Use channel ID over funding outpoint to track monitors in ChainMonitor

Once dual funding/splicing is supported, channels will no longer
maintain their original funding outpoint. Ideally, we identify
`ChannelMonitor`s with a stable identifier, such as the channel ID,
which is fixed throughout the channel's lifetime.

This commit replaces the use of funding outpoints as the key to the
monitor index with the channel ID. Note that this is strictly done to
the in-memory state; it does not change how we track monitors within
their persisted state, they are still keyed by their funding outpoint
there. Addressing that is left for follow-up work.

Author: wpaulino

fuzz/src/chanmon_consistency.rs

@@ -198,7 +198,7 @@ struct TestChainMonitor {
 			Arc<TestPersister>,
 		>,
 	>,
-	pub latest_monitors: Mutex<HashMap<OutPoint, LatestMonitorState>>,
+	pub latest_monitors: Mutex<HashMap<ChannelId, LatestMonitorState>>,
 }
 impl TestChainMonitor {
 	pub fn new(
@@ -222,12 +222,12 @@ impl TestChainMonitor {
 }
 impl chain::Watch<TestChannelSigner> for TestChainMonitor {
 	fn watch_channel(
-		&self, funding_txo: OutPoint, monitor: channelmonitor::ChannelMonitor<TestChannelSigner>,
+		&self, channel_id: ChannelId, monitor: channelmonitor::ChannelMonitor<TestChannelSigner>,
 	) -> Result<chain::ChannelMonitorUpdateStatus, ()> {
 		let mut ser = VecWriter(Vec::new());
 		monitor.write(&mut ser).unwrap();
 		let monitor_id = monitor.get_latest_update_id();
-		let res = self.chain_monitor.watch_channel(funding_txo, monitor);
+		let res = self.chain_monitor.watch_channel(channel_id, monitor);
 		let state = match res {
 			Ok(chain::ChannelMonitorUpdateStatus::Completed) => LatestMonitorState {
 				persisted_monitor_id: monitor_id,
@@ -240,17 +240,17 @@ impl chain::Watch<TestChannelSigner> for TestChainMonitor {
 			Ok(chain::ChannelMonitorUpdateStatus::UnrecoverableError) => panic!(),
 			Err(()) => panic!(),
 		};
-		if self.latest_monitors.lock().unwrap().insert(funding_txo, state).is_some() {
+		if self.latest_monitors.lock().unwrap().insert(channel_id, state).is_some() {
 			panic!("Already had monitor pre-watch_channel");
 		}
 		res
 	}
 
 	fn update_channel(
-		&self, funding_txo: OutPoint, update: &channelmonitor::ChannelMonitorUpdate,
+		&self, channel_id: ChannelId, update: &channelmonitor::ChannelMonitorUpdate,
 	) -> chain::ChannelMonitorUpdateStatus {
 		let mut map_lock = self.latest_monitors.lock().unwrap();
-		let map_entry = map_lock.get_mut(&funding_txo).expect("Didn't have monitor on update call");
+		let map_entry = map_lock.get_mut(&channel_id).expect("Didn't have monitor on update call");
 		let latest_monitor_data = map_entry
 			.pending_monitors
 			.last()
@@ -274,7 +274,7 @@ impl chain::Watch<TestChannelSigner> for TestChainMonitor {
 			.unwrap();
 		let mut ser = VecWriter(Vec::new());
 		deserialized_monitor.write(&mut ser).unwrap();
-		let res = self.chain_monitor.update_channel(funding_txo, update);
+		let res = self.chain_monitor.update_channel(channel_id, update);
 		match res {
 			chain::ChannelMonitorUpdateStatus::Completed => {
 				map_entry.persisted_monitor_id = update.update_id;
@@ -763,9 +763,9 @@ pub fn do_test<Out: Output>(data: &[u8], underlying_out: Out, anchors: bool) {
 					.1,
 				chain_monitor.clone(),
 			);
-			for (funding_txo, mon) in monitors.drain() {
+			for (channel_id, mon) in monitors.drain() {
 				assert_eq!(
-					chain_monitor.chain_monitor.watch_channel(funding_txo, mon),
+					chain_monitor.chain_monitor.watch_channel(channel_id, mon),
 					Ok(ChannelMonitorUpdateStatus::Completed)
 				);
 			}
@@ -836,7 +836,6 @@ pub fn do_test<Out: Output>(data: &[u8], underlying_out: Out, anchors: bool) {
 			};
 
 			$source.handle_accept_channel($dest.get_our_node_id(), &accept_channel);
-			let funding_output;
 			{
 				let mut events = $source.get_and_clear_pending_events();
 				assert_eq!(events.len(), 1);
@@ -856,7 +855,6 @@ pub fn do_test<Out: Output>(data: &[u8], underlying_out: Out, anchors: bool) {
 							script_pubkey: output_script,
 						}],
 					};
-					funding_output = OutPoint { txid: tx.compute_txid(), index: 0 };
 					$source
 						.funding_transaction_generated(
 							temporary_channel_id,
@@ -901,13 +899,19 @@ pub fn do_test<Out: Output>(data: &[u8], underlying_out: Out, anchors: bool) {
 			$source.handle_funding_signed($dest.get_our_node_id(), &funding_signed);
 			let events = $source.get_and_clear_pending_events();
 			assert_eq!(events.len(), 1);
-			if let events::Event::ChannelPending { ref counterparty_node_id, .. } = events[0] {
+			let channel_id = if let events::Event::ChannelPending {
+				ref counterparty_node_id,
+				ref channel_id,
+				..
+			} = events[0]
+			{
 				assert_eq!(counterparty_node_id, &$dest.get_our_node_id());
+				channel_id.clone()
 			} else {
 				panic!("Wrong event type");
-			}
+			};
 
-			funding_output
+			channel_id
 		}};
 	}
 
@@ -974,8 +978,8 @@ pub fn do_test<Out: Output>(data: &[u8], underlying_out: Out, anchors: bool) {
 
 	let mut nodes = [node_a, node_b, node_c];
 
-	let chan_1_funding = make_channel!(nodes[0], nodes[1], keys_manager_b, 0);
-	let chan_2_funding = make_channel!(nodes[1], nodes[2], keys_manager_c, 1);
+	let chan_1_id = make_channel!(nodes[0], nodes[1], keys_manager_b, 0);
+	let chan_2_id = make_channel!(nodes[1], nodes[2], keys_manager_c, 1);
 
 	for node in nodes.iter() {
 		confirm_txn!(node);
@@ -1374,14 +1378,14 @@ pub fn do_test<Out: Output>(data: &[u8], underlying_out: Out, anchors: bool) {
 				}
 			};
 
-		let complete_all_monitor_updates = |monitor: &Arc<TestChainMonitor>, chan_funding| {
-			if let Some(state) = monitor.latest_monitors.lock().unwrap().get_mut(chan_funding) {
+		let complete_all_monitor_updates = |monitor: &Arc<TestChainMonitor>, chan_id| {
+			if let Some(state) = monitor.latest_monitors.lock().unwrap().get_mut(chan_id) {
 				assert!(
 					state.pending_monitors.windows(2).all(|pair| pair[0].0 < pair[1].0),
 					"updates should be sorted by id"
 				);
 				for (id, data) in state.pending_monitors.drain(..) {
-					monitor.chain_monitor.channel_monitor_updated(*chan_funding, id).unwrap();
+					monitor.chain_monitor.channel_monitor_updated(*chan_id, id).unwrap();
 					if id > state.persisted_monitor_id {
 						state.persisted_monitor_id = id;
 						state.persisted_monitor = data;
@@ -1421,10 +1425,10 @@ pub fn do_test<Out: Output>(data: &[u8], underlying_out: Out, anchors: bool) {
 					ChannelMonitorUpdateStatus::Completed
 			},
 
-			0x08 => complete_all_monitor_updates(&monitor_a, &chan_1_funding),
-			0x09 => complete_all_monitor_updates(&monitor_b, &chan_1_funding),
-			0x0a => complete_all_monitor_updates(&monitor_b, &chan_2_funding),
-			0x0b => complete_all_monitor_updates(&monitor_c, &chan_2_funding),
+			0x08 => complete_all_monitor_updates(&monitor_a, &chan_1_id),
+			0x09 => complete_all_monitor_updates(&monitor_b, &chan_1_id),
+			0x0a => complete_all_monitor_updates(&monitor_b, &chan_2_id),
+			0x0b => complete_all_monitor_updates(&monitor_c, &chan_2_id),
 
 			0x0c => {
 				if !chan_a_disconnected {
@@ -1694,21 +1698,21 @@ pub fn do_test<Out: Output>(data: &[u8], underlying_out: Out, anchors: bool) {
 				nodes[2].maybe_update_chan_fees();
 			},
 
-			0xf0 => complete_monitor_update(&monitor_a, &chan_1_funding, &complete_first),
-			0xf1 => complete_monitor_update(&monitor_a, &chan_1_funding, &complete_second),
-			0xf2 => complete_monitor_update(&monitor_a, &chan_1_funding, &Vec::pop),
+			0xf0 => complete_monitor_update(&monitor_a, &chan_1_id, &complete_first),
+			0xf1 => complete_monitor_update(&monitor_a, &chan_1_id, &complete_second),
+			0xf2 => complete_monitor_update(&monitor_a, &chan_1_id, &Vec::pop),
 
-			0xf4 => complete_monitor_update(&monitor_b, &chan_1_funding, &complete_first),
-			0xf5 => complete_monitor_update(&monitor_b, &chan_1_funding, &complete_second),
-			0xf6 => complete_monitor_update(&monitor_b, &chan_1_funding, &Vec::pop),
+			0xf4 => complete_monitor_update(&monitor_b, &chan_1_id, &complete_first),
+			0xf5 => complete_monitor_update(&monitor_b, &chan_1_id, &complete_second),
+			0xf6 => complete_monitor_update(&monitor_b, &chan_1_id, &Vec::pop),
 
-			0xf8 => complete_monitor_update(&monitor_b, &chan_2_funding, &complete_first),
-			0xf9 => complete_monitor_update(&monitor_b, &chan_2_funding, &complete_second),
-			0xfa => complete_monitor_update(&monitor_b, &chan_2_funding, &Vec::pop),
+			0xf8 => complete_monitor_update(&monitor_b, &chan_2_id, &complete_first),
+			0xf9 => complete_monitor_update(&monitor_b, &chan_2_id, &complete_second),
+			0xfa => complete_monitor_update(&monitor_b, &chan_2_id, &Vec::pop),
 
-			0xfc => complete_monitor_update(&monitor_c, &chan_2_funding, &complete_first),
-			0xfd => complete_monitor_update(&monitor_c, &chan_2_funding, &complete_second),
-			0xfe => complete_monitor_update(&monitor_c, &chan_2_funding, &Vec::pop),
+			0xfc => complete_monitor_update(&monitor_c, &chan_2_id, &complete_first),
+			0xfd => complete_monitor_update(&monitor_c, &chan_2_id, &complete_second),
+			0xfe => complete_monitor_update(&monitor_c, &chan_2_id, &Vec::pop),
 
 			0xff => {
 				// Test that no channel is in a stuck state where neither party can send funds even
@@ -1722,10 +1726,10 @@ pub fn do_test<Out: Output>(data: &[u8], underlying_out: Out, anchors: bool) {
 				*monitor_c.persister.update_ret.lock().unwrap() =
 					ChannelMonitorUpdateStatus::Completed;
 
-				complete_all_monitor_updates(&monitor_a, &chan_1_funding);
-				complete_all_monitor_updates(&monitor_b, &chan_1_funding);
-				complete_all_monitor_updates(&monitor_b, &chan_2_funding);
-				complete_all_monitor_updates(&monitor_c, &chan_2_funding);
+				complete_all_monitor_updates(&monitor_a, &chan_1_id);
+				complete_all_monitor_updates(&monitor_b, &chan_1_id);
+				complete_all_monitor_updates(&monitor_b, &chan_2_id);
+				complete_all_monitor_updates(&monitor_c, &chan_2_id);
 
 				// Next, make sure peers are all connected to each other
 				if chan_a_disconnected {

lightning-block-sync/src/init.rs

@@ -125,7 +125,7 @@ where
 ///
 /// 	// Allow the chain monitor to watch any channels.
 /// 	let monitor = monitor_listener.0;
-/// 	chain_monitor.watch_channel(monitor.get_funding_txo().0, monitor);
+/// 	chain_monitor.watch_channel(monitor.channel_id(), monitor);
 ///
 /// 	// Create an SPV client to notify the chain monitor and channel manager of block events.
 /// 	let chain_poller = poll::ChainPoller::new(block_source, Network::Bitcoin);