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Johnathan Corgan
bf117df0ca
Implement periodic full rekey at both protocol layers using fresh DH key exchanges. Uses the existing K-bit flag (FLAG_KEY_EPOCH / FSP_FLAG_K) to coordinate cutover between peers. FMP layer (IK pattern): - ActivePeer gains rekey state: pending/previous sessions, K-bit epoch tracking, drain window, dampening timer - Handshake state stored on ActivePeer with msg1 sent on existing link - Encrypted frame handler detects K-bit flips, promotes pending sessions, falls back to previous session during drain - Handshake handlers distinguish rekey from new connections using addr_to_link lookup with identity-based fallback - Free all session indices (current, rekey, pending, previous) on peer removal FSP layer (XK pattern): - SessionEntry gains parallel rekey fields with XK-specific state for the 3-message handshake - Route availability check before FSP rekey initiation - Encrypted session handler adds K-bit flip detection and dual-session decrypt fallback - SessionSetup/Ack/Msg3 handlers extended for rekey paths Defense-in-depth: - Consecutive decryption failure detector (threshold=20) triggers forced peer removal instead of waiting for link-dead timeout - Identity-based rekey detection as fallback when addr_to_link doesn't match (e.g., TCP ephemeral ports) Configuration: RekeyConfig with enabled flag, after_secs (default 120), and after_messages (default 65536) thresholds. Logging: info for successful K-bit cutover completions, warn for failures, debug for intermediate handshake steps, trace for routine operations (resends, drain cleanup). Rekey lifecycle: 1. Timer/counter fires -> initiator starts new handshake 2. Old session continues handling traffic during handshake 3. Handshake completes -> initiator cuts over, flips K-bit 4. Responder sees flipped K-bit -> promotes new session 5. Both keep old session for 10s drain window 6. After drain, old session discarded Integration test: Docker-based multi-phase test exercising both FMP and FSP rekey with aggressive timers (35s). Verifies connectivity across all 20 directed pairs survives two consecutive rekey cycles. Includes rekey topology, docker-compose profile, and CI matrix entry. Increase ping test convergence wait from 3s to 5s for CI reliability.