Add test for async signing for commitment_signed

This adds a test (and fixes the implementation!) to check that we correctly
resume processing after awaiting an asynchronous signature for a
`commitment_signed` event.

lightning/src/ln/async_signer_tests.rs

@@ -11,9 +11,9 @@
 //! properly with a signer implementation that asynchronously derives signatures.
 
 use crate::events::{MessageSendEvent, MessageSendEventsProvider};
-use crate::ln::msgs::ChannelMessageHandler;
-
 use crate::ln::functional_test_utils::*;
+use crate::ln::msgs::ChannelMessageHandler;
+use crate::ln::channelmanager::{PaymentId, RecipientOnionFields};
 
 #[test]
 fn test_async_commitment_signature_for_funding_created() {
@@ -24,7 +24,7 @@ fn test_async_commitment_signature_for_funding_created() {
 	let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
 
 	nodes[0].node.create_channel(nodes[1].node.get_our_node_id(), 100000, 10001, 42, None).unwrap();
-	
+
 	// nodes[0] --- open_channel --> nodes[1]
 	let mut open_chan_msg = get_event_msg!(nodes[0], MessageSendEvent::SendOpenChannel, nodes[1].node.get_our_node_id());
 	nodes[1].node.handle_open_channel(&nodes[0].node.get_our_node_id(), &open_chan_msg);
@@ -130,3 +130,62 @@ fn test_async_commitment_signature_for_funding_signed() {
 	check_added_monitors(&nodes[0], 1);
 	expect_channel_pending_event(&nodes[0], &nodes[1].node.get_our_node_id());
 }
+
+#[test]
+fn test_async_commitment_signature_for_commitment_signed() {
+	let chanmon_cfgs = create_chanmon_cfgs(2);
+	let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
+	let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
+	let nodes = create_network(2, &node_cfgs, &node_chanmgrs);
+	create_announced_chan_between_nodes(&nodes, 0, 1);
+
+	let chan_id = {
+		let per_peer_state = nodes[0].node.per_peer_state.read().unwrap();
+		let chan_lock = per_peer_state.get(&nodes[1].node.get_our_node_id()).unwrap().lock().unwrap();
+		let chan_ids = chan_lock.channel_by_id.keys().collect::<Vec<_>>();
+		let n = chan_ids.len();
+		assert_eq!(n, 1, "expected one channel, not {n}");
+		*chan_ids[0]
+	};
+
+	// Send a payment.
+	let src = &nodes[0];
+	let dst = &nodes[1];
+	let (route, our_payment_hash, _our_payment_preimage, our_payment_secret) = get_route_and_payment_hash!(src, dst, 8000000);
+	src.node.send_payment_with_route(&route, our_payment_hash,
+		RecipientOnionFields::secret_only(our_payment_secret), PaymentId(our_payment_hash.0)).unwrap();
+	check_added_monitors!(src, 1);
+
+	// Pass the payment along the route.
+	let payment_event = {
+		let mut events = src.node.get_and_clear_pending_msg_events();
+		assert_eq!(events.len(), 1);
+		SendEvent::from_event(events.remove(0))
+	};
+	assert_eq!(payment_event.node_id, dst.node.get_our_node_id());
+	assert_eq!(payment_event.msgs.len(), 1);
+
+	dst.node.handle_update_add_htlc(&src.node.get_our_node_id(), &payment_event.msgs[0]);
+
+	// Mark dst's signer as unavailable and handle src's commitment_signed: while dst won't yet have a
+	// `commitment_signed` of its own to offer, it should publish a `revoke_and_ack`.
+	dst.set_channel_signer_available(&src.node.get_our_node_id(), &chan_id, false);
+	dst.node.handle_commitment_signed(&src.node.get_our_node_id(), &payment_event.commitment_msg);
+	check_added_monitors(dst, 1);
+
+	get_event_msg!(dst, MessageSendEvent::SendRevokeAndACK, src.node.get_our_node_id());
+
+	// Mark dst's signer as available and retry: we now expect to see dst's `commitment_signed`.
+	dst.set_channel_signer_available(&src.node.get_our_node_id(), &chan_id, true);
+	dst.node.signer_unblocked(Some((src.node.get_our_node_id(), chan_id)));
+
+	let events = dst.node.get_and_clear_pending_msg_events();
+	let n = events.len();
+	assert_eq!(n, 1, "expected one message, got {n}");
+	if let MessageSendEvent::UpdateHTLCs { ref node_id, ref updates } = events[0] {
+		assert_eq!(node_id, &src.node.get_our_node_id());
+	} else {
+		panic!("expected UpdateHTLCs message, not {:?}", events[0]);
+	};
+}
+

lightning/src/ln/channel.rs

@@ -3863,7 +3863,7 @@ impl<SP: Deref> Channel<SP> where
 	/// blocked.
 	pub fn signer_maybe_unblocked<L: Deref>(&mut self, logger: &L) -> SignerResumeUpdates where L::Target: Logger {
 		let commitment_update = if self.context.signer_pending_commitment_update {
-			None
+			self.get_last_commitment_update_for_send(logger).ok()
 		} else { None };
 		let funding_signed = if self.context.signer_pending_funding && !self.context.is_outbound() {
 			self.context.get_funding_signed_msg(logger).1

lightning/src/ln/functional_test_utils.rs

@@ -945,7 +945,8 @@ macro_rules! unwrap_send_err {
 pub fn check_added_monitors<CM: AChannelManager, H: NodeHolder<CM=CM>>(node: &H, count: usize) {
 	if let Some(chain_monitor) = node.chain_monitor() {
 		let mut added_monitors = chain_monitor.added_monitors.lock().unwrap();
-		assert_eq!(added_monitors.len(), count);
+		let n = added_monitors.len();
+		assert_eq!(n, count, "expected {count} monitors to be added, not {n}");
 		added_monitors.clear();
 	}
 }