how to create dns request packets

masood_gandhi · 10-26-2004, 07:23 AM

hi everybody,
i m working on project related to dns
and i m the new to this
can anyone pls tell me how to create
dns request packets and any related info
about it
i will appreciate your help
thanx

n3tw0rk · 10-26-2004, 07:48 AM

You need to study the DNS protocol and learn how to do network programming. DNS uses the UDP (User Datagram Protocol) which means you would have to create a UDP socket and play with it

.... there is a lot of information available on how to do network programming. Beej's guide is a good way to start, visit http://www.ecst.csuchico.edu/~beej/guide/net/ , for DNS visit http://www.freesoft.org/CIE/Topics/77.htm and also study the related RFCs.

scowles · 10-26-2004, 07:49 AM

The "dig" command will create a DNS query/packet to a particular server. Example:

dig @xx.xx.xx.xx www.mydomain.com

Where xx.xx.xx.xx is the IP address of the DNS server.

If your are wanting to create a DNS query/packet in code, then take a look at:

man resolver
man gethostbyname

masood_gandhi · 10-26-2004, 09:41 AM

Thanx,
actually i have read DNS protocol but didnt know the exact packet formate of the request

masood_gandhi · 10-27-2004, 04:42 AM

hello everybody,
thanx for the earlier help but i want to know
what happens on dns server side when it recieves the request through dig command on client side.

scowles · 10-27-2004, 07:07 AM

The DNS server would try to answer the query. If the answer to the query is already cached, then it would simply return the answer to the requesting system (dig). If the answer is not cached, then it would start a recursive query (starting at the root name servers) until it got the answer to be returned. FWIW: To visually see a recursive query, type: dig +trace www.mydomain.com

If you want to see the actual packets that are generated by dig or your DNS server, then use a program like tcpdump or ethereal.