Method read_single_message_from_net

src/iocore/net/UnixUDPNet.cc:386–516

} // namespace

void
UDPNetProcessorInternal::read_single_message_from_net(UDPNetHandler *nh, UDPConnection *xuc)
{
  UnixUDPConnection *uc = static_cast<UnixUDPConnection *>(xuc);

  // receive packet and queue onto UDPConnection.
  // don't call back connection at this time.
  int64_t            r;
  int                iters    = 0;
  unsigned           max_niov = 32;
  int64_t            gso_size{0}; // in case is available.
  struct msghdr      msg;
  Ptr<IOBufferBlock> chain, next_chain;
  struct iovec       tiovec[max_niov];
  int64_t            size_index  = BUFFER_SIZE_INDEX_2K;
  int64_t            buffer_size = BUFFER_SIZE_FOR_INDEX(size_index);
  // The max length of receive buffer is 32 * buffer_size (2048) = 65536 bytes.
  // Because the 'UDP Length' is type of uint16_t defined in RFC 768.
  // And there is 8 octets in 'User Datagram Header' which means the max length of payload is no more than 65527 bytes.
  do {
    // create IOBufferBlock chain to receive data
    unsigned int niov = build_iovec_block_chain(max_niov, size_index, chain, tiovec);

    // build struct msghdr
    sockaddr_storage fromaddr;
    sockaddr_storage toaddr;
    msg.msg_name    = &fromaddr;
    msg.msg_namelen = sizeof(fromaddr);
    msg.msg_iov     = tiovec;
    msg.msg_iovlen  = niov;
    msg.msg_flags   = 0;

    static const size_t cmsg_size{CMSG_SPACE(sizeof(int))
#ifdef IP_PKTINFO
                                  + CMSG_SPACE(sizeof(struct in_pktinfo))
#endif
#if defined(IPV6_PKTINFO) || defined(IPV6_RECVPKTINFO)
                                  + CMSG_SPACE(sizeof(struct in6_pktinfo))
#endif
#ifdef IP_RECVDSTADDR
                                  + CMSG_SPACE(sizeof(struct in_addr))
#endif
#ifdef UDP_GRO
                                  + CMSG_SPACE(sizeof(uint16_t))
#endif
    };

    char control[cmsg_size] = {0};
    msg.msg_control         = control;
    msg.msg_controllen      = cmsg_size;

    // receive data by recvmsg
    r = uc->sock.recvmsg(&msg, 0);
    if (r <= 0) {
      // error
      break;
    }