Add TrampolineForward variant to PendingHTLCRouting

Author: arik-so

lightning/src/ln/channelmanager.rs

@@ -132,7 +132,7 @@ pub use crate::ln::outbound_payment::{Bolt12PaymentError, ProbeSendFailure, Retr
 #[cfg(test)]
 pub(crate) use crate::ln::outbound_payment::PaymentSendFailure;
 use crate::ln::script::ShutdownScript;
-
+use crate::routing::gossip::NodeId;
 // We hold various information about HTLC relay in the HTLC objects in Channel itself:
 //
 // Upon receipt of an HTLC from a peer, we'll give it a PendingHTLCStatus indicating if it should
@@ -170,6 +170,25 @@ pub enum PendingHTLCRouting {
 		/// The absolute CLTV of the inbound HTLC
 		incoming_cltv_expiry: Option<u32>,
 	},
+
+	/// An HTLC which should be forwarded on to another Trampoline node.
+	TrampolineForward {
+		/// The onion shared secret we build with the sender (or the preceding Trampoline node) used
+		/// to decrypt the onion.
+		///
+		/// This is later used to encrypt failure packets in the event that the HTLC is failed.
+		incoming_shared_secret: [u8; 32],
+		/// The onion which should be included in the forwarded HTLC, telling the next hop what to
+		/// do with the HTLC.
+		onion_packet: msgs::TrampolineOnionPacket,
+		/// The node ID of the Trampoline node which we need to route this HTLC to.
+		node_id: NodeId, // This should be NonZero<u64> eventually when we bump MSRV
+		/// Set if this HTLC is being forwarded within a blinded path.
+		blinded: Option<BlindedForward>,
+		/// The absolute CLTV of the inbound HTLC
+		incoming_cltv_expiry: Option<u32>,
+	},
+
 	/// The onion indicates that this is a payment for an invoice (supposedly) generated by us.
 	///
 	/// Note that at this point, we have not checked that the invoice being paid was actually
@@ -278,6 +297,7 @@ impl PendingHTLCRouting {
 	fn incoming_cltv_expiry(&self) -> Option<u32> {
 		match self {
 			Self::Forward { incoming_cltv_expiry, .. } => *incoming_cltv_expiry,
+			Self::TrampolineForward { incoming_cltv_expiry, .. } => *incoming_cltv_expiry,
 			Self::Receive { incoming_cltv_expiry, .. } => Some(*incoming_cltv_expiry),
 			Self::ReceiveKeysend { incoming_cltv_expiry, .. } => Some(*incoming_cltv_expiry),
 		}
@@ -8857,6 +8877,7 @@ This indicates a bug inside LDK. Please report this error at https://github.com/
 				for (forward_info, prev_htlc_id) in pending_forwards.drain(..) {
 					let scid = match forward_info.routing {
 						PendingHTLCRouting::Forward { short_channel_id, .. } => short_channel_id,
+						PendingHTLCRouting::TrampolineForward { .. } => 0,
 						PendingHTLCRouting::Receive { .. } => 0,
 						PendingHTLCRouting::ReceiveKeysend { .. } => 0,
 					};
@@ -12397,6 +12418,13 @@ impl_writeable_tlv_based_enum!(PendingHTLCRouting,
 		(7, has_recipient_created_payment_secret, (default_value, false)),
 		(9, payment_context, option),
 	},
+	(3, TrampolineForward) => {
+		(0, incoming_shared_secret, required),
+		(1, onion_packet, required),
+		(2, blinded, option),
+		(3, node_id, required),
+		(4, incoming_cltv_expiry, option),
+	}
 );
 
 impl_writeable_tlv_based!(PendingHTLCInfo, {