Use all valid routes during blinded path construction #9334

MPins · 2024-12-05T14:57:33Z

MaxNumPaths restriction moved from FindBlindedPaths to BuildBlindedPaymentPaths this way we can interact through all possibly routes.

If the reviewers agreed to this approach we will have to modify the TestFindBlindedPathsWithMC because it is considering that MaxNumPaths retriction is applied on FindBlindedPaths function.

coderabbitai · 2024-12-05T14:57:43Z

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ziggie1984 · 2024-12-07T00:34:31Z

This seems like the simpler solution to implement. Since we’re already querying all routes in FindBlindedPaths, it makes sense to just return them. However, it might be worthwhile to introduce a hard constant cap during the pathfinding process to prevent the array size from growing exponentially. Currently, the algorithm explores all possible paths within the given constraints. Instead, we could stop after finding, say, 100 routes in total, and then apply filtering to select the MaxNumPaths in BuildBlindedPaymentPaths, as proposed in this PR.

Probably the constraints of the Min/Max Hop number prevents these high numbers for routes but I think having a cap is kind of a sanity check.

MPins · 2024-12-09T11:52:30Z

This seems like the simpler solution to implement. Since we’re already querying all routes in FindBlindedPaths, it makes sense to just return them. However, it might be worthwhile to introduce a hard constant cap during the pathfinding process to prevent the array size from growing exponentially. Currently, the algorithm explores all possible paths within the given constraints. Instead, we could stop after finding, say, 100 routes in total, and then apply filtering to select the MaxNumPaths in BuildBlindedPaymentPaths, as proposed in this PR.

Probably the constraints of the Min/Max Hop number prevents these high numbers for routes but I think having a cap is kind of a sanity check.

Before the proposed changes we are querying all routes, sorting the routes based on probability and them capping them based on MaxNumPaths before returning from FindBlindedPaths. After the changes we are capping them just one step later after FindBlindedPaths return them to BuildBlindedPaymentPaths. The hard constant cap should be introduced after the sorting! I might be wrong, but it seems that we are getting too little introducing it!

ziggie1984 · 2024-12-09T12:46:26Z

The hard constant cap should be introduced after the sorting! I might be wrong, but it seems that we are getting too little introducing it!

I think we need to do way more when creating the path rather than creating the path and later checking the probability this does not seem efficient. I think we should build the path in the first place based on probability not just running a depth first search on all available paths. But I am not sure how difficult that might be because we went with the recusrive approach.

MPins · 2024-12-10T13:42:54Z

The hard constant cap should be introduced after the sorting! I might be wrong, but it seems that we are getting too little introducing it!

I think we need to do way more when creating the path rather than creating the path and later checking the probability this does not seem efficient. I think we should build the path in the first place based on probability not just running a depth first search on all available paths. But I am not sure how difficult that might be because we went with the recursive approach.

I think we might compute the total probability and sort the path list during the creation of it (into processNodeForBlindedPath), but I'm not sure it's worth it. What do you think?

ziggie1984 · 2024-12-12T10:09:14Z

yes let's keep it as is and focus only on the underlying issue.

routing/router.go

MPins · 2024-12-19T13:30:08Z

Hello @ziggie1984 gently reminder of review 😉

ziggie1984 · 2024-12-29T08:29:22Z

unit-test fail !

ziggie1984

Looking good I am missing 2 things here:

Can you add some logging stats how many routes are find in total, then how many are filtered out because of the probability as for example debug information. I am very curious whether routes will fail often at the level where the final route and relay information is accumulated.
I tend to introduce a max route variable for the blinded path finding in general, maybe a default of 50 routes, otherwise we look for everything which with a big number of blinded hops might be wasteful.

routing/blindedpath/blinded_path.go

ziggie1984 · 2024-12-29T08:49:15Z

routing/router_test.go

-		},
-	)
-	require.NoError(t, err)
-	assertPaths(routes, []string{


can we still check here the expected number of paths now

Yes, we could, but it would be redundant since this is already tested in the previous tests.

which one do you mean ?

My understanding is that this test was meant to verify the numpaths restriction. Without it, no additional cases are being tested beyond those already covered in the previous tests.

rpcserver.go

lightninglabs-deploy · 2025-01-15T20:03:24Z

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

MPins · 2025-01-24T01:50:05Z

Looking good I am missing 2 things here:

Can you add some logging stats how many routes are find in total, then how many are filtered out because of the probability as for example debug information. I am very curious whether routes will fail often at the level where the final route and relay information is accumulated.

I tend to introduce a max route variable for the blinded path finding in general, maybe a default of 50 routes, otherwise we look for everything which with a big number of blinded hops might be wasteful.

Hello Ziggie, I had addressed your comments, thank you! Ready for your next review!

Abdulkbk

Thanks for the PR. I looked through the changes and left some comments/questions.

routing/router.go

routing/blindedpath/blinded_path_test.go

MPins

Thank you @Abdulkbk for your review!

routing/router.go

MPins · 2025-01-31T21:04:54Z

@ziggie1984 and @Abdulkbk , it is ready for your review. 🤝

ziggie1984

Looking good, I want to get @ellemouton opinion on the recursive abort criteria in case we have a maximum number of paths.

Missing release notes for LND 20.

routing/blindedpath/blinded_path.go

ziggie1984 · 2025-02-01T17:32:27Z

routing/router.go

 	for _, route := range routes {
-		if len(bestRoutes) >= int(restrictions.MaxNumPaths) {
+		if len(allRoutes) >= maxRoutes {


that is not what I meant, my idea was to exit the recursion early when enough paths are found,

I was more thinking of restricting the recursion in processNodeForBlindedPath but I would like to get @ellemouton opinion on this and also this can probably done in another PR.

Currently our DFS exhausts all Paths which exist in the graph, so I was thinking we could abort the DFS after we already have a hopSet of let's say 100 ?

Imagine we have a minRouteLen of 2 and a maxRouteLen of 6, each node has more than 100 channels, when reaching the depth of 6, we could easily accumulate > 1000 routes which seems unreasonable.

But the above restrictions we do not need, because really makes not difference we already have all the paths in memory.

You right, thanks for the explanation.

The point is that, in the current implementation, we first retrieve all the routes and then sort them to prioritize those with the highest success probability.

Instead, we should modify the process to evaluate the probability of each route during the iteration, keeping only the best ones.

ziggie1984 · 2025-02-01T17:35:52Z

routing/router_test.go

-		},
-	)
-	require.NoError(t, err)
-	assertPaths(routes, []string{


which one do you mean ?

routing/blindedpath/blinded_path_test.go

MPins

@ziggie1984 thank for your review! Comments addressed.

MPins · 2025-02-02T13:25:08Z

routing/router.go

 	for _, route := range routes {
-		if len(bestRoutes) >= int(restrictions.MaxNumPaths) {
+		if len(allRoutes) >= maxRoutes {


You right, thanks for the explanation.

The point is that, in the current implementation, we first retrieve all the routes and then sort them to prioritize those with the highest success probability.

Instead, we should modify the process to evaluate the probability of each route during the iteration, keeping only the best ones.

MPins · 2025-02-02T14:12:05Z

routing/router_test.go

-		},
-	)
-	require.NoError(t, err)
-	assertPaths(routes, []string{


My understanding is that this test was meant to verify the numpaths restriction. Without it, no additional cases are being tested beyond those already covered in the previous tests.

MaxNumPaths restriction moved from FindBlindedPaths to BuildBlindedPaymentPaths this way we can interact through all possibly routes when creating a new blinded path.

… use MaxNumPaths MaxNumPaths restriction moved from FindBlindedPaths to BuildBlindedPaymentPaths this way we have to fill the MaxNumPaths parameter when calling this function.

MPins · 2025-02-03T01:14:21Z

Looking good, I want to get @ellemouton opinion on the recursive abort criteria in case we have a maximum number of paths.

Missing release notes for LND 20.

There is no release notes for LND 20 yet. Should I create it?

MPins changed the title ~~route blinding: use all valid routes during path construction iteration instead of the currently capped set by MaxNumPaths~~ Use all valid routes during path construction iteration instead of the currently capped set by MaxNumPaths Dec 5, 2024

MPins changed the title ~~Use all valid routes during path construction iteration instead of the currently capped set by MaxNumPaths~~ use all valid routes during blinded path construction Dec 5, 2024

MPins changed the title ~~use all valid routes during blinded path construction~~ Use all valid routes during blinded path construction Dec 5, 2024

MPins force-pushed the issue-9076 branch from f21292d to bbab1a7 Compare December 5, 2024 15:11

ziggie1984 self-requested a review December 5, 2024 18:06

MPins force-pushed the issue-9076 branch from bbab1a7 to 12819a2 Compare December 6, 2024 10:50

ziggie1984 reviewed Dec 12, 2024

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MPins force-pushed the issue-9076 branch from 12819a2 to cfa17cb Compare December 13, 2024 09:50

MPins requested a review from ziggie1984 December 13, 2024 10:31

saubyk assigned MPins Dec 19, 2024

ziggie1984 reviewed Dec 29, 2024

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MPins force-pushed the issue-9076 branch 2 times, most recently from 41573d0 to c1251d7 Compare January 20, 2025 23:28

MPins requested a review from ziggie1984 January 20, 2025 23:44

MPins force-pushed the issue-9076 branch from c1251d7 to 100f8de Compare January 21, 2025 11:08

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MPins force-pushed the issue-9076 branch from 100f8de to 965b431 Compare January 31, 2025 19:55

MPins requested a review from Abdulkbk January 31, 2025 20:30

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MPins commented Feb 2, 2025

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MPins added 2 commits February 2, 2025 20:22

blindedpath: add the MaxNumPaths restriction on BuildBlindedPaymentPaths

f0b2e70

invoicesrpc: included MaxNumPaths to be used on BuildBlindedPaymentPaths

7ed3a80

MPins force-pushed the issue-9076 branch from 965b431 to f9f4d7d Compare February 2, 2025 23:27

MPins added 4 commits February 2, 2025 21:58

routing: no MaxNumPaths restriction on FindBlindedPaths

dc402b8

routing: modify the TestFindBlindedPathsWithMC to not use MaxNumPaths

d4339ae

MaxNumPaths restriction moved from FindBlindedPaths to BuildBlindedPaymentPaths this way we can interact through all possibly routes when creating a new blinded path.

lnd: added MaxNumPaths on blindedPathCfg to be used on AddInvoice

9b10d31

blindedpath: modify all the tests calling BuildBlindedPaymentPaths to…

1c0ddb2

… use MaxNumPaths MaxNumPaths restriction moved from FindBlindedPaths to BuildBlindedPaymentPaths this way we have to fill the MaxNumPaths parameter when calling this function.

MPins force-pushed the issue-9076 branch from f9f4d7d to 1c0ddb2 Compare February 3, 2025 00:58

MPins requested a review from ziggie1984 February 4, 2025 13:37

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Use all valid routes during blinded path construction #9334

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Use all valid routes during blinded path construction #9334

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