Emit SpliceFailed event upon reload

Similarly to when a peer is disconnected, when a node is reloaded any
splice that hasn't reaching FundingNegotiation::AwaitingSignatures will
be reset. This should produce a SpliceFailed event. However, since other
FundingNegotiation variants are not persisted, the data to produced the
SpliceFailed event upon reload is lost. Therefore, opportunistically
persist a SpliceFailed event for these cases such that it is available
upon reload.

Author: jkczyz

lightning/src/ln/channel.rs

@@ -6732,6 +6732,13 @@ impl FundingNegotiationContext {
 		let contributed_outputs = self.our_funding_outputs;
 		(contributed_inputs, contributed_outputs)
 	}
+
+	fn to_contributed_inputs_and_outputs(&self) -> (Vec<bitcoin::OutPoint>, Vec<TxOut>) {
+		let contributed_inputs =
+			self.our_funding_inputs.iter().map(|input| input.utxo.outpoint).collect();
+		let contributed_outputs = self.our_funding_outputs.clone();
+		(contributed_inputs, contributed_outputs)
+	}
 }
 
 // Holder designates channel data owned for the benefit of the user client.
@@ -6865,6 +6872,45 @@ pub struct SpliceFundingFailed {
 	pub contributed_outputs: Vec<bitcoin::TxOut>,
 }
 
+macro_rules! maybe_create_splice_funding_failed {
+	($pending_splice: expr, $get: ident, $contributed_inputs_and_outputs: ident) => {{
+		$pending_splice
+			.and_then(|pending_splice| pending_splice.funding_negotiation.$get())
+			.filter(|funding_negotiation| funding_negotiation.is_initiator())
+			.map(|funding_negotiation| {
+				let funding_txo = funding_negotiation
+					.as_funding()
+					.and_then(|funding| funding.get_funding_txo())
+					.map(|txo| txo.into_bitcoin_outpoint());
+
+				let channel_type = funding_negotiation
+					.as_funding()
+					.map(|funding| funding.get_channel_type().clone());
+
+				let (contributed_inputs, contributed_outputs) = match funding_negotiation {
+					FundingNegotiation::AwaitingAck { context } => {
+						context.$contributed_inputs_and_outputs()
+					},
+					FundingNegotiation::ConstructingTransaction {
+						interactive_tx_constructor,
+						..
+					} => interactive_tx_constructor.$contributed_inputs_and_outputs(),
+					FundingNegotiation::AwaitingSignatures { .. } => {
+						debug_assert!(false);
+						(Vec::new(), Vec::new())
+					},
+				};
+
+				SpliceFundingFailed {
+					funding_txo,
+					channel_type,
+					contributed_inputs,
+					contributed_outputs,
+				}
+			})
+	}};
+}
+
 pub struct SpliceFundingPromotion {
 	pub funding_txo: OutPoint,
 	pub monitor_update: Option<ChannelMonitorUpdate>,
@@ -6977,42 +7023,11 @@ where
 		debug_assert!(self.context.interactive_tx_signing_session.is_none());
 		self.context.channel_state.clear_quiescent();
 
-		let splice_funding_failed = self
-			.pending_splice
-			.as_mut()
-			.and_then(|pending_splice| pending_splice.funding_negotiation.take())
-			.filter(|funding_negotiation| funding_negotiation.is_initiator())
-			.map(|funding_negotiation| {
-				let funding_txo = funding_negotiation
-					.as_funding()
-					.and_then(|funding| funding.get_funding_txo())
-					.map(|txo| txo.into_bitcoin_outpoint());
-
-				let channel_type = funding_negotiation
-					.as_funding()
-					.map(|funding| funding.get_channel_type().clone());
-
-				let (contributed_inputs, contributed_outputs) = match funding_negotiation {
-					FundingNegotiation::AwaitingAck { context } => {
-						context.into_contributed_inputs_and_outputs()
-					},
-					FundingNegotiation::ConstructingTransaction {
-						interactive_tx_constructor,
-						..
-					} => interactive_tx_constructor.into_contributed_inputs_and_outputs(),
-					FundingNegotiation::AwaitingSignatures { .. } => {
-						debug_assert!(false);
-						(Vec::new(), Vec::new())
-					},
-				};
-
-				SpliceFundingFailed {
-					funding_txo,
-					channel_type,
-					contributed_inputs,
-					contributed_outputs,
-				}
-			});
+		let splice_funding_failed = maybe_create_splice_funding_failed!(
+			self.pending_splice.as_mut(),
+			take,
+			into_contributed_inputs_and_outputs
+		);
 
 		if self.pending_funding().is_empty() {
 			self.pending_splice.take();
@@ -7021,6 +7036,18 @@ where
 		splice_funding_failed
 	}
 
+	pub(super) fn maybe_splice_funding_failed(&self) -> Option<SpliceFundingFailed> {
+		if !self.should_reset_pending_splice_state() {
+			return None;
+		}
+
+		maybe_create_splice_funding_failed!(
+			self.pending_splice.as_ref(),
+			as_ref,
+			to_contributed_inputs_and_outputs
+		)
+	}
+
 	#[rustfmt::skip]
 	fn check_remote_fee<F: Deref, L: Deref>(
 		channel_type: &ChannelTypeFeatures, fee_estimator: &LowerBoundedFeeEstimator<F>,

lightning/src/ln/channelmanager.rs

@@ -16134,7 +16134,32 @@ where
 			}
 		}
 
-		let events = self.pending_events.lock().unwrap();
+
+		// Since some FundingNegotiation variants are not persisted, any splice in such state must
+		// be failed upon reload. However, as the necessary information for the SpliceFailed event
+		// is not persisted, the event itself needs to be persisted even though it hasn't been
+		// emitted yet. These are removed after the events are written.
+		let mut events = self.pending_events.lock().unwrap();
+		let event_count = events.len();
+		for peer_state in peer_states.iter() {
+			for chan in peer_state.channel_by_id.values().filter_map(Channel::as_funded) {
+				if let Some(splice_funding_failed) = chan.maybe_splice_funding_failed() {
+					events.push_back((
+						events::Event::SpliceFailed {
+							channel_id: chan.context.channel_id(),
+							counterparty_node_id: chan.context.get_counterparty_node_id(),
+							user_channel_id: chan.context.get_user_id(),
+							abandoned_funding_txo: splice_funding_failed.funding_txo,
+							channel_type: splice_funding_failed.channel_type,
+							contributed_inputs: splice_funding_failed.contributed_inputs,
+							contributed_outputs: splice_funding_failed.contributed_outputs,
+						},
+						None,
+					));
+				}
+			}
+		}
+
 		// LDK versions prior to 0.0.115 don't support post-event actions, thus if there's no
 		// actions at all, skip writing the required TLV. Otherwise, pre-0.0.115 versions will
 		// refuse to read the new ChannelManager.
@@ -16251,6 +16276,9 @@ where
 			(21, WithoutLength(&self.flow.writeable_async_receive_offer_cache()), required),
 		});
 
+		// Remove the SpliceFailed events added earlier.
+		events.truncate(event_count);
+
 		Ok(())
 	}
 }

lightning/src/ln/interactivetxs.rs

@@ -2100,6 +2100,22 @@ impl InteractiveTxConstructor {
 		(contributed_inputs, contributed_outputs)
 	}
 
+	pub(super) fn to_contributed_inputs_and_outputs(&self) -> (Vec<BitcoinOutPoint>, Vec<TxOut>) {
+		let contributed_inputs = self
+			.inputs_to_contribute
+			.iter()
+			.filter(|(_, input)| !input.is_shared())
+			.map(|(_, input)| input.tx_in().previous_output)
+			.collect();
+		let contributed_outputs = self
+			.outputs_to_contribute
+			.iter()
+			.filter(|(_, output)| !output.is_shared())
+			.map(|(_, output)| output.tx_out().clone())
+			.collect();
+		(contributed_inputs, contributed_outputs)
+	}
+
 	pub fn is_initiator(&self) -> bool {
 		self.is_initiator
 	}

lightning/src/ln/splicing_tests.rs

@@ -431,10 +431,10 @@ fn do_test_splice_state_reset_on_disconnect(reload: bool) {
 	} else {
 		nodes[0].node.peer_disconnected(node_id_1);
 		nodes[1].node.peer_disconnected(node_id_0);
-
-		let _event = get_event!(nodes[0], Event::SpliceFailed);
 	}
 
+	let _event = get_event!(nodes[0], Event::SpliceFailed);
+
 	let mut reconnect_args = ReconnectArgs::new(&nodes[0], &nodes[1]);
 	reconnect_args.send_channel_ready = (true, true);
 	reconnect_args.send_announcement_sigs = (true, true);
@@ -490,10 +490,10 @@ fn do_test_splice_state_reset_on_disconnect(reload: bool) {
 	} else {
 		nodes[0].node.peer_disconnected(node_id_1);
 		nodes[1].node.peer_disconnected(node_id_0);
-
-		let _event = get_event!(nodes[0], Event::SpliceFailed);
 	}
 
+	let _event = get_event!(nodes[0], Event::SpliceFailed);
+
 	let mut reconnect_args = ReconnectArgs::new(&nodes[0], &nodes[1]);
 	reconnect_args.send_channel_ready = (true, true);
 	reconnect_args.send_announcement_sigs = (true, true);