DataPathResult iobufChainBasedBuildScheduleEncrypt()

in quic/api/QuicTransportFunctions.cpp [291:368]

• 74 lines of code
• 8 McCabe index (conditional complexity)

DataPathResult iobufChainBasedBuildScheduleEncrypt(
    QuicConnectionStateBase& connection,
    PacketHeader header,
    PacketNumberSpace pnSpace,
    PacketNum packetNum,
    uint64_t cipherOverhead,
    QuicPacketScheduler& scheduler,
    uint64_t writableBytes,
    IOBufQuicBatch& ioBufBatch,
    const Aead& aead,
    const PacketNumberCipher& headerCipher) {
  RegularQuicPacketBuilder pktBuilder(
      connection.udpSendPacketLen,
      std::move(header),
      getAckState(connection, pnSpace).largestAckedByPeer.value_or(0));
  // It's the scheduler's job to invoke encode header
  pktBuilder.accountForCipherOverhead(cipherOverhead);
  auto result =
      scheduler.scheduleFramesForPacket(std::move(pktBuilder), writableBytes);
  auto& packet = result.packet;
  if (!packet || packet->packet.frames.empty()) {
    ioBufBatch.flush();
    if (connection.loopDetectorCallback) {
      connection.writeDebugState.noWriteReason = NoWriteReason::NO_FRAME;
    }
    return DataPathResult::makeBuildFailure();
  }
  if (!packet->body) {
    // No more space remaining.
    ioBufBatch.flush();
    if (connection.loopDetectorCallback) {
      connection.writeDebugState.noWriteReason = NoWriteReason::NO_BODY;
    }
    return DataPathResult::makeBuildFailure();
  }
  packet->header->coalesce();
  auto headerLen = packet->header->length();
  auto bodyLen = packet->body->computeChainDataLength();
  auto unencrypted =
      folly::IOBuf::create(headerLen + bodyLen + aead.getCipherOverhead());
  auto bodyCursor = folly::io::Cursor(packet->body.get());
  bodyCursor.pull(unencrypted->writableData() + headerLen, bodyLen);
  unencrypted->advance(headerLen);
  unencrypted->append(bodyLen);
  auto packetBuf = aead.inplaceEncrypt(
      std::move(unencrypted), packet->header.get(), packetNum);
  DCHECK(packetBuf->headroom() == headerLen);
  packetBuf->clear();
  auto headerCursor = folly::io::Cursor(packet->header.get());
  headerCursor.pull(packetBuf->writableData(), headerLen);
  packetBuf->append(headerLen + bodyLen + aead.getCipherOverhead());

  HeaderForm headerForm = packet->packet.header.getHeaderForm();
  encryptPacketHeader(
      headerForm,
      packetBuf->writableData(),
      headerLen,
      packetBuf->data() + headerLen,
      packetBuf->length() - headerLen,
      headerCipher);
  auto encodedSize = packetBuf->computeChainDataLength();
  auto encodedBodySize = encodedSize - headerLen;
#if !FOLLY_MOBILE
  if (encodedSize > connection.udpSendPacketLen) {
    LOG_EVERY_N(ERROR, 5000)
        << "Quic sending pkt larger than limit, encodedSize=" << encodedSize
        << " encodedBodySize=" << encodedBodySize;
  }
#endif
  bool ret = ioBufBatch.write(std::move(packetBuf), encodedSize);
  if (ret) {
    // update stats and connection
    QUIC_STATS(connection.statsCallback, onWrite, encodedSize);
    QUIC_STATS(connection.statsCallback, onPacketSent);
  }
  return DataPathResult::makeWriteResult(
      ret, std::move(result), encodedSize, encodedBodySize);
}