void writeCloseCommon()

in quic/api/QuicTransportFunctions.cpp [1139:1237]
94 lines of code
12 McCabe index (conditional complexity)

void writeCloseCommon(
    folly::AsyncUDPSocket& sock,
    QuicConnectionStateBase& connection,
    PacketHeader&& header,
    folly::Optional<QuicError> closeDetails,
    const Aead& aead,
    const PacketNumberCipher& headerCipher) {
  // close is special, we're going to bypass all the packet sent logic for all
  // packets we send with a connection close frame.
  PacketNumberSpace pnSpace = header.getPacketNumberSpace();
  HeaderForm headerForm = header.getHeaderForm();
  PacketNum packetNum = header.getPacketSequenceNum();
  // TODO: This too needs to be switchable between regular and inplace builder.
  RegularQuicPacketBuilder packetBuilder(
      kDefaultUDPSendPacketLen,
      std::move(header),
      getAckState(connection, pnSpace).largestAckedByPeer.value_or(0));
  packetBuilder.encodePacketHeader();
  packetBuilder.accountForCipherOverhead(aead.getCipherOverhead());
  size_t written = 0;
  if (!closeDetails) {
    written = writeFrame(
        ConnectionCloseFrame(
            QuicErrorCode(TransportErrorCode::NO_ERROR),
            std::string("No error")),
        packetBuilder);
  } else {
    switch (closeDetails->code.type()) {
      case QuicErrorCode::Type::ApplicationErrorCode:
        written = writeFrame(
            ConnectionCloseFrame(
                QuicErrorCode(*closeDetails->code.asApplicationErrorCode()),
                closeDetails->message,
                quic::FrameType::CONNECTION_CLOSE_APP_ERR),
            packetBuilder);
        break;
      case QuicErrorCode::Type::TransportErrorCode:
        written = writeFrame(
            ConnectionCloseFrame(
                QuicErrorCode(*closeDetails->code.asTransportErrorCode()),
                closeDetails->message,
                quic::FrameType::CONNECTION_CLOSE),
            packetBuilder);
        break;
      case QuicErrorCode::Type::LocalErrorCode:
        written = writeFrame(
            ConnectionCloseFrame(
                QuicErrorCode(TransportErrorCode::INTERNAL_ERROR),
                std::string("Internal error"),
                quic::FrameType::CONNECTION_CLOSE),
            packetBuilder);
        break;
    }
  }
  if (pnSpace == PacketNumberSpace::Initial &&
      connection.nodeType == QuicNodeType::Client) {
    while (packetBuilder.remainingSpaceInPkt() > 0) {
      writeFrame(PaddingFrame(), packetBuilder);
    }
  }
  if (written == 0) {
    LOG(ERROR) << "Close frame too large " << connection;
    return;
  }
  auto packet = std::move(packetBuilder).buildPacket();
  packet.header->coalesce();
  packet.body->reserve(0, aead.getCipherOverhead());
  CHECK_GE(packet.body->tailroom(), aead.getCipherOverhead());
  auto body = aead.inplaceEncrypt(
      std::move(packet.body), packet.header.get(), packetNum);
  body->coalesce();
  encryptPacketHeader(
      headerForm,
      packet.header->writableData(),
      packet.header->length(),
      body->data(),
      body->length(),
      headerCipher);
  auto packetBuf = std::move(packet.header);
  packetBuf->prependChain(std::move(body));
  auto packetSize = packetBuf->computeChainDataLength();
  if (connection.qLogger) {
    connection.qLogger->addPacket(packet.packet, packetSize);
  }
  VLOG(10) << nodeToString(connection.nodeType)
           << " sent close packetNum=" << packetNum << " in space=" << pnSpace
           << " " << connection;
  // Increment the sequence number.
  increaseNextPacketNum(connection, pnSpace);
  // best effort writing to the socket, ignore any errors.
  auto ret = sock.write(connection.peerAddress, packetBuf);
  connection.lossState.totalBytesSent += packetSize;
  if (ret < 0) {
    VLOG(4) << "Error writing connection close " << folly::errnoStr(errno)
            << " " << connection;
  } else {
    QUIC_STATS(connection.statsCallback, onWrite, ret);
  }
}