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Explicitly reject routes that double-back #2741

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Nov 27, 2023
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9 changes: 8 additions & 1 deletion lightning/src/ln/functional_test_utils.rs
Original file line number Diff line number Diff line change
Expand Up @@ -948,7 +948,14 @@ macro_rules! unwrap_send_err {
_ => panic!(),
}
},
_ => panic!(),
&Err(PaymentSendFailure::PathParameterError(ref result)) if !$all_failed => {
assert_eq!(result.len(), 1);
match result[0] {
Err($type) => { $check },
_ => panic!(),
}
},
_ => {panic!()},
}
}
}
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24 changes: 24 additions & 0 deletions lightning/src/ln/functional_tests.rs
Original file line number Diff line number Diff line change
Expand Up @@ -6204,6 +6204,30 @@ fn test_fail_holding_cell_htlc_upon_free_multihop() {
check_added_monitors!(nodes[0], 1);
}

#[test]
fn test_payment_route_reaching_same_channel_twice() {
//A route should not go through the same channel twice
//It is enforced when constructing a route.
let chanmon_cfgs = create_chanmon_cfgs(2);
let node_cfgs = create_node_cfgs(2, &chanmon_cfgs);
let node_chanmgrs = create_node_chanmgrs(2, &node_cfgs, &[None, None]);
let mut nodes = create_network(2, &node_cfgs, &node_chanmgrs);
let _chan = create_announced_chan_between_nodes_with_value(&nodes, 0, 1, 1000000, 0);

let payment_params = PaymentParameters::from_node_id(nodes[1].node.get_our_node_id(), 0)
.with_bolt11_features(nodes[1].node.bolt11_invoice_features()).unwrap();
let (mut route, our_payment_hash, _, our_payment_secret) = get_route_and_payment_hash!(nodes[0], nodes[1], payment_params, 100000000);

// Extend the path by itself, essentially simulating route going through same channel twice
let cloned_hops = route.paths[0].hops.clone();
route.paths[0].hops.extend_from_slice(&cloned_hops);

unwrap_send_err!(nodes[0].node.send_payment_with_route(&route, our_payment_hash,
RecipientOnionFields::secret_only(our_payment_secret), PaymentId(our_payment_hash.0)
), false, APIError::InvalidRoute { ref err },
assert_eq!(err, &"Path went through the same channel twice"));
}

// BOLT 2 Requirements for the Sender when constructing and sending an update_add_htlc message.
// BOLT 2 Requirement: MUST NOT offer amount_msat it cannot pay for in the remote commitment transaction at the current feerate_per_kw (see "Updating Fees") while maintaining its channel reserve.
//TODO: I don't believe this is explicitly enforced when sending an HTLC but as the Fee aspect of the BOLT specs is in flux leaving this as a TODO.
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7 changes: 7 additions & 0 deletions lightning/src/ln/outbound_payment.rs
Original file line number Diff line number Diff line change
Expand Up @@ -1337,6 +1337,13 @@ impl OutboundPayments {
continue 'path_check;
}
}
for (i, hop) in path.hops.iter().enumerate() {
// Check for duplicate channel_id in the remaining hops of the path
if path.hops.iter().skip(i + 1).any(|other_hop| other_hop.short_channel_id == hop.short_channel_id) {
path_errs.push(Err(APIError::InvalidRoute{err: "Path went through the same channel twice".to_owned()}));
continue 'path_check;
}
}
total_value += path.final_value_msat();
path_errs.push(Ok(()));
}
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