Remove dead code in BBR2 and BBR. flexible_app_limited was added for Quartc, which is not longer active. PiperOrigin-RevId: 339266593 Change-Id: Ie291a8b4907635f4ff9a1f8920dec9dda3484aaf

diff --git a/quic/core/congestion_control/bbr2_misc.h b/quic/core/congestion_control/bbr2_misc.h
index 2287960..0d852e9 100644
--- a/quic/core/congestion_control/bbr2_misc.h
+++ b/quic/core/congestion_control/bbr2_misc.h

@@ -171,10 +171,6 @@
    * Experimental flags from QuicConfig.
    */
 
-  // Indicates app-limited calls should be ignored as long as there's
-  // enough data inflight to see more bandwidth when necessary.
-  bool flexible_app_limited = false;
-
   // Can be disabled by connection option 'B2NA'.
   bool add_ack_height_to_queueing_threshold = true;
 

diff --git a/quic/core/congestion_control/bbr2_sender.cc b/quic/core/congestion_control/bbr2_sender.cc
index a2e23bf..5fcea6c 100644
--- a/quic/core/congestion_control/bbr2_sender.cc
+++ b/quic/core/congestion_control/bbr2_sender.cc

@@ -100,9 +100,6 @@
 
 void Bbr2Sender::SetFromConfig(const QuicConfig& config,
                                Perspective perspective) {
-  if (config.HasClientRequestedIndependentOption(kBBR9, perspective)) {
-    params_.flexible_app_limited = true;
-  }
   if (config.HasClientRequestedIndependentOption(kB2NA, perspective)) {
     params_.add_ack_height_to_queueing_threshold = false;
   }
@@ -405,9 +402,6 @@
   if (bytes_in_flight >= GetCongestionWindow()) {
     return;
   }
-  if (params().flexible_app_limited && IsPipeSufficientlyFull()) {
-    return;
-  }
 
   model_.OnApplicationLimited();
   QUIC_DVLOG(2) << this << " Becoming application limited. Last sent packet: "
@@ -443,41 +437,7 @@
 
 bool Bbr2Sender::ShouldSendProbingPacket() const {
   // TODO(wub): Implement ShouldSendProbingPacket properly.
-  if (!BBR2_MODE_DISPATCH(IsProbingForBandwidth())) {
-    return false;
-  }
-
-  // TODO(b/77975811): If the pipe is highly under-utilized, consider not
-  // sending a probing transmission, because the extra bandwidth is not needed.
-  // If flexible_app_limited is enabled, check if the pipe is sufficiently full.
-  if (params().flexible_app_limited) {
-    const bool is_pipe_sufficiently_full = IsPipeSufficientlyFull();
-    QUIC_DVLOG(3) << this << " CWND: " << GetCongestionWindow()
-                  << ", inflight: " << unacked_packets_->bytes_in_flight()
-                  << ", pacing_rate: " << PacingRate(0)
-                  << ", flexible_app_limited: true, ShouldSendProbingPacket: "
-                  << !is_pipe_sufficiently_full;
-    return !is_pipe_sufficiently_full;
-  } else {
-    return true;
-  }
-}
-
-bool Bbr2Sender::IsPipeSufficientlyFull() const {
-  QuicByteCount bytes_in_flight = unacked_packets_->bytes_in_flight();
-  // See if we need more bytes in flight to see more bandwidth.
-  if (mode_ == Bbr2Mode::STARTUP) {
-    // STARTUP exits if it doesn't observe a 25% bandwidth increase, so the CWND
-    // must be more than 25% above the target.
-    return bytes_in_flight >= GetTargetCongestionWindow(1.5);
-  }
-  if (model_.pacing_gain() > 1) {
-    // Super-unity PROBE_BW doesn't exit until 1.25 * BDP is achieved.
-    return bytes_in_flight >= GetTargetCongestionWindow(model_.pacing_gain());
-  }
-  // If bytes_in_flight are above the target congestion window, it should be
-  // possible to observe the same or more bandwidth if it's available.
-  return bytes_in_flight >= GetTargetCongestionWindow(1.1);
+  return BBR2_MODE_DISPATCH(IsProbingForBandwidth());
 }
 
 std::string Bbr2Sender::GetDebugState() const {

diff --git a/quic/core/congestion_control/bbr2_sender.h b/quic/core/congestion_control/bbr2_sender.h
index 1b328fe..6a83184 100644
--- a/quic/core/congestion_control/bbr2_sender.h
+++ b/quic/core/congestion_control/bbr2_sender.h

@@ -160,10 +160,6 @@
     return random_->RandUint64() % max;
   }
 
-  // Returns true if there are enough bytes in flight to ensure more bandwidth
-  // will be observed if present.
-  bool IsPipeSufficientlyFull() const;
-
   // Cwnd limits imposed by the current Bbr2 mode.
   Limits<QuicByteCount> GetCwndLimitsByMode() const;
 

diff --git a/quic/core/congestion_control/bbr_sender.cc b/quic/core/congestion_control/bbr_sender.cc
index ac953ba..7ce3ab5 100644
--- a/quic/core/congestion_control/bbr_sender.cc
+++ b/quic/core/congestion_control/bbr_sender.cc

@@ -221,24 +221,6 @@
   return true;
 }
 
-bool BbrSender::IsPipeSufficientlyFull() const {
-  // See if we need more bytes in flight to see more bandwidth.
-  if (mode_ == STARTUP) {
-    // STARTUP exits if it doesn't observe a 25% bandwidth increase, so the CWND
-    // must be more than 25% above the target.
-    return unacked_packets_->bytes_in_flight() >=
-           GetTargetCongestionWindow(1.5);
-  }
-  if (pacing_gain_ > 1) {
-    // Super-unity PROBE_BW doesn't exit until 1.25 * BDP is achieved.
-    return unacked_packets_->bytes_in_flight() >=
-           GetTargetCongestionWindow(pacing_gain_);
-  }
-  // If bytes_in_flight are above the target congestion window, it should be
-  // possible to observe the same or more bandwidth if it's available.
-  return unacked_packets_->bytes_in_flight() >= GetTargetCongestionWindow(1.1);
-}
-
 void BbrSender::SetFromConfig(const QuicConfig& config,
                               Perspective perspective) {
   if (config.HasClientRequestedIndependentOption(k1RTT, perspective)) {

diff --git a/quic/core/congestion_control/bbr_sender.h b/quic/core/congestion_control/bbr_sender.h
index ae6cce9..30f2945 100644
--- a/quic/core/congestion_control/bbr_sender.h
+++ b/quic/core/congestion_control/bbr_sender.h

@@ -244,10 +244,6 @@
   void CalculateRecoveryWindow(QuicByteCount bytes_acked,
                                QuicByteCount bytes_lost);
 
-  // Returns true if there are enough bytes in flight to ensure more bandwidth
-  // will be observed if present.
-  bool IsPipeSufficientlyFull() const;
-
   // Called right before exiting STARTUP.
   void OnExitStartup(QuicTime now);