From b9343798ba5471d5d5c0a265a23bd514986fe1d8 Mon Sep 17 00:00:00 2001
From: Arik Sosman <git@arik.io>
Date: Thu, 12 Dec 2024 23:59:22 -0800
Subject: [PATCH] f: set multipath_trampoline_data

---
 lightning/src/ln/onion_utils.rs | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/lightning/src/ln/onion_utils.rs b/lightning/src/ln/onion_utils.rs
index 50063a49b32..8265713310c 100644
--- a/lightning/src/ln/onion_utils.rs
+++ b/lightning/src/ln/onion_utils.rs
@@ -33,10 +33,11 @@ use bitcoin::secp256k1::ecdh::SharedSecret;
 use bitcoin::secp256k1::{PublicKey, Scalar, Secp256k1, SecretKey};
 
 use crate::io::{Cursor, Read};
-use crate::ln::msgs::OutboundOnionPayload;
+use crate::ln::msgs::{FinalOnionHopData, OutboundOnionPayload};
 #[allow(unused_imports)]
 use crate::prelude::*;
 use core::ops::Deref;
+use types::payment::PaymentSecret;
 
 pub(crate) struct OnionKeys {
 	#[cfg(test)]
@@ -1400,11 +1401,20 @@ pub fn create_payment_onion<T: secp256k1::Signing>(
 		})?;
 
 		match last_payload {
-			OutboundOnionPayload::Receive { .. } => {
+			OutboundOnionPayload::Receive { payment_data, .. } => {
+				let multipath_trampoline_data = payment_data.map(|d| {
+					let trampoline_payment_secret =
+						Sha256::hash(&d.payment_secret.0).to_byte_array();
+					let total_msat = d.total_msat + path.hops.last().map_or(0, |h| h.fee_msat);
+					FinalOnionHopData {
+						payment_secret: PaymentSecret(trampoline_payment_secret),
+						total_msat,
+					}
+				});
 				onion_payloads.push(OutboundOnionPayload::TrampolineEntrypoint {
 					amt_to_forward: outer_total_msat,
 					outgoing_cltv_value: outer_starting_htlc_offset,
-					multipath_trampoline_data: None,
+					multipath_trampoline_data,
 					trampoline_packet,
 				});
 			},