http2: send an error of FLOW_CONTROL_ERROR when exceed the maximum octets

According to rfc9113 "https://www.rfc-editor.org/rfc/rfc9113.html#section-6.9.1-7", if a sender receives a WINDOW_UPDATE that causes a flow-control window to exceed this maximum, it MUST terminate either the stream or the connection, as appropriate. For streams, the sender sends a RST_STREAM with an error code of FLOW_CONTROL_ERROR.

Change-Id: I5e14db247012ebc860a23053f73e70b83c7cd85d
GitHub-Last-Rev: d1a85d3
GitHub-Pull-Request: #204
Reviewed-on: https://go-review.googlesource.com/c/net/+/561035
Auto-Submit: Damien Neil <dneil@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: Damien Neil <dneil@google.com>

Author: bestgopher

http2/transport.go

@@ -2911,6 +2911,15 @@ func (rl *clientConnReadLoop) processWindowUpdate(f *WindowUpdateFrame) error {
 		fl = &cs.flow
 	}
 	if !fl.add(int32(f.Increment)) {
+		// For stream, the sender sends RST_STREAM with an error code of FLOW_CONTROL_ERROR
+		if cs != nil {
+			rl.endStreamError(cs, StreamError{
+				StreamID: f.StreamID,
+				Code:     ErrCodeFlowControl,
+			})
+			return nil
+		}
+
 		return ConnectionError(ErrCodeFlowControl)
 	}
 	cc.cond.Broadcast()