From: Matt Corallo Date: Thu, 9 Sep 2021 01:09:41 +0000 (+0000) Subject: Reduce our stated max closing-transaction fee to be the true value X-Git-Tag: v0.0.101~21^2 X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=commitdiff_plain;h=refs%2Fheads%2F2021-09-tighter-max_fee-constant;p=rust-lightning Reduce our stated max closing-transaction fee to be the true value When communicating the maximum fee we're willing to accept on a cooperative closing transaction to our peer, we currently tell them we'll accept `u64::max_value()` if they're the ones who have to pay it. Spec-wise this is fine - they aren't allowed to try to claim our balance, and we don't care how much of their own funds they want to spend on transaction fees. However, the Eclair folks prefer to check all values on the wire do not exceed 21 million BTC, which seems like generally good practice to avoid overflows and such issues. Thus, our close messages are rejected by Eclair. Here we simply relax our stated maximum to be the real value - our counterparty's current balance in satoshis. Fixes #1071 --- diff --git a/lightning/src/ln/channel.rs b/lightning/src/ln/channel.rs index 0481a93fc..767cf130d 100644 --- a/lightning/src/ln/channel.rs +++ b/lightning/src/ln/channel.rs @@ -459,8 +459,8 @@ pub(super) struct Channel { /// closing_signed message and handling it in `maybe_propose_closing_signed`. pending_counterparty_closing_signed: Option, - /// The minimum and maximum absolute fee we are willing to place on the closing transaction. - /// These are set once we reach `closing_negotiation_ready`. + /// The minimum and maximum absolute fee, in satoshis, we are willing to place on the closing + /// transaction. These are set once we reach `closing_negotiation_ready`. #[cfg(test)] pub(crate) closing_fee_limits: Option<(u64, u64)>, #[cfg(not(test))] @@ -3444,7 +3444,7 @@ impl Channel { cmp::max(normal_feerate as u64 * tx_weight / 1000 + self.config.force_close_avoidance_max_fee_satoshis, proposed_max_feerate as u64 * tx_weight / 1000) } else { - u64::max_value() + self.channel_value_satoshis - (self.value_to_self_msat + 999) / 1000 }; self.closing_fee_limits = Some((proposed_total_fee_satoshis, proposed_max_total_fee_satoshis)); @@ -3732,7 +3732,8 @@ impl Channel { if !self.is_outbound() { // They have to pay, so pick the highest fee in the overlapping range. - debug_assert_eq!(our_max_fee, u64::max_value()); // We should never set an upper bound + // We should never set an upper bound aside from their full balance + debug_assert_eq!(our_max_fee, self.channel_value_satoshis - (self.value_to_self_msat + 999) / 1000); propose_fee!(cmp::min(max_fee_satoshis, our_max_fee)); } else { if msg.fee_satoshis < our_min_fee || msg.fee_satoshis > our_max_fee {