f - handle closing signed while waiting on signer

Author: alecchendev

lightning/src/ln/channel.rs

@@ -6066,6 +6066,14 @@ impl<SP: Deref> Channel<SP> where
 		-> Result<(Option<msgs::ClosingSigned>, Option<Transaction>, Option<ShutdownResult>), ChannelError>
 		where F::Target: FeeEstimator, L::Target: Logger
 	{
+		if matches!(self.context.channel_state, ChannelState::ShutdownComplete) {
+			// During async signing, we may need to keep the channel around
+			// even after it's been fully closed, so that we can construct
+			// and sign the final transaction to send back to the peer.
+			// If they send us another closing_signed, we should act as
+			// if the channel has already been fully closed.
+			return Err(ChannelError::Warn(String::from("Remote end sent us a closing_signed after shutdown complete")));
+		}
 		if !self.context.channel_state.is_both_sides_shutdown() {
 			return Err(ChannelError::close("Remote end sent us a closing_signed before both sides provided a shutdown".to_owned()));
 		}

lightning/src/ln/channelmanager.rs

@@ -8544,7 +8544,9 @@ where
 											node_id: chan.context.get_counterparty_node_id(), msg,
 										});
 									}
-									debug_assert_eq!(shutdown_result_opt.is_some(), chan.is_shutdown());
+									if shutdown_result_opt.is_some() {
+										debug_assert!(chan.is_shutdown());
+									}
 									if let Some(shutdown_result) = shutdown_result_opt {
 										shutdown_results.push(shutdown_result);
 									}