Allow number of open QUIC streams to grow 10% beyond configured limit at

net/quic/quic_session.cc

Index: net/quic/quic_session.cc
diff --git a/net/quic/quic_session.cc b/net/quic/quic_session.cc
index b31224392ad8d433d0a2c0f75b3bdcfafd298e6d..7fd5ae9c73217341e85c514be95b31e94174d03d 100644
--- a/net/quic/quic_session.cc
+++ b/net/quic/quic_session.cc
@@ -476,6 +476,15 @@ bool QuicSession::IsCryptoHandshakeConfirmed() {
 void QuicSession::OnConfigNegotiated() {
   connection_->SetFromConfig(config_);
   QuicVersion version = connection()->version();
+
+  // A server should accept a small number of additional streams beyond the
+  // limit sent to the client. This helps avoid early connection termination
+  // when FIN/RSTs for old streams are lost or arrive out of order.
+  if (FLAGS_quic_allow_more_open_streams) {
+    set_max_open_streams((is_server() ? kMaxStreamsMultiplier : 1.0) *
+                         config_.max_streams_per_connection());
+  }
+
   if (version <= QUIC_VERSION_16) {
     return;
   }
@@ -564,7 +573,9 @@ void QuicSession::OnCryptoHandshakeEvent(CryptoHandshakeEvent event) {
       // the peer.
       connection_->NeuterUnencryptedPackets();
       connection_->SetOverallConnectionTimeout(QuicTime::Delta::Infinite());
-      max_open_streams_ = config_.max_streams_per_connection();
+      if (!FLAGS_quic_allow_more_open_streams) {
+        max_open_streams_ = config_.max_streams_per_connection();
+      }
       break;
 
     default:
@@ -679,6 +690,11 @@ QuicDataStream* QuicSession::GetIncomingDataStream(QuicStreamId stream_id) {
   return stream;
 }
 
+void QuicSession::set_max_open_streams(size_t max_open_streams) {
+  DVLOG(1) << "Setting max_open_streams_ to " << max_open_streams;
+  max_open_streams_ = max_open_streams;
+}
+
 bool QuicSession::IsClosedStream(QuicStreamId id) {
   DCHECK_NE(0u, id);
   if (id == kCryptoStreamId) {