Fix race between activeStreams and bdp window size

internal/transport/http2_client.go

@@ -78,6 +78,7 @@ type http2Client struct {
 	framer *framer
 	// controlBuf delivers all the control related tasks (e.g., window
 	// updates, reset streams, and various settings) to the controller.
+	// Do not access controlBuf with mu held.
 	controlBuf *controlBuffer
 	fc         *trInFlow
 	// The scheme used: https if TLS is on, http otherwise.
@@ -109,6 +110,7 @@ type http2Client struct {
 	waitingStreams        uint32
 	nextID                uint32
 
+	// Do not access controlBuf with mu held.
 	mu            sync.Mutex // guard the following variables
 	state         transportState
 	activeStreams map[uint32]*Stream
@@ -685,7 +687,6 @@ func (t *http2Client) NewStream(ctx context.Context, callHdr *CallHdr) (*Stream,
 				cleanup(err)
 				return err
 			}
-			t.activeStreams[id] = s
 			if channelz.IsOn() {
 				atomic.AddInt64(&t.czData.streamsStarted, 1)
 				atomic.StoreInt64(&t.czData.lastStreamCreatedTime, time.Now().UnixNano())
@@ -719,6 +720,13 @@ func (t *http2Client) NewStream(ctx context.Context, callHdr *CallHdr) (*Stream,
 		t.nextID += 2
 		s.id = h.streamID
 		s.fc = &inFlow{limit: uint32(t.initialWindowSize)}
+		t.mu.Lock()
+		if t.activeStreams == nil { // Can be niled from Close().
+			t.mu.Unlock()
+			return false // Don't create a stream if the transport is already closed.
+		}
+		t.activeStreams[s.id] = s
+		t.mu.Unlock()
 		if t.streamQuota > 0 && t.waitingStreams > 0 {
 			select {
 			case t.streamsQuotaAvailable <- struct{}{}:
@@ -744,13 +752,7 @@ func (t *http2Client) NewStream(ctx context.Context, callHdr *CallHdr) (*Stream,
 	}
 	for {
 		success, err := t.controlBuf.executeAndPut(func(it interface{}) bool {
-			if !checkForStreamQuota(it) {
-				return false
-			}
-			if !checkForHeaderListSize(it) {
-				return false
-			}
-			return true
+			return checkForHeaderListSize(it) && checkForStreamQuota(it)
 		}, hdr)
 		if err != nil {
 			// Connection closed.
@@ -1003,13 +1005,13 @@ func (t *http2Client) updateWindow(s *Stream, n uint32) {
 // for the transport and the stream based on the current bdp
 // estimation.
 func (t *http2Client) updateFlowControl(n uint32) {
-	t.mu.Lock()
-	for _, s := range t.activeStreams {
-		s.fc.newLimit(n)
-	}
-	t.mu.Unlock()
 	updateIWS := func(interface{}) bool {
 		t.initialWindowSize = int32(n)
+		t.mu.Lock()
+		for _, s := range t.activeStreams {
+			s.fc.newLimit(n)
+		}
+		t.mu.Unlock()
 		return true
 	}
 	t.controlBuf.executeAndPut(updateIWS, &outgoingWindowUpdate{streamID: 0, increment: t.fc.newLimit(n)})
@@ -1215,7 +1217,7 @@ func (t *http2Client) handleGoAway(f *http2.GoAwayFrame) {
 	default:
 		t.setGoAwayReason(f)
 		close(t.goAway)
-		t.controlBuf.put(&incomingGoAway{})
+		defer t.controlBuf.put(&incomingGoAway{}) // Defer as t.mu is currently held.
 		// Notify the clientconn about the GOAWAY before we set the state to
 		// draining, to allow the client to stop attempting to create streams
 		// before disallowing new streams on this connection.

test/end2end_test.go

@@ -8041,3 +8041,39 @@ func (s) TestServerClosesConn(t *testing.T) {
 	}
 	t.Fatalf("timed out waiting for conns to be closed by server; still open: %v", atomic.LoadInt32(&wrapLis.connsOpen))
 }
+
+// TestUnexpectedEOF tests a scenario where a client invokes two unary RPC
+// calls. The first call receives a payload which exceeds max grpc receive
+// message length, and the second gets a large response. This second RPC should
+// not fail with unexpected.EOF.
+func (s) TestUnexpectedEOF(t *testing.T) {
+	ss := &stubserver.StubServer{
+		UnaryCallF: func(ctx context.Context, in *testpb.SimpleRequest) (*testpb.SimpleResponse, error) {
+			return &testpb.SimpleResponse{
+				Payload: &testpb.Payload{
+					Body: bytes.Repeat([]byte("a"), int(in.ResponseSize)),
+				},
+			}, nil
+		},
+	}
+	if err := ss.Start([]grpc.ServerOption{}); err != nil {
+		t.Fatalf("Error starting endpoint server: %v", err)
+	}
+	defer ss.Stop()
+
+	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
+	defer cancel()
+	for i := 0; i < 10; i++ {
+		// exceeds grpc.DefaultMaxRecvMessageSize, this should error with
+		// RESOURCE_EXHAUSTED error.
+		_, err := ss.Client.UnaryCall(ctx, &testpb.SimpleRequest{ResponseSize: 4194304})
+		if code := status.Code(err); code != codes.ResourceExhausted {
+			t.Fatalf("UnaryCall RPC returned error: %v, want status code %v", err, codes.ResourceExhausted)
+		}
+		// Larger response that doesn't exceed DefaultMaxRecvMessageSize, this
+		// should work normally.
+		if _, err := ss.Client.UnaryCall(ctx, &testpb.SimpleRequest{ResponseSize: 275075}); err != nil {
+			t.Fatalf("UnaryCall RPC failed: %v", err)
+		}
+	}
+}