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.

lnrpc/routerrpc/router_backend.go

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

done. I declared a new type FetchChannelInfo in the router_server.go which matches the function signature in router_backend.go.

lnrpc/routerrpc/router_server.go

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.

lnrpc/routerrpc/router_server_test.go

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

To keep the footprint of this PR small I agree to repurpose FetchChannelEndpoints to check if we deal with a public route hint. I've removed the field FetchChannelInfo from the router backend.

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?

still ref used ?

renamed it to destHopHint and also referenced that in the comments.

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

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

ziggie1984

Nice, LGTM.

Please update the documentation otherwise good-to-go

ziggie1984 · 2025-02-07T19:32:25Z

docs/release-notes/release-notes-0.19.0.md

+
+* [Fixed a bug](https://github.com/lightningnetwork/lnd/pull/9433) that caused 
+  `estimateroutefee` to assume probing an LSP when given a route hint containing 
+  a public channel.


... when given an invoice with a route hint containing a public channel to the destination.

thanks, fixed it.

ziggie1984 · 2025-02-07T19:40:04Z

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]


still ref used ?

ziggie1984 · 2025-02-07T19:42:32Z

lnrpc/routerrpc/router_server_test.go

@@ -284,6 +294,7 @@ func TestIsLsp(t *testing.T) {
 		isLsp          bool
 		expectedHints  [][]zpay32.HopHint
 		expectedLspHop *zpay32.HopHint
+		channelID      int64


why not uint64 ?

ziggie1984 · 2025-02-07T20:07:45Z

lnrpc/routerrpc/router_server.go

@@ -627,12 +632,23 @@ 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


comment needs an update because we also check for public channels now.

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 2 times, most recently 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

hieblmi force-pushed the estimate-route-fee-fix branch 2 times, most recently from 7be7d83 to ec2132b Compare February 7, 2025 11:33

hieblmi requested review from bitromortac and ziggie1984 February 7, 2025 12:30

ziggie1984 approved these changes Feb 7, 2025

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hieblmi added 2 commits February 8, 2025 17:50

routerrpc: fix estimateroutefee for public route hints

4aebf45

docs: update release notes

8c8e852

hieblmi force-pushed the estimate-route-fee-fix branch from ec2132b to 8c8e852 Compare February 8, 2025 16:52

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routerrpc: fix estimateroutefee for public route hints #9433

routerrpc: fix estimateroutefee for public route hints #9433

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		@@ -627,12 +632,23 @@ 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

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