Define a default MessageRouter implementation

Otherwise, users need to define one when using "Simple" type aliases.

Author: jkczyz

lightning/src/ln/peer_handler.rs

@@ -607,11 +607,11 @@ impl Peer {
 /// issues such as overly long function definitions.
 ///
 /// This is not exported to bindings users as `Arc`s don't make sense in bindings.
-pub type SimpleArcPeerManager<SD, M, T, F, C, L, R> = PeerManager<
+pub type SimpleArcPeerManager<SD, M, T, F, C, L> = PeerManager<
 	SD,
 	Arc<SimpleArcChannelManager<M, T, F, L>>,
 	Arc<P2PGossipSync<Arc<NetworkGraph<Arc<L>>>, Arc<C>, Arc<L>>>,
-	Arc<SimpleArcOnionMessenger<L, R>>,
+	Arc<SimpleArcOnionMessenger<L>>,
 	Arc<L>,
 	IgnoringMessageHandler,
 	Arc<KeysManager>
@@ -626,12 +626,12 @@ pub type SimpleArcPeerManager<SD, M, T, F, C, L, R> = PeerManager<
 ///
 /// This is not exported to bindings users as general type aliases don't make sense in bindings.
 pub type SimpleRefPeerManager<
-	'a, 'b, 'c, 'd, 'e, 'f, 'g, 'h, 'i, 'j, 'k, 'l, 'm, 'n, SD, M, T, F, C, L, R
+	'a, 'b, 'c, 'd, 'e, 'f, 'g, 'h, 'i, 'j, 'k, 'l, 'm, 'n, SD, M, T, F, C, L
 > = PeerManager<
 	SD,
 	&'n SimpleRefChannelManager<'a, 'b, 'c, 'd, 'e, 'f, 'g, 'm, M, T, F, L>,
 	&'f P2PGossipSync<&'g NetworkGraph<&'f L>, &'h C, &'f L>,
-	&'i SimpleRefOnionMessenger<'g, 'm, 'n, L, R>,
+	&'i SimpleRefOnionMessenger<'g, 'm, 'n, L>,
 	&'f L,
 	IgnoringMessageHandler,
 	&'c KeysManager

lightning/src/onion_message/messenger.rs

@@ -152,6 +152,17 @@ pub trait MessageRouter {
 	) -> Result<OnionMessagePath, ()>;
 }
 
+/// A [`MessageRouter`] that always fails.
+pub struct DefaultMessageRouter;
+
+impl MessageRouter for DefaultMessageRouter {
+	fn find_path(
+		&self, _sender: PublicKey, _peers: Vec<PublicKey>, _destination: Destination
+	) -> Result<OnionMessagePath, ()> {
+		Err(())
+	}
+}
+
 /// A path for sending an [`msgs::OnionMessage`].
 #[derive(Clone)]
 pub struct OnionMessagePath {
@@ -598,11 +609,11 @@ where
 ///
 /// [`SimpleArcChannelManager`]: crate::ln::channelmanager::SimpleArcChannelManager
 /// [`SimpleArcPeerManager`]: crate::ln::peer_handler::SimpleArcPeerManager
-pub type SimpleArcOnionMessenger<L, R> = OnionMessenger<
+pub type SimpleArcOnionMessenger<L> = OnionMessenger<
 	Arc<KeysManager>,
 	Arc<KeysManager>,
 	Arc<L>,
-	Arc<R>,
+	Arc<DefaultMessageRouter>,
 	IgnoringMessageHandler,
 	IgnoringMessageHandler
 >;
@@ -614,11 +625,11 @@ pub type SimpleArcOnionMessenger<L, R> = OnionMessenger<
 ///
 /// [`SimpleRefChannelManager`]: crate::ln::channelmanager::SimpleRefChannelManager
 /// [`SimpleRefPeerManager`]: crate::ln::peer_handler::SimpleRefPeerManager
-pub type SimpleRefOnionMessenger<'a, 'b, 'c, L, R> = OnionMessenger<
+pub type SimpleRefOnionMessenger<'a, 'b, 'c, L> = OnionMessenger<
 	&'a KeysManager,
 	&'a KeysManager,
 	&'b L,
-	&'c R,
+	&'c DefaultMessageRouter,
 	IgnoringMessageHandler,
 	IgnoringMessageHandler
 >;