From ZmnSCPxj at protonmail.com Tue May 29 06:15:55 2018 From: ZmnSCPxj at protonmail.com (ZmnSCPxj) Date: Tue, 29 May 2018 02:15:55 -0400 Subject: [Lightning-dev] Imposing minimum 253 sat/ksipa feerate? Message-ID: 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 -------------- next part -------------- An HTML attachment was scrubbed... URL: