sock.cpp

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// Copyright (c) 2020-2021 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 <util/sock.h>
 
#include <common/system.h>
#include <compat.h>
#include <logging.h>
#include <threadinterrupt.h>
#include <tinyformat.h>
#include <util/syserror.h>
#include <util/time.h>
 
#include <codecvt>
#include <cwchar>
#include <locale>
#include <memory>
#include <stdexcept>
#include <string>
 
#ifdef USE_POLL
#include <poll.h>
#endif
 
static inline bool IOErrorIsPermanent(int err) {
    return err != WSAEAGAIN && err != WSAEINTR && err != WSAEWOULDBLOCK &&
           err != WSAEINPROGRESS;
}
 
Sock::Sock() : m_socket(INVALID_SOCKET) {}
 
Sock::Sock(SOCKET s) : m_socket(s) {}
 
Sock::Sock(Sock &&other) {
    m_socket = other.m_socket;
    other.m_socket = INVALID_SOCKET;
}
 
Sock::~Sock() {
    Reset();
}
 
Sock &Sock::operator=(Sock &&other) {
    Reset();
    m_socket = other.m_socket;
    other.m_socket = INVALID_SOCKET;
    return *this;
}
 
SOCKET Sock::Get() const {
    return m_socket;
}
 
SOCKET Sock::Release() {
    const SOCKET s = m_socket;
    m_socket = INVALID_SOCKET;
    return s;
}
 
void Sock::Reset() {
    CloseSocket(m_socket);
}
 
ssize_t Sock::Send(const void *data, size_t len, int flags) const {
    return send(m_socket, static_cast<const char *>(data), len, flags);
}
 
ssize_t Sock::Recv(void *buf, size_t len, int flags) const {
    return recv(m_socket, static_cast<char *>(buf), len, flags);
}
 
int Sock::Connect(const sockaddr *addr, socklen_t addr_len) const {
    return connect(m_socket, addr, addr_len);
}
 
std::unique_ptr<Sock> Sock::Accept(sockaddr *addr, socklen_t *addr_len) const {
#ifdef WIN32
    static constexpr auto err = INVALID_SOCKET;
#else
    static constexpr auto err = SOCKET_ERROR;
#endif
 
    std::unique_ptr<Sock> sock;
 
    const auto socket = accept(m_socket, addr, addr_len);
    if (socket != err) {
        try {
            sock = std::make_unique<Sock>(socket);
        } catch (const std::exception &) {
#ifdef WIN32
            closesocket(socket);
#else
            close(socket);
#endif
        }
    }
 
    return sock;
}
 
int Sock::GetSockOpt(int level, int opt_name, void *opt_val,
                     socklen_t *opt_len) const {
    return getsockopt(m_socket, level, opt_name, static_cast<char *>(opt_val),
                      opt_len);
}
 
bool Sock::Wait(std::chrono::milliseconds timeout, Event requested,
                Event *occurred) const {
    // We need a `shared_ptr` owning `this` for `WaitMany()`, but don't want
    // `this` to be destroyed when the `shared_ptr` goes out of scope at the
    // end of this function. Create it with a custom noop deleter.
    std::shared_ptr<const Sock> shared{this, [](const Sock *) {}};
 
    EventsPerSock events_per_sock{std::make_pair(shared, Events{requested})};
 
    if (!WaitMany(timeout, events_per_sock)) {
        return false;
    }
 
    if (occurred != nullptr) {
        *occurred = events_per_sock.begin()->second.occurred;
    }
 
    return true;
}
 
bool Sock::WaitMany(std::chrono::milliseconds timeout,
                    EventsPerSock &events_per_sock) const {
#ifdef USE_POLL
    std::vector<pollfd> pfds;
    for (const auto &[sock, events] : events_per_sock) {
        pfds.emplace_back();
        auto &pfd = pfds.back();
        pfd.fd = sock->m_socket;
        if (events.requested & RECV) {
            pfd.events |= POLLIN;
        }
        if (events.requested & SEND) {
            pfd.events |= POLLOUT;
        }
    }
 
    if (poll(pfds.data(), pfds.size(), count_milliseconds(timeout)) ==
        SOCKET_ERROR) {
        return false;
    }
 
    assert(pfds.size() == events_per_sock.size());
    size_t i{0};
    for (auto &[sock, events] : events_per_sock) {
        assert(sock->m_socket == static_cast<SOCKET>(pfds[i].fd));
        events.occurred = 0;
        if (pfds[i].revents & POLLIN) {
            events.occurred |= RECV;
        }
        if (pfds[i].revents & POLLOUT) {
            events.occurred |= SEND;
        }
        if (pfds[i].revents & (POLLERR | POLLHUP)) {
            events.occurred |= ERR;
        }
        ++i;
    }
 
    return true;
#else
    fd_set recv;
    fd_set send;
    fd_set err;
    FD_ZERO(&recv);
    FD_ZERO(&send);
    FD_ZERO(&err);
    SOCKET socket_max{0};
 
    for (const auto &[sock, events] : events_per_sock) {
        const auto &s = sock->m_socket;
        if (!IsSelectableSocket(s)) {
            return false;
        }
        if (events.requested & RECV) {
            FD_SET(s, &recv);
        }
        if (events.requested & SEND) {
            FD_SET(s, &send);
        }
        FD_SET(s, &err);
        socket_max = std::max(socket_max, s);
    }
 
    timeval tv = MillisToTimeval(timeout);
 
    if (select(socket_max + 1, &recv, &send, &err, &tv) == SOCKET_ERROR) {
        return false;
    }
 
    for (auto &[sock, events] : events_per_sock) {
        const auto &s = sock->m_socket;
        events.occurred = 0;
        if (FD_ISSET(s, &recv)) {
            events.occurred |= RECV;
        }
        if (FD_ISSET(s, &send)) {
            events.occurred |= SEND;
        }
        if (FD_ISSET(s, &err)) {
            events.occurred |= ERR;
        }
    }
 
    return true;
#endif /* USE_POLL */
}
 
void Sock::SendComplete(const std::string &data,
                        std::chrono::milliseconds timeout,
                        CThreadInterrupt &interrupt) const {
    const auto deadline = GetTime<std::chrono::milliseconds>() + timeout;
    size_t sent{0};
 
    for (;;) {
        const ssize_t ret{
            Send(data.data() + sent, data.size() - sent, MSG_NOSIGNAL)};
 
        if (ret > 0) {
            sent += static_cast<size_t>(ret);
            if (sent == data.size()) {
                break;
            }
        } else {
            const int err{WSAGetLastError()};
            if (IOErrorIsPermanent(err)) {
                throw std::runtime_error(
                    strprintf("send(): %s", NetworkErrorString(err)));
            }
        }
 
        const auto now = GetTime<std::chrono::milliseconds>();
 
        if (now >= deadline) {
            throw std::runtime_error(
                strprintf("Send timeout (sent only %u of %u bytes before that)",
                          sent, data.size()));
        }
 
        if (interrupt) {
            throw std::runtime_error(strprintf(
                "Send interrupted (sent only %u of %u bytes before that)", sent,
                data.size()));
        }
 
        // Wait for a short while (or the socket to become ready for sending)
        // before retrying if nothing was sent.
        const auto wait_time = std::min(
            deadline - now, std::chrono::milliseconds{MAX_WAIT_FOR_IO});
        Wait(wait_time, SEND);
    }
}
 
std::string Sock::RecvUntilTerminator(uint8_t terminator,
                                      std::chrono::milliseconds timeout,
                                      CThreadInterrupt &interrupt,
                                      size_t max_data) const {
    const auto deadline = GetTime<std::chrono::milliseconds>() + timeout;
    std::string data;
    bool terminator_found{false};
 
    // We must not consume any bytes past the terminator from the socket.
    // One option is to read one byte at a time and check if we have read a
    // terminator. However that is very slow. Instead, we peek at what is in the
    // socket and only read as many bytes as possible without crossing the
    // terminator. Reading 64 MiB of random data with 262526 terminator chars
    // takes 37 seconds to read one byte at a time VS 0.71 seconds with the
    // "peek" solution below. Reading one byte at a time is about 50 times
    // slower.
 
    for (;;) {
        if (data.size() >= max_data) {
            throw std::runtime_error(
                strprintf("Received too many bytes without a terminator (%u)",
                          data.size()));
        }
 
        char buf[512];
 
        const ssize_t peek_ret{
            Recv(buf, std::min(sizeof(buf), max_data - data.size()), MSG_PEEK)};
 
        switch (peek_ret) {
            case -1: {
                const int err{WSAGetLastError()};
                if (IOErrorIsPermanent(err)) {
                    throw std::runtime_error(
                        strprintf("recv(): %s", NetworkErrorString(err)));
                }
                break;
            }
            case 0:
                throw std::runtime_error(
                    "Connection unexpectedly closed by peer");
            default:
                auto end = buf + peek_ret;
                auto terminator_pos = std::find(buf, end, terminator);
                terminator_found = terminator_pos != end;
 
                const size_t try_len{terminator_found
                                         ? terminator_pos - buf + 1
                                         : static_cast<size_t>(peek_ret)};
 
                const ssize_t read_ret{Recv(buf, try_len, 0)};
 
                if (read_ret < 0 || static_cast<size_t>(read_ret) != try_len) {
                    throw std::runtime_error(
                        strprintf("recv() returned %u bytes on attempt to read "
                                  "%u bytes but previous "
                                  "peek claimed %u bytes are available",
                                  read_ret, try_len, peek_ret));
                }
 
                // Don't include the terminator in the output.
                const size_t append_len{terminator_found ? try_len - 1
                                                         : try_len};
 
                data.append(buf, buf + append_len);
 
                if (terminator_found) {
                    return data;
                }
        }
 
        const auto now = GetTime<std::chrono::milliseconds>();
 
        if (now >= deadline) {
            throw std::runtime_error(
                strprintf("Receive timeout (received %u bytes without "
                          "terminator before that)",
                          data.size()));
        }
 
        if (interrupt) {
            throw std::runtime_error(
                strprintf("Receive interrupted (received %u bytes without "
                          "terminator before that)",
                          data.size()));
        }
 
        // Wait for a short while (or the socket to become ready for reading)
        // before retrying.
        const auto wait_time = std::min(
            deadline - now, std::chrono::milliseconds{MAX_WAIT_FOR_IO});
        Wait(wait_time, RECV);
    }
}
 
bool Sock::IsConnected(std::string &errmsg) const {
    if (m_socket == INVALID_SOCKET) {
        errmsg = "not connected";
        return false;
    }
 
    char c;
    switch (Recv(&c, sizeof(c), MSG_PEEK)) {
        case -1: {
            const int err = WSAGetLastError();
            if (IOErrorIsPermanent(err)) {
                errmsg = NetworkErrorString(err);
                return false;
            }
            return true;
        }
        case 0:
            errmsg = "closed";
            return false;
        default:
            return true;
    }
}
 
#ifdef WIN32
std::string NetworkErrorString(int err) {
    wchar_t buf[256];
    buf[0] = 0;
    if (FormatMessageW(FORMAT_MESSAGE_FROM_SYSTEM |
                           FORMAT_MESSAGE_IGNORE_INSERTS |
                           FORMAT_MESSAGE_MAX_WIDTH_MASK,
                       nullptr, err, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
                       buf, ARRAYSIZE(buf), nullptr)) {
        return strprintf(
            "%s (%d)",
            std::wstring_convert<std::codecvt_utf8_utf16<wchar_t>, wchar_t>()
                .to_bytes(buf),
            err);
    } else {
        return strprintf("Unknown error (%d)", err);
    }
}
#else
std::string NetworkErrorString(int err) {
    // On BSD sockets implementations, NetworkErrorString is the same as
    // SysErrorString.
    return SysErrorString(err);
}
#endif
 
bool CloseSocket(SOCKET &hSocket) {
    if (hSocket == INVALID_SOCKET) {
        return false;
    }
#ifdef WIN32
    int ret = closesocket(hSocket);
#else
    int ret = close(hSocket);
#endif
    if (ret) {
        LogPrintf("Socket close failed: %d. Error: %s\n", hSocket,
                  NetworkErrorString(WSAGetLastError()));
    }
    hSocket = INVALID_SOCKET;
    return ret != SOCKET_ERROR;
}