As part of a project I've written a very simplistic DNS server whose only purpose is to resolve queries for the zone it serves, and to store the IP addresses of the server that made the query.
I've noticed that if I use dig, my DNS server gets queried multiple times - sometimes from the same IP address. Why does this happen? Is it due to the unreliable nature of UDP?
For example, here's a dig reply I made:
C:\Data>dig xyz.dns.example.com
; <<>> DiG 9.10.4-P2 <<>> xyz.dns.example.com
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 2539
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;xyz.dns.example.com. IN A
;; ANSWER SECTION:
xyz.dns.example.com. 12321 IN A 50.16.166.175
;; Query time: 224 msec
;; SERVER: 192.168.1.1#53(192.168.1.1)
;; WHEN: Thu Aug 11 15:07:42 Eastern Daylight Time 2016
;; MSG SIZE rcvd: 77
In this example, the zone file for example.com has an NS record for dns.example.com which is where my simplistic DNS server runs. Fror this one query, my server was called 4 times from 2 different IP addresses.
I also noticed that I'm supposedly returning an "Additional" record, but the data I return in bytes 10 and 11 are clearly 0. Could this be causing a problem?
