routerrpc: fix estimateroutefee for public route hints #9433

hieblmi · 2025-01-22T15:07:06Z

This PR attempts to fix #9431, an edge case in EstimateRouteFee.

We want to send a probe in case a route hint contains a public edge.

coderabbitai · 2025-01-22T15:07:14Z

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ziggie1984

Thanks for the quick fix, looking good.

I think a unit-test might be worthwhile for the new behaviour.

ziggie1984 · 2025-01-22T21:25:34Z

lnrpc/routerrpc/router_backend.go

@@ -44,6 +45,11 @@ type RouterBackend struct {
 	// SelfNode is the vertex of the node sending the payment.
 	SelfNode route.Vertex

+	// FetchChannelInfo is a closure that we'll use the fetch the latest
+	// routing state for a particular channel identified by its channel ID.


routing state? maybe just write ChannelPolicy ?

ziggie1984 · 2025-01-22T22:04:42Z

lnrpc/routerrpc/router_server.go

@@ -627,12 +628,13 @@ func (s *Server) probePaymentRequest(ctx context.Context, paymentRequest string,
 // isLSP checks if the route hints indicate an LSP. An LSP is indicated with
 // true if the last node in each route hint has the same node id, false
 // otherwise.
-func isLSP(routeHints [][]zpay32.HopHint) bool {
+func isLSP(routeHints [][]zpay32.HopHint, routerBackend *RouterBackend) bool {


why not make isLSP part of ther routerbackend func (s *Server) isLSP makes it way cleaner ?

I think passing in a function in instead is good enough, also makes it easier to mock in a unit test

ziggie1984 · 2025-01-22T22:12:03Z

lnrpc/routerrpc/router_server.go

@@ -649,7 +651,16 @@ func isLSP(routeHints [][]zpay32.HopHint) bool {
 		}
 	}

-	return true
+	// If the ref node hint contains a public channel we can send a probe to


let's move it at the beginning so we can do the check first something like this:
We just check, does the refChanID exist, if it does we exit early.

_, _, _, err := routerBackend.FetchChannelInfo(refHint.ChannelID) if err == nil { return false }

ziggie1984 · 2025-01-22T22:14:54Z

rpcserver.go

+			*models.ChannelEdgePolicy, *models.ChannelEdgePolicy,
+			error) {
+
+			info, policy1, policy2, err := graph.FetchChannelEdgesByID(chanID) //nolint:ll


put nolint in a line before.

ziggie1984 · 2025-01-22T22:18:05Z

lnrpc/routerrpc/router_server_test.go

@@ -387,7 +388,13 @@ func TestIsLsp(t *testing.T) {

 	for _, tc := range lspTestCases {
 		t.Run(tc.name, func(t *testing.T) {
-			require.Equal(t, tc.isLsp, isLSP(tc.routeHints))
+			require.Equal(t, tc.isLsp, isLSP(tc.routeHints, &RouterBackend{


I think it makes sense to add a unit test for this behaviour.

ziggie1984 · 2025-01-22T22:21:17Z

lnrpc/routerrpc/router_backend.go

@@ -44,6 +45,11 @@ type RouterBackend struct {
 	// SelfNode is the vertex of the node sending the payment.
 	SelfNode route.Vertex

+	// FetchChannelInfo is a closure that we'll use the fetch the latest
+	// routing state for a particular channel identified by its channel ID.
+	FetchChannelInfo func(chanID uint64) (*models.ChannelEdgeInfo,


Although we are currently only interested in a bool return value, we might still return the full chaninfo as a prevision for future use case, hmm I am not sure maybe we just simplify the function signature for now and only return a bool (also then maybe changing the name of the function)?

We could also repurpose some of the other endpoints exposed here already, like FetchChannelCapacity or FetchChannelEndpoints, which would return EdgeNotFound

bitromortac

Concept ACK, in principle, a single public hop hint doesn't lead to fee estimation errors, I think. The advantage in checking if we know the last hop is that we'll also probe it and know if it supports the payment as opposed to the case when we assume an LSP.

bitromortac · 2025-01-24T10:22:30Z

lnrpc/routerrpc/router_server.go

@@ -627,12 +628,13 @@ func (s *Server) probePaymentRequest(ctx context.Context, paymentRequest string,
 // isLSP checks if the route hints indicate an LSP. An LSP is indicated with
 // true if the last node in each route hint has the same node id, false
 // otherwise.
-func isLSP(routeHints [][]zpay32.HopHint) bool {
+func isLSP(routeHints [][]zpay32.HopHint, routerBackend *RouterBackend) bool {


I think passing in a function in instead is good enough, also makes it easier to mock in a unit test

bitromortac · 2025-01-24T10:24:01Z

lnrpc/routerrpc/router_backend.go

@@ -44,6 +45,11 @@ type RouterBackend struct {
 	// SelfNode is the vertex of the node sending the payment.
 	SelfNode route.Vertex

+	// FetchChannelInfo is a closure that we'll use the fetch the latest
+	// routing state for a particular channel identified by its channel ID.
+	FetchChannelInfo func(chanID uint64) (*models.ChannelEdgeInfo,


We could also repurpose some of the other endpoints exposed here already, like FetchChannelCapacity or FetchChannelEndpoints, which would return EdgeNotFound

bitromortac · 2025-01-24T10:35:11Z

lnrpc/routerrpc/router_server.go

 	if len(routeHints) == 0 || len(routeHints[0]) == 0 {
 		return false
 	}

-	refNodeID := routeHints[0][len(routeHints[0])-1].NodeID
+	refHint := routeHints[0][len(routeHints[0])-1]


could we rename the ref prefixes to something that's more explanatory?

lightninglabs-deploy · 2025-02-04T18:15:24Z

@hieblmi, remember to re-request review from reviewers when ready

hieblmi requested a review from ziggie1984 January 22, 2025 15:07

hieblmi self-assigned this Jan 22, 2025

hieblmi marked this pull request as draft January 22, 2025 15:07

hieblmi force-pushed the estimate-route-fee-fix branch from a0bc2cf to b3d97b5 Compare January 22, 2025 15:59

hieblmi added 2 commits January 22, 2025 17:23

routerrpc: fix estimateroutefee for public route hints

15dea83

docs: update release notes

eb1d56a

hieblmi force-pushed the estimate-route-fee-fix branch from b3d97b5 to eb1d56a Compare January 22, 2025 16:23

ziggie1984 added this to the v0.19.0 milestone Jan 22, 2025

ziggie1984 requested changes Jan 22, 2025

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ziggie1984 reviewed Jan 22, 2025

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saubyk requested a review from bitromortac January 23, 2025 15:48

bitromortac reviewed Jan 24, 2025

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hieblmi marked this pull request as ready for review February 4, 2025 17:12

saubyk requested a review from gijswijs February 4, 2025 17:48

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routerrpc: fix estimateroutefee for public route hints #9433

routerrpc: fix estimateroutefee for public route hints #9433

hieblmi commented Jan 22, 2025 •

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lightninglabs-deploy commented Feb 4, 2025

routerrpc: fix estimateroutefee for public route hints #9433

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hieblmi commented Jan 22, 2025 •

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