Add ChannelManager support for monitor update failure in one place

src/ln/channelmonitor.rs

@@ -39,6 +39,7 @@ use std::sync::{Arc,Mutex};
 use std::{hash,cmp};
 
 /// An error enum representing a failure to persist a channel monitor update.
+#[derive(Clone)]
 pub enum ChannelMonitorUpdateErr {
 	/// Used to indicate a temporary failure (eg connection to a watchtower failed, but is expected
 	/// to succeed at some point in the future).
@@ -47,6 +48,22 @@ pub enum ChannelMonitorUpdateErr {
 	/// submitting new commitment transactions to the remote party.
 	/// ChannelManager::test_restore_channel_monitor can be used to retry the update(s) and restore
 	/// the channel to an operational state.
+	///
+	/// Note that continuing to operate when no copy of the updated ChannelMonitor could be
+	/// persisted is unsafe - if you failed to store the update on your own local disk you should
+	/// instead return PermanentFailure to force closure of the channel ASAP.
+	///
+	/// Even when a channel has been "frozen" updates to the ChannelMonitor can continue to occur
+	/// (eg if an inbound HTLC which we forwarded was claimed upstream resulting in us attempting
+	/// to claim it on this channel) and those updates must be applied wherever they can be. At
+	/// least one such updated ChannelMonitor must be persisted otherwise PermanentFailure should
+	/// be returned to get things on-chain ASAP using only the in-memory copy. Obviously updates to
+	/// the channel which would invalidate previous ChannelMonitors are not made when a channel has
+	/// been "frozen".
+	///
+	/// Note that even if updates made after TemporaryFailure succeed you must still call
+	/// test_restore_channel_monitor to ensure you have the latest monitor and re-enable normal
+	/// channel operation.
 	TemporaryFailure,
 	/// Used to indicate no further channel monitor updates will be allowed (eg we've moved on to a
 	/// different watchtower and cannot update with all watchtowers that were previously informed

src/ln/msgs.rs

@@ -224,7 +224,7 @@ pub struct FundingSigned {
 }
 
 /// A funding_locked message to be sent or received from a peer
-#[derive(Clone)]
+#[derive(Clone, PartialEq)]
 pub struct FundingLocked {
 	pub(crate) channel_id: [u8; 32],
 	pub(crate) next_per_commitment_point: PublicKey,
@@ -244,7 +244,7 @@ pub struct ClosingSigned {
 }
 
 /// An update_add_htlc message to be sent or received from a peer
-#[derive(Clone)]
+#[derive(Clone, PartialEq)]
 pub struct UpdateAddHTLC {
 	pub(crate) channel_id: [u8; 32],
 	pub(crate) htlc_id: u64,
@@ -255,23 +255,23 @@ pub struct UpdateAddHTLC {
 }
 
 /// An update_fulfill_htlc message to be sent or received from a peer
-#[derive(Clone)]
+#[derive(Clone, PartialEq)]
 pub struct UpdateFulfillHTLC {
 	pub(crate) channel_id: [u8; 32],
 	pub(crate) htlc_id: u64,
 	pub(crate) payment_preimage: [u8; 32],
 }
 
 /// An update_fail_htlc message to be sent or received from a peer
-#[derive(Clone)]
+#[derive(Clone, PartialEq)]
 pub struct UpdateFailHTLC {
 	pub(crate) channel_id: [u8; 32],
 	pub(crate) htlc_id: u64,
 	pub(crate) reason: OnionErrorPacket,
 }
 
 /// An update_fail_malformed_htlc message to be sent or received from a peer
-#[derive(Clone)]
+#[derive(Clone, PartialEq)]
 pub struct UpdateFailMalformedHTLC {
 	pub(crate) channel_id: [u8; 32],
 	pub(crate) htlc_id: u64,
@@ -280,32 +280,36 @@ pub struct UpdateFailMalformedHTLC {
 }
 
 /// A commitment_signed message to be sent or received from a peer
-#[derive(Clone)]
+#[derive(Clone, PartialEq)]
 pub struct CommitmentSigned {
 	pub(crate) channel_id: [u8; 32],
 	pub(crate) signature: Signature,
 	pub(crate) htlc_signatures: Vec<Signature>,
 }
 
 /// A revoke_and_ack message to be sent or received from a peer
+#[derive(Clone, PartialEq)]
 pub struct RevokeAndACK {
 	pub(crate) channel_id: [u8; 32],
 	pub(crate) per_commitment_secret: [u8; 32],
 	pub(crate) next_per_commitment_point: PublicKey,
 }
 
 /// An update_fee message to be sent or received from a peer
+#[derive(PartialEq)]
 pub struct UpdateFee {
 	pub(crate) channel_id: [u8; 32],
 	pub(crate) feerate_per_kw: u32,
 }
 
+#[derive(PartialEq)]
 pub(crate) struct DataLossProtect {
 	pub(crate) your_last_per_commitment_secret: [u8; 32],
 	pub(crate) my_current_per_commitment_point: PublicKey,
 }
 
 /// A channel_reestablish message to be sent or received from a peer
+#[derive(PartialEq)]
 pub struct ChannelReestablish {
 	pub(crate) channel_id: [u8; 32],
 	pub(crate) next_local_commitment_number: u64,
@@ -463,6 +467,7 @@ pub struct HandleError { //TODO: rename me
 
 /// Struct used to return values from revoke_and_ack messages, containing a bunch of commitment
 /// transaction updates if they were pending.
+#[derive(PartialEq)]
 pub struct CommitmentUpdate {
 	pub(crate) update_add_htlcs: Vec<UpdateAddHTLC>,
 	pub(crate) update_fulfill_htlcs: Vec<UpdateFulfillHTLC>,
@@ -629,7 +634,18 @@ pub(crate) struct OnionPacket {
 	pub(crate) hmac: [u8; 32],
 }
 
-#[derive(Clone)]
+impl PartialEq for OnionPacket {
+	fn eq(&self, other: &OnionPacket) -> bool {
+		for (i, j) in self.hop_data.iter().zip(other.hop_data.iter()) {
+			if i != j { return false; }
+		}
+		self.version == other.version &&
+			self.public_key == other.public_key &&
+			self.hmac == other.hmac
+	}
+}
+
+#[derive(Clone, PartialEq)]
 pub(crate) struct OnionErrorPacket {
 	// This really should be a constant size slice, but the spec lets these things be up to 128KB?
 	// (TODO) We limit it in decode to much lower...

src/ln/peer_handler.rs

@@ -866,6 +866,17 @@ impl<Descriptor: SocketDescriptor> PeerManager<Descriptor> {
 						Self::do_attempt_write_data(&mut descriptor, peer);
 						continue;
 					},
+					Event::SendRevokeAndACK { ref node_id, ref msg } => {
+						log_trace!(self, "Handling SendRevokeAndACK event in peer_handler for node {} for channel {}",
+								log_pubkey!(node_id),
+								log_bytes!(msg.channel_id));
+						let (mut descriptor, peer) = get_peer_for_forwarding!(node_id, {
+								//TODO: Do whatever we're gonna do for handling dropped messages
+							});
+						peer.pending_outbound_buffer.push_back(peer.channel_encryptor.encrypt_message(&encode_msg!(msg, 133)));
+						Self::do_attempt_write_data(&mut descriptor, peer);
+						continue;
+					},
 					Event::SendShutdown { ref node_id, ref msg } => {
 						log_trace!(self, "Handling Shutdown event in peer_handler for node {} for channel {}",
 								log_pubkey!(node_id),

src/util/errors.rs

@@ -32,7 +32,10 @@ pub enum APIError {
 	ChannelUnavailable {
 		/// A human-readable error message
 		err: &'static str
-	}
+	},
+	/// An attempt to call add_update_monitor returned an Err (ie you did this!), causing the
+	/// attempted action to fail.
+	MonitorUpdateFailed,
 }
 
 impl fmt::Debug for APIError {
@@ -42,6 +45,7 @@ impl fmt::Debug for APIError {
 			APIError::FeeRateTooHigh {ref err, ref feerate} => write!(f, "{} feerate: {}", err, feerate),
 			APIError::RouteError {ref err} => f.write_str(err),
 			APIError::ChannelUnavailable {ref err} => f.write_str(err),
+			APIError::MonitorUpdateFailed => f.write_str("Client indicated a channel monitor update failed"),
 		}
 	}
 }

src/util/events.rs

@@ -129,6 +129,15 @@ pub enum Event {
 		/// The update messages which should be sent. ALL messages in the struct should be sent!
 		updates: msgs::CommitmentUpdate,
 	},
+	/// Used to indicate that a revoke_and_ack message should be sent to the peer with the given node_id.
+	///
+	/// This event is handled by PeerManager::process_events if you are using a PeerManager.
+	SendRevokeAndACK {
+		/// The node_id of the node which should receive this message
+		node_id: PublicKey,
+		/// The message which should be sent.
+		msg: msgs::RevokeAndACK,
+	},
 	/// Used to indicate that a shutdown message should be sent to the peer with the given node_id.
 	///
 	/// This event is handled by PeerManager::process_events if you are using a PeerManager.

src/util/test_utils.rs

@@ -38,12 +38,14 @@ impl chaininterface::FeeEstimator for TestFeeEstimator {
 pub struct TestChannelMonitor {
 	pub added_monitors: Mutex<Vec<(OutPoint, channelmonitor::ChannelMonitor)>>,
 	pub simple_monitor: Arc<channelmonitor::SimpleManyChannelMonitor<OutPoint>>,
+	pub update_ret: Mutex<Result<(), channelmonitor::ChannelMonitorUpdateErr>>,
 }
 impl TestChannelMonitor {
 	pub fn new(chain_monitor: Arc<chaininterface::ChainWatchInterface>, broadcaster: Arc<chaininterface::BroadcasterInterface>) -> Self {
 		Self {
 			added_monitors: Mutex::new(Vec::new()),
 			simple_monitor: channelmonitor::SimpleManyChannelMonitor::new(chain_monitor, broadcaster),
+			update_ret: Mutex::new(Ok(())),
 		}
 	}
 }
@@ -57,7 +59,8 @@ impl channelmonitor::ManyChannelMonitor for TestChannelMonitor {
 		w.0.clear();
 		monitor.write_for_watchtower(&mut w).unwrap(); // This at least shouldn't crash...
 		self.added_monitors.lock().unwrap().push((funding_txo, monitor.clone()));
-		self.simple_monitor.add_update_monitor(funding_txo, monitor)
+		assert!(self.simple_monitor.add_update_monitor(funding_txo, monitor).is_ok());
+		self.update_ret.lock().unwrap().clone()
 	}
 }