Don't use compact blinded paths for reply paths

There's no need to save space when creating reply paths since they are
part of onion messages rather than in QR codes. Use normal blinded paths
for these instead as they are less likely to become invalid in case of
channel closure.

Author: jkczyz

lightning/src/ln/channelmanager.rs

@@ -8270,7 +8270,8 @@ macro_rules! create_offer_builder { ($self: ident, $builder: ty) => {
 		let entropy = &*$self.entropy_source;
 		let secp_ctx = &$self.secp_ctx;
 
-		let path = $self.create_blinded_path().map_err(|_| Bolt12SemanticError::MissingPaths)?;
+		let path = $self.create_compact_blinded_path()
+			.map_err(|_| Bolt12SemanticError::MissingPaths)?;
 		let builder = OfferBuilder::deriving_signing_pubkey(
 			node_id, expanded_key, entropy, secp_ctx
 		)
@@ -8337,7 +8338,8 @@ macro_rules! create_refund_builder { ($self: ident, $builder: ty) => {
 		let entropy = &*$self.entropy_source;
 		let secp_ctx = &$self.secp_ctx;
 
-		let path = $self.create_blinded_path().map_err(|_| Bolt12SemanticError::MissingPaths)?;
+		let path = $self.create_compact_blinded_path()
+			.map_err(|_| Bolt12SemanticError::MissingPaths)?;
 		let builder = RefundBuilder::deriving_payer_id(
 			node_id, expanded_key, entropy, secp_ctx, amount_msats, payment_id
 		)?
@@ -8686,13 +8688,31 @@ where
 		inbound_payment::get_payment_preimage(payment_hash, payment_secret, &self.inbound_payment_key)
 	}
 
-	/// Creates a blinded path by delegating to [`MessageRouter::create_compact_blinded_paths`].
+	/// Creates a blinded path by delegating to [`MessageRouter::create_blinded_paths`].
 	///
 	/// Errors if the `MessageRouter` errors or returns an empty `Vec`.
 	fn create_blinded_path(&self) -> Result<BlindedPath, ()> {
 		let recipient = self.get_our_node_id();
 		let secp_ctx = &self.secp_ctx;
 
+		let peers = self.per_peer_state.read().unwrap()
+			.iter()
+			.filter(|(_, peer)| peer.lock().unwrap().latest_features.supports_onion_messages())
+			.map(|(node_id, _)| *node_id)
+			.collect::<Vec<_>>();
+
+		self.router
+			.create_blinded_paths(recipient, peers, secp_ctx)
+			.and_then(|paths| paths.into_iter().next().ok_or(()))
+	}
+
+	/// Creates a blinded path by delegating to [`MessageRouter::create_compact_blinded_paths`].
+	///
+	/// Errors if the `MessageRouter` errors or returns an empty `Vec`.
+	fn create_compact_blinded_path(&self) -> Result<BlindedPath, ()> {
+		let recipient = self.get_our_node_id();
+		let secp_ctx = &self.secp_ctx;
+
 		let peers = self.per_peer_state.read().unwrap()
 			.iter()
 			.map(|(node_id, peer_state)| (node_id, peer_state.lock().unwrap()))

lightning/src/ln/offers_tests.rs

@@ -427,11 +427,9 @@ fn creates_and_pays_for_offer_using_two_hop_blinded_path() {
 			payer_note_truncated: None,
 		},
 	});
-	let introduction_node_id = resolve_introduction_node(alice, &reply_path);
 	assert_eq!(invoice_request.amount_msats(), None);
 	assert_ne!(invoice_request.payer_id(), david_id);
-	assert_eq!(introduction_node_id, charlie_id);
-	assert!(matches!(reply_path.introduction_node, IntroductionNode::DirectedShortChannelId(..)));
+	assert_eq!(reply_path.introduction_node, IntroductionNode::NodeId(charlie_id));
 
 	let onion_message = alice.onion_messenger.next_onion_message_for_peer(charlie_id).unwrap();
 	charlie.onion_messenger.handle_onion_message(&alice_id, &onion_message);
@@ -582,11 +580,9 @@ fn creates_and_pays_for_offer_using_one_hop_blinded_path() {
 			payer_note_truncated: None,
 		},
 	});
-	let introduction_node_id = resolve_introduction_node(alice, &reply_path);
 	assert_eq!(invoice_request.amount_msats(), None);
 	assert_ne!(invoice_request.payer_id(), bob_id);
-	assert_eq!(introduction_node_id, bob_id);
-	assert!(matches!(reply_path.introduction_node, IntroductionNode::DirectedShortChannelId(..)));
+	assert_eq!(reply_path.introduction_node, IntroductionNode::NodeId(bob_id));
 
 	let onion_message = alice.onion_messenger.next_onion_message_for_peer(bob_id).unwrap();
 	bob.onion_messenger.handle_onion_message(&alice_id, &onion_message);