Verify that transport-cc is used when RFC8888 field trial is off.

This is preparatory to ensuring that transport-cc gets turned off when
RFC8888 ccfb is negotiated.

Bug: webrtc:378698658
Change-Id: Ie76677bd6aa046701562bbd93d8489858488f863
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/368543
Reviewed-by: Per Kjellander <perkj@webrtc.org>
Commit-Queue: Harald Alvestrand <hta@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#43426}

call/call.cc

@@ -280,6 +280,7 @@ class Call final : public webrtc::Call,
 
   void EnableSendCongestionControlFeedbackAccordingToRfc8888() override;
   int FeedbackAccordingToRfc8888Count() override;
+  int FeedbackAccordingToTransportCcCount() override;
 
   const FieldTrialsView& trials() const override;
 
@@ -1200,6 +1201,10 @@ int Call::FeedbackAccordingToRfc8888Count() {
   return transport_send_->ReceivedCongestionControlFeedbackCount();
 }
 
+int Call::FeedbackAccordingToTransportCcCount() {
+  return transport_send_->ReceivedTransportCcFeedbackCount();
+}
+
 const FieldTrialsView& Call::trials() const {
   return env_.field_trials();
 }

call/call.h

@@ -155,6 +155,7 @@ class Call {
 
   virtual void EnableSendCongestionControlFeedbackAccordingToRfc8888() = 0;
   virtual int FeedbackAccordingToRfc8888Count() = 0;
+  virtual int FeedbackAccordingToTransportCcCount() = 0;
 
   virtual const FieldTrialsView& trials() const = 0;
 

call/rtp_transport_controller_send.cc

@@ -639,6 +639,7 @@ void RtpTransportControllerSend::OnTransportFeedback(
     Timestamp receive_time,
     const rtcp::TransportFeedback& feedback) {
   RTC_DCHECK_RUN_ON(&sequence_checker_);
+  ++transport_cc_feedback_count_;
   feedback_demuxer_.OnTransportFeedback(feedback);
   std::optional<TransportPacketsFeedback> feedback_msg =
       transport_feedback_adapter_.ProcessTransportFeedback(feedback,

call/rtp_transport_controller_send.h

@@ -146,6 +146,10 @@ class RtpTransportControllerSend final
     RTC_DCHECK_RUN_ON(&sequence_checker_);
     return feedback_count_;
   }
+  int ReceivedTransportCcFeedbackCount() const override {
+    RTC_DCHECK_RUN_ON(&sequence_checker_);
+    return transport_cc_feedback_count_;
+  }
 
  private:
   void MaybeCreateControllers() RTC_RUN_ON(sequence_checker_);
@@ -235,6 +239,7 @@ class RtpTransportControllerSend final
   bool is_congested_ RTC_GUARDED_BY(sequence_checker_);
   // Count of feedback messages received.
   int feedback_count_ RTC_GUARDED_BY(sequence_checker_) = 0;
+  int transport_cc_feedback_count_ RTC_GUARDED_BY(sequence_checker_) = 0;
 
   // Protected by internal locks.
   RateLimiter retransmission_rate_limiter_;

call/rtp_transport_controller_send_interface.h

@@ -163,6 +163,8 @@ class RtpTransportControllerSendInterface {
   virtual NetworkControllerInterface* GetNetworkController() = 0;
   // Count of RFC8888 feedback reports received
   virtual int ReceivedCongestionControlFeedbackCount() const = 0;
+  // Count of transport-cc feedback reports received
+  virtual int ReceivedTransportCcFeedbackCount() const = 0;
 };
 
 }  // namespace webrtc

call/test/mock_rtp_transport_controller_send.h

@@ -119,6 +119,7 @@ class MockRtpTransportControllerSend
               ReceivedCongestionControlFeedbackCount,
               (),
               (const, override));
+  MOCK_METHOD(int, ReceivedTransportCcFeedbackCount, (), (const, override));
 };
 }  // namespace webrtc
 #endif  // CALL_TEST_MOCK_RTP_TRANSPORT_CONTROLLER_SEND_H_

media/engine/fake_webrtc_call.h

@@ -471,6 +471,7 @@ class FakeCall final : public webrtc::Call, public webrtc::PacketReceiver {
   }
   void EnableSendCongestionControlFeedbackAccordingToRfc8888() override {}
   int FeedbackAccordingToRfc8888Count() { return 0; }
+  int FeedbackAccordingToTransportCcCount() { return 0; }
 
  private:
   webrtc::AudioSendStream* CreateAudioSendStream(

pc/congestion_control_integrationtest.cc

@@ -23,6 +23,7 @@
 
 namespace webrtc {
 
+using testing::Eq;
 using testing::HasSubstr;
 
 class PeerConnectionCongestionControlTest
@@ -83,4 +84,24 @@ TEST_F(PeerConnectionCongestionControlTest, CcfbGetsUsed) {
                    kDefaultTimeout);
 }
 
+TEST_F(PeerConnectionCongestionControlTest, TransportCcGetsUsed) {
+  test::ScopedFieldTrials trials(
+      "WebRTC-RFC8888CongestionControlFeedback/Disabled/");
+  ASSERT_TRUE(CreatePeerConnectionWrappers());
+  ConnectFakeSignaling();
+  caller()->AddAudioVideoTracks();
+  caller()->CreateAndSetAndSignalOffer();
+  ASSERT_TRUE_WAIT(SignalingStateStable(), kDefaultTimeout);
+  MediaExpectations media_expectations;
+  media_expectations.CalleeExpectsSomeAudio();
+  media_expectations.CalleeExpectsSomeVideo();
+  ASSERT_TRUE(ExpectNewFrames(media_expectations));
+  auto pc_internal = caller()->pc_internal();
+  EXPECT_TRUE_WAIT(
+      pc_internal->FeedbackAccordingToTransportCcCountForTesting() > 0,
+      kDefaultTimeout);
+  // Test that RFC 8888 feedback is NOT generated when field trial disabled.
+  EXPECT_THAT(pc_internal->FeedbackAccordingToRfc8888CountForTesting(), Eq(0));
+}
+
 }  // namespace webrtc

pc/peer_connection.cc

@@ -3038,6 +3038,13 @@ int PeerConnection::FeedbackAccordingToRfc8888CountForTesting() const {
   });
 }
 
+int PeerConnection::FeedbackAccordingToTransportCcCountForTesting() const {
+  return worker_thread()->BlockingCall([this]() {
+    RTC_DCHECK_RUN_ON(worker_thread());
+    return call_->FeedbackAccordingToTransportCcCount();
+  });
+}
+
 std::function<void(const rtc::CopyOnWriteBuffer& packet,
                    int64_t packet_time_us)>
 PeerConnection::InitializeRtcpCallback() {

pc/peer_connection.h

@@ -443,6 +443,7 @@ class PeerConnection : public PeerConnectionInternal,
   }
   void RequestUsagePatternReportForTesting();
   int FeedbackAccordingToRfc8888CountForTesting() const;
+  int FeedbackAccordingToTransportCcCountForTesting() const;
 
   NetworkControllerInterface* GetNetworkController() override {
     if (!worker_thread()->IsCurrent()) {