relnote: Allow changing initial flow control window via connection options. Protected by --quic_lar…

net/quic/core/quic_session.cc

Index: net/quic/core/quic_session.cc
diff --git a/net/quic/core/quic_session.cc b/net/quic/core/quic_session.cc
index ced354aaeb803c8a50cf489c862516711d86493c..c0bd4906fa70094bdc873a590ca1683818decb7c 100644
--- a/net/quic/core/quic_session.cc
+++ b/net/quic/core/quic_session.cc
@@ -55,13 +55,15 @@ void QuicSession::Initialize() {
 }
 
 QuicSession::~QuicSession() {
-  DLOG_IF(WARNING, num_locally_closed_incoming_streams_highest_offset() >
-                       max_open_incoming_streams_)
+  DLOG_IF(WARNING,
+         num_locally_closed_incoming_streams_highest_offset() >
+             max_open_incoming_streams_)
       << "Surprisingly high number of locally closed peer initiated streams"
          "still waiting for final byte offset: "
       << num_locally_closed_incoming_streams_highest_offset();
-  DLOG_IF(WARNING, GetNumLocallyClosedOutgoingStreamsHighestOffset() >
-                       max_open_outgoing_streams_)
+  DLOG_IF(WARNING,
+          GetNumLocallyClosedOutgoingStreamsHighestOffset() >
+             max_open_outgoing_streams_)
       << "Surprisingly high number of locally closed self initiated streams"
          "still waiting for final byte offset: "
       << GetNumLocallyClosedOutgoingStreamsHighestOffset();
@@ -439,6 +441,28 @@ void QuicSession::OnConfigNegotiated() {
     max_streams = config_.MaxStreamsPerConnection();
   }
   set_max_open_outgoing_streams(max_streams);
+  if (FLAGS_quic_large_ifw_options &&
+      perspective() == Perspective::IS_SERVER) {
+    if (config_.HasReceivedConnectionOptions()) {
+      // The following variations change the initial receive flow control
+      // window sizes.
+      if (ContainsQuicTag(config_.ReceivedConnectionOptions(), kIFW6)) {
+        AdjustInitialFlowControlWindows(64 * 1024);
+      }
+      if (ContainsQuicTag(config_.ReceivedConnectionOptions(), kIFW7)) {
+        AdjustInitialFlowControlWindows(128 * 1024);
+      }
+      if (ContainsQuicTag(config_.ReceivedConnectionOptions(), kIFW8)) {
+        AdjustInitialFlowControlWindows(256 * 1024);
+      }
+      if (ContainsQuicTag(config_.ReceivedConnectionOptions(), kIFW9)) {
+        AdjustInitialFlowControlWindows(512 * 1024);
+      }
+      if (ContainsQuicTag(config_.ReceivedConnectionOptions(), kIFWA)) {
+        AdjustInitialFlowControlWindows(1024 * 1024);
+      }
+    }
+  }
 
   if (version <= QUIC_VERSION_34) {
     // A small number of additional incoming streams beyond the limit should be
@@ -472,6 +496,30 @@ void QuicSession::OnConfigNegotiated() {
   }
 }
 
+void QuicSession::AdjustInitialFlowControlWindows(size_t stream_window) {
+  const float session_window_multiplier =
+      config_.GetInitialStreamFlowControlWindowToSend()
+          ? static_cast<float>(
+                config_.GetInitialSessionFlowControlWindowToSend()) /
+                config_.GetInitialStreamFlowControlWindowToSend()
+          : 1.5;
+
+  DVLOG(1) << ENDPOINT << "Set stream receive window to " << stream_window;
+  config_.SetInitialStreamFlowControlWindowToSend(stream_window);
+
+  size_t session_window = session_window_multiplier * stream_window;
+  DVLOG(1) << ENDPOINT << "Set session receive window to " << session_window;
+  config_.SetInitialSessionFlowControlWindowToSend(session_window);
+  flow_controller_.UpdateReceiveWindowSize(session_window);
+  // Inform all existing streams about the new window.
+  for (auto const& kv : static_stream_map_) {
+    kv.second->flow_controller()->UpdateReceiveWindowSize(stream_window);
+  }
+  for (auto const& kv : dynamic_stream_map_) {
+    kv.second->flow_controller()->UpdateReceiveWindowSize(stream_window);
+  }
+}
+
 void QuicSession::HandleFrameOnNonexistentOutgoingStream(
     QuicStreamId stream_id) {
   DCHECK(!IsClosedStream(stream_id));