Correct the units of counterparty htlc tx excess fees calculations

The widely used sats/kWU ratio is equivalent to msats/WU

Author: tankyleo

lightning/src/ln/chan_utils.rs

@@ -199,11 +199,11 @@ pub(crate) fn commit_tx_fee_sat(feerate_per_kw: u32, num_htlcs: usize, channel_t
 pub(crate) fn per_outbound_htlc_counterparty_commit_tx_fee_msat(feerate_per_kw: u32, channel_type_features: &ChannelTypeFeatures) -> u64 {
 	// Note that we need to divide before multiplying to round properly,
 	// since the lowest denomination of bitcoin on-chain is the satoshi.
-	let commitment_tx_fee = COMMITMENT_TX_WEIGHT_PER_HTLC * feerate_per_kw as u64 / 1000 * 1000;
+	let commitment_tx_fee_msat = COMMITMENT_TX_WEIGHT_PER_HTLC * feerate_per_kw as u64 / 1000 * 1000;
 	if channel_type_features.supports_anchors_zero_fee_htlc_tx() {
-		commitment_tx_fee
+		commitment_tx_fee_msat
 	} else {
-		commitment_tx_fee + htlc_success_tx_weight(channel_type_features) * feerate_per_kw as u64 / 1000
+		commitment_tx_fee_msat + htlc_success_tx_weight(channel_type_features) * feerate_per_kw as u64
 	}
 }
 

lightning/src/ln/channel.rs

@@ -3669,10 +3669,10 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider {
 			if !self.channel_type.supports_anchors_zero_fee_htlc_tx() {
 				on_counterparty_tx_dust_exposure_msat +=
 					on_counterparty_tx_accepted_nondust_htlcs as u64 * htlc_success_tx_weight(&self.channel_type)
-					* excess_feerate as u64 / 1000;
+					* excess_feerate as u64;
 				on_counterparty_tx_dust_exposure_msat +=
 					on_counterparty_tx_offered_nondust_htlcs as u64 * htlc_timeout_tx_weight(&self.channel_type)
-					* excess_feerate as u64 / 1000;
+					* excess_feerate as u64;
 			}
 		}