Net::DNS::Nameserver
Net::DNS::Nameserver(User Contributed Perl DocumentatiNet::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.
NotifyHandler Reference to reply-handling
subroutine for queries with
opdcode NS_NOTIFY (RFC1996)
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 inter-
faces on IPv6 and IPv4);
The ReplyHandler subroutine is passed the query name, query class,
query type and optionally an argument containing the peerhost, the
incoming query, and the name of the incomming socket (sockethost). 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 it may also contain a headermaks 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 lis-
ten 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.
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, $peerhost,$query,$conn) = @_;
my ($rcode, @ans, @auth, @add);
print "Received query from $peerhost to ". $conn->{"sockhost"}. "\n";
$query->print;
if ($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 clos-
est 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) 2005-2007 O.M, Kolkman, RIPE NCC.
Portions Copyright (c) 2005 Robert Martin-Legene.
All rights reserved. This program is free software; you may redis-
tribute 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 2009-01-26 Net::DNS::Nameserver(3)
