Rename ChannelKeys -> Sign and generic it consistently

The `ChannelKeys` object really isn't about keys at all anymore,
its all about signing. At the same time, we rename the type aliases
used in traits from both `ChanKeySigner` and `Keys` to just
`Signer` (or, in contexts where Channel isnt clear, `ChanSigner`).

Author: TheBlueMatt

fuzz/src/chanmon_consistency.rs

@@ -34,11 +34,11 @@ use lightning::chain::channelmonitor;
 use lightning::chain::channelmonitor::{ChannelMonitor, ChannelMonitorUpdateErr, MonitorEvent};
 use lightning::chain::transaction::OutPoint;
 use lightning::chain::chaininterface::{BroadcasterInterface, ConfirmationTarget, FeeEstimator};
-use lightning::chain::keysinterface::{KeysInterface, InMemoryChannelKeys};
+use lightning::chain::keysinterface::{KeysInterface, InMemorySigner};
 use lightning::ln::channelmanager::{ChannelManager, PaymentHash, PaymentPreimage, PaymentSecret, PaymentSendFailure, ChannelManagerReadArgs};
 use lightning::ln::features::{ChannelFeatures, InitFeatures, NodeFeatures};
 use lightning::ln::msgs::{CommitmentUpdate, ChannelMessageHandler, DecodeError, ErrorAction, UpdateAddHTLC, Init};
-use lightning::util::enforcing_trait_impls::{EnforcingChannelKeys, INITIAL_REVOKED_COMMITMENT_NUMBER};
+use lightning::util::enforcing_trait_impls::{EnforcingSigner, INITIAL_REVOKED_COMMITMENT_NUMBER};
 use lightning::util::errors::APIError;
 use lightning::util::events;
 use lightning::util::logger::Logger;
@@ -87,7 +87,7 @@ impl Writer for VecWriter {
 
 struct TestChainMonitor {
 	pub logger: Arc<dyn Logger>,
-	pub chain_monitor: Arc<chainmonitor::ChainMonitor<EnforcingChannelKeys, Arc<dyn chain::Filter>, Arc<TestBroadcaster>, Arc<FuzzEstimator>, Arc<dyn Logger>, Arc<TestPersister>>>,
+	pub chain_monitor: Arc<chainmonitor::ChainMonitor<EnforcingSigner, Arc<dyn chain::Filter>, Arc<TestBroadcaster>, Arc<FuzzEstimator>, Arc<dyn Logger>, Arc<TestPersister>>>,
 	pub update_ret: Mutex<Result<(), channelmonitor::ChannelMonitorUpdateErr>>,
 	// If we reload a node with an old copy of ChannelMonitors, the ChannelManager deserialization
 	// logic will automatically force-close our channels for us (as we don't have an up-to-date
@@ -109,9 +109,9 @@ impl TestChainMonitor {
 	}
 }
 impl chain::Watch for TestChainMonitor {
-	type Keys = EnforcingChannelKeys;
+	type ChanSigner = EnforcingSigner;
 
-	fn watch_channel(&self, funding_txo: OutPoint, monitor: channelmonitor::ChannelMonitor<EnforcingChannelKeys>) -> Result<(), channelmonitor::ChannelMonitorUpdateErr> {
+	fn watch_channel(&self, funding_txo: OutPoint, monitor: channelmonitor::ChannelMonitor<EnforcingSigner>) -> Result<(), channelmonitor::ChannelMonitorUpdateErr> {
 		let mut ser = VecWriter(Vec::new());
 		monitor.write(&mut ser).unwrap();
 		if let Some(_) = self.latest_monitors.lock().unwrap().insert(funding_txo, (monitor.get_latest_update_id(), ser.0)) {
@@ -128,7 +128,7 @@ impl chain::Watch for TestChainMonitor {
 			hash_map::Entry::Occupied(entry) => entry,
 			hash_map::Entry::Vacant(_) => panic!("Didn't have monitor on update call"),
 		};
-		let mut deserialized_monitor = <(BlockHash, channelmonitor::ChannelMonitor<EnforcingChannelKeys>)>::
+		let mut deserialized_monitor = <(BlockHash, channelmonitor::ChannelMonitor<EnforcingSigner>)>::
 			read(&mut Cursor::new(&map_entry.get().1), &OnlyReadsKeysInterface {}).unwrap().1;
 		deserialized_monitor.update_monitor(&update, &&TestBroadcaster{}, &&FuzzEstimator{}, &self.logger).unwrap();
 		let mut ser = VecWriter(Vec::new());
@@ -149,7 +149,7 @@ struct KeyProvider {
 	revoked_commitments: Mutex<HashMap<[u8;32], Arc<Mutex<u64>>>>,
 }
 impl KeysInterface for KeyProvider {
-	type ChanKeySigner = EnforcingChannelKeys;
+	type Signer = EnforcingSigner;
 
 	fn get_node_secret(&self) -> SecretKey {
 		SecretKey::from_slice(&[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, self.node_id]).unwrap()
@@ -167,10 +167,10 @@ impl KeysInterface for KeyProvider {
 		PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 3, self.node_id]).unwrap())
 	}
 
-	fn get_channel_keys(&self, _inbound: bool, channel_value_satoshis: u64) -> EnforcingChannelKeys {
+	fn get_channel_signer(&self, _inbound: bool, channel_value_satoshis: u64) -> EnforcingSigner {
 		let secp_ctx = Secp256k1::signing_only();
 		let id = self.rand_bytes_id.fetch_add(1, atomic::Ordering::Relaxed);
-		let keys = InMemoryChannelKeys::new(
+		let keys = InMemorySigner::new(
 			&secp_ctx,
 			SecretKey::from_slice(&[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 4, self.node_id]).unwrap(),
 			SecretKey::from_slice(&[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 5, self.node_id]).unwrap(),
@@ -182,23 +182,23 @@ impl KeysInterface for KeyProvider {
 			[0; 32],
 		);
 		let revoked_commitment = self.make_revoked_commitment_cell(keys.commitment_seed);
-		EnforcingChannelKeys::new_with_revoked(keys, revoked_commitment, false)
+		EnforcingSigner::new_with_revoked(keys, revoked_commitment, false)
 	}
 
 	fn get_secure_random_bytes(&self) -> [u8; 32] {
 		let id = self.rand_bytes_id.fetch_add(1, atomic::Ordering::Relaxed);
 		[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, id, 11, self.node_id]
 	}
 
-	fn read_chan_signer(&self, buffer: &[u8]) -> Result<Self::ChanKeySigner, DecodeError> {
+	fn read_chan_signer(&self, buffer: &[u8]) -> Result<Self::Signer, DecodeError> {
 		let mut reader = std::io::Cursor::new(buffer);
 
-		let inner: InMemoryChannelKeys = Readable::read(&mut reader)?;
+		let inner: InMemorySigner = Readable::read(&mut reader)?;
 		let revoked_commitment = self.make_revoked_commitment_cell(inner.commitment_seed);
 
 		let last_commitment_number = Readable::read(&mut reader)?;
 
-		Ok(EnforcingChannelKeys {
+		Ok(EnforcingSigner {
 			inner,
 			last_commitment_number: Arc::new(Mutex::new(last_commitment_number)),
 			revoked_commitment,
@@ -259,7 +259,7 @@ fn check_payment_err(send_err: PaymentSendFailure) {
 	}
 }
 
-type ChanMan = ChannelManager<EnforcingChannelKeys, Arc<TestChainMonitor>, Arc<TestBroadcaster>, Arc<KeyProvider>, Arc<FuzzEstimator>, Arc<dyn Logger>>;
+type ChanMan = ChannelManager<EnforcingSigner, Arc<TestChainMonitor>, Arc<TestBroadcaster>, Arc<KeyProvider>, Arc<FuzzEstimator>, Arc<dyn Logger>>;
 
 #[inline]
 fn send_payment(source: &ChanMan, dest: &ChanMan, dest_chan_id: u64, amt: u64, payment_id: &mut u8) -> bool {
@@ -339,7 +339,7 @@ pub fn do_test<Out: test_logger::Output>(data: &[u8], out: Out) {
 			let mut monitors = HashMap::new();
 			let mut old_monitors = $old_monitors.latest_monitors.lock().unwrap();
 			for (outpoint, (update_id, monitor_ser)) in old_monitors.drain() {
-				monitors.insert(outpoint, <(BlockHash, ChannelMonitor<EnforcingChannelKeys>)>::read(&mut Cursor::new(&monitor_ser), &OnlyReadsKeysInterface {}).expect("Failed to read monitor").1);
+				monitors.insert(outpoint, <(BlockHash, ChannelMonitor<EnforcingSigner>)>::read(&mut Cursor::new(&monitor_ser), &OnlyReadsKeysInterface {}).expect("Failed to read monitor").1);
 				chain_monitor.latest_monitors.lock().unwrap().insert(outpoint, (update_id, monitor_ser));
 			}
 			let mut monitor_refs = HashMap::new();

fuzz/src/chanmon_deser.rs

@@ -4,7 +4,7 @@
 use bitcoin::hash_types::BlockHash;
 
 use lightning::chain::channelmonitor;
-use lightning::util::enforcing_trait_impls::EnforcingChannelKeys;
+use lightning::util::enforcing_trait_impls::EnforcingSigner;
 use lightning::util::ser::{ReadableArgs, Writer, Writeable};
 use lightning::util::test_utils::OnlyReadsKeysInterface;
 
@@ -25,10 +25,10 @@ impl Writer for VecWriter {
 
 #[inline]
 pub fn do_test<Out: test_logger::Output>(data: &[u8], _out: Out) {
-	if let Ok((latest_block_hash, monitor)) = <(BlockHash, channelmonitor::ChannelMonitor<EnforcingChannelKeys>)>::read(&mut Cursor::new(data), &OnlyReadsKeysInterface {}) {
+	if let Ok((latest_block_hash, monitor)) = <(BlockHash, channelmonitor::ChannelMonitor<EnforcingSigner>)>::read(&mut Cursor::new(data), &OnlyReadsKeysInterface {}) {
 		let mut w = VecWriter(Vec::new());
 		monitor.write(&mut w).unwrap();
-		let deserialized_copy = <(BlockHash, channelmonitor::ChannelMonitor<EnforcingChannelKeys>)>::read(&mut Cursor::new(&w.0), &OnlyReadsKeysInterface {}).unwrap();
+		let deserialized_copy = <(BlockHash, channelmonitor::ChannelMonitor<EnforcingSigner>)>::read(&mut Cursor::new(&w.0), &OnlyReadsKeysInterface {}).unwrap();
 		assert!(latest_block_hash == deserialized_copy.0);
 		assert!(monitor == deserialized_copy.1);
 	}

fuzz/src/full_stack.rs

@@ -30,15 +30,15 @@ use lightning::chain;
 use lightning::chain::chaininterface::{BroadcasterInterface, ConfirmationTarget, FeeEstimator};
 use lightning::chain::chainmonitor;
 use lightning::chain::transaction::OutPoint;
-use lightning::chain::keysinterface::{InMemoryChannelKeys, KeysInterface};
+use lightning::chain::keysinterface::{InMemorySigner, KeysInterface};
 use lightning::ln::channelmanager::{ChannelManager, PaymentHash, PaymentPreimage, PaymentSecret};
 use lightning::ln::peer_handler::{MessageHandler,PeerManager,SocketDescriptor};
 use lightning::ln::msgs::DecodeError;
 use lightning::routing::router::get_route;
 use lightning::routing::network_graph::NetGraphMsgHandler;
 use lightning::util::config::UserConfig;
 use lightning::util::events::{EventsProvider,Event};
-use lightning::util::enforcing_trait_impls::EnforcingChannelKeys;
+use lightning::util::enforcing_trait_impls::EnforcingSigner;
 use lightning::util::logger::Logger;
 use lightning::util::ser::Readable;
 
@@ -148,14 +148,14 @@ impl<'a> std::hash::Hash for Peer<'a> {
 }
 
 type ChannelMan = ChannelManager<
-	EnforcingChannelKeys,
-	Arc<chainmonitor::ChainMonitor<EnforcingChannelKeys, Arc<dyn chain::Filter>, Arc<TestBroadcaster>, Arc<FuzzEstimator>, Arc<dyn Logger>, Arc<TestPersister>>>,
+	EnforcingSigner,
+	Arc<chainmonitor::ChainMonitor<EnforcingSigner, Arc<dyn chain::Filter>, Arc<TestBroadcaster>, Arc<FuzzEstimator>, Arc<dyn Logger>, Arc<TestPersister>>>,
 	Arc<TestBroadcaster>, Arc<KeyProvider>, Arc<FuzzEstimator>, Arc<dyn Logger>>;
 type PeerMan<'a> = PeerManager<Peer<'a>, Arc<ChannelMan>, Arc<NetGraphMsgHandler<Arc<dyn chain::Access>, Arc<dyn Logger>>>, Arc<dyn Logger>>;
 
 struct MoneyLossDetector<'a> {
 	manager: Arc<ChannelMan>,
-	monitor: Arc<chainmonitor::ChainMonitor<EnforcingChannelKeys, Arc<dyn chain::Filter>, Arc<TestBroadcaster>, Arc<FuzzEstimator>, Arc<dyn Logger>, Arc<TestPersister>>>,
+	monitor: Arc<chainmonitor::ChainMonitor<EnforcingSigner, Arc<dyn chain::Filter>, Arc<TestBroadcaster>, Arc<FuzzEstimator>, Arc<dyn Logger>, Arc<TestPersister>>>,
 	handler: PeerMan<'a>,
 
 	peers: &'a RefCell<[bool; 256]>,
@@ -169,7 +169,7 @@ struct MoneyLossDetector<'a> {
 impl<'a> MoneyLossDetector<'a> {
 	pub fn new(peers: &'a RefCell<[bool; 256]>,
 	           manager: Arc<ChannelMan>,
-	           monitor: Arc<chainmonitor::ChainMonitor<EnforcingChannelKeys, Arc<dyn chain::Filter>, Arc<TestBroadcaster>, Arc<FuzzEstimator>, Arc<dyn Logger>, Arc<TestPersister>>>,
+	           monitor: Arc<chainmonitor::ChainMonitor<EnforcingSigner, Arc<dyn chain::Filter>, Arc<TestBroadcaster>, Arc<FuzzEstimator>, Arc<dyn Logger>, Arc<TestPersister>>>,
 	           handler: PeerMan<'a>) -> Self {
 		MoneyLossDetector {
 			manager,
@@ -248,7 +248,7 @@ struct KeyProvider {
 	counter: AtomicU64,
 }
 impl KeysInterface for KeyProvider {
-	type ChanKeySigner = EnforcingChannelKeys;
+	type Signer = EnforcingSigner;
 
 	fn get_node_secret(&self) -> SecretKey {
 		self.node_secret.clone()
@@ -266,11 +266,11 @@ impl KeysInterface for KeyProvider {
 		PublicKey::from_secret_key(&secp_ctx, &SecretKey::from_slice(&[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]).unwrap())
 	}
 
-	fn get_channel_keys(&self, inbound: bool, channel_value_satoshis: u64) -> EnforcingChannelKeys {
+	fn get_channel_signer(&self, inbound: bool, channel_value_satoshis: u64) -> EnforcingSigner {
 		let ctr = self.counter.fetch_add(1, Ordering::Relaxed) as u8;
 		let secp_ctx = Secp256k1::signing_only();
-		EnforcingChannelKeys::new(if inbound {
-			InMemoryChannelKeys::new(
+		EnforcingSigner::new(if inbound {
+			InMemorySigner::new(
 				&secp_ctx,
 				SecretKey::from_slice(&[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, ctr]).unwrap(),
 				SecretKey::from_slice(&[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 2, ctr]).unwrap(),
@@ -282,7 +282,7 @@ impl KeysInterface for KeyProvider {
 				[0; 32]
 			)
 		} else {
-			InMemoryChannelKeys::new(
+			InMemorySigner::new(
 				&secp_ctx,
 				SecretKey::from_slice(&[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 7, ctr]).unwrap(),
 				SecretKey::from_slice(&[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 8, ctr]).unwrap(),
@@ -302,8 +302,8 @@ impl KeysInterface for KeyProvider {
 		(ctr >> 8*7) as u8, (ctr >> 8*6) as u8, (ctr >> 8*5) as u8, (ctr >> 8*4) as u8, (ctr >> 8*3) as u8, (ctr >> 8*2) as u8, (ctr >> 8*1) as u8, 14, (ctr >> 8*0) as u8]
 	}
 
-	fn read_chan_signer(&self, data: &[u8]) -> Result<EnforcingChannelKeys, DecodeError> {
-		EnforcingChannelKeys::read(&mut std::io::Cursor::new(data))
+	fn read_chan_signer(&self, data: &[u8]) -> Result<EnforcingSigner, DecodeError> {
+		EnforcingSigner::read(&mut std::io::Cursor::new(data))
 	}
 }
 

fuzz/src/utils/test_persister.rs

@@ -1,14 +1,14 @@
 use lightning::chain::channelmonitor;
 use lightning::chain::transaction::OutPoint;
-use lightning::util::enforcing_trait_impls::EnforcingChannelKeys;
+use lightning::util::enforcing_trait_impls::EnforcingSigner;
 
 pub struct TestPersister {}
-impl channelmonitor::Persist<EnforcingChannelKeys> for TestPersister {
-	fn persist_new_channel(&self, _funding_txo: OutPoint, _data: &channelmonitor::ChannelMonitor<EnforcingChannelKeys>) -> Result<(), channelmonitor::ChannelMonitorUpdateErr> {
+impl channelmonitor::Persist<EnforcingSigner> for TestPersister {
+	fn persist_new_channel(&self, _funding_txo: OutPoint, _data: &channelmonitor::ChannelMonitor<EnforcingSigner>) -> Result<(), channelmonitor::ChannelMonitorUpdateErr> {
 		Ok(())
 	}
 
-	fn update_persisted_channel(&self, _funding_txo: OutPoint, _update: &channelmonitor::ChannelMonitorUpdate, _data: &channelmonitor::ChannelMonitor<EnforcingChannelKeys>) -> Result<(), channelmonitor::ChannelMonitorUpdateErr> {
+	fn update_persisted_channel(&self, _funding_txo: OutPoint, _update: &channelmonitor::ChannelMonitorUpdate, _data: &channelmonitor::ChannelMonitor<EnforcingSigner>) -> Result<(), channelmonitor::ChannelMonitorUpdateErr> {
 		Ok(())
 	}
 }

lightning-net-tokio/src/lib.rs

@@ -36,8 +36,8 @@
 //! type Logger = dyn lightning::util::logger::Logger;
 //! type ChainAccess = dyn lightning::chain::Access;
 //! type ChainFilter = dyn lightning::chain::Filter;
-//! type DataPersister = dyn lightning::chain::channelmonitor::Persist<lightning::chain::keysinterface::InMemoryChannelKeys>;
-//! type ChainMonitor = lightning::chain::chainmonitor::ChainMonitor<lightning::chain::keysinterface::InMemoryChannelKeys, Arc<ChainFilter>, Arc<TxBroadcaster>, Arc<FeeEstimator>, Arc<Logger>, Arc<DataPersister>>;
+//! type DataPersister = dyn lightning::chain::channelmonitor::Persist<lightning::chain::keysinterface::InMemoryChannelSigner>;
+//! type ChainMonitor = lightning::chain::chainmonitor::ChainMonitor<lightning::chain::keysinterface::InMemoryChannelSigner, Arc<ChainFilter>, Arc<TxBroadcaster>, Arc<FeeEstimator>, Arc<Logger>, Arc<DataPersister>>;
 //! type ChannelManager = lightning::ln::channelmanager::SimpleArcChannelManager<ChainMonitor, TxBroadcaster, FeeEstimator, Logger>;
 //! type PeerManager = lightning::ln::peer_handler::SimpleArcPeerManager<lightning_net_tokio::SocketDescriptor, ChainMonitor, TxBroadcaster, FeeEstimator, ChainAccess, Logger>;
 //!

lightning-persister/src/lib.rs

@@ -5,7 +5,7 @@ extern crate libc;
 use bitcoin::hashes::hex::ToHex;
 use lightning::chain::channelmonitor::{ChannelMonitor, ChannelMonitorUpdate, ChannelMonitorUpdateErr};
 use lightning::chain::channelmonitor;
-use lightning::chain::keysinterface::ChannelKeys;
+use lightning::chain::keysinterface::Sign;
 use lightning::chain::transaction::OutPoint;
 use lightning::util::ser::Writeable;
 use std::fs;
@@ -45,7 +45,7 @@ trait DiskWriteable {
 	fn write(&self, writer: &mut fs::File) -> Result<(), Error>;
 }
 
-impl<ChanSigner: ChannelKeys> DiskWriteable for ChannelMonitor<ChanSigner> {
+impl<ChanSigner: Sign> DiskWriteable for ChannelMonitor<ChanSigner> {
 	fn write(&self, writer: &mut fs::File) -> Result<(), Error> {
 		Writeable::write(self, writer)
 	}
@@ -97,7 +97,7 @@ impl FilesystemPersister {
 
 	#[cfg(test)]
 	fn load_channel_data<Keys: KeysInterface>(&self, keys: &Keys) ->
-		Result<HashMap<OutPoint, ChannelMonitor<Keys::ChanKeySigner>>, ChannelMonitorUpdateErr> {
+		Result<HashMap<OutPoint, ChannelMonitor<Keys::Signer>>, ChannelMonitorUpdateErr> {
 		if let Err(_) = fs::create_dir_all(&self.path_to_channel_data) {
 			return Err(ChannelMonitorUpdateErr::PermanentFailure);
 		}
@@ -120,7 +120,7 @@ impl FilesystemPersister {
 			if contents.is_err() { return Err(ChannelMonitorUpdateErr::PermanentFailure); }
 
 			if let Ok((_, loaded_monitor)) =
-				<(BlockHash, ChannelMonitor<Keys::ChanKeySigner>)>::read(&mut Cursor::new(&contents.unwrap()), keys) {
+				<(BlockHash, ChannelMonitor<Keys::Signer>)>::read(&mut Cursor::new(&contents.unwrap()), keys) {
 				res.insert(OutPoint { txid: txid.unwrap(), index: index.unwrap() }, loaded_monitor);
 			} else {
 				return Err(ChannelMonitorUpdateErr::PermanentFailure);
@@ -130,7 +130,7 @@ impl FilesystemPersister {
 	}
 }
 
-impl<ChanSigner: ChannelKeys + Send + Sync> channelmonitor::Persist<ChanSigner> for FilesystemPersister {
+impl<ChanSigner: Sign + Send + Sync> channelmonitor::Persist<ChanSigner> for FilesystemPersister {
 	fn persist_new_channel(&self, funding_txo: OutPoint, monitor: &ChannelMonitor<ChanSigner>) -> Result<(), ChannelMonitorUpdateErr> {
 		self.write_channel_data(funding_txo, monitor)
 		  .map_err(|_| ChannelMonitorUpdateErr::PermanentFailure)