Fix reconnect message order on remote updates while waiting on RAA

Author: TheBlueMatt

src/ln/channel.rs

@@ -296,6 +296,12 @@ pub(super) struct Channel {
 	cur_local_commitment_transaction_number: u64,
 	cur_remote_commitment_transaction_number: u64,
 	value_to_self_msat: u64, // Excluding all pending_htlcs, excluding fees
+	/// Upon receipt of a channel_reestablish we have to figure out whether to send a
+	/// revoke_and_ack first or a commitment update first. Generally, we prefer to send
+	/// revoke_and_ack first, but if we had a pending commitment update of our own waiting on a
+	/// remote revoke when we received the latest commitment update from the remote we have to make
+	/// sure that commitment update gets resent first.
+	received_commitment_while_awaiting_raa: bool,
 	pending_inbound_htlcs: Vec<InboundHTLCOutput>,
 	pending_outbound_htlcs: Vec<OutboundHTLCOutput>,
 	holding_cell_htlc_updates: Vec<HTLCUpdateAwaitingACK>,
@@ -492,6 +498,8 @@ impl Channel {
 			cur_local_commitment_transaction_number: INITIAL_COMMITMENT_NUMBER,
 			cur_remote_commitment_transaction_number: INITIAL_COMMITMENT_NUMBER,
 			value_to_self_msat: channel_value_satoshis * 1000 - push_msat,
+			received_commitment_while_awaiting_raa: false,
+
 			pending_inbound_htlcs: Vec::new(),
 			pending_outbound_htlcs: Vec::new(),
 			holding_cell_htlc_updates: Vec::new(),
@@ -647,6 +655,8 @@ impl Channel {
 			cur_local_commitment_transaction_number: INITIAL_COMMITMENT_NUMBER,
 			cur_remote_commitment_transaction_number: INITIAL_COMMITMENT_NUMBER,
 			value_to_self_msat: msg.push_msat,
+			received_commitment_while_awaiting_raa: false,
+
 			pending_inbound_htlcs: Vec::new(),
 			pending_outbound_htlcs: Vec::new(),
 			holding_cell_htlc_updates: Vec::new(),
@@ -1696,6 +1706,7 @@ impl Channel {
 
 		self.cur_local_commitment_transaction_number -= 1;
 		self.last_local_commitment_txn = new_local_commitment_txn;
+		self.received_commitment_while_awaiting_raa = (self.channel_state & (ChannelState::AwaitingRemoteRevoke as u32)) != 0;
 
 		let (our_commitment_signed, monitor_update) = if need_our_commitment && (self.channel_state & (ChannelState::AwaitingRemoteRevoke as u32)) == 0 {
 			// If we're AwaitingRemoteRevoke we can't send a new commitment here, but that's ok -
@@ -1831,6 +1842,7 @@ impl Channel {
 		self.their_prev_commitment_point = self.their_cur_commitment_point;
 		self.their_cur_commitment_point = Some(msg.next_per_commitment_point);
 		self.cur_remote_commitment_transaction_number -= 1;
+		self.received_commitment_while_awaiting_raa = false;
 
 		let mut to_forward_infos = Vec::new();
 		let mut revoked_htlcs = Vec::new();
@@ -2120,7 +2132,11 @@ impl Channel {
 			})
 		} else { None };
 
-		let order = RAACommitmentOrder::RevokeAndACKFirst;
+		let order = if self.received_commitment_while_awaiting_raa {
+			RAACommitmentOrder::CommitmentFirst
+		} else {
+			RAACommitmentOrder::RevokeAndACKFirst
+		};
 
 		if msg.next_local_commitment_number == our_next_remote_commitment_number {
 			if required_revoke.is_some() {