Complete TCP connection tracking state machine:
NEW TRANSITIONS (mirrors Linux nf_conntrack_proto_tcp.c):
- RST from either direction → Close (10s timeout, ConnState::New)
- Established + FIN (either dir) → FinWait (120s timeout)
- FinWait + FIN (other dir) → TimeWait (120s timeout)
- TimeWait extends timeout on any traffic (125s idle for safe
delayed-ACK arrival)
PRESERVED TRANSITIONS (from original code):
- None → SynSent (on original SYN) — unchanged
- SynSent → SynRecv (on reply SYN-ACK) — unchanged
- SynRecv → Established (on reply ACK) — unchanged
NEW HELPERS:
- tcp_flags(): extract TCP flags byte from packet
- is_fin(): check FIN bit
- is_rst(): check RST bit
NEW TESTS:
- rst_forces_state_to_new: RST resets conn state to New
(entry stays 10s for lingering cleanup)
- fin_transitions_established_to_timewait: double-FIN
transition through FinWait → TimeWait
FIXED BUGS:
- advance_entry_state never processed FIN/RST/TimeWait, so
connections stayed Established for 5 days after actual close.
Now: FinWait after FIN, TimeWait after both FINs, Close on RST.
All 31 tests pass.
Red Bear OS
b27515d583