f use helper, update err/comment for sp

Author: TheBlueMatt

lightning/src/ln/channel.rs

@@ -934,11 +934,11 @@ impl<Signer: Sign> Channel<Signer> {
 		let funders_amount_msat = msg.funding_satoshis * 1000 - msg.push_msat;
 		let commitment_tx_fee = msg.feerate_per_kw as u64 * (COMMITMENT_TX_BASE_WEIGHT + 4 * COMMITMENT_TX_WEIGHT_PER_HTLC) / 1000;
 		if funders_amount_msat / 1000 < commitment_tx_fee {
-			return Err(ChannelError::Close(format!("Funding amount ({}) can't even pay fee for initial commitment transaction fee of {}.", funders_amount_msat / 1000, commitment_tx_fee)));
+			return Err(ChannelError::Close(format!("Funding amount ({} sats) can't even pay fee for initial commitment transaction fee of {} sats.", funders_amount_msat / 1000, commitment_tx_fee)));
 		}
 
 		let to_remote_satoshis = funders_amount_msat / 1000 - commitment_tx_fee;
-		// While its reasonable for us to not meet the channel reserve initially (if they don't
+		// While it's reasonable for us to not meet the channel reserve initially (if they don't
 		// want to push much to us), our counterparty should always have more than our reserve.
 		if to_remote_satoshis < holder_selected_channel_reserve_satoshis {
 			return Err(ChannelError::Close("Insufficient funding amount for initial reserve".to_owned()));

lightning/src/ln/functional_tests.rs

@@ -1400,7 +1400,7 @@ fn test_chan_reserve_violation_outbound_htlc_inbound_chan() {
 	let mut nodes = create_network(2, &node_cfgs, &node_chanmgrs);
 
 	let mut push_amt = 100_000_000;
-	push_amt -= feerate_per_kw as u64 * (COMMITMENT_TX_BASE_WEIGHT + 4 * COMMITMENT_TX_WEIGHT_PER_HTLC) / 1000 * 1000;
+	push_amt -= commit_tx_fee_msat(feerate_per_kw, 4);
 	push_amt -= Channel::<EnforcingSigner>::get_holder_selected_channel_reserve_satoshis(100_000) * 1000;
 
 	let _ = create_announced_chan_between_nodes_with_value(&nodes, 0, 1, 100_000, push_amt, InitFeatures::known(), InitFeatures::known());
@@ -1431,7 +1431,7 @@ fn test_chan_reserve_violation_inbound_htlc_outbound_channel() {
 	// channel reserve violation (so their balance is channel reserve (1000 sats) + commitment
 	// transaction fee with 0 HTLCs (183 sats)).
 	let mut push_amt = 100_000_000;
-	push_amt -= feerate_per_kw as u64 * (COMMITMENT_TX_BASE_WEIGHT + 4 * COMMITMENT_TX_WEIGHT_PER_HTLC) / 1000 * 1000;
+	push_amt -= commit_tx_fee_msat(feerate_per_kw, 4);
 	push_amt -= Channel::<EnforcingSigner>::get_holder_selected_channel_reserve_satoshis(100_000) * 1000;
 	let chan = create_announced_chan_between_nodes_with_value(&nodes, 0, 1, 100_000, push_amt, InitFeatures::known(), InitFeatures::known());
 
@@ -1485,7 +1485,7 @@ fn test_chan_reserve_dust_inbound_htlcs_outbound_chan() {
 	// channel reserve violation (so their balance is channel reserve (1000 sats) + commitment
 	// transaction fee with 0 HTLCs (183 sats)).
 	let mut push_amt = 100_000_000;
-	push_amt -= feerate_per_kw as u64 * (COMMITMENT_TX_BASE_WEIGHT + 4 * COMMITMENT_TX_WEIGHT_PER_HTLC) / 1000 * 1000;
+	push_amt -= commit_tx_fee_msat(feerate_per_kw, 4);
 	push_amt -= Channel::<EnforcingSigner>::get_holder_selected_channel_reserve_satoshis(100_000) * 1000;
 	create_announced_chan_between_nodes_with_value(&nodes, 0, 1, 100000, push_amt, InitFeatures::known(), InitFeatures::known());