Avoid stuck channels after fee increase by dipping into reserve #750
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t-bast
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Allow funders to dip into their channel reserve once to be able to pay the increased commit tx fee for a pending HTLC. This prevents channels from getting in a state where the channel is unusable because of the increased commit tx cost of a new HTLC. Fixes #728.
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joostjager
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Feb 25, 2020
| @@ -863,6 +869,10 @@ seconds, and the protocol only supports an expiry in blocks. | |||
| specification; larger amounts are not necessary, nor wise, during the | |||
| bootstrap phase of the network. | |||
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| The node _responsible_ for paying the Bitcoin fee should be allowed to dip into | |||
| its channel reserve to accommodate a fee increase, otherwise the channel may end | |||
| up in an unusable state (see [#728](https://github.com/lightningnetwork/lightning-rfc/issues/728)). | |||
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How do nodes signal that they allow this? Older nodes wouldn't allow this.
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I don't think you need to signal anything.
First case: sender is upgraded, receiver is not. The sender will send an HTLC that the receiver will reject (a non-upgraded sender wouldn't have sent that HTLC - the channel would be stuck). No big deal.
Second case: receiver is upgraded, sender is not. The sender will not send any HTLC, so the channel will be stuck. It's still possible to restore the channel by using below dust HTLCs until it's unblocked.
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Closing in favor of #740 as agreed during yesterday's IRC meeting. |
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Allow funders to dip into their channel reserve once to be able to pay the increased commit tx fee for a pending HTLC.
This prevents channels from getting in a state where the channel is unusable because of the increased commit tx cost of a new HTLC.
Fixes #728. (see the issue for a longer discussion)
This is an alternative to #740. I think it makes sense to dip into the reserve in that case.
Do note that this only fixes the stuck channel issue if the channel reserve is big enough for the fee increase.
At ~3500 sat/kw with a 1% reserve, it means that channels with a capacity bigger than 60 000 sats are safe from getting stuck, but smaller channels may still get stuck.