight.push_back(queue.pindex->nHeight);
            }
        }
    }
 
    PeerRef peer = GetPeerRef(nodeid);
    if (peer == nullptr) {
        return false;
    }
    stats.their_services = peer->m_their_services;
    stats.m_starting_height = peer->m_starting_height;
    // It is common for nodes with good ping times to suddenly become lagged,
    // due to a new block arriving or other large transfer.
    // Merely reporting pingtime might fool the caller into thinking the node
    // was still responsive, since pingtime does not update until the ping is
    // complete, which might take a while. So, if a ping is taking an unusually
    // long time in flight, the caller can immediately detect that this is
    // happening.
    auto ping_wait{0us};
    if ((0 != peer->m_ping_nonce_sent) &&
        (0 != peer->m_ping_start.load().count())) {
        ping_wait =
            GetTime<std::chrono::microseconds>() - peer->m_ping_start.load();
    }
 
    if (auto tx_relay = peer->GetTxRelay()) {
        stats.m_relay_txs = WITH_LOCK(tx_relay->m_bloom_filter_mutex,
                                      return tx_relay->m_relay_txs);
        stats.m_fee_filter_received = tx_relay->m_fee_filter_received.load();
    } else {
        stats.m_relay_txs = false;
        stats.m_fee_filter_received = Amount::zero();
    }
 
    stats.m_ping_wait = ping_wait;
    stats.m_addr_processed = peer->m_addr_processed.load();
    stats.m_addr_rate_limited = peer->m_addr_rate_limited.load();
    stats.m_addr_relay_enabled = peer->m_addr_relay_enabled.load();
    {
        LOCK(peer->m_headers_sync_mutex);
        if (peer->m_headers_sync) {
            stats.presync_height = peer->m_headers_sync->GetPresyncHeight();
        }
    }
 
    return true;
}
 
void PeerManagerImpl::AddToCompactExtraTransactions(const CTransactionRef &tx) {
    if (m_opts.max_extra_txs <= 0) {
        return;
    }
 
    if (!vExtraTxnForCompact.size()) {
        vExtraTxnForCompact.resize(m_opts.max_extra_txs);
    }
 
    vExtraTxnForCompact[vExtraTxnForCompactIt] = tx;
    vExtraTxnForCompactIt = (vExtraTxnForCompactIt + 1) % m_opts.max_extra_txs;
}
 
void PeerManagerImpl::Misbehaving(Peer &peer, const std::string &message) {
    LOCK(peer.m_misbehavior_mutex);
 
    const std::string message_prefixed =
        message.empty() ? "" : (": " + message);
    peer.m_should_discourage = true;
    LogPrint(BCLog::NET, "Misbehaving: peer=%d%s\n", peer.m_id,
             message_prefixed);
}
 
void PeerManagerImpl::MaybePunishNodeForBlock(NodeId nodeid,
                                              const BlockValidationState &state,
                                              bool via_compact_block,
                                              const std::string &message) {
    PeerRef peer{GetPeerRef(nodeid)};
    switch (state.GetResult()) {
        case BlockValidationResult::BLOCK_RESULT_UNSET:
            break;
        case BlockValidationResult::BLOCK_HEADER_LOW_WORK:
            // We didn't try to process the block because the header chain may
            // have too little work.
            break;
        // The node is providing invalid data:
        case BlockValidationResult::BLOCK_CONSENSUS:
        case BlockValidationResult::BLOCK_MUTATED:
            if (!via_compact_block) {
                if (peer) {
                    Misbehaving(*peer, message);
                }
                return;
            }
            break;
        case BlockValidationResult::BLOCK_CACHED_INVALID: {
            LOCK(cs_main);
            CNodeState *node_state = State(nodeid);
            if (node_state == nullptr) {
                break;
            }
 
            // Ban outbound (but not inbound) peers if on an invalid chain.
            // Exempt HB compact block peers. Manual connections are always
            // protected from discouragement.
            if (!via_compact_block && !node_state->m_is_inbound) {
                if (peer) {
                    Misbehaving(*peer, message);
                }
                return;
            }
            break;
        }
        case BlockValidationResult::BLOCK_INVALID_HEADER:
        case BlockValidationResult::BLOCK_CHECKPOINT:
        case BlockValidationResult::BLOCK_INVALID_PREV:
            if (peer) {
                Misbehaving(*peer, message);
            }
            return;
        // Conflicting (but not necessarily invalid) data or different policy:
        case BlockValidationResult::BLOCK_MISSING_PREV:
            if (peer) {
                Misbehaving(*peer, message);
            }
            return;
        case BlockValidationResult::BLOCK_TIME_FUTURE:
            break;
    }
    if (message != "") {
        LogPrint(BCLog::NET, "peer=%d: %s\n", nodeid, message);
    }
}
 
void PeerManagerImpl::MaybePunishNodeForTx(NodeId nodeid,
                                           const TxValidationState &state,
                                           const std::string &message) {
    PeerRef peer{GetPeerRef(nodeid)};
    switch (state.GetResult()) {
        case TxValidationResult::TX_RESULT_UNSET:
            break;
        // The node is providing invalid data:
        case TxValidationResult::TX_CONSENSUS:
            if (peer) {
                Misbehaving(*peer, message);
            }
            return;
        // Conflicting (but not necessarily invalid) data or different policy:
        case TxValidationResult::TX_INPUTS_NOT_STANDARD:
        case TxValidationResult::TX_NOT_STANDARD:
        case TxValidationResult::TX_MISSING_INPUTS:
        case TxValidationResult::TX_PREMATURE_SPEND:
        case TxValidationResult::TX_DUPLICATE:
        case TxValidationResult::TX_CONFLICT:
        case TxValidationResult::TX_CHILD_BEFORE_PARENT:
        case TxValidationResult::TX_MEMPOOL_POLICY:
        case TxValidationResult::TX_NO_MEMPOOL:
        case TxValidationResult::TX_PACKAGE_RECONSIDERABLE:
        case TxValidationResult::TX_AVALANCHE_RECONSIDERABLE:
        case TxValidationResult::TX_UNKNOWN:
            break;
    }
    if (message != "") {
        LogPrint(BCLog::NET, "peer=%d: %s\n", nodeid, message);
    }
}
 
bool PeerManagerImpl::BlockRequestAllowed(const CBlockIndex *pindex) {
    AssertLockHeld(cs_main);
    if (m_chainman.ActiveChain().Contains(pindex)) {
        return true;
    }
    return pindex->IsValid(BlockValidity::SCRIPTS) &&
           (m_chainman.m_best_header != nullptr) &&
           (m_chainman.m_best_header->GetBlockTime() - pindex->GetBlockTime() <
            STALE_RELAY_AGE_LIMIT) &&
           (GetBlockProofEquivalentTime(
                *m_chainman.m_best_header, *pindex, *m_chainman.m_best_header,
                m_chainparams.GetConsensus()) < STALE_RELAY_AGE_LIMIT);
}
 
std::optional<std::string>
PeerManagerImpl::FetchBlock(const Config &config, NodeId peer_id,
                            const CBlockIndex &block_index) {
    if (m_chainman.m_blockman.LoadingBlocks()) {
        return "Loading blocks ...";
    }
 
    LOCK(cs_main);
 
    // Ensure this peer exists and hasn't been disconnected
    CNodeState *state = State(peer_id);
    if (state == nullptr) {
        return "Peer does not exist";
    }
 
    // Forget about all prior requests
    RemoveBlockRequest(block_index.GetBlockHash(), std::nullopt);
 
    // Mark block as in-flight
    if (!BlockRequested(config, peer_id, block_index)) {
        return "Already requested from this peer";
    }
 
    // Construct message to request the block
    const BlockHash &hash{block_index.GetBlockHash()};
    const std::vector<CInv> invs{CInv(MSG_BLOCK, hash)};
 
    // Send block request message to the peer
    if (!m_connman.ForNode(peer_id, [this, &invs](CNode *node) {
            this->MakeAndPushMessage(*node, NetMsgType::GETDATA, invs);
            return true;
        })) {
        return "Node not fully connected";
    }
 
    LogPrint(BCLog::NET, "Requesting block %s from peer=%d\n", hash.ToString(),
             peer_id);
    return std::nullopt;
}
 
std::unique_ptr<PeerManager>
PeerManager::make(CConnman &connman, AddrMan &addrman, BanMan *banman,
                  ChainstateManager &chainman, CTxMemPool &pool,
                  avalanche::Processor *const avalanche, Options opts) {
    return std::make_unique<PeerManagerImpl>(connman, addrman, banman, chainman,
                                             pool, avalanche, opts);
}
 
PeerManagerImpl::PeerManagerImpl(CConnman &connman, AddrMan &addrman,
                                 BanMan *banman, ChainstateManager &chainman,
                                 CTxMemPool &pool,
                                 avalanche::Processor *const avalanche,
                                 Options opts)
    : m_rng{opts.deterministic_rng},
      m_fee_filter_rounder{CFeeRate{DEFAULT_MIN_RELAY_TX_FEE_PER_KB}, m_rng},
      m_chainparams(chainman.GetParams()), m_connman(connman),
      m_addrman(addrman), m_banman(banman), m_chainman(chainman),
      m_mempool(pool), m_avalanche(avalanche), m_opts{opts} {}
 
void PeerManagerImpl::StartScheduledTasks(CScheduler &scheduler) {
    // Stale tip checking and peer eviction are on two different timers, but we
    // don't want them to get out of sync due to drift in the scheduler, so we
    // combine them in one function and schedule at the quicker (peer-eviction)
    // timer.
    static_assert(
        EXTRA_PEER_CHECK_INTERVAL < STALE_CHECK_INTERVAL,
        "peer eviction timer should be less than stale tip check timer");
    scheduler.scheduleEvery(
        [this]() {
            this->CheckForStaleTipAndEvictPeers();
            return true;
        },
        std::chrono::seconds{EXTRA_PEER_CHECK_INTERVAL});
 
    // schedule next run for 10-15 minutes in the future
    const auto reattemptBroadcastInterval =
        10min + FastRandomContext().randrange<std::chrono::milliseconds>(5min);
    scheduler.scheduleFromNow([&] { ReattemptInitialBroadcast(scheduler); },
                              reattemptBroadcastInterval);
 
    // Update the avalanche statistics on a schedule
    scheduler.scheduleEvery(
        [this]() {
            UpdateAvalancheStatistics();
            return true;
        },
        AVALANCHE_STATISTICS_REFRESH_PERIOD);
 
    // schedule next run for 2-5 minutes in the future
    const auto avalanchePeriodicNetworkingInterval =
        2min + FastRandomContext().randrange<std::chrono::milliseconds>(3min);
    scheduler.scheduleFromNow([&] { AvalanchePeriodicNetworking(scheduler); },
                              avalanchePeriodicNetworkingInterval);
}
 
void PeerManagerImpl::BlockConnected(
    ChainstateRole role, const std::shared_ptr<const CBlock> &pblock,
    const CBlockIndex *pindex) {
    // Update this for all chainstate roles so that we don't mistakenly see
    // peers helping us do background IBD as having a stale tip.
    m_last_tip_update = GetTime<std::chrono::seconds>();
 
    // In case the dynamic timeout was doubled once or more, reduce it slowly
    // back to its default value
    auto stalling_timeout = m_block_stalling_timeout.load();
    Assume(stalling_timeout >= BLOCK_STALLING_TIMEOUT_DEFAULT);
    if (stalling_timeout != BLOCK_STALLING_TIMEOUT_DEFAULT) {
        const auto new_timeout =
            std::max(std::chrono::duration_cast<std::chrono::seconds>(
                         stalling_timeout * 0.85),
                     BLOCK_STALLING_TIMEOUT_DEFAULT);
        if (m_block_stalling_timeout.compare_exchange_strong(stalling_timeout,
                                                             new_timeout)) {
            LogPrint(BCLog::NET, "Decreased stalling timeout to %d seconds\n",
                     count_seconds(new_timeout));
        }
    }
 
    // The following tasks can be skipped since we don't maintain a mempool for
    // the ibd/background chainstate.
    if (role == ChainstateRole::BACKGROUND) {
        return;
    }
    m_mempool.withOrphanage([&pblock](TxOrphanage &orphanage) {
        orphanage.EraseForBlock(*pblock);
    });
    m_mempool.withConflicting([&pblock](TxConflicting &conflicting) {
        conflicting.EraseForBlock(*pblock);
    });
 
    {
        LOCK(m_recent_confirmed_transactions_mutex);
        for (const CTransactionRef &ptx : pblock->vtx) {
            m_recent_confirmed_transactions.insert(ptx->GetId());
        }
    }
    {
        LOCK(cs_main);
        for (const auto &ptx : pblock->vtx) {
            m_txrequest.ForgetInvId(ptx->GetId());
        }
    }
}
 
void PeerManagerImpl::BlockDisconnected(
    const std::shared_ptr<const CBlock> &block, const CBlockIndex *pindex) {
    // To avoid relay problems with transactions that were previously
    // confirmed, clear our filter of recently confirmed transactions whenever
    // there's a reorg.
    // This means that in a 1-block reorg (where 1 block is disconnected and
    // then another block reconnected), our filter will drop to having only one
    // block's worth of transactions in it, but that should be fine, since
    // presumably the most common case of relaying a confirmed transaction
    // should be just after a new block containing it is found.
    LOCK(m_recent_confirmed_transactions_mutex);
    m_recent_confirmed_transactions.reset();
}
 
void PeerManagerImpl::NewPoWValidBlock(
    const CBlockIndex *pindex, const std::shared_ptr<const CBlock> &pblock) {
    std::shared_ptr<const CBlockHeaderAndShortTxIDs> pcmpctblock =
        std::make_shared<const CBlockHeaderAndShortTxIDs>(
            *pblock, FastRandomContext().rand64());
 
    LOCK(cs_main);
 
    if (pindex->nHeight <= m_highest_fast_announce) {
        return;
    }
    m_highest_fast_announce = pindex->nHeight;
 
    BlockHash hashBlock(pblock->GetHash());
    const std::shared_future<CSerializedNetMsg> lazy_ser{
        std::async(std::launch::deferred, [&] {
            return NetMsg::Make(NetMsgType::CMPCTBLOCK, *pcmpctblock);
        })};
 
    {
        auto most_recent_block_txs =
            std::make_unique<std::map<TxId, CTransactionRef>>();
        for (const auto &tx : pblock->vtx) {
            most_recent_block_txs->emplace(tx->GetId(), tx);
        }
 
        LOCK(m_most_recent_block_mutex);
        m_most_recent_block_hash = hashBlock;
        m_most_recent_block = pblock;
        m_most_recent_compact_block = pcmpctblock;
        m_most_recent_block_txs = std::move(most_recent_block_txs);
    }
 
    m_connman.ForEachNode(
        [this, pindex, &lazy_ser, &hashBlock](CNode *pnode)
            EXCLUSIVE_LOCKS_REQUIRED(::cs_main) {
                AssertLockHeld(::cs_main);
 
                if (pnode->GetCommonVersion() < INVALID_CB_NO_BAN_VERSION ||
                    pnode->fDisconnect) {
                    return;
                }
                ProcessBlockAvailability(pnode->GetId());
                CNodeState &state = *State(pnode->GetId());
                // If the peer has, or we announced to them the previous block
                // already, but we don't think they have this one, go ahead and
                // announce it.
                if (state.m_requested_hb_cmpctblocks &&
                    !PeerHasHeader(&state, pindex) &&
                    PeerHasHeader(&state, pindex->pprev)) {
                    LogPrint(BCLog::NET,
                             "%s sending header-and-ids %s to peer=%d\n",
                             "PeerManager::NewPoWValidBlock",
                             hashBlock.ToString(), pnode->GetId());
 
                    const CSerializedNetMsg &ser_cmpctblock{lazy_ser.get()};
                    PushMessage(*pnode, ser_cmpctblock.Copy());
                    state.pindexBestHeaderSent = pindex;
                }
            });
}
 
void PeerManagerImpl::UpdatedBlockTip(const CBlockIndex *pindexNew,
                                      const CBlockIndex *pindexFork,
                                      bool fInitialDownload) {
    SetBestHeight(pindexNew->nHeight);
    SetServiceFlagsIBDCache(!fInitialDownload);
 
    // Don't relay inventory during initial block download.
    if (fInitialDownload) {
        return;
    }
 
    // Find the hashes of all blocks that weren't previously in the best chain.
    std::vector<BlockHash> vHashes;
    const CBlockIndex *pindexToAnnounce = pindexNew;
    while (pindexToAnnounce != pindexFork) {
        vHashes.push_back(pindexToAnnounce->GetBlockHash());
        pindexToAnnounce = pindexToAnnounce->pprev;
        if (vHashes.size() == MAX_BLOCKS_TO_ANNOUNCE) {
            // Limit announcements in case of a huge reorganization. Rely on the
            // peer's synchronization mechanism in that case.
            break;
        }
    }
 
    {
        LOCK(m_peer_mutex);
        for (auto &it : m_peer_map) {
            Peer &peer = *it.second;
            LOCK(peer.m_block_inv_mutex);
            for (const BlockHash &hash : reverse_iterate(vHashes)) {
                peer.m_blocks_for_headers_relay.push_back(hash);
            }
        }
    }
 
    m_connman.WakeMessageHandler();
}
 
void PeerManagerImpl::BlockChecked(const CBlock &block,
                                   const BlockValidationState &state) {
    LOCK(cs_main);
 
    const BlockHash hash = block.GetHash();
    std::map<BlockHash, std::pair<NodeId, bool>>::iterator it =
        mapBlockSource.find(hash);
 
    // If the block failed validation, we know where it came from and we're
    // still connected to that peer, maybe punish.
    if (state.IsInvalid() && it != mapBlockSource.end() &&
        State(it->second.first)) {
        MaybePunishNodeForBlock(/*nodeid=*/it->second.first, state,
                                /*via_compact_block=*/!it->second.second);
    }
    // Check that:
    // 1. The block is valid
    // 2. We're not in initial block download
    // 3. This is currently the best block we're aware of. We haven't updated
    //    the tip yet so we have no way to check this directly here. Instead we
    //    just check that there are currently no other blocks in flight.
    else if (state.IsValid() && !m_chainman.IsInitialBlockDownload() &&
             mapBlocksInFlight.count(hash) == mapBlocksInFlight.size()) {
        if (it != mapBlockSource.end()) {
            MaybeSetPeerAsAnnouncingHeaderAndIDs(it->second.first);
        }
    }
 
    if (it != mapBlockSource.end()) {
        mapBlockSource.erase(it);
    }
}
 
//
// Messages
//
 
bool PeerManagerImpl::AlreadyHaveTx(const TxId &txid,
                                    bool include_reconsiderable) {
    if (m_chainman.ActiveChain().Tip()->GetBlockHash() !=
        hashRecentRejectsChainTip) {
        // If the chain tip has changed previously rejected transactions
        // might be now valid, e.g. due to a nLockTime'd tx becoming
        // valid, or a double-spend. Reset the rejects filter and give
        // those txs a second chance.
        hashRecentRejectsChainTip =
            m_chainman.ActiveChain().Tip()->GetBlockHash();
        m_recent_rejects.reset();
        m_recent_rejects_package_reconsiderable.reset();
    }
 
    if (m_mempool.withOrphanage([&txid](const TxOrphanage &orphanage) {
            return orphanage.HaveTx(txid);
        })) {
        return true;
    }
 
    if (m_mempool.withConflicting([&txid](const TxConflicting &conflicting) {
            return conflicting.HaveTx(txid);
        })) {
        return true;
    }
 
    if (include_reconsiderable &&
        m_recent_rejects_package_reconsiderable.contains(txid)) {
        return true;
    }
 
    {
        LOCK(m_recent_confirmed_transactions_mutex);
        if (m_recent_confirmed_transactions.contains(txid)) {
            return true;
        }
    }
 
    return m_recent_rejects.contains(txid) || m_mempool.exists(txid);
}
 
bool PeerManagerImpl::AlreadyHaveBlock(const BlockHash &block_hash) {
    return m_chainman.m_blockman.LookupBlockIndex(block_hash) != nullptr;
}
 
bool PeerManagerImpl::AlreadyHaveProof(const avalanche::ProofId &proofid) {
    if (!Assume(m_avalanche)) {
        return false;
    }
 
    auto localProof = m_avalanche->getLocalProof();
    if (localProof && localProof->getId() == proofid) {
        return true;
    }
 
    return m_avalanche->withPeerManager([&proofid](avalanche::PeerManager &pm) {
        return pm.exists(proofid) || pm.isInvalid(proofid);
    });
}
 
void PeerManagerImpl::SendPings() {
    LOCK(m_peer_mutex);
    for (auto &it : m_peer_map) {
        it.second->m_ping_queued = true;
    }
}
 
void PeerManagerImpl::RelayTransaction(const TxId &txid) {
    LOCK(m_peer_mutex);
    for (auto &it : m_peer_map) {
        Peer &peer = *it.second;
        auto tx_relay = peer.GetTxRelay();
        if (!tx_relay) {
            continue;
        }
        LOCK(tx_relay->m_tx_inventory_mutex);
        // Only queue transactions for announcement once the version handshake
        // is completed. The time of arrival for these transactions is
        // otherwise at risk of leaking to a spy, if the spy is able to
        // distinguish transactions received during the handshake from the rest
        // in the announcement.
        if (tx_relay->m_next_inv_send_time == 0s) {
            continue;
        }
 
        if (!tx_relay->m_tx_inventory_known_filter.contains(txid) ||
            tx_relay->m_avalanche_stalled_txids.count(txid) > 0) {
            tx_relay->m_tx_inventory_to_send.insert(txid);
        }
    }
}
 
void PeerManagerImpl::RelayProof(const avalanche::ProofId &proofid) {
    LOCK(m_peer_mutex);
    for (auto &it : m_peer_map) {
        Peer &peer = *it.second;
 
        if (!peer.m_proof_relay) {
            continue;
        }
        LOCK(peer.m_proof_relay->m_proof_inventory_mutex);
        if (!peer.m_proof_relay->m_proof_inventory_known_filter.contains(
                proofid)) {
            peer.m_proof_relay->m_proof_inventory_to_send.insert(proofid);
        }
    }
}
 
void PeerManagerImpl::RelayAddress(NodeId originator, const CAddress &addr,
                                   bool fReachable) {
    // We choose the same nodes within a given 24h window (if the list of
    // connected nodes does not change) and we don't relay to nodes that already
    // know an address. So within 24h we will likely relay a given address once.
    // This is to prevent a peer from unjustly giving their address better
    // propagation by sending it to us repeatedly.
 
    if (!fReachable && !addr.IsRelayable()) {
        return;
    }
 
    // Relay to a limited number of other nodes
    // Use deterministic randomness to send to the same nodes for 24 hours
    // at a time so the m_addr_knowns of the chosen nodes prevent repeats
    const uint64_t hash_addr{CServiceHash(0, 0)(addr)};
    const auto current_time{GetTime<std::chrono::seconds>()};
    // Adding address hash makes exact rotation time different per address,
    // while preserving periodicity.
    const uint64_t time_addr{
        (static_cast<uint64_t>(count_seconds(current_time)) + hash_addr) /
        count_seconds(ROTATE_ADDR_RELAY_DEST_INTERVAL)};
 
    const CSipHasher hasher{
        m_connman.GetDeterministicRandomizer(RANDOMIZER_ID_ADDRESS_RELAY)
            .Write(hash_addr)
            .Write(time_addr)};
 
    // Relay reachable addresses to 2 peers. Unreachable addresses are relayed
    // randomly to 1 or 2 peers.
    unsigned int nRelayNodes = (fReachable || (hasher.Finalize() & 1)) ? 2 : 1;
    std::array<std::pair<uint64_t, Peer *>, 2> best{
        {{0, nullptr}, {0, nullptr}}};
    assert(nRelayNodes <= best.size());
 
    LOCK(m_peer_mutex);
 
    for (auto &[id, peer] : m_peer_map) {
        if (peer->m_addr_relay_enabled && id != originator &&
            IsAddrCompatible(*peer, addr)) {
            uint64_t hashKey = CSipHasher(hasher).Write(id).Finalize();
            for (unsigned int i = 0; i < nRelayNodes; i++) {
                if (hashKey > best[i].first) {
                    std::copy(best.begin() + i, best.begin() + nRelayNodes - 1,
                              best.begin() + i + 1);
                    best[i] = std::make_pair(hashKey, peer.get());
                    break;
                }
            }
        }
    };
 
    for (unsigned int i = 0; i < nRelayNodes && best[i].first != 0; i++) {
        PushAddress(*best[i].second, addr);
    }
}
 
void PeerManagerImpl::ProcessGetBlockData(const Config &config, CNode &pfrom,
                                          Peer &peer, const CInv &inv) {
    const BlockHash hash(inv.hash);
 
    std::shared_ptr<const CBlock> a_recent_block;
    std::shared_ptr<const CBlockHeaderAndShortTxIDs> a_recent_compact_block;
    {
        LOCK(m_most_recent_block_mutex);
        a_recent_block = m_most_recent_block;
        a_recent_compact_block = m_most_recent_compact_block;
    }
 
    bool need_activate_chain = false;
    {
        LOCK(cs_main);
        const CBlockIndex *pindex =
            m_chainman.m_blockman.LookupBlockIndex(hash);
        if (pindex) {
            if (pindex->HaveNumChainTxs() &&
                !pindex->IsValid(BlockValidity::SCRIPTS) &&
                pindex->IsValid(BlockValidity::TREE)) {
                // If we have the block and all of its parents, but have not yet
                // validated it, we might be in the middle of connecting it (ie
                // in the unlock of cs_main before ActivateBestChain but after
                // AcceptBlock). In this case, we need to run ActivateBestChain
                // prior to checking the relay conditions below.
                need_activate_chain = true;
            }
        }
    } // release cs_main before calling ActivateBestChain
    if (need_activate_chain) {
        BlockValidationState state;
        if (!m_chainman.ActiveChainstate().ActivateBestChain(
                state, a_recent_block, m_avalanche)) {
            LogPrint(BCLog::NET, "failed to activate chain (%s)\n",
                     state.ToString());
        }
    }
 
    const CBlockIndex *pindex{nullptr};
    const CBlockIndex *tip{nullptr};
    bool can_direct_fetch{false};
    FlatFilePos block_pos{};
    {
        LOCK(cs_main);
        pindex = m_chainman.m_blockman.LookupBlockIndex(hash);
        if (!pindex) {
            return;
        }
        if (!BlockRequestAllowed(pindex)) {
            LogPrint(BCLog::NET,
                     "%s: ignoring request from peer=%i for old "
                     "block that isn't in the main chain\n",
                     __func__, pfrom.GetId());
            return;
        }
        // Disconnect node in case we have reached the outbound limit for
        // serving historical blocks.
        if (m_connman.OutboundTargetReached(true) &&
            (((m_chainman.m_best_header != nullptr) &&
              (m_chainman.m_best_header->GetBlockTime() -
                   pindex->GetBlockTime() >
               HISTORICAL_BLOCK_AGE)) ||
             inv.IsMsgFilteredBlk()) &&
            // nodes with the download permission may exceed target
            !pfrom.HasPermission(NetPermissionFlags::Download)) {
            LogPrint(
                BCLog::NET,
                "historical block serving limit reached, disconnect peer=%d\n",
                pfrom.GetId());
            pfrom.fDisconnect = true;
            return;
        }
        tip = m_chainman.ActiveChain().Tip();
        // Avoid leaking prune-height by never sending blocks below the
        // NODE_NETWORK_LIMITED threshold.
        // Add two blocks buffer extension for possible races
        if (!pfrom.HasPermission(NetPermissionFlags::NoBan) &&
            ((((peer.m_our_services & NODE_NETWORK_LIMITED) ==
               NODE_NETWORK_LIMITED) &&
              ((peer.m_our_services & NODE_NETWORK) != NODE_NETWORK) &&
              (tip->nHeight - pindex->nHeight >
               (int)NODE_NETWORK_LIMITED_MIN_BLOCKS + 2)))) {
            LogPrint(BCLog::NET,
                     "Ignore block request below NODE_NETWORK_LIMITED "
                     "threshold, disconnect peer=%d\n",
                     pfrom.GetId());
 
            // disconnect node and prevent it from stalling (would otherwise
            // wait for the missing block)
            pfrom.fDisconnect = true;
            return;
        }
        // Pruned nodes may have deleted the block, so check whether it's
        // available before trying to send.
        if (!pindex->nStatus.hasData()) {
            return;
        }
        can_direct_fetch = CanDirectFetch();
        block_pos = pindex->GetBlockPos();
    }
 
    std::shared_ptr<const CBlock> pblock;
    auto handle_block_read_error = [&]() {
        if (WITH_LOCK(m_chainman.GetMutex(),
                      return m_chainman.m_blockman.IsBlockPruned(*pindex))) {
            LogDebug(BCLog::NET,
                     "Block was pruned before it could be read, disconnect "
                     "peer=%s\n",
                     pfrom.GetId());
        } else {
            LogError("Cannot load block from disk, disconnect peer=%d\n",
                     pfrom.GetId());
        }
        pfrom.fDisconnect = true;
    };
 
    if (a_recent_block && a_recent_block->GetHash() == pindex->GetBlockHash()) {
        pblock = a_recent_block;
    } else if (!inv.IsMsgCmpctBlk()) {
        // Fast-path: in this case it is possible to serve the block directly
        // from disk, as the network format matches the format on disk
        std::vector<uint8_t> block_data;
        if (!m_chainman.m_blockman.ReadRawBlock(block_data, block_pos)) {
            handle_block_read_error();
            return;
        }
        MakeAndPushMessage(pfrom, NetMsgType::BLOCK, Span{block_data});
        // Don't set pblock as we've sent the block
    } else {
        // Send block from disk
        std::shared_ptr<CBlock> pblockRead = std::make_shared<CBlock>();
        if (!m_chainman.m_blockman.ReadBlock(*pblockRead, block_pos)) {
            handle_block_read_error();
            return;
        }
        pblock = pblockRead;
    }
    if (pblock) {
        if (inv.IsMsgBlk()) {
            MakeAndPushMessage(pfrom, NetMsgType::BLOCK, *pblock);
        } else if (inv.IsMsgFilteredBlk()) {
            bool sendMerkleBlock = false;
            CMerkleBlock merkleBlock;
            if (auto tx_relay = peer.GetTxRelay()) {
                LOCK(tx_relay->m_bloom_filter_mutex);
                if (tx_relay->m_bloom_filter) {
                    sendMerkleBlock = true;
                    merkleBlock =
                        CMerkleBlock(*pblock, *tx_relay->m_bloom_filter);
                }
            }
            if (sendMerkleBlock) {
                MakeAndPushMessage(pfrom, NetMsgType::MERKLEBLOCK, merkleBlock);
                // CMerkleBlock just contains hashes, so also push any
                // transactions in the block the client did not see. This avoids
                // hurting performance by pointlessly requiring a round-trip.
                // Note that there is currently no way for a node to request any
                // single transactions we didn't send here - they must either
                // disconnect and retry or request the full block. Thus, the
                // protocol spec specified allows for us to provide duplicate
                // txn here, however we MUST always provide at least what the
                // remote peer needs.
                typedef std::pair<size_t, uint256> PairType;
                for (PairType &pair : merkleBlock.vMatchedTxn) {
                    MakeAndPushMessage(pfrom, NetMsgType::TX,
                                       *pblock->vtx[pair.first]);
                }
            }
            // else
            // no response
        } else if (inv.IsMsgCmpctBlk()) {
            // If a peer is asking for old blocks, we're almost guaranteed they
            // won't have a useful mempool to match against a compact block, and
            // we don't feel like constructing the object for them, so instead
            // we respond with the full, non-compact block.
            if (can_direct_fetch &&
                pindex->nHeight >= tip->nHeight - MAX_CMPCTBLOCK_DEPTH) {
                if (a_recent_compact_block &&
                    a_recent_compact_block->header.GetHash() ==
                        pindex->GetBlockHash()) {
                    MakeAndPushMessage(pfrom, NetMsgType::CMPCTBLOCK,
                                       *a_recent_compact_block);
                } else {
                    CBlockHeaderAndShortTxIDs cmpctblock(
                        *pblock, FastRandomContext().rand64());
                    MakeAndPushMessage(pfrom, NetMsgType::CMPCTBLOCK,
                                       cmpctblock);
                }
            } else {
                MakeAndPushMessage(pfrom, NetMsgType::BLOCK, *pblock);
            }
        }
    }
 
    {
        LOCK(peer.m_block_inv_mutex);
        // Trigger the peer node to send a getblocks request for the next
        // batch of inventory.
        if (hash == peer.m_continuation_block) {
            // Send immediately. This must send even if redundant, and
            // we want it right after the last block so they don't wait for
            // other stuff first.
            std::vector<CInv> vInv;
            vInv.push_back(CInv(MSG_BLOCK, tip->GetBlockHash()));
            MakeAndPushMessage(pfrom, NetMsgType::INV, vInv);
            peer.m_continuation_block = BlockHash();
        }
    }
}
 
CTransactionRef
PeerManagerImpl::FindTxForGetData(const Peer &peer, const TxId &txid,
                                  const std::chrono::seconds mempool_req,
                                  const std::chrono::seconds now) {
    auto txinfo = m_mempool.info(txid);
    if (txinfo.tx) {
        // If a TX could have been INVed in reply to a MEMPOOL request,
        // or is older than UNCONDITIONAL_RELAY_DELAY, permit the request
        // unconditionally.
        if ((mempool_req.count() && txinfo.m_time <= mempool_req) ||
            txinfo.m_time <= now - UNCONDITIONAL_RELAY_DELAY) {
            return std::move(txinfo.tx);
        }
    }
 
    {
        LOCK(cs_main);
 
        // Otherwise, the transaction might have been announced recently.
        bool recent =
            Assume(peer.GetTxRelay())->m_recently_announced_invs.contains(txid);
        if (recent && txinfo.tx) {
            return std::move(txinfo.tx);
        }
 
        // Or it might be from the most recent block
        {
            LOCK(m_most_recent_block_mutex);
            if (m_most_recent_block_txs != nullptr) {
                auto it = m_most_recent_block_txs->find(txid);
                if (it != m_most_recent_block_txs->end()) {
                    return it->second;
                }
            }
        }
    }
 
    return {};
}
 
avalanche::ProofRef
PeerManagerImpl::FindProofForGetData(const Peer &peer,
                                     const avalanche::ProofId &proofid,
                                     const std::chrono::seconds now) {
    avalanche::ProofRef proof;
 
    bool send_unconditionally =
        m_avalanche->withPeerManager([&](const avalanche::PeerManager &pm) {
            return pm.forPeer(proofid, [&](const avalanche::Peer &peer) {
                proof = peer.proof;
 
                // If we know that proof for long enough, allow for requesting
                // it.
                return peer.registration_time <=
                       now - UNCONDITIONAL_RELAY_DELAY;
            });
        });
 
    if (!proof) {
        // Always send our local proof if it gets requested, assuming it's
        // valid. This will make it easier to bind with peers upon startup where
        // the status of our proof is unknown pending for a block. Note that it
        // still needs to have been announced first (presumably via an avahello
        // message).
        proof = m_avalanche->getLocalProof();
    }
 
    // We don't have this proof
    if (!proof) {
        return avalanche::ProofRef();
    }
 
    if (send_unconditionally) {
        return proof;
    }
 
    // Otherwise, the proofs must have been announced recently.
    if (peer.m_proof_relay->m_recently_announced_proofs.contains(proofid)) {
        return proof;
    }
 
    return avalanche::ProofRef();
}
 
void PeerManagerImpl::ProcessGetData(
    const Config &config, CNode &pfrom, Peer &peer,
    const std::atomic<bool> &interruptMsgProc) {
    AssertLockNotHeld(cs_main);
 
    auto tx_relay = peer.GetTxRelay();
 
    std::deque<CInv>::iterator it = peer.m_getdata_requests.begin();
    std::vector<CInv> vNotFound;
 
    const auto now{GetTime<std::chrono::seconds>()};
    // Get last mempool request time
    const auto mempool_req = tx_relay != nullptr
                                 ? tx_relay->m_last_mempool_req.load()
                                 : std::chrono::seconds::min();
 
    // Process as many TX or AVA_PROOF items from the front of the getdata
    // queue as possible, since they're common and it's efficient to batch
    // process them.
    while (it != peer.m_getdata_requests.end() &&
           (it->IsMsgProof() || it->IsMsgTx())) {
        if (interruptMsgProc) {
            return;
        }
        // The send buffer provides backpressure. If there's no space in
        // the buffer, pause processing until the next call.
        if (pfrom.fPauseSend) {
            break;
        }
 
        const CInv &inv = *it++;
 
        if (inv.IsMsgProof()) {
            if (!m_avalanche) {
                vNotFound.push_back(inv);
                continue;
            }
            const avalanche::ProofId proofid(inv.hash);
            auto proof = FindProofForGetData(peer, proofid, now);
            if (proof) {
                MakeAndPushMessage(pfrom, NetMsgType::AVAPROOF, *proof);
                m_avalanche->withPeerManager([&](avalanche::PeerManager &pm) {
                    pm.removeUnbroadcastProof(proofid);
                });
            } else {
                vNotFound.push_back(inv);
            }
 
            continue;
        }
 
        if (inv.IsMsgTx()) {
            if (tx_relay == nullptr) {
                // Ignore GETDATA requests for transactions from
                // block-relay-only peers and peers that asked us not to
                // announce transactions.
                continue;
            }
 
            const TxId txid(inv.hash);
            CTransactionRef tx = FindTxForGetData(peer, txid, mempool_req, now);
            if (tx) {
                MakeAndPushMessage(pfrom, NetMsgType::TX, *tx);
                m_mempool.RemoveUnbroadcastTx(txid);
                // As we're going to send tx, make sure its unconfirmed parents
                // are made requestable.
                std::vector<TxId> parent_ids_to_add;
                {
                    LOCK(m_mempool.cs);
                    auto txiter = m_mempool.GetIter(tx->GetId());
                    if (txiter) {
                        auto &pentry = *txiter;
                        const CTxMemPoolEntry::Parents &parents =
                            (*pentry)->GetMemPoolParentsConst();
                        parent_ids_to_add.reserve(parents.size());
                        for (const auto &parent : parents) {
                            if (parent.get()->GetTime() >
                                now - UNCONDITIONAL_RELAY_DELAY) {
                                parent_ids_to_add.push_back(
                                    parent.get()->GetTx().GetId());
                            }
                        }
                    }
                }
                for (const TxId &parent_txid : parent_ids_to_add) {
                    // Relaying a transaction with a recent but unconfirmed
                    // parent.
                    if (WITH_LOCK(tx_relay->m_tx_inventory_mutex,
                                  return !tx_relay->m_tx_inventory_known_filter
                                              .contains(parent_txid))) {
                        tx_relay->m_recently_announced_invs.insert(parent_txid);
                    }
                }
            } else {
                vNotFound.push_back(inv);
            }
 
            continue;
        }
 
        // It's neither a proof nor a transaction
        break;
    }
 
    // Only process one BLOCK item per call, since they're uncommon and can be
    // expensive to process.
    if (it != peer.m_getdata_requests.end() && !pfrom.fPauseSend) {
        const CInv &inv = *it++;
        if (inv.IsGenBlkMsg()) {
            ProcessGetBlockData(config, pfrom, peer, inv);
        }
        // else: If the first item on the queue is an unknown type, we erase it
        // and continue processing the queue on the next call.
    }
 
    peer.m_getdata_requests.erase(peer.m_getdata_requests.begin(), it);
 
    if (!vNotFound.empty()) {
        // Let the peer know that we didn't find what it asked for, so it
        // doesn't have to wait around forever. SPV clients care about this
        // message: it's needed when they are recursively walking the
        // dependencies of relevant unconfirmed transactions. SPV clients want
        // to do that because they want to know about (and store and rebroadcast
        // and risk analyze) the dependencies of transactions relevant to them,
        // without having to download the entire memory pool. Also, other nodes
        // can use these messages to automatically request a transaction from
        // some other peer that annnounced it, and stop waiting for us to
        // respond. In normal operation, we often send NOTFOUND messages for
        // parents of transactions that we relay; if a peer is missing a parent,
        // they may assume we have them and request the parents from us.
        MakeAndPushMessage(pfrom, NetMsgType::NOTFOUND, vNotFound);
    }
}
 
void PeerManagerImpl::SendBlockTransactions(
    CNode &pfrom, Peer &peer, const CBlock &block,
    const BlockTransactionsRequest &req) {
    BlockTransactions resp(req);
    for (size_t i = 0; i < req.indices.size(); i++) {
        if (req.indices[i] >= block.vtx.size()) {
            Misbehaving(peer, "getblocktxn with out-of-bounds tx indices");
            return;
        }
        resp.txn[i] = block.vtx[req.indices[i]];
    }
    LOCK(cs_main);
    MakeAndPushMessage(pfrom, NetMsgType::BLOCKTXN, resp);
}
 
bool PeerManagerImpl::CheckHeadersPoW(const std::vector<CBlockHeader> &headers,
                                      const Consensus::Params &consensusParams,
                                      Peer &peer) {
    // Do these headers have proof-of-work matching what's claimed?
    if (!HasValidProofOfWork(headers, consensusParams)) {
        Misbehaving(peer, "header with invalid proof of work");
        return false;
    }
 
    // Are these headers connected to each other?
    if (!CheckHeadersAreContinuous(headers)) {
        Misbehaving(peer, "non-continuous headers sequence");
        return false;
    }
    return true;
}
 
arith_uint256 PeerManagerImpl::GetAntiDoSWorkThreshold() {
    arith_uint256 near_chaintip_work = 0;
    LOCK(cs_main);
    if (m_chainman.ActiveChain().Tip() != nullptr) {
        const CBlockIndex *tip = m_chainman.ActiveChain().Tip();
        // Use a 144 block buffer, so that we'll accept headers that fork from
        // near our tip.
        near_chaintip_work =
            tip->nChainWork -
            std::min<arith_uint256>(144 * GetBlockProof(*tip), tip->nChainWork);
    }
    return std::max(near_chaintip_work, m_chainman.MinimumChainWork());
}
 
void PeerManagerImpl::HandleUnconnectingHeaders(
    CNode &pfrom, Peer &peer, const std::vector<CBlockHeader> &headers) {
    // Try to fill in the missing headers.
    const CBlockIndex *best_header{
        WITH_LOCK(cs_main, return m_chainman.m_best_header)};
    if (MaybeSendGetHeaders(pfrom, GetLocator(best_header), peer)) {
        LogPrint(
            BCLog::NET,
            "received header %s: missing prev block %s, sending getheaders "
            "(%d) to end (peer=%d)\n",
            headers[0].GetHash().ToString(),
            headers[0].hashPrevBlock.ToString(), best_header->nHeight,
            pfrom.GetId());
    }
 
    // Set hashLastUnknownBlock for this peer, so that if we
    // eventually get the headers - even from a different peer -
    // we can use this peer to download.
    WITH_LOCK(cs_main,
              UpdateBlockAvailability(pfrom.GetId(), headers.back().GetHash()));
}
 
bool PeerManagerImpl::CheckHeadersAreContinuous(
    const std::vector<CBlockHeader> &headers) const {
    BlockHash hashLastBlock;
    for (const CBlockHeader &header : headers) {
        if (!hashLastBlock.IsNull() && header.hashPrevBlock != hashLastBlock) {
            return false;
        }
        hashLastBlock = header.GetHash();
    }
    return true;
}
 
bool PeerManagerImpl::IsContinuationOfLowWorkHeadersSync(
    Peer &peer, CNode &pfrom, std::vector<CBlockHeader> &headers) {
    if (peer.m_headers_sync) {
        auto result = peer.m_headers_sync->ProcessNextHeaders(
            headers, headers.size() == MAX_HEADERS_RESULTS);
        // If it is a valid continuation, we should treat the existing
        // getheaders request as responded to.
        if (result.success) {
            peer.m_last_getheaders_timestamp = {};
        }
        if (result.request_more) {
            auto locator = peer.m_headers_sync->NextHeadersRequestLocator();
            // If we were instructed to ask for a locator, it should not be
            // empty.
            Assume(!locator.vHave.empty());
            // We can only be instructed to request more if processing was
            // successful.
            Assume(result.success);
            if (!locator.vHave.empty()) {
                // It should be impossible for the getheaders request to fail,
                // because we just cleared the last getheaders timestamp.
                bool sent_getheaders =
                    MaybeSendGetHeaders(pfrom, locator, peer);
                Assume(sent_getheaders);
                LogPrint(BCLog::NET, "more getheaders (from %s) to peer=%d\n",
                         locator.vHave.front().ToString(), pfrom.GetId());
            }
        }
 
        if (peer.m_headers_sync->GetState() == HeadersSyncState::State::FINAL) {
            peer.m_headers_sync.reset(nullptr);
 
            // Delete this peer's entry in m_headers_presync_stats.
            // If this is m_headers_presync_bestpeer, it will be replaced later
            // by the next peer that triggers the else{} branch below.
            LOCK(m_headers_presync_mutex);
            m_headers_presync_stats.erase(pfrom.GetId());
        } else {
            // Build statistics for this peer's sync.
            HeadersPresyncStats stats;
            stats.first = peer.m_headers_sync->GetPresyncWork();
            if (peer.m_headers_sync->GetState() ==
                HeadersSyncState::State::PRESYNC) {
                stats.second = {peer.m_headers_sync->GetPresyncHeight(),
                                peer.m_headers_sync->GetPresyncTime()};
            }
 
            // Update statistics in stats.
            LOCK(m_headers_presync_mutex);
            m_headers_presync_stats[pfrom.GetId()] = stats;
            auto best_it =
                m_headers_presync_stats.find(m_headers_presync_bestpeer);
            bool best_updated = false;
            if (best_it == m_headers_presync_stats.end()) {
                // If the cached best peer is outdated, iterate over all
                // remaining ones (including newly updated one) to find the best
                // one.
                NodeId peer_best{-1};
                const HeadersPresyncStats *stat_best{nullptr};
                for (const auto &[_peer, _stat] : m_headers_presync_stats) {
                    if (!stat_best || _stat > *stat_best) {
                        peer_best = _peer;
                        stat_best = &_stat;
                    }
                }
                m_headers_presync_bestpeer = peer_best;
                best_updated = (peer_best == pfrom.GetId());
            } else if (best_it->first == pfrom.GetId() ||
                       stats > best_it->second) {
                // pfrom was and remains the best peer, or pfrom just became
                // best.
                m_headers_presync_bestpeer = pfrom.GetId();
                best_updated = true;
            }
            if (best_updated && stats.second.has_value()) {
                // If the best peer updated, and it is in its first phase,
                // signal.
                m_headers_presync_should_signal = true;
            }
        }
 
        if (result.success) {
            // We only overwrite the headers passed in if processing was
            // successful.
            headers.swap(result.pow_validated_headers);
        }
 
        return result.success;
    }
    // Either we didn't have a sync in progress, or something went wrong
    // processing these headers, or we are returning headers to the caller to
    // process.
    return false;
}
 
bool PeerManagerImpl::TryLowWorkHeadersSync(
    Peer &peer, CNode &pfrom, const CBlockIndex *chain_start_header,
    std::vector<CBlockHeader> &headers) {
    // Calculate the total work on this chain.
    arith_uint256 total_work =
        chain_start_header->nChainWork + CalculateHeadersWork(headers);
 
    // Our dynamic anti-DoS threshold (minimum work required on a headers chain
    // before we'll store it)
    arith_uint256 minimum_chain_work = GetAntiDoSWorkThreshold();
 
    // Avoid DoS via low-difficulty-headers by only processing if the headers
    // are part of a chain with sufficient work.
    if (total_work < minimum_chain_work) {
        // Only try to sync with this peer if their headers message was full;
        // otherwise they don't have more headers after this so no point in
        // trying to sync their too-little-work chain.
        if (headers.size() == MAX_HEADERS_RESULTS) {
            // Note: we could advance to the last header in this set that is
            // known to us, rather than starting at the first header (which we
            // may already have); however this is unlikely to matter much since
            // ProcessHeadersMessage() already handles the case where all
            // headers in a received message are already known and are
            // ancestors of m_best_header or chainActive.Tip(), by skipping
            // this logic in that case. So even if the first header in this set
            // of headers is known, some header in this set must be new, so
            // advancing to the first unknown header would be a small effect.
            LOCK(peer.m_headers_sync_mutex);
            peer.m_headers_sync.reset(
                new HeadersSyncState(peer.m_id, m_chainparams.GetConsensus(),
                                     chain_start_header, minimum_chain_work));
 
            // Now a HeadersSyncState object for tracking this synchronization
            // is created, process the headers using it as normal. Failures are
            // handled inside of IsContinuationOfLowWorkHeadersSync.
            (void)IsContinuationOfLowWorkHeadersSync(peer, pfrom, headers);
        } else {
            LogPrint(BCLog::NET,
                     "Ignoring low-work chain (height=%u) from peer=%d\n",
                     chain_start_header->nHeight + headers.size(),
                     pfrom.GetId());
        }
        // The peer has not yet given us a chain that meets our work threshold,
        // so we want to prevent further processing of the headers in any case.
        headers = {};
        return true;
    }
 
    return false;
}
 
bool PeerManagerImpl::IsAncestorOfBestHeaderOrTip(const CBlockIndex *header) {
    return header != nullptr &&
           ((m_chainman.m_best_header != nullptr &&
             header ==
                 m_chainman.m_best_header->GetAncestor(header->nHeight)) ||
            m_chainman.ActiveChain().Contains(header));
}
 
bool PeerManagerImpl::MaybeSendGetHeaders(CNode &pfrom,
                                          const CBlockLocator &locator,
                                          Peer &peer) {
    const auto current_time = NodeClock::now();
 
    // Only allow a new getheaders message to go out if we don't have a recent
    // one already in-flight
    if (current_time - peer.m_last_getheaders_timestamp >
        HEADERS_RESPONSE_TIME) {
        MakeAndPushMessage(pfrom, NetMsgType::GETHEADERS, locator, uint256());
        peer.m_last_getheaders_timestamp = current_time;
        return true;
    }
    return false;
}
 
void PeerManagerImpl::HeadersDirectFetchBlocks(const Config &config,
                                               CNode &pfrom,
                                               const CBlockIndex &last_header) {
    LOCK(cs_main);
    CNodeState *nodestate = State(pfrom.GetId());
 
    if (CanDirectFetch() && last_header.IsValid(BlockValidity::TREE) &&
        m_chainman.ActiveChain().Tip()->nChainWork <= last_header.nChainWork) {
        std::vector<const CBlockIndex *> vToFetch;
        const CBlockIndex *pindexWalk{&last_header};
        // Calculate all the blocks we'd need to switch to last_header, up to
        // a limit.
        while (pindexWalk && !m_chainman.ActiveChain().Contains(pindexWalk) &&
               vToFetch.size() <= MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
            if (!pindexWalk->nStatus.hasData() &&
                !IsBlockRequested(pindexWalk->GetBlockHash())) {
                // We don't have this block, and it's not yet in flight.
                vToFetch.push_back(pindexWalk);
            }
            pindexWalk = pindexWalk->pprev;
        }
        // If pindexWalk still isn't on our main chain, we're looking at a
        // very large reorg at a time we think we're close to caught up to
        // the main chain -- this shouldn't really happen. Bail out on the
        // direct fetch and rely on parallel download instead.
        if (!m_chainman.ActiveChain().Contains(pindexWalk)) {
            LogPrint(BCLog::NET, "Large reorg, won't direct fetch to %s (%d)\n",
                     last_header.GetBlockHash().ToString(),
                     last_header.nHeight);
        } else {
            std::vector<CInv> vGetData;
            // Download as much as possible, from earliest to latest.
            for (const CBlockIndex *pindex : reverse_iterate(vToFetch)) {
                if (nodestate->vBlocksInFlight.size() >=
                    MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
                    // Can't download any more from this peer
                    break;
                }
                vGetData.push_back(CInv(MSG_BLOCK, pindex->GetBlockHash()));
                BlockRequested(config, pfrom.GetId(), *pindex);
                LogPrint(BCLog::NET, "Requesting block %s from  peer=%d\n",
                         pindex->GetBlockHash().ToString(), pfrom.GetId());
            }
            if (vGetData.size() > 1) {
                LogPrint(BCLog::NET,
                         "Downloading blocks toward %s (%d) via headers "
                         "direct fetch\n",
                         last_header.GetBlockHash().ToString(),
                         last_header.nHeight);
            }
            if (vGetData.size() > 0) {
                if (!m_opts.ignore_incoming_txs &&
                    nodestate->m_provides_cmpctblocks && vGetData.size() == 1 &&
                    mapBlocksInFlight.size() == 1 &&
                    last_header.pprev->IsValid(BlockValidity::CHAIN)) {
                    // In any case, we want to download using a compact
                    // block, not a regular one.
                    vGetData[0] = CInv(MSG_CMPCT_BLOCK, vGetData[0].hash);
                }
                MakeAndPushMessage(pfrom, NetMsgType::GETDATA, vGetData);
            }
        }
    }
}
 
void PeerManagerImpl::UpdatePeerStateForReceivedHeaders(
    CNode &pfrom, Peer &peer, const CBlockIndex &last_header,
    bool received_new_header, bool may_have_more_headers) {
    LOCK(cs_main);
 
    CNodeState *nodestate = State(pfrom.GetId());
 
    UpdateBlockAvailability(pfrom.GetId(), last_header.GetBlockHash());
 
    // From here, pindexBestKnownBlock should be guaranteed to be non-null,
    // because it is set in UpdateBlockAvailability. Some nullptr checks are
    // still present, however, as belt-and-suspenders.
 
    if (received_new_header &&
        last_header.nChainWork > m_chainman.ActiveChain().Tip()->nChainWork) {
        nodestate->m_last_block_announcement = GetTime();
    }
 
    // If we're in IBD, we want outbound peers that will serve us a useful
    // chain. Disconnect peers that are on chains with insufficient work.
    if (m_chainman.IsInitialBlockDownload() && !may_have_more_headers) {
        // When nCount < MAX_HEADERS_RESULTS, we know we have no more
        // headers to fetch from this peer.
        if (nodestate->pindexBestKnownBlock &&
            nodestate->pindexBestKnownBlock->nChainWork <
                m_chainman.MinimumChainWork()) {
            // This peer has too little work on their headers chain to help
            // us sync -- disconnect if it is an outbound disconnection
            // candidate.
            // Note: We compare their tip to the minimum chain work (rather than
            // m_chainman.ActiveChain().Tip()) because we won't start block
            // download until we have a headers chain that has at least
            // the minimum chain work, even if a peer has a chain past our tip,
            // as an anti-DoS measure.
            if (pfrom.IsOutboundOrBlockRelayConn()) {
                LogPrintf("Disconnecting outbound peer %d -- headers "
                          "chain has insufficient work\n",
                          pfrom.GetId());
                pfrom.fDisconnect = true;
            }
        }
    }
 
    // If this is an outbound full-relay peer, check to see if we should
    // protect it from the bad/lagging chain logic.
    // Note that outbound block-relay peers are excluded from this
    // protection, and thus always subject to eviction under the bad/lagging
    // chain logic.
    // See ChainSyncTimeoutState.
    if (!pfrom.fDisconnect && pfrom.IsFullOutboundConn() &&
        nodestate->pindexBestKnownBlock != nullptr) {
        if (m_outbound_peers_with_protect_from_disconnect <
                MAX_OUTBOUND_PEERS_TO_PROTECT_FROM_DISCONNECT &&
            nodestate->pindexBestKnownBlock->nChainWork >=
                m_chainman.ActiveChain().Tip()->nChainWork &&
            !nodestate->m_chain_sync.m_protect) {
            LogPrint(BCLog::NET, "Protecting outbound peer=%d from eviction\n",
                     pfrom.GetId());
            nodestate->m_chain_sync.m_protect = true;
            ++m_outbound_peers_with_protect_from_disconnect;
        }
    }
}
 
void PeerManagerImpl::ProcessHeadersMessage(const Config &config, CNode &pfrom,
                                            Peer &peer,
                                            std::vector<CBlockHeader> &&headers,
                                            bool via_compact_block) {
    size_t nCount = headers.size();
 
    if (nCount == 0) {
        // Nothing interesting. Stop asking this peers for more headers.
        // If we were in the middle of headers sync, receiving an empty headers
        // message suggests that the peer suddenly has nothing to give us
        // (perhaps it reorged to our chain). Clear download state for this
        // peer.
        LOCK(peer.m_headers_sync_mutex);
        if (peer.m_headers_sync) {
            peer.m_headers_sync.reset(nullptr);
            LOCK(m_headers_presync_mutex);
            m_headers_presync_stats.erase(pfrom.GetId());
        }
        // A headers message with no headers cannot be an announcement, so
        // assume it is a response to our last getheaders request, if there is
        // one.
        peer.m_last_getheaders_timestamp = {};
        return;
    }
 
    // Before we do any processing, make sure these pass basic sanity checks.
    // We'll rely on headers having valid proof-of-work further down, as an
    // anti-DoS criteria (note: this check is required before passing any
    // headers into HeadersSyncState).
    if (!CheckHeadersPoW(headers, m_chainparams.GetConsensus(), peer)) {
        // Misbehaving() calls are handled within CheckHeadersPoW(), so we can
        // just return. (Note that even if a header is announced via compact
        // block, the header itself should be valid, so this type of error can
        // always be punished.)
        return;
    }
 
    const CBlockIndex *pindexLast = nullptr;
 
    // We'll set already_validated_work to true if these headers are
    // successfully processed as part of a low-work headers sync in progress
    // (either in PRESYNC or REDOWNLOAD phase).
    // If true, this will mean that any headers returned to us (ie during
    // REDOWNLOAD) can be validated without further anti-DoS checks.
    bool already_validated_work = false;
 
    // If we're in the middle of headers sync, let it do its magic.
    bool have_headers_sync = false;
    {
        LOCK(peer.m_headers_sync_mutex);
 
        already_validated_work =
            IsContinuationOfLowWorkHeadersSync(peer, pfrom, headers);
 
        // The headers we passed in may have been:
        // - untouched, perhaps if no headers-sync was in progress, or some
        //   failure occurred
        // - erased, such as if the headers were successfully processed and no
        //   additional headers processing needs to take place (such as if we
        //   are still in PRESYNC)
        // - replaced with headers that are now ready for validation, such as
        //   during the REDOWNLOAD phase of a low-work headers sync.
        // So just check whether we still have headers that we need to process,
        // or not.
        if (headers.empty()) {
            return;
        }
 
        have_headers_sync = !!peer.m_headers_sync;
    }
 
    // Do these headers connect to something in our block index?
    const CBlockIndex *chain_start_header{
        WITH_LOCK(::cs_main, return m_chainman.m_blockman.LookupBlockIndex(
                                 headers[0].hashPrevBlock))};
    bool headers_connect_blockindex{chain_start_header != nullptr};
 
    if (!headers_connect_blockindex) {
        // This could be a BIP 130 block announcement, use
        // special logic for handling headers that don't connect, as this
        // could be benign.
        HandleUnconnectingHeaders(pfrom, peer, headers);
        return;
    }
 
    // If headers connect, assume that this is in response to any outstanding
    // getheaders request we may have sent, and clear out the time of our last
    // request. Non-connecting headers cannot be a response to a getheaders
    // request.
    peer.m_last_getheaders_timestamp = {};
 
    // If the headers we received are already in memory and an ancestor of
    // m_best_header or our tip, skip anti-DoS checks. These headers will not
    // use any more memory (and we are not leaking information that could be
    // used to fingerprint us).
    const CBlockIndex *last_received_header{nullptr};
    {
        LOCK(cs_main);
        last_received_header =
            m_chainman.m_blockman.LookupBlockIndex(headers.back().GetHash());
        if (IsAncestorOfBestHeaderOrTip(last_received_header)) {
            already_validated_work = true;
        }
    }
 
    // If our peer has NetPermissionFlags::NoBan privileges, then bypass our
    // anti-DoS logic (this saves bandwidth when we connect to a trusted peer
    // on startup).
    if (pfrom.HasPermission(NetPermissionFlags::NoBan)) {
        already_validated_work = true;
    }
 
    // At this point, the headers connect to something in our block index.
    // Do anti-DoS checks to determine if we should process or store for later
    // processing.
    if (!already_validated_work &&
        TryLowWorkHeadersSync(peer, pfrom, chain_start_header, headers)) {
        // If we successfully started a low-work headers sync, then there
        // should be no headers to process any further.
        Assume(headers.empty());
        return;
    }
 
    // At this point, we have a set of headers with sufficient work on them
    // which can be processed.
 
    // If we don't have the last header, then this peer will have given us
    // something new (if these headers are valid).
    bool received_new_header{last_received_header == nullptr};
 
    // Now process all the headers.
    BlockValidationState state;
    if (!m_chainman.ProcessNewBlockHeaders(headers, /*min_pow_checked=*/true,
                                           state, &pindexLast)) {
        if (state.IsInvalid()) {
            MaybePunishNodeForBlock(pfrom.GetId(), state, via_compact_block,
                                    "invalid header received");
            return;
        }
    }
    assert(pindexLast);
 
    // Consider fetching more headers if we are not using our headers-sync
    // mechanism.
    if (nCount == MAX_HEADERS_RESULTS && !have_headers_sync) {
        // Headers message had its maximum size; the peer may have more headers.
        if (MaybeSendGetHeaders(pfrom, GetLocator(pindexLast), peer)) {
            LogPrint(
                BCLog::NET,
                "more getheaders (%d) to end to peer=%d (startheight:%d)\n",
                pindexLast->nHeight, pfrom.GetId(), peer.m_starting_height);
        }
    }
 
    UpdatePeerStateForReceivedHeaders(pfrom, peer, *pindexLast,
                                      received_new_header,
                                      nCount == MAX_HEADERS_RESULTS);
 
    // Consider immediately downloading blocks.
    HeadersDirectFetchBlocks(config, pfrom, *pindexLast);
}
 
void PeerManagerImpl::ProcessInvalidTx(NodeId nodeid,
                                       const CTransactionRef &ptx,
                                       const TxValidationState &state,
                                       bool maybe_add_extra_compact_tx) {
    AssertLockNotHeld(m_peer_mutex);
    AssertLockHeld(g_msgproc_mutex);
    AssertLockHeld(cs_main);
 
    const TxId &txid = ptx->GetId();
 
    LogPrint(BCLog::MEMPOOLREJ, "%s from peer=%d was not accepted: %s\n",
             txid.ToString(), nodeid, state.ToString());
 
    if (state.GetResult() == TxValidationResult::TX_MISSING_INPUTS) {
        return;
    }
 
    if (m_avalanche &&
        m_avalanche->isPreconsensusActivated(m_chainman.ActiveTip()) &&
        state.GetResult() == TxValidationResult::TX_AVALANCHE_RECONSIDERABLE) {
        return;
    }
 
    if (state.GetResult() == TxValidationResult::TX_PACKAGE_RECONSIDERABLE) {
        // If the result is TX_PACKAGE_RECONSIDERABLE, add it to
        // m_recent_rejects_package_reconsiderable because we should not
        // download or submit this transaction by itself again, but may submit
        // it as part of a package later.
        m_recent_rejects_package_reconsiderable.insert(txid);
    } else {
        m_recent_rejects.insert(txid);
    }
    m_txrequest.ForgetInvId(txid);
 
    if (maybe_add_extra_compact_tx && RecursiveDynamicUsage(*ptx) < 100000) {
        AddToCompactExtraTransactions(ptx);
    }
 
    MaybePunishNodeForTx(nodeid, state);
 
    // If the tx failed in ProcessOrphanTx, it should be removed from the
    // orphanage unless the tx was still missing inputs. If the tx was not in
    // the orphanage, EraseTx does nothing and returns 0.
    if (m_mempool.withOrphanage([&txid](TxOrphanage &orphanage) {
            return orphanage.EraseTx(txid);
        }) > 0) {
        LogPrint(BCLog::TXPACKAGES, "   removed orphan tx %s\n",
                 txid.ToString());
    }
}
 
void PeerManagerImpl::ProcessValidTx(NodeId nodeid, const CTransactionRef &tx) {
    AssertLockNotHeld(m_peer_mutex);
    AssertLockHeld(g_msgproc_mutex);
    AssertLockHeld(cs_main);
 
    // As this version of the transaction was acceptable, we can forget about
    // any requests for it. No-op if the tx is not in txrequest.
    m_txrequest.ForgetInvId(tx->GetId());
 
    m_mempool.withOrphanage([&tx](TxOrphanage &orphanage) {
        orphanage.AddChildrenToWorkSet(*tx);
        // If it came from the orphanage, remove it. No-op if the tx is not in
        // txorphanage.
        orphanage.EraseTx(tx->GetId());
    });
 
    LogPrint(
        BCLog::MEMPOOL,
        "AcceptToMemoryPool: peer=%d: accepted %s (poolsz %u txn, %u kB)\n",
        nodeid, tx->GetId().ToString(), m_mempool.size(),
        m_mempool.DynamicMemoryUsage() / 1000);
 
    RelayTransaction(tx->GetId());
}
 
void PeerManagerImpl::ProcessPackageResult(
    const PackageToValidate &package_to_validate,
    const PackageMempoolAcceptResult &package_result) {
    AssertLockNotHeld(m_peer_mutex);
    AssertLockHeld(g_msgproc_mutex);
    AssertLockHeld(cs_main);
 
    const auto &package = package_to_validate.m_txns;
    const auto &senders = package_to_validate.m_senders;
 
    if (package_result.m_state.IsInvalid()) {
        m_recent_rejects_package_reconsiderable.insert(GetPackageHash(package));
    }
    // We currently only expect to process 1-parent-1-child packages. Remove if
    // this changes.
    if (!Assume(package.size() == 2)) {
        return;
    }
 
    // Iterate backwards to erase in-package descendants from the orphanage
    // before they become relevant in AddChildrenToWorkSet.
    auto package_iter = package.rbegin();
    auto senders_iter = senders.rbegin();
    while (package_iter != package.rend()) {
        const auto &tx = *package_iter;
        const NodeId nodeid = *senders_iter;
        const auto it_result{package_result.m_tx_results.find(tx->GetId())};
 
        // It is not guaranteed that a result exists for every transaction.
        if (it_result != package_result.m_tx_results.end()) {
            const auto &tx_result = it_result->second;
            switch (tx_result.m_result_type) {
                case MempoolAcceptResult::ResultType::VALID: {
                    ProcessValidTx(nodeid, tx);
                    break;
                }
                case MempoolAcceptResult::ResultType::INVALID: {
                    // Don't add to vExtraTxnForCompact, as these transactions
                    // should have already been added there when added to the
                    // orphanage or rejected for TX_PACKAGE_RECONSIDERABLE.
                    // This should be updated if package submission is ever used
                    // for transactions that haven't already been validated
                    // before.
                    ProcessInvalidTx(nodeid, tx, tx_result.m_state,
                                     /*maybe_add_extra_compact_tx=*/false);
                    break;
                }
                case MempoolAcceptResult::ResultType::MEMPOOL_ENTRY: {
                    // AlreadyHaveTx() should be catching transactions that are
                    // already in mempool.
                    Assume(false);
                    break;
                }
            }
        }
        package_iter++;
        senders_iter++;
    }
}
 
std::optional<PeerManagerImpl::PackageToValidate>
PeerManagerImpl::Find1P1CPackage(const CTransactionRef &ptx, NodeId nodeid) {
    AssertLockNotHeld(m_peer_mutex);
    AssertLockHeld(g_msgproc_mutex);
    AssertLockHeld(cs_main);
 
    const auto &parent_txid{ptx->GetId()};
 
    Assume(m_recent_rejects_package_reconsiderable.contains(parent_txid));
 
    // Prefer children from this peer. This helps prevent censorship attempts in
    // which an attacker sends lots of fake children for the parent, and we
    // (unluckily) keep selecting the fake children instead of the real one
    // provided by the honest peer.
    const auto cpfp_candidates_same_peer{
        m_mempool.withOrphanage([&ptx, nodeid](const TxOrphanage &orphanage) {
            return orphanage.GetChildrenFromSamePeer(ptx, nodeid);
        })};
 
    // These children should be sorted from newest to oldest.
    for (const auto &child : cpfp_candidates_same_peer) {
        Package maybe_cpfp_package{ptx, child};
        if (!m_recent_rejects_package_reconsiderable.contains(
                GetPackageHash(maybe_cpfp_package))) {
            return PeerManagerImpl::PackageToValidate{ptx, child, nodeid,
                                                      nodeid};
        }
    }
 
    // If no suitable candidate from the same peer is found, also try children
    // that were provided by a different peer. This is useful because sometimes
    // multiple peers announce both transactions to us, and we happen to
    // download them from different peers (we wouldn't have known that these 2
    // transactions are related). We still want to find 1p1c packages then.
    //
    // If we start tracking all announcers of orphans, we can restrict this
    // logic to parent + child pairs in which both were provided by the same
    // peer, i.e. delete this step.
    const auto cpfp_candidates_different_peer{
        m_mempool.withOrphanage([&ptx, nodeid](const TxOrphanage &orphanage) {
            return orphanage.GetChildrenFromDifferentPeer(ptx, nodeid);
        })};
 
    // Find the first 1p1c that hasn't already been rejected. We randomize the
    // order to not create a bias that attackers can use to delay package
    // acceptance.
    //
    // Create a random permutation of the indices.
    std::vector<size_t> tx_indices(cpfp_candidates_different_peer.size());
    std::iota(tx_indices.begin(), tx_indices.end(), 0);
    Shuffle(tx_indices.begin(), tx_indices.end(), m_rng);
 
    for (const auto index : tx_indices) {
        // If we already tried a package and failed for any reason, the combined
        // hash was cached in m_recent_rejects_package_reconsiderable.
        const auto [child_tx, child_sender] =
            cpfp_candidates_different_peer.at(index);
        Package maybe_cpfp_package{ptx, child_tx};
        if (!m_recent_rejects_package_reconsiderable.contains(
                GetPackageHash(maybe_cpfp_package))) {
            return PeerManagerImpl::PackageToValidate{ptx, child_tx, nodeid,
                                                      child_sender};
        }
    }
    return std::nullopt;
}
 
bool PeerManagerImpl::ProcessOrphanTx(const Config &config, Peer &peer) {
    AssertLockHeld(g_msgproc_mutex);
    LOCK(cs_main);
 
    while (CTransactionRef porphanTx =
               m_mempool.withOrphanage([&peer](TxOrphanage &orphanage) {
                   return orphanage.GetTxToReconsider(peer.m_id);
               })) {
        const MempoolAcceptResult result =
            m_chainman.ProcessTransaction(porphanTx);
        const TxValidationState &state = result.m_state;
        const TxId &orphanTxId = porphanTx->GetId();
 
        if (result.m_result_type == MempoolAcceptResult::ResultType::VALID) {
            LogPrint(BCLog::TXPACKAGES, "   accepted orphan tx %s\n",
                     orphanTxId.ToString());
            ProcessValidTx(peer.m_id, porphanTx);
            return true;
        }
 
        if (state.GetResult() != TxValidationResult::TX_MISSING_INPUTS) {
            LogPrint(BCLog::TXPACKAGES,
                     "   invalid orphan tx %s from peer=%d. %s\n",
                     orphanTxId.ToString(), peer.m_id, state.ToString());
 
            if (Assume(state.IsInvalid() &&
                       state.GetResult() != TxValidationResult::TX_NO_MEMPOOL &&
                       state.GetResult() !=
                           TxValidationResult::TX_RESULT_UNSET)) {
                ProcessInvalidTx(peer.m_id, porphanTx, state,
                                 /*maybe_add_extra_compact_tx=*/false);
            }
 
            return true;
        }
    }
 
    return false;
}
 
bool PeerManagerImpl::PrepareBlockFilterRequest(
    CNode &node, Peer &peer, BlockFilterType filter_type, uint32_t start_height,
    const BlockHash &stop_hash, uint32_t max_height_diff,
    const CBlockIndex *&stop_index, BlockFilterIndex *&filter_index) {
    const bool supported_filter_type =
        (filter_type == BlockFilterType::BASIC &&
         (peer.m_our_services & NODE_COMPACT_FILTERS));
    if (!supported_filter_type) {
        LogPrint(BCLog::NET,
                 "peer %d requested unsupported block filter type: %d\n",
                 node.GetId(), static_cast<uint8_t>(filter_type));
        node.fDisconnect = true;
        return false;
    }
 
    {
        LOCK(cs_main);
        stop_index = m_chainman.m_blockman.LookupBlockIndex(stop_hash);
 
        // Check that the stop block exists and the peer would be allowed to
        // fetch it.
        if (!stop_index || !BlockRequestAllowed(stop_index)) {
            LogPrint(BCLog::NET, "peer %d requested invalid block hash: %s\n",
                     node.GetId(), stop_hash.ToString());
            node.fDisconnect = true;
            return false;
        }
    }
 
    uint32_t stop_height = stop_index->nHeight;
    if (start_height > stop_height) {
        LogPrint(
            BCLog::NET,
            "peer %d sent invalid getcfilters/getcfheaders with " /* Continued
                                                                   */
            "start height %d and stop height %d\n",
            node.GetId(), start_height, stop_height);
        node.fDisconnect = true;
        return false;
    }
    if (stop_height - start_height >= max_height_diff) {
        LogPrint(BCLog::NET,
                 "peer %d requested too many cfilters/cfheaders: %d / %d\n",
                 node.GetId(), stop_height - start_height + 1, max_height_diff);
        node.fDisconnect = true;
        return false;
    }
 
    filter_index = GetBlockFilterIndex(filter_type);
    if (!filter_index) {
        LogPrint(BCLog::NET, "Filter index for supported type %s not found\n",
                 BlockFilterTypeName(filter_type));
        return false;
    }
 
    return true;
}
 
void PeerManagerImpl::ProcessGetCFilters(CNode &node, Peer &peer,
                                         DataStream &vRecv) {
    uint8_t filter_type_ser;
    uint32_t start_height;
    BlockHash stop_hash;
 
    vRecv >> filter_type_ser >> start_height >> stop_hash;
 
    const BlockFilterType filter_type =
        static_cast<BlockFilterType>(filter_type_ser);
 
    const CBlockIndex *stop_index;
    BlockFilterIndex *filter_index;
    if (!PrepareBlockFilterRequest(node, peer, filter_type, start_height,
                                   stop_hash, MAX_GETCFILTERS_SIZE, stop_index,
                                   filter_index)) {
        return;
    }
 
    std::vector<BlockFilter> filters;
    if (!filter_index->LookupFilterRange(start_height, stop_index, filters)) {
        LogPrint(BCLog::NET,
                 "Failed to find block filter in index: filter_type=%s, "
                 "start_height=%d, stop_hash=%s\n",
                 BlockFilterTypeName(filter_type), start_height,
                 stop_hash.ToString());
        return;
    }
 
    for (const auto &filter : filters) {
        MakeAndPushMessage(node, NetMsgType::CFILTER, filter);
    }
}
 
void PeerManagerImpl::ProcessGetCFHeaders(CNode &node, Peer &peer,
                                          DataStream &vRecv) {
    uint8_t filter_type_ser;
    uint32_t start_height;
    BlockHash stop_hash;
 
    vRecv >> filter_type_ser >> start_height >> stop_hash;
 
    const BlockFilterType filter_type =
        static_cast<BlockFilterType>(filter_type_ser);
 
    const CBlockIndex *stop_index;
    BlockFilterIndex *filter_index;
    if (!PrepareBlockFilterRequest(node, peer, filter_type, start_height,
                                   stop_hash, MAX_GETCFHEADERS_SIZE, stop_index,
                                   filter_index)) {
        return;
    }
 
    uint256 prev_header;
    if (start_height > 0) {
        const CBlockIndex *const prev_block =
            stop_index->GetAncestor(static_cast<int>(start_height - 1));
        if (!filter_index->LookupFilterHeader(prev_block, prev_header)) {
            LogPrint(BCLog::NET,
                     "Failed to find block filter header in index: "
                     "filter_type=%s, block_hash=%s\n",
                     BlockFilterTypeName(filter_type),
                     prev_block->GetBlockHash().ToString());
            return;
        }
    }
 
    std::vector<uint256> filter_hashes;
    if (!filter_index->LookupFilterHashRange(start_height, stop_index,
                                             filter_hashes)) {
        LogPrint(BCLog::NET,
                 "Failed to find block filter hashes in index: filter_type=%s, "
                 "start_height=%d, stop_hash=%s\n",
                 BlockFilterTypeName(filter_type), start_height,
                 stop_hash.ToString());
        return;
    }
 
    MakeAndPushMessage(node, NetMsgType::CFHEADERS, filter_type_ser,
                       stop_index->GetBlockHash(), prev_header, filter_hashes);
}
 
void PeerManagerImpl::ProcessGetCFCheckPt(CNode &node, Peer &peer,
                                          DataStream &vRecv) {
    uint8_t filter_type_ser;
    BlockHash stop_hash;
 
    vRecv >> filter_type_ser >> stop_hash;
 
    const BlockFilterType filter_type =
        static_cast<BlockFilterType>(filter_type_ser);
 
    const CBlockIndex *stop_index;
    BlockFilterIndex *filter_index;
    if (!PrepareBlockFilterRequest(
            node, peer, filter_type, /*start_height=*/0, stop_hash,
            /*max_height_diff=*/std::numeric_limits<uint32_t>::max(),
            stop_index, filter_index)) {
        return;
    }
 
    std::vector<uint256> headers(stop_index->nHeight / CFCHECKPT_INTERVAL);
 
    // Populate headers.
    const CBlockIndex *block_index = stop_index;
    for (int i = headers.size() - 1; i >= 0; i--) {
        int height = (i + 1) * CFCHECKPT_INTERVAL;
        block_index = block_index->GetAncestor(height);
 
        if (!filter_index->LookupFilterHeader(block_index, headers[i])) {
            LogPrint(BCLog::NET,
                     "Failed to find block filter header in index: "
                     "filter_type=%s, block_hash=%s\n",
                     BlockFilterTypeName(filter_type),
                     block_index->GetBlockHash().ToString());
            return;
        }
    }
 
    MakeAndPushMessage(node, NetMsgType::CFCHECKPT, filter_type_ser,
                       stop_index->GetBlockHash(), headers);
}
 
bool IsAvalancheMessageType(const std::string &msg_type) {
    return msg_type == NetMsgType::AVAHELLO ||
           msg_type == NetMsgType::AVAPOLL ||
           msg_type == NetMsgType::AVARESPONSE ||
           msg_type == NetMsgType::AVAPROOF ||
           msg_type == NetMsgType::GETAVAADDR ||
           msg_type == NetMsgType::GETAVAPROOFS ||
           msg_type == NetMsgType::AVAPROOFS ||
           msg_type == NetMsgType::AVAPROOFSREQ;
}
 
uint32_t
PeerManagerImpl::GetAvalancheVoteForBlock(const BlockHash &hash) const {
    AssertLockHeld(cs_main);
 
    const CBlockIndex *pindex = m_chainman.m_blockman.LookupBlockIndex(hash);
 
    // Unknown block.
    if (!pindex) {
        return -1;
    }
 
    // Invalid block
    if (pindex->nStatus.isInvalid()) {
        return 1;
    }
 
    // Parked block
    if (pindex->nStatus.isOnParkedChain()) {
        return 2;
    }
 
    const CBlockIndex *pindexTip = m_chainman.ActiveChain().Tip();
    const CBlockIndex *pindexFork = LastCommonAncestor(pindex, pindexTip);
 
    // Active block.
    if (pindex == pindexFork) {
        return 0;
    }
 
    // Fork block.
    if (pindexFork != pindexTip) {
        return 3;
    }
 
    // Missing block data.
    if (!pindex->nStatus.hasData()) {
        return -2;
    }
 
    // This block is built on top of the tip, we have the data, it
    // is pending connection or rejection.
    return -3;
};
 
uint32_t
PeerManagerImpl::GetAvalancheVoteForTx(const avalanche::Processor &avalanche,
                                       const TxId &id) const {
    // Recently confirmed
    if (WITH_LOCK(m_recent_confirmed_transactions_mutex,
                  return m_recent_confirmed_transactions.contains(id))) {
        return 0;
    }
 
    CTransactionRef mempool_tx;
    {
        LOCK(::cs_main);
 
        // Invalid tx. m_recent_rejects needs cs_main
        if (m_recent_rejects.contains(id)) {
            return 1;
        }
 
        LOCK(m_mempool.cs);
 
        // Finalized
        if (m_mempool.isAvalancheFinalizedPreConsensus(id)) {
            return 0;
        }
 
        // Accepted in mempool
        if (auto iter = m_mempool.GetIter(id)) {
            mempool_tx = (**iter)->GetSharedTx();
        } else {
            // Conflicting tx
            if (m_mempool.withConflicting(
                    [&id](const TxConflicting &conflicting) {
                        return conflicting.HaveTx(id);
                    })) {
                return 2;
            }
 
            // Orphan tx
            if (m_mempool.withOrphanage([&id](const TxOrphanage &orphanage) {
                    return orphanage.HaveTx(id);
                })) {
                return -2;
            }
        }
    } // release cs_main and mempool.cs locks
 
    // isPolled() access the vote records, and should be accessed with cs_main
    // released.
    // If the tx is in the mempool...
    if (mempool_tx) {
        // ... and in the polled list
        if (avalanche.isPolled(mempool_tx)) {
            return 0;
        }
 
        // ... but not in the polled list
        return -3;
    }
 
    // Unknown tx
    return -1;
};
 
static uint32_t getAvalancheVoteForProof(const avalanche::Processor &avalanche,
                                         const avalanche::ProofId &id) {
    return avalanche.withPeerManager([&id](avalanche::PeerManager &pm) {
        // Rejected proof
        if (pm.isInvalid(id)) {
            return 1;
        }
 
        // The proof is actively bound to a peer
        if (pm.isBoundToPeer(id)) {
            return 0;
        }
 
        // Unknown proof
        if (!pm.exists(id)) {
            return -1;
        }
 
        // Immature proof
        if (pm.isImmature(id)) {
            return 2;
        }
 
        // Not immature, but in conflict with an actively bound proof
        if (pm.isInConflictingPool(id)) {
            return 3;
        }
 
        // The proof is known, not rejected, not immature, not a conflict, but
        // for some reason unbound. This should not happen if the above pools
        // are managed correctly, but added for robustness.
        return -2;
    });
};
 
void PeerManagerImpl::ProcessBlock(const Config &config, CNode &node,
                                   const std::shared_ptr<const CBlock> &block,
                                   bool force_processing,
                                   bool min_pow_checked) {
    bool new_block{false};
    m_chainman.ProcessNewBlock(block, force_processing, min_pow_checked,
                               &new_block, m_avalanche);
    if (new_block) {
        node.m_last_block_time = GetTime<std::chrono::seconds>();
        // In case this block came from a different peer than we requested
        // from, we can erase the block request now anyway (as we just stored
        // this block to disk).
        LOCK(cs_main);
        RemoveBlockRequest(block->GetHash(), std::nullopt);
    } else {
        LOCK(cs_main);
        mapBlockSource.erase(block->GetHash());
    }
}
 
void PeerManagerImpl::ProcessMessage(
    const Config &config, CNode &pfrom, const std::string &msg_type,
    DataStream &vRecv, const std::chrono::microseconds time_received,
    const std::atomic<bool> &interruptMsgProc) {
    AssertLockHeld(g_msgproc_mutex);
 
    LogPrint(BCLog::NETDEBUG, "received: %s (%u bytes) peer=%d\n",
             SanitizeString(msg_type), vRecv.size(), pfrom.GetId());
 
    PeerRef peer = GetPeerRef(pfrom.GetId());
    if (peer == nullptr) {
        return;
    }
 
    if (!m_avalanche && IsAvalancheMessageType(msg_type)) {
        LogPrint(BCLog::AVALANCHE,
                 "Avalanche is not initialized, ignoring %s message\n",
                 msg_type);
        return;
    }
 
    if (msg_type == NetMsgType::VERSION) {
        // Each connection can only send one version message
        if (pfrom.nVersion != 0) {
            LogPrint(BCLog::NET, "redundant version message from peer=%d\n",
                     pfrom.GetId());
            return;
        }
 
        int64_t nTime;
        CService addrMe;
        uint64_t nNonce = 1;
        ServiceFlags nServices;
        int nVersion;
        std::string cleanSubVer;
        int starting_height = -1;
        bool fRelay = true;
        uint64_t nExtraEntropy = 1;
 
        vRecv >> nVersion >> Using<CustomUintFormatter<8>>(nServices) >> nTime;
        if (nTime < 0) {
            nTime = 0;
        }
        // Ignore the addrMe service bits sent by the peer
        vRecv.ignore(8);
        vRecv >> WithParams(CNetAddr::V1, addrMe);
        if (!pfrom.IsInboundConn()) {
            m_addrman.SetServices(pfrom.addr, nServices);
        }
        if (pfrom.ExpectServicesFromConn() &&
            !HasAllDesirableServiceFlags(nServices)) {
            LogPrint(BCLog::NET,
                     "peer=%d does not offer the expected services "
                     "(%08x offered, %08x expected); disconnecting\n",
                     pfrom.GetId(), nServices,
                     GetDesirableServiceFlags(nServices));
            pfrom.fDisconnect = true;
            return;
        }
 
        if (pfrom.IsAvalancheOutboundConnection() &&
            !(nServices & NODE_AVALANCHE)) {
            LogPrint(
                BCLog::AVALANCHE,
                "peer=%d does not offer the avalanche service; disconnecting\n",
                pfrom.GetId());
            pfrom.fDisconnect = true;
            return;
        }
 
        if (nVersion < MIN_PEER_PROTO_VERSION) {
            // disconnect from peers older than this proto version
            LogPrint(BCLog::NET,
                     "peer=%d using obsolete version %i; disconnecting\n",
                     pfrom.GetId(), nVersion);
            pfrom.fDisconnect = true;
            return;
        }
 
        if (!vRecv.empty()) {
            // The version message includes information about the sending node
            // which we don't use:
            //   - 8 bytes (service bits)
            //   - 16 bytes (ipv6 address)
            //   - 2 bytes (port)
            vRecv.ignore(26);
            vRecv >> nNonce;
        }
        if (!vRecv.empty()) {
            std::string strSubVer;
            vRecv >> LIMITED_STRING(strSubVer, MAX_SUBVERSION_LENGTH);
            cleanSubVer = SanitizeString(strSubVer);
        }
        if (!vRecv.empty()) {
            vRecv >> starting_height;
        }
        if (!vRecv.empty()) {
            vRecv >> fRelay;
        }
        if (!vRecv.empty()) {
            vRecv >> nExtraEntropy;
        }
        // Disconnect if we connected to ourself
        if (pfrom.IsInboundConn() && !m_connman.CheckIncomingNonce(nNonce)) {
            LogPrintf("connected to self at %s, disconnecting\n",
                      pfrom.addr.ToStringAddrPort());
            pfrom.fDisconnect = true;
            return;
        }
 
        if (pfrom.IsInboundConn() && addrMe.IsRoutable()) {
            SeenLocal(addrMe);
        }
 
        // Inbound peers send us their version message when they connect.
        // We send our version message in response.
        if (pfrom.IsInboundConn()) {
            PushNodeVersion(config, pfrom, *peer);
        }
 
        // Change version
        const int greatest_common_version =
            std::min(nVersion, PROTOCOL_VERSION);
        pfrom.SetCommonVersion(greatest_common_version);
        pfrom.nVersion = nVersion;
 
        MakeAndPushMessage(pfrom, NetMsgType::VERACK);
 
        // Signal ADDRv2 support (BIP155).
        MakeAndPushMessage(pfrom, NetMsgType::SENDADDRV2);
 
        pfrom.m_has_all_wanted_services =
            HasAllDesirableServiceFlags(nServices);
        peer->m_their_services = nServices;
        pfrom.SetAddrLocal(addrMe);
        {
            LOCK(pfrom.m_subver_mutex);
            pfrom.cleanSubVer = cleanSubVer;
        }
        peer->m_starting_height = starting_height;
 
        // Only initialize the m_tx_relay data structure if:
        // - this isn't an outbound block-relay-only connection; and
        // - this isn't an outbound feeler connection, and
        // - fRelay=true or we're offering NODE_BLOOM to this peer
        //   (NODE_BLOOM means that the peer may turn on tx relay later)
        if (!pfrom.IsBlockOnlyConn() && !pfrom.IsFeelerConn() &&
            (fRelay || (peer->m_our_services & NODE_BLOOM))) {
            auto *const tx_relay = peer->SetTxRelay();
            {
                LOCK(tx_relay->m_bloom_filter_mutex);
                // set to true after we get the first filter* message
                tx_relay->m_relay_txs = fRelay;
            }
            if (fRelay) {
                pfrom.m_relays_txs = true;
            }
        }
 
        pfrom.nRemoteHostNonce = nNonce;
        pfrom.nRemoteExtraEntropy = nExtraEntropy;
 
        // Potentially mark this peer as a preferred download peer.
        {
            LOCK(cs_main);
            CNodeState *state = State(pfrom.GetId());
            state->fPreferredDownload =
                (!pfrom.IsInboundConn() ||
                 pfrom.HasPermission(NetPermissionFlags::NoBan)) &&
                !pfrom.IsAddrFetchConn() && CanServeBlocks(*peer);
            m_num_preferred_download_peers += state->fPreferredDownload;
        }
 
        // Attempt to initialize address relay for outbound peers and use result
        // to decide whether to send GETADDR, so that we don't send it to
        // inbound or outbound block-relay-only peers.
        bool send_getaddr{false};
        if (!pfrom.IsInboundConn()) {
            send_getaddr = SetupAddressRelay(pfrom, *peer);
        }
        if (send_getaddr) {
            // Do a one-time address fetch to help populate/update our addrman.
            // If we're starting up for the first time, our addrman may be
            // pretty empty, so this mechanism is important to help us connect
            // to the network.
            // We skip this for block-relay-only peers. We want to avoid
            // potentially leaking addr information and we do not want to
            // indicate to the peer that we will participate in addr relay.
            MakeAndPushMessage(pfrom, NetMsgType::GETADDR);
            peer->m_getaddr_sent = true;
            // When requesting a getaddr, accept an additional MAX_ADDR_TO_SEND
            // addresses in response (bypassing the
            // MAX_ADDR_PROCESSING_TOKEN_BUCKET limit).
            WITH_LOCK(peer->m_addr_token_bucket_mutex,
                      peer->m_addr_token_bucket += m_opts.max_addr_to_send);
        }
 
        if (!pfrom.IsInboundConn()) {
            // For non-inbound connections, we update the addrman to record
            // connection success so that addrman will have an up-to-date
            // notion of which peers are online and available.
            //
            // While we strive to not leak information about block-relay-only
            // connections via the addrman, not moving an address to the tried
            // table is also potentially detrimental because new-table entries
            // are subject to eviction in the event of addrman collisions.  We
            // mitigate the information-leak by never calling
            // AddrMan::Connected() on block-relay-only peers; see
            // FinalizeNode().
            //
            // This moves an address from New to Tried table in Addrman,
            // resolves tried-table collisions, etc.
            m_addrman.Good(pfrom.addr);
        }
 
        std::string remoteAddr;
        if (fLogIPs) {
            remoteAddr = ", peeraddr=" + pfrom.addr.ToStringAddrPort();
        }
 
        LogPrint(BCLog::NET,
                 "receive version message: [%s] %s: version %d, blocks=%d, "
                 "us=%s, txrelay=%d, peer=%d%s\n",
                 pfrom.addr.ToStringAddrPort(), cleanSubVer, pfrom.nVersion,
                 peer->m_starting_height, addrMe.ToStringAddrPort(), fRelay,
                 pfrom.GetId(), remoteAddr);
 
        int64_t currentTime = GetTime();
        int64_t nTimeOffset = nTime - currentTime;
        pfrom.nTimeOffset = nTimeOffset;
        if (nTime < int64_t(m_chainparams.GenesisBlock().nTime)) {
            // Ignore time offsets that are improbable (before the Genesis
            // block) and may underflow our adjusted time.
            Misbehaving(*peer, "Ignoring invalid timestamp in version message");
        } else if (!pfrom.IsInboundConn()) {
            // Don't use timedata samples from inbound peers to make it
            // harder for others to tamper with our adjusted time.
            AddTimeData(pfrom.addr, nTimeOffset);
        }
 
        // Feeler connections exist only to verify if address is online.
        if (pfrom.IsFeelerConn()) {
            LogPrint(BCLog::NET,
                     "feeler connection completed peer=%d; disconnecting\n",
                     pfrom.GetId());
            pfrom.fDisconnect = true;
        }
        return;
    }
 
    if (pfrom.nVersion == 0) {
        // Must have a version message before anything else
        Misbehaving(*peer, "non-version message before version handshake");
        return;
    }
 
    if (msg_type == NetMsgType::VERACK) {
        if (pfrom.fSuccessfullyConnected) {
            LogPrint(BCLog::NET,
                     "ignoring redundant verack message from peer=%d\n",
                     pfrom.GetId());
            return;
        }
 
        if (!pfrom.IsInboundConn()) {
            LogPrintf("New outbound peer connected: version: %d, blocks=%d, "
                      "peer=%d%s (%s)\n",
                      pfrom.nVersion.load(), peer->m_starting_height,
                      pfrom.GetId(),
                      (fLogIPs ? strprintf(", peeraddr=%s",
                                           pfrom.addr.ToStringAddrPort())
                               : ""),
                      pfrom.ConnectionTypeAsString());
        }
 
        if (pfrom.GetCommonVersion() >= SHORT_IDS_BLOCKS_VERSION) {
            // Tell our peer we are willing to provide version 1
            // cmpctblocks. However, we do not request new block announcements
            // using cmpctblock messages. We send this to non-NODE NETWORK peers
            // as well, because they may wish to request compact blocks from us.
            MakeAndPushMessage(pfrom, NetMsgType::SENDCMPCT,
                               /*high_bandwidth=*/false,
                               /*version=*/CMPCTBLOCKS_VERSION);
        }
 
        if (m_avalanche) {
            if (m_avalanche->sendHello(&pfrom)) {
                auto localProof = m_avalanche->getLocalProof();
 
                if (localProof) {
                    AddKnownProof(*peer, localProof->getId());
                    // Add our proof id to the list or the recently announced
                    // proof INVs to this peer. This is used for filtering which
                    // INV can be requested for download.
                    peer->m_proof_relay->m_recently_announced_proofs.insert(
                        localProof->getId());
                }
            }
        }
 
        if (auto tx_relay = peer->GetTxRelay()) {
            // `TxRelay::m_tx_inventory_to_send` must be empty before the
            // version handshake is completed as
            // `TxRelay::m_next_inv_send_time` is first initialised in
            // `SendMessages` after the verack is received. Any transactions
            // received during the version handshake would otherwise
            // immediately be advertised without random delay, potentially
            // leaking the time of arrival to a spy.
            Assume(WITH_LOCK(tx_relay->m_tx_inventory_mutex,
                             return tx_relay->m_tx_inventory_to_send.empty() &&
                                    tx_relay->m_next_inv_send_time == 0s));
        }
 
        pfrom.fSuccessfullyConnected = true;
        return;
    }
 
    if (!pfrom.fSuccessfullyConnected) {
        // Must have a verack message before anything else
        Misbehaving(*peer, "non-verack message before version handshake");
        return;
    }
 
    if (msg_type == NetMsgType::ADDR || msg_type == NetMsgType::ADDRV2) {
        const auto ser_params{
            msg_type == NetMsgType::ADDRV2
                ?
                // Set V2 param so that the CNetAddr and CAddress unserialize
                // methods know that an address in v2 format is coming.
                CAddress::V2_NETWORK
                : CAddress::V1_NETWORK,
        };
 
        std::vector<CAddress> vAddr;
 
        vRecv >> WithParams(ser_params, vAddr);
 
        if (!SetupAddressRelay(pfrom, *peer)) {
            LogPrint(BCLog::NET, "ignoring %s message from %s peer=%d\n",
                     msg_type, pfrom.ConnectionTypeAsString(), pfrom.GetId());
            return;
        }
 
        if (vAddr.size() > m_opts.max_addr_to_send) {
            Misbehaving(*peer, strprintf("%s message size = %u", msg_type,
                                         vAddr.size()));
            return;
        }
 
        // Store the new addresses
        std::vector<CAddress> vAddrOk;
        const auto current_a_time{Now<NodeSeconds>()};
 
        // Update/increment addr rate limiting bucket.
        const auto current_time = GetTime<std::chrono::microseconds>();
        {
            LOCK(peer->m_addr_token_bucket_mutex);
            if (peer->m_addr_token_bucket < MAX_ADDR_PROCESSING_TOKEN_BUCKET) {
                // Don't increment bucket if it's already full
                const auto time_diff =
                    std::max(current_time - peer->m_addr_token_timestamp, 0us);
                const double increment =
                    CountSecondsDouble(time_diff) * MAX_ADDR_RATE_PER_SECOND;
                peer->m_addr_token_bucket =
                    std::min<double>(peer->m_addr_token_bucket + increment,
                                     MAX_ADDR_PROCESSING_TOKEN_BUCKET);
            }
        }
        peer->m_addr_token_timestamp = current_time;
 
        const bool rate_limited =
            !pfrom.HasPermission(NetPermissionFlags::Addr);
        uint64_t num_proc = 0;
        uint64_t num_rate_limit = 0;
        Shuffle(vAddr.begin(), vAddr.end(), m_rng);
        for (CAddress &addr : vAddr) {
            if (interruptMsgProc) {
                return;
            }
 
            {
                LOCK(peer->m_addr_token_bucket_mutex);
                // Apply rate limiting.
                if (peer->m_addr_token_bucket < 1.0) {
                    if (rate_limited) {
                        ++num_rate_limit;
                        continue;
                    }
                } else {
                    peer->m_addr_token_bucket -= 1.0;
                }
            }
 
            // We only bother storing full nodes, though this may include things
            // which we would not make an outbound connection to, in part
            // because we may make feeler connections to them.
            if (!MayHaveUsefulAddressDB(addr.nServices) &&
                !HasAllDesirableServiceFlags(addr.nServices)) {
                continue;
            }
 
            if (addr.nTime <= NodeSeconds{100000000s} ||
                addr.nTime > current_a_time + 10min) {
                addr.nTime = current_a_time - 5 * 24h;
            }
            AddAddressKnown(*peer, addr);
            if (m_banman &&
                (m_banman->IsDiscouraged(addr) || m_banman->IsBanned(addr))) {
                // Do not process banned/discouraged addresses beyond
                // remembering we received them
                continue;
            }
            ++num_proc;
            bool fReachable = IsReachable(addr);
            if (addr.nTime > current_a_time - 10min && !peer->m_getaddr_sent &&
                vAddr.size() <= 10 && addr.IsRoutable()) {
                // Relay to a limited number of other nodes
                RelayAddress(pfrom.GetId(), addr, fReachable);
            }
            // Do not store addresses outside our network
            if (fReachable) {
                vAddrOk.push_back(addr);
            }
        }
        peer->m_addr_processed += num_proc;
        peer->m_addr_rate_limited += num_rate_limit;
        LogPrint(BCLog::NET,
                 "Received addr: %u addresses (%u processed, %u rate-limited) "
                 "from peer=%d\n",
                 vAddr.size(), num_proc, num_rate_limit, pfrom.GetId());
 
        m_addrman.Add(vAddrOk, pfrom.addr, 2h);
        if (vAddr.size() < 1000) {
            peer->m_getaddr_sent = false;
        }
 
        // AddrFetch: Require multiple addresses to avoid disconnecting on
        // self-announcements
        if (pfrom.IsAddrFetchConn() && vAddr.size() > 1) {
            LogPrint(BCLog::NET,
                     "addrfetch connection completed peer=%d; disconnecting\n",
                     pfrom.GetId());
            pfrom.fDisconnect = true;
        }
        return;
    }
 
    if (msg_type == NetMsgType::SENDADDRV2) {
        peer->m_wants_addrv2 = true;
        return;
    }
 
    if (msg_type == NetMsgType::SENDHEADERS) {
        peer->m_prefers_headers = true;
        return;
    }
 
    if (msg_type == NetMsgType::SENDCMPCT) {
        bool sendcmpct_hb{false};
        uint64_t sendcmpct_version{0};
        vRecv >> sendcmpct_hb >> sendcmpct_version;
 
        if (sendcmpct_version != CMPCTBLOCKS_VERSION) {
            return;
        }
 
        LOCK(cs_main);
        CNodeState *nodestate = State(pfrom.GetId());
        nodestate->m_provides_cmpctblocks = true;
        nodestate->m_requested_hb_cmpctblocks = sendcmpct_hb;
        // save whether peer selects us as BIP152 high-bandwidth peer
        // (receiving sendcmpct(1) signals high-bandwidth,
        // sendcmpct(0) low-bandwidth)
        pfrom.m_bip152_highbandwidth_from = sendcmpct_hb;
        return;
    }
 
    if (msg_type == NetMsgType::INV) {
        std::vector<CInv> vInv;
        vRecv >> vInv;
        if (vInv.size() > MAX_INV_SZ) {
            Misbehaving(*peer, strprintf("inv message size = %u", vInv.size()));
            return;
        }
 
        const bool reject_tx_invs{RejectIncomingTxs(pfrom)};
 
        const auto current_time{GetTime<std::chrono::microseconds>()};
        std::optional<BlockHash> best_block;
 
        auto logInv = [&](const CInv &inv, bool fAlreadyHave) {
            LogPrint(BCLog::NET, "got inv: %s  %s peer=%d\n", inv.ToString(),
                     fAlreadyHave ? "have" : "new", pfrom.GetId());
        };
 
        for (CInv &inv : vInv) {
            if (interruptMsgProc) {
                return;
            }
 
            if (inv.IsMsgStakeContender()) {
                // Ignore invs with stake contenders. This type is only used for
                // polling.
                continue;
            }
 
            if (inv.IsMsgBlk()) {
                LOCK(cs_main);
                const bool fAlreadyHave = AlreadyHaveBlock(BlockHash(inv.hash));
                logInv(inv, fAlreadyHave);
 
                BlockHash hash{inv.hash};
                UpdateBlockAvailability(pfrom.GetId(), hash);
                if (!fAlreadyHave && !m_chainman.m_blockman.LoadingBlocks() &&
                    !IsBlockRequested(hash)) {
                    // Headers-first is the primary method of announcement on
                    // the network. If a node fell back to sending blocks by
                    // inv, it may be for a re-org, or because we haven't
                    // completed initial headers sync. The final block hash
                    // provided should be the highest, so send a getheaders and
                    // then fetch the blocks we need to catch up.
                    best_block = std::move(hash);
                }
 
                continue;
            }
 
            if (inv.IsMsgProof()) {
                if (!m_avalanche) {
                    continue;
                }
                const avalanche::ProofId proofid(inv.hash);
                const bool fAlreadyHave = AlreadyHaveProof(proofid);
                logInv(inv, fAlreadyHave);
                AddKnownProof(*peer, proofid);
 
                if (!fAlreadyHave && m_avalanche &&
                    !m_chainman.IsInitialBlockDownload()) {
                    const bool preferred = isPreferredDownloadPeer(pfrom);
 
                    LOCK(cs_proofrequest);
                    AddProofAnnouncement(pfrom, proofid, current_time,
                                         preferred);
                }
                continue;
            }
 
            if (inv.IsMsgTx()) {
                LOCK(cs_main);
                const TxId txid(inv.hash);
                const bool fAlreadyHave =
                    AlreadyHaveTx(txid, /*include_reconsiderable=*/true);
                logInv(inv, fAlreadyHave);
 
                AddKnownTx(*peer, txid);
                if (reject_tx_invs) {
                    LogPrint(BCLog::NET,
                             "transaction (%s) inv sent in violation of "
                             "protocol, disconnecting peer=%d\n",
                             txid.ToString(), pfrom.GetId());
                    pfrom.fDisconnect = true;
                    return;
                } else if (!fAlreadyHave &&
                           !m_chainman.IsInitialBlockDownload()) {
                    AddTxAnnouncement(pfrom, txid, current_time);
                }
 
                continue;
            }
 
            LogPrint(BCLog::NET,
                     "Unknown inv type \"%s\" received from peer=%d\n",
                     inv.ToString(), pfrom.GetId());
        }
 
        if (best_block) {
            // If we haven't started initial headers-sync with this peer, then
            // consider sending a getheaders now. On initial startup, there's a
            // reliability vs bandwidth tradeoff, where we are only trying to do
            // initial headers sync with one peer at a time, with a long
            // timeout (at which point, if the sync hasn't completed, we will
            // disconnect the peer and then choose another). In the meantime,
            // as new blocks are found, we are willing to add one new peer per
            // block to sync with as well, to sync quicker in the case where
            // our initial peer is unresponsive (but less bandwidth than we'd
            // use if we turned on sync with all peers).
            LOCK(::cs_main);
            CNodeState &state{*Assert(State(pfrom.GetId()))};
            if (state.fSyncStarted ||
                (!peer->m_inv_triggered_getheaders_before_sync &&
                 *best_block != m_last_block_inv_triggering_headers_sync)) {
                if (MaybeSendGetHeaders(
                        pfrom, GetLocator(m_chainman.m_best_header), *peer)) {
                    LogPrint(BCLog::NET, "getheaders (%d) %s to peer=%d\n",
                             m_chainman.m_best_header->nHeight,
                             best_block->ToString(), pfrom.GetId());
                }
                if (!state.fSyncStarted) {
                    peer->m_inv_triggered_getheaders_before_sync = true;
                    // Update the last block hash that triggered a new headers
                    // sync, so that we don't turn on headers sync with more
                    // than 1 new peer every new block.
                    m_last_block_inv_triggering_headers_sync = *best_block;
                }
            }
        }
 
        return;
    }
 
    if (msg_type == NetMsgType::GETDATA) {
        std::vector<CInv> vInv;
        vRecv >> vInv;
        if (vInv.size() > MAX_INV_SZ) {
            Misbehaving(*peer,
                        strprintf("getdata message size = %u", vInv.size()));
            return;
        }
 
        LogPrint(BCLog::NET, "received getdata (%u invsz) peer=%d\n",
                 vInv.size(), pfrom.GetId());
 
        if (vInv.size() > 0) {
            LogPrint(BCLog::NET, "received getdata for: %s peer=%d\n",
                     vInv[0].ToString(), pfrom.GetId());
        }
 
        {
            LOCK(peer->m_getdata_requests_mutex);
            peer->m_getdata_requests.insert(peer->m_getdata_requests.end(),
                                            vInv.begin(), vInv.end());
            ProcessGetData(config, pfrom, *peer, interruptMsgProc);
        }
 
        return;
    }
 
    if (msg_type == NetMsgType::GETBLOCKS) {
        CBlockLocator locator;
        uint256 hashStop;
        vRecv >> locator >> hashStop;
 
        if (locator.vHave.size() > MAX_LOCATOR_SZ) {
            LogPrint(BCLog::NET,
                     "getblocks locator size %lld > %d, disconnect peer=%d\n",
                     locator.vHave.size(), MAX_LOCATOR_SZ, pfrom.GetId());
            pfrom.fDisconnect = true;
            return;
        }
 
        // We might have announced the currently-being-connected tip using a
        // compact block, which resulted in the peer sending a getblocks
        // request, which we would otherwise respond to without the new block.
        // To avoid this situation we simply verify that we are on our best
        // known chain now. This is super overkill, but we handle it better
        // for getheaders requests, and there are no known nodes which support
        // compact blocks but still use getblocks to request blocks.
        {
            std::shared_ptr<const CBlock> a_recent_block;
            {
                LOCK(m_most_recent_block_mutex);
                a_recent_block = m_most_recent_block;
            }
            BlockValidationState state;
            if (!m_chainman.ActiveChainstate().ActivateBestChain(
                    state, a_recent_block, m_avalanche)) {
                LogPrint(BCLog::NET, "failed to activate chain (%s)\n",
                         state.ToString());
            }
        }
 
        LOCK(cs_main);
 
        // Find the last block the caller has in the main chain
        const CBlockIndex *pindex =
            m_chainman.ActiveChainstate().FindForkInGlobalIndex(locator);
 
        // Send the rest of the chain
        if (pindex) {
            pindex = m_chainman.ActiveChain().Next(pindex);
        }
        int nLimit = 500;
        LogPrint(BCLog::NET, "getblocks %d to %s limit %d from peer=%d\n",
                 (pindex ? pindex->nHeight : -1),
                 hashStop.IsNull() ? "end" : hashStop.ToString(), nLimit,
                 pfrom.GetId());
        for (; pindex; pindex = m_chainman.ActiveChain().Next(pindex)) {
            if (pindex->GetBlockHash() == hashStop) {
                LogPrint(BCLog::NET, "  getblocks stopping at %d %s\n",
                         pindex->nHeight, pindex->GetBlockHash().ToString());
                break;
            }
            // If pruning, don't inv blocks unless we have on disk and are
            // likely to still have for some reasonable time window (1 hour)
            // that block relay might require.
            const int nPrunedBlocksLikelyToHave =
                MIN_BLOCKS_TO_KEEP -
                3600 / m_chainparams.GetConsensus().nPowTargetSpacing;
            if (m_chainman.m_blockman.IsPruneMode() &&
                (!pindex->nStatus.hasData() ||
                 pindex->nHeight <= m_chainman.ActiveChain().Tip()->nHeight -
                                        nPrunedBlocksLikelyToHave)) {
                LogPrint(
                    BCLog::NET,
                    " getblocks stopping, pruned or too old block at %d %s\n",
                    pindex->nHeight, pindex->GetBlockHash().ToString());
                break;
            }
            WITH_LOCK(
                peer->m_block_inv_mutex,
                peer->m_blocks_for_inv_relay.push_back(pindex->GetBlockHash()));
            if (--nLimit <= 0) {
                // When this block is requested, we'll send an inv that'll
                // trigger the peer to getblocks the next batch of inventory.
                LogPrint(BCLog::NET, "  getblocks stopping at limit %d %s\n",
                         pindex->nHeight, pindex->GetBlockHash().ToString());
                WITH_LOCK(peer->m_block_inv_mutex, {
                    peer->m_continuation_block = pindex->GetBlockHash();
                });
                break;
            }
        }
        return;
    }
 
    if (msg_type == NetMsgType::GETBLOCKTXN) {
        BlockTransactionsRequest req;
        vRecv >> req;
 
        std::shared_ptr<const CBlock> recent_block;
        {
            LOCK(m_most_recent_block_mutex);
            if (m_most_recent_block_hash == req.blockhash) {
                recent_block = m_most_recent_block;
            }
            // Unlock m_most_recent_block_mutex to avoid cs_main lock inversion
        }
        if (recent_block) {
            SendBlockTransactions(pfrom, *peer, *recent_block, req);
            return;
        }
 
        FlatFilePos block_pos{};
        {
            LOCK(cs_main);
 
            const CBlockIndex *pindex =
                m_chainman.m_blockman.LookupBlockIndex(req.blockhash);
            if (!pindex || !pindex->nStatus.hasData()) {
                LogPrint(
                    BCLog::NET,
                    "Peer %d sent us a getblocktxn for a block we don't have\n",
                    pfrom.GetId());
                return;
            }
 
            if (pindex->nHeight >=
                m_chainman.ActiveChain().Height() - MAX_BLOCKTXN_DEPTH) {
                block_pos = pindex->GetBlockPos();
            }
        }
 
        if (!block_pos.IsNull()) {
            CBlock block;
            const bool ret{m_chainman.m_blockman.ReadBlock(block, block_pos)};
            // If height is above MAX_BLOCKTXN_DEPTH then this block cannot get
            // pruned after we release cs_main above, so this read should never
            // fail.
            assert(ret);
 
            SendBlockTransactions(pfrom, *peer, block, req);
            return;
        }
 
        // If an older block is requested (should never happen in practice,
        // but can happen in tests) send a block response instead of a
        // blocktxn response. Sending a full block response instead of a
        // small blocktxn response is preferable in the case where a peer
        // might maliciously send lots of getblocktxn requests to trigger
        // expensive disk reads, because it will require the peer to
        // actually receive all the data read from disk over the network.
        LogPrint(BCLog::NET,
                 "Peer %d sent us a getblocktxn for a block > %i deep\n",
                 pfrom.GetId(), MAX_BLOCKTXN_DEPTH);
        CInv inv;
        inv.type = MSG_BLOCK;
        inv.hash = req.blockhash;
        WITH_LOCK(peer->m_getdata_requests_mutex,
                  peer->m_getdata_requests.push_back(inv));
        // The message processing loop will go around again (without pausing)
        // and we'll respond then (without cs_main)
        return;
    }
 
    if (msg_type == NetMsgType::GETHEADERS) {
        CBlockLocator locator;
        BlockHash hashStop;
        vRecv >> locator >> hashStop;
 
        if (locator.vHave.size() > MAX_LOCATOR_SZ) {
            LogPrint(BCLog::NET,
                     "getheaders locator size %lld > %d, disconnect peer=%d\n",
                     locator.vHave.size(), MAX_LOCATOR_SZ, pfrom.GetId());
            pfrom.fDisconnect = true;
            return;
        }
 
        if (m_chainman.m_blockman.LoadingBlocks()) {
            LogPrint(
                BCLog::NET,
                "Ignoring getheaders from peer=%d while importing/reindexing\n",
                pfrom.GetId());
            return;
        }
 
        LOCK(cs_main);
 
        // Note that if we were to be on a chain that forks from the
        // checkpointed chain, then serving those headers to a peer that has
        // seen the checkpointed chain would cause that peer to disconnect us.
        // Requiring that our chainwork exceed the minimum chainwork is a
        // protection against being fed a bogus chain when we started up for
        // the first time and getting partitioned off the honest network for
        // serving that chain to others.
        if (m_chainman.ActiveTip() == nullptr ||
            (m_chainman.ActiveTip()->nChainWork <
                 m_chainman.MinimumChainWork() &&
             !pfrom.HasPermission(NetPermissionFlags::Download))) {
            LogPrint(BCLog::NET,
                     "Ignoring getheaders from peer=%d because active chain "
                     "has too little work; sending empty response\n",
                     pfrom.GetId());
            // Just respond with an empty headers message, to tell the peer to
            // go away but not treat us as unresponsive.
            MakeAndPushMessage(pfrom, NetMsgType::HEADERS,
                               std::vector<CBlock>());
            return;
        }
 
        CNodeState *nodestate = State(pfrom.GetId());
        const CBlockIndex *pindex = nullptr;
        if (locator.IsNull()) {
            // If locator is null, return the hashStop block
            pindex = m_chainman.m_blockman.LookupBlockIndex(hashStop);
            if (!pindex) {
                return;
            }
 
            if (!BlockRequestAllowed(pindex)) {
                LogPrint(BCLog::NET,
                         "%s: ignoring request from peer=%i for old block "
                         "header that isn't in the main chain\n",
                         __func__, pfrom.GetId());
                return;
            }
        } else {
            // Find the last block the caller has in the main chain
            pindex =
                m_chainman.ActiveChainstate().FindForkInGlobalIndex(locator);
            if (pindex) {
                pindex = m_chainman.ActiveChain().Next(pindex);
            }
        }
 
        // we must use CBlocks, as CBlockHeaders won't include the 0x00 nTx
        // count at the end
        std::vector<CBlock> vHeaders;
        int nLimit = MAX_HEADERS_RESULTS;
        LogPrint(BCLog::NET, "getheaders %d to %s from peer=%d\n",
                 (pindex ? pindex->nHeight : -1),
                 hashStop.IsNull() ? "end" : hashStop.ToString(),
                 pfrom.GetId());
        for (; pindex; pindex = m_chainman.ActiveChain().Next(pindex)) {
            vHeaders.push_back(pindex->GetBlockHeader());
            if (--nLimit <= 0 || pindex->GetBlockHash() == hashStop) {
                break;
            }
        }
        // pindex can be nullptr either if we sent
        // m_chainman.ActiveChain().Tip() OR if our peer has
        // m_chainman.ActiveChain().Tip() (and thus we are sending an empty
        // headers message). In both cases it's safe to update
        // pindexBestHeaderSent to be our tip.
        //
        // It is important that we simply reset the BestHeaderSent value here,
        // and not max(BestHeaderSent, newHeaderSent). We might have announced
        // the currently-being-connected tip using a compact block, which
        // resulted in the peer sending a headers request, which we respond to
        // without the new block. By resetting the BestHeaderSent, we ensure we
        // will re-announce the new block via headers (or compact blocks again)
        // in the SendMessages logic.
        nodestate->pindexBestHeaderSent =
            pindex ? pindex : m_chainman.ActiveChain().Tip();
        MakeAndPushMessage(pfrom, NetMsgType::HEADERS, vHeaders);
        return;
    }
 
    if (msg_type == NetMsgType::TX) {
        if (RejectIncomingTxs(pfrom)) {
            LogPrint(BCLog::NET,
                     "transaction sent in violation of protocol peer=%d\n",
                     pfrom.GetId());
            pfrom.fDisconnect = true;
            return;
        }
 
        // Stop processing the transaction early if we are still in IBD since we
        // don't have enough information to validate it yet. Sending unsolicited
        // transactions is not considered a protocol violation, so don't punish
        // the peer.
        if (m_chainman.IsInitialBlockDownload()) {
            return;
        }
 
        CTransactionRef ptx;
        vRecv >> ptx;
        const CTransaction &tx = *ptx;
        const TxId &txid = tx.GetId();
        AddKnownTx(*peer, txid);
 
        {
            LOCK(cs_main);
 
            m_txrequest.ReceivedResponse(pfrom.GetId(), txid);
 
            if (AlreadyHaveTx(txid, /*include_reconsiderable=*/true)) {
                if (pfrom.HasPermission(NetPermissionFlags::ForceRelay)) {
                    // Always relay transactions received from peers with
                    // forcerelay permission, even if they were already in the
                    // mempool, allowing the node to function as a gateway for
                    // nodes hidden behind it.
                    if (!m_mempool.exists(tx.GetId())) {
                        LogPrintf(
                            "Not relaying non-mempool transaction %s from "
                            "forcerelay peer=%d\n",
                            tx.GetId().ToString(), pfrom.GetId());
                    } else {
                        LogPrintf("Force relaying tx %s from peer=%d\n",
                                  tx.GetId().ToString(), pfrom.GetId());
                        RelayTransaction(tx.GetId());
                    }
                }
 
                if (m_recent_rejects_package_reconsiderable.contains(txid)) {
                    // When a transaction is already in
                    // m_recent_rejects_package_reconsiderable, we shouldn't
                    // submit it by itself again. However, look for a matching
                    // child in the orphanage, as it is possible that they
                    // succeed as a package.
                    LogPrint(
                        BCLog::TXPACKAGES,
                        "found tx %s in reconsiderable rejects, looking for "
                        "child in orphanage\n",
                        txid.ToString());
                    if (auto package_to_validate{
                            Find1P1CPackage(ptx, pfrom.GetId())}) {
                        const auto package_result{ProcessNewPackage(
                            m_chainman.ActiveChainstate(), m_mempool,
                            package_to_validate->m_txns,
                            /*test_accept=*/false)};
                        LogPrint(BCLog::TXPACKAGES,
                                 "package evaluation for %s: %s (%s)\n",
                                 package_to_validate->ToString(),
                                 package_result.m_state.IsValid()
                                     ? "package accepted"
                                     : "package rejected",
                                 package_result.m_state.ToString());
                        ProcessPackageResult(package_to_validate.value(),
                                             package_result);
                    }
                }
                // If a tx is detected by m_recent_rejects it is ignored.
                // Because we haven't submitted the tx to our mempool, we won't
                // have computed a DoS score for it or determined exactly why we
                // consider it invalid.
                //
                // This means we won't penalize any peer subsequently relaying a
                // DoSy tx (even if we penalized the first peer who gave it to
                // us) because we have to account for m_recent_rejects showing
                // false positives. In other words, we shouldn't penalize a peer
                // if we aren't *sure* they submitted a DoSy tx.
                //
                // Note that m_recent_rejects doesn't just record DoSy or
                // invalid transactions, but any tx not accepted by the mempool,
                // which may be due to node policy (vs. consensus). So we can't
                // blanket penalize a peer simply for relaying a tx that our
                // m_recent_rejects has caught, regardless of false positives.
                return;
            }
 
            const MempoolAcceptResult result =
                m_chainman.ProcessTransaction(ptx);
            const TxValidationState &state = result.m_state;
 
            if (result.m_result_type ==
                MempoolAcceptResult::ResultType::VALID) {
                ProcessValidTx(pfrom.GetId(), ptx);
                pfrom.m_last_tx_time = GetTime<std::chrono::seconds>();
            } else if (state.GetResult() ==
                       TxValidationResult::TX_MISSING_INPUTS) {
                // It may be the case that the orphans parents have all been
                // rejected.
                bool fRejectedParents = false;
 
                // Deduplicate parent txids, so that we don't have to loop over
                // the same parent txid more than once down below.
                std::vector<TxId> unique_parents;
                unique_parents.reserve(tx.vin.size());
                for (const CTxIn &txin : tx.vin) {
                    // We start with all parents, and then remove duplicates
                    // below.
                    unique_parents.push_back(txin.prevout.GetTxId());
                }
                std::sort(unique_parents.begin(), unique_parents.end());
                unique_parents.erase(
                    std::unique(unique_parents.begin(), unique_parents.end()),
                    unique_parents.end());
 
                // Distinguish between parents in m_recent_rejects and
                // m_recent_rejects_package_reconsiderable. We can tolerate
                // having up to 1 parent in
                // m_recent_rejects_package_reconsiderable since we submit 1p1c
                // packages. However, fail immediately if any are in
                // m_recent_rejects.
                std::optional<TxId> rejected_parent_reconsiderable;
                for (const TxId &parent_txid : unique_parents) {
                    if (m_recent_rejects.contains(parent_txid)) {
                        fRejectedParents = true;
                        break;
                    }
 
                    if (m_recent_rejects_package_reconsiderable.contains(
                            parent_txid) &&
                        !m_mempool.exists(parent_txid)) {
                        // More than 1 parent in
                        // m_recent_rejects_package_reconsiderable:
                        // 1p1c will not be sufficient to accept this package,
                        // so just give up here.
                        if (rejected_parent_reconsiderable.has_value()) {
                            fRejectedParents = true;
                            break;
                        }
                        rejected_parent_reconsiderable = parent_txid;
                    }
                }
                if (!fRejectedParents) {
                    const auto current_time{
                        GetTime<std::chrono::microseconds>()};
 
                    for (const TxId &parent_txid : unique_parents) {
                        // FIXME: MSG_TX should use a TxHash, not a TxId.
                        AddKnownTx(*peer, parent_txid);
                        // Exclude m_recent_rejects_package_reconsiderable: the
                        // missing parent may have been previously rejected for
                        // being too low feerate. This orphan might CPFP it.
                        if (!AlreadyHaveTx(parent_txid,
                                           /*include_reconsiderable=*/false)) {
                            AddTxAnnouncement(pfrom, parent_txid, current_time);
                        }
                    }
 
                    // NO_THREAD_SAFETY_ANALYSIS because we can't annotate for
                    // g_msgproc_mutex
                    if (unsigned int nEvicted =
                            m_mempool.withOrphanage(
                                [&](TxOrphanage &orphanage)
                                    NO_THREAD_SAFETY_ANALYSIS {
                                        if (orphanage.AddTx(ptx,
                                                            pfrom.GetId())) {
                                            AddToCompactExtraTransactions(ptx);
                                        }
                                        return orphanage.LimitTxs(
                                            m_opts.max_orphan_txs, m_rng);
                                    }) > 0) {
                        LogPrint(BCLog::TXPACKAGES,
                                 "orphanage overflow, removed %u tx\n",
                                 nEvicted);
                    }
 
                    // Once added to the orphan pool, a tx is considered
                    // AlreadyHave, and we shouldn't request it anymore.
                    m_txrequest.ForgetInvId(tx.GetId());
 
                } else {
                    LogPrint(BCLog::MEMPOOL,
                             "not keeping orphan with rejected parents %s\n",
                             tx.GetId().ToString());
                    // We will continue to reject this tx since it has rejected
                    // parents so avoid re-requesting it from other peers.
                    m_recent_rejects.insert(tx.GetId());
                    m_txrequest.ForgetInvId(tx.GetId());
                }
            }
            if (state.IsInvalid()) {
                ProcessInvalidTx(pfrom.GetId(), ptx, state,
                                 /*maybe_add_extra_compact_tx=*/true);
            }
            // When a transaction fails for TX_PACKAGE_RECONSIDERABLE, look for
            // a matching child in the orphanage, as it is possible that they
            // succeed as a package.
            if (state.GetResult() ==
                TxValidationResult::TX_PACKAGE_RECONSIDERABLE) {
                LogPrint(
                    BCLog::TXPACKAGES,
                    "tx %s failed but reconsiderable, looking for child in "
                    "orphanage\n",
                    txid.ToString());
                if (auto package_to_validate{
                        Find1P1CPackage(ptx, pfrom.GetId())}) {
                    const auto package_result{ProcessNewPackage(
                        m_chainman.ActiveChainstate(), m_mempool,
                        package_to_validate->m_txns, /*test_accept=*/false)};
                    LogPrint(BCLog::TXPACKAGES,
                             "package evaluation for %s: %s (%s)\n",
                             package_to_validate->ToString(),
                             package_result.m_state.IsValid()
                                 ? "package accepted"
                                 : "package rejected",
                             package_result.m_state.ToString());
                    ProcessPackageResult(package_to_validate.value(),
                                         package_result);
                }
            }
 
            if (state.GetResult() ==
                TxValidationResult::TX_AVALANCHE_RECONSIDERABLE) {
                // Once added to the conflicting pool, a tx is considered
                // AlreadyHave, and we shouldn't request it anymore.
                m_txrequest.ForgetInvId(tx.GetId());
 
                unsigned int nEvicted{0};
                // NO_THREAD_SAFETY_ANALYSIS because of g_msgproc_mutex required
                // in the lambda for m_rng
                m_mempool.withConflicting(
                    [&](TxConflicting &conflicting) NO_THREAD_SAFETY_ANALYSIS {
                        conflicting.AddTx(ptx, pfrom.GetId());
                        nEvicted = conflicting.LimitTxs(
                            m_opts.max_conflicting_txs, m_rng);
                    });
 
                if (nEvicted > 0) {
                    LogPrint(BCLog::TXPACKAGES,
                             "conflicting pool overflow, removed %u tx\n",
                             nEvicted);
                }
            }
        } // Release cs_main
 
        return;
    }
 
    if (msg_type == NetMsgType::CMPCTBLOCK) {
        // Ignore cmpctblock received while importing
        if (m_chainman.m_blockman.LoadingBlocks()) {
            LogPrint(BCLog::NET,
                     "Unexpected cmpctblock message received from peer %d\n",
                     pfrom.GetId());
            return;
        }
 
        CBlockHeaderAndShortTxIDs cmpctblock;
        try {
            vRecv >> cmpctblock;
        } catch (std::ios_base::failure &e) {
            // This block has non contiguous or overflowing indexes
            Misbehaving(*peer, "cmpctblock-bad-indexes");
            return;
        }
 
        bool received_new_header = false;
        const auto blockhash = cmpctblock.header.GetHash();
 
        {
            LOCK(cs_main);
 
            const CBlockIndex *prev_block =
                m_chainman.m_blockman.LookupBlockIndex(
                    cmpctblock.header.hashPrevBlock);
            if (!prev_block) {
                // Doesn't connect (or is genesis), instead of DoSing in
                // AcceptBlockHeader, request deeper headers
                if (!m_chainman.IsInitialBlockDownload()) {
                    MaybeSendGetHeaders(
                        pfrom, GetLocator(m_chainman.m_best_header), *peer);
                }
                return;
            }
            if (prev_block->nChainWork +
                    CalculateHeadersWork({cmpctblock.header}) <
                GetAntiDoSWorkThreshold()) {
                // If we get a low-work header in a compact block, we can ignore
                // it.
                LogPrint(BCLog::NET,
                         "Ignoring low-work compact block from peer %d\n",
                         pfrom.GetId());
                return;
            }
 
            if (!m_chainman.m_blockman.LookupBlockIndex(blockhash)) {
                received_new_header = true;
            }
        }
 
        const CBlockIndex *pindex = nullptr;
        BlockValidationState state;
        if (!m_chainman.ProcessNewBlockHeaders({cmpctblock.header},
                                               /*min_pow_checked=*/true, state,
                                               &pindex)) {
            if (state.IsInvalid()) {
                MaybePunishNodeForBlock(pfrom.GetId(), state,
                                        /*via_compact_block*/ true,
                                        "invalid header via cmpctblock");
                return;
            }
        }
 
        if (received_new_header) {
            LogInfo("Saw new cmpctblock header hash=%s peer=%d\n",
                    blockhash.ToString(), pfrom.GetId());
        }
 
        // When we succeed in decoding a block's txids from a cmpctblock
        // message we typically jump to the BLOCKTXN handling code, with a
        // dummy (empty) BLOCKTXN message, to re-use the logic there in
        // completing processing of the putative block (without cs_main).
        bool fProcessBLOCKTXN = false;
        DataStream blockTxnMsg{};
 
        // If we end up treating this as a plain headers message, call that as
        // well
        // without cs_main.
        bool fRevertToHeaderProcessing = false;
 
        // Keep a CBlock for "optimistic" compactblock reconstructions (see
        // below)
        std::shared_ptr<CBlock> pblock = std::make_shared<CBlock>();
        bool fBlockReconstructed = false;
 
        {
            LOCK(cs_main);
            // If AcceptBlockHeader returned true, it set pindex
            assert(pindex);
            UpdateBlockAvailability(pfrom.GetId(), pindex->GetBlockHash());
 
            CNodeState *nodestate = State(pfrom.GetId());
 
            // If this was a new header with more work than our tip, update the
            // peer's last block announcement time
            if (received_new_header &&
                pindex->nChainWork >
                    m_chainman.ActiveChain().Tip()->nChainWork) {
                nodestate->m_last_block_announcement = GetTime();
            }
 
            if (pindex->nStatus.hasData()) {
                // Nothing to do here
                return;
            }
 
            auto range_flight =
                mapBlocksInFlight.equal_range(pindex->GetBlockHash());
            size_t already_in_flight =
                std::distance(range_flight.first, range_flight.second);
            bool requested_block_from_this_peer{false};
 
            // Multimap ensures ordering of outstanding requests. It's either
            // empty or first in line.
            bool first_in_flight =
                already_in_flight == 0 ||
                (range_flight.first->second.first == pfrom.GetId());
 
            while (range_flight.first != range_flight.second) {
                if (range_flight.first->second.first == pfrom.GetId()) {
                    requested_block_from_this_peer = true;
                    break;
                }
                range_flight.first++;
            }
 
            if (pindex->nChainWork <=
                    m_chainman.ActiveChain()
                        .Tip()
                        ->nChainWork || // We know something better
                pindex->nTx != 0) {
                // We had this block at some point, but pruned it
                if (requested_block_from_this_peer) {
                    // We requested this block for some reason, but our mempool
                    // will probably be useless so we just grab the block via
                    // normal getdata.
                    std::vector<CInv> vInv(1);
                    vInv[0] = CInv(MSG_BLOCK, blockhash);
                    MakeAndPushMessage(pfrom, NetMsgType::GETDATA, vInv);
                }
                return;
            }
 
            // If we're not close to tip yet, give up and let parallel block
            // fetch work its magic.
            if (!already_in_flight && !CanDirectFetch()) {
                return;
            }
 
            // We want to be a bit conservative just to be extra careful about
            // DoS possibilities in compact block processing...
            if (pindex->nHeight <= m_chainman.ActiveChain().Height() + 2) {
                if ((already_in_flight < MAX_CMPCTBLOCKS_INFLIGHT_PER_BLOCK &&
                     nodestate->vBlocksInFlight.size() <
                         MAX_BLOCKS_IN_TRANSIT_PER_PEER) ||
                    requested_block_from_this_peer) {
                    std::list<QueuedBlock>::iterator *queuedBlockIt = nullptr;
                    if (!BlockRequested(config, pfrom.GetId(), *pindex,
                                        &queuedBlockIt)) {
                        if (!(*queuedBlockIt)->partialBlock) {
                            (*queuedBlockIt)
                                ->partialBlock.reset(
                                    new PartiallyDownloadedBlock(config,
                                                                 &m_mempool));
                        } else {
                            // The block was already in flight using compact
                            // blocks from the same peer.
                            LogPrint(BCLog::NET, "Peer sent us compact block "
                                                 "we were already syncing!\n");
                            return;
                        }
                    }
 
                    PartiallyDownloadedBlock &partialBlock =
                        *(*queuedBlockIt)->partialBlock;
                    ReadStatus status =
                        partialBlock.InitData(cmpctblock, vExtraTxnForCompact);
                    if (status == READ_STATUS_INVALID) {
                        // Reset in-flight state in case Misbehaving does not
                        // result in a disconnect
                        RemoveBlockRequest(pindex->GetBlockHash(),
                                           pfrom.GetId());
                        Misbehaving(*peer, "invalid compact block");
                        return;
                    } else if (status == READ_STATUS_FAILED) {
                        if (first_in_flight) {
                            // Duplicate txindices, the block is now in-flight,
                            // so just request it.
                            std::vector<CInv> vInv(1);
                            vInv[0] = CInv(MSG_BLOCK, blockhash);
                            MakeAndPushMessage(pfrom, NetMsgType::GETDATA,
                                               vInv);
                        } else {
                            // Give up for this peer and wait for other peer(s)
                            RemoveBlockRequest(pindex->GetBlockHash(),
                                               pfrom.GetId());
                        }
                        return;
                    }
 
                    BlockTransactionsRequest req;
                    for (size_t i = 0; i < cmpctblock.BlockTxCount(); i++) {
                        if (!partialBlock.IsTxAvailable(i)) {
                            req.indices.push_back(i);
                        }
                    }
                    if (req.indices.empty()) {
                        // Dirty hack to jump to BLOCKTXN code (TODO: move
                        // message handling into their own functions)
                        BlockTransactions txn;
                        txn.blockhash = blockhash;
                        blockTxnMsg << txn;
                        fProcessBLOCKTXN = true;
                    } else if (first_in_flight) {
                        // We will try to round-trip any compact blocks we get
                        // on failure, as long as it's first...
                        req.blockhash = pindex->GetBlockHash();
                        MakeAndPushMessage(pfrom, NetMsgType::GETBLOCKTXN, req);
                    } else if (pfrom.m_bip152_highbandwidth_to &&
                               (!pfrom.IsInboundConn() ||
                                IsBlockRequestedFromOutbound(blockhash) ||
                                already_in_flight <
                                    MAX_CMPCTBLOCKS_INFLIGHT_PER_BLOCK - 1)) {
                        // ... or it's a hb relay peer and:
                        // - peer is outbound, or
                        // - we already have an outbound attempt in flight (so
                        // we'll take what we can get), or
                        // - it's not the final parallel download slot (which we
                        // may reserve for first outbound)
                        req.blockhash = pindex->GetBlockHash();
                        MakeAndPushMessage(pfrom, NetMsgType::GETBLOCKTXN, req);
                    } else {
                        // Give up for this peer and wait for other peer(s)
                        RemoveBlockRequest(pindex->GetBlockHash(),
                                           pfrom.GetId());
                    }
                } else {
                    // This block is either already in flight from a different
                    // peer, or this peer has too many blocks outstanding to
                    // download from. Optimistically try to reconstruct anyway
                    // since we might be able to without any round trips.
                    PartiallyDownloadedBlock tempBlock(config, &m_mempool);
                    ReadStatus status =
                        tempBlock.InitData(cmpctblock, vExtraTxnForCompact);
                    if (status != READ_STATUS_OK) {
                        // TODO: don't ignore failures
                        return;
                    }
                    std::vector<CTransactionRef> dummy;
                    status = tempBlock.FillBlock(*pblock, dummy);
                    if (status == READ_STATUS_OK) {
                        fBlockReconstructed = true;
                    }
                }
            } else {
                if (requested_block_from_this_peer) {
                    // We requested this block, but its far into the future, so
                    // our mempool will probably be useless - request the block
                    // normally.
                    std::vector<CInv> vInv(1);
                    vInv[0] = CInv(MSG_BLOCK, blockhash);
                    MakeAndPushMessage(pfrom, NetMsgType::GETDATA, vInv);
                    return;
                } else {
                    // If this was an announce-cmpctblock, we want the same
                    // treatment as a header message.
                    fRevertToHeaderProcessing = true;
                }
            }
        } // cs_main
 
        if (fProcessBLOCKTXN) {
            return ProcessMessage(config, pfrom, NetMsgType::BLOCKTXN,
                                  blockTxnMsg, time_received, interruptMsgProc);
        }
 
        if (fRevertToHeaderProcessing) {
            // Headers received from HB compact block peers are permitted to be
            // relayed before full validation (see BIP 152), so we don't want to
            // disconnect the peer if the header turns out to be for an invalid
            // block. Note that if a peer tries to build on an invalid chain,
            // that will be detected and the peer will be banned.
            return ProcessHeadersMessage(config, pfrom, *peer,
                                         {cmpctblock.header},
                                         /*via_compact_block=*/true);
        }
 
        if (fBlockReconstructed) {
            // If we got here, we were able to optimistically reconstruct a
            // block that is in flight from some other peer.
            {
                LOCK(cs_main);
                mapBlockSource.emplace(pblock->GetHash(),
                                       std::make_pair(pfrom.GetId(), false));
            }
            // Setting force_processing to true means that we bypass some of
            // our anti-DoS protections in AcceptBlock, which filters
            // unrequested blocks that might be trying to waste our resources
            // (eg disk space). Because we only try to reconstruct blocks when
            // we're close to caught up (via the CanDirectFetch() requirement
            // above, combined with the behavior of not requesting blocks until
            // we have a chain with at least the minimum chain work), and we
            // ignore compact blocks with less work than our tip, it is safe to
            // treat reconstructed compact blocks as having been requested.
            ProcessBlock(config, pfrom, pblock, /*force_processing=*/true,
                         /*min_pow_checked=*/true);
            // hold cs_main for CBlockIndex::IsValid()
            LOCK(cs_main);
            if (pindex->IsValid(BlockValidity::TRANSACTIONS)) {
                // Clear download state for this block, which is in process from
                // some other peer. We do this after calling. ProcessNewBlock so
                // that a malleated cmpctblock announcement can't be used to
                // interfere with block relay.
                RemoveBlockRequest(pblock->GetHash(), std::nullopt);
            }
        }
        return;
    }
 
    if (msg_type == NetMsgType::BLOCKTXN) {
        // Ignore blocktxn received while importing
        if (m_chainman.m_blockman.LoadingBlocks()) {
            LogPrint(BCLog::NET,
                     "Unexpected blocktxn message received from peer %d\n",
                     pfrom.GetId());
            return;
        }
 
        BlockTransactions resp;
        vRecv >> resp;
 
        std::shared_ptr<CBlock> pblock = std::make_shared<CBlock>();
        bool fBlockRead = false;
        {
            LOCK(cs_main);
 
            auto range_flight = mapBlocksInFlight.equal_range(resp.blockhash);
            size_t already_in_flight =
                std::distance(range_flight.first, range_flight.second);
            bool requested_block_from_this_peer{false};
 
            // Multimap ensures ordering of outstanding requests. It's either
            // empty or first in line.
            bool first_in_flight =
                already_in_flight == 0 ||
                (range_flight.first->second.first == pfrom.GetId());
 
            while (range_flight.first != range_flight.second) {
                auto [node_id, block_it] = range_flight.first->second;
                if (node_id == pfrom.GetId() && block_it->partialBlock) {
                    requested_block_from_this_peer = true;
                    break;
                }
                range_flight.first++;
            }
 
            if (!requested_block_from_this_peer) {
                LogPrint(BCLog::NET,
                         "Peer %d sent us block transactions for block "
                         "we weren't expecting\n",
                         pfrom.GetId());
                return;
            }
 
            PartiallyDownloadedBlock &partialBlock =
                *range_flight.first->second.second->partialBlock;
            ReadStatus status = partialBlock.FillBlock(*pblock, resp.txn);
            if (status == READ_STATUS_INVALID) {
                // Reset in-flight state in case of Misbehaving does not
                // result in a disconnect.
                RemoveBlockRequest(resp.blockhash, pfrom.GetId());
                Misbehaving(
                    *peer,
                    "invalid compact block/non-matching block transactions");
                return;
            } else if (status == READ_STATUS_FAILED) {
                if (first_in_flight) {
                    // Might have collided, fall back to getdata now :(
                    std::vector<CInv> invs;
                    invs.push_back(CInv(MSG_BLOCK, resp.blockhash));
                    MakeAndPushMessage(pfrom, NetMsgType::GETDATA, invs);
                } else {
                    RemoveBlockRequest(resp.blockhash, pfrom.GetId());
                    LogPrint(
                        BCLog::NET,
                        "Peer %d sent us a compact block but it failed to "
                        "reconstruct, waiting on first download to complete\n",
                        pfrom.GetId());
                    return;
                }
            } else {
                // Block is either okay, or possibly we received
                // READ_STATUS_CHECKBLOCK_FAILED.
                // Note that CheckBlock can only fail for one of a few reasons:
                // 1. bad-proof-of-work (impossible here, because we've already
                //    accepted the header)
                // 2. merkleroot doesn't match the transactions given (already
                //    caught in FillBlock with READ_STATUS_FAILED, so
                //    impossible here)
                // 3. the block is otherwise invalid (eg invalid coinbase,
                //    block is too big, too many sigChecks, etc).
                // So if CheckBlock failed, #3 is the only possibility.
                // Under BIP 152, we don't DoS-ban unless proof of work is
                // invalid (we don't require all the stateless checks to have
                // been run). This is handled below, so just treat this as
                // though the block was successfully read, and rely on the
                // handling in ProcessNewBlock to ensure the block index is
                // updated, etc.
 
                // it is now an empty pointer
                RemoveBlockRequest(resp.blockhash, pfrom.GetId());
                fBlockRead = true;
                // mapBlockSource is used for potentially punishing peers and
                // updating which peers send us compact blocks, so the race
                // between here and cs_main in ProcessNewBlock is fine.
                // BIP 152 permits peers to relay compact blocks after
                // validating the header only; we should not punish peers
                // if the block turns out to be invalid.
                mapBlockSource.emplace(resp.blockhash,
                                       std::make_pair(pfrom.GetId(), false));
            }
        } // Don't hold cs_main when we call into ProcessNewBlock
        if (fBlockRead) {
            // Since we requested this block (it was in mapBlocksInFlight),
            // force it to be processed, even if it would not be a candidate for
            // new tip (missing previous block, chain not long enough, etc)
            // This bypasses some anti-DoS logic in AcceptBlock (eg to prevent
            // disk-space attacks), but this should be safe due to the
            // protections in the compact block handler -- see related comment
            // in compact block optimistic reconstruction handling.
            ProcessBlock(config, pfrom, pblock, /*force_processing=*/true,
                         /*min_pow_checked=*/true);
        }
        return;
    }
 
    if (msg_type == NetMsgType::HEADERS) {
        // Ignore headers received while importing
        if (m_chainman.m_blockman.LoadingBlocks()) {
            LogPrint(BCLog::NET,
                     "Unexpected headers message received from peer %d\n",
                     pfrom.GetId());
            return;
        }
 
        std::vector<CBlockHeader> headers;
 
        // Bypass the normal CBlock deserialization, as we don't want to risk
        // deserializing 2000 full blocks.
        unsigned int nCount = ReadCompactSize(vRecv);
        if (nCount > MAX_HEADERS_RESULTS) {
            Misbehaving(*peer,
                        strprintf("too-many-headers: headers message size = %u",
                                  nCount));
            return;
        }
        headers.resize(nCount);
        for (unsigned int n = 0; n < nCount; n++) {
            vRecv >> headers[n];
            // Ignore tx count; assume it is 0.
            ReadCompactSize(vRecv);
        }
 
        ProcessHeadersMessage(config, pfrom, *peer, std::move(headers),
                              /*via_compact_block=*/false);
 
        // Check if the headers presync progress needs to be reported to
        // validation. This needs to be done without holding the
        // m_headers_presync_mutex lock.
        if (m_headers_presync_should_signal.exchange(false)) {
            HeadersPresyncStats stats;
            {
                LOCK(m_headers_presync_mutex);
                auto it =
                    m_headers_presync_stats.find(m_headers_presync_bestpeer);
                if (it != m_headers_presync_stats.end()) {
                    stats = it->second;
                }
            }
            if (stats.second) {
                m_chainman.ReportHeadersPresync(
                    stats.first, stats.second->first, stats.second->second);
            }
        }
 
        return;
    }
 
    if (msg_type == NetMsgType::BLOCK) {
        // Ignore block received while importing
        if (m_chainman.m_blockman.LoadingBlocks()) {
            LogPrint(BCLog::NET,
                     "Unexpected block message received from peer %d\n",
                     pfrom.GetId());
            return;
        }
 
        std::shared_ptr<CBlock> pblock = std::make_shared<CBlock>();
        vRecv >> *pblock;
 
        LogPrint(BCLog::NET, "received block %s peer=%d\n",
                 pblock->GetHash().ToString(), pfrom.GetId());
 
        const CBlockIndex *prev_block{
            WITH_LOCK(m_chainman.GetMutex(),
                      return m_chainman.m_blockman.LookupBlockIndex(
                          pblock->hashPrevBlock))};
 
        if (IsBlockMutated(/*block=*/*pblock)) {
            LogPrintLevel(BCLog::NET, BCLog::Level::Debug,
                          "Received mutated block from peer=%d\n", peer->m_id);
            Misbehaving(*peer, "mutated block");
            WITH_LOCK(cs_main,
                      RemoveBlockRequest(pblock->GetHash(), peer->m_id));
            return;
        }
 
        // Process all blocks from whitelisted peers, even if not requested,
        // unless we're still syncing with the network. Such an unrequested
        // block may still be processed, subject to the conditions in
        // AcceptBlock().
        bool forceProcessing = pfrom.HasPermission(NetPermissionFlags::NoBan) &&
                               !m_chainman.IsInitialBlockDownload();
        const BlockHash hash = pblock->GetHash();
        bool min_pow_checked = false;
        {
            LOCK(cs_main);
            // Always process the block if we requested it, since we may
            // need it even when it's not a candidate for a new best tip.
            forceProcessing = IsBlockRequested(hash);
            RemoveBlockRequest(hash, pfrom.GetId());
            // mapBlockSource is only used for punishing peers and setting
            // which peers send us compact blocks, so the race between here and
            // cs_main in ProcessNewBlock is fine.
            mapBlockSource.emplace(hash, std::make_pair(pfrom.GetId(), true));
 
            // Check work on this block against our anti-dos thresholds.
            if (prev_block &&
                prev_block->nChainWork +
                        CalculateHeadersWork({pblock->GetBlockHeader()}) >=
                    GetAntiDoSWorkThreshold()) {
                min_pow_checked = true;
            }
        }
        ProcessBlock(config, pfrom, pblock, forceProcessing, min_pow_checked);
        return;
    }
 
    if (msg_type == NetMsgType::AVAHELLO) {
        if (!m_avalanche) {
            return;
        }
        {
            LOCK(pfrom.cs_avalanche_pubkey);
            if (pfrom.m_avalanche_pubkey.has_value()) {
                LogPrint(
                    BCLog::AVALANCHE,
                    "Ignoring avahello from peer %d: already in our node set\n",
                    pfrom.GetId());
                return;
            }
 
            avalanche::Delegation delegation;
            vRecv >> delegation;
 
            // A delegation with an all zero limited id indicates that the peer
            // has no proof, so we're done.
            if (delegation.getLimitedProofId() != uint256::ZERO) {
                avalanche::DelegationState state;
                CPubKey pubkey;
                if (!delegation.verify(state, pubkey)) {
                    Misbehaving(*peer, "invalid-delegation");
                    return;
                }
                pfrom.m_avalanche_pubkey = std::move(pubkey);
 
                HashWriter sighasher{};
                sighasher << delegation.getId();
                sighasher << pfrom.nRemoteHostNonce;
                sighasher << pfrom.GetLocalNonce();
                sighasher << pfrom.nRemoteExtraEntropy;
                sighasher << pfrom.GetLocalExtraEntropy();
 
                SchnorrSig sig;
                vRecv >> sig;
                if (!(*pfrom.m_avalanche_pubkey)
                         .VerifySchnorr(sighasher.GetHash(), sig)) {
                    Misbehaving(*peer, "invalid-avahello-signature");
                    return;
                }
 
                // If we don't know this proof already, add it to the tracker so
                // it can be requested.
                const avalanche::ProofId proofid(delegation.getProofId());
                if (!AlreadyHaveProof(proofid)) {
                    const bool preferred = isPreferredDownloadPeer(pfrom);
                    LOCK(cs_proofrequest);
                    AddProofAnnouncement(pfrom, proofid,
                                         GetTime<std::chrono::microseconds>(),
                                         preferred);
                }
 
                uint32_t max_elements{AVALANCHE_MAX_ELEMENT_POLL_LEGACY};
                if (pfrom.GetCommonVersion() >=
                        AVALANCHE_MAX_ELEMENT_BUMP_VERSION &&
                    !vRecv.empty()) {
                    vRecv >> max_elements;
                    // max_elements below AVALANCHE_MAX_ELEMENT_POLL_LEGACY is
                    // invalid
                    if (max_elements < AVALANCHE_MAX_ELEMENT_POLL_LEGACY) {
                        Misbehaving(*peer, "avahello-max-elements-too-low");
                        return;
                    }
                }
 
                // Don't check the return value. If it fails we probably don't
                // know about the proof yet.
                m_avalanche->withPeerManager([&](avalanche::PeerManager &pm) {
                    return pm.addNode(pfrom.GetId(), proofid, max_elements);
                });
            }
 
            pfrom.m_avalanche_enabled = true;
        }
 
        // Send getavaaddr and getavaproofs to our avalanche outbound or
        // manual connections
        if (!pfrom.IsInboundConn()) {
            MakeAndPushMessage(pfrom, NetMsgType::GETAVAADDR);
            WITH_LOCK(peer->m_addr_token_bucket_mutex,
                      peer->m_addr_token_bucket += m_opts.max_addr_to_send);
 
            if (peer->m_proof_relay && !m_chainman.IsInitialBlockDownload()) {
                MakeAndPushMessage(pfrom, NetMsgType::GETAVAPROOFS);
                peer->m_proof_relay->compactproofs_requested = true;
            }
        }
 
        return;
    }
 
    if (msg_type == NetMsgType::AVAPOLL) {
        if (!m_avalanche) {
            return;
        }
        const auto now = Now<SteadyMilliseconds>();
 
        const auto last_poll = pfrom.m_last_poll;
        pfrom.m_last_poll = now;
 
        if (now <
            last_poll + std::chrono::milliseconds(m_opts.avalanche_cooldown)) {
            LogPrint(BCLog::AVALANCHE,
                     "Ignoring repeated avapoll from peer %d: cooldown not "
                     "elapsed\n",
                     pfrom.GetId());
            return;
        }
 
        const bool quorum_established = m_avalanche->isQuorumEstablished();
 
        uint64_t round;
        Unserialize(vRecv, round);
 
        unsigned int nCount = ReadCompactSize(vRecv);
        if (nCount > m_avalanche->getMaxElementPoll()) {
            Misbehaving(
                *peer,
                strprintf("too-many-ava-poll: poll message size = %u", nCount));
            return;
        }
 
        std::vector<avalanche::Vote> votes;
        votes.reserve(nCount);
 
        bool fPreconsensus{false};
        bool fStakingPreconsensus{false};
        {
            LOCK(::cs_main);
            const CBlockIndex *tip = m_chainman.ActiveTip();
            fPreconsensus = m_avalanche->isPreconsensusActivated(tip);
            fStakingPreconsensus =
                m_avalanche->isStakingPreconsensusActivated(tip);
        }
 
        for (unsigned int n = 0; n < nCount; n++) {
            CInv inv;
            vRecv >> inv;
 
            // Default vote for unknown inv type
            uint32_t vote = -1;
 
            // We don't vote definitively until we have an established quorum
            if (!quorum_established) {
                votes.emplace_back(vote, inv.hash);
                continue;
            }
 
            // If inv's type is known, get a vote for its hash
            switch (inv.type) {
                case MSG_TX: {
                    if (fPreconsensus) {
                        vote =
                            GetAvalancheVoteForTx(*m_avalanche, TxId(inv.hash));
                    }
                } break;
                case MSG_BLOCK: {
                    vote = WITH_LOCK(cs_main, return GetAvalancheVoteForBlock(
                                                  BlockHash(inv.hash)));
                } break;
                case MSG_AVA_PROOF: {
                    vote = getAvalancheVoteForProof(
                        *m_avalanche, avalanche::ProofId(inv.hash));
                } break;
                case MSG_AVA_STAKE_CONTENDER: {
                    if (fStakingPreconsensus) {
                        vote = m_avalanche->getStakeContenderStatus(
                            avalanche::StakeContenderId(inv.hash));
                    }
                } break;
                default: {
                    LogPrint(BCLog::AVALANCHE,
                             "poll inv type %d unknown from peer=%d\n",
                             inv.type, pfrom.GetId());
                }
            }
 
            votes.emplace_back(vote, inv.hash);
        }
 
        // Send the query to the node.
        m_avalanche->sendResponse(
            &pfrom, avalanche::Response(round, m_opts.avalanche_cooldown,
                                        std::move(votes)));
        return;
    }
 
    if (msg_type == NetMsgType::AVARESPONSE) {
        if (!m_avalanche) {
            return;
        }
        // As long as QUIC is not implemented, we need to sign response and
        // verify response's signatures in order to avoid any manipulation of
        // messages at the transport level.
        HashVerifier verifier(vRecv);
        avalanche::Response response;
        verifier >> response;
 
        SchnorrSig sig;
        vRecv >> sig;
 
        {
            LOCK(pfrom.cs_avalanche_pubkey);
            if (!pfrom.m_avalanche_pubkey.has_value() ||
                !(*pfrom.m_avalanche_pubkey)
                     .VerifySchnorr(verifier.GetHash(), sig)) {
                Misbehaving(*peer, "invalid-ava-response-signature");
                return;
            }
        }
 
        auto now = GetTime<std::chrono::seconds>();
 
        std::vector<avalanche::VoteItemUpdate> updates;
        bool disconnect{false};
        std::string error;
        if (!m_avalanche->registerVotes(pfrom.GetId(), response, updates,
                                        disconnect, error)) {
            if (disconnect) {
                Misbehaving(*peer, error);
                return;
            }
 
            // Otherwise the node may have got a network issue. Increase the
            // fault counter instead and only ban if we reached a threshold.
            // This allows for fault tolerance should there be a temporary
            // outage while still preventing DoS'ing behaviors, as the counter
            // is reset if no fault occured over some time period.
            pfrom.m_avalanche_message_fault_counter++;
            pfrom.m_avalanche_last_message_fault = now;
 
            // Allow up to 12 messages before increasing the ban score. Since
            // the queries are cleared after 10s, this is at least 2 minutes
            // of network outage tolerance over the 1h window.
            if (pfrom.m_avalanche_message_fault_counter > 12) {
                LogPrint(
                    BCLog::AVALANCHE,
                    "Repeated failure to register votes from peer %d: %s\n",
                    pfrom.GetId(), error);
                pfrom.m_avalanche_message_fault_score += 2;
                if (pfrom.m_avalanche_message_fault_score > 100) {
                    Misbehaving(*peer, error);
                }
                return;
            }
        }
 
        // If no fault occurred within the last hour, reset the fault counter
        if (now > (pfrom.m_avalanche_last_message_fault.load() + 1h)) {
            pfrom.m_avalanche_message_fault_counter = 0;
        }
 
        pfrom.invsVoted(response.GetVotes().size());
 
        auto logVoteUpdate = [](const auto &voteUpdate,
                                const std::string &voteItemTypeStr,
                                const auto &voteItemId) {
            std::string voteOutcome;
            bool alwaysPrint = false;
            switch (voteUpdate.getStatus()) {
                case avalanche::VoteStatus::Invalid:
                    voteOutcome = "invalidated";
                    alwaysPrint = true;
                    break;
                case avalanche::VoteStatus::Rejected:
                    voteOutcome = "rejected";
                    break;
                case avalanche::VoteStatus::Accepted:
                    voteOutcome = "accepted";
                    break;
                case avalanche::VoteStatus::Finalized:
                    voteOutcome = "finalized";
                    // Don't log tx finalization unconditionally as it can be
                    // quite spammy.
                    alwaysPrint = voteItemTypeStr != "tx";
                    break;
                case avalanche::VoteStatus::Stale:
                    voteOutcome = "stalled";
                    alwaysPrint = true;
                    break;
 
                    // No default case, so the compiler can warn about missing
                    // cases
            }
 
            // Always log the stake contenders to the avalanche category
            alwaysPrint &= (voteItemTypeStr != "contender");
 
            if (alwaysPrint) {
                LogPrintf("Avalanche %s %s %s\n", voteOutcome, voteItemTypeStr,
                          voteItemId.ToString());
            } else {
                // Only print these messages if -debug=avalanche is set
                LogPrint(BCLog::AVALANCHE, "Avalanche %s %s %s\n", voteOutcome,
                         voteItemTypeStr, voteItemId.ToString());
            }
        };
 
        bool shouldActivateBestChain = false;
 
        bool fPreconsensus{false};
        bool fStakingPreconsensus{false};
        {
            LOCK(::cs_main);
            const CBlockIndex *tip = m_chainman.ActiveTip();
            fPreconsensus = m_avalanche->isPreconsensusActivated(tip);
            fStakingPreconsensus =
                m_avalanche->isStakingPreconsensusActivated(tip);
        }
 
        for (const auto &u : updates) {
            const avalanche::AnyVoteItem &item = u.getVoteItem();
 
            // Don't use a visitor here as we want to ignore unsupported item
            // types. This comes in handy when adding new types.
            if (auto pitem = std::get_if<const avalanche::ProofRef>(&item)) {
                avalanche::ProofRef proof = *pitem;
                const avalanche::ProofId &proofid = proof->getId();
 
                logVoteUpdate(u, "proof", proofid);
 
                auto rejectionMode =
                    avalanche::PeerManager::RejectionMode::DEFAULT;
                auto nextCooldownTimePoint = GetTime<std::chrono::seconds>();
                switch (u.getStatus()) {
                    case avalanche::VoteStatus::Invalid:
                        m_avalanche->withPeerManager(
                            [&](avalanche::PeerManager &pm) {
                                pm.setInvalid(proofid);
                            });
                        // Fallthrough
                    case avalanche::VoteStatus::Stale:
                        // Invalidate mode removes the proof from all proof
                        // pools
                        rejectionMode =
                            avalanche::PeerManager::RejectionMode::INVALIDATE;
                        // Fallthrough
                    case avalanche::VoteStatus::Rejected:
                        if (!m_avalanche->withPeerManager(
                                [&](avalanche::PeerManager &pm) {
                                    return pm.rejectProof(proofid,
                                                          rejectionMode);
                                })) {
                            LogPrint(BCLog::AVALANCHE,
                                     "ERROR: Failed to reject proof: %s\n",
                                     proofid.GetHex());
                        }
                        break;
                    case avalanche::VoteStatus::Finalized:
                        m_avalanche->setRecentlyFinalized(proofid);
                        nextCooldownTimePoint += std::chrono::seconds(
                            m_opts.avalanche_peer_replacement_cooldown);
                    case avalanche::VoteStatus::Accepted:
                        if (!m_avalanche->withPeerManager(
                                [&](avalanche::PeerManager &pm) {
                                    pm.registerProof(
                                        proof,
                                        avalanche::PeerManager::
                                            RegistrationMode::FORCE_ACCEPT);
                                    return pm.forPeer(
                                        proofid,
                                        [&](const avalanche::Peer &peer) {
                                            pm.updateNextPossibleConflictTime(
                                                peer.peerid,
                                                nextCooldownTimePoint);
                                            if (u.getStatus() ==
                                                avalanche::VoteStatus::
                                                    Finalized) {
                                                pm.setFinalized(peer.peerid);
                                            }
                                            // Only fail if the peer was not
                                            // created
                                            return true;
                                        });
                                })) {
                            LogPrint(BCLog::AVALANCHE,
                                     "ERROR: Failed to accept proof: %s\n",
                                     proofid.GetHex());
                        }
                        break;
                }
            }
 
            auto getBlockFromIndex = [this](const CBlockIndex *pindex) {
                // First check if the block is cached before reading
                // from disk.
                std::shared_ptr<const CBlock> pblock = WITH_LOCK(
                    m_most_recent_block_mutex, return m_most_recent_block);
 
                if (!pblock || pblock->GetHash() != pindex->GetBlockHash()) {
                    std::shared_ptr<CBlock> pblockRead =
                        std::make_shared<CBlock>();
                    if (!m_chainman.m_blockman.ReadBlock(*pblockRead,
                                                         *pindex)) {
                        assert(!"cannot load block from disk");
                    }
                    pblock = pblockRead;
                }
                return pblock;
            };
 
            if (auto pitem = std::get_if<const CBlockIndex *>(&item)) {
                CBlockIndex *pindex = const_cast<CBlockIndex *>(*pitem);
 
                shouldActivateBestChain = true;
 
                logVoteUpdate(u, "block", pindex->GetBlockHash());
 
                switch (u.getStatus()) {
                    case avalanche::VoteStatus::Rejected: {
                        BlockValidationState state;
                        m_chainman.ActiveChainstate().ParkBlock(state, pindex);
                        if (!state.IsValid()) {
                            LogPrintf("ERROR: Database error: %s\n",
                                      state.GetRejectReason());
                            return;
                        }
                    } break;
                    case avalanche::VoteStatus::Invalid: {
                        BlockValidationState state;
                        m_chainman.ActiveChainstate().ParkBlock(state, pindex);
                        if (!state.IsValid()) {
                            LogPrintf("ERROR: Database error: %s\n",
                                      state.GetRejectReason());
                            return;
                        }
 
                        auto pblock = getBlockFromIndex(pindex);
                        assert(pblock);
 
                        WITH_LOCK(cs_main, GetMainSignals().BlockInvalidated(
                                               pindex, pblock));
                    } break;
                    case avalanche::VoteStatus::Accepted: {
                        LOCK(cs_main);
                        m_chainman.ActiveChainstate().UnparkBlock(pindex);
                    } break;
                    case avalanche::VoteStatus::Finalized: {
                        m_avalanche->setRecentlyFinalized(
                            pindex->GetBlockHash());
 
                        m_avalanche->cleanupStakingRewards(pindex->nHeight);
 
                        std::unique_ptr<node::CBlockTemplate> blockTemplate;
                        {
                            LOCK(cs_main);
                            auto &chainstate = m_chainman.ActiveChainstate();
                            chainstate.UnparkBlock(pindex);
 
                            const bool newlyFinalized =
                                !chainstate.IsBlockAvalancheFinalized(pindex) &&
                                chainstate.AvalancheFinalizeBlock(pindex,
                                                                  *m_avalanche);
 
                            // Skip if the block is already finalized, aka an
                            // ancestor of the finalized tip.
                            if (fPreconsensus && newlyFinalized) {
                                auto pblock = getBlockFromIndex(pindex);
                                assert(pblock);
 
                                {
                                    // If the finalized block is not the tip, we
                                    // need to keep track of the transactions
                                    // from the non final blocks, so that we can
                                    // check if they were finalized by
                                    // pre-consensus. If these transactions were
                                    // pruned from the radix tree, their
                                    // finalization status could be lost in the
                                    // case the non final blocks are later
                                    // rejected.
                                    CBlockIndex *tip = m_chainman.ActiveTip();
                                    std::unordered_set<TxId, SaltedTxIdHasher>
                                        confirmedTxIdsInNonFinalizedBlocks;
                                    for (const CBlockIndex *block = tip;
                                         block != nullptr && block != pindex;
                                         block = block->pprev) {
                                        auto currentBlock =
                                            getBlockFromIndex(block);
                                        assert(currentBlock);
                                        for (const auto &tx :
                                             currentBlock->vtx) {
                                            confirmedTxIdsInNonFinalizedBlocks
                                                .insert(tx->GetId());
                                        }
                                    }
 
                                    // Remove the transactions that are not
                                    // confirmed
                                    LOCK(m_mempool.cs);
                                    m_mempool.removeForFinalizedBlock(
                                        confirmedTxIdsInNonFinalizedBlocks);
 
                                    // Now add mempool transactions to the poll.
                                    // To determine which transaction to add, we
                                    // leverage the legacy block template
                                    // construction method and build a template
                                    // with the most valuable txs in it. These
                                    // transactions are sorted topologically;
                                    // parents come before children, so we can
                                    // poll for children first and optimize the
                                    // number of polls.
                                    node::BlockAssembler blockAssembler(
                                        config, chainstate, &m_mempool,
                                        m_avalanche);
                                    blockAssembler.pblocktemplate.reset(
                                        new node::CBlockTemplate());
 
                                    if (blockAssembler.pblocktemplate) {
                                        blockAssembler.addTxs(m_mempool);
                                        blockTemplate = std::move(
                                            blockAssembler.pblocktemplate);
                                    }
                                }
                            }
                        } // release cs_main
 
                        if (blockTemplate) {
                            // We could check if the tx is final already
                            // but addToReconcile will skip the recently
                            // finalized txs, so let's abuse this
                            // feature and avoid a tree lookup for each
                            // tx as an optimization.
                            for (const auto &templateEntry :
                                 reverse_iterate(blockTemplate->entries)) {
                                m_avalanche->addToReconcile(templateEntry.tx);
                            }
                        }
                    } break;
                    case avalanche::VoteStatus::Stale:
                        // Fall back on Nakamoto consensus in the absence of
                        // Avalanche votes for other competing or descendant
                        // blocks.
                        break;
                }
            }
 
            if (fStakingPreconsensus) {
                if (auto pitem =
                        std::get_if<const avalanche::StakeContenderId>(&item)) {
                    const avalanche::StakeContenderId contenderId = *pitem;
                    logVoteUpdate(u, "contender", contenderId);
 
                    switch (u.getStatus()) {
                        case avalanche::VoteStatus::Rejected:
                        case avalanche::VoteStatus::Invalid: {
                            m_avalanche->rejectStakeContender(contenderId);
                            break;
                        }
                        case avalanche::VoteStatus::Finalized: {
                            m_avalanche->setRecentlyFinalized(contenderId);
                            m_avalanche->finalizeStakeContender(contenderId);
                            break;
                        }
                        case avalanche::VoteStatus::Accepted: {
                            m_avalanche->acceptStakeContender(contenderId);
                            break;
                        }
                        case avalanche::VoteStatus::Stale:
                            break;
                    }
                }
            }
 
            if (!fPreconsensus) {
                continue;
            }
 
            if (auto pitem = std::get_if<const CTransactionRef>(&item)) {
                const CTransactionRef tx = *pitem;
                assert(tx != nullptr);
 
                const TxId &txid = tx->GetId();
                const auto status{u.getStatus()};
 
                if (status != avalanche::VoteStatus::Finalized) {
                    // Because we also want to log the parents txs of this
                    // finalized tx, we log the finalization later.
                    logVoteUpdate(u, "tx", txid);
                }
 
                switch (status) {
                    case avalanche::VoteStatus::Invalid: // Fallthrough
                    case avalanche::VoteStatus::Rejected: {
                        // Remove from the mempool and the finalized tree, as
                        // well as all the children txs. Note that removal from
                        // the finalized tree is only a safety net and should
                        // never happen.
                        LOCK2(cs_main, m_mempool.cs);
 
                        std::shared_ptr<const std::vector<Coin>> spentCoins;
                        if (status == avalanche::VoteStatus::Invalid) {
                            // Get the spent coins before removing the tx from
                            // the mempool.
                            CCoinsViewMemPool coinViewMempool(
                                &m_chainman.ActiveChainstate().CoinsTip(),
                                m_mempool);
                            CCoinsViewCache coinViewCache(&coinViewMempool);
                            auto _spentCoins = GetSpentCoins(tx, coinViewCache);
                            // spentCoins can be null here if the parent tx has
                            // been invalidated already
                            spentCoins =
                                _spentCoins.has_value()
                                    ? std::make_shared<const std::vector<Coin>>(
                                          std::move(*_spentCoins))
                                    : nullptr;
                        }
 
                        if (m_mempool.exists(txid)) {
                            m_mempool.removeRecursive(
                                *tx, MemPoolRemovalReason::AVALANCHE);
 
                            std::vector<CTransactionRef> conflictingTxs =
                                m_mempool.withConflicting(
                                    [&tx](const TxConflicting &conflicting) {
                                        return conflicting.GetConflictTxs(tx);
                                    });
 
                            if (conflictingTxs.size() > 0) {
                                // Pull the first tx only, erase the others so
                                // they can be re-downloaded if needed.
                                auto result = m_chainman.ProcessTransaction(
                                    conflictingTxs[0]);
                                if (!result.m_state.IsValid()) {
                                    LogPrint(
                                        BCLog::AVALANCHE,
                                        "Attempting to pull a now invalid "
                                        "conflicting tx %s to mempool\n",
                                        conflictingTxs[0]->GetId().ToString());
                                }
                            }
 
                            m_mempool.withConflicting(
                                [&conflictingTxs,
                                 &tx](TxConflicting &conflicting) {
                                    for (const auto &conflictingTx :
                                         conflictingTxs) {
                                        conflicting.EraseTx(
                                            conflictingTx->GetId());
                                    }
 
                                    // Note that we don't store the descendants,
                                    // which should be re-downloaded. This could
                                    // be optimized but we will have to manage
                                    // the topological ordering.
                                    conflicting.AddTx(tx, NO_NODE);
                                });
                        }
 
                        if (status == avalanche::VoteStatus::Invalid) {
                            // Also remove from the conflicting pool. If it was
                            // in the mempool (unlikely) we just moved it there.
                            m_mempool.withConflicting(
                                [&txid](TxConflicting &conflicting) {
                                    conflicting.EraseTx(txid);
                                });
 
                            m_recent_rejects.insert(txid);
 
                            AddToCompactExtraTransactions(tx);
 
                            GetMainSignals().TransactionInvalidated(tx,
                                                                    spentCoins);
                        }
 
                        break;
                    }
                    case avalanche::VoteStatus::Finalized:
                        // fallthrough
                    case avalanche::VoteStatus::Accepted: {
                        {
                            LOCK2(cs_main, m_mempool.cs);
                            if (m_mempool.withConflicting(
                                    [&txid](const TxConflicting &conflicting) {
                                        return conflicting.HaveTx(txid);
                                    })) {
                                // Swap conflicting txs from/to the mempool
                                std::vector<CTransactionRef>
                                    mempool_conflicting_txs;
                                for (const auto &txin : tx->vin) {
                                    // Find the conflicting txs
                                    if (CTransactionRef conflict =
                                            m_mempool.GetConflictTx(
                                                txin.prevout)) {
                                        mempool_conflicting_txs.push_back(
                                            std::move(conflict));
                                    }
                                }
                                m_mempool.removeConflicts(*tx);
 
                                auto result = m_chainman.ProcessTransaction(tx);
                                assert(result.m_state.IsValid());
 
                                m_mempool.withConflicting(
                                    [&txid, &mempool_conflicting_txs](
                                        TxConflicting &conflicting) {
                                        conflicting.EraseTx(txid);
                                        // Store the first tx only, the others
                                        // can be re-downloaded if needed.
                                        if (mempool_conflicting_txs.size() >
                                            0) {
                                            conflicting.AddTx(
                                                mempool_conflicting_txs[0],
                                                NO_NODE);
                                        }
                                    });
                            }
                        }
 
                        if (status == avalanche::VoteStatus::Finalized) {
                            LOCK2(cs_main, m_mempool.cs);
                            auto it = m_mempool.GetIter(txid);
                            if (!it.has_value()) {
                                LogPrint(
                                    BCLog::AVALANCHE,
                                    "Error: finalized tx (%s) is not in the "
                                    "mempool\n",
                                    txid.ToString());
                                break;
                            }
 
                            std::vector<TxId> finalizedTxIds;
                            m_mempool.setAvalancheFinalized(
                                **it, m_chainparams.GetConsensus(),
                                *Assert(m_chainman.ActiveTip()),
                                finalizedTxIds);
 
                            for (const auto &finalized_txid : finalizedTxIds) {
                                m_avalanche->setRecentlyFinalized(
                                    finalized_txid);
                                // Log the parent tx being implicitely finalized
                                // as well
                                logVoteUpdate(u, "tx", finalized_txid);
                            }
 
                            // NO_THREAD_SAFETY_ANALYSIS because
                            // m_recent_rejects requires cs_main in the lambda
                            m_mempool.withConflicting(
                                [&](TxConflicting &conflicting)
                                    NO_THREAD_SAFETY_ANALYSIS {
                                        std::vector<CTransactionRef>
                                            conflictingTxs =
                                                conflicting.GetConflictTxs(tx);
                                        for (const auto &conflictingTx :
                                             conflictingTxs) {
                                            m_recent_rejects.insert(
                                                conflictingTx->GetId());
                                            conflicting.EraseTx(
                                                conflictingTx->GetId());
                                        }
                                    });
                        }
 
                        break;
                    }
                    case avalanche::VoteStatus::Stale: {
                        LOCK(cs_main);
 
                        // If the tx is stale, there is no point keeping it
                        // around as it will no be mined. Let's remove it but
                        // also forget we got it so it can be eventually
                        // re-downloaded.
                        {
                            LOCK(m_mempool.cs);
                            m_mempool.removeRecursive(
                                *tx, MemPoolRemovalReason::AVALANCHE);
 
                            m_mempool.withConflicting(
                                [&txid](TxConflicting &conflicting) {
                                    conflicting.EraseTx(txid);
                                });
                        }
 
                        // Make sure we can request this tx again
                        m_txrequest.ForgetInvId(txid);
 
                        {
                            // Save the stalled txids so that we can relay them
                            // to our peers.
                            LOCK(m_peer_mutex);
                            for (auto &it : m_peer_map) {
                                auto tx_relay = (*it.second).GetTxRelay();
                                if (!tx_relay) {
                                    continue;
                                }
 
                                LOCK(tx_relay->m_tx_inventory_mutex);
 
                                // We limit the size of the stalled txs set to
                                // avoid unbounded memory growth. In practice,
                                // this should not be an issue as stalled txs
                                // should be few and far between. If we are at
                                // the limit, remove the oldest entries.
                                auto &stalled_by_time =
                                    tx_relay->m_avalanche_stalled_txids
                                        .get<by_time>();
                                if (stalled_by_time.size() >=
                                    MAX_AVALANCHE_STALLED_TXIDS_PER_PEER) {
                                    stalled_by_time.erase(
                                        stalled_by_time.begin()->timeAdded);
                                }
 
                                tx_relay->m_avalanche_stalled_txids.insert(
                                    {txid, now});
                            }
                        }
 
                        AddToCompactExtraTransactions(tx);
 
                        break;
                    }
                }
            }
        }
 
        if (shouldActivateBestChain) {
            BlockValidationState state;
            if (!m_chainman.ActiveChainstate().ActivateBestChain(
                    state, /*pblock=*/nullptr, m_avalanche)) {
                LogPrintf("failed to activate chain (%s)\n", state.ToString());
            }
        }
 
        return;
    }
 
    if (msg_type == NetMsgType::AVAPROOF) {
        if (!m_avalanche) {
            return;
        }
        auto proof = RCUPtr<avalanche::Proof>::make();
        vRecv >> *proof;
 
        ReceivedAvalancheProof(pfrom, *peer, proof);
 
        return;
    }
 
    if (msg_type == NetMsgType::GETAVAPROOFS) {
        if (!m_avalanche) {
            return;
        }
        if (peer->m_proof_relay == nullptr) {
            return;
        }
 
        peer->m_proof_relay->lastSharedProofsUpdate =
            GetTime<std::chrono::seconds>();
 
        peer->m_proof_relay->sharedProofs =
            m_avalanche->withPeerManager([&](const avalanche::PeerManager &pm) {
                return pm.getShareableProofsSnapshot();
            });
 
        avalanche::CompactProofs compactProofs(
            peer->m_proof_relay->sharedProofs);
        MakeAndPushMessage(pfrom, NetMsgType::AVAPROOFS, compactProofs);
 
        return;
    }
 
    if (msg_type == NetMsgType::AVAPROOFS) {
        if (!m_avalanche) {
            return;
        }
        if (peer->m_proof_relay == nullptr) {
            return;
        }
 
        // Only process the compact proofs if we requested them
        if (!peer->m_proof_relay->compactproofs_requested) {
            LogPrint(BCLog::AVALANCHE, "Ignoring unsollicited avaproofs\n");
            return;
        }
        peer->m_proof_relay->compactproofs_requested = false;
 
        avalanche::CompactProofs compactProofs;
        try {
            vRecv >> compactProofs;
        } catch (std::ios_base::failure &e) {
            // This compact proofs have non contiguous or overflowing indexes
            Misbehaving(*peer, "avaproofs-bad-indexes");
            return;
        }
 
        // If there are prefilled proofs, process them first
        for (const auto &prefilledProof : compactProofs.getPrefilledProofs()) {
            if (!ReceivedAvalancheProof(pfrom, *peer, prefilledProof.proof)) {
                // If we got an invalid proof, the peer is getting banned and we
                // can bail out.
                return;
            }
        }
 
        // If there is no shortid, avoid parsing/responding/accounting for the
        // message.
        if (compactProofs.getShortIDs().size() == 0) {
            return;
        }
 
        // To determine the chance that the number of entries in a bucket
        // exceeds N, we use the fact that the number of elements in a single
        // bucket is binomially distributed (with n = the number of shorttxids
        // S, and p = 1 / the number of buckets), that in the worst case the
        // number of buckets is equal to S (due to std::unordered_map having a
        // default load factor of 1.0), and that the chance for any bucket to
        // exceed N elements is at most buckets * (the chance that any given
        // bucket is above N elements). Thus:
        //   P(max_elements_per_bucket > N) <=
        //     S * (1 - cdf(binomial(n=S,p=1/S), N))
        // If we assume up to 21000000, allowing 15 elements per bucket should
        // only fail once per ~2.5 million avaproofs transfers (per peer and
        // connection).
        // TODO re-evaluate the bucket count to a more realistic value.
        // TODO: In the case of a shortid-collision, we should request all the
        // proofs which collided. For now, we only request one, which is not
        // that bad considering this event is expected to be very rare.
        auto shortIdProcessor =
            avalanche::ProofShortIdProcessor(compactProofs.getPrefilledProofs(),
                                             compactProofs.getShortIDs(), 15);
 
        if (shortIdProcessor.hasOutOfBoundIndex()) {
            // This should be catched by deserialization, but catch it here as
            // well as a good measure.
            Misbehaving(*peer, "avaproofs-bad-indexes");
            return;
        }
        if (!shortIdProcessor.isEvenlyDistributed()) {
            // This is suspicious, don't ban but bail out
            return;
        }
 
        std::vector<std::pair<avalanche::ProofId, bool>> remoteProofsStatus;
        m_avalanche->withPeerManager([&](const avalanche::PeerManager &pm) {
            pm.forEachPeer([&](const avalanche::Peer &peer) {
                assert(peer.proof);
                uint64_t shortid = compactProofs.getShortID(peer.getProofId());
 
                int added =
                    shortIdProcessor.matchKnownItem(shortid, peer.proof);
 
                // No collision
                if (added >= 0) {
                    // Because we know the proof, we can determine if our peer
                    // has it (added = 1) or not (added = 0) and update the
                    // remote proof status accordingly.
                    remoteProofsStatus.emplace_back(peer.getProofId(),
                                                    added > 0);
                }
 
                // In order to properly determine which proof is missing, we
                // need to keep scanning for all our proofs.
                return true;
            });
        });
 
        avalanche::ProofsRequest req;
        for (size_t i = 0; i < compactProofs.size(); i++) {
            if (shortIdProcessor.getItem(i) == nullptr) {
                req.indices.push_back(i);
            }
        }
 
        MakeAndPushMessage(pfrom, NetMsgType::AVAPROOFSREQ, req);
 
        const NodeId nodeid = pfrom.GetId();
 
        // We want to keep a count of how many nodes we successfully requested
        // avaproofs from as this is used to determine when we are confident our
        // quorum is close enough to the other participants.
        m_avalanche->avaproofsSent(nodeid);
 
        // Only save remote proofs from stakers
        if (WITH_LOCK(pfrom.cs_avalanche_pubkey,
                      return pfrom.m_avalanche_pubkey.has_value())) {
            m_avalanche->withPeerManager(
                [&remoteProofsStatus, nodeid](avalanche::PeerManager &pm) {
                    for (const auto &[proofid, present] : remoteProofsStatus) {
                        pm.saveRemoteProof(proofid, nodeid, present);
                    }
                });
        }
 
        return;
    }
 
    if (msg_type == NetMsgType::AVAPROOFSREQ) {
        if (peer->m_proof_relay == nullptr) {
            return;
        }
 
        avalanche::ProofsRequest proofreq;
        vRecv >> proofreq;
 
        auto requestedIndiceIt = proofreq.indices.begin();
        uint32_t treeIndice = 0;
        peer->m_proof_relay->sharedProofs.forEachLeaf([&](const auto &proof) {
            if (requestedIndiceIt == proofreq.indices.end()) {
                // No more indice to process
                return false;
            }
 
            if (treeIndice++ == *requestedIndiceIt) {
                MakeAndPushMessage(pfrom, NetMsgType::AVAPROOF, *proof);
                requestedIndiceIt++;
            }
 
            return true;
        });
 
        peer->m_proof_relay->sharedProofs = {};
        return;
    }
 
    if (msg_type == NetMsgType::GETADDR) {
        // This asymmetric behavior for inbound and outbound connections was
        // introduced to prevent a fingerprinting attack: an attacker can send
        // specific fake addresses to users' AddrMan and later request them by
        // sending getaddr messages. Making nodes which are behind NAT and can
        // only make outgoing connections ignore the getaddr message mitigates
        // the attack.
        if (!pfrom.IsInboundConn()) {
            LogPrint(BCLog::NET,
                     "Ignoring \"getaddr\" from %s connection. peer=%d\n",
                     pfrom.ConnectionTypeAsString(), pfrom.GetId());
            return;
        }
 
        // Since this must be an inbound connection, SetupAddressRelay will
        // never fail.
        Assume(SetupAddressRelay(pfrom, *peer));
 
        // Only send one GetAddr response per connection to reduce resource
        // waste and discourage addr stamping of INV announcements.
        if (peer->m_getaddr_recvd) {
            LogPrint(BCLog::NET, "Ignoring repeated \"getaddr\". peer=%d\n",
                     pfrom.GetId());
            return;
        }
        peer->m_getaddr_recvd = true;
 
        peer->m_addrs_to_send.clear();
        std::vector<CAddress> vAddr;
        const size_t maxAddrToSend = m_opts.max_addr_to_send;
        if (pfrom.HasPermission(NetPermissionFlags::Addr)) {
            vAddr = m_connman.GetAddresses(maxAddrToSend, MAX_PCT_ADDR_TO_SEND,
                                           /* network */ std::nullopt);
        } else {
            vAddr = m_connman.GetAddresses(pfrom, maxAddrToSend,
                                           MAX_PCT_ADDR_TO_SEND);
        }
        for (const CAddress &addr : vAddr) {
            PushAddress(*peer, addr);
        }
        return;
    }
 
    if (msg_type == NetMsgType::GETAVAADDR) {
        auto now = GetTime<std::chrono::seconds>();
        if (now < pfrom.m_nextGetAvaAddr) {
            // Prevent a peer from exhausting our resources by spamming
            // getavaaddr messages.
            return;
        }
 
        // Only accept a getavaaddr every GETAVAADDR_INTERVAL at most
        pfrom.m_nextGetAvaAddr = now + GETAVAADDR_INTERVAL;
 
        if (!SetupAddressRelay(pfrom, *peer)) {
            LogPrint(BCLog::AVALANCHE,
                     "Ignoring getavaaddr message from %s peer=%d\n",
                     pfrom.ConnectionTypeAsString(), pfrom.GetId());
            return;
        }
 
        auto availabilityScoreComparator = [](const CNode *lhs,
                                              const CNode *rhs) {
            double scoreLhs = lhs->getAvailabilityScore();
            double scoreRhs = rhs->getAvailabilityScore();
 
            if (scoreLhs != scoreRhs) {
                return scoreLhs > scoreRhs;
            }
 
            return lhs < rhs;
        };
 
        // Get up to MAX_ADDR_TO_SEND addresses of the nodes which are the
        // most active in the avalanche network. Account for 0 availability as
        // well so we can send addresses even if we did not start polling yet.
        std::set<const CNode *, decltype(availabilityScoreComparator)> avaNodes(
            availabilityScoreComparator);
        m_connman.ForEachNode([&](const CNode *pnode) {
            if (!pnode->m_avalanche_enabled ||
                pnode->getAvailabilityScore() < 0.) {
                return;
            }
 
            avaNodes.insert(pnode);
            if (avaNodes.size() > m_opts.max_addr_to_send) {
                avaNodes.erase(std::prev(avaNodes.end()));
            }
        });
 
        peer->m_addrs_to_send.clear();
        for (const CNode *pnode : avaNodes) {
            PushAddress(*peer, pnode->addr);
        }
 
        return;
    }
 
    if (msg_type == NetMsgType::MEMPOOL) {
        if (!(peer->m_our_services & NODE_BLOOM) &&
            !pfrom.HasPermission(NetPermissionFlags::Mempool)) {
            if (!pfrom.HasPermission(NetPermissionFlags::NoBan)) {
                LogPrint(BCLog::NET,
                         "mempool request with bloom filters disabled, "
                         "disconnect peer=%d\n",
                         pfrom.GetId());
                pfrom.fDisconnect = true;
            }
            return;
        }
 
        if (m_connman.OutboundTargetReached(false) &&
            !pfrom.HasPermission(NetPermissionFlags::Mempool)) {
            if (!pfrom.HasPermission(NetPermissionFlags::NoBan)) {
                LogPrint(BCLog::NET,
                         "mempool request with bandwidth limit reached, "
                         "disconnect peer=%d\n",
                         pfrom.GetId());
                pfrom.fDisconnect = true;
            }
            return;
        }
 
        if (auto tx_relay = peer->GetTxRelay()) {
            LOCK(tx_relay->m_tx_inventory_mutex);
            tx_relay->m_send_mempool = true;
        }
        return;
    }
 
    if (msg_type == NetMsgType::PING) {
        if (pfrom.GetCommonVersion() > BIP0031_VERSION) {
            uint64_t nonce = 0;
            vRecv >> nonce;
            // Echo the message back with the nonce. This allows for two useful
            // features:
            //
            // 1) A remote node can quickly check if the connection is
            // operational.
            // 2) Remote nodes can measure the latency of the network thread. If
            // this node is overloaded it won't respond to pings quickly and the
            // remote node can avoid sending us more work, like chain download
            // requests.
            //
            // The nonce stops the remote getting confused between different
            // pings: without it, if the remote node sends a ping once per
            // second and this node takes 5 seconds to respond to each, the 5th
            // ping the remote sends would appear to return very quickly.
            MakeAndPushMessage(pfrom, NetMsgType::PONG, nonce);
        }
        return;
    }
 
    if (msg_type == NetMsgType::PONG) {
        const auto ping_end = time_received;
        uint64_t nonce = 0;
        size_t nAvail = vRecv.in_avail();
        bool bPingFinished = false;
        std::string sProblem;
 
        if (nAvail >= sizeof(nonce)) {
            vRecv >> nonce;
 
            // Only process pong message if there is an outstanding ping (old
            // ping without nonce should never pong)
            if (peer->m_ping_nonce_sent != 0) {
                if (nonce == peer->m_ping_nonce_sent) {
                    // Matching pong received, this ping is no longer
                    // outstanding
                    bPingFinished = true;
                    const auto ping_time = ping_end - peer->m_ping_start.load();
                    if (ping_time.count() >= 0) {
                        // Let connman know about this successful ping-pong
                        pfrom.PongReceived(ping_time);
                    } else {
                        // This should never happen
                        sProblem = "Timing mishap";
                    }
                } else {
                    // Nonce mismatches are normal when pings are overlapping
                    sProblem = "Nonce mismatch";
                    if (nonce == 0) {
                        // This is most likely a bug in another implementation
                        // somewhere; cancel this ping
                        bPingFinished = true;
                        sProblem = "Nonce zero";
                    }
                }
            } else {
                sProblem = "Unsolicited pong without ping";
            }
        } else {
            // This is most likely a bug in another implementation somewhere;
            // cancel this ping
            bPingFinished = true;
            sProblem = "Short payload";
        }
 
        if (!(sProblem.empty())) {
            LogPrint(BCLog::NET,
                     "pong peer=%d: %s, %x expected, %x received, %u bytes\n",
                     pfrom.GetId(), sProblem, peer->m_ping_nonce_sent, nonce,
                     nAvail);
        }
        if (bPingFinished) {
            peer->m_ping_nonce_sent = 0;
        }
        return;
    }
 
    if (msg_type == NetMsgType::FILTERLOAD) {
        if (!(peer->m_our_services & NODE_BLOOM)) {
            LogPrint(BCLog::NET,
                     "filterload received despite not offering bloom services "
                     "from peer=%d; disconnecting\n",
                     pfrom.GetId());
            pfrom.fDisconnect = true;
            return;
        }
        CBloomFilter filter;
        vRecv >> filter;
 
        if (!filter.IsWithinSizeConstraints()) {
            // There is no excuse for sending a too-large filter
            Misbehaving(*peer, "too-large bloom filter");
        } else if (auto tx_relay = peer->GetTxRelay()) {
            {
                LOCK(tx_relay->m_bloom_filter_mutex);
                tx_relay->m_bloom_filter.reset(new CBloomFilter(filter));
                tx_relay->m_relay_txs = true;
            }
            pfrom.m_bloom_filter_loaded = true;
        }
        return;
    }
 
    if (msg_type == NetMsgType::FILTERADD) {
        if (!(peer->m_our_services & NODE_BLOOM)) {
            LogPrint(BCLog::NET,
                     "filteradd received despite not offering bloom services "
                     "from peer=%d; disconnecting\n",
                     pfrom.GetId());
            pfrom.fDisconnect = true;
            return;
        }
        std::vector<uint8_t> vData;
        vRecv >> vData;
 
        // Nodes must NEVER send a data item > 520 bytes (the max size for a
        // script data object, and thus, the maximum size any matched object can
        // have) in a filteradd message.
        bool bad = false;
        if (vData.size() > MAX_SCRIPT_ELEMENT_SIZE) {
            bad = true;
        } else if (auto tx_relay = peer->GetTxRelay()) {
            LOCK(tx_relay->m_bloom_filter_mutex);
            if (tx_relay->m_bloom_filter) {
                tx_relay->m_bloom_filter->insert(vData);
            } else {
                bad = true;
            }
        }
        if (bad) {
            // The structure of this code doesn't really allow for a good error
            // code. We'll go generic.
            Misbehaving(*peer, "bad filteradd message");
        }
        return;
    }
 
    if (msg_type == NetMsgType::FILTERCLEAR) {
        if (!(peer->m_our_services & NODE_BLOOM)) {
            LogPrint(BCLog::NET,
                     "filterclear received despite not offering bloom services "
                     "from peer=%d; disconnecting\n",
                     pfrom.GetId());
            pfrom.fDisconnect = true;
            return;
        }
        auto tx_relay = peer->GetTxRelay();
        if (!tx_relay) {
            return;
        }
 
        {
            LOCK(tx_relay->m_bloom_filter_mutex);
            tx_relay->m_bloom_filter = nullptr;
            tx_relay->m_relay_txs = true;
        }
        pfrom.m_bloom_filter_loaded = false;
        pfrom.m_relays_txs = true;
        return;
    }
 
    if (msg_type == NetMsgType::FEEFILTER) {
        Amount newFeeFilter = Amount::zero();
        vRecv >> newFeeFilter;
        if (MoneyRange(newFeeFilter)) {
            if (auto tx_relay = peer->GetTxRelay()) {
                tx_relay->m_fee_filter_received = newFeeFilter;
            }
            LogPrint(BCLog::NET, "received: feefilter of %s from peer=%d\n",
                     CFeeRate(newFeeFilter).ToString(), pfrom.GetId());
        }
        return;
    }
 
    if (msg_type == NetMsgType::GETCFILTERS) {
        ProcessGetCFilters(pfrom, *peer, vRecv);
        return;
    }
 
    if (msg_type == NetMsgType::GETCFHEADERS) {
        ProcessGetCFHeaders(pfrom, *peer, vRecv);
        return;
    }
 
    if (msg_type == NetMsgType::GETCFCHECKPT) {
        ProcessGetCFCheckPt(pfrom, *peer, vRecv);
        return;
    }
 
    if (msg_type == NetMsgType::NOTFOUND) {
        std::vector<CInv> vInv;
        vRecv >> vInv;
        // A peer might send up to 1 notfound per getdata request, but no more
        if (vInv.size() <= PROOF_REQUEST_PARAMS.max_peer_announcements +
                               TX_REQUEST_PARAMS.max_peer_announcements +
                               MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
            for (CInv &inv : vInv) {
                if (inv.IsMsgTx()) {
                    // If we receive a NOTFOUND message for a tx we requested,
                    // mark the announcement for it as completed in
                    // InvRequestTracker.
                    LOCK(::cs_main);
                    m_txrequest.ReceivedResponse(pfrom.GetId(), TxId(inv.hash));
                    continue;
                }
                if (inv.IsMsgProof()) {
                    if (!m_avalanche) {
                        continue;
                    }
                    LOCK(cs_proofrequest);
                    m_proofrequest.ReceivedResponse(
                        pfrom.GetId(), avalanche::ProofId(inv.hash));
                }
            }
        }
        return;
    }
 
    // Ignore unknown commands for extensibility
    LogPrint(BCLog::NET, "Unknown command \"%s\" from peer=%d\n",
             SanitizeString(msg_type), pfrom.GetId());
    return;
}
 
bool PeerManagerImpl::MaybeDiscourageAndDisconnect(CNode &pnode, Peer &peer) {
    {
        LOCK(peer.m_misbehavior_mutex);
 
        // There's nothing to do if the m_should_discourage flag isn't set
        if (!peer.m_should_discourage) {
            return false;
        }
 
        peer.m_should_discourage = false;
    } // peer.m_misbehavior_mutex
 
    if (pnode.HasPermission(NetPermissionFlags::NoBan)) {
        // We never disconnect or discourage peers for bad behavior if they have
        // NetPermissionFlags::NoBan permission
        LogPrintf("Warning: not punishing noban peer %d!\n", peer.m_id);
        return false;
    }
 
    if (pnode.IsManualConn()) {
        // We never disconnect or discourage manual peers for bad behavior
        LogPrintf("Warning: not punishing manually connected peer %d!\n",
                  peer.m_id);
        return false;
    }
 
    if (pnode.addr.IsLocal()) {
        // We disconnect local peers for bad behavior but don't discourage
        // (since that would discourage all peers on the same local address)
        LogPrint(BCLog::NET,
                 "Warning: disconnecting but not discouraging %s peer %d!\n",
                 pnode.m_inbound_onion ? "inbound onion" : "local", peer.m_id);
        pnode.fDisconnect = true;
        return true;
    }
 
    // Normal case: Disconnect the peer and discourage all nodes sharing the
    // address
    LogPrint(BCLog::NET, "Disconnecting and discouraging peer %d!\n",
             peer.m_id);
    if (m_banman) {
        m_banman->Discourage(pnode.addr);
    }
    m_connman.DisconnectNode(pnode.addr);
    return true;
}
 
bool PeerManagerImpl::ProcessMessages(const Config &config, CNode *pfrom,
                                      std::atomic<bool> &interruptMsgProc) {
    AssertLockHeld(g_msgproc_mutex);
 
    PeerRef peer = GetPeerRef(pfrom->GetId());
    if (peer == nullptr) {
        return false;
    }
 
    {
        LOCK(peer->m_getdata_requests_mutex);
        if (!peer->m_getdata_requests.empty()) {
            ProcessGetData(config, *pfrom, *peer, interruptMsgProc);
        }
    }
 
    const bool processed_orphan = ProcessOrphanTx(config, *peer);
 
    if (pfrom->fDisconnect) {
        return false;
    }
 
    if (processed_orphan) {
        return true;
    }
 
    // this maintains the order of responses and prevents m_getdata_requests to
    // grow unbounded
    {
        LOCK(peer->m_getdata_requests_mutex);
        if (!peer->m_getdata_requests.empty()) {
            return true;
        }
    }
 
    // Don't bother if send buffer is too full to respond anyway
    if (pfrom->fPauseSend) {
        return false;
    }
 
    auto poll_result{pfrom->PollMessage()};
    if (!poll_result) {
        // No message to process
        return false;
    }
 
    CNetMessage &msg{poll_result->first};
    bool fMoreWork = poll_result->second;
 
    TRACE6(net, inbound_message, pfrom->GetId(), pfrom->m_addr_name.c_str(),
           pfrom->ConnectionTypeAsString().c_str(), msg.m_type.c_str(),
           msg.m_recv.size(), msg.m_recv.data());
 
    if (m_opts.capture_messages) {
        CaptureMessage(pfrom->addr, msg.m_type, MakeUCharSpan(msg.m_recv),
                       /*is_incoming=*/true);
    }
 
    try {
        ProcessMessage(config, *pfrom, msg.m_type, msg.m_recv, msg.m_time,
                       interruptMsgProc);
        if (interruptMsgProc) {
            return false;
        }
 
        {
            LOCK(peer->m_getdata_requests_mutex);
            if (!peer->m_getdata_requests.empty()) {
                fMoreWork = true;
            }
        }
        // Does this peer has an orphan ready to reconsider?
        // (Note: we may have provided a parent for an orphan provided by
        // another peer that was already processed; in that case, the extra work
        // may not be noticed, possibly resulting in an unnecessary 100ms delay)
        if (m_mempool.withOrphanage([&peer](TxOrphanage &orphanage) {
                return orphanage.HaveTxToReconsider(peer->m_id);
            })) {
            fMoreWork = true;
        }
    } catch (const std::exception &e) {
        LogPrint(BCLog::NET, "%s(%s, %u bytes): Exception '%s' (%s) caught\n",
                 __func__, SanitizeString(msg.m_type), msg.m_message_size,
                 e.what(), typeid(e).name());
    } catch (...) {
        LogPrint(BCLog::NET, "%s(%s, %u bytes): Unknown exception caught\n",
                 __func__, SanitizeString(msg.m_type), msg.m_message_size);
    }
 
    return fMoreWork;
}
 
void PeerManagerImpl::ConsiderEviction(CNode &pto, Peer &peer,
                                       std::chrono::seconds time_in_seconds) {
    AssertLockHeld(cs_main);
 
    CNodeState &state = *State(pto.GetId());
 
    if (!state.m_chain_sync.m_protect && pto.IsOutboundOrBlockRelayConn() &&
        state.fSyncStarted) {
        // This is an outbound peer subject to disconnection if they don't
        // announce a block with as much work as the current tip within
        // CHAIN_SYNC_TIMEOUT + HEADERS_RESPONSE_TIME seconds (note: if their
        // chain has more work than ours, we should sync to it, unless it's
        // invalid, in which case we should find that out and disconnect from
        // them elsewhere).
        if (state.pindexBestKnownBlock != nullptr &&
            state.pindexBestKnownBlock->nChainWork >=
                m_chainman.ActiveChain().Tip()->nChainWork) {
            if (state.m_chain_sync.m_timeout != 0s) {
                state.m_chain_sync.m_timeout = 0s;
                state.m_chain_sync.m_work_header = nullptr;
                state.m_chain_sync.m_sent_getheaders = false;
            }
        } else if (state.m_chain_sync.m_timeout == 0s ||
                   (state.m_chain_sync.m_work_header != nullptr &&
                    state.pindexBestKnownBlock != nullptr &&
                    state.pindexBestKnownBlock->nChainWork >=
                        state.m_chain_sync.m_work_header->nChainWork)) {
            // Our best block known by this peer is behind our tip, and we're
            // either noticing that for the first time, OR this peer was able to
            // catch up to some earlier point where we checked against our tip.
            // Either way, set a new timeout based on current tip.
            state.m_chain_sync.m_timeout = time_in_seconds + CHAIN_SYNC_TIMEOUT;
            state.m_chain_sync.m_work_header = m_chainman.ActiveChain().Tip();
            state.m_chain_sync.m_sent_getheaders = false;
        } else if (state.m_chain_sync.m_timeout > 0s &&
                   time_in_seconds > state.m_chain_sync.m_timeout) {
            // No evidence yet that our peer has synced to a chain with work
            // equal to that of our tip, when we first detected it was behind.
            // Send a single getheaders message to give the peer a chance to
            // update us.
            if (state.m_chain_sync.m_sent_getheaders) {
                // They've run out of time to catch up!
                LogPrintf(
                    "Disconnecting outbound peer %d for old chain, best known "
                    "block = %s\n",
                    pto.GetId(),
                    state.pindexBestKnownBlock != nullptr
                        ? state.pindexBestKnownBlock->GetBlockHash().ToString()
                        : "<none>");
                pto.fDisconnect = true;
            } else {
                assert(state.m_chain_sync.m_work_header);
                // Here, we assume that the getheaders message goes out,
                // because it'll either go out or be skipped because of a
                // getheaders in-flight already, in which case the peer should
                // still respond to us with a sufficiently high work chain tip.
                MaybeSendGetHeaders(
                    pto, GetLocator(state.m_chain_sync.m_work_header->pprev),
                    peer);
                LogPrint(
                    BCLog::NET,
                    "sending getheaders to outbound peer=%d to verify chain "
                    "work (current best known block:%s, benchmark blockhash: "
                    "%s)\n",
                    pto.GetId(),
                    state.pindexBestKnownBlock != nullptr
                        ? state.pindexBestKnownBlock->GetBlockHash().ToString()
                        : "<none>",
                    state.m_chain_sync.m_work_header->GetBlockHash()
                        .ToString());
                state.m_chain_sync.m_sent_getheaders = true;
                // Bump the timeout to allow a response, which could clear the
                // timeout (if the response shows the peer has synced), reset
                // the timeout (if the peer syncs to the required work but not
                // to our tip), or result in disconnect (if we advance to the
                // timeout and pindexBestKnownBlock has not sufficiently
                // progressed)
                state.m_chain_sync.m_timeout =
                    time_in_seconds + HEADERS_RESPONSE_TIME;
            }
        }
    }
}
 
void PeerManagerImpl::EvictExtraOutboundPeers(std::chrono::seconds now) {
    // If we have any extra block-relay-only peers, disconnect the youngest
    // unless it's given us a block -- in which case, compare with the
    // second-youngest, and out of those two, disconnect the peer who least
    // recently gave us a block.
    // The youngest block-relay-only peer would be the extra peer we connected
    // to temporarily in order to sync our tip; see net.cpp.
    // Note that we use higher nodeid as a measure for most recent connection.
    if (m_connman.GetExtraBlockRelayCount() > 0) {
        std::pair<NodeId, std::chrono::seconds> youngest_peer{-1, 0},
            next_youngest_peer{-1, 0};
 
        m_connman.ForEachNode([&](CNode *pnode) {
            if (!pnode->IsBlockOnlyConn() || pnode->fDisconnect) {
                return;
            }
            if (pnode->GetId() > youngest_peer.first) {
                next_youngest_peer = youngest_peer;
                youngest_peer.first = pnode->GetId();
                youngest_peer.second = pnode->m_last_block_time;
            }
        });
 
        NodeId to_disconnect = youngest_peer.first;
        if (youngest_peer.second > next_youngest_peer.second) {
            // Our newest block-relay-only peer gave us a block more recently;
            // disconnect our second youngest.
            to_disconnect = next_youngest_peer.first;
        }
 
        m_connman.ForNode(
            to_disconnect,
            [&](CNode *pnode) EXCLUSIVE_LOCKS_REQUIRED(::cs_main) {
                AssertLockHeld(::cs_main);
                // Make sure we're not getting a block right now, and that we've
                // been connected long enough for this eviction to happen at
                // all. Note that we only request blocks from a peer if we learn
                // of a valid headers chain with at least as much work as our
                // tip.
                CNodeState *node_state = State(pnode->GetId());
                if (node_state == nullptr ||
                    (now - pnode->m_connected >= MINIMUM_CONNECT_TIME &&
                     node_state->vBlocksInFlight.empty())) {
                    pnode->fDisconnect = true;
                    LogPrint(BCLog::NET,
                             "disconnecting extra block-relay-only peer=%d "
                             "(last block received at time %d)\n",
                             pnode->GetId(),
                             count_seconds(pnode->m_last_block_time));
                    return true;
                } else {
                    LogPrint(
                        BCLog::NET,
                        "keeping block-relay-only peer=%d chosen for eviction "
                        "(connect time: %d, blocks_in_flight: %d)\n",
                        pnode->GetId(), count_seconds(pnode->m_connected),
                        node_state->vBlocksInFlight.size());
                }
                return false;
            });
    }
 
    // Check whether we have too many OUTBOUND_FULL_RELAY peers
    if (m_connman.GetExtraFullOutboundCount() <= 0) {
        return;
    }
 
    // If we have more OUTBOUND_FULL_RELAY peers than we target, disconnect one.
    // Pick the OUTBOUND_FULL_RELAY peer that least recently announced us a new
    // block, with ties broken by choosing the more recent connection (higher
    // node id)
    NodeId worst_peer = -1;
    int64_t oldest_block_announcement = std::numeric_limits<int64_t>::max();
 
    m_connman.ForEachNode([&](CNode *pnode) EXCLUSIVE_LOCKS_REQUIRED(
                              ::cs_main) {
        AssertLockHeld(::cs_main);
 
        // Only consider OUTBOUND_FULL_RELAY peers that are not already marked
        // for disconnection
        if (!pnode->IsFullOutboundConn() || pnode->fDisconnect) {
            return;
        }
        CNodeState *state = State(pnode->GetId());
        if (state == nullptr) {
            // shouldn't be possible, but just in case
            return;
        }
        // Don't evict our protected peers
        if (state->m_chain_sync.m_protect) {
            return;
        }
        if (state->m_last_block_announcement < oldest_block_announcement ||
            (state->m_last_block_announcement == oldest_block_announcement &&
             pnode->GetId() > worst_peer)) {
            worst_peer = pnode->GetId();
            oldest_block_announcement = state->m_last_block_announcement;
        }
    });
 
    if (worst_peer == -1) {
        return;
    }
 
    bool disconnected = m_connman.ForNode(
        worst_peer, [&](CNode *pnode) EXCLUSIVE_LOCKS_REQUIRED(::cs_main) {
            AssertLockHeld(::cs_main);
 
            // Only disconnect a peer that has been connected to us for some
            // reasonable fraction of our check-frequency, to give it time for
            // new information to have arrived. Also don't disconnect any peer
            // we're trying to download a block from.
            CNodeState &state = *State(pnode->GetId());
            if (now - pnode->m_connected > MINIMUM_CONNECT_TIME &&
                state.vBlocksInFlight.empty()) {
                LogPrint(BCLog::NET,
                         "disconnecting extra outbound peer=%d (last block "
                         "announcement received at time %d)\n",
                         pnode->GetId(), oldest_block_announcement);
                pnode->fDisconnect = true;
                return true;
            } else {
                LogPrint(BCLog::NET,
                         "keeping outbound peer=%d chosen for eviction "
                         "(connect time: %d, blocks_in_flight: %d)\n",
                         pnode->GetId(), count_seconds(pnode->m_connected),
                         state.vBlocksInFlight.size());
                return false;
            }
        });
 
    if (disconnected) {
        // If we disconnected an extra peer, that means we successfully
        // connected to at least one peer after the last time we detected a
        // stale tip. Don't try any more extra peers until we next detect a
        // stale tip, to limit the load we put on the network from these extra
        // connections.
        m_connman.SetTryNewOutboundPeer(false);
    }
}
 
void PeerManagerImpl::CheckForStaleTipAndEvictPeers() {
    LOCK(cs_main);
 
    auto now{GetTime<std::chrono::seconds>()};
 
    EvictExtraOutboundPeers(now);
 
    if (now > m_stale_tip_check_time) {
        // Check whether our tip is stale, and if so, allow using an extra
        // outbound peer.
        if (!m_chainman.m_blockman.LoadingBlocks() &&
            m_connman.GetNetworkActive() && m_connman.GetUseAddrmanOutgoing() &&
            TipMayBeStale()) {
            LogPrintf("Potential stale tip detected, will try using extra "
                      "outbound peer (last tip update: %d seconds ago)\n",
                      count_seconds(now - m_last_tip_update.load()));
            m_connman.SetTryNewOutboundPeer(true);
        } else if (m_connman.GetTryNewOutboundPeer()) {
            m_connman.SetTryNewOutboundPeer(false);
        }
        m_stale_tip_check_time = now + STALE_CHECK_INTERVAL;
    }
 
    if (!m_initial_sync_finished && CanDirectFetch()) {
        m_connman.StartExtraBlockRelayPeers();
        m_initial_sync_finished = true;
    }
}
 
void PeerManagerImpl::MaybeSendPing(CNode &node_to, Peer &peer,
                                    std::chrono::microseconds now) {
    if (m_connman.ShouldRunInactivityChecks(
            node_to, std::chrono::duration_cast<std::chrono::seconds>(now)) &&
        peer.m_ping_nonce_sent &&
        now > peer.m_ping_start.load() + TIMEOUT_INTERVAL) {
        // The ping timeout is using mocktime. To disable the check during
        // testing, increase -peertimeout.
        LogPrint(BCLog::NET, "ping timeout: %fs peer=%d\n",
                 0.000001 * count_microseconds(now - peer.m_ping_start.load()),
                 peer.m_id);
        node_to.fDisconnect = true;
        return;
    }
 
    bool pingSend = false;
 
    if (peer.m_ping_queued) {
        // RPC ping request by user
        pingSend = true;
    }
 
    if (peer.m_ping_nonce_sent == 0 &&
        now > peer.m_ping_start.load() + PING_INTERVAL) {
        // Ping automatically sent as a latency probe & keepalive.
        pingSend = true;
    }
 
    if (pingSend) {
        uint64_t nonce;
        do {
            nonce = FastRandomContext().rand64();
        } while (nonce == 0);
        peer.m_ping_queued = false;
        peer.m_ping_start = now;
        if (node_to.GetCommonVersion() > BIP0031_VERSION) {
            peer.m_ping_nonce_sent = nonce;
            MakeAndPushMessage(node_to, NetMsgType::PING, nonce);
        } else {
            // Peer is too old to support ping command with nonce, pong will
            // never arrive.
            peer.m_ping_nonce_sent = 0;
            MakeAndPushMessage(node_to, NetMsgType::PING);
        }
    }
}
 
void PeerManagerImpl::MaybeSendAddr(CNode &node, Peer &peer,
                                    std::chrono::microseconds current_time) {
    // Nothing to do for non-address-relay peers
    if (!peer.m_addr_relay_enabled) {
        return;
    }
 
    LOCK(peer.m_addr_send_times_mutex);
    if (fListen && !m_chainman.IsInitialBlockDownload() &&
        peer.m_next_local_addr_send < current_time) {
        // If we've sent before, clear the bloom filter for the peer, so
        // that our self-announcement will actually go out. This might
        // be unnecessary if the bloom filter has already rolled over
        // since our last self-announcement, but there is only a small
        // bandwidth cost that we can incur by doing this (which happens
        // once a day on average).
        if (peer.m_next_local_addr_send != 0us) {
            peer.m_addr_known->reset();
        }
        if (std::optional<CService> local_service = GetLocalAddrForPeer(node)) {
            CAddress local_addr{*local_service, peer.m_our_services,
                                Now<NodeSeconds>()};
            PushAddress(peer, local_addr);
        }
        peer.m_next_local_addr_send =
            current_time +
            m_rng.rand_exp_duration(AVG_LOCAL_ADDRESS_BROADCAST_INTERVAL);
    }
 
    // We sent an `addr` message to this peer recently. Nothing more to do.
    if (current_time <= peer.m_next_addr_send) {
        return;
    }
 
    peer.m_next_addr_send =
        current_time + m_rng.rand_exp_duration(AVG_ADDRESS_BROADCAST_INTERVAL);
 
    const size_t max_addr_to_send = m_opts.max_addr_to_send;
    if (!Assume(peer.m_addrs_to_send.size() <= max_addr_to_send)) {
        // Should be impossible since we always check size before adding to
        // m_addrs_to_send. Recover by trimming the vector.
        peer.m_addrs_to_send.resize(max_addr_to_send);
    }
 
    // Remove addr records that the peer already knows about, and add new
    // addrs to the m_addr_known filter on the same pass.
    auto addr_already_known =
        [&peer](const CAddress &addr)
            EXCLUSIVE_LOCKS_REQUIRED(g_msgproc_mutex) {
                bool ret = peer.m_addr_known->contains(addr.GetKey());
                if (!ret) {
                    peer.m_addr_known->insert(addr.GetKey());
                }
                return ret;
            };
    peer.m_addrs_to_send.erase(std::remove_if(peer.m_addrs_to_send.begin(),
                                              peer.m_addrs_to_send.end(),
                                              addr_already_known),
                               peer.m_addrs_to_send.end());
 
    // No addr messages to send
    if (peer.m_addrs_to_send.empty()) {
        return;
    }
 
    const char *msg_type;
    CNetAddr::Encoding ser_enc;
    if (peer.m_wants_addrv2) {
        msg_type = NetMsgType::ADDRV2;
        ser_enc = CNetAddr::Encoding::V2;
    } else {
        msg_type = NetMsgType::ADDR;
        ser_enc = CNetAddr::Encoding::V1;
    }
    MakeAndPushMessage(
        node, msg_type,
        WithParams(CAddress::SerParams{{ser_enc}, CAddress::Format::Network},
                   peer.m_addrs_to_send));
    peer.m_addrs_to_send.clear();
 
    // we only send the big addr message once
    if (peer.m_addrs_to_send.capacity() > 40) {
        peer.m_addrs_to_send.shrink_to_fit();
    }
}
 
void PeerManagerImpl::MaybeSendSendHeaders(CNode &node, Peer &peer) {
    // Delay sending SENDHEADERS (BIP 130) until we're done with an
    // initial-headers-sync with this peer. Receiving headers announcements for
    // new blocks while trying to sync their headers chain is problematic,
    // because of the state tracking done.
    if (!peer.m_sent_sendheaders &&
        node.GetCommonVersion() >= SENDHEADERS_VERSION) {
        LOCK(cs_main);
        CNodeState &state = *State(node.GetId());
        if (state.pindexBestKnownBlock != nullptr &&
            state.pindexBestKnownBlock->nChainWork >
                m_chainman.MinimumChainWork()) {
            // Tell our peer we prefer to receive headers rather than inv's
            // We send this to non-NODE NETWORK peers as well, because even
            // non-NODE NETWORK peers can announce blocks (such as pruning
            // nodes)
            MakeAndPushMessage(node, NetMsgType::SENDHEADERS);
            peer.m_sent_sendheaders = true;
        }
    }
}
 
void PeerManagerImpl::MaybeSendFeefilter(
    CNode &pto, Peer &peer, std::chrono::microseconds current_time) {
    if (m_opts.ignore_incoming_txs) {
        return;
    }
    if (pto.GetCommonVersion() < FEEFILTER_VERSION) {
        return;
    }
    // peers with the forcerelay permission should not filter txs to us
    if (pto.HasPermission(NetPermissionFlags::ForceRelay)) {
        return;
    }
    // Don't send feefilter messages to outbound block-relay-only peers since
    // they should never announce transactions to us, regardless of feefilter
    // state.
    if (pto.IsBlockOnlyConn()) {
        return;
    }
 
    Amount currentFilter = m_mempool.GetMinFee().GetFeePerK();
 
    if (m_chainman.IsInitialBlockDownload()) {
        // Received tx-inv messages are discarded when the active
        // chainstate is in IBD, so tell the peer to not send them.
        currentFilter = MAX_MONEY;
    } else {
        static const Amount MAX_FILTER{m_fee_filter_rounder.round(MAX_MONEY)};
        if (peer.m_fee_filter_sent == MAX_FILTER) {
            // Send the current filter if we sent MAX_FILTER previously
            // and made it out of IBD.
            peer.m_next_send_feefilter = 0us;
        }
    }
    if (current_time > peer.m_next_send_feefilter) {
        Amount filterToSend = m_fee_filter_rounder.round(currentFilter);
        // We always have a fee filter of at least the min relay fee
        filterToSend =
            std::max(filterToSend, m_mempool.m_min_relay_feerate.GetFeePerK());
        if (filterToSend != peer.m_fee_filter_sent) {
            MakeAndPushMessage(pto, NetMsgType::FEEFILTER, filterToSend);
            peer.m_fee_filter_sent = filterToSend;
        }
        peer.m_next_send_feefilter =
            current_time +
            m_rng.rand_exp_duration(AVG_FEEFILTER_BROADCAST_INTERVAL);
    }
    // If the fee filter has changed substantially and it's still more than
    // MAX_FEEFILTER_CHANGE_DELAY until scheduled broadcast, then move the
    // broadcast to within MAX_FEEFILTER_CHANGE_DELAY.
    else if (current_time + MAX_FEEFILTER_CHANGE_DELAY <
                 peer.m_next_send_feefilter &&
             (currentFilter < 3 * peer.m_fee_filter_sent / 4 ||
              currentFilter > 4 * peer.m_fee_filter_sent / 3)) {
        peer.m_next_send_feefilter =
            current_time +
            FastRandomContext().randrange<std::chrono::microseconds>(
                MAX_FEEFILTER_CHANGE_DELAY);
    }
}
 
namespace {
class CompareInvMempoolOrder {
    CTxMemPool *mp;
 
public:
    explicit CompareInvMempoolOrder(CTxMemPool *_mempool) : mp(_mempool) {}
 
    bool operator()(std::set<TxId>::iterator a, std::set<TxId>::iterator b) {
        return mp->CompareTopologically(*b, *a);
    }
};
} // namespace
 
bool PeerManagerImpl::RejectIncomingTxs(const CNode &peer) const {
    // block-relay-only peers may never send txs to us
    if (peer.IsBlockOnlyConn()) {
        return true;
    }
    if (peer.IsFeelerConn()) {
        return true;
    }
    // In -blocksonly mode, peers need the 'relay' permission to send txs to us
    if (m_opts.ignore_incoming_txs &&
        !peer.HasPermission(NetPermissionFlags::Relay)) {
        return true;
    }
    return false;
}
 
bool PeerManagerImpl::SetupAddressRelay(const CNode &node, Peer &peer) {
    // We don't participate in addr relay with outbound block-relay-only
    // connections to prevent providing adversaries with the additional
    // information of addr traffic to infer the link.
    if (node.IsBlockOnlyConn()) {
        return false;
    }
 
    if (!peer.m_addr_relay_enabled.exchange(true)) {
        // During version message processing (non-block-relay-only outbound
        // peers) or on first addr-related message we have received (inbound
        // peers), initialize m_addr_known.
        peer.m_addr_known = std::make_unique<CRollingBloomFilter>(5000, 0.001);
    }
 
    return true;
}
 
bool PeerManagerImpl::SendMessages(const Config &config, CNode *pto) {
    AssertLockHeld(g_msgproc_mutex);
 
    PeerRef peer = GetPeerRef(pto->GetId());
    if (!peer) {
        return false;
    }
    const Consensus::Params &consensusParams = m_chainparams.GetConsensus();
 
    // We must call MaybeDiscourageAndDisconnect first, to ensure that we'll
    // disconnect misbehaving peers even before the version handshake is
    // complete.
    if (MaybeDiscourageAndDisconnect(*pto, *peer)) {
        return true;
    }
 
    // Don't send anything until the version handshake is complete
    if (!pto->fSuccessfullyConnected || pto->fDisconnect) {
        return true;
    }
 
    const auto current_time{GetTime<std::chrono::microseconds>()};
 
    if (pto->IsAddrFetchConn() &&
        current_time - pto->m_connected > 10 * AVG_ADDRESS_BROADCAST_INTERVAL) {
        LogPrint(BCLog::NET,
                 "addrfetch connection timeout; disconnecting peer=%d\n",
                 pto->GetId());
        pto->fDisconnect = true;
        return true;
    }
 
    MaybeSendPing(*pto, *peer, current_time);
 
    // MaybeSendPing may have marked peer for disconnection
    if (pto->fDisconnect) {
        return true;
    }
 
    bool sync_blocks_and_headers_from_peer = false;
 
    MaybeSendAddr(*pto, *peer, current_time);
 
    MaybeSendSendHeaders(*pto, *peer);
 
    {
        LOCK(cs_main);
 
        CNodeState &state = *State(pto->GetId());
 
        // Start block sync
        if (m_chainman.m_best_header == nullptr) {
            m_chainman.m_best_header = m_chainman.ActiveChain().Tip();
        }
 
        // Determine whether we might try initial headers sync or parallel
        // block download from this peer -- this mostly affects behavior while
        // in IBD (once out of IBD, we sync from all peers).
        if (state.fPreferredDownload) {
            sync_blocks_and_headers_from_peer = true;
        } else if (CanServeBlocks(*peer) && !pto->IsAddrFetchConn()) {
            // Typically this is an inbound peer. If we don't have any outbound
            // peers, or if we aren't downloading any blocks from such peers,
            // then allow block downloads from this peer, too.
            // We prefer downloading blocks from outbound peers to avoid
            // putting undue load on (say) some home user who is just making
            // outbound connections to the network, but if our only source of
            // the latest blocks is from an inbound peer, we have to be sure to
            // eventually download it (and not just wait indefinitely for an
            // outbound peer to have it).
            if (m_num_preferred_download_peers == 0 ||
                mapBlocksInFlight.empty()) {
                sync_blocks_and_headers_from_peer = true;
            }
        }
 
        if (!state.fSyncStarted && CanServeBlocks(*peer) &&
            !m_chainman.m_blockman.LoadingBlocks()) {
            // Only actively request headers from a single peer, unless we're
            // close to today.
            if ((nSyncStarted == 0 && sync_blocks_and_headers_from_peer) ||
                m_chainman.m_best_header->Time() > GetAdjustedTime() - 24h) {
                const CBlockIndex *pindexStart = m_chainman.m_best_header;
                if (pindexStart->pprev) {
                    pindexStart = pindexStart->pprev;
                }
                if (MaybeSendGetHeaders(*pto, GetLocator(pindexStart), *peer)) {
                    LogPrint(
                        BCLog::NET,
                        "initial getheaders (%d) to peer=%d (startheight:%d)\n",
                        pindexStart->nHeight, pto->GetId(),
                        peer->m_starting_height);
 
                    state.fSyncStarted = true;
                    peer->m_headers_sync_timeout =
                        current_time + HEADERS_DOWNLOAD_TIMEOUT_BASE +
                        (
                            // Convert HEADERS_DOWNLOAD_TIMEOUT_PER_HEADER to
                            // microseconds before scaling to maintain precision
                            std::chrono::microseconds{
                                HEADERS_DOWNLOAD_TIMEOUT_PER_HEADER} *
                            Ticks<std::chrono::seconds>(
                                GetAdjustedTime() -
                                m_chainman.m_best_header->Time()) /
                            consensusParams.nPowTargetSpacing);
                    nSyncStarted++;
                }
            }
        }
 
        //
        // Try sending block announcements via headers
        //
        {
            // If we have less than MAX_BLOCKS_TO_ANNOUNCE in our list of block
            // hashes we're relaying, and our peer wants headers announcements,
            // then find the first header not yet known to our peer but would
            // connect, and send. If no header would connect, or if we have too
            // many blocks, or if the peer doesn't want headers, just add all to
            // the inv queue.
            LOCK(peer->m_block_inv_mutex);
            std::vector<CBlock> vHeaders;
            bool fRevertToInv =
                ((!peer->m_prefers_headers &&
                  (!state.m_requested_hb_cmpctblocks ||
                   peer->m_blocks_for_headers_relay.size() > 1)) ||
                 peer->m_blocks_for_headers_relay.size() >
                     MAX_BLOCKS_TO_ANNOUNCE);
            // last header queued for delivery
            const CBlockIndex *pBestIndex = nullptr;
            // ensure pindexBestKnownBlock is up-to-date
            ProcessBlockAvailability(pto->GetId());
 
            if (!fRevertToInv) {
                bool fFoundStartingHeader = false;
                // Try to find first header that our peer doesn't have, and then
                // send all headers past that one. If we come across an headers
                // that aren't on m_chainman.ActiveChain(), give up.
                for (const BlockHash &hash : peer->m_blocks_for_headers_relay) {
                    const CBlockIndex *pindex =
                        m_chainman.m_blockman.LookupBlockIndex(hash);
                    assert(pindex);
                    if (m_chainman.ActiveChain()[pindex->nHeight] != pindex) {
                        // Bail out if we reorged away from this block
                        fRevertToInv = true;
                        break;
                    }
                    if (pBestIndex != nullptr && pindex->pprev != pBestIndex) {
                        // This means that the list of blocks to announce don't
                        // connect to each other. This shouldn't really be
                        // possible to hit during regular operation (because
                        // reorgs should take us to a chain that has some block
                        // not on the prior chain, which should be caught by the
                        // prior check), but one way this could happen is by
                        // using invalidateblock / reconsiderblock repeatedly on
                        // the tip, causing it to be added multiple times to
                        // m_blocks_for_headers_relay. Robustly deal with this
                        // rare situation by reverting to an inv.
                        fRevertToInv = true;
                        break;
                    }
                    pBestIndex = pindex;
                    if (fFoundStartingHeader) {
                        // add this to the headers message
                        vHeaders.push_back(pindex->GetBlockHeader());
                    } else if (PeerHasHeader(&state, pindex)) {
                        // Keep looking for the first new block.
                        continue;
                    } else if (pindex->pprev == nullptr ||
                               PeerHasHeader(&state, pindex->pprev)) {
                        // Peer doesn't have this header but they do have the
                        // prior one. Start sending headers.
                        fFoundStartingHeader = true;
                        vHeaders.push_back(pindex->GetBlockHeader());
                    } else {
                        // Peer doesn't have this header or the prior one --
                        // nothing will connect, so bail out.
                        fRevertToInv = true;
                        break;
                    }
                }
            }
            if (!fRevertToInv && !vHeaders.empty()) {
                if (vHeaders.size() == 1 && state.m_requested_hb_cmpctblocks) {
                    // We only send up to 1 block as header-and-ids, as
                    // otherwise probably means we're doing an initial-ish-sync
                    // or they're slow.
                    LogPrint(BCLog::NET,
                             "%s sending header-and-ids %s to peer=%d\n",
                             __func__, vHeaders.front().GetHash().ToString(),
                             pto->GetId());
 
                    std::optional<CSerializedNetMsg> cached_cmpctblock_msg;
                    {
                        LOCK(m_most_recent_block_mutex);
                        if (m_most_recent_block_hash ==
                            pBestIndex->GetBlockHash()) {
                            cached_cmpctblock_msg =
                                NetMsg::Make(NetMsgType::CMPCTBLOCK,
                                             *m_most_recent_compact_block);
                        }
                    }
                    if (cached_cmpctblock_msg.has_value()) {
                        PushMessage(*pto,
                                    std::move(cached_cmpctblock_msg.value()));
                    } else {
                        CBlock block;
                        const bool ret{m_chainman.m_blockman.ReadBlock(
                            block, *pBestIndex)};
                        assert(ret);
                        CBlockHeaderAndShortTxIDs cmpctblock(
                            block, FastRandomContext().rand64());
                        MakeAndPushMessage(*pto, NetMsgType::CMPCTBLOCK,
                                           cmpctblock);
                    }
                    state.pindexBestHeaderSent = pBestIndex;
                } else if (peer->m_prefers_headers) {
                    if (vHeaders.size() > 1) {
                        LogPrint(BCLog::NET,
                                 "%s: %u headers, range (%s, %s), to peer=%d\n",
                                 __func__, vHeaders.size(),
                                 vHeaders.front().GetHash().ToString(),
                                 vHeaders.back().GetHash().ToString(),
                                 pto->GetId());
                    } else {
                        LogPrint(BCLog::NET,
                                 "%s: sending header %s to peer=%d\n", __func__,
                                 vHeaders.front().GetHash().ToString(),
                                 pto->GetId());
                    }
                    MakeAndPushMessage(*pto, NetMsgType::HEADERS, vHeaders);
                    state.pindexBestHeaderSent = pBestIndex;
                } else {
                    fRevertToInv = true;
                }
            }
            if (fRevertToInv) {
                // If falling back to using an inv, just try to inv the tip. The
                // last entry in m_blocks_for_headers_relay was our tip at some
                // point in the past.
                if (!peer->m_blocks_for_headers_relay.empty()) {
                    const BlockHash &hashToAnnounce =
                        peer->m_blocks_for_headers_relay.back();
                    const CBlockIndex *pindex =
                        m_chainman.m_blockman.LookupBlockIndex(hashToAnnounce);
                    assert(pindex);
 
                    // Warn if we're announcing a block that is not on the main
                    // chain. This should be very rare and could be optimized
                    // out. Just log for now.
                    if (m_chainman.ActiveChain()[pindex->nHeight] != pindex) {
                        LogPrint(
                            BCLog::NET,
                            "Announcing block %s not on main chain (tip=%s)\n",
                            hashToAnnounce.ToString(),
                            m_chainman.ActiveChain()
                                .Tip()
                                ->GetBlockHash()
                                .ToString());
                    }
 
                    // If the peer's chain has this block, don't inv it back.
                    if (!PeerHasHeader(&state, pindex)) {
                        peer->m_blocks_for_inv_relay.push_back(hashToAnnounce);
                        LogPrint(BCLog::NET,
                                 "%s: sending inv peer=%d hash=%s\n", __func__,
                                 pto->GetId(), hashToAnnounce.ToString());
                    }
                }
            }
            peer->m_blocks_for_headers_relay.clear();
        }
    } // release cs_main
 
    //
    // Message: inventory
    //
    std::vector<CInv> vInv;
    auto addInvAndMaybeFlush = [&](uint32_t type, const uint256 &hash) {
        vInv.emplace_back(type, hash);
        if (vInv.size() == MAX_INV_SZ) {
            MakeAndPushMessage(*pto, NetMsgType::INV, std::move(vInv));
            vInv.clear();
        }
    };
 
    {
        LOCK(cs_main);
 
        {
            LOCK(peer->m_block_inv_mutex);
 
            vInv.reserve(std::max<size_t>(peer->m_blocks_for_inv_relay.size(),
                                          INVENTORY_BROADCAST_MAX_PER_MB *
                                              config.GetMaxBlockSize() /
                                              1000000));
 
            // Add blocks
            for (const BlockHash &hash : peer->m_blocks_for_inv_relay) {
                addInvAndMaybeFlush(MSG_BLOCK, hash);
            }
            peer->m_blocks_for_inv_relay.clear();
        }
 
        auto computeNextInvSendTime =
            [&](std::chrono::microseconds &next)
                EXCLUSIVE_LOCKS_REQUIRED(g_msgproc_mutex) -> bool {
            bool fSendTrickle = pto->HasPermission(NetPermissionFlags::NoBan);
 
            if (next < current_time) {
                fSendTrickle = true;
                if (pto->IsInboundConn()) {
                    next = NextInvToInbounds(
                        current_time, INBOUND_INVENTORY_BROADCAST_INTERVAL);
                } else {
                    // Skip delay for outbound peers, as there is less privacy
                    // concern for them.
                    next = current_time;
                }
            }
 
            return fSendTrickle;
        };
 
        // Add proofs to inventory
        if (peer->m_proof_relay != nullptr) {
            LOCK(peer->m_proof_relay->m_proof_inventory_mutex);
 
            if (computeNextInvSendTime(
                    peer->m_proof_relay->m_next_inv_send_time)) {
                auto it =
                    peer->m_proof_relay->m_proof_inventory_to_send.begin();
                while (it !=
                       peer->m_proof_relay->m_proof_inventory_to_send.end()) {
                    const avalanche::ProofId proofid = *it;
 
                    it = peer->m_proof_relay->m_proof_inventory_to_send.erase(
                        it);
 
                    if (peer->m_proof_relay->m_proof_inventory_known_filter
                            .contains(proofid)) {
                        continue;
                    }
 
                    peer->m_proof_relay->m_proof_inventory_known_filter.insert(
                        proofid);
                    addInvAndMaybeFlush(MSG_AVA_PROOF, proofid);
                    peer->m_proof_relay->m_recently_announced_proofs.insert(
                        proofid);
                }
            }
        }
 
        if (auto tx_relay = peer->GetTxRelay()) {
            LOCK(tx_relay->m_tx_inventory_mutex);
            // Check whether periodic sends should happen
            const bool fSendTrickle =
                computeNextInvSendTime(tx_relay->m_next_inv_send_time);
 
            // Time to send but the peer has requested we not relay
            // transactions.
            if (fSendTrickle) {
                LOCK(tx_relay->m_bloom_filter_mutex);
                if (!tx_relay->m_relay_txs) {
                    tx_relay->m_tx_inventory_to_send.clear();
                }
            }
 
            // Respond to BIP35 mempool requests
            if (fSendTrickle && tx_relay->m_send_mempool) {
                auto vtxinfo = m_mempool.infoAll();
                tx_relay->m_send_mempool = false;
                const CFeeRate filterrate{
                    tx_relay->m_fee_filter_received.load()};
 
                LOCK(tx_relay->m_bloom_filter_mutex);
 
                for (const auto &txinfo : vtxinfo) {
                    const TxId &txid = txinfo.tx->GetId();
                    tx_relay->m_tx_inventory_to_send.erase(txid);
                    // Don't send transactions that peers will not put into
                    // their mempool
                    if (txinfo.fee < filterrate.GetFee(txinfo.vsize)) {
                        continue;
                    }
                    if (tx_relay->m_bloom_filter &&
                        !tx_relay->m_bloom_filter->IsRelevantAndUpdate(
                            *txinfo.tx)) {
                        continue;
                    }
                    tx_relay->m_tx_inventory_known_filter.insert(txid);
                    // Responses to MEMPOOL requests bypass the
                    // m_recently_announced_invs filter.
                    addInvAndMaybeFlush(MSG_TX, txid);
                }
                tx_relay->m_last_mempool_req =
                    std::chrono::duration_cast<std::chrono::seconds>(
                        current_time);
            }
 
            // Determine transactions to relay
            if (fSendTrickle) {
                // Produce a vector with all candidates for sending
                std::vector<std::set<TxId>::iterator> vInvTx;
                vInvTx.reserve(tx_relay->m_tx_inventory_to_send.size());
                for (std::set<TxId>::iterator it =
                         tx_relay->m_tx_inventory_to_send.begin();
                     it != tx_relay->m_tx_inventory_to_send.end(); it++) {
                    vInvTx.push_back(it);
                }
                const CFeeRate filterrate{
                    tx_relay->m_fee_filter_received.load()};
                // Send out the inventory in the order of admission to our
                // mempool, which is guaranteed to be a topological sort order.
                // A heap is used so that not all items need sorting if only a
                // few are being sent.
                CompareInvMempoolOrder compareInvMempoolOrder(&m_mempool);
                std::make_heap(vInvTx.begin(), vInvTx.end(),
                               compareInvMempoolOrder);
                // No reason to drain out at many times the network's
                // capacity, especially since we have many peers and some
                // will draw much shorter delays.
                unsigned int nRelayedTransactions = 0;
                LOCK(tx_relay->m_bloom_filter_mutex);
                while (!vInvTx.empty() &&
                       nRelayedTransactions < INVENTORY_BROADCAST_MAX_PER_MB *
                                                  config.GetMaxBlockSize() /
                                                  1000000) {
                    // Fetch the top element from the heap
                    std::pop_heap(vInvTx.begin(), vInvTx.end(),
                                  compareInvMempoolOrder);
                    std::set<TxId>::iterator it = vInvTx.back();
                    vInvTx.pop_back();
                    const TxId txid = *it;
                    // Remove it from the to-be-sent set
                    tx_relay->m_tx_inventory_to_send.erase(it);
                    // Check if not in the filter already
                    if (tx_relay->m_tx_inventory_known_filter.contains(txid) &&
                        tx_relay->m_avalanche_stalled_txids.count(txid) == 0) {
                        continue;
                    }
                    // Not in the mempool anymore? don't bother sending it.
                    auto txinfo = m_mempool.info(txid);
                    if (!txinfo.tx) {
                        continue;
                    }
                    // Peer told you to not send transactions at that
                    // feerate? Don't bother sending it.
                    if (txinfo.fee < filterrate.GetFee(txinfo.vsize)) {
                        continue;
                    }
                    if (tx_relay->m_bloom_filter &&
                        !tx_relay->m_bloom_filter->IsRelevantAndUpdate(
                            *txinfo.tx)) {
                        continue;
                    }
                    // Send
                    tx_relay->m_recently_announced_invs.insert(txid);
                    addInvAndMaybeFlush(MSG_TX, txid);
                    nRelayedTransactions++;
                    tx_relay->m_tx_inventory_known_filter.insert(txid);
                    tx_relay->m_avalanche_stalled_txids.erase(txid);
                }
            }
        }
    } // release cs_main
 
    if (!vInv.empty()) {
        MakeAndPushMessage(*pto, NetMsgType::INV, vInv);
    }
 
    {
        LOCK(cs_main);
 
        CNodeState &state = *State(pto->GetId());
 
        // Detect whether we're stalling
        auto stalling_timeout = m_block_stalling_timeout.load();
        if (state.m_stalling_since.count() &&
            state.m_stalling_since < current_time - stalling_timeout) {
            // Stalling only triggers when the block download window cannot
            // move. During normal steady state, the download window should be
            // much larger than the to-be-downloaded set of blocks, so
            // disconnection should only happen during initial block download.
            LogPrintf("Peer=%d is stalling block download, disconnecting\n",
                      pto->GetId());
            pto->fDisconnect = true;
            // Increase timeout for the next peer so that we don't disconnect
            // multiple peers if our own bandwidth is insufficient.
            const auto new_timeout =
                std::min(2 * stalling_timeout, BLOCK_STALLING_TIMEOUT_MAX);
            if (stalling_timeout != new_timeout &&
                m_block_stalling_timeout.compare_exchange_strong(
                    stalling_timeout, new_timeout)) {
                LogPrint(
                    BCLog::NET,
                    "Increased stalling timeout temporarily to %d seconds\n",
                    count_seconds(new_timeout));
            }
            return true;
        }
        // In case there is a block that has been in flight from this peer for
        // block_interval * (1 + 0.5 * N) (with N the number of peers from which
        // we're downloading validated blocks), disconnect due to timeout.
        // We compensate for other peers to prevent killing off peers due to our
        // own downstream link being saturated. We only count validated
        // in-flight blocks so peers can't advertise non-existing block hashes
        // to unreasonably increase our timeout.
        if (state.vBlocksInFlight.size() > 0) {
            QueuedBlock &queuedBlock = state.vBlocksInFlight.front();
            int nOtherPeersWithValidatedDownloads =
                m_peers_downloading_from - 1;
            if (current_time >
                state.m_downloading_since +
                    std::chrono::seconds{consensusParams.nPowTargetSpacing} *
                        (BLOCK_DOWNLOAD_TIMEOUT_BASE +
                         BLOCK_DOWNLOAD_TIMEOUT_PER_PEER *
                             nOtherPeersWithValidatedDownloads)) {
                LogPrintf("Timeout downloading block %s from peer=%d, "
                          "disconnecting\n",
                          queuedBlock.pindex->GetBlockHash().ToString(),
                          pto->GetId());
                pto->fDisconnect = true;
                return true;
            }
        }
 
        // Check for headers sync timeouts
        if (state.fSyncStarted &&
            peer->m_headers_sync_timeout < std::chrono::microseconds::max()) {
            // Detect whether this is a stalling initial-headers-sync peer
            if (m_chainman.m_best_header->Time() <= GetAdjustedTime() - 24h) {
                if (current_time > peer->m_headers_sync_timeout &&
                    nSyncStarted == 1 &&
                    (m_num_preferred_download_peers -
                         state.fPreferredDownload >=
                     1)) {
                    // Disconnect a peer (without NetPermissionFlags::NoBan
                    // permission) if it is our only sync peer, and we have
                    // others we could be using instead. Note: If all our peers
                    // are inbound, then we won't disconnect our sync peer for
                    // stalling; we have bigger problems if we can't get any
                    // outbound peers.
                    if (!pto->HasPermission(NetPermissionFlags::NoBan)) {
                        LogPrintf("Timeout downloading headers from peer=%d, "
                                  "disconnecting\n",
                                  pto->GetId());
                        pto->fDisconnect = true;
                        return true;
                    } else {
                        LogPrintf("Timeout downloading headers from noban "
                                  "peer=%d, not disconnecting\n",
                                  pto->GetId());
                        // Reset the headers sync state so that we have a chance
                        // to try downloading from a different peer. Note: this
                        // will also result in at least one more getheaders
                        // message to be sent to this peer (eventually).
                        state.fSyncStarted = false;
                        nSyncStarted--;
                        peer->m_headers_sync_timeout = 0us;
                    }
                }
            } else {
                // After we've caught up once, reset the timeout so we can't
                // trigger disconnect later.
                peer->m_headers_sync_timeout = std::chrono::microseconds::max();
            }
        }
 
        // Check that outbound peers have reasonable chains GetTime() is used by
        // this anti-DoS logic so we can test this using mocktime.
        ConsiderEviction(*pto, *peer, GetTime<std::chrono::seconds>());
    } // release cs_main
 
    std::vector<CInv> vGetData;
 
    //
    // Message: getdata (blocks)
    //
    {
        LOCK(cs_main);
 
        CNodeState &state = *State(pto->GetId());
 
        if (CanServeBlocks(*peer) &&
            ((sync_blocks_and_headers_from_peer && !IsLimitedPeer(*peer)) ||
             !m_chainman.IsInitialBlockDownload()) &&
            state.vBlocksInFlight.size() < MAX_BLOCKS_IN_TRANSIT_PER_PEER) {
            std::vector<const CBlockIndex *> vToDownload;
            NodeId staller = -1;
            auto get_inflight_budget = [&state]() {
                return std::max(
                    0, MAX_BLOCKS_IN_TRANSIT_PER_PEER -
                           static_cast<int>(state.vBlocksInFlight.size()));
            };
 
            // If a snapshot chainstate is in use, we want to find its next
            // blocks before the background chainstate to prioritize getting to
            // network tip.
            FindNextBlocksToDownload(*peer, get_inflight_budget(), vToDownload,
                                     staller);
            if (m_chainman.BackgroundSyncInProgress() &&
                !IsLimitedPeer(*peer)) {
                // If the background tip is not an ancestor of the snapshot
                // block, we need to start requesting blocks from their last
                // common ancestor.
                const CBlockIndex *from_tip =
                    LastCommonAncestor(m_chainman.GetBackgroundSyncTip(),
                                       m_chainman.GetSnapshotBaseBlock());
 
                TryDownloadingHistoricalBlocks(
                    *peer, get_inflight_budget(), vToDownload, from_tip,
                    Assert(m_chainman.GetSnapshotBaseBlock()));
            }
            for (const CBlockIndex *pindex : vToDownload) {
                vGetData.push_back(CInv(MSG_BLOCK, pindex->GetBlockHash()));
                BlockRequested(config, pto->GetId(), *pindex);
                LogPrint(BCLog::NET, "Requesting block %s (%d) peer=%d\n",
                         pindex->GetBlockHash().ToString(), pindex->nHeight,
                         pto->GetId());
            }
            if (state.vBlocksInFlight.empty() && staller != -1) {
                if (State(staller)->m_stalling_since == 0us) {
                    State(staller)->m_stalling_since = current_time;
                    LogPrint(BCLog::NET, "Stall started peer=%d\n", staller);
                }
            }
        }
    } // release cs_main
 
    auto addGetDataAndMaybeFlush = [&](uint32_t type, const uint256 &hash) {
        CInv inv(type, hash);
        LogPrint(BCLog::NET, "Requesting %s from peer=%d\n", inv.ToString(),
                 pto->GetId());
        vGetData.push_back(std::move(inv));
        if (vGetData.size() >= MAX_GETDATA_SZ) {
            MakeAndPushMessage(*pto, NetMsgType::GETDATA, std::move(vGetData));
            vGetData.clear();
        }
    };
 
    //
    // Message: getdata (proof)
    //
    if (m_avalanche) {
        LOCK(cs_proofrequest);
        std::vector<std::pair<NodeId, avalanche::ProofId>> expired;
        auto requestable =
            m_proofrequest.GetRequestable(pto->GetId(), current_time, &expired);
        for (const auto &entry : expired) {
            LogPrint(BCLog::AVALANCHE,
                     "timeout of inflight proof %s from peer=%d\n",
                     entry.second.ToString(), entry.first);
        }
        for (const auto &proofid : requestable) {
            if (!AlreadyHaveProof(proofid)) {
                addGetDataAndMaybeFlush(MSG_AVA_PROOF, proofid);
                m_proofrequest.RequestedData(
                    pto->GetId(), proofid,
                    current_time + PROOF_REQUEST_PARAMS.getdata_interval);
            } else {
                // We have already seen this proof, no need to download.
                // This is just a belt-and-suspenders, as this should
                // already be called whenever a proof becomes
                // AlreadyHaveProof().
                m_proofrequest.ForgetInvId(proofid);
            }
        }
    }
 
    //
    // Message: getdata (transactions)
    //
    {
        LOCK(cs_main);
        std::vector<std::pair<NodeId, TxId>> expired;
        auto requestable =
            m_txrequest.GetRequestable(pto->GetId(), current_time, &expired);
        for (const auto &entry : expired) {
            LogPrint(BCLog::NET, "timeout of inflight tx %s from peer=%d\n",
                     entry.second.ToString(), entry.first);
        }
        for (const TxId &txid : requestable) {
            // Exclude m_recent_rejects_package_reconsiderable: we may be
            // requesting a missing parent that was previously rejected for
            // being too low feerate.
            if (!AlreadyHaveTx(txid, /*include_reconsiderable=*/false)) {
                addGetDataAndMaybeFlush(MSG_TX, txid);
                m_txrequest.RequestedData(
                    pto->GetId(), txid,
                    current_time + TX_REQUEST_PARAMS.getdata_interval);
            } else {
                // We have already seen this transaction, no need to download.
                // This is just a belt-and-suspenders, as this should already be
                // called whenever a transaction becomes AlreadyHaveTx().
                m_txrequest.ForgetInvId(txid);
            }
        }
 
        if (!vGetData.empty()) {
            MakeAndPushMessage(*pto, NetMsgType::GETDATA, vGetData);
        }
 
    } // release cs_main
    MaybeSendFeefilter(*pto, *peer, current_time);
    return true;
}
 
bool PeerManagerImpl::ReceivedAvalancheProof(CNode &node, Peer &peer,
                                             const avalanche::ProofRef &proof) {
    assert(proof != nullptr);
 
    const avalanche::ProofId &proofid = proof->getId();
 
    AddKnownProof(peer, proofid);
 
    if (m_chainman.IsInitialBlockDownload()) {
        // We cannot reliably verify proofs during IBD, so bail out early and
        // keep the inventory as pending so it can be requested when the node
        // has synced.
        return true;
    }
 
    const NodeId nodeid = node.GetId();
 
    const bool isStaker = WITH_LOCK(node.cs_avalanche_pubkey,
                                    return node.m_avalanche_pubkey.has_value());
    auto saveProofIfStaker = [this, isStaker](const CNode &node,
                                              const avalanche::ProofId &proofid,
                                              const NodeId nodeid) -> bool {
        if (isStaker) {
            return m_avalanche->withPeerManager(
                [&](avalanche::PeerManager &pm) {
                    return pm.saveRemoteProof(proofid, nodeid, true);
                });
        }
 
        return false;
    };
 
    {
        LOCK(cs_proofrequest);
        m_proofrequest.ReceivedResponse(nodeid, proofid);
 
        if (AlreadyHaveProof(proofid)) {
            m_proofrequest.ForgetInvId(proofid);
            saveProofIfStaker(node, proofid, nodeid);
            return true;
        }
    }
 
    // registerProof should not be called while cs_proofrequest because it
    // holds cs_main and that creates a potential deadlock during shutdown
 
    avalanche::ProofRegistrationState state;
    if (m_avalanche->withPeerManager([&](avalanche::PeerManager &pm) {
            return pm.registerProof(proof, state);
        })) {
        WITH_LOCK(cs_proofrequest, m_proofrequest.ForgetInvId(proofid));
        RelayProof(proofid);
 
        node.m_last_proof_time = GetTime<std::chrono::seconds>();
 
        LogPrint(BCLog::NET, "New avalanche proof: peer=%d, proofid %s\n",
                 nodeid, proofid.ToString());
    }
 
    if (state.GetResult() == avalanche::ProofRegistrationResult::INVALID) {
        m_avalanche->withPeerManager(
            [&](avalanche::PeerManager &pm) { pm.setInvalid(proofid); });
        Misbehaving(peer, state.GetRejectReason());
        return false;
    }
 
    if (state.GetResult() == avalanche::ProofRegistrationResult::MISSING_UTXO) {
        // This is possible that a proof contains a utxo we don't know yet, so
        // don't ban for this.
        return false;
    }
 
    // Unlike other reasons we can expect lots of peers to send a proof that we
    // have dangling. In this case we don't want to print a lot of useless debug
    // message, the proof will be polled as soon as it's considered again.
    if (!m_avalanche->reconcileOrFinalize(proof) &&
        state.GetResult() != avalanche::ProofRegistrationResult::DANGLING) {
        LogPrint(BCLog::AVALANCHE,
                 "Not polling the avalanche proof (%s): peer=%d, proofid %s\n",
                 state.IsValid() ? "not-worth-polling"
                                 : state.GetRejectReason(),
                 nodeid, proofid.ToString());
    }
 
    saveProofIfStaker(node, proofid, nodeid);
    return true;
}