Use Channel::funding_txo instead of its channel_monitor.funding_txo

Currently Channel relies on its own internal channel_monitor copy
to keep track of funding_txo information, which is both a bit
awkward and not ideal if we want to get rid of the ChannelMonitor
copy in Channel.

Instead, just duplicate it (its small) and keep it directly in
Channel, allowing us to remove the (super awkward)
ChannelMonitor::unset_funding_txo().

Author: TheBlueMatt

lightning/src/chain/transaction.rs

@@ -39,6 +39,8 @@ impl OutPoint {
 	}
 }
 
+impl_writeable!(OutPoint, 0, { txid, index });
+
 #[cfg(test)]
 mod tests {
 	use chain::transaction::OutPoint;

lightning/src/ln/channel.rs

@@ -303,6 +303,8 @@ pub(super) struct Channel<ChanSigner: ChannelKeys> {
 
 	last_sent_closing_fee: Option<(u64, u64, Signature)>, // (feerate, fee, our_sig)
 
+	funding_txo: Option<OutPoint>,
+
 	/// The hash of the block in which the funding transaction reached our CONF_TARGET. We use this
 	/// to detect unconfirmation after a serialize-unserialize roundtrip where we may not see a full
 	/// series of block_connected/block_disconnected calls. Obviously this is not a guarantee as we
@@ -498,6 +500,7 @@ impl<ChanSigner: ChannelKeys> Channel<ChanSigner> {
 
 			last_sent_closing_fee: None,
 
+			funding_txo: None,
 			funding_tx_confirmed_in: None,
 			short_channel_id: None,
 			last_block_connected: Default::default(),
@@ -718,6 +721,7 @@ impl<ChanSigner: ChannelKeys> Channel<ChanSigner> {
 
 			last_sent_closing_fee: None,
 
+			funding_txo: None,
 			funding_tx_confirmed_in: None,
 			short_channel_id: None,
 			last_block_connected: Default::default(),
@@ -814,7 +818,7 @@ impl<ChanSigner: ChannelKeys> Channel<ChanSigner> {
 		let txins = {
 			let mut ins: Vec<TxIn> = Vec::new();
 			ins.push(TxIn {
-				previous_output: self.channel_monitor.get_funding_txo().unwrap().into_bitcoin_outpoint(),
+				previous_output: self.funding_txo.unwrap().into_bitcoin_outpoint(),
 				script_sig: Script::new(),
 				sequence: ((0x80 as u32) << 8*3) | ((obscured_commitment_transaction_number >> 3*8) as u32),
 				witness: Vec::new(),
@@ -1033,7 +1037,7 @@ impl<ChanSigner: ChannelKeys> Channel<ChanSigner> {
 		let txins = {
 			let mut ins: Vec<TxIn> = Vec::new();
 			ins.push(TxIn {
-				previous_output: self.channel_monitor.get_funding_txo().unwrap().into_bitcoin_outpoint(),
+				previous_output: self.funding_txo.unwrap().into_bitcoin_outpoint(),
 				script_sig: Script::new(),
 				sequence: 0xffffffff,
 				witness: Vec::new(),
@@ -1461,17 +1465,19 @@ impl<ChanSigner: ChannelKeys> Channel<ChanSigner> {
 		}
 
 		let funding_txo = OutPoint::new(msg.funding_txid, msg.funding_output_index);
-		let funding_txo_script = self.get_funding_redeemscript().to_v0_p2wsh();
-		self.channel_monitor.set_funding_info((funding_txo, funding_txo_script));
+		self.funding_txo = Some(funding_txo.clone());
 
 		let (remote_initial_commitment_tx, local_initial_commitment_tx, our_signature, local_keys) = match self.funding_created_signature(&msg.signature) {
 			Ok(res) => res,
 			Err(e) => {
-				self.channel_monitor.unset_funding_info();
+				self.funding_txo = None;
 				return Err(e);
 			}
 		};
 
+		let funding_txo_script = self.get_funding_redeemscript().to_v0_p2wsh();
+		self.channel_monitor.set_funding_info((funding_txo, funding_txo_script));
+
 		// Now that we're past error-generating stuff, update our local state:
 
 		self.channel_monitor.provide_latest_remote_commitment_tx_info(&remote_initial_commitment_tx, Vec::new(), self.cur_remote_commitment_transaction_number, self.their_cur_commitment_point.unwrap());
@@ -2825,7 +2831,7 @@ impl<ChanSigner: ChannelKeys> Channel<ChanSigner> {
 	/// Returns the funding_txo we either got from our peer, or were given by
 	/// get_outbound_funding_created.
 	pub fn get_funding_txo(&self) -> Option<OutPoint> {
-		self.channel_monitor.get_funding_txo()
+		self.funding_txo
 	}
 
 	/// Allowed in any state (including after shutdown)
@@ -3005,8 +3011,8 @@ impl<ChanSigner: ChannelKeys> Channel<ChanSigner> {
 		}
 		if non_shutdown_state & !(ChannelState::TheirFundingLocked as u32) == ChannelState::FundingSent as u32 {
 			for (ref tx, index_in_block) in txn_matched.iter().zip(indexes_of_txn_matched) {
-				if tx.txid() == self.channel_monitor.get_funding_txo().unwrap().txid {
-					let txo_idx = self.channel_monitor.get_funding_txo().unwrap().index as usize;
+				if tx.txid() == self.funding_txo.unwrap().txid {
+					let txo_idx = self.funding_txo.unwrap().index as usize;
 					if txo_idx >= tx.output.len() || tx.output[txo_idx].script_pubkey != self.get_funding_redeemscript().to_v0_p2wsh() ||
 							tx.output[txo_idx].value != self.channel_value_satoshis {
 						if self.channel_outbound {
@@ -3209,18 +3215,18 @@ impl<ChanSigner: ChannelKeys> Channel<ChanSigner> {
 			panic!("Should not have advanced channel commitment tx numbers prior to funding_created");
 		}
 
-		let funding_txo_script = self.get_funding_redeemscript().to_v0_p2wsh();
-		self.channel_monitor.set_funding_info((funding_txo, funding_txo_script));
-
+		self.funding_txo = Some(funding_txo.clone());
 		let (our_signature, commitment_tx) = match self.get_outbound_funding_created_signature() {
 			Ok(res) => res,
 			Err(e) => {
 				log_error!(self, "Got bad signatures: {:?}!", e);
-				self.channel_monitor.unset_funding_info();
+				self.funding_txo = None;
 				return Err(e);
 			}
 		};
 
+		let funding_txo_script = self.get_funding_redeemscript().to_v0_p2wsh();
+		self.channel_monitor.set_funding_info((funding_txo, funding_txo_script));
 		let temporary_channel_id = self.channel_id;
 
 		// Now that we're past error-generating stuff, update our local state:
@@ -3815,6 +3821,7 @@ impl<ChanSigner: ChannelKeys + Writeable> Writeable for Channel<ChanSigner> {
 			None => 0u8.write(writer)?,
 		}
 
+		write_option!(self.funding_txo);
 		write_option!(self.funding_tx_confirmed_in);
 		write_option!(self.short_channel_id);
 
@@ -3967,6 +3974,7 @@ impl<R : ::std::io::Read, ChanSigner: ChannelKeys + Readable<R>> ReadableArgs<R,
 			_ => return Err(DecodeError::InvalidValue),
 		};
 
+		let funding_txo = Readable::read(reader)?;
 		let funding_tx_confirmed_in = Readable::read(reader)?;
 		let short_channel_id = Readable::read(reader)?;
 
@@ -4043,6 +4051,7 @@ impl<R : ::std::io::Read, ChanSigner: ChannelKeys + Readable<R>> ReadableArgs<R,
 
 			last_sent_closing_fee,
 
+			funding_txo,
 			funding_tx_confirmed_in,
 			short_channel_id,
 			last_block_connected,
@@ -4183,7 +4192,7 @@ mod tests {
 		chan.our_dust_limit_satoshis = 546;
 
 		let funding_info = OutPoint::new(Sha256dHash::from_hex("8984484a580b825b9972d7adb15050b3ab624ccd731946b3eeddb92f4e7ef6be").unwrap(), 0);
-		chan.channel_monitor.set_funding_info((funding_info, Script::new()));
+		chan.funding_txo = Some(funding_info);
 
 		let their_pubkeys = ChannelPublicKeys {
 			funding_pubkey: public_from_secret_hex(&secp_ctx, "1552dfba4f6cf29a62a0af13c8d6981d36d0ef8d61ba10fb0fe90da7634d7e13"),

lightning/src/ln/channelmanager.rs

@@ -3318,7 +3318,7 @@ impl<'a, R : ::std::io::Read, ChanSigner: ChannelKeys + Readable<R>, M: Deref> R
 				return Err(DecodeError::InvalidValue);
 			}
 
-			let funding_txo = channel.channel_monitor().get_funding_txo().ok_or(DecodeError::InvalidValue)?;
+			let funding_txo = channel.get_funding_txo().ok_or(DecodeError::InvalidValue)?;
 			funding_txo_set.insert(funding_txo.clone());
 			if let Some(ref mut monitor) = args.channel_monitors.get_mut(&funding_txo) {
 				if channel.get_cur_local_commitment_transaction_number() != monitor.get_cur_local_commitment_number() ||

lightning/src/ln/channelmonitor.rs

@@ -1284,8 +1284,8 @@ impl<ChanSigner: ChannelKeys> ChannelMonitor<ChanSigner> {
 
 	/// Allows this monitor to scan only for transactions which are applicable. Note that this is
 	/// optional, without it this monitor cannot be used in an SPV client, but you may wish to
-	/// avoid this (or call unset_funding_info) on a monitor you wish to send to a watchtower as it
-	/// provides slightly better privacy.
+	/// avoid this on a monitor you wish to send to a watchtower as it provides slightly better
+	/// privacy.
 	/// It's the responsibility of the caller to register outpoint and script with passing the former
 	/// value as key to add_update_monitor.
 	pub(super) fn set_funding_info(&mut self, new_funding_info: (OutPoint, Script)) {
@@ -1311,17 +1311,6 @@ impl<ChanSigner: ChannelKeys> ChannelMonitor<ChanSigner> {
 		self.commitment_transaction_number_obscure_factor = commitment_transaction_number_obscure_factor;
 	}
 
-	pub(super) fn unset_funding_info(&mut self) {
-		match self.key_storage {
-			Storage::Local { ref mut funding_info, .. } => {
-				*funding_info = None;
-			},
-			Storage::Watchtower { .. } => {
-				panic!("Channel somehow ended up with its internal ChannelMonitor being in Watchtower mode?");
-			},
-		}
-	}
-
 	/// Gets the funding transaction outpoint of the channel this ChannelMonitor is monitoring for.
 	pub fn get_funding_txo(&self) -> Option<OutPoint> {
 		match self.key_storage {