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Wed, 30 Jul 2008

Simple DNS server/resolver.

Exact time to hack a DNS server is a middle of the night: 3 A.M. here and I've just completed initial draft of the trivial DNS server, which is only capable to receive a datagram from predefined port, parse it, fill a reply for static "IN A" record (I think I will add a config file), this record is placed into 'answer' and 'additional' resource record sections, then the whole request is being sent back to the client.

That's how it looks for standard UNIX dig command:

$ dig @localhost -p 1025 www.google.com
;; Warning: query response not set

; <<>> DiG 9.4.2-P1 <<>> @localhost -p 1025 www.google.com
; (1 server found)
;; global options:  printcmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 51486
;; flags: rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; WARNING: recursion requested but not available

;; QUESTION SECTION:
;www.google.com.			IN	A

;; ANSWER SECTION:
www.google.com.		123456	IN	A	195.178.208.66

;; ADDITIONAL SECTION:
www.google.com.		123456	IN	A	195.178.208.66

;; Query time: 15 msec
;; SERVER: 127.0.0.1#1025(127.0.0.1)
;; WHEN: Wed Jul 30 02:56:23 2008
;; MSG SIZE  rcvd: 64

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