Use the new monitor persistence flow for funding_created handling

Building on the previous commits, this finishes our transition to
doing all message-sending in the monitor update completion
pipeline, unifying our immediate- and async- `ChannelMonitor`
update and persistence flows.

Author: TheBlueMatt

lightning/src/ln/channel.rs

@@ -2268,9 +2268,9 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
 
 	pub fn funding_created<SP: Deref, L: Deref>(
 		&mut self, msg: &msgs::FundingCreated, best_block: BestBlock, signer_provider: &SP, logger: &L
-	) -> Result<(msgs::FundingSigned, ChannelMonitor<<SP::Target as SignerProvider>::Signer>, Option<msgs::ChannelReady>), ChannelError>
+	) -> Result<(msgs::FundingSigned, ChannelMonitor<Signer>), ChannelError>
 	where
-		SP::Target: SignerProvider,
+		SP::Target: SignerProvider<Signer = Signer>,
 		L::Target: Logger
 	{
 		if self.is_outbound() {
@@ -2346,10 +2346,13 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
 
 		log_info!(logger, "Generated funding_signed for peer for channel {}", log_bytes!(self.channel_id()));
 
+		let need_channel_ready = self.check_get_channel_ready(0).is_some();
+		self.monitor_updating_paused(false, false, need_channel_ready, Vec::new(), Vec::new(), Vec::new());
+
 		Ok((msgs::FundingSigned {
 			channel_id: self.channel_id,
 			signature
-		}, channel_monitor, self.check_get_channel_ready(0)))
+		}, channel_monitor))
 	}
 
 	/// Handles a funding_signed message from the remote end.
@@ -3740,15 +3743,17 @@ impl<Signer: WriteableEcdsaChannelSigner> Channel<Signer> {
 	}
 
 	/// Indicates that a ChannelMonitor update is in progress and has not yet been fully persisted.
-	/// This must be called immediately after the [`chain::Watch`] call which returned
-	/// [`ChannelMonitorUpdateStatus::InProgress`].
+	/// This must be called before we return the [`ChannelMonitorUpdate`] back to the
+	/// [`ChannelManager`], which will call [`Self::monitor_updating_restored`] once the monitor
+	/// update completes (potentially immediately).
 	/// The messages which were generated with the monitor update must *not* have been sent to the
 	/// remote end, and must instead have been dropped. They will be regenerated when
 	/// [`Self::monitor_updating_restored`] is called.
 	///
+	/// [`ChannelManager`]: super::channelmanager::ChannelManager
 	/// [`chain::Watch`]: crate::chain::Watch
 	/// [`ChannelMonitorUpdateStatus::InProgress`]: crate::chain::ChannelMonitorUpdateStatus::InProgress
-	pub fn monitor_updating_paused(&mut self, resend_raa: bool, resend_commitment: bool,
+	fn monitor_updating_paused(&mut self, resend_raa: bool, resend_commitment: bool,
 		resend_channel_ready: bool, mut pending_forwards: Vec<(PendingHTLCInfo, u64)>,
 		mut pending_fails: Vec<(HTLCSource, PaymentHash, HTLCFailReason)>,
 		mut pending_finalized_claimed_htlcs: Vec<HTLCSource>
@@ -7189,7 +7194,7 @@ mod tests {
 		}]};
 		let funding_outpoint = OutPoint{ txid: tx.txid(), index: 0 };
 		let funding_created_msg = node_a_chan.get_outbound_funding_created(tx.clone(), funding_outpoint, &&logger).unwrap();
-		let (funding_signed_msg, _, _) = node_b_chan.funding_created(&funding_created_msg, best_block, &&keys_provider, &&logger).unwrap();
+		let (funding_signed_msg, _) = node_b_chan.funding_created(&funding_created_msg, best_block, &&keys_provider, &&logger).unwrap();
 
 		// Node B --> Node A: funding signed
 		let _ = node_a_chan.funding_signed(&funding_signed_msg, best_block, &&keys_provider, &&logger);

lightning/src/ln/channelmanager.rs

@@ -4352,60 +4352,31 @@ where
 	}
 
 	fn internal_funding_created(&self, counterparty_node_id: &PublicKey, msg: &msgs::FundingCreated) -> Result<(), MsgHandleErrInternal> {
+		let best_block = *self.best_block.read().unwrap();
+
 		let per_peer_state = self.per_peer_state.read().unwrap();
 		let peer_state_mutex = per_peer_state.get(counterparty_node_id)
 			.ok_or_else(|| {
 				debug_assert!(false);
 				MsgHandleErrInternal::send_err_msg_no_close(format!("Can't find a peer matching the passed counterparty node_id {}", counterparty_node_id), msg.temporary_channel_id)
 			})?;
-		let ((funding_msg, monitor, mut channel_ready), mut chan) = {
-			let best_block = *self.best_block.read().unwrap();
-			let mut peer_state_lock = peer_state_mutex.lock().unwrap();
-			let peer_state = &mut *peer_state_lock;
+
+		let mut peer_state_lock = peer_state_mutex.lock().unwrap();
+		let peer_state = &mut *peer_state_lock;
+		let ((funding_msg, monitor), chan) =
 			match peer_state.channel_by_id.entry(msg.temporary_channel_id) {
 				hash_map::Entry::Occupied(mut chan) => {
 					(try_chan_entry!(self, chan.get_mut().funding_created(msg, best_block, &self.signer_provider, &self.logger), chan), chan.remove())
 				},
 				hash_map::Entry::Vacant(_) => return Err(MsgHandleErrInternal::send_err_msg_no_close(format!("Got a message for a channel from the wrong node! No such channel for the passed counterparty_node_id {}", counterparty_node_id), msg.temporary_channel_id))
-			}
-		};
-		// Because we have exclusive ownership of the channel here we can release the peer_state
-		// lock before watch_channel
-		match self.chain_monitor.watch_channel(monitor.get_funding_txo().0, monitor) {
-			ChannelMonitorUpdateStatus::Completed => {},
-			ChannelMonitorUpdateStatus::PermanentFailure => {
-				// Note that we reply with the new channel_id in error messages if we gave up on the
-				// channel, not the temporary_channel_id. This is compatible with ourselves, but the
-				// spec is somewhat ambiguous here. Not a huge deal since we'll send error messages for
-				// any messages referencing a previously-closed channel anyway.
-				// We do not propagate the monitor update to the user as it would be for a monitor
-				// that we didn't manage to store (and that we don't care about - we don't respond
-				// with the funding_signed so the channel can never go on chain).
-				let (_monitor_update, failed_htlcs) = chan.force_shutdown(false);
-				assert!(failed_htlcs.is_empty());
-				return Err(MsgHandleErrInternal::send_err_msg_no_close("ChannelMonitor storage failure".to_owned(), funding_msg.channel_id));
-			},
-			ChannelMonitorUpdateStatus::InProgress => {
-				// There's no problem signing a counterparty's funding transaction if our monitor
-				// hasn't persisted to disk yet - we can't lose money on a transaction that we haven't
-				// accepted payment from yet. We do, however, need to wait to send our channel_ready
-				// until we have persisted our monitor.
-				chan.monitor_updating_paused(false, false, channel_ready.is_some(), Vec::new(), Vec::new(), Vec::new());
-				channel_ready = None; // Don't send the channel_ready now
-			},
-		}
-		// It's safe to unwrap as we've held the `per_peer_state` read lock since checking that the
-		// peer exists, despite the inner PeerState potentially having no channels after removing
-		// the channel above.
-		let mut peer_state_lock = peer_state_mutex.lock().unwrap();
-		let peer_state = &mut *peer_state_lock;
+			};
+
 		match peer_state.channel_by_id.entry(funding_msg.channel_id) {
 			hash_map::Entry::Occupied(_) => {
-				return Err(MsgHandleErrInternal::send_err_msg_no_close("Already had channel with the new channel_id".to_owned(), funding_msg.channel_id))
+				Err(MsgHandleErrInternal::send_err_msg_no_close("Already had channel with the new channel_id".to_owned(), funding_msg.channel_id))
 			},
 			hash_map::Entry::Vacant(e) => {
-				let mut id_to_peer = self.id_to_peer.lock().unwrap();
-				match id_to_peer.entry(chan.channel_id()) {
+				match self.id_to_peer.lock().unwrap().entry(chan.channel_id()) {
 					hash_map::Entry::Occupied(_) => {
 						return Err(MsgHandleErrInternal::send_err_msg_no_close(
 							"The funding_created message had the same funding_txid as an existing channel - funding is not possible".to_owned(),
@@ -4415,17 +4386,35 @@ where
 						i_e.insert(chan.get_counterparty_node_id());
 					}
 				}
+
+				// There's no problem signing a counterparty's funding transaction if our monitor
+				// hasn't persisted to disk yet - we can't lose money on a transaction that we haven't
+				// accepted payment from yet. We do, however, need to wait to send our channel_ready
+				// until we have persisted our monitor.
+				let new_channel_id = funding_msg.channel_id;
 				peer_state.pending_msg_events.push(events::MessageSendEvent::SendFundingSigned {
 					node_id: counterparty_node_id.clone(),
 					msg: funding_msg,
 				});
-				if let Some(msg) = channel_ready {
-					send_channel_ready!(self, peer_state.pending_msg_events, chan, msg);
+
+				let monitor_res = self.chain_monitor.watch_channel(monitor.get_funding_txo().0, monitor);
+
+				let chan = e.insert(chan);
+				let mut res = handle_new_monitor_update!(self, monitor_res, 0, peer_state_lock, peer_state, chan, MANUALLY_REMOVING, { peer_state.channel_by_id.remove(&new_channel_id) });
+
+				// Note that we reply with the new channel_id in error messages if we gave up on the
+				// channel, not the temporary_channel_id. This is compatible with ourselves, but the
+				// spec is somewhat ambiguous here. Not a huge deal since we'll send error messages for
+				// any messages referencing a previously-closed channel anyway.
+				// We do not propagate the monitor update to the user as it would be for a monitor
+				// that we didn't manage to store (and that we don't care about - we don't respond
+				// with the funding_signed so the channel can never go on chain).
+				if let Err(MsgHandleErrInternal { shutdown_finish: Some((res, _)), .. }) = &mut res {
+					res.0 = None;
 				}
-				e.insert(chan);
+				res
 			}
 		}
-		Ok(())
 	}
 
 	fn internal_funding_signed(&self, counterparty_node_id: &PublicKey, msg: &msgs::FundingSigned) -> Result<(), MsgHandleErrInternal> {

lightning/src/ln/functional_tests.rs

@@ -8736,9 +8736,9 @@ fn test_duplicate_chan_id() {
 	};
 	check_added_monitors!(nodes[0], 0);
 	nodes[1].node.handle_funding_created(&nodes[0].node.get_our_node_id(), &funding_created);
-	// At this point we'll try to add a duplicate channel monitor, which will be rejected, but
-	// still needs to be cleared here.
-	check_added_monitors!(nodes[1], 1);
+	// At this point we'll look up if the channel_id is present and immediately fail the channel
+	// without trying to persist the `ChannelMonitor`.
+	check_added_monitors!(nodes[1], 0);
 
 	// ...still, nodes[1] will reject the duplicate channel.
 	{