Function PCPRequestPortMap

src/common/pcp.cpp:406–542

}

std::variant<MappingResult, MappingError> PCPRequestPortMap(const PCPMappingNonce &nonce, const CNetAddr &gateway, const CNetAddr &bind, uint16_t port, uint32_t lifetime, CThreadInterrupt& interrupt, int num_tries, std::chrono::milliseconds timeout_per_try)
{
    struct sockaddr_storage dest_addr, bind_addr;
    socklen_t dest_addrlen = sizeof(struct sockaddr_storage), bind_addrlen = sizeof(struct sockaddr_storage);

    LogDebug(BCLog::NET, "pcp: Requesting port mapping for addr %s port %d from gateway %s\n", bind.ToStringAddr(), port, gateway.ToStringAddr());

    // Validate addresses, make sure they're the same network family.
    if (!CService(gateway, PCP_SERVER_PORT).GetSockAddr((struct sockaddr*)&dest_addr, &dest_addrlen)) return MappingError::NETWORK_ERROR;
    if (!CService(bind, 0).GetSockAddr((struct sockaddr*)&bind_addr, &bind_addrlen)) return MappingError::NETWORK_ERROR;
    if (dest_addr.ss_family != bind_addr.ss_family) return MappingError::NETWORK_ERROR;

    // Create UDP socket (IPv4 or IPv6 based on provided gateway).
    auto sock{CreateSock(dest_addr.ss_family, SOCK_DGRAM, IPPROTO_UDP)};
    if (!sock) {
        LogWarning("pcp: Could not create UDP socket: %s\n", NetworkErrorString(WSAGetLastError()));
        return MappingError::NETWORK_ERROR;
    }

    // Make sure that we send from requested destination address, anything else will be
    // rejected by a security-conscious router.
    if (sock->Bind((struct sockaddr*)&bind_addr, bind_addrlen) != 0) {
        LogWarning("pcp: Could not bind to address: %s\n", NetworkErrorString(WSAGetLastError()));
        return MappingError::NETWORK_ERROR;
    }

    // Associate UDP socket to gateway.
    if (sock->Connect((struct sockaddr*)&dest_addr, dest_addrlen) != 0) {
        LogWarning("pcp: Could not connect to gateway: %s\n", NetworkErrorString(WSAGetLastError()));
        return MappingError::NETWORK_ERROR;
    }

    // Use getsockname to get the address toward the default gateway (the internal address),
    // in case we don't know what address to map
    // (this is only needed if bind is INADDR_ANY, but it doesn't hurt as an extra check).
    struct sockaddr_storage internal_addr;
    socklen_t internal_addrlen = sizeof(struct sockaddr_storage);
    if (sock->GetSockName((struct sockaddr*)&internal_addr, &internal_addrlen) != 0) {
        LogWarning("pcp: Could not get sock name: %s\n", NetworkErrorString(WSAGetLastError()));
        return MappingError::NETWORK_ERROR;
    }
    CService internal;
    if (!internal.SetSockAddr((struct sockaddr*)&internal_addr, internal_addrlen)) return MappingError::NETWORK_ERROR;
    LogDebug(BCLog::NET, "pcp: Internal address after connect: %s\n", internal.ToStringAddr());

    // Build request packet. Make sure the packet is zeroed so that reserved fields are zero
    // as required by the spec (and not potentially leak data).
    // Make sure there's space for the request header and MAP specific request data.
    std::vector<uint8_t> request(PCP_HDR_SIZE + PCP_MAP_SIZE);
    // Fill in request header, See RFC6887 Figure 2.
    size_t ofs = 0;
    request[ofs + PCP_HDR_VERSION_OFS] = PCP_VERSION;
    request[ofs + PCP_HDR_OP_OFS] = PCP_REQUEST | PCP_OP_MAP;
    WriteBE32(request.data() + ofs + PCP_HDR_LIFETIME_OFS, lifetime);
    if (!PCPWrapAddress(std::span(request).subspan(ofs + PCP_REQUEST_HDR_IP_OFS, ADDR_IPV6_SIZE), internal)) return MappingError::NETWORK_ERROR;

    ofs += PCP_HDR_SIZE;