Net::DNS::Nameserver - DNS server class

CWuse Net::DNS::Nameserver;

Instances of the CWNet::DNS::Nameserver class represent simple DNS server objects. See EXAMPLE for an example.

 my $ns = Net::DNS::Nameserver->new(
        LocalAddr        => "10.1.2.3",
        LocalPort        => "5353",
        ReplyHandler => \&reply_handler,
        Verbose          => 1
 );

 my $ns = Net::DNS::Nameserver->new(
        LocalAddr        => ['::1' , '127.0.0.1' ],
        LocalPort        => "5353",
        ReplyHandler => \&reply_handler,
        Verbose          => 1
 );

Creates a nameserver object. Attributes are:

  LocalAddr             IP address on which to listen.  Defaults to INADDR_ANY.
  LocalPort             Port on which to listen.        Defaults to 53.
  ReplyHandler          Reference to reply-handling 
                        subroutine                      Required.
  Verbose               Print info about received 
                        queries.                        Defaults to 0 (off).

The LocalAddr attribute may alternatively be specified as a list of IP addresses to liten to.

If IO::Socket::INET6 and Socket6 are available on the system you can also list IPv6 addresses and the default is '0' (listen on all interfaces on IPv6 and IPv4);

The ReplyHandler subroutine is passed the query name, query class, query type and optionally an argument containing header bit settings (see below). It must return the response code and references to the answer, authority, and additional sections of the response. Common response codes are:

  NOERROR       No error
  FORMERR       Format error
  SERVFAIL      Server failure
  NXDOMAIN      Non-existent domain (name doesn't exist)
  NOTIMP        Not implemented
  REFUSED       Query refused

For advanced usage there is an optional argument containing an hashref with the settings for the CWaa, CWra, and CWad header bits. The argument is of the form CW{ ad => 1, aa => 0, ra => 1 }.

See RFC 1035 and the IANA dns-parameters file for more information:

  ftp://ftp.rfc-editor.org/in-notes/rfc1035.txt
  http://www.isi.edu/in-notes/iana/assignments/dns-parameters

The nameserver will listen for both UDP and TCP connections. On Unix-like systems, the program will probably have to run as root to listen on the default port, 53. A non-privileged user should be able to listen on ports 1024 and higher.

Returns a Net::DNS::Nameserver object, or undef if the object couldn't be created.

See EXAMPLE for an example.

        $ns->main_loop;

Start accepting queries.

The following example will listen on port 5353 and respond to all queries for A records with the IP address 10.1.2.3. All other queries will be answered with NXDOMAIN. Authority and additional sections are left empty. The CW$peerhost variable catches the IP address of the peer host, so that additional filtering on its basis may be applied.

 #!/usr/bin/perl

 use Net::DNS;
 use strict;
 use warnings;

 sub reply_handler {
         my ($qname, $qclass, $qtype, $peerhost) = @_;
         my ($rcode, @ans, @auth, @add);

         if ($qtype eq "A") {
                 my ($ttl, $rdata) = (3600, "10.1.2.3");
                 push @ans, Net::DNS::RR->new("$qname $ttl $qclass $qtype $rdata");
                 $rcode = "NOERROR";
         } else {
         $rcode = "NXDOMAIN";
         }

         # mark the answer as authoritive (by setting the 'aa' flag
         return ($rcode, \@ans, \@auth, \@add, { aa => 1 });
 }

 my $ns = Net::DNS::Nameserver->new(
     LocalPort    => 5353,
     ReplyHandler => \&reply_handler,
     Verbose      => 1,
 ) || die "couldn't create nameserver object\n";

 $ns->main_loop;

Net::DNS::Nameserver objects can handle only one query at a time.

Limitations in perl 5.8.6 makes it impossible to guarantee that replies to UDP queries from Net::DNS::Nameserver are sent from the IP-address they were received on. This is a problem for machines with multiple IP-addresses and causes violation of RFC2181 section 4.

Copyright (c) 1997-2002 Michael Fuhr.

Portions Copyright (c) 2002-2004 Chris Reinhardt.

Portions Copyright (c) 2005 O.M, Kolkman, RIPE NCC.

All rights reserved. This program is free software; you may redistribute it and/or modify it under the same terms as Perl itself.

perl(1), Net::DNS, Net::DNS::Resolver, Net::DNS::Packet, Net::DNS::Update, Net::DNS::Header, Net::DNS::Question, Net::DNS::RR, RFC 1035