Limit minimum output size to the dust limit when RBF-bumping

diff --git a/lightning/src/chain/onchaintx.rs b/lightning/src/chain/onchaintx.rs
index d6777cc5c8cfd494409f5832f29efb3699bc21ab..8d70c7722ca15d1ec063119c68e61596aaea2aa3 100644 (file)
--- a/lightning/src/chain/onchaintx.rs
+++ b/lightning/src/chain/onchaintx.rs
@@ -380,7 +380,8 @@ impl<ChannelSigner: Sign> OnchainTxHandler<ChannelSigner> {
                let new_timer = Some(cached_request.get_height_timer(cur_height));
                if cached_request.is_malleable() {
                        let predicted_weight = cached_request.package_weight(&self.destination_script);
-                       if let Some((output_value, new_feerate)) = cached_request.compute_package_output(predicted_weight, fee_estimator, logger) {
+                       if let Some((output_value, new_feerate)) =
+                                       cached_request.compute_package_output(predicted_weight, self.destination_script.dust_value().as_sat(), fee_estimator, logger) {
                                assert!(new_feerate != 0);
 
                                let transaction = cached_request.finalize_package(self, output_value, self.destination_script.clone(), logger).unwrap();

diff --git a/lightning/src/chain/package.rs b/lightning/src/chain/package.rs
index a86add4b9e56efbd1606da736011db882b1e399d..8a17f726cf030a23b3fbda31248b791cf5b51b28 100644 (file)
--- a/lightning/src/chain/package.rs
+++ b/lightning/src/chain/package.rs
@@ -636,26 +636,25 @@ impl PackageTemplate {
                }
                current_height + LOW_FREQUENCY_BUMP_INTERVAL
        }
-       /// Returns value in satoshis to be included as package outgoing output amount and feerate with which package finalization should be done.
-       pub(crate) fn compute_package_output<F: Deref, L: Deref>(&self, predicted_weight: usize, fee_estimator: &F, logger: &L) -> Option<(u64, u64)>
+
+       /// Returns value in satoshis to be included as package outgoing output amount and feerate
+       /// which was used to generate the value. Will not return less than `dust_limit_sats` for the
+       /// value.
+       pub(crate) fn compute_package_output<F: Deref, L: Deref>(&self, predicted_weight: usize, dust_limit_sats: u64, fee_estimator: &F, logger: &L) -> Option<(u64, u64)>
                where F::Target: FeeEstimator,
                      L::Target: Logger,
        {
                debug_assert!(self.malleability == PackageMalleability::Malleable, "The package output is fixed for non-malleable packages");
                let input_amounts = self.package_amount();
+               assert!(dust_limit_sats as i64 > 0, "Output script must be broadcastable/have a 'real' dust limit.");
                // If old feerate is 0, first iteration of this claim, use normal fee calculation
                if self.feerate_previous != 0 {
                        if let Some((new_fee, feerate)) = feerate_bump(predicted_weight, input_amounts, self.feerate_previous, fee_estimator, logger) {
-                               // If new computed fee is superior at the whole claimable amount burn all in fees
-                               if new_fee > input_amounts {
-                                       return Some((0, feerate));
-                               } else {
-                                       return Some((input_amounts - new_fee, feerate));
-                               }
+                               return Some((cmp::max(input_amounts as i64 - new_fee as i64, dust_limit_sats as i64) as u64, feerate));
                        }
                } else {
                        if let Some((new_fee, feerate)) = compute_fee_from_spent_amounts(input_amounts, predicted_weight, fee_estimator, logger) {
-                               return Some((input_amounts - new_fee, feerate));
+                               return Some((cmp::max(input_amounts as i64 - new_fee as i64, dust_limit_sats as i64) as u64, feerate));
                        }
                }
                None