Hi all, but most especially non-c-lightning developers,
Some time ago, C-lightning imposed a minimum 253 sat/ksipa feerate:
https://github.com/ElementsProject/lightning/pull/1251
The reason is that the BOLT spec specifies a fee computation that is not
identical to how bitcoind computes fees.
Thus, the minimum 250 sat/ksipa feerate, if computed using the BOLT spec, will
result in a fee which bitcoind will compute as less than the minimum 250
sat/ksipa it imposes (due to difference in how BOLT and bitcoind compute
feerates).
Now C-lightning will not accept an onchain feerate (from `update_fee`) of less
than 253 sat/ksipa, precisely because of the above issue with the divergence in
how BOLT and bitcoind compute fees: anything less than 253 sat/ksipa, computed
using the BOLT spec, will be rejected by bitcoind. This results in a few
issues in C-lightning where we close unilaterally when the counterparty
proposes a 250sat/ksipa feerate:
* https://github.com/ElementsProject/lightning/issues/1351
* https://github.com/ElementsProject/lightning/issues/1529
(C-lightning has increased the ranges recently, but the 253sat/ksipa limit is a
hard limit and will still cause C-lightning to unilaterally close if the
counterparty gives an `update_fee` of <253)
Recently, Eclair discovered this same issue (i.e. bitcoind will not broadcast a
250 sat/ksipa feerate tx when computed using the BOLT spec algorithm):
https://github.com/ACINQ/eclair/issues/602
Eclair appears to have also imposed the same solution as C-lightning:
https://github.com/ACINQ/eclair/commit/8981d45dd52c52abe60d5c00411d638dd2124b6f
ucoin (nayutaco/ptarmigan) also has 253 in a constant somewhere:
https://github.com/nayutaco/ptarmigan/blob/6fe9db418ec962bf1d9282bb5271750b7c5764c2/ucoin/include/ln.h#L73
https://github.com/nayutaco/ptarmigan/blob/315e49785aa3fa19d1291b4d40bfc6951f988cda/ucoind/monitoring.c#L147
I am wondering whether lnd and lit have ever encountered issues with 250
sat/ksipa transactions getting propagated on the Bitcoin-level network. I
cannot find "253" in either codebase, suggesting that this minimum is not
imposed by lnd or lit.
Regards,
ZmnSCPxj
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