f handle monitor to use not always being the last

Author: TheBlueMatt

lightning/src/ln/channelmanager.rs

@@ -1910,13 +1910,15 @@ macro_rules! handle_new_monitor_update {
 		let update_id = $update.update_id;
 		let in_flight_updates = $peer_state.in_flight_monitor_updates.entry($funding_txo)
 			.or_insert_with(Vec::new);
-		if !in_flight_updates.contains(&$update) {
-			// During startup, we push monitor updates as background events through to here in
-			// order to replay updates that were in-flight when we shut down. Thus, we have to
-			// filter for uniqueness here.
-			in_flight_updates.push($update);
-		}
-		let update_res = $self.chain_monitor.update_channel($funding_txo, in_flight_updates.last().unwrap());
+		// During startup, we push monitor updates as background events through to here in
+		// order to replay updates that were in-flight when we shut down. Thus, we have to
+		// filter for uniqueness here.
+		let idx = in_flight_updates.iter().position(|upd| upd == &$update)
+			.unwrap_or_else(|| {
+				in_flight_updates.push($update);
+				in_flight_updates.len() - 1
+			});
+		let update_res = $self.chain_monitor.update_channel($funding_txo, &in_flight_updates[idx]);
 		handle_new_monitor_update!($self, update_res, $peer_state_lock, $peer_state,
 			$per_peer_state_lock, $chan, _internal, $remove,
 			{