[bug]: scammed using a hold invoice

[anycolo]

1. I tried paying a ln invoice using my lnd instance. I submitted the payment a few days ago, but the status i received wasn't "complete".
2. I waited a few hours, i tried paying again, i got 'no route' or 'payment in transit' (not sure)
3. I waited a few more hours, i tried paying again, it didn't say 'invoice is already paid'.
4. I waited a few moure hours, i tried paying the invoice again, it said that it was EXPIRED, so i assumed that the payment failed.

I refunded the customer using another channel and .. behold, the invoice managed to complete itself after some time, so i paid him twice.

I have a lot of questions:

• was it possible, that between 3 and 4 the payment completed and when trying to pay it again, lnd woulnd't respond with 'invoice is already paid' but with 'invoice expired'?
• i am 99% sure that this was a hold invoice. is it possible to force lnd to pay an invoice in X amount of time or cancel it, with me being able to retry it later and get a clear status of what is going on?
• can an invoice be settled AFTER the expiration date, using these stuck HTLC's? If so, why? It seems like a very bad idea.
• how can lnd cancel a transaction that is in flight? how can i cancel a hodl invoice?
• how can i set the max amount of time a HTLC can get stuck by the other side?

[alexbosworth]

payment in transit means that the payment is being sent, but it shouldn't be possible that you can pay the same payment request twice in lnd, probably need more logs or more details to know exactly what happened

[anycolo]

I didn't pay the same invoice twice, i refunded via classic bitcoin transaction.

[alexbosworth]

ok, just to note, yes an invoice that is past the "expiry" date marked on the payment request can still be settled after this date. The date is advisory and not binding

[anycolo]

Is this behavior a bug in lightning, in general?

[anycolo]

I have a payment request "lnbcxxxx..." from yesterday. My lnd wallet attempted to pay it a few times. What command can i run to see:

• if it was attempted
• what was the result of that attempt(s)
• if the status isn't clear, how can i stop any future attempts
• if there are any stuck htlcs for that payment (part of an hodl invoice)

[alexbosworth]

you can use trackpayment

[anycolo]

Trackpayment requires a hash, so i have decoded the payment request with decodepayreq, then i ran trackpayment succesfully:

+------------+--------------+--------------+--------------+-----+----------+----------+-------+
| HTLC_STATE | ATTEMPT_TIME | RESOLVE_TIME | RECEIVER_AMT | FEE | TIMELOCK | CHAN_OUT | ROUTE |
+------------+--------------+--------------+--------------+-----+----------+----------+-------+
+------------+--------------+--------------+--------------+-----+----------+----------+-------+
Amount + fee:   0 + 0 sat
Payment hash:   xxx
Payment status: FAILED, reason: FAILURE_REASON_NO_ROUTE

Does this mean 100% sure that the payment will not be completed at a later time?

[alexbosworth]

yes

[anycolo]

Okay, assume this case again:

• attempt to pay an invoice
• payment is held hostage by HODL invoice
• invoice expires
• attempt to pay the invoice again to see it's status

What should lnd respond when i try to do this:

• A: payment is in transit
• B: invoice has expired
• C: something else?

[alexbosworth]

if the htlc is still locked then it should respond that the payment is in transit yes, it shouldn't let you double pay it

[anycolo]

Okay, but any way to cancel a 'payment in transit' invoice? Or do i have to wait for the HTLC to resolve?

[alexbosworth]

Right there is a timeout associated with HTLCs that are in flight, wait for that timeout to expire

[anycolo]

I notice that sometimes, i can submit a payment attempt to my LND node, and it will timeout with some error after a few minutes of trying. When i try to make the same payment in a few minutes, i'll get an 'invoice is already paid'. How can i instruct lnd to cancel a submitted payment attempt or how can i instruct LND to try paying it for only a finite amount of time and then abort forever. It seems that once you submit an invoice to pay to lnd, it goes into a grey zone where you can never be sure about it's status.

[alexbosworth]

you couldn't cancel a payment with already committed HTLCs, but you can specify a pathfinding timeout to payment

You also cannot cancel pathfinding within that timeout frame though

The status can be found via trackpayment api