X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=blobdiff_plain;f=lightning%2Fsrc%2Fblinded_path%2Fmessage.rs;h=1a0f63d46000401cd5ffbec7a87c1dd42bf7e786;hb=d792afb08cdc20a30786728c3bfe816dd3b59e47;hp=9a282a5f87d42658599870dd7446d5eef2e1ea5c;hpb=b8d4ac1371bf0db3b28339d4e12fadf02f6add3d;p=rust-lightning

diff --git a/lightning/src/blinded_path/message.rs b/lightning/src/blinded_path/message.rs
index 9a282a5f..1a0f63d4 100644
--- a/lightning/src/blinded_path/message.rs
+++ b/lightning/src/blinded_path/message.rs
@@ -1,3 +1,7 @@
+//! Data structures and methods for constructing [`BlindedPath`]s to send a message over.
+//!
+//! [`BlindedPath`]: crate::blinded_path::BlindedPath
+
 use bitcoin::secp256k1::{self, PublicKey, Secp256k1, SecretKey};
 
 #[allow(unused_imports)]
@@ -16,6 +20,17 @@ use crate::util::ser::{FixedLengthReader, LengthReadableArgs, Writeable, Writer}
 use core::mem;
 use core::ops::Deref;
 
+/// An intermediate node, and possibly a short channel id leading to the next node.
+#[derive(Clone, Debug, Hash, PartialEq, Eq)]
+pub struct ForwardNode {
+	/// This node's pubkey.
+	pub node_id: PublicKey,
+	/// The channel between `node_id` and the next hop. If set, the constructed [`BlindedHop`]'s
+	/// `encrypted_payload` will use this instead of the next [`ForwardNode::node_id`] for a more
+	/// compact representation.
+	pub short_channel_id: Option<u64>,
+}
+
 /// TLVs to encode in an intermediate onion message packet's hop data. When provided in a blinded
 /// route, they are encoded into [`BlindedHop::encrypted_payload`].
 pub(crate) struct ForwardTlvs {
@@ -60,17 +75,24 @@ impl Writeable for ReceiveTlvs {
 	}
 }
 
-/// Construct blinded onion message hops for the given `unblinded_path`.
+/// Construct blinded onion message hops for the given `intermediate_nodes` and `recipient_node_id`.
 pub(super) fn blinded_hops<T: secp256k1::Signing + secp256k1::Verification>(
-	secp_ctx: &Secp256k1<T>, unblinded_path: &[PublicKey], session_priv: &SecretKey
+	secp_ctx: &Secp256k1<T>, intermediate_nodes: &[ForwardNode], recipient_node_id: PublicKey,
+	session_priv: &SecretKey
 ) -> Result<Vec<BlindedHop>, secp256k1::Error> {
-	let blinded_tlvs = unblinded_path.iter()
+	let pks = intermediate_nodes.iter().map(|node| &node.node_id)
+		.chain(core::iter::once(&recipient_node_id));
+	let tlvs = pks.clone()
 		.skip(1) // The first node's TLVs contains the next node's pubkey
-		.map(|pk| ForwardTlvs { next_hop: NextMessageHop::NodeId(*pk), next_blinding_override: None })
-		.map(|tlvs| ControlTlvs::Forward(tlvs))
+		.zip(intermediate_nodes.iter().map(|node| node.short_channel_id))
+		.map(|(pubkey, scid)| match scid {
+			Some(scid) => NextMessageHop::ShortChannelId(scid),
+			None => NextMessageHop::NodeId(*pubkey),
+		})
+		.map(|next_hop| ControlTlvs::Forward(ForwardTlvs { next_hop, next_blinding_override: None }))
 		.chain(core::iter::once(ControlTlvs::Receive(ReceiveTlvs { path_id: None })));
 
-	utils::construct_blinded_hops(secp_ctx, unblinded_path.iter(), blinded_tlvs, session_priv)
+	utils::construct_blinded_hops(secp_ctx, pks, tlvs, session_priv)
 }
 
 // Advance the blinded onion message path by one hop, so make the second hop into the new