fixup! fixup! fixup! Enable spliting lightning channel

I think we might need to update the `ChannelTransactionParameters` in
the `OnchainTxHandler` when we split the channel. It seems necessary
in general and it has become mandatory now that we have a
`debug_assert_eq` checking the commitment TXIDs when handling a
`ChannelMonitorUpdate` in the `ChannelMonitor`.

Author: luckysori

lightning/src/chain/channelmonitor.rs

@@ -1292,12 +1292,20 @@ impl<Signer: WriteableEcdsaChannelSigner> ChannelMonitor<Signer> {
 		if let Some(original) = inner.original_funding_info.as_ref() {
 			if fund_outpoint == original.0 {
 				inner.original_funding_info = None;
+				inner.onchain_tx_handler.channel_transaction_parameters.original_funding_outpoint = None;
 			}
 		} else {
-			inner.original_funding_info = Some((inner.funding_info.0.clone(), inner.funding_info.1.clone()));
+			let original_funding_txo = inner.funding_info.0;
+			let original_funding_script_pubkey = &inner.funding_info.1;
+
+			inner.original_funding_info = Some((original_funding_txo, original_funding_script_pubkey.clone()));
+			inner.onchain_tx_handler.channel_transaction_parameters.original_funding_outpoint = Some(original_funding_txo);
 		}
 		inner.outputs_to_watch.insert(fund_outpoint.txid, vec![(fund_outpoint.index as u32, script.clone())]);
+
 		inner.funding_info = (fund_outpoint, script.clone());
+		inner.onchain_tx_handler.channel_transaction_parameters.funding_outpoint = Some(fund_outpoint);
+
 		inner.channel_value_satoshis = channel_value_satoshis;
 		inner.onchain_tx_handler.signer.set_channel_value_satoshis(channel_value_satoshis);
 		script

lightning/src/ln/channel.rs

@@ -1076,8 +1076,7 @@ impl<SP: Deref> ChannelContext<SP> where SP::Target: SignerProvider  {
 		self.channel_transaction_parameters.original_funding_outpoint.or(self.get_funding_txo())
 	}
 
-	/// Set the funding output and value of the channel, returning a `ChannelMonitorUpdate`
-	/// containing a commitment for the new funding output if requested.
+	/// Set the funding output and value of the channel.
 	fn set_funding_outpoint(&mut self, funding_outpoint: &OutPoint, channel_value_satoshis: u64, own_balance: u64)
 	{
 		self.channel_value_satoshis = channel_value_satoshis;

lightning/src/ln/channelmanager.rs

@@ -2720,6 +2720,10 @@ where
 		let chan = channel_lock.get_channel();
 
 		let original_funding_txo = chan.context.get_original_funding_txo().unwrap();
+		if ChannelMonitorUpdateStatus::Completed != self.chain_monitor.update_channel_funding_txo(chan.context.get_original_funding_txo().unwrap(), *funding_outpoint, channel_value_satoshis) {
+			return Err(APIError::APIMisuseError { err: "Could not update channel funding transaction.".to_string() });
+		}
+
 		let monitor_update = chan.set_funding_outpoint(funding_outpoint, channel_value_satoshis, own_balance, true, &self.logger);
 		if let Some(monitor_update) = &monitor_update {
 			let update_res = self.chain_monitor.update_channel(original_funding_txo, monitor_update);
@@ -2728,10 +2732,6 @@ where
 			}
 		}
 
-		if ChannelMonitorUpdateStatus::Completed != self.chain_monitor.update_channel_funding_txo(chan.context.get_original_funding_txo().unwrap(), *funding_outpoint, channel_value_satoshis) {
-			return Err(APIError::APIMisuseError { err: "Could not update channel funding transaction.".to_string() });
-		}
-
 		let res = chan.monitor_updating_restored(&self.logger, &self.node_signer, self.genesis_hash, &self.default_configuration, self.best_block.read().unwrap().height());
 
 		let commit_tx_number = chan.get_cur_counterparty_commitment_transaction_number();