htlcswitch: change ForwardPackets to return error

As part of the preparation to the switch interceptor feature, this
function is changed  to return error instead of error channel that
is closed automatically.
Returning an error channel has become complex to maintain and
implement when adding more asynchronous flows to the switch.
The change doesn't affect the current behavior which logs the
errors as before.

htlcswitch/switch_test.go

@@ -172,6 +172,13 @@ func TestSwitchSendPending(t *testing.T) {
 		t.Fatalf("unable to create alice server: %v", err)
 	}
 
+	bobPeer, err := newMockServer(
+		t, "bob", testStartingHeight, nil, testDefaultDelta,
+	)
+	if err != nil {
+		t.Fatalf("unable to create bob server: %v", err)
+	}
+
 	s, err := initSwitchWithDB(testStartingHeight, nil)
 	if err != nil {
 		t.Fatalf("unable to init switch: %v", err)
@@ -181,7 +188,7 @@ func TestSwitchSendPending(t *testing.T) {
 	}
 	defer s.Stop()
 
-	chanID1, _, aliceChanID, bobChanID := genIDs()
+	chanID1, chanID2, aliceChanID, bobChanID := genIDs()
 
 	pendingChanID := lnwire.ShortChannelID{}
 
@@ -192,6 +199,13 @@ func TestSwitchSendPending(t *testing.T) {
 		t.Fatalf("unable to add alice link: %v", err)
 	}
 
+	bobChannelLink := newMockChannelLink(
+		s, chanID2, bobChanID, bobPeer, true,
+	)
+	if err := s.AddLink(bobChannelLink); err != nil {
+		t.Fatalf("unable to add bob link: %v", err)
+	}
+
 	// Create request which should is being forwarded from Bob channel
 	// link to Alice channel link.
 	preimage, err := genPreimage()
@@ -212,7 +226,17 @@ func TestSwitchSendPending(t *testing.T) {
 
 	// Send the ADD packet, this should not be forwarded out to the link
 	// since there are no eligible links.
-	err = forwardPackets(t, s, packet)
+	if err = s.ForwardPackets(nil, packet); err != nil {
+		t.Fatal(err)
+	}
+	select {
+	case p := <-bobChannelLink.packets:
+		if p.linkFailure != nil {
+			err = p.linkFailure
+		}
+	case <-time.After(time.Second):
+		t.Fatal("no timely reply from switch")
+	}
 	linkErr, ok := err.(*LinkError)
 	if !ok {
 		t.Fatalf("expected link error, got: %T", err)
@@ -248,7 +272,7 @@ func TestSwitchSendPending(t *testing.T) {
 	packet.incomingHTLCID++
 
 	// Handle the request and checks that bob channel link received it.
-	if err := forwardPackets(t, s, packet); err != nil {
+	if err := s.ForwardPackets(nil, packet); err != nil {
 		t.Fatalf("unexpected forward failure: %v", err)
 	}
 
@@ -321,7 +345,7 @@ func TestSwitchForward(t *testing.T) {
 	}
 
 	// Handle the request and checks that bob channel link received it.
-	if err := forwardPackets(t, s, packet); err != nil {
+	if err := s.ForwardPackets(nil, packet); err != nil {
 		t.Fatal(err)
 	}
 
@@ -355,7 +379,7 @@ func TestSwitchForward(t *testing.T) {
 	}
 
 	// Handle the request and checks that payment circuit works properly.
-	if err := forwardPackets(t, s, packet); err != nil {
+	if err := s.ForwardPackets(nil, packet); err != nil {
 		t.Fatal(err)
 	}
 
@@ -450,7 +474,7 @@ func TestSwitchForwardFailAfterFullAdd(t *testing.T) {
 	}
 
 	// Handle the request and checks that bob channel link received it.
-	if err := forwardPackets(t, s, ogPacket); err != nil {
+	if err := s.ForwardPackets(nil, ogPacket); err != nil {
 		t.Fatal(err)
 	}
 
@@ -538,7 +562,7 @@ func TestSwitchForwardFailAfterFullAdd(t *testing.T) {
 	}
 
 	// Send the fail packet from the remote peer through the switch.
-	if err := <-s2.ForwardPackets(nil, fail); err != nil {
+	if err := s2.ForwardPackets(nil, fail); err != nil {
 		t.Fatalf(err.Error())
 	}
 
@@ -562,9 +586,13 @@ func TestSwitchForwardFailAfterFullAdd(t *testing.T) {
 	}
 
 	// Send the fail packet from the remote peer through the switch.
-	if err := <-s2.ForwardPackets(nil, fail); err == nil {
-		t.Fatalf("expected failure when sending duplicate fail " +
-			"with no pending circuit")
+	if err := s.ForwardPackets(nil, fail); err != nil {
+		t.Fatal(err)
+	}
+	select {
+	case <-aliceChannelLink.packets:
+		t.Fatalf("expected duplicate fail to not arrive at the destination")
+	case <-time.After(time.Second):
 	}
 }
 
@@ -645,7 +673,7 @@ func TestSwitchForwardSettleAfterFullAdd(t *testing.T) {
 	}
 
 	// Handle the request and checks that bob channel link received it.
-	if err := forwardPackets(t, s, ogPacket); err != nil {
+	if err := s.ForwardPackets(nil, ogPacket); err != nil {
 		t.Fatal(err)
 	}
 
@@ -735,7 +763,7 @@ func TestSwitchForwardSettleAfterFullAdd(t *testing.T) {
 	}
 
 	// Send the settle packet from the remote peer through the switch.
-	if err := <-s2.ForwardPackets(nil, settle); err != nil {
+	if err := s2.ForwardPackets(nil, settle); err != nil {
 		t.Fatalf(err.Error())
 	}
 
@@ -759,10 +787,14 @@ func TestSwitchForwardSettleAfterFullAdd(t *testing.T) {
 		t.Fatalf("wrong amount of circuits")
 	}
 
-	// Send the settle packet again, which should fail.
-	if err := <-s2.ForwardPackets(nil, settle); err != nil {
-		t.Fatalf("expected success when sending duplicate settle " +
-			"with no pending circuit")
+	// Send the settle packet again, which not arrive at destination.
+	if err := s2.ForwardPackets(nil, settle); err != nil {
+		t.Fatal(err)
+	}
+	select {
+	case <-bobChannelLink.packets:
+		t.Fatalf("expected duplicate fail to not arrive at the destination")
+	case <-time.After(time.Second):
 	}
 }
 
@@ -843,7 +875,7 @@ func TestSwitchForwardDropAfterFullAdd(t *testing.T) {
 	}
 
 	// Handle the request and checks that bob channel link received it.
-	if err := forwardPackets(t, s, ogPacket); err != nil {
+	if err := s.ForwardPackets(nil, ogPacket); err != nil {
 		t.Fatal(err)
 	}
 
@@ -916,7 +948,7 @@ func TestSwitchForwardDropAfterFullAdd(t *testing.T) {
 
 	// Resend the failed htlc. The packet will be dropped silently since the
 	// switch will detect that it has been half added previously.
-	if err := <-s2.ForwardPackets(nil, ogPacket); err != nil {
+	if err := s2.ForwardPackets(nil, ogPacket); err != nil {
 		t.Fatal(err)
 	}
 
@@ -1008,7 +1040,7 @@ func TestSwitchForwardFailAfterHalfAdd(t *testing.T) {
 	}
 
 	// Handle the request and checks that bob channel link received it.
-	if err := forwardPackets(t, s, ogPacket); err != nil {
+	if err := s.ForwardPackets(nil, ogPacket); err != nil {
 		t.Fatal(err)
 	}
 
@@ -1076,7 +1108,7 @@ func TestSwitchForwardFailAfterHalfAdd(t *testing.T) {
 
 	// Resend the failed htlc, it should be returned to alice since the
 	// switch will detect that it has been half added previously.
-	err = <-s2.ForwardPackets(nil, ogPacket)
+	err = s2.ForwardPackets(nil, ogPacket)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -1174,7 +1206,7 @@ func TestSwitchForwardCircuitPersistence(t *testing.T) {
 	}
 
 	// Handle the request and checks that bob channel link received it.
-	if err := forwardPackets(t, s, ogPacket); err != nil {
+	if err := s.ForwardPackets(nil, ogPacket); err != nil {
 		t.Fatal(err)
 	}
 
@@ -1264,7 +1296,7 @@ func TestSwitchForwardCircuitPersistence(t *testing.T) {
 	}
 
 	// Handle the request and checks that payment circuit works properly.
-	if err := <-s2.ForwardPackets(nil, ogPacket); err != nil {
+	if err := s2.ForwardPackets(nil, ogPacket); err != nil {
 		t.Fatal(err)
 	}
 
@@ -1414,7 +1446,17 @@ func TestCircularForwards(t *testing.T) {
 
 			// Attempt to forward the packet and check for the expected
 			// error.
-			err = forwardPackets(t, s, packet)
+			if err = s.ForwardPackets(nil, packet); err != nil {
+				t.Fatal(err)
+			}
+			select {
+			case p := <-aliceChannelLink.packets:
+				if p.linkFailure != nil {
+					err = p.linkFailure
+				}
+			case <-time.After(time.Second):
+				t.Fatal("no timely reply from switch")
+			}
 			if !reflect.DeepEqual(err, test.expectedErr) {
 				t.Fatalf("expected: %v, got: %v",
 					test.expectedErr, err)
@@ -1634,18 +1676,30 @@ func testSkipIneligibleLinksMultiHopForward(t *testing.T,
 	}
 
 	// The request to forward should fail as
-	err = forwardPackets(t, s, packet)
-
+	if err := s.ForwardPackets(nil, packet); err != nil {
+		t.Fatal(err)
+	}
+	var linkError *LinkError
+	select {
+	case p := <-aliceChannelLink.packets:
+		linkError = p.linkFailure
+	case p := <-bobChannelLink1.packets:
+		linkError = p.linkFailure
+	case p := <-bobChannelLink2.packets:
+		linkError = p.linkFailure
+	case <-time.After(time.Second):
+		t.Fatal("no timely reply from switch")
+	}
 	failure := obfuscator.(*mockObfuscator).failure
 	if testCase.expectedReply == lnwire.CodeNone {
-		if err != nil {
+		if linkError != nil {
 			t.Fatalf("forwarding should have succeeded")
 		}
 		if failure != nil {
 			t.Fatalf("unexpected failure %T", failure)
 		}
 	} else {
-		if err == nil {
+		if linkError == nil {
 			t.Fatalf("forwarding should have failed due to " +
 				"inactive link")
 		}
@@ -1793,7 +1847,7 @@ func TestSwitchCancel(t *testing.T) {
 	}
 
 	// Handle the request and checks that bob channel link received it.
-	if err := forwardPackets(t, s, request); err != nil {
+	if err := s.ForwardPackets(nil, request); err != nil {
 		t.Fatal(err)
 	}
 
@@ -1825,7 +1879,7 @@ func TestSwitchCancel(t *testing.T) {
 	}
 
 	// Handle the request and checks that payment circuit works properly.
-	if err := forwardPackets(t, s, request); err != nil {
+	if err := s.ForwardPackets(nil, request); err != nil {
 		t.Fatal(err)
 	}
 
@@ -1908,7 +1962,7 @@ func TestSwitchAddSamePayment(t *testing.T) {
 	}
 
 	// Handle the request and checks that bob channel link received it.
-	if err := forwardPackets(t, s, request); err != nil {
+	if err := s.ForwardPackets(nil, request); err != nil {
 		t.Fatal(err)
 	}
 
@@ -1938,7 +1992,7 @@ func TestSwitchAddSamePayment(t *testing.T) {
 	}
 
 	// Handle the request and checks that bob channel link received it.
-	if err := forwardPackets(t, s, request); err != nil {
+	if err := s.ForwardPackets(nil, request); err != nil {
 		t.Fatal(err)
 	}
 
@@ -1967,7 +2021,7 @@ func TestSwitchAddSamePayment(t *testing.T) {
 	}
 
 	// Handle the request and checks that payment circuit works properly.
-	if err := forwardPackets(t, s, request); err != nil {
+	if err := s.ForwardPackets(nil, request); err != nil {
 		t.Fatal(err)
 	}
 
@@ -1993,7 +2047,7 @@ func TestSwitchAddSamePayment(t *testing.T) {
 	}
 
 	// Handle the request and checks that payment circuit works properly.
-	if err := forwardPackets(t, s, request); err != nil {
+	if err := s.ForwardPackets(nil, request); err != nil {
 		t.Fatal(err)
 	}
 
@@ -2136,7 +2190,7 @@ func TestSwitchSendPayment(t *testing.T) {
 		},
 	}
 
-	if err := forwardPackets(t, s, packet); err != nil {
+	if err := s.ForwardPackets(nil, packet); err != nil {
 		t.Fatalf("can't forward htlc packet: %v", err)
 	}
 
@@ -2631,7 +2685,7 @@ func TestInvalidFailure(t *testing.T) {
 		},
 	}
 
-	if err := forwardPackets(t, s, packet); err != nil {
+	if err := s.ForwardPackets(nil, packet); err != nil {
 		t.Fatalf("can't forward htlc packet: %v", err)
 	}
 
@@ -3057,17 +3111,3 @@ func getThreeHopEvents(channels *clusterChannels, htlcID uint64,
 
 	return aliceEvents, bobEvents, carolEvents
 }
-
-// forwardPackets forwards packets to the switch and enforces a timeout on the
-// reply.
-func forwardPackets(t *testing.T, s *Switch, packets ...*htlcPacket) error {
-
-	select {
-	case err := <-s.ForwardPackets(nil, packets...):
-		return err
-
-	case <-time.After(time.Second):
-		t.Fatal("no timely reply from switch")
-		return nil
-	}
-}