routing: check for invalid routes

routing/router_test.go

@@ -3339,6 +3339,74 @@ func TestSendToRouteStructuredError(t *testing.T) {
 	}
 }
 
+// TestSendToRouteMaxHops asserts that SendToRoute fails when using a route that
+// exceeds the maximum number of hops.
+func TestSendToRouteMaxHops(t *testing.T) {
+	t.Parallel()
+
+	// Setup a two node network.
+	chanCapSat := btcutil.Amount(100000)
+	testChannels := []*testChannel{
+		symmetricTestChannel("a", "b", chanCapSat, &testChannelPolicy{
+			Expiry:  144,
+			FeeRate: 400,
+			MinHTLC: 1,
+			MaxHTLC: lnwire.NewMSatFromSatoshis(chanCapSat),
+		}, 1),
+	}
+
+	testGraph, err := createTestGraphFromChannels(testChannels, "a")
+	if err != nil {
+		t.Fatalf("unable to create graph: %v", err)
+	}
+	defer testGraph.cleanUp()
+
+	const startingBlockHeight = 101
+
+	ctx, cleanUp, err := createTestCtxFromGraphInstance(
+		startingBlockHeight, testGraph,
+	)
+	if err != nil {
+		t.Fatalf("unable to create router: %v", err)
+	}
+	defer cleanUp()
+
+	// Create a 30 hop route that exceeds the maximum hop limit.
+	const payAmt = lnwire.MilliSatoshi(10000)
+	hopA := ctx.aliases["a"]
+	hopB := ctx.aliases["b"]
+
+	var hops []*route.Hop
+	for i := 0; i < 15; i++ {
+		hops = append(hops, &route.Hop{
+			ChannelID:     1,
+			PubKeyBytes:   hopB,
+			AmtToForward:  payAmt,
+			LegacyPayload: true,
+		})
+
+		hops = append(hops, &route.Hop{
+			ChannelID:     1,
+			PubKeyBytes:   hopA,
+			AmtToForward:  payAmt,
+			LegacyPayload: true,
+		})
+	}
+
+	rt, err := route.NewRouteFromHops(payAmt, 100, ctx.aliases["a"], hops)
+	if err != nil {
+		t.Fatalf("unable to create route: %v", err)
+	}
+
+	// Send off the payment request to the router. We expect an error back
+	// indicating that the route is too long.
+	var payment lntypes.Hash
+	_, err = ctx.router.SendToRoute(payment, rt)
+	if err != route.ErrMaxRouteHopsExceeded {
+		t.Fatalf("expected ErrMaxRouteHopsExceeded, but got %v", err)
+	}
+}
+
 // TestBuildRoute tests whether correct routes are built.
 func TestBuildRoute(t *testing.T) {
 	// Setup a three node network.