Reduce force-closures with user fee estimators which round poorly

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diff --git a/lightning/src/ln/channel.rs b/lightning/src/ln/channel.rs
index ae5df9a1507c78058d4d94d5ed06e79ef272668d..0ab687521c3aa5fcff317b1c53ee65e58022dcda 100644 (file)
--- a/lightning/src/ln/channel.rs
+++ b/lightning/src/ln/channel.rs
@@ -862,8 +862,12 @@ impl<Signer: Sign> Channel<Signer> {
                where F::Target: FeeEstimator
        {
                let lower_limit = fee_estimator.get_est_sat_per_1000_weight(ConfirmationTarget::Background);
-               if feerate_per_kw < lower_limit {
-                       return Err(ChannelError::Close(format!("Peer's feerate much too low. Actual: {}. Our expected lower limit: {}", feerate_per_kw, lower_limit)));
+               // Some fee estimators round up to the next full sat/vbyte (ie 250 sats per kw), causing
+               // occasional issues with feerate disagreements between an initiator that wants a feerate
+               // of 1.1 sat/vbyte and a receiver that wants 1.1 rounded up to 2. Thus, we always add 250
+               // sat/kw before the comparison here.
+               if feerate_per_kw + 250 < lower_limit {
+                       return Err(ChannelError::Close(format!("Peer's feerate much too low. Actual: {}. Our expected lower limit: {} (- 250)", feerate_per_kw, lower_limit)));
                }
                // We only bound the fee updates on the upper side to prevent completely absurd feerates,
                // always accepting up to 25 sat/vByte or 10x our fee estimator's "High Priority" fee.