When talking >=QUIC_VERSION_22, regularly send updated bandwidth

net/tools/quic/quic_server_session.cc

Index: net/tools/quic/quic_server_session.cc
diff --git a/net/tools/quic/quic_server_session.cc b/net/tools/quic/quic_server_session.cc
index c59559c28a77e69dfeb85ad4d71813de865f4597..b5be8d436bf4572840e3c42f551fb819d0d65a25 100644
--- a/net/tools/quic/quic_server_session.cc
+++ b/net/tools/quic/quic_server_session.cc
@@ -5,6 +5,7 @@
 #include "net/tools/quic/quic_server_session.h"
 
 #include "base/logging.h"
+#include "net/quic/crypto/source_address_token.h"
 #include "net/quic/quic_connection.h"
 #include "net/quic/quic_flags.h"
 #include "net/quic/reliable_quic_stream.h"
@@ -17,7 +18,9 @@ QuicServerSession::QuicServerSession(const QuicConfig& config,
                                      QuicConnection* connection,
                                      QuicServerSessionVisitor* visitor)
     : QuicSession(connection, config),
-      visitor_(visitor) {}
+      visitor_(visitor),
+      bandwidth_estimate_sent_to_client_(QuicBandwidth::Zero()),
+      last_server_config_update_time_(QuicTime::Zero()) {}
 
 QuicServerSession::~QuicServerSession() {}
 
@@ -60,6 +63,79 @@ void QuicServerSession::OnWriteBlocked() {
   visitor_->OnWriteBlocked(connection());
 }
 
+void QuicServerSession::OnCongestionWindowChange(QuicTime now) {
+  if (connection()->version() <= QUIC_VERSION_21) {
+    return;
+  }
+
+  // If not enough time has passed since the last time we sent an update to the
+  // client, then return early.
+  const QuicSentPacketManager& sent_packet_manager =
+      connection()->sent_packet_manager();
+  int64 srtt_ms =
+      sent_packet_manager.GetRttStats()->SmoothedRtt().ToMilliseconds();
+  int64 now_ms = now.Subtract(last_server_config_update_time_).ToMilliseconds();
+  if (now_ms < (kMinIntervalBetweenServerConfigUpdatesRTTs * srtt_ms) ||
+      now_ms < kMinIntervalBetweenServerConfigUpdatesMs) {
+    return;
+  }
+
+  // If the bandwidth recorder does not have a valid estimate, return early.
+  const QuicSustainedBandwidthRecorder& bandwidth_recorder =
+      sent_packet_manager.SustainedBandwidthRecorder();
+  if (!bandwidth_recorder.HasEstimate()) {
+    return;
+  }
+
+  // The bandwidth recorder has recorded at least one sustained bandwidth
+  // estimate. Check that it's substantially different from the last one that
+  // we sent to the client, and if so, send the new one.
+  QuicBandwidth new_bandwidth_estimate = bandwidth_recorder.BandwidthEstimate();
+
+  int64 bandwidth_delta =
+      std::abs(new_bandwidth_estimate.ToBitsPerSecond() -
+               bandwidth_estimate_sent_to_client_.ToBitsPerSecond());
+
+  // Define "substantial" difference as a 50% increase or decrease from the
+  // last estimate.
+  bool substantial_difference =
+      bandwidth_delta >
+      0.5 * bandwidth_estimate_sent_to_client_.ToBitsPerSecond();
+  if (!substantial_difference) {
+    return;
+  }
+
+  bandwidth_estimate_sent_to_client_ = new_bandwidth_estimate;
+  DVLOG(1) << "Server: sending new bandwidth estimate (KBytes/s): "
+           << bandwidth_estimate_sent_to_client_.ToKBytesPerSecond();
+
+  // Include max bandwidth in the update.
+  QuicBandwidth max_bandwidth_estimate =
+      bandwidth_recorder.MaxBandwidthEstimate();
+  int32 max_bandwidth_timestamp = bandwidth_recorder.MaxBandwidthTimestamp();
+
+  // Fill the proto before passing it to the crypto stream to send.
+  CachedNetworkParameters cached_network_params;
+  cached_network_params.set_bandwidth_estimate_bytes_per_second(
+      bandwidth_estimate_sent_to_client_.ToBytesPerSecond());
+  cached_network_params.set_max_bandwidth_estimate_bytes_per_second(
+      max_bandwidth_estimate.ToBytesPerSecond());
+  cached_network_params.set_max_bandwidth_timestamp_seconds(
+      max_bandwidth_timestamp);
+  cached_network_params.set_min_rtt_ms(
+      sent_packet_manager.GetRttStats()->min_rtt().ToMilliseconds());
+  cached_network_params.set_previous_connection_state(
+      bandwidth_recorder.EstimateRecordedDuringSlowStart()
+          ? CachedNetworkParameters::SLOW_START
+          : CachedNetworkParameters::CONGESTION_AVOIDANCE);
+  if (!serving_region_.empty()) {
+    cached_network_params.set_serving_region(serving_region_);
+  }
+
+  crypto_stream_->SendServerConfigUpdate(&cached_network_params);
+  last_server_config_update_time_ = now;
+}
+
 bool QuicServerSession::ShouldCreateIncomingDataStream(QuicStreamId id) {
   if (id % 2 == 0) {
     DVLOG(1) << "Invalid incoming even stream_id:" << id;