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Net::DNS::Nameserver(3)              User Contributed Perl Documentation             Net::DNS::Nameserver(3)



NAME
       Net::DNS::Nameserver - DNS server class

SYNOPSIS
       "use Net::DNS::Nameserver;"

DESCRIPTION
       Instances of the "Net::DNS::Nameserver" class represent DNS server objects.  See "EXAMPLE" for an
       example.

METHODS
       new

        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 listen 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
       "aa", "ra", and "ad" header bits. The argument is of the form "{ 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.

       main_loop

               $ns->main_loop;

       Start accepting queries. Calling main_loop never returns.

       loop_once

               $ns->loop_once( [TIMEOUT_IN_SECONDS] );

       Start accepting queries, but returns. If called without a parameter, the call will not return until a
       request has been received (and replied to). If called with a number, that number specifies how many
       seconds (even fractional) to maximum wait before returning. If called with 0 it will return
       immediately unless there's something to do.

       Handling a request and replying obviously depends on the speed of ReplyHandler. Assuming ReplyHandler
       is super fast, loop_once should spend just a fraction of a second, if called with a timeout value of
       0 seconds.  One exception is when an AXFR has requested a huge amount of data that the OS is not
       ready to receive in full. In that case, it will keep running through a loop (while servicing new
       requests) until the reply has been sent.

       In case loop_once accepted a TCP connection it will immediatly check if there is data to be read from
       the socket. If not it will return and you will have to call loop_once() again to check if there is
       any data waiting on the socket to be processed. In most cases you will have to count on calling
       "loop_once" twice.

       A code fragment like:      $ns->loop_once(10);
               while( $ns->get_open_tcp() ){            $ns->loop_once(0);      }

       Would wait for 10 seconds for the initial connection and would then process all TCP sockets until
       none is left.

       get_open_tcp

       In scalar context returns the number of TCP connections for which state is maintained. In array
       context it returns IO::Socket objects, these could be useful for troubleshooting but be careful using
       them.

EXAMPLE
       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 $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::Nameserver;
        use strict;
        use warnings;

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

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

BUGS
       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.  Thus a UDP socket
       created listening to INADDR_ANY (all available IP-addresses) will reply not necessarily with the
       source address being the one to which the request was sent, but rather with the address that the
       operating system choses. This is also often called "the closest address". This should really only be
       a problem on a server which has more than one IP-address (besides localhost - any experience with
       IPv6 complications here, would be nice). If this is a problem for you, a work-around would be to not
       listen to INADDR_ANY but to specify each address that you want this module to listen on. A seperate
       set of sockets will then be created for each IP-address.

COPYRIGHT
       Copyright (c) 1997-2002 Michael Fuhr.

       Portions Copyright (c) 2002-2004 Chris Reinhardt.

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

       Portions Copyright (c) 2005 Robert Martin-Legene.

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

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



perl v5.8.8                                      2007-06-21                          Net::DNS::Nameserver(3)