[konnectivity-client] Send best-effort DIAL_CLS on dial timeout

konnectivity-client/pkg/client/client.go

@@ -327,9 +327,11 @@ func (t *grpcTunnel) DialContext(requestCtx context.Context, protocol, address s
 		t.connsLock.Unlock()
 	case <-time.After(30 * time.Second):
 		klog.V(5).InfoS("Timed out waiting for DialResp", "dialID", random)
+		go t.closeDial(random)
 		return nil, &dialFailure{"dial timeout, backstop", DialFailureTimeout}
 	case <-requestCtx.Done():
 		klog.V(5).InfoS("Context canceled waiting for DialResp", "ctxErr", requestCtx.Err(), "dialID", random)
+		go t.closeDial(random)
 		return nil, &dialFailure{"dial timeout, context", DialFailureContext}
 	}
 
@@ -340,6 +342,21 @@ func (t *grpcTunnel) Done() <-chan struct{} {
 	return t.done
 }
 
+// Send a best-effort DIAL_CLS request for the given dial ID.
+func (t *grpcTunnel) closeDial(dialID int64) {
+	req := &client.Packet{
+		Type: client.PacketType_DIAL_CLS,
+		Payload: &client.Packet_CloseDial{
+			CloseDial: &client.CloseDial{
+				Random: dialID,
+			},
+		},
+	}
+	if err := t.stream.Send(req); err != nil {
+		klog.V(5).InfoS("Failed to send DIAL_CLS", "err", err, "dialID", dialID)
+	}
+}
+
 func GetDialFailureReason(err error) (isDialFailure bool, reason DialFailureReason) {
 	var df *dialFailure
 	if errors.As(err, &df) {

konnectivity-client/pkg/client/client_test.go

@@ -310,6 +310,11 @@ func TestDial_RequestContextCancelled(t *testing.T) {
 		reqCancel()
 		return nil // don't respond
 	}
+	closeCh := make(chan struct{})
+	ts.handlers[client.PacketType_DIAL_CLS] = func(*client.Packet) *client.Packet {
+		close(closeCh)
+		return nil // don't respond
+	}
 
 	defer ps.Close()
 	defer s.Close()
@@ -332,6 +337,12 @@ func TestDial_RequestContextCancelled(t *testing.T) {
 	}
 
 	ts.assertPacketType(0, client.PacketType_DIAL_REQ)
+	select {
+	case <-closeCh:
+		ts.assertPacketType(1, client.PacketType_DIAL_CLS)
+	case <-time.After(30 * time.Second):
+		t.Fatal("Timed out waiting for DIAL_CLS packet")
+	}
 }
 
 func TestDial_BackendError(t *testing.T) {