Caching of negative responses if the returned query type is different from queried type. #832

alpominth · 2023-01-17T14:15:45Z

alpominth
Jan 17, 2023

When using dig to query a domain that has no support from queried type, a SOA response is gotten:

$ time dig @127.0.0.1 -p 53 -t PTR t.co

; <<>> DiG 9.18.4-2ubuntu2-Ubuntu <<>> @127.0.0.1 -p 53 -t PTR t.co
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 33069
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;t.co.                          IN      PTR

;; AUTHORITY SECTION:
t.co.                   28      IN      SOA     ns1.p26.dynect.net. ops.twitter.com. 2538 3600 600 604800 60

;; Query time: 233 msec
;; SERVER: 127.0.0.1#53(127.0.0.1) (UDP)
;; WHEN: Tue Jan 17 09:13:01 EST 2023
;; MSG SIZE  rcvd: 102


real    0m0.252s
user    0m0.003s
sys     0m0.005s

Blocky cache this negative answer, but it doesn't cache the returned type (SOA) when querying the cache:

$ time dig @127.0.0.1 -p 53 -t PTR t.co

; <<>> DiG 9.18.4-2ubuntu2-Ubuntu <<>> @127.0.0.1 -p 53 -t PTR t.co
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 59575
;; flags: qr rd ra; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;t.co.                          IN      PTR

;; Query time: 0 msec
;; SERVER: 127.0.0.1#53(127.0.0.1) (UDP)
;; WHEN: Tue Jan 17 09:13:47 EST 2023
;; MSG SIZE  rcvd: 22


real    0m0.019s
user    0m0.002s
sys     0m0.006s

I think Blocky should cache the returned query type even if it is different from the queried type.