Account for Path::blinded_tail when adding a shadow cltv offset

diff --git a/lightning/src/routing/router.rs b/lightning/src/routing/router.rs
index e441f53916d3eb0dee2bbcbb9de933433f12750c..b26298391b2f9cb2fe3561b2b5786927a27ef6a2 100644 (file)
--- a/lightning/src/routing/router.rs
+++ b/lightning/src/routing/router.rs
@@ -2180,6 +2180,10 @@ fn add_random_cltv_offset(route: &mut Route, payment_params: &PaymentParameters,
                shadow_ctlv_expiry_delta_offset = cmp::min(shadow_ctlv_expiry_delta_offset, max_path_offset);
 
                // Add 'shadow' CLTV offset to the final hop
+               if let Some(tail) = path.blinded_tail.as_mut() {
+                       tail.excess_final_cltv_expiry_delta = tail.excess_final_cltv_expiry_delta
+                               .checked_add(shadow_ctlv_expiry_delta_offset).unwrap_or(tail.excess_final_cltv_expiry_delta);
+               }
                if let Some(last_hop) = path.hops.last_mut() {
                        last_hop.cltv_expiry_delta = last_hop.cltv_expiry_delta
                                .checked_add(shadow_ctlv_expiry_delta_offset).unwrap_or(last_hop.cltv_expiry_delta);
@@ -5872,6 +5876,50 @@ mod tests {
                assert_eq!(*inflight_htlcs.0.get(&(42, true)).unwrap(), 301);
                assert_eq!(*inflight_htlcs.0.get(&(43, false)).unwrap(), 201);
        }
+
+       #[test]
+       fn blinded_path_cltv_shadow_offset() {
+               // Make sure we add a shadow offset when sending to blinded paths.
+               let blinded_path = BlindedPath {
+                       introduction_node_id: ln_test_utils::pubkey(43),
+                       blinding_point: ln_test_utils::pubkey(44),
+                       blinded_hops: vec![
+                               BlindedHop { blinded_node_id: ln_test_utils::pubkey(45), encrypted_payload: Vec::new() },
+                               BlindedHop { blinded_node_id: ln_test_utils::pubkey(46), encrypted_payload: Vec::new() }
+                       ],
+               };
+               let mut route = Route { paths: vec![Path {
+                       hops: vec![RouteHop {
+                               pubkey: ln_test_utils::pubkey(42),
+                               node_features: NodeFeatures::empty(),
+                               short_channel_id: 42,
+                               channel_features: ChannelFeatures::empty(),
+                               fee_msat: 100,
+                               cltv_expiry_delta: 0,
+                       },
+                       RouteHop {
+                               pubkey: blinded_path.introduction_node_id,
+                               node_features: NodeFeatures::empty(),
+                               short_channel_id: 43,
+                               channel_features: ChannelFeatures::empty(),
+                               fee_msat: 1,
+                               cltv_expiry_delta: 0,
+                       }
+                       ],
+                       blinded_tail: Some(BlindedTail {
+                               hops: blinded_path.blinded_hops,
+                               blinding_point: blinded_path.blinding_point,
+                               excess_final_cltv_expiry_delta: 0,
+                               final_value_msat: 200,
+                       }),
+               }], payment_params: None};
+
+               let payment_params = PaymentParameters::from_node_id(ln_test_utils::pubkey(47), 18);
+               let (_, network_graph, _, _, _) = build_line_graph();
+               add_random_cltv_offset(&mut route, &payment_params, &network_graph.read_only(), &[0; 32]);
+               assert_eq!(route.paths[0].blinded_tail.as_ref().unwrap().excess_final_cltv_expiry_delta, 40);
+               assert_eq!(route.paths[0].hops.last().unwrap().cltv_expiry_delta, 40);
+       }
 }
 
 #[cfg(all(test, not(feature = "no-std")))]