internal/transport: convert ConnectionError to Unavailable status…

… when writing headers (#6891)

internal/transport/http2_server.go

@@ -960,7 +960,12 @@ func (t *http2Server) WriteHeader(s *Stream, md metadata.MD) error {
 		}
 	}
 	if err := t.writeHeaderLocked(s); err != nil {
-		return status.Convert(err).Err()
+		switch e := err.(type) {
+		case ConnectionError:
+			return status.Error(codes.Unavailable, e.Desc)
+		default:
+			return status.Convert(err).Err()
+		}
 	}
 	return nil
 }

internal/transport/transport_test.go

@@ -45,6 +45,7 @@ import (
 	"google.golang.org/grpc/internal/grpctest"
 	"google.golang.org/grpc/internal/leakcheck"
 	"google.golang.org/grpc/internal/testutils"
+	"google.golang.org/grpc/metadata"
 	"google.golang.org/grpc/resolver"
 	"google.golang.org/grpc/status"
 )
@@ -2136,6 +2137,70 @@ func (s) TestHeadersHTTPStatusGRPCStatus(t *testing.T) {
 	}
 }
 
+func (s) TestWriteHeaderConnectionError(t *testing.T) {
+	server, client, cancel := setUp(t, 0, notifyCall)
+	defer cancel()
+	defer server.stop()
+
+	waitWhileTrue(t, func() (bool, error) {
+		server.mu.Lock()
+		defer server.mu.Unlock()
+
+		if len(server.conns) == 0 {
+			return true, fmt.Errorf("timed-out while waiting for connection to be created on the server")
+		}
+		return false, nil
+	})
+
+	server.mu.Lock()
+
+	if len(server.conns) != 1 {
+		t.Fatalf("Server has %d connections from the client, want 1", len(server.conns))
+	}
+
+	// Get the server transport for the connecton to the client.
+	var serverTransport *http2Server
+	for k := range server.conns {
+		serverTransport = k.(*http2Server)
+	}
+	notifyChan := make(chan struct{})
+	server.h.notify = notifyChan
+	server.mu.Unlock()
+
+	ctx, cancel := context.WithTimeout(context.Background(), defaultTestTimeout)
+	defer cancel()
+	cstream, err := client.NewStream(ctx, &CallHdr{})
+	if err != nil {
+		t.Fatalf("Client failed to create first stream. Err: %v", err)
+	}
+
+	<-notifyChan // Wait for server stream to be established.
+	var sstream *Stream
+	// Access stream on the server.
+	serverTransport.mu.Lock()
+	for _, v := range serverTransport.activeStreams {
+		if v.id == cstream.id {
+			sstream = v
+		}
+	}
+	serverTransport.mu.Unlock()
+	if sstream == nil {
+		t.Fatalf("Didn't find stream corresponding to client cstream.id: %v on the server", cstream.id)
+	}
+
+	client.Close(fmt.Errorf("closed manually by test"))
+
+	// Wait for server transport to be closed.
+	<-serverTransport.done
+
+	// Write header on a closed server transport.
+	err = serverTransport.WriteHeader(sstream, metadata.MD{})
+	st := status.Convert(err)
+	if st.Code() != codes.Unavailable {
+		t.Fatalf("WriteHeader() failed with status code %s, want %s", st.Code(), codes.Unavailable)
+	}
+}
+
 func (s) TestPingPong1B(t *testing.T) {
 	runPingPongTest(t, 1)
 }