Negotiate 0FC channels if the anchor config is set

Author: tankyleo

src/config.rs

@@ -171,15 +171,17 @@ 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.
 	///
 	/// If set to `Some`, we'll try to open new channels with Anchors enabled, i.e., new channels
-	/// will be negotiated with the `option_anchors_zero_fee_htlc_tx` channel type if supported by
-	/// the counterparty. Note that this won't prevent us from opening non-Anchor channels if the
-	/// counterparty doesn't support `option_anchors_zero_fee_htlc_tx`. If set to `None`, new
-	/// channels will be negotiated with the legacy `option_static_remotekey` channel type only.
+	/// will be negotiated with the `option_zero_fee_commitments` channel type first, then the
+	/// `option_anchors_zero_fee_htlc_tx` channel type if supported by the counterparty. Note
+	/// that this won't prevent us from opening non-Anchor channels if the counterparty doesn't
+	/// support `option_anchors_zero_fee_htlc_tx`. If set to `None`, new channels will be
+	/// negotiated with the legacy `option_static_remotekey` channel type only.
 	///
 	/// **Note:** If set to `None` *after* some Anchor channels have already been
 	/// opened, no dedicated emergency on-chain reserve will be maintained for these channels,
@@ -282,7 +284,7 @@ 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
@@ -404,6 +406,8 @@ pub(crate) fn default_user_config(config: &Config) -> UserConfig {
 	user_config.channel_handshake_limits.force_announced_channel_preference = false;
 	user_config.channel_handshake_config.negotiate_anchors_zero_fee_htlc_tx =
 		config.anchor_channels_config.is_some();
+	user_config.channel_handshake_config.negotiate_anchor_zero_fee_commitments =
+		config.anchor_channels_config.is_some();
 	user_config.reject_inbound_splices = false;
 
 	if may_announce_channel(config).is_err() {

tests/common/mod.rs

@@ -1408,10 +1408,9 @@ 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 };
+		// If we expect an anchor channel, this will be a 0FC channel, so no funds will be
+		// allocated to the anchor.
+		let node_a_anchors_msat = 0;
 		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

@@ -1023,17 +1023,12 @@ 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;
 
 	assert_eq!(
 		node_a.list_balances().total_onchain_balance_sats,
 		premine_amount_sat - 4_000_000 - opening_transaction_fee_sat
 	);
-	assert_eq!(
-		node_a.list_balances().total_lightning_balance_sats,
-		4_000_000 - closing_transaction_fee_sat - anchor_output_sat
-	);
+	assert_eq!(node_a.list_balances().total_lightning_balance_sats, 4_000_000);
 	assert_eq!(node_b.list_balances().total_lightning_balance_sats, 0);
 
 	// Test that splicing and payments fail when there are insufficient funds
@@ -1101,10 +1096,7 @@ async fn splice_channel() {
 	// Mine a block to give time for the HTLC to resolve
 	generate_blocks_and_wait(&bitcoind.client, &electrsd.client, 1).await;
 
-	assert_eq!(
-		node_a.list_balances().total_lightning_balance_sats,
-		4_000_000 - closing_transaction_fee_sat - anchor_output_sat + amount_msat / 1000
-	);
+	assert_eq!(node_a.list_balances().total_lightning_balance_sats, 4_000_000 + amount_msat / 1000);
 	assert_eq!(
 		node_b.list_balances().total_lightning_balance_sats,
 		expected_splice_in_lightning_balance_sat - amount_msat / 1000
@@ -1138,7 +1130,7 @@ async fn splice_channel() {
 	);
 	assert_eq!(
 		node_a.list_balances().total_lightning_balance_sats,
-		4_000_000 - closing_transaction_fee_sat - anchor_output_sat - expected_splice_out_fee_sat
+		4_000_000 - expected_splice_out_fee_sat
 	);
 }