Limit external claim feerate bumps

[rust-lightning] / lightning / src / chain / package.rs

diff --git a/lightning/src/chain/package.rs b/lightning/src/chain/package.rs
index b66a2f70d3369f4aff6e012025b3e995d6918a9e..382ffac3e8e886c303207798fafe528c78406b0d 100644 (file)
--- a/lightning/src/chain/package.rs
+++ b/lightning/src/chain/package.rs
@@ -976,14 +976,23 @@ impl PackageTemplate {
        ) -> u32 where F::Target: FeeEstimator {
                let feerate_estimate = fee_estimator.bounded_sat_per_1000_weight(conf_target);
                if self.feerate_previous != 0 {
-                       // If old feerate inferior to actual one given back by Fee Estimator, use it to compute new fee...
+                       // Use the new fee estimate if it's higher than the one previously used.
                        if feerate_estimate as u64 > self.feerate_previous {
                                feerate_estimate
                        } else if !force_feerate_bump {
                                self.feerate_previous.try_into().unwrap_or(u32::max_value())
                        } else {
-                               // ...else just increase the previous feerate by 25% (because that's a nice number)
-                               (self.feerate_previous + (self.feerate_previous / 4)).try_into().unwrap_or(u32::max_value())
+                               // Our fee estimate has decreased, but our transaction remains unconfirmed after
+                               // using our previous fee estimate. This may point to an unreliable fee estimator,
+                               // so we choose to bump our previous feerate by 25%, making sure we don't use a
+                               // lower feerate or overpay by a large margin by limiting it to 5x the new fee
+                               // estimate.
+                               let previous_feerate = self.feerate_previous.try_into().unwrap_or(u32::max_value());
+                               let mut new_feerate = previous_feerate.saturating_add(previous_feerate / 4);
+                               if new_feerate > feerate_estimate * 5 {
+                                       new_feerate = cmp::max(feerate_estimate * 5, previous_feerate);
+                               }
+                               new_feerate
                        }
                } else {
                        feerate_estimate