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fuzz: derive routes from payment paths
Public commit record
78/100 · Adequate
What the developer wrote
Authored by Joost Jager
fuzz: derive routes from payment paths
Build direct, forwarded, and MPP routes from a shared per-path hop
description. Derive route fees and node metadata from that description,
and increase the CLTV delta by 100 for each successive hop.
Later failure tracking needs to describe the exact route that was sent.
Keeping route construction and bookkeeping on one representation
prevents them from drifting and prepares the tracker to retain more
per-hop failure context.
✓ Descriptive subject✓ Names a concrete action or component✓ Provides detailed explanatory context✓ Mentions testing or verification
What changed, and why it matters
This commit is a refactoring of internal fuzz-test code only. It changes how fake Lightning payment routes are built in a test harness so that route construction uses a single shared helper instead of hand-written route structures. There is no change to production code, no user-facing behavior change, and no security fix or vulnerability.
Recommended action
No action required. This is a test-only refactoring with no security relevance.
Security signals we found
No strong security signals were identified.
Evidence from the diff
The diff modifies fuzz/src/chanmon_consistency.rs, which is part of the LDK fuzzing harness. It introduces PaymentHop/PaymentPath types and a route_from_payment_paths helper that derives RouteHop fields (pubkey, features, SCID, fee_msat, cltv_expiry_delta) from a per-path hop description. Existing direct, forwarded, and MPP route construction sites are converted to use this helper. The CLTV delta is now computed as (idx + 1) * 100 per hop, which matches the previous hard-coded values (100, 200) for one- and two-hop routes. No production library code is touched.
Changed components
fuzz/src/chanmon_consistency.rsInspect captured patch +96 / −111
diff --git a/fuzz/src/chanmon_consistency.rs b/fuzz/src/chanmon_consistency.rs
index 9487241..7c17dc9 100644
--- a/fuzz/src/chanmon_consistency.rs
+++ b/fuzz/src/chanmon_consistency.rs
@@ -1943,6 +1943,14 @@ impl PeerLink {
}
}
+#[derive(Clone, Copy)]
+struct PaymentHop {
+ amount_msat: u64,
+ short_channel_id: u64,
+}
+
+type PaymentPath = Vec<PaymentHop>;
+
struct PendingPayment {
payment_id: PaymentId,
payment_hash: PaymentHash,
@@ -2069,6 +2077,42 @@ impl PaymentTracker {
(secret, hash, id)
}
+ fn route_from_payment_paths(
+ payment_paths: &[PaymentPath], path_nodes: &[&HarnessNode<'_>],
+ route_params: RouteParameters,
+ ) -> Route {
+ let paths = payment_paths
+ .iter()
+ .map(|payment_path| {
+ assert_eq!(payment_path.len(), path_nodes.len());
+ let hops = payment_path
+ .iter()
+ .enumerate()
+ .map(|(idx, hop)| {
+ let node = path_nodes[idx];
+ let fee_msat =
+ payment_path.get(idx + 1).map_or(hop.amount_msat, |next_hop| {
+ hop.amount_msat.checked_sub(next_hop.amount_msat).expect(
+ "payment path amounts must not increase toward the recipient",
+ )
+ });
+ RouteHop {
+ pubkey: node.get_our_node_id(),
+ node_features: node.node_features(),
+ short_channel_id: hop.short_channel_id,
+ channel_features: node.channel_features(),
+ fee_msat,
+ cltv_expiry_delta: (idx as u32 + 1) * 100,
+ maybe_announced_channel: true,
+ }
+ })
+ .collect();
+ Path { hops, blinded_tail: None }
+ })
+ .collect();
+ Route { paths, route_params }
+ }
+
fn send(
&mut self, nodes: &[HarnessNode<'_>; 3], source_idx: usize, dest_idx: usize,
dest_chan_id: ChannelId, amt: u64,
@@ -2088,25 +2132,13 @@ impl PaymentTracker {
)
})
.unwrap_or((0, 0, 0));
+ let payment_paths =
+ vec![vec![PaymentHop { amount_msat: amt, short_channel_id: dest_scid }]];
let route_params = RouteParameters::from_payment_params_and_value(
PaymentParameters::from_node_id(source.get_our_node_id(), TEST_FINAL_CLTV),
amt,
);
- let route = Route {
- paths: vec![Path {
- hops: vec![RouteHop {
- pubkey: dest.get_our_node_id(),
- node_features: dest.node_features(),
- short_channel_id: dest_scid,
- channel_features: dest.channel_features(),
- fee_msat: amt,
- cltv_expiry_delta: 200,
- maybe_announced_channel: true,
- }],
- blinded_tail: None,
- }],
- route_params,
- };
+ let route = Self::route_from_payment_paths(&payment_paths, &[dest], route_params);
let onion = RecipientOnionFields::secret_only(secret, amt);
let res = source.send_payment_with_route(route, hash, onion, id);
let succeeded = match res {
@@ -2157,36 +2189,15 @@ impl PaymentTracker {
.and_then(|chan| chan.short_channel_id)
.unwrap_or(0);
let first_hop_fee = 50_000;
+ let payment_paths = vec![vec![
+ PaymentHop { amount_msat: amt + first_hop_fee, short_channel_id: middle_scid },
+ PaymentHop { amount_msat: amt, short_channel_id: dest_scid },
+ ]];
let route_params = RouteParameters::from_payment_params_and_value(
PaymentParameters::from_node_id(source.get_our_node_id(), TEST_FINAL_CLTV),
amt,
);
- let route = Route {
- paths: vec![Path {
- hops: vec![
- RouteHop {
- pubkey: middle.get_our_node_id(),
- node_features: middle.node_features(),
- short_channel_id: middle_scid,
- channel_features: middle.channel_features(),
- fee_msat: first_hop_fee,
- cltv_expiry_delta: 100,
- maybe_announced_channel: true,
- },
- RouteHop {
- pubkey: dest.get_our_node_id(),
- node_features: dest.node_features(),
- short_channel_id: dest_scid,
- channel_features: dest.channel_features(),
- fee_msat: amt,
- cltv_expiry_delta: 200,
- maybe_announced_channel: true,
- },
- ],
- blinded_tail: None,
- }],
- route_params,
- };
+ let route = Self::route_from_payment_paths(&payment_paths, &[middle, dest], route_params);
let onion = RecipientOnionFields::secret_only(secret, amt);
let res = source.send_payment_with_route(route, hash, onion, id);
let succeeded = match res {
@@ -2231,43 +2242,37 @@ impl PaymentTracker {
}
let amt_per_path = amt / num_paths as u64;
- let mut paths = Vec::with_capacity(num_paths);
let dest_chans = dest.list_channels();
- let dest_scids = dest_chan_ids.iter().map(|chan_id| {
- dest_chans
- .iter()
- .find(|chan| chan.channel_id == *chan_id)
- .and_then(|chan| chan.short_channel_id)
- .unwrap()
- });
-
- for (i, dest_scid) in dest_scids.enumerate() {
- let path_amt = if i == num_paths - 1 {
- amt - amt_per_path * (num_paths as u64 - 1)
- } else {
- amt_per_path
- };
+ let dest_scids: Vec<_> = dest_chan_ids
+ .iter()
+ .map(|chan_id| {
+ dest_chans
+ .iter()
+ .find(|chan| chan.channel_id == *chan_id)
+ .and_then(|chan| chan.short_channel_id)
+ .unwrap()
+ })
+ .collect();
- paths.push(Path {
- hops: vec![RouteHop {
- pubkey: dest.get_our_node_id(),
- node_features: dest.node_features(),
- short_channel_id: dest_scid,
- channel_features: dest.channel_features(),
- fee_msat: path_amt,
- cltv_expiry_delta: 200,
- maybe_announced_channel: true,
- }],
- blinded_tail: None,
- });
- }
+ let payment_paths: Vec<PaymentPath> = dest_scids
+ .iter()
+ .enumerate()
+ .map(|(i, dest_scid)| {
+ let path_amt = if i == num_paths - 1 {
+ amt - amt_per_path * (num_paths as u64 - 1)
+ } else {
+ amt_per_path
+ };
+ vec![PaymentHop { amount_msat: path_amt, short_channel_id: *dest_scid }]
+ })
+ .collect();
let route_params = RouteParameters::from_payment_params_and_value(
PaymentParameters::from_node_id(dest.get_our_node_id(), TEST_FINAL_CLTV),
amt,
);
- let route = Route { paths, route_params };
+ let route = Self::route_from_payment_paths(&payment_paths, &[dest], route_params);
let onion = RecipientOnionFields::secret_only(secret, amt);
let res = source.send_payment_with_route(route, hash, onion, id);
let succeeded = match res {
@@ -2301,7 +2306,6 @@ impl PaymentTracker {
let first_hop_fee = 50_000;
let amt_per_path = amt / num_paths as u64;
let fee_per_path = first_hop_fee / num_paths as u64;
- let mut paths = Vec::with_capacity(num_paths);
let middle_chans = middle.list_channels();
let middle_scids: Vec<_> = middle_chan_ids
@@ -2327,51 +2331,32 @@ impl PaymentTracker {
})
.collect();
- for i in 0..num_paths {
- let middle_scid = middle_scids[i % middle_scids.len()];
- let dest_scid = dest_scids[i % dest_scids.len()];
-
- let path_amt = if i == num_paths - 1 {
- amt - amt_per_path * (num_paths as u64 - 1)
- } else {
- amt_per_path
- };
- let path_fee = if i == num_paths - 1 {
- first_hop_fee - fee_per_path * (num_paths as u64 - 1)
- } else {
- fee_per_path
- };
-
- paths.push(Path {
- hops: vec![
- RouteHop {
- pubkey: middle.get_our_node_id(),
- node_features: middle.node_features(),
- short_channel_id: middle_scid,
- channel_features: middle.channel_features(),
- fee_msat: path_fee,
- cltv_expiry_delta: 100,
- maybe_announced_channel: true,
- },
- RouteHop {
- pubkey: dest.get_our_node_id(),
- node_features: dest.node_features(),
- short_channel_id: dest_scid,
- channel_features: dest.channel_features(),
- fee_msat: path_amt,
- cltv_expiry_delta: 200,
- maybe_announced_channel: true,
- },
- ],
- blinded_tail: None,
- });
- }
+ let payment_paths: Vec<PaymentPath> = (0..num_paths)
+ .map(|i| {
+ let middle_scid = middle_scids[i % middle_scids.len()];
+ let dest_scid = dest_scids[i % dest_scids.len()];
+ let path_amt = if i == num_paths - 1 {
+ amt - amt_per_path * (num_paths as u64 - 1)
+ } else {
+ amt_per_path
+ };
+ let path_fee = if i == num_paths - 1 {
+ first_hop_fee - fee_per_path * (num_paths as u64 - 1)
+ } else {
+ fee_per_path
+ };
+ vec![
+ PaymentHop { amount_msat: path_amt + path_fee, short_channel_id: middle_scid },
+ PaymentHop { amount_msat: path_amt, short_channel_id: dest_scid },
+ ]
+ })
+ .collect();
let route_params = RouteParameters::from_payment_params_and_value(
PaymentParameters::from_node_id(dest.get_our_node_id(), TEST_FINAL_CLTV),
amt,
);
- let route = Route { paths, route_params };
+ let route = Self::route_from_payment_paths(&payment_paths, &[middle, dest], route_params);
let onion = RecipientOnionFields::secret_only(secret, amt);
let res = source.send_payment_with_route(route, hash, onion, id);
let succeeded = match res {
Risk score
Our methodology →Why this scored 15/100
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