payment lifecycle small fix #9626

ziggie1984 · 2025-03-21T04:04:40Z

While working on the payment lifecycle I came across this case. When trying to send a keysend with a max shard restriction we would not fail the payment properly and it would hang indefinitely being marked as INFLIGHT in the db although no payment was attempted.

Just try sending a payment via this cmd:

lncli sendpayment --dest XXX --amt 100 --keysend --max_shard_size_sat 10

The payment lifecycle will fail here because keysend payments are not MPP payments but we try to shard them:

lnd/channeldb/payment_control.go

Lines 419 to 422 in 5d92172

    
           amt := attempt.Route.ReceiverAmt() 
        
           if !isBlinded && mpp == nil && amt != payment.Info.Value { 
        
           	return ErrValueMismatch 
        
           }

coderabbitai · 2025-03-21T04:09:16Z

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yyforyongyu

I think we need an itest to show what's been fixed. In addition I think we should catch this error earlier in the rpc layer.

yyforyongyu · 2025-03-21T05:27:51Z

routing/payment_lifecycle.go

+		// because otherwise the payment might be resolved when
+		// resuming.
+		_, failure := payment.TerminalInfo()
+		if failure == nil &&


I don't think we should make it this complicated - if we really want to fail the payment, I think the only safe case to fail is when the status is in StatusInitiated, which is the case from using keysend + max_shard_size_sat, the payment was never attempted.

yyforyongyu · 2025-03-21T05:28:27Z

routing/payment_lifecycle.go

+	exitWithErr := func(exitErr error) ([32]byte, *route.Route, error) {
+		// We fetch the latest payment status here to get the latest
+		// state of the payment.
+		payment, err := p.router.cfg.Control.FetchPayment(p.identifier)


we don't need to fetch the payment again - it's already been rewritten in the loop below.

hmm, acutally I think we need because we reload it at the beginning and then we might fail it down the road so we will not have the current payment status available.

As long as we check for StatusInitiated we can be sure it's not modified, which can only happen when the async result collector is fired, which implicitly means there are inflight HTLCs, and we don't want to fail it in that case.

yyforyongyu · 2025-03-21T05:28:44Z

routing/payment_lifecycle.go

-	exitWithErr := func(err error) ([32]byte, *route.Route, error) {
-		// Log an error with the latest payment status.
-		//
-		// NOTE: this `status` variable is reassigned in the loop


Keep this note?

yyforyongyu · 2025-03-21T05:30:22Z

routing/payment_lifecycle.go

@@ -332,6 +350,13 @@ lifecycle:
 		return htlc.Settle.Preimage, &htlc.Route, nil
 	}

+	// At this point the payment should have a failure reason and therefore
+	// this should never happen.
+	if failure == nil {


Have you encountered this case before?

No I haven't it just caught my eye so I added this robustness check.

yeah i had that concern too - tho I think it's not possible to have this being nil. A better way is to Defining errors out of existence so we don't need to even worry about it, maybe a new PR to change the pointer to be a concrete struct.

itest/lnd_payment_test.go

yyforyongyu · 2025-03-25T05:20:01Z

routing/payment_lifecycle.go

-		// the payment fetching to return an error.
-		log.Errorf("Payment %v with status=%v failed: %v", p.identifier,
-			status, err)
+	exitWithErr := func(exitErr error) ([32]byte, *route.Route, error) {


if we really wanna do this let's make these into a new method so we don't grow the resumePayment

bhandras

LGTM 🚀

record/custom_records.go

yyforyongyu

Looking good

record/custom_records.go

ziggie1984 requested review from yyforyongyu and bhandras March 21, 2025 04:07

ziggie1984 force-pushed the payment-lifecycle-small-fix branch from 603ecfb to 208e181 Compare March 21, 2025 04:08

ziggie1984 marked this pull request as ready for review March 21, 2025 04:08

ziggie1984 force-pushed the payment-lifecycle-small-fix branch from 208e181 to a5a3772 Compare March 21, 2025 04:51

yyforyongyu requested changes Mar 21, 2025

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ziggie1984 force-pushed the payment-lifecycle-small-fix branch from a5a3772 to fc67963 Compare March 25, 2025 04:54

yyforyongyu reviewed Mar 25, 2025

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itest/lnd_payment_test.go Show resolved Hide resolved

yyforyongyu reviewed Mar 25, 2025

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ziggie1984 force-pushed the payment-lifecycle-small-fix branch from fc67963 to 0356f0e Compare March 25, 2025 06:25

ziggie1984 added 2 commits March 25, 2025 04:42

multi: make validation for keysend stricter

013e408

docs: add release-notes

0eca55f

ziggie1984 force-pushed the payment-lifecycle-small-fix branch from 0356f0e to 0eca55f Compare March 25, 2025 09:42

ziggie1984 requested a review from yyforyongyu March 25, 2025 09:42

ziggie1984 added this to lnd v0.19 Mar 25, 2025

ziggie1984 added this to the v0.19 overflow milestone Mar 25, 2025

bhandras approved these changes Mar 25, 2025

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record/custom_records.go Show resolved Hide resolved

yyforyongyu approved these changes Mar 25, 2025

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guggero merged commit cf35be8 into lightningnetwork:master Mar 25, 2025
31 of 35 checks passed

github-project-automation bot moved this to Done in lnd v0.19 Mar 25, 2025

ziggie1984 mentioned this pull request Mar 25, 2025

Add unit test to record pkg #9644

Merged

saubyk modified the milestones: v0.19 overflow, v0.19.0 May 15, 2025

	amt := attempt.Route.ReceiverAmt()
	if !isBlinded && mpp == nil && amt != payment.Info.Value {
	return ErrValueMismatch
	}

payment lifecycle small fix #9626

payment lifecycle small fix #9626

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ziggie1984 commented Mar 21, 2025 •

edited

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coderabbitai bot commented Mar 21, 2025 •

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