Patch htlc attempt hash for legacy payments #9703

yyforyongyu · 2025-04-11T07:40:52Z

Fix #9688 by making sure we always set the Hash field on legacy payments.

coderabbitai · 2025-04-11T07:40:58Z

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Copilot

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

routing/payment_lifecycle.go

ziggie1984

Thank you for the investigation,

LGTM - pending lint issue.

ziggie1984 · 2025-04-11T09:17:29Z

routing/payment_lifecycle.go

+
+	// Log a warning if the user is still using legacy payments, which has
+	// weaker support.
+	log.Warnf("Found legacy htlc attempt %v in payment %v", a.AttemptID,


Can legacy payments still be created with the latest LND release, or are these payments which are stuck inlight because of previous behaviour and we are just relaunching it every time ?

yeah - it's another question that I will ask Kevin once he could restart his testnet node once this PR is merged. Weird we still have stuck payments.

Can legacy payments still be created with the latest LND release

No they can't, as stated in the commit msg,

For legacy payments, the hash field will be nil, and we need to use the payment identifier instead. We have multiple ways to fix this: A trivial solution is we can simply call `sharder.GetHash` in `collectResult`, and pass this hash to `attempt.Circuit()`, which ends up multiple methods taking the hash. This is bad as it's confusing why the methods of `HTLCAttempt` need to take another hash value, while itself already has the info via `HTLCAttempt.Hash`. We don't want an exceptional case to influence our main flow. We can then patch the field `HTLCAttempt.Hash`, and set it to the payment hash if it's nil, which can be done in `collectResult`. This is also less optimal as it means every htlc attempts, either legacy or not, now need to bear this context. The best way to do this is to patch the field in `reloadInflightAttempts`. As we are sure any new payments made won't be legacy, and the only source of legacy payments comes from reloading existing payments.

ziggie1984 · 2025-04-11T09:19:25Z

routing/payment_lifecycle.go

+	// before MPP feature, the `Hash` field was not set so we use the
+	// payment hash instead.
+	//
+	// NOTE: During the router's startup, we have a similar logic in


Instead of this comment could we use this function there as well ?

or maybe we could patch in the db layer in fetchPayment?

Instead of this comment could we use this function there as well ?

You mean the GetHash? Yeah we could use that, tho I think it's more clear this way. Plus it'd be better if we don't use shard tracker for non-AMP payments to make the flow clean for MPP.

or maybe we could patch in the db layer in fetchPayment?

Yeah it'd be nice if we did that initially. As for now it seems unnecessary as we won't create legacy payments, and those legacy payments should not be inflight anymore as they should have timed out years ago. Think it's weird we have this stuck payments still, will ask Kevin for more logs once he could start his testnet node.

ziggie1984 · 2025-04-11T09:22:03Z

routing/payment_lifecycle_test.go

+
+	var r *switchResult
+
+	// Assert the result is returned within 5 seconds.


instead of hard coded 5 seconds, just leave it out because the testTimeout is a variable ?

routing/payment_lifecycle.go

bitromortac · 2025-04-11T12:08:33Z

routing/payment_lifecycle.go

+	// before MPP feature, the `Hash` field was not set so we use the
+	// payment hash instead.
+	//
+	// NOTE: During the router's startup, we have a similar logic in


or maybe we could patch in the db layer in fetchPayment?

For legacy payments, the hash field will be nil, and we need to use the payment identifier instead. We have multiple ways to fix this: A trivial solution is we can simply call `sharder.GetHash` in `collectResult`, and pass this hash to `attempt.Circuit()`, which ends up multiple methods taking the hash. This is bad as it's confusing why the methods of `HTLCAttempt` need to take another hash value, while itself already has the info via `HTLCAttempt.Hash`. We don't want an exceptional case to influence our main flow. We can then patch the field `HTLCAttempt.Hash`, and set it to the payment hash if it's nil, which can be done in `collectResult`. This is also less optimal as it means every htlc attempts, either legacy or not, now need to bear this context. The best way to do this is to patch the field in `reloadInflightAttempts`. As we are sure any new payments made won't be legacy, and the only source of legacy payments comes from reloading existing payments.

bitromortac

LGTM 🎉 thank you!

yyforyongyu · 2025-04-14T13:12:20Z

@bitromortac and I discussed offline, thinking we could use the SQL payment as an opportunity to permanently patch this nil Hash, cc @ziggie1984

yyforyongyu added the payments Related to invoices/payments label Apr 11, 2025

yyforyongyu added this to the v0.19.0 milestone Apr 11, 2025

yyforyongyu requested review from bitromortac, ziggie1984 and Copilot April 11, 2025 07:40

yyforyongyu self-assigned this Apr 11, 2025

Copilot AI reviewed Apr 11, 2025

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routing/payment_lifecycle.go Show resolved Hide resolved

ziggie1984 approved these changes Apr 11, 2025

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bitromortac reviewed Apr 11, 2025

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yyforyongyu added 3 commits April 11, 2025 21:52

routing: add regression test to catch the panic

8689eee

docs: update release notes

79ab2b2

yyforyongyu force-pushed the fix-attempt-hash branch from b2bf87b to 79ab2b2 Compare April 11, 2025 13:52

bitromortac approved these changes Apr 14, 2025

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yyforyongyu merged commit 4cf18ee into lightningnetwork:master Apr 14, 2025
34 of 36 checks passed

yyforyongyu deleted the fix-attempt-hash branch April 14, 2025 13:12

ziggie1984 mentioned this pull request Apr 14, 2025

[Part 1|3] Introduce SQL Payment schema into LND #9147

Draft


		var r *switchResult

		// Assert the result is returned within 5 seconds.

Patch htlc attempt hash for legacy payments #9703

Patch htlc attempt hash for legacy payments #9703

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yyforyongyu commented Apr 11, 2025

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yyforyongyu commented Apr 14, 2025

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