The FSP XK rekey handshake has a race condition where the initiator
can cut over (K-bit flip) and send data encrypted with the new session
before msg3 reaches the responder. The responder has no pending session
yet, so K-bit detection fails and packets are dropped.
Defer FSP initiator cutover by 2 seconds after handshake completion
(FSP_CUTOVER_DELAY_MS) to give msg3 time to traverse the mesh. FMP
(IK, 2 messages) is unaffected since the responder completes during
msg1 processing.
Also fix MMP metric corruption after rekey cutover: the new session
starts with counter 0 but MMP state carries highest_counter and
GapTracker.expected_next from the old session, producing false
reorder counts, jitter spikes, and invalid OWD trends. Add
reset_for_rekey() methods that clear counter-dependent state while
preserving RTT estimates.
Additional fixes:
- Remove stale peers_by_index entry on abandon_rekey error path
- Replace redundant peers_by_index inserts with debug assertions
verifying the pre-registration invariant
- Tighten rekey integration test to zero tolerance (was 4 failures)
Add a Unix domain socket interface for querying node state at runtime.
A spawned tokio task accepts connections and communicates with the main
event loop via mpsc/oneshot channels, keeping all Node access
single-threaded.
Includes:
- src/control/ module with socket lifecycle, JSON protocol, and 11
query handlers (status, peers, links, tree, sessions, bloom, mmp,
cache, connections, transports, routing)
- Separate fipsctl binary for CLI queries (fipsctl show <command>)
- ControlConfig in node configuration (enabled, socket_path)
- Integration into the main select! event loop
Johnathan Corgan