Don't rebroadcast closing TX upon restart

While we don't rebroadcast the latest holder commitment transactions in
`ChannelMonitor::update_monitor()` anymore if we had previously seen a
closing tx on-chain, we still do so upon restarting / deserlization of
`ChannelManager`

With this change, we now also refrain from rebroadcasting upon
restarting.

Author: tnull

lightning/src/chain/channelmonitor.rs

@@ -1236,6 +1236,11 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitor<Signer> {
 		self.inner.lock().unwrap().get_funding_txo().clone()
 	}
 
+	/// Gets whether we've seen a confirmed transaction spending the funding output.
+	pub(crate) fn detected_funding_spend(&self) -> bool {
+		self.inner.lock().unwrap().detected_funding_spend()
+	}
+
 	/// Gets a list of txids, with their output scripts (in the order they appear in the
 	/// transaction), which we must learn about spends of via block_connected().
 	pub fn get_outputs_to_watch(&self) -> Vec<(Txid, Vec<(u32, Script)>)> {
@@ -2275,12 +2280,7 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitorImpl<Signer> {
 						// There's no need to broadcast our commitment transaction if we've seen one
 						// confirmed (even with 1 confirmation) as it'll be rejected as
 						// duplicate/conflicting.
-						let detected_funding_spend = self.funding_spend_confirmed.is_some() ||
-							self.onchain_events_awaiting_threshold_conf.iter().find(|event| match event.event {
-								OnchainEvent::FundingSpendConfirmation { .. } => true,
-								_ => false,
-							}).is_some();
-						if detected_funding_spend {
+						if self.detected_funding_spend() {
 							continue;
 						}
 						self.broadcast_latest_holder_commitment_txn(broadcaster, logger);
@@ -2338,6 +2338,15 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitorImpl<Signer> {
 		&self.funding_info
 	}
 
+	pub fn detected_funding_spend(&self) -> bool {
+			self.funding_spend_confirmed.is_some() ||
+			self.onchain_events_awaiting_threshold_conf
+				.iter().find(|event| match event.event {
+					OnchainEvent::FundingSpendConfirmation { .. } => true,
+					_ => false,
+			}).is_some()
+	}
+
 	pub fn get_outputs_to_watch(&self) -> &HashMap<Txid, Vec<(u32, Script)>> {
 		// If we've detected a counterparty commitment tx on chain, we must include it in the set
 		// of outputs to watch for spends of, otherwise we're likely to lose user funds. Because

lightning/src/ln/channelmanager.rs

@@ -7208,7 +7208,10 @@ where
 		}
 
 		for (funding_txo, monitor) in args.channel_monitors.iter_mut() {
-			if !funding_txo_set.contains(funding_txo) {
+			// There's no need to broadcast our commitment transaction if we've seen one
+			// confirmed (even with 1 confirmation) as it'll be rejected as
+			// duplicate/conflicting.
+			if !funding_txo_set.contains(funding_txo) && !monitor.detected_funding_spend() {
 				log_info!(args.logger, "Broadcasting latest holder commitment transaction for closed channel {}", log_bytes!(funding_txo.to_channel_id()));
 				monitor.broadcast_latest_holder_commitment_txn(&args.tx_broadcaster, &args.logger);
 			}