Method readHeader

src/net.cpp:739–780

}

int V1Transport::readHeader(std::span<const uint8_t> msg_bytes)
{
    AssertLockHeld(m_recv_mutex);
    // copy data to temporary parsing buffer
    unsigned int nRemaining = CMessageHeader::HEADER_SIZE - nHdrPos;
    unsigned int nCopy = std::min<unsigned int>(nRemaining, msg_bytes.size());

    memcpy(&hdrbuf[nHdrPos], msg_bytes.data(), nCopy);
    nHdrPos += nCopy;

    // if header incomplete, exit
    if (nHdrPos < CMessageHeader::HEADER_SIZE)
        return nCopy;

    // deserialize to CMessageHeader
    try {
        hdrbuf >> hdr;
    }
    catch (const std::exception&) {
        LogDebug(BCLog::NET, "Header error: Unable to deserialize, peer=%d\n", m_node_id);
        return -1;
    }

    // Check start string, network magic
    if (hdr.pchMessageStart != m_magic_bytes) {
        LogDebug(BCLog::NET, "Header error: Wrong MessageStart %s received, peer=%d\n", HexStr(hdr.pchMessageStart), m_node_id);
        return -1;
    }

    // reject messages larger than MAX_SIZE or MAX_PROTOCOL_MESSAGE_LENGTH
    // NOTE: failing to perform this check previously allowed a malicious peer to make us allocate 32MiB of memory per
    // connection. See https://bitcoincore.org/en/2024/07/03/disclose_receive_buffer_oom.
    if (hdr.nMessageSize > MAX_SIZE || hdr.nMessageSize > MAX_PROTOCOL_MESSAGE_LENGTH) {
        LogDebug(BCLog::NET, "Header error: Size too large (%s, %u bytes), peer=%d\n", SanitizeString(hdr.GetMessageType()), hdr.nMessageSize, m_node_id);
        return -1;
    }

    // switch state to reading message data
    in_data = true;

    return nCopy;
}

int V1Transport::readData(std::span<const uint8_t> msg_bytes)
{