Congestion Control interface for receiving ECN feedback. PiperOrigin-RevId: 515174710

diff --git a/quiche/quic/core/congestion_control/bbr2_sender.h b/quiche/quic/core/congestion_control/bbr2_sender.h
index 7f47a4e..d808791 100644
--- a/quiche/quic/core/congestion_control/bbr2_sender.h
+++ b/quiche/quic/core/congestion_control/bbr2_sender.h

@@ -92,6 +92,9 @@
   void OnApplicationLimited(QuicByteCount bytes_in_flight) override;
 
   void PopulateConnectionStats(QuicConnectionStats* stats) const override;
+
+  void CongestionExperienced(QuicPacketCount /*num_ce*/,
+                             QuicPacketCount /*num_ect*/) override {}
   // End implementation of SendAlgorithmInterface.
 
   const Bbr2Params& Params() const { return params_; }

diff --git a/quiche/quic/core/congestion_control/bbr_sender.h b/quiche/quic/core/congestion_control/bbr_sender.h
index 5f711fd..774cb7e 100644
--- a/quiche/quic/core/congestion_control/bbr_sender.h
+++ b/quiche/quic/core/congestion_control/bbr_sender.h

@@ -130,6 +130,8 @@
   std::string GetDebugState() const override;
   void OnApplicationLimited(QuicByteCount bytes_in_flight) override;
   void PopulateConnectionStats(QuicConnectionStats* stats) const override;
+  void CongestionExperienced(QuicPacketCount /*num_ce*/,
+                             QuicPacketCount /*num_ect*/) override {}
   // End implementation of SendAlgorithmInterface.
 
   // Gets the number of RTTs BBR remains in STARTUP phase.

diff --git a/quiche/quic/core/congestion_control/send_algorithm_interface.h b/quiche/quic/core/congestion_control/send_algorithm_interface.h
index db14a1e..82be341 100644
--- a/quiche/quic/core/congestion_control/send_algorithm_interface.h
+++ b/quiche/quic/core/congestion_control/send_algorithm_interface.h

@@ -160,6 +160,11 @@
 
   // Called before connection close to collect stats.
   virtual void PopulateConnectionStats(QuicConnectionStats* stats) const = 0;
+
+  // Called when the connection has received feedback about received
+  // Explicit Congestion Notification (ECN) marks.
+  virtual void CongestionExperienced(QuicPacketCount num_ce,
+                                     QuicPacketCount num_ect) = 0;
 };
 
 }  // namespace quic

diff --git a/quiche/quic/core/congestion_control/tcp_cubic_sender_bytes.h b/quiche/quic/core/congestion_control/tcp_cubic_sender_bytes.h
index 2531e5a..ae24c8c 100644
--- a/quiche/quic/core/congestion_control/tcp_cubic_sender_bytes.h
+++ b/quiche/quic/core/congestion_control/tcp_cubic_sender_bytes.h

@@ -72,6 +72,8 @@
   std::string GetDebugState() const override;
   void OnApplicationLimited(QuicByteCount bytes_in_flight) override;
   void PopulateConnectionStats(QuicConnectionStats* /*stats*/) const override {}
+  void CongestionExperienced(QuicPacketCount /*num_ce*/,
+                             QuicPacketCount /*num_ect*/) override {}
   // End implementation of SendAlgorithmInterface.
 
   QuicByteCount min_congestion_window() const { return min_congestion_window_; }

diff --git a/quiche/quic/test_tools/quic_test_utils.h b/quiche/quic/test_tools/quic_test_utils.h
index 9d717df..3664b11 100644
--- a/quiche/quic/test_tools/quic_test_utils.h
+++ b/quiche/quic/test_tools/quic_test_utils.h

@@ -1243,6 +1243,8 @@
   MOCK_METHOD(void, OnApplicationLimited, (QuicByteCount), (override));
   MOCK_METHOD(void, PopulateConnectionStats, (QuicConnectionStats*),
               (const, override));
+  MOCK_METHOD(void, CongestionExperienced, (QuicPacketCount, QuicPacketCount),
+              (override));
 };
 
 class MockLossAlgorithm : public LossDetectionInterface {