The ~30-signature hand-rolled p0f-lite table in decnet/sniffer/p0f.py
misses most real-world attackers (yesterday's SLOW SCAN being a
textbook case — 9 hours of events, 19 hits, os_guess = NULL). The
375-sig vendored p0f v2 DB was already there; this commit actually
calls it.
New resolution chain in sniffer_rollup:
1. Enabled OS-fingerprint providers (p0f-v2 default, via
DECNET_OSFP_PROVIDERS) tried in declared order. Provider with
highest-confidence match across all enabled sources wins.
2. Modal os_guess label from the sniffer's hand-rolled p0f.py.
Kept as fallback because v2's DB predates post-2006 kernels.
3. TTL bucket (linux / windows / embedded). Coarse but never wrong.
Wiring details:
- _match_via_osfp_providers: never raises — factory / provider
failures collapse to None and the chain falls through to the
old modal-label / TTL path. A corrupt .fp file or misconfigured
DECNET_OSFP_PROVIDERS must never wedge a profile rebuild.
- tcp_fp_context tracks whether the LATEST tcp_fp snapshot came
from a passive SYN ('syn' → p0f.fp) or an active prober probe
('synack' → p0fa.fp). Routes to the right sig list.
- initial-TTL normalisation via decnet.sniffer.p0f.initial_ttl.
Observation's TTL may be N hops below the OS's initial; v2
signatures match on the canonical bucket.
Soft-field semantics on Signature.score(): df and total_len are now
skip-checked when the observation is missing them. Sniffer doesn't
currently emit either SD field; a literal-constraint sig
shouldn't hard-reject a match solely because of upstream
incompleteness. Hard fields (window, ttl, options_sig, quirks)
still hard-reject on absent/mismatched input — those are the real
discriminators. Promote df / total_len back to hard the moment the
sniffer starts emitting them.
+2 integration tests on TestSnifferRollup, +2 soft-field tests on
test_signature. Full regression: 166 tests across tests/prober/osfp
+ tests/profiler all green.
anti
ec1079e78b