fix: use the update_add_htlc's cltv_expiry for comparison

As noted in BOLT 4, we should be using the update_add_htlc's cltv_expiry,
not the CLTV expiry set by the sender in the onion for this comparison.
See here: https://github.com/lightning/bolts/blob/4dcc377209509b13cf89a4b91fde7d478f5b46d8/04-onion-routing.md?plain=1#L334

diff --git a/lightning/src/ln/channelmanager.rs b/lightning/src/ln/channelmanager.rs
index 1e9a3ed011def00672e46053391ac2b7d4f723ea..755cb2c76845678dc97e75c804884e0c3dcdec3c 100644 (file)
--- a/lightning/src/ln/channelmanager.rs
+++ b/lightning/src/ln/channelmanager.rs
@@ -2940,7 +2940,7 @@ where
                // payment logic has enough time to fail the HTLC backward before our onchain logic triggers a
                // channel closure (see HTLC_FAIL_BACK_BUFFER rationale).
                let current_height: u32 = self.best_block.read().unwrap().height();
-               if (outgoing_cltv_value as u64) <= current_height as u64 + HTLC_FAIL_BACK_BUFFER as u64 + 1 {
+               if cltv_expiry <= current_height + HTLC_FAIL_BACK_BUFFER + 1 {
                        let mut err_data = Vec::with_capacity(12);
                        err_data.extend_from_slice(&amt_msat.to_be_bytes());
                        err_data.extend_from_slice(&current_height.to_be_bytes());
@@ -11096,6 +11096,30 @@ mod tests {
                        sender_intended_amt_msat - extra_fee_msat, 42, None, true, Some(extra_fee_msat)).is_ok());
        }
 
+       #[test]
+       fn test_final_incorrect_cltv(){
+               let chanmon_cfg = create_chanmon_cfgs(1);
+               let node_cfg = create_node_cfgs(1, &chanmon_cfg);
+               let node_chanmgr = create_node_chanmgrs(1, &node_cfg, &[None]);
+               let node = create_network(1, &node_cfg, &node_chanmgr);
+
+               let result = node[0].node.construct_recv_pending_htlc_info(msgs::InboundOnionPayload::Receive {
+                       amt_msat: 100,
+                       outgoing_cltv_value: 22,
+                       payment_metadata: None,
+                       keysend_preimage: None,
+                       payment_data: Some(msgs::FinalOnionHopData {
+                               payment_secret: PaymentSecret([0; 32]), total_msat: 100,
+                       }),
+                       custom_tlvs: Vec::new(),
+               }, [0; 32], PaymentHash([0; 32]), 100, 23, None, true, None);
+
+               // Should not return an error as this condition:
+               // https://github.com/lightning/bolts/blob/4dcc377209509b13cf89a4b91fde7d478f5b46d8/04-onion-routing.md?plain=1#L334
+               // is not satisfied.
+               assert!(result.is_ok());
+       }
+
        #[test]
        fn test_inbound_anchors_manual_acceptance() {
                // Tests that we properly limit inbound channels when we have the manual-channel-acceptance