Benjamin Weintraub [ARCHIVE] on Nostr: 📅 Original date posted:2022-12-13 📝 Original message: Hi list, I have a ...

📅 Original date posted:2022-12-13
📝 Original message:
Hi list,


I have a question about how update_fail_htlcs are handled. Consider this scenario: a node, potentially adversarial, forwards an HTLC along a channel that does not have the funds to support a payment of that size. How does the recipient of the HTLC respond?


I see this line in BOLT #2:

“until the corresponding HTLC is irrevocably committed in both sides' commitment transactions: MUST NOT send an update_fulfill_htlc, update_fail_htlc, or update_fail_malformed_htlc"


But this seems confusing to me in the context of the scenario I suggested. Is it saying that even though the channel cannot support the payment, the nodes still need to commit to it?


I assume that this interpretation is not correct, but then when is it okay for a node to send an update_fail_htlc? Immediately upon receiving an invalid transaction?


Any insight you could provide would be great.


Thanks in advance,

Ben

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