http2: Change accounting of WINDOW_UPDATE frames (#14924)

Signed-off-by: Yan Avlasov <yavlasov@google.com>

Mirrored from https://github.com/envoyproxy/envoy @ 5bdcdd63b348829b5e0ea1612c97168c8ce41750

envoy/config/core/v3/protocol.proto

@@ -301,9 +301,12 @@ message Http2ProtocolOptions {
   // of PRIORITY frames received over the lifetime of connection exceeds the value calculated
   // using this formula::
   //
-  //     max_inbound_priority_frames_per_stream * (1 + inbound_streams)
+  //   max_inbound_priority_frames_per_stream * (1 + opened_streams)
   //
-  // the connection is terminated. The ``http2.inbound_priority_frames_flood`` stat tracks
+  // the connection is terminated. For downstream connections the `opened_streams` is incremented when
+  // Envoy receives complete response headers from the upstream server. For upstream connection the
+  // `opened_streams` is incremented when Envoy send the HEADERS frame for a new stream. The
+  // ``http2.inbound_priority_frames_flood`` stat tracks
   // the number of connections terminated due to flood mitigation. The default limit is 100.
   // NOTE: flood and abuse mitigation for upstream connections is presently enabled by the
   // `envoy.reloadable_features.upstream_http2_flood_checks` flag.
@@ -313,11 +316,14 @@ message Http2ProtocolOptions {
   // of WINDOW_UPDATE frames received over the lifetime of connection exceeds the value calculated
   // using this formula::
   //
-  //     1 + 2 * (inbound_streams +
-  //              max_inbound_window_update_frames_per_data_frame_sent * outbound_data_frames)
+  //   5 + 2 * (opened_streams +
+  //            max_inbound_window_update_frames_per_data_frame_sent * outbound_data_frames)
   //
-  // the connection is terminated. The ``http2.inbound_priority_frames_flood`` stat tracks
-  // the number of connections terminated due to flood mitigation. The default limit is 10.
+  // the connection is terminated. For downstream connections the `opened_streams` is incremented when
+  // Envoy receives complete response headers from the upstream server. For upstream connections the
+  // `opened_streams` is incremented when Envoy sends the HEADERS frame for a new stream. The
+  // ``http2.inbound_priority_frames_flood`` stat tracks the number of connections terminated due to
+  // flood mitigation. The default max_inbound_window_update_frames_per_data_frame_sent value is 10.
   // Setting this to 1 should be enough to support HTTP/2 implementations with basic flow control,
   // but more complex implementations that try to estimate available bandwidth require at least 2.
   // NOTE: flood and abuse mitigation for upstream connections is presently enabled by the

envoy/config/core/v4alpha/protocol.proto

@@ -308,9 +308,12 @@ message Http2ProtocolOptions {
   // of PRIORITY frames received over the lifetime of connection exceeds the value calculated
   // using this formula::
   //
-  //     max_inbound_priority_frames_per_stream * (1 + inbound_streams)
+  //   max_inbound_priority_frames_per_stream * (1 + opened_streams)
   //
-  // the connection is terminated. The ``http2.inbound_priority_frames_flood`` stat tracks
+  // the connection is terminated. For downstream connections the `opened_streams` is incremented when
+  // Envoy receives complete response headers from the upstream server. For upstream connection the
+  // `opened_streams` is incremented when Envoy send the HEADERS frame for a new stream. The
+  // ``http2.inbound_priority_frames_flood`` stat tracks
   // the number of connections terminated due to flood mitigation. The default limit is 100.
   // NOTE: flood and abuse mitigation for upstream connections is presently enabled by the
   // `envoy.reloadable_features.upstream_http2_flood_checks` flag.
@@ -320,11 +323,14 @@ message Http2ProtocolOptions {
   // of WINDOW_UPDATE frames received over the lifetime of connection exceeds the value calculated
   // using this formula::
   //
-  //     1 + 2 * (inbound_streams +
-  //              max_inbound_window_update_frames_per_data_frame_sent * outbound_data_frames)
+  //   5 + 2 * (opened_streams +
+  //            max_inbound_window_update_frames_per_data_frame_sent * outbound_data_frames)
   //
-  // the connection is terminated. The ``http2.inbound_priority_frames_flood`` stat tracks
-  // the number of connections terminated due to flood mitigation. The default limit is 10.
+  // the connection is terminated. For downstream connections the `opened_streams` is incremented when
+  // Envoy receives complete response headers from the upstream server. For upstream connections the
+  // `opened_streams` is incremented when Envoy sends the HEADERS frame for a new stream. The
+  // ``http2.inbound_priority_frames_flood`` stat tracks the number of connections terminated due to
+  // flood mitigation. The default max_inbound_window_update_frames_per_data_frame_sent value is 10.
   // Setting this to 1 should be enough to support HTTP/2 implementations with basic flow control,
   // but more complex implementations that try to estimate available bandwidth require at least 2.
   // NOTE: flood and abuse mitigation for upstream connections is presently enabled by the