Look up node id from scid in OnionMessenger

[rust-lightning] / lightning / src / blinded_path / mod.rs

diff --git a/lightning/src/blinded_path/mod.rs b/lightning/src/blinded_path/mod.rs
index daa9f033d94e4f0b5544c8cc71bb6e7523ca8acb..07fa7b770249cae94e1ea18269b63805dc933f93 100644 (file)
--- a/lightning/src/blinded_path/mod.rs
+++ b/lightning/src/blinded_path/mod.rs
@@ -58,7 +58,7 @@ pub enum IntroductionNode {
 ///
 /// [BOLT 7]: https://github.com/lightning/bolts/blob/master/07-routing-gossip.md#the-channel_announcement-message
 /// [`ChannelAnnouncement`]: crate::ln::msgs::ChannelAnnouncement
-#[derive(Clone, Debug, Hash, PartialEq, Eq)]
+#[derive(Clone, Copy, Debug, Hash, PartialEq, Eq)]
 pub enum Direction {
        /// The lesser node id when compared lexicographically in ascending order.
        NodeOne,
@@ -66,6 +66,29 @@ pub enum Direction {
        NodeTwo,
 }
 
+/// An interface for looking up the node id of a channel counterparty for the purpose of forwarding
+/// an [`OnionMessage`].
+///
+/// [`OnionMessage`]: crate::ln::msgs::OnionMessage
+pub trait NodeIdLookUp {
+       /// Returns the node id of the forwarding node's channel counterparty with `short_channel_id`.
+       ///
+       /// Here, the forwarding node is referring to the node of the [`OnionMessenger`] parameterized
+       /// by the [`NodeIdLookUp`] and the counterparty to one of that node's peers.
+       ///
+       /// [`OnionMessenger`]: crate::onion_message::messenger::OnionMessenger
+       fn next_node_id(&self, short_channel_id: u64) -> Option<PublicKey>;
+}
+
+/// A [`NodeIdLookUp`] that always returns `None`.
+pub struct EmptyNodeIdLookUp {}
+
+impl NodeIdLookUp for EmptyNodeIdLookUp {
+       fn next_node_id(&self, _short_channel_id: u64) -> Option<PublicKey> {
+               None
+       }
+}
+
 /// An encrypted payload and node id corresponding to a hop in a payment or onion message path, to
 /// be encoded in the sender's onion packet. These hops cannot be identified by outside observers
 /// and thus can be used to hide the identity of the recipient.
@@ -238,4 +261,17 @@ impl Direction {
                        Direction::NodeTwo => core::cmp::max(node_a, node_b),
                }
        }
+
+       /// Returns the [`PublicKey`] from the inputs corresponding to the direction.
+       pub fn select_pubkey<'a>(&self, node_a: &'a PublicKey, node_b: &'a PublicKey) -> &'a PublicKey {
+               let (node_one, node_two) = if NodeId::from_pubkey(node_a) < NodeId::from_pubkey(node_b) {
+                       (node_a, node_b)
+               } else {
+                       (node_b, node_a)
+               };
+               match self {
+                       Direction::NodeOne => node_one,
+                       Direction::NodeTwo => node_two,
+               }
+       }
 }