Withheld channel close: fail back inflight HTLCs and free UTXOs#8943
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Withheld channel close: fail back inflight HTLCs and free UTXOs#8943nepet wants to merge 3 commits intoElementsProject:masterfrom
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When a withheld channel is force-closed (e.g. due to CLTV timeout), in-flight HTLCs were being freed without failing them back to the upstream sender. This caused the upstream peer to eventually force-close its own channel waiting for a resolution that would never come. Iterate over all offered HTLCs on the withheld channel in drop_to_chain() and fail them back upstream with permanent_channel_failure before freeing them. Changelog-fixed: withheld channel now fail back incoming inflight htlc
…channel When a channel using a withheld funding PSBT is dropped, we need to unreserve the UTXOs from the PSBT. Otherwise those funds will remain blocked until the reservation expires, delaying their availability for other transactions. Changelog-Fixed: lightningd: unreserve UTXOs from withheld funding PSBT on channel close.
Adds the preimage to the forward_event notification when status is settled. This can be useful to gather some context when listening to this event Changelog-Changed: forward_event notification no has preimage set if status is settled. Signed-off-by: Peter Neuroth <pet.v.ne@gmail.com>
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Important
26.04 FREEZE March 11th: Non-bugfix PRs not ready by this date will wait for 26.06.
RC1 is scheduled on March 23rd
The final release is scheduled for April 15th.
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Before submitting the PR, ensure the following tasks are completed. If an item is not applicable to your PR, please mark it as checked:
tools/lightning-downgradeThis PR improves the handling of withheld channel closes:
First, when a withheld zero-conf channel gets dropped, for example because an in-flight HTLC on a channel hits its CLTV deadline, we only freed any HTLCs on that channel withouth failing them back upstream. The upstream peer would then sit there waiting for a resolution that was never going to come, and eventually force-close its channel too. This patch iterates over offered HTLCs on the withheld channel during drop_to_chain() and fails them back with permanent_channel_failure before freeing them.
Second, the UTXOs used in the withheld funding PSBT were left reserved after the channel was torn down. They'd eventually become available again once the reservation expired, but in the meantime the wallet would behave as if those funds didn't exist. Now we explicitly unreserve them when dropping the channel.
This also slips in a convenient small addition to
forward_event: also return the preimage if status issettled