Implement synlimit = "pf" for PF-based firewalls using per-listener source tracking rules in a Telemt-owned anchor.
PF evaluates max-src-conn-rate through source tracking when creating
tates for completed TCP connections. Telemt installs a rate-limited pass
rule followed by a reject fallback rule in the listener anchor:
- under-limit new connections create PF state and pass;
- over-limit new connections fall through to block return-rst;
- access resumes automatically when the source rate drops below the configured window.
Keep Linux iptables/nftables behavior unchanged.
PF maps synlimit_hitcount / synlimit_seconds to max-src-conn-rate and intentionally has
no direct equivalent for Linux-only burst/hashlimit knobs.
Vladimir Grebenshchikov