Negotiate 0FC channels if configured

Author: tankyleo

src/config.rs

@@ -188,7 +188,8 @@ pub struct Config {
 	/// used to send pre-flight probes.
 	pub probing_liquidity_limit_multiplier: u64,
 	/// Configuration options pertaining to Anchor channels, i.e., channels for which the
-	/// `option_anchors_zero_fee_htlc_tx` channel type is negotiated.
+	/// `option_zero_fee_commitments` or `option_anchors_zero_fee_htlc_tx` channel type is
+	/// negotiated.
 	///
 	/// Please refer to [`AnchorChannelsConfig`] for further information on Anchor channels.
 	pub anchor_channels_config: AnchorChannelsConfig,
@@ -287,7 +288,7 @@ impl Default for HumanReadableNamesConfig {
 }
 
 /// Configuration options pertaining to 'Anchor' channels, i.e., channels for which the
-/// `option_anchors_zero_fee_htlc_tx` channel type is negotiated.
+/// `option_zero_fee_commitments` or `option_anchors_zero_fee_htlc_tx` channel type is negotiated.
 ///
 /// Prior to the introduction of Anchor channels, the on-chain fees paying for the transactions
 /// issued on channel closure were pre-determined and locked-in at the time of the channel
@@ -421,6 +422,8 @@ pub(crate) fn default_user_config(config: &Config) -> UserConfig {
 	// will mostly be relevant for inbound channels.
 	let mut user_config = UserConfig::default();
 	user_config.channel_handshake_limits.force_announced_channel_preference = false;
+	user_config.channel_handshake_config.negotiate_anchor_zero_fee_commitments =
+		config.anchor_channels_config.enable_zero_fee_commitments;
 	user_config.reject_inbound_splices = false;
 
 	if may_announce_channel(config).is_err() {

tests/common/mod.rs

@@ -382,6 +382,11 @@ pub(crate) fn random_node_alias() -> Option<NodeAlias> {
 pub(crate) fn random_config() -> TestConfig {
 	let mut node_config = Config::default();
 
+	// We want 0FC channels to be negotiated half the time, 0.49 is good enough
+	let zero_fee_commitments = rand::random_bool(0.7);
+	println!("Negotiating zero-fee commitment channels: {}", zero_fee_commitments);
+	node_config.anchor_channels_config.enable_zero_fee_commitments = zero_fee_commitments;
+
 	node_config.network = Network::Regtest;
 	println!("Setting network: {}", node_config.network);
 
@@ -1579,10 +1584,8 @@ pub(crate) async fn do_channel_full_cycle<E: ElectrumApi>(
 		let node_a_outbound_capacity_msat = node_a.list_channels()[0].outbound_capacity_msat;
 		let node_a_reserve_msat =
 			node_a.list_channels()[0].unspendable_punishment_reserve.unwrap() * 1000;
-		// TODO: Zero-fee commitment channels are anchor channels, but do not allocate any
-		// funds to the anchor, so this will need to be updated when we ship these channels
-		// in ldk-node.
-		let node_a_anchors_msat = if expect_anchor_channel { 2 * 330 * 1000 } else { 0 };
+		let zero_fee_commitments = node_a.list_channels()[0].feerate_sat_per_1000_weight == 0;
+		let node_a_anchors_msat = if zero_fee_commitments { 0 } else { 2 * 330 * 1000 };
 		let funding_amount_msat = node_a.list_channels()[0].channel_value_sats * 1000;
 		// Node B does not have any reserve, so we only subtract a few items on node A's
 		// side to arrive at node B's capacity

tests/integration_tests_rust.rs

@@ -1543,8 +1543,9 @@ async fn splice_channel() {
 	let user_channel_id_b = expect_channel_ready_event!(node_b, node_a.node_id());
 
 	let opening_transaction_fee_sat = 156;
-	let closing_transaction_fee_sat = 614;
-	let anchor_output_sat = 330;
+	let zero_fee_commitments = node_a.list_channels()[0].feerate_sat_per_1000_weight == 0;
+	let closing_transaction_fee_sat = if zero_fee_commitments { 0 } else { 614 };
+	let anchor_output_sat = if zero_fee_commitments { 0 } else { 330 };
 
 	assert_eq!(
 		node_a.list_balances().total_onchain_balance_sats,