Add a maximum fee threshold for anchor outputs #1672
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With anchor outputs, the actual feerate for the commit tx can be decided when broadcasting the tx by using CPFP on the anchor. That means we don't need to constantly keep the channel feerate close to what's happening on-chain. We just need a feerate that's good enough to get the tx to propagate through the bitcoin network. We set the upper threshold to 10 sat/byte, which is what lnd does as well. We let the feerate be lower than that when possible, but do note that depending on your configured `feerate-tolerance`, that means you can still experience some force-close events because of feerate mismatch.
When using anchor outputs, the mutual close fee is allowed to be greater than the commit tx fee, because we're targeting a specific confirmation window.
We allow disagreeing on fees while the channel doesn't contain any htlc, because no funds can be at risk in that case. But we used the latest signed fee when adding a new HTLC, whereas we must also take into account the latest proposed (unsigned) fee.
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Codecov Report
@@ Coverage Diff @@
## master #1672 +/- ##
==========================================
+ Coverage 85.98% 86.04% +0.05%
==========================================
Files 151 151
Lines 11455 11504 +49
Branches 500 502 +2
==========================================
+ Hits 9850 9899 +49
Misses 1605 1605
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pm47
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Feb 18, 2021
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With anchor outputs, the actual feerate for the commit tx can be decided when broadcasting the tx by using CPFP on the anchor.
That means we don't need to constantly keep the channel feerate close to what's happening on-chain. We just need a feerate that's good enough to get the tx to propagate through the bitcoin network.
We set the upper threshold to 10 sat/byte, which is what lnd does as well. We let the feerate be lower than that when possible, but do note that depending on your configured
feerate-tolerance, that means you can still experience some force-close events because of feerate mismatch.The last two commits fix small related issues and can be reviewed independently.
NB: anchor outputs is still not safe to use after this commit: we don't bump the feerate yet by doing a CPFP on the anchor. This will come in a later PR.