ANSWER section not empty on SERVFAIL
In some cases, the ANSWER section contains (unvalidated) data while the request ends with SERVFAIL.
In my specific conditions, the issue seems reproducible when:
- cache is clear
- IPv6 isn't available, but isn't turned off with net.ipv6
- server selection chooses specific servers (and typically chooses the non-functioning IPv6 ones)
$ kdig @::1 -p 5553 +timeout=16 +edns signotincepted.bad-dnssec.wb.sidnlabs.nl
;; ->>HEADER<<- opcode: QUERY; status: SERVFAIL; id: 6998
;; Flags: qr rd ra; QUERY: 1; ANSWER: 1; AUTHORITY: 0; ADDITIONAL: 1
;; EDNS PSEUDOSECTION:
;; Version: 0; flags: ; UDP size: 1232 B; ext-rcode: NOERROR
;; QUESTION SECTION:
;; signotincepted.bad-dnssec.wb.sidnlabs.nl. IN A
;; ANSWER SECTION:
signotincepted.bad-dnssec.wb.sidnlabs.nl. 3600 IN A 94.198.159.39
;; Received 85 B
;; Time 2021-11-04 10:45:32 CET
;; From ::1@5553(UDP) in 10027.7 ms
See attached log.txt