Emit SpliceFailed event during channel shutdown

When a channel has a pending splice and is shutdown, generate a
SpliceFailed event when necessary. This allows users to reclaim any
contributed UTXOs.

Author: jkczyz

lightning/src/ln/channel.rs

@@ -1191,6 +1191,9 @@ pub(crate) struct ShutdownResult {
 	pub(crate) unbroadcasted_funding_tx: Option<Transaction>,
 	pub(crate) channel_funding_txo: Option<OutPoint>,
 	pub(crate) last_local_balance_msat: u64,
+	/// If a splice was in progress when the channel was shut down, this contains
+	/// the splice funding information for emitting a SpliceFailed event.
+	pub(crate) splice_funding_failed: Option<SpliceFundingFailed>,
 }
 
 /// Tracks the transaction number, along with current and next commitment points.
@@ -2686,6 +2689,15 @@ pub(crate) struct SpliceInstructions {
 	locktime: u32,
 }
 
+impl SpliceInstructions {
+	fn into_contributed_inputs_and_outputs(self) -> (Vec<bitcoin::OutPoint>, Vec<TxOut>) {
+		(
+			self.our_funding_inputs.into_iter().map(|input| input.utxo.outpoint).collect(),
+			self.our_funding_outputs,
+		)
+	}
+}
+
 impl_writeable_tlv_based!(SpliceInstructions, {
 	(1, adjusted_funding_contribution, required),
 	(3, our_funding_inputs, required_vec),
@@ -6040,6 +6052,7 @@ where
 			is_manual_broadcast: self.is_manual_broadcast,
 			channel_funding_txo: funding.get_funding_txo(),
 			last_local_balance_msat: funding.value_to_self_msat,
+			splice_funding_failed: None,
 		}
 	}
 
@@ -6824,7 +6837,38 @@ where
 	}
 
 	pub fn force_shutdown(&mut self, closure_reason: ClosureReason) -> ShutdownResult {
-		self.context.force_shutdown(&self.funding, closure_reason)
+		let splice_funding_failed =
+			if matches!(self.context.channel_state, ChannelState::ChannelReady(_)) {
+				if self.should_reset_pending_splice_state() {
+					self.reset_pending_splice_state()
+				} else {
+					match self.quiescent_action.take() {
+						Some(QuiescentAction::Splice(instructions)) => {
+							self.context.channel_state.clear_awaiting_quiescence();
+							let (inputs, outputs) =
+								instructions.into_contributed_inputs_and_outputs();
+							Some(SpliceFundingFailed {
+								funding_txo: None,
+								channel_type: None,
+								contributed_inputs: inputs,
+								contributed_outputs: outputs,
+							})
+						},
+						#[cfg(any(test, fuzzing))]
+						Some(quiescent_action) => {
+							self.quiescent_action = Some(quiescent_action);
+							None
+						},
+						None => None,
+					}
+				}
+			} else {
+				None
+			};
+
+		let mut shutdown_result = self.context.force_shutdown(&self.funding, closure_reason);
+		shutdown_result.splice_funding_failed = splice_funding_failed;
+		shutdown_result
 	}
 
 	fn interactive_tx_constructor_mut(&mut self) -> Option<&mut InteractiveTxConstructor> {
@@ -10372,6 +10416,7 @@ where
 			is_manual_broadcast: self.context.is_manual_broadcast,
 			channel_funding_txo: self.funding.get_funding_txo(),
 			last_local_balance_msat: self.funding.value_to_self_msat,
+			splice_funding_failed: None,
 		}
 	}
 

lightning/src/ln/channelmanager.rs

@@ -4536,6 +4536,18 @@ where
 				last_local_balance_msat: Some(shutdown_res.last_local_balance_msat),
 			}, None));
 
+			if let Some(splice_funding_failed) = shutdown_res.splice_funding_failed.take() {
+				pending_events.push_back((events::Event::SpliceFailed {
+					channel_id: shutdown_res.channel_id,
+					counterparty_node_id: shutdown_res.counterparty_node_id,
+					user_channel_id: shutdown_res.user_channel_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));
+			}
+
 			if let Some(transaction) = shutdown_res.unbroadcasted_funding_tx {
 				let funding_info = if shutdown_res.is_manual_broadcast {
 					FundingInfo::OutPoint {

lightning/src/ln/functional_test_utils.rs

@@ -2151,6 +2151,7 @@ pub struct ExpectedCloseEvent {
 	pub channel_id: Option<ChannelId>,
 	pub counterparty_node_id: Option<PublicKey>,
 	pub discard_funding: bool,
+	pub splice_failed: bool,
 	pub reason: Option<ClosureReason>,
 	pub channel_funding_txo: Option<OutPoint>,
 	pub user_channel_id: Option<u128>,
@@ -2165,6 +2166,7 @@ impl ExpectedCloseEvent {
 			channel_id: Some(channel_id),
 			counterparty_node_id: None,
 			discard_funding,
+			splice_failed: false,
 			reason: Some(reason),
 			channel_funding_txo: None,
 			user_channel_id: None,
@@ -2176,8 +2178,14 @@ impl ExpectedCloseEvent {
 pub fn check_closed_events(node: &Node, expected_close_events: &[ExpectedCloseEvent]) {
 	let closed_events_count = expected_close_events.len();
 	let discard_events_count = expected_close_events.iter().filter(|e| e.discard_funding).count();
+	let splice_events_count = expected_close_events.iter().filter(|e| e.splice_failed).count();
 	let events = node.node.get_and_clear_pending_events();
-	assert_eq!(events.len(), closed_events_count + discard_events_count, "{:?}", events);
+	assert_eq!(
+		events.len(),
+		closed_events_count + discard_events_count + splice_events_count,
+		"{:?}",
+		events
+	);
 	for expected_event in expected_close_events {
 		assert!(events.iter().any(|e| matches!(
 			e,
@@ -2207,6 +2215,10 @@ pub fn check_closed_events(node: &Node, expected_close_events: &[ExpectedCloseEv
 		events.iter().filter(|e| matches!(e, Event::DiscardFunding { .. },)).count(),
 		discard_events_count
 	);
+	assert_eq!(
+		events.iter().filter(|e| matches!(e, Event::SpliceFailed { .. },)).count(),
+		splice_events_count
+	);
 }
 
 /// Check that a channel's closing channel events has been issued
@@ -2228,6 +2240,7 @@ pub fn check_closed_event(
 			channel_id: None,
 			counterparty_node_id: Some(*node_id),
 			discard_funding: is_check_discard_funding,
+			splice_failed: false,
 			reason: Some(expected_reason.clone()),
 			channel_funding_txo: None,
 			user_channel_id: None,

lightning/src/ln/monitor_tests.rs

@@ -1467,6 +1467,7 @@ fn do_test_revoked_counterparty_commitment_balances(keyed_anchors: bool, p2a_anc
 		channel_id: Some(chan_id),
 		counterparty_node_id: Some(nodes[0].node.get_our_node_id()),
 		discard_funding: false,
+		splice_failed: false,
 		reason: None, // Could be due to any HTLC timing out, so don't bother checking
 		channel_funding_txo: None,
 		user_channel_id: None,

lightning/src/ln/reorg_tests.rs

@@ -504,6 +504,7 @@ fn test_set_outpoints_partial_claiming() {
 		channel_id: Some(chan.2),
 		counterparty_node_id: Some(nodes[0].node.get_our_node_id()),
 		discard_funding: false,
+		splice_failed: false,
 		reason: None, // Could be due to either HTLC timing out, so don't bother checking
 		channel_funding_txo: None,
 		user_channel_id: None,

lightning/src/ln/shutdown_tests.rs

@@ -636,6 +636,7 @@ fn do_htlc_fail_async_shutdown(blinded_recipient: bool) {
 		channel_id: None,
 		counterparty_node_id: Some(node_a_id),
 		discard_funding: false,
+		splice_failed: false,
 		reason: Some(ClosureReason::LocallyInitiatedCooperativeClosure),
 		channel_funding_txo: None,
 		user_channel_id: None,
@@ -645,6 +646,7 @@ fn do_htlc_fail_async_shutdown(blinded_recipient: bool) {
 		channel_id: None,
 		counterparty_node_id: Some(node_c_id),
 		discard_funding: false,
+		splice_failed: false,
 		reason: Some(ClosureReason::CounterpartyInitiatedCooperativeClosure),
 		channel_funding_txo: None,
 		user_channel_id: None,

lightning/src/ln/splicing_tests.rs

@@ -1341,3 +1341,114 @@ fn fail_splice_on_tx_abort() {
 	let tx_abort = get_event_msg!(initiator, MessageSendEvent::SendTxAbort, node_id_acceptor);
 	acceptor.node.handle_tx_abort(node_id_initiator, &tx_abort);
 }
+
+#[test]
+fn fail_splice_on_channel_close() {
+	let chanmon_cfgs = create_chanmon_cfgs(2);
+	let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
+	let config = test_default_anchors_channel_config();
+	let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[Some(config.clone()), Some(config)]);
+	let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
+
+	let initiator = &nodes[0];
+	let acceptor = &nodes[1];
+
+	let _node_id_initiator = initiator.node.get_our_node_id();
+	let node_id_acceptor = acceptor.node.get_our_node_id();
+
+	let initial_channel_capacity = 100_000;
+	let (_, _, channel_id, _) =
+		create_announced_chan_between_nodes_with_value(&nodes, 0, 1, initial_channel_capacity, 0);
+
+	let coinbase_tx = provide_anchor_reserves(&nodes);
+	let splice_in_amount = initial_channel_capacity / 2;
+	let contribution = SpliceContribution::SpliceIn {
+		value: Amount::from_sat(splice_in_amount),
+		inputs: vec![FundingTxInput::new_p2wpkh(coinbase_tx, 0).unwrap()],
+		change_script: Some(nodes[0].wallet_source.get_change_script().unwrap()),
+	};
+
+	// Close the channel before completion of interactive-tx construction.
+	let _ = complete_splice_handshake(initiator, acceptor, channel_id, contribution.clone());
+	let _tx_add_input =
+		get_event_msg!(initiator, MessageSendEvent::SendTxAddInput, node_id_acceptor);
+
+	initiator
+		.node
+		.force_close_broadcasting_latest_txn(&channel_id, &node_id_acceptor, "test".to_owned())
+		.unwrap();
+	handle_bump_events(initiator, true, 0);
+	check_closed_events(
+		&nodes[0],
+		&[ExpectedCloseEvent {
+			channel_id: Some(channel_id),
+			discard_funding: false,
+			splice_failed: true,
+			channel_funding_txo: None,
+			user_channel_id: Some(42),
+			..Default::default()
+		}],
+	);
+	check_closed_broadcast(&nodes[0], 1, true);
+	check_added_monitors(&nodes[0], 1);
+}
+
+#[test]
+fn fail_quiescent_action_on_channel_close() {
+	let chanmon_cfgs = create_chanmon_cfgs(2);
+	let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
+	let config = test_default_anchors_channel_config();
+	let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[Some(config.clone()), Some(config)]);
+	let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
+
+	let initiator = &nodes[0];
+	let acceptor = &nodes[1];
+
+	let _node_id_initiator = initiator.node.get_our_node_id();
+	let node_id_acceptor = acceptor.node.get_our_node_id();
+
+	let initial_channel_capacity = 100_000;
+	let (_, _, channel_id, _) =
+		create_announced_chan_between_nodes_with_value(&nodes, 0, 1, initial_channel_capacity, 0);
+
+	let coinbase_tx = provide_anchor_reserves(&nodes);
+	let splice_in_amount = initial_channel_capacity / 2;
+	let contribution = SpliceContribution::SpliceIn {
+		value: Amount::from_sat(splice_in_amount),
+		inputs: vec![FundingTxInput::new_p2wpkh(coinbase_tx, 0).unwrap()],
+		change_script: Some(nodes[0].wallet_source.get_change_script().unwrap()),
+	};
+
+	// Close the channel before completion of STFU handshake.
+	initiator
+		.node
+		.splice_channel(
+			&channel_id,
+			&node_id_acceptor,
+			contribution,
+			FEERATE_FLOOR_SATS_PER_KW,
+			None,
+		)
+		.unwrap();
+
+	let _stfu_init = get_event_msg!(initiator, MessageSendEvent::SendStfu, node_id_acceptor);
+
+	initiator
+		.node
+		.force_close_broadcasting_latest_txn(&channel_id, &node_id_acceptor, "test".to_owned())
+		.unwrap();
+	handle_bump_events(initiator, true, 0);
+	check_closed_events(
+		&nodes[0],
+		&[ExpectedCloseEvent {
+			channel_id: Some(channel_id),
+			discard_funding: false,
+			splice_failed: true,
+			channel_funding_txo: None,
+			user_channel_id: Some(42),
+			..Default::default()
+		}],
+	);
+	check_closed_broadcast(&nodes[0], 1, true);
+	check_added_monitors(&nodes[0], 1);
+}