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fix(relay): decouple global circuit ceiling from the per-peer limit #701

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Merged
varex83 merged 1 commit into from
Sep 18, 2026
+21 −2
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fix(relay): decouple global circuit ceiling from the per-peer limit #701

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23 changes: 21 additions & 2 deletions crates/relay-server/src/config.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -60,7 +60,16 @@ pub(crate) fn create_relay_config(config: &Config) -> relay::Config {
max_reservations: config.max_conns,
max_reservations_per_peer: config.max_res_per_peer,
reservation_duration: Duration::from_secs(ONE_HOUR_SECONDS),
max_circuits: config.max_res_per_peer,
// rust-libp2p splits circuit limits into a global ceiling
// (`max_circuits`) and a per-peer one (`max_circuits_per_peer`);
// go-libp2p's `Resources.MaxCircuits` is only the per-peer limit and
// has no global counterpart (go-libp2p@v0.41.1
// p2p/protocol/circuitv2/relay/relay.go:293,301 checks the source and
// destination peer counts only). So only the per-peer value mirrors
// Charon's `MaxCircuits = MaxResPerPeer`; the global ceiling is sized
// from the connection budget instead, keeping a safety valve
// go-libp2p lacks without throttling total relay throughput.
max_circuits: config.max_conns,
max_circuits_per_peer: config.max_res_per_peer,
max_circuit_duration: Duration::from_secs(ONE_HOUR_SECONDS),
max_circuit_bytes: MB_32,
Expand Down Expand Up @@ -110,7 +119,8 @@ mod tests {
let relay_config = create_relay_config(&test_config(64, 8));
assert_eq!(relay_config.max_reservations, 64);
assert_eq!(relay_config.max_reservations_per_peer, 8);
assert_eq!(relay_config.max_circuits, 8);
// Global circuit ceiling tracks `max_conns`, not `max_res_per_peer`.
assert_eq!(relay_config.max_circuits, 64);
assert_eq!(relay_config.max_circuits_per_peer, 8);
assert_eq!(
relay_config.reservation_duration,
Expand All @@ -123,6 +133,15 @@ mod tests {
assert_eq!(relay_config.max_circuit_bytes, MB_32);
}

#[test]
fn global_circuit_ceiling_is_decoupled_from_per_peer_limit() {
// CLI defaults (`crates/cli/src/commands/relay.rs`), matching Charon's
// `p2p-max-reservations` / `p2p-max-connections`.
let relay_config = create_relay_config(&test_config(16384, 512));
assert_eq!(relay_config.max_circuits, 16384);
assert_eq!(relay_config.max_circuits_per_peer, 512);
}

#[test]
fn zero_max_res_per_peer_uses_default_per_ip_capacity() {
// max_res_per_peer = 0 must not panic (NonZeroU32 fallback path) and
Expand Down
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