f don't count blinded hops towards max path len

Author: valentinewallace

lightning/src/ln/blinded_payment_tests.rs

@@ -282,9 +282,10 @@ fn do_forward_checks_failure(check: ForwardCheckFail, intro_fails: bool) {
 
 	let amt_msat = 5000;
 	let (_, payment_hash, payment_secret) = get_payment_preimage_hash(&nodes[3], Some(amt_msat), None);
-	let route_params = get_blinded_route_parameters(amt_msat, payment_secret, 1, 1_0000_0000,
+	let mut route_params = get_blinded_route_parameters(amt_msat, payment_secret, 1, 1_0000_0000,
 		nodes.iter().skip(1).map(|n| n.node.get_our_node_id()).collect(),
 		&[&chan_upd_1_2, &chan_upd_2_3], &chanmon_cfgs[3].keys_manager);
+	route_params.payment_params.max_path_length = 18;
 
 	let route = get_route(&nodes[0], &route_params).unwrap();
 	node_cfgs[0].router.expect_find_route(route_params.clone(), Ok(route.clone()));

lightning/src/ln/onion_utils.rs

@@ -333,23 +333,19 @@ pub(crate) fn set_max_path_length(
 		MIN_FINAL_VALUE_ESTIMATE_WITH_OVERPAY,
 	);
 
-	let (num_reserved_hops, blinded_tail_opt) = route_params
+	let blinded_tail_opt = route_params
 		.payment_params
 		.payee
 		.blinded_route_hints()
 		.iter()
 		.map(|(_, path)| path)
 		.max_by_key(|path| path.serialized_length())
-		.map(|largest_path| {
-			let blinded_tail = BlindedTailHopIter {
-				hops: largest_path.blinded_hops.iter(),
-				blinding_point: largest_path.blinding_point,
-				final_value_msat: final_value_msat_with_overpay_buffer,
-				excess_final_cltv_expiry_delta: 0,
-			};
-			(largest_path.blinded_hops.len(), Some(blinded_tail))
-		})
-		.unwrap_or((1, None));
+		.map(|largest_path| BlindedTailHopIter {
+			hops: largest_path.blinded_hops.iter(),
+			blinding_point: largest_path.blinding_point,
+			final_value_msat: final_value_msat_with_overpay_buffer,
+			excess_final_cltv_expiry_delta: 0,
+		});
 
 	let unblinded_route_hop = RouteHop {
 		pubkey: PublicKey::from_slice(&[2; 33]).unwrap(),
@@ -379,7 +375,7 @@ pub(crate) fn set_max_path_length(
 	let max_path_length = 1300usize
 		.checked_sub(num_reserved_bytes)
 		.map(|p| p / unblinded_intermed_payload_len)
-		.and_then(|l| u8::try_from(l.saturating_add(num_reserved_hops)).ok())
+		.and_then(|l| u8::try_from(l.saturating_add(1)).ok())
 		.ok_or(())?;
 
 	route_params.payment_params.max_path_length =