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Net::DNS::Nameserver(3)User Contributed Perl DocumentatioNnet::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.

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my $ns = Net::DNS::Nameserver->new(

LocalAddr => "10.1.2.3", LocalPort => "5353", ReplyHandler => \&replyhandler, Verbose => 1 );

my $ns = Net::DNS::Nameserver->new(

LocalAddr => ['::1' , '127.0.0.1' ], LocalPort => "5353", ReplyHandler => \&replyhandler, Verbose => 1 ); Creates a nameserver object. Attributes are: LocalAddr IP address on which to listen. Defaults to INADDRANY. 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.

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$ns->mainloop;

Start accepting queries. Calling mainloop never returns. llooooppoonnccee

$ns->looponce( [TIMEOUTINSECONDS] );

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, looponce 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 looponce 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 looponce() 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 "looponce" twice.

A code fragment like: $ns->looponce(10);

while( $ns->getopentcp() ){ $ns->looponce(0);

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

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 => \&replyhandler, Verbose => 1, ) || die "couldn't create nameserver object\n";

$ns->mainloop;

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 INADDRANY (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 INADDRANY 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.