routing: fail stale HTLC attempts during startup

This commit adds a check during router's startup and fails the inflight
HTLCs if they are routing using channels unknown to us. The channels are
unknown because they are already closed, usually long time ago.

routing/router_test.go

@@ -93,6 +93,10 @@ func (c *testCtx) getChannelIDFromAlias(t *testing.T, a, b string) uint64 {
 	return channelID
 }
 
+func mockFetchClosedChannels(_ bool) ([]*channeldb.ChannelCloseSummary, error) {
+	return nil, nil
+}
+
 func createTestCtxFromGraphInstance(t *testing.T, startingHeight uint32,
 	graphInstance *testGraphInstance) *testCtx {
 
@@ -158,9 +162,10 @@ func createTestCtxFromGraphInstanceAssumeValid(t *testing.T,
 			next := atomic.AddUint64(&uniquePaymentID, 1)
 			return next, nil
 		},
-		PathFindingConfig:  pathFindingConfig,
-		Clock:              clock.NewTestClock(time.Unix(1, 0)),
-		ApplyChannelUpdate: graphBuilder.ApplyChannelUpdate,
+		PathFindingConfig:   pathFindingConfig,
+		Clock:               clock.NewTestClock(time.Unix(1, 0)),
+		ApplyChannelUpdate:  graphBuilder.ApplyChannelUpdate,
+		FetchClosedChannels: mockFetchClosedChannels,
 	})
 	require.NoError(t, router.Start(), "unable to start router")
 
@@ -2170,6 +2175,7 @@ func TestSendToRouteSkipTempErrSuccess(t *testing.T) {
 		NextPaymentID: func() (uint64, error) {
 			return 0, nil
 		},
+		FetchClosedChannels: mockFetchClosedChannels,
 	}}
 
 	// Register mockers with the expected method calls.
@@ -2253,6 +2259,7 @@ func TestSendToRouteSkipTempErrNonMPP(t *testing.T) {
 		NextPaymentID: func() (uint64, error) {
 			return 0, nil
 		},
+		FetchClosedChannels: mockFetchClosedChannels,
 	}}
 
 	// Expect an error to be returned.
@@ -2307,6 +2314,7 @@ func TestSendToRouteSkipTempErrTempFailure(t *testing.T) {
 		NextPaymentID: func() (uint64, error) {
 			return 0, nil
 		},
+		FetchClosedChannels: mockFetchClosedChannels,
 	}}
 
 	// Create the error to be returned.
@@ -2389,6 +2397,7 @@ func TestSendToRouteSkipTempErrPermanentFailure(t *testing.T) {
 		NextPaymentID: func() (uint64, error) {
 			return 0, nil
 		},
+		FetchClosedChannels: mockFetchClosedChannels,
 	}}
 
 	// Create the error to be returned.
@@ -2475,6 +2484,7 @@ func TestSendToRouteTempFailure(t *testing.T) {
 		NextPaymentID: func() (uint64, error) {
 			return 0, nil
 		},
+		FetchClosedChannels: mockFetchClosedChannels,
 	}}
 
 	// Create the error to be returned.