gfe-relnote: In QUIC, do not inject bandwidth in BbrSender::AdjustNetworkParameters. Also use min rtt instead of srtt when calculating new cwnd. Protected by gfe2_reloadable_flag_quic_bbr_donot_inject_bandwidth.

PiperOrigin-RevId: 279119475
Change-Id: I6bca045fd27926321e1984b41849dd406f6fe6ab

quic/core/congestion_control/bbr_sender.cc

diff --git a/quic/core/congestion_control/bbr_sender.cc b/quic/core/congestion_control/bbr_sender.cc
index b9a259a..478339a 100644
--- a/quic/core/congestion_control/bbr_sender.cc
+++ b/quic/core/congestion_control/bbr_sender.cc
@@ -332,7 +332,9 @@
 void BbrSender::AdjustNetworkParameters(QuicBandwidth bandwidth,
                                         QuicTime::Delta rtt,
                                         bool allow_cwnd_to_decrease) {
-  if (!bandwidth.IsZero()) {
+  if (GetQuicReloadableFlag(quic_bbr_donot_inject_bandwidth)) {
+    QUIC_RELOADABLE_FLAG_COUNT(quic_bbr_donot_inject_bandwidth);
+  } else if (!bandwidth.IsZero()) {
     max_bandwidth_.Update(bandwidth, round_trip_count_);
   }
   if (!rtt.IsZero() && (min_rtt_ > rtt || min_rtt_.IsZero())) {
@@ -346,10 +348,13 @@
                                    3);
       return;
     }
-    const QuicByteCount new_cwnd =
-        std::max(kMinInitialCongestionWindow * kDefaultTCPMSS,
-                 std::min(kMaxInitialCongestionWindow * kDefaultTCPMSS,
-                          bandwidth * rtt_stats_->SmoothedOrInitialRtt()));
+    const QuicByteCount new_cwnd = std::max(
+        kMinInitialCongestionWindow * kDefaultTCPMSS,
+        std::min(
+            kMaxInitialCongestionWindow * kDefaultTCPMSS,
+            bandwidth * (GetQuicReloadableFlag(quic_bbr_donot_inject_bandwidth)
+                             ? GetMinRtt()
+                             : rtt_stats_->SmoothedOrInitialRtt())));
     if (!rtt_stats_->smoothed_rtt().IsZero()) {
       QUIC_CODE_COUNT(quic_smoothed_rtt_available);
     } else if (rtt_stats_->initial_rtt() !=

quic/core/congestion_control/bbr_sender_test.cc

diff --git a/quic/core/congestion_control/bbr_sender_test.cc b/quic/core/congestion_control/bbr_sender_test.cc
index 9403c57..9120ea8 100644
--- a/quic/core/congestion_control/bbr_sender_test.cc
+++ b/quic/core/congestion_control/bbr_sender_test.cc
@@ -1251,8 +1251,15 @@
 
   bbr_sender_.connection()->AdjustNetworkParameters(kTestLinkBandwidth,
                                                     kTestRtt, false);
-  EXPECT_EQ(kTestLinkBandwidth, sender_->ExportDebugState().max_bandwidth);
-  EXPECT_EQ(kTestLinkBandwidth, sender_->BandwidthEstimate());
+  if (!GetQuicReloadableFlag(quic_bbr_donot_inject_bandwidth)) {
+    EXPECT_EQ(kTestLinkBandwidth, sender_->ExportDebugState().max_bandwidth);
+    EXPECT_EQ(kTestLinkBandwidth, sender_->BandwidthEstimate());
+  }
+  EXPECT_EQ(kTestLinkBandwidth * kTestRtt,
+            sender_->ExportDebugState().congestion_window);
+  if (GetQuicReloadableFlag(quic_bbr_fix_pacing_rate)) {
+    EXPECT_EQ(kTestLinkBandwidth, sender_->PacingRate(/*bytes_in_flight=*/0));
+  }
   EXPECT_APPROX_EQ(kTestRtt, sender_->ExportDebugState().min_rtt, 0.01f);
 
   DriveOutOfStartup();
@@ -1327,8 +1334,10 @@
   // Bootstrap cwnd.
   bbr_sender_.connection()->AdjustNetworkParameters(
       kTestLinkBandwidth, QuicTime::Delta::Zero(), false);
-  EXPECT_EQ(kTestLinkBandwidth, sender_->ExportDebugState().max_bandwidth);
-  EXPECT_EQ(kTestLinkBandwidth, sender_->BandwidthEstimate());
+  if (!GetQuicReloadableFlag(quic_bbr_donot_inject_bandwidth)) {
+    EXPECT_EQ(kTestLinkBandwidth, sender_->ExportDebugState().max_bandwidth);
+    EXPECT_EQ(kTestLinkBandwidth, sender_->BandwidthEstimate());
+  }
   EXPECT_LT(previous_cwnd, sender_->ExportDebugState().congestion_window);
 
   if (GetQuicReloadableFlag(quic_bbr_fix_pacing_rate)) {
@@ -1354,8 +1363,10 @@
   // Bootstrap cwnd.
   bbr_sender_.connection()->AdjustNetworkParameters(
       kTestLinkBandwidth, QuicTime::Delta::Zero(), false);
-  EXPECT_EQ(kTestLinkBandwidth, sender_->ExportDebugState().max_bandwidth);
-  EXPECT_EQ(kTestLinkBandwidth, sender_->BandwidthEstimate());
+  if (!GetQuicReloadableFlag(quic_bbr_donot_inject_bandwidth)) {
+    EXPECT_EQ(kTestLinkBandwidth, sender_->ExportDebugState().max_bandwidth);
+    EXPECT_EQ(kTestLinkBandwidth, sender_->BandwidthEstimate());
+  }
   EXPECT_LT(kInitialCongestionWindowPackets * kDefaultTCPMSS,
             sender_->ExportDebugState().congestion_window);
   // No Rtt sample is available.