Landing Recent QUIC changes until 4/22/2016 14:55 UTC

net/quic/congestion_control/tcp_cubic_sender_packets.cc

Index: net/quic/congestion_control/tcp_cubic_sender_packets.cc
diff --git a/net/quic/congestion_control/tcp_cubic_sender_packets.cc b/net/quic/congestion_control/tcp_cubic_sender_packets.cc
index aee29ba1064cdc3efa7774fc6f6c5794cd111c01..0467963c487f528dd7cc3380b09dcb36eb83a67e 100644
--- a/net/quic/congestion_control/tcp_cubic_sender_packets.cc
+++ b/net/quic/congestion_control/tcp_cubic_sender_packets.cc
@@ -41,18 +41,24 @@ TcpCubicSenderPackets::TcpCubicSenderPackets(
       slowstart_threshold_(max_tcp_congestion_window),
       max_tcp_congestion_window_(max_tcp_congestion_window),
       initial_tcp_congestion_window_(initial_tcp_congestion_window),
-      initial_max_tcp_congestion_window_(max_tcp_congestion_window) {}
+      initial_max_tcp_congestion_window_(max_tcp_congestion_window),
+      min_slow_start_exit_window_(min_congestion_window_) {}
 
 TcpCubicSenderPackets::~TcpCubicSenderPackets() {}
 
 void TcpCubicSenderPackets::SetCongestionWindowFromBandwidthAndRtt(
     QuicBandwidth bandwidth,
     QuicTime::Delta rtt) {
-  // Make sure CWND is in appropriate range (in case of bad data).
   QuicPacketCount new_congestion_window =
       bandwidth.ToBytesPerPeriod(rtt) / kDefaultTCPMSS;
-  congestion_window_ = max(min(new_congestion_window, kMaxCongestionWindow),
-                           kMinCongestionWindowForBandwidthResumption);
+  if (FLAGS_quic_no_lower_bw_resumption_limit) {
+    // Limit new CWND to be in the range [1, kMaxCongestionWindow].
+    congestion_window_ = max(min_congestion_window_,
+                             min(new_congestion_window, kMaxCongestionWindow));
+  } else {
+    congestion_window_ = max(min(new_congestion_window, kMaxCongestionWindow),
+                             kMinCongestionWindowForBandwidthResumption);
+  }
 }
 
 void TcpCubicSenderPackets::SetCongestionWindowInPackets(
@@ -94,7 +100,7 @@ void TcpCubicSenderPackets::OnPacketLost(QuicPacketNumber packet_number,
                 (stats_->slowstart_bytes_lost - lost_bytes) / kDefaultTCPMSS) {
           // Reduce congestion window by 1 for every mss of bytes lost.
           congestion_window_ =
-              max(congestion_window_ - 1, min_congestion_window_);
+              max(congestion_window_ - 1, min_slow_start_exit_window_);
         }
         slowstart_threshold_ = congestion_window_;
       }
@@ -114,6 +120,10 @@ void TcpCubicSenderPackets::OnPacketLost(QuicPacketNumber packet_number,
   // TODO(jri): Separate out all of slow start into a separate class.
   if (slow_start_large_reduction_ && InSlowStart()) {
     DCHECK_LT(1u, congestion_window_);
+    if (FLAGS_quic_sslr_limit_reduction &&
+        congestion_window_ >= 2 * initial_tcp_congestion_window_) {
+      min_slow_start_exit_window_ = congestion_window_ / 2;
+    }
     congestion_window_ = congestion_window_ - 1;
   } else if (reno_) {
     congestion_window_ = congestion_window_ * RenoBeta();