LSPS2: Fail (or abandon) intercepted HTLCs if LSP channel open fails

lightning-liquidity/src/lsps2/service.rs

@@ -32,7 +32,7 @@ use crate::prelude::{new_hash_map, HashMap};
 use crate::sync::{Arc, Mutex, MutexGuard, RwLock};
 
 use lightning::events::HTLCHandlingFailureType;
-use lightning::ln::channelmanager::{AChannelManager, InterceptId};
+use lightning::ln::channelmanager::{AChannelManager, FailureCode, InterceptId};
 use lightning::ln::msgs::{ErrorAction, LightningError};
 use lightning::ln::types::ChannelId;
 use lightning::util::errors::APIError;
@@ -985,6 +985,128 @@ where
 		Ok(())
 	}
 
+	/// Abandons a pending JIT‐open flow for `user_channel_id`, removing all local state.
+	///
+	/// This removes the intercept SCID, any outbound channel state, and associated
+	/// channel‐ID mappings for the specified `user_channel_id`, but only while no payment
+	/// has been forwarded yet and no channel has been opened on-chain.
+	///
+	/// Returns an error if:
+	///  - there is no channel matching `user_channel_id`, or
+	///  - a payment has already been forwarded or a channel has already been opened
+	///
+	/// Note: this does *not* close or roll back any on‐chain channel which may already
+	/// have been opened. The caller must call this before or instead of initiating the channel
+	/// open, as it only affects the local LSPS2 state and doesn't affect any channels that
+	/// might already exist on-chain. Any pending channel open attempts must be managed
+	/// separately.
+	pub fn channel_open_abandoned(
+		&self, counterparty_node_id: &PublicKey, user_channel_id: u128,
+	) -> Result<(), APIError> {
+		let outer_state_lock = self.per_peer_state.read().unwrap();
+		let inner_state_lock =
+			outer_state_lock.get(counterparty_node_id).ok_or_else(|| APIError::APIMisuseError {
+				err: format!("No counterparty state for: {}", counterparty_node_id),
+			})?;
+		let mut peer_state = inner_state_lock.lock().unwrap();
+
+		let intercept_scid = peer_state
+			.intercept_scid_by_user_channel_id
+			.get(&user_channel_id)
+			.copied()
+			.ok_or_else(|| APIError::APIMisuseError {
+				err: format!("Could not find a channel with user_channel_id {}", user_channel_id),
+			})?;
+
+		let jit_channel = peer_state
+			.outbound_channels_by_intercept_scid
+			.get(&intercept_scid)
+			.ok_or_else(|| APIError::APIMisuseError {
+				err: format!(
+					"Failed to map intercept_scid {} for user_channel_id {} to a channel.",
+					intercept_scid, user_channel_id,
+				),
+			})?;
+
+		let is_pending = matches!(
+			jit_channel.state,
+			OutboundJITChannelState::PendingInitialPayment { .. }
+				| OutboundJITChannelState::PendingChannelOpen { .. }
+		);
+
+		if !is_pending {
+			return Err(APIError::APIMisuseError {
+				err: "Cannot abandon channel open after channel creation or payment forwarding"
+					.to_string(),
+			});
+		}
+
+		peer_state.intercept_scid_by_user_channel_id.remove(&user_channel_id);
+		peer_state.outbound_channels_by_intercept_scid.remove(&intercept_scid);
+		peer_state.intercept_scid_by_channel_id.retain(|_, &mut scid| scid != intercept_scid);
+
+		Ok(())
+	}
+
+	/// Used to fail intercepted HTLCs backwards when a channel open attempt ultimately fails.
+	///
+	/// This function should be called after receiving an [`LSPS2ServiceEvent::OpenChannel`] event
+	/// but only if the channel could not be successfully established. It resets the JIT channel
+	/// state so that the payer may try the payment again.
+	///
+	/// [`LSPS2ServiceEvent::OpenChannel`]: crate::lsps2::event::LSPS2ServiceEvent::OpenChannel
+	pub fn channel_open_failed(
+		&self, counterparty_node_id: &PublicKey, user_channel_id: u128,
+	) -> Result<(), APIError> {
+		let outer_state_lock = self.per_peer_state.read().unwrap();
+
+		let inner_state_lock =
+			outer_state_lock.get(counterparty_node_id).ok_or_else(|| APIError::APIMisuseError {
+				err: format!("No counterparty state for: {}", counterparty_node_id),
+			})?;
+
+		let mut peer_state = inner_state_lock.lock().unwrap();
+
+		let intercept_scid = peer_state
+			.intercept_scid_by_user_channel_id
+			.get(&user_channel_id)
+			.copied()
+			.ok_or_else(|| APIError::APIMisuseError {
+				err: format!("Could not find a channel with user_channel_id {}", user_channel_id),
+			})?;
+
+		let jit_channel = peer_state
+			.outbound_channels_by_intercept_scid
+			.get_mut(&intercept_scid)
+			.ok_or_else(|| APIError::APIMisuseError {
+			err: format!(
+				"Failed to map intercept_scid {} for user_channel_id {} to a channel.",
+				intercept_scid, user_channel_id,
+			),
+		})?;
+
+		if let OutboundJITChannelState::PendingChannelOpen { payment_queue, .. } =
+			&mut jit_channel.state
+		{
+			let intercepted_htlcs = payment_queue.clear();
+			for htlc in intercepted_htlcs {
+				self.channel_manager.get_cm().fail_htlc_backwards_with_reason(
+					&htlc.payment_hash,
+					FailureCode::TemporaryNodeFailure,
+				);
+			}
+
+			jit_channel.state = OutboundJITChannelState::PendingInitialPayment {
+				payment_queue: PaymentQueue::new(),
+			};
+			Ok(())
+		} else {
+			Err(APIError::APIMisuseError {
+				err: "Channel is not in the PendingChannelOpen state.".to_string(),
+			})
+		}
+	}
+
 	/// Forward [`Event::ChannelReady`] event parameters into this function.
 	///
 	/// Will forward the intercepted HTLC if it matches a channel

lightning-liquidity/tests/common/mod.rs

@@ -9,6 +9,7 @@ use lightning::sign::EntropySource;
 
 use bitcoin::blockdata::constants::{genesis_block, ChainHash};
 use bitcoin::blockdata::transaction::Transaction;
+use bitcoin::secp256k1::SecretKey;
 use bitcoin::Network;
 use lightning::chain::channelmonitor::ANTI_REORG_DELAY;
 use lightning::chain::{chainmonitor, BestBlock, Confirm};
@@ -34,6 +35,8 @@ use lightning::util::persist::{
 	SCORER_PERSISTENCE_SECONDARY_NAMESPACE,
 };
 use lightning::util::test_utils;
+use lightning_liquidity::lsps2::client::{LSPS2ClientConfig, LSPS2ClientHandler};
+use lightning_liquidity::lsps2::service::{LSPS2ServiceConfig, LSPS2ServiceHandler};
 use lightning_liquidity::{LiquidityClientConfig, LiquidityManager, LiquidityServiceConfig};
 use lightning_persister::fs_store::FilesystemStore;
 
@@ -487,7 +490,7 @@ pub(crate) fn create_liquidity_node(
 	}
 }
 
-pub(crate) fn create_service_and_client_nodes(
+fn create_service_and_client_nodes(
 	persist_dir: &str, service_config: LiquidityServiceConfig, client_config: LiquidityClientConfig,
 ) -> (Node, Node) {
 	let persist_temp_path = env::temp_dir().join(persist_dir);
@@ -671,3 +674,53 @@ fn advance_chain(node: &mut Node, num_blocks: u32) {
 		}
 	}
 }
+
+pub(crate) fn setup_test_lsps2() -> (
+	&'static LSPS2ClientHandler<Arc<KeysManager>>,
+	&'static LSPS2ServiceHandler<Arc<ChannelManager>>,
+	bitcoin::secp256k1::PublicKey,
+	bitcoin::secp256k1::PublicKey,
+	&'static Node,
+	&'static Node,
+	[u8; 32],
+) {
+	let promise_secret = [42; 32];
+	let signing_key = SecretKey::from_slice(&promise_secret).unwrap();
+	let lsps2_service_config = LSPS2ServiceConfig { promise_secret };
+	let service_config = LiquidityServiceConfig {
+		#[cfg(lsps1_service)]
+		lsps1_service_config: None,
+		lsps2_service_config: Some(lsps2_service_config),
+		advertise_service: true,
+	};
+
+	let lsps2_client_config = LSPS2ClientConfig::default();
+	let client_config = LiquidityClientConfig {
+		lsps1_client_config: None,
+		lsps2_client_config: Some(lsps2_client_config),
+	};
+
+	let (service_node, client_node) =
+		create_service_and_client_nodes("webhook_registration_flow", service_config, client_config);
+
+	// Leak the nodes to extend their lifetime to 'static since this is test code
+	let service_node = Box::leak(Box::new(service_node));
+	let client_node = Box::leak(Box::new(client_node));
+
+	let client_handler = client_node.liquidity_manager.lsps2_client_handler().unwrap();
+	let service_handler = service_node.liquidity_manager.lsps2_service_handler().unwrap();
+
+	let secp = bitcoin::secp256k1::Secp256k1::new();
+	let service_node_id = bitcoin::secp256k1::PublicKey::from_secret_key(&secp, &signing_key);
+	let client_node_id = client_node.channel_manager.get_our_node_id();
+
+	(
+		client_handler,
+		service_handler,
+		service_node_id,
+		client_node_id,
+		service_node,
+		client_node,
+		promise_secret,
+	)
+}