Method rcv_priority_frame

src/proxy/http2/Http2ConnectionState.cc:545–627

* [RFC 7540] 6.3 PRIORITY * */

 *
 */
Http2Error
Http2ConnectionState::rcv_priority_frame(const Http2Frame &frame)
{
  const Http2StreamId stream_id      = frame.header().streamid;
  const uint32_t      payload_length = frame.header().length;

  Http2StreamDebug(this->session, stream_id, "Received PRIORITY frame");

  if (this->get_zombie_event()) {
    Warning("Priority frame for zombied session %" PRId64, this->session->get_connection_id());
  }

  // If a PRIORITY frame is received with a stream identifier of 0x0, the
  // recipient MUST respond with a connection error of type PROTOCOL_ERROR.
  if (stream_id == HTTP2_CONNECTION_CONTROL_STREAM) {
    return Http2Error(Http2ErrorClass::HTTP2_ERROR_CLASS_CONNECTION, Http2ErrorCode::HTTP2_ERROR_PROTOCOL_ERROR,
                      "priority 0 stream_id");
  }

  // A PRIORITY frame with a length other than 5 octets MUST be treated as
  // a stream error (Section 5.4.2) of type FRAME_SIZE_ERROR.
  if (payload_length != HTTP2_PRIORITY_LEN) {
    return Http2Error(Http2ErrorClass::HTTP2_ERROR_CLASS_STREAM, Http2ErrorCode::HTTP2_ERROR_FRAME_SIZE_ERROR,
                      "priority bad length");
  }

  uint8_t buf[HTTP2_PRIORITY_LEN] = {0};
  frame.reader()->memcpy(buf, HTTP2_PRIORITY_LEN, 0);

  Http2Priority priority;
  if (!http2_parse_priority_parameter(make_iovec(buf, HTTP2_PRIORITY_LEN), priority)) {
    return Http2Error(Http2ErrorClass::HTTP2_ERROR_CLASS_CONNECTION, Http2ErrorCode::HTTP2_ERROR_PROTOCOL_ERROR,
                      "priority parse error");
  }

  //  A stream cannot depend on itself.  An endpoint MUST treat this as a stream error of type PROTOCOL_ERROR.
  if (stream_id == priority.stream_dependency) {
    return Http2Error(Http2ErrorClass::HTTP2_ERROR_CLASS_STREAM, Http2ErrorCode::HTTP2_ERROR_PROTOCOL_ERROR,
                      "PRIORITY frame depends on itself");
  }

  if (!Http2::stream_priority_enabled) {
    return Http2Error(Http2ErrorClass::HTTP2_ERROR_CLASS_NONE);
  }

  // Update PRIORITY frame count per minute
  this->increment_received_priority_frame_count();
  // Close this connection if its priority frame count received exceeds a limit
  if (configured_max_priority_frames_per_minute >= 0 &&
      this->get_received_priority_frame_count() > static_cast<uint32_t>(configured_max_priority_frames_per_minute)) {
    Metrics::Counter::increment(http2_rsb.max_priority_frames_per_minute_exceeded);
    Http2StreamDebug(this->session, stream_id, "Observed too frequent priority changes: %u priority changes within a last minute",
                     this->get_received_priority_frame_count());
    return Http2Error(Http2ErrorClass::HTTP2_ERROR_CLASS_CONNECTION, Http2ErrorCode::HTTP2_ERROR_ENHANCE_YOUR_CALM,
                      "recv priority too frequent priority changes");
  }

  Http2StreamDebug(this->session, stream_id, "PRIORITY - dep: %d, weight: %d, excl: %d, tree size: %d", priority.stream_dependency,