DNS filter

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question:

Hi,

I am trying to make DNS filter where I can send 'A' entry for some of the requested domains and redirect the request to a real DNS server if no domain matched.

I am stucked with the fact that tools like 'nslookup' send un-understandable characters to my perl script so I am unable to match anything and stopped working on the code until I get some help.

Here is my code:

use IO::Socket;
my $server = IO::Socket::INET->new(
            Proto      => 'udp',
            LocalPort => 53,            
            );

die "Couldn't setup server: $@" unless $server;

while ( $server->recv(my $data , 1024, my $flag ) ) {
    print "Got: $data\n";
}
[download]

Comment on DNS filter Download Code

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Re: DNS filter by Corion (Patriarch) on Feb 09, 2010 at 20:13 UTC
Have you looked at the modules for handling DNS packets on the CPAN? Especially Net::DNS::Packet and POE::Component::Server::DNS look promising.	[reply]
Re^2: DNS filter by Anonymous Monk on Feb 10, 2010 at 00:07 UTC
Both appears to be complicated ... I have tried both of them but could not get what I need. Any idea why the dns request appears scrambled ? For example querying msn.com giving this output. `�smsncom` [download] Is there any guide for implementing this, I looked at the source of the modules you mentioned and both are full of pack/unpack ...etc I do not want to copy and paste code all over ... I want to understand how it works.	[reply] [d/l]
Re^3: DNS filter by gman (Friar) on Feb 10, 2010 at 02:20 UTC
DNS is BINARY not ASCI, This site explains it http://www.firewall.cx/dns-query-format.php. But I think a better source is the DNS and BIND book. Your set up sounds like you just need a BIND server with a forwarder address, you can add your own zones with 'A' records as you see fit.	[reply]