Allow setting a ChannelConfig for LSPS2 JIT channels

src/liquidity/mod.rs

@@ -26,7 +26,7 @@ use lightning_liquidity::lsps1::client::LSPS1ClientConfig as LdkLSPS1ClientConfi
 use lightning_liquidity::lsps2::client::LSPS2ClientConfig as LdkLSPS2ClientConfig;
 use lightning_liquidity::lsps2::service::LSPS2ServiceConfig as LdkLSPS2ServiceConfig;
 use lightning_liquidity::{LiquidityClientConfig, LiquidityServiceConfig};
-pub use service::lsps2::LSPS2ServiceConfig;
+pub use service::lsps2::{LSPS2ChannelConfig, LSPS2ServiceConfig};
 use tokio::sync::oneshot;
 
 use crate::builder::BuildError;

src/liquidity/service/lsps2.rs

@@ -22,6 +22,7 @@ use lightning_liquidity::lsps2::msgs::LSPS2RawOpeningFeeParams;
 use lightning_liquidity::lsps2::service::LSPS2ServiceConfig as LdkLSPS2ServiceConfig;
 use lightning_types::payment::PaymentHash;
 
+use crate::config::MaxDustHTLCExposure;
 use crate::logger::{log_error, LdkLogger};
 use crate::types::{ChannelManager, KeysManager, LiquidityManager, PeerManager, Wallet};
 use crate::{total_anchor_channels_reserve_sats, Config};
@@ -106,6 +107,31 @@ pub struct LSPS2ServiceConfig {
 	///
 	/// [`Node::open_0reserve_channel`]: crate::Node::open_0reserve_channel
 	pub disable_client_reserve: bool,
+	/// The channel config we'll apply to the JIT channels we open to clients, allowing to
+	/// configure them separately from regular channels.
+	///
+	/// Any unset fields, or if set to `None` entirely, fall back to the node-wide config.
+	pub channel_config: Option<LSPS2ChannelConfig>,
+}
+
+/// A subset of channel configuration options applied to the JIT channels opened towards
+/// clients when acting as an LSPS2 service.
+///
+/// Any fields set to `None` fall back to the node-wide config.
+///
+/// Note that the forwarding fees of JIT channels are always set to zero, as we're
+/// compensated via the channel opening fee.
+#[derive(Debug, Clone)]
+#[cfg_attr(feature = "uniffi", derive(uniffi::Record))]
+pub struct LSPS2ChannelConfig {
+	/// The difference in the CLTV value between incoming HTLCs and an outbound HTLC forwarded
+	/// over the channel.
+	pub cltv_expiry_delta: Option<u16>,
+	/// The total exposure we're willing to allow to potential loss due to dust HTLCs.
+	pub max_dust_htlc_exposure: Option<MaxDustHTLCExposure>,
+	/// The additional fee we're willing to pay to avoid waiting for the counterparty's
+	/// `to_self_delay` to reclaim funds.
+	pub force_close_avoidance_max_fee_satoshis: Option<u64>,
 }
 
 impl<L: Deref> LSPS2ServiceLiquiditySource<L>
@@ -487,12 +513,28 @@ where
 				debug_assert!(!config.channel_handshake_config.announce_for_forwarding);
 				debug_assert!(config.accept_forwards_to_priv_channels);
 
-				// We set the forwarding fee to 0 for now as we're getting paid by the channel fee.
-				//
-				// TODO: revisit this decision eventually.
+				// We set the forwarding fees to 0 as we're getting paid by the channel opening
+				// fee.
 				config.channel_config.forwarding_fee_base_msat = 0;
 				config.channel_config.forwarding_fee_proportional_millionths = 0;
 
+				if let Some(jit_channel_config) = service_config.channel_config.as_ref() {
+					if let Some(cltv_expiry_delta) = jit_channel_config.cltv_expiry_delta {
+						config.channel_config.cltv_expiry_delta = cltv_expiry_delta;
+					}
+					if let Some(max_dust_htlc_exposure) = jit_channel_config.max_dust_htlc_exposure
+					{
+						config.channel_config.max_dust_htlc_exposure =
+							max_dust_htlc_exposure.into();
+					}
+					if let Some(force_close_avoidance_max_fee_satoshis) =
+						jit_channel_config.force_close_avoidance_max_fee_satoshis
+					{
+						config.channel_config.force_close_avoidance_max_fee_satoshis =
+							force_close_avoidance_max_fee_satoshis;
+					}
+				}
+
 				let result = if service_config.disable_client_reserve {
 					self.channel_manager.create_channel_to_trusted_peer_0reserve(
 						their_network_key,

tests/integration_tests_rust.rs

@@ -31,7 +31,7 @@ use electrsd::corepc_node::{self, Node as BitcoinD};
 use electrsd::ElectrsD;
 use ldk_node::config::{AsyncPaymentsRole, EsploraSyncConfig, DEFAULT_FULL_SCAN_STOP_GAP};
 use ldk_node::entropy::NodeEntropy;
-use ldk_node::liquidity::LSPS2ServiceConfig;
+use ldk_node::liquidity::{LSPS2ChannelConfig, LSPS2ServiceConfig};
 use ldk_node::payment::{
 	ConfirmationStatus, PaymentDetails, PaymentDirection, PaymentKind, PaymentStatus,
 	TransactionType, UnifiedPaymentResult,
@@ -2787,6 +2787,12 @@ async fn do_lsps2_client_service_integration(client_trusts_lsp: bool) {
 	// Setup three nodes: service, client, and payer
 	let channel_opening_fee_ppm = 10_000;
 	let channel_over_provisioning_ppm = 100_000;
+
+	let jit_channel_config = LSPS2ChannelConfig {
+		cltv_expiry_delta: None,
+		max_dust_htlc_exposure: None,
+		force_close_avoidance_max_fee_satoshis: Some(1337),
+	};
 	let lsps2_service_config = LSPS2ServiceConfig {
 		require_token: None,
 		advertise_service: false,
@@ -2799,6 +2805,7 @@ async fn do_lsps2_client_service_integration(client_trusts_lsp: bool) {
 		max_client_to_self_delay: 1024,
 		client_trusts_lsp,
 		disable_client_reserve: false,
+		channel_config: Some(jit_channel_config),
 	};
 
 	let service_config = random_config(true);
@@ -2890,6 +2897,14 @@ async fn do_lsps2_client_service_integration(client_trusts_lsp: bool) {
 	let channel_value_sats = client_node.list_channels().first().unwrap().channel_value_sats;
 	assert_eq!(channel_value_sats, expected_channel_size_sat);
 
+	let jit_channel = service_node
+		.list_channels()
+		.into_iter()
+		.find(|c| c.counterparty.node_id == client_node.node_id())
+		.unwrap();
+	assert_eq!(jit_channel.config.force_close_avoidance_max_fee_satoshis, 1337);
+	assert_eq!(jit_channel.config.forwarding_fee_base_msat, 0);
+
 	println!("Generating regular invoice!");
 	let invoice_description =
 		Bolt11InvoiceDescription::Direct(Description::new(String::from("asdf")).unwrap()).into();
@@ -3118,6 +3133,7 @@ async fn lsps2_client_trusts_lsp() {
 		max_client_to_self_delay: 1024,
 		client_trusts_lsp: true,
 		disable_client_reserve: false,
+		channel_config: None,
 	};
 
 	let service_config = random_config(true);
@@ -3293,6 +3309,7 @@ async fn lsps2_lsp_trusts_client_but_client_does_not_claim() {
 		max_client_to_self_delay: 1024,
 		client_trusts_lsp: false,
 		disable_client_reserve: false,
+		channel_config: None,
 	};
 
 	let service_config = random_config(true);
@@ -4092,6 +4109,7 @@ async fn do_lsps2_multi_lsp_picks_cheapest(reverse_order: bool) {
 		max_client_to_self_delay: 1024,
 		client_trusts_lsp: true,
 		disable_client_reserve: false,
+		channel_config: None,
 	};
 	let cheap_node_config = random_config(true);
 	setup_builder!(cheap_builder, cheap_node_config.node_config);
@@ -4115,6 +4133,7 @@ async fn do_lsps2_multi_lsp_picks_cheapest(reverse_order: bool) {
 		max_client_to_self_delay: 1024,
 		client_trusts_lsp: true,
 		disable_client_reserve: false,
+		channel_config: None,
 	};
 	let expensive_node_config = random_config(true);
 	setup_builder!(expensive_builder, expensive_node_config.node_config);