Tools like fpdns send OPCODE=IQUERY/STATUS/NOTIFY/UPDATE or set the reserved
Z bit to fingerprint resolver behaviour. Previously all these were parsed as
standard queries with no signal.
- opcode!=0 → fingerprint_probe probe=opcode_<name>, NOTIMP response;
fired before qdcount check so qdcount=0 UPDATE packets are still caught.
- Z bit set OR (AD+CD without RD) → fingerprint_probe probe=header_flags;
AD alone with RD is ignored to avoid tagging DNSSEC-aware stubs.
- Both variants contribute to recon_burst.
anti
4dadeb9aba