Hold peer lock when pushing to decode_update_adds

This avoids race conditions where we're unable to properly update an HTLC's
state because we need to update its state in the ChannelManager, but the HTLC
is stuck in transit from the Channel to
ChannelManager::decode_update_add_htlcs. Now the HTLC will atomically go from
the Channel to the ChannelManager decode queue under the same lock.

Author: valentinewallace

lightning/src/ln/channelmanager.rs

@@ -1516,7 +1516,6 @@ enum PostMonitorUpdateChanResume {
 		unbroadcasted_batch_funding_txid: Option<Txid>,
 		update_actions: Vec<MonitorUpdateCompletionAction>,
 		htlc_forwards: Vec<PendingAddHTLCInfo>,
-		decode_update_add_htlcs: Option<(u64, Vec<msgs::UpdateAddHTLC>)>,
 		finalized_claimed_htlcs: Vec<(HTLCSource, Option<AttributionData>)>,
 		failed_htlcs: Vec<(HTLCSource, PaymentHash, HTLCFailReason)>,
 		committed_outbound_htlc_sources: Vec<(HTLCPreviousHopData, u64)>,
@@ -10116,7 +10115,6 @@ This indicates a bug inside LDK. Please report this error at https://github.com/
 		&self, channel_id: ChannelId, counterparty_node_id: PublicKey, funding_txo: OutPoint,
 		user_channel_id: u128, unbroadcasted_batch_funding_txid: Option<Txid>,
 		update_actions: Vec<MonitorUpdateCompletionAction>, htlc_forwards: Vec<PendingAddHTLCInfo>,
-		decode_update_add_htlcs: Option<(u64, Vec<msgs::UpdateAddHTLC>)>,
 		finalized_claimed_htlcs: Vec<(HTLCSource, Option<AttributionData>)>,
 		failed_htlcs: Vec<(HTLCSource, PaymentHash, HTLCFailReason)>,
 		committed_outbound_htlc_sources: Vec<(HTLCPreviousHopData, u64)>,
@@ -10177,9 +10175,6 @@ This indicates a bug inside LDK. Please report this error at https://github.com/
 		self.handle_monitor_update_completion_actions(update_actions);
 
 		self.forward_htlcs(htlc_forwards);
-		if let Some(decode) = decode_update_add_htlcs {
-			self.push_decode_update_add_htlcs(decode);
-		}
 		self.finalize_claims(finalized_claimed_htlcs);
 		for failure in failed_htlcs {
 			let failure_type = failure.0.failure_type(counterparty_node_id, channel_id);
@@ -10667,6 +10662,10 @@ This indicates a bug inside LDK. Please report this error at https://github.com/
 				pending_msg_events.push(upd);
 			}
 
+			if let Some(update_adds) = decode_update_add_htlcs {
+				self.push_decode_update_add_htlcs(update_adds);
+			}
+
 			let unbroadcasted_batch_funding_txid =
 				chan.context.unbroadcasted_batch_funding_txid(&chan.funding);
 
@@ -10678,7 +10677,6 @@ This indicates a bug inside LDK. Please report this error at https://github.com/
 				unbroadcasted_batch_funding_txid,
 				update_actions,
 				htlc_forwards,
-				decode_update_add_htlcs,
 				finalized_claimed_htlcs: updates.finalized_claimed_htlcs,
 				failed_htlcs: updates.failed_htlcs,
 				committed_outbound_htlc_sources: updates.committed_outbound_htlc_sources,
@@ -10780,7 +10778,6 @@ This indicates a bug inside LDK. Please report this error at https://github.com/
 				unbroadcasted_batch_funding_txid,
 				update_actions,
 				htlc_forwards,
-				decode_update_add_htlcs,
 				finalized_claimed_htlcs,
 				failed_htlcs,
 				committed_outbound_htlc_sources,
@@ -10793,7 +10790,6 @@ This indicates a bug inside LDK. Please report this error at https://github.com/
 					unbroadcasted_batch_funding_txid,
 					update_actions,
 					htlc_forwards,
-					decode_update_add_htlcs,
 					finalized_claimed_htlcs,
 					failed_htlcs,
 					committed_outbound_htlc_sources,
@@ -17920,12 +17916,6 @@ impl<
 			}
 		}
 
-		let mut decode_update_add_htlcs_opt = None;
-		let decode_update_add_htlcs = self.decode_update_add_htlcs.lock().unwrap();
-		if !decode_update_add_htlcs.is_empty() {
-			decode_update_add_htlcs_opt = Some(decode_update_add_htlcs);
-		}
-
 		let claimable_payments = self.claimable_payments.lock().unwrap();
 		let pending_outbound_payments = self.pending_outbound_payments.pending_outbound_payments.lock().unwrap();
 
@@ -17951,6 +17941,14 @@ impl<
 			peer_states.push(peer_state_mutex.unsafe_well_ordered_double_lock_self());
 		}
 
+		let mut decode_update_add_htlcs_opt = None;
+		{
+			let decode_update_add_htlcs = self.decode_update_add_htlcs.lock().unwrap();
+			if !decode_update_add_htlcs.is_empty() {
+				decode_update_add_htlcs_opt = Some(decode_update_add_htlcs);
+			}
+		}
+
 		let mut peer_storage_dir: Vec<(&PublicKey, &Vec<u8>)> = Vec::new();
 
 		(serializable_peer_count).write(writer)?;