package Net::DNS;
#
# $Id: DNS.pm 1374 2015-07-06 12:19:47Z willem $
#
use vars qw($VERSION $SVNVERSION);
$VERSION = '1.01';
$SVNVERSION = (qw$LastChangedRevision: 1374 $)[1];
=head1 NAME
Net::DNS - Perl Interface to the Domain Name System
=head1 SYNOPSIS
use Net::DNS;
=head1 DESCRIPTION
Net::DNS is a collection of Perl modules that act as a Domain Name System
(DNS) resolver. It allows the programmer to perform DNS queries that are
beyond the capabilities of "gethostbyname" and "gethostbyaddr".
The programmer should be somewhat familiar with the format of a DNS packet
and its various sections. See RFC 1035 or DNS and BIND (Albitz & Liu) for
details.
=cut
use 5.004_04;
use strict;
use integer;
use base qw(Exporter);
use vars qw(@EXPORT);
@EXPORT = qw(SEQUENTIAL UNIXTIME YYYYMMDDxx
yxrrset nxrrset yxdomain nxdomain rr_add rr_del
mx rrsort);
use Net::DNS::RR;
use Net::DNS::Packet;
use Net::DNS::Update;
use Net::DNS::Resolver;
sub version { $VERSION; }
#
# mx()
#
# Usage:
# @mx = mx('example.com');
# @mx = mx($res, 'example.com');
#
sub mx {
my ($arg1) = @_;
my $res = ref($arg1) ? shift : new Net::DNS::Resolver();
my ( $name, @class ) = @_;
my $ans = $res->query( $name, 'MX', @class );
# This construct is best read backwards.
#
# First we take the answer section of the packet.
# Then we take just the MX records from that list
# Then we sort the list by preference
# We do this into an array to force list context.
# Then we return the list.
my @list = sort { $a->preference <=> $b->preference }
grep { $_->type eq 'MX' } $ans->answer
if $ans;
return @list;
}
#
# rrsort()
#
# Usage:
# @prioritysorted = rrsort( "SRV", "priority", @rr_array );
#
sub rrsort {
my $rrtype = uc shift;
my @empty;
my ( $attribute, @rr_array ) = @_;
return undef unless defined $attribute; # attribute not specified
( @rr_array, $attribute ) = @_ if ref($attribute) =~ /^Net::DNS::RR/;
my @extracted_rr = grep $_->type eq $rrtype, @rr_array;
return @empty unless scalar @extracted_rr;
my $func = "Net::DNS::RR::$rrtype"->get_rrsort_func($attribute);
my @sorted = sort $func @extracted_rr;
return @sorted;
}
#
# Auxiliary functions to support policy-driven zone serial numbering.
#
# $successor = $soa->serial(SEQUENTIAL);
# $successor = $soa->serial(UNIXTIME);
# $successor = $soa->serial(YYYYMMDDxx);
#
sub SEQUENTIAL {undef}
sub UNIXTIME { return CORE::time; }
sub YYYYMMDDxx {
my ( $dd, $mm, $yy ) = (localtime)[3 .. 5];
return 1900010000 + sprintf '%d%0.2d%0.2d00', $yy, $mm, $dd;
}
#
# Auxiliary functions to support dynamic update.
#
sub yxrrset {
my $rr = new Net::DNS::RR(shift);
$rr->ttl(0);
$rr->class('ANY') unless $rr->rdata;
return $rr;
}
sub nxrrset {
my $rr = new Net::DNS::RR(shift);
return new Net::DNS::RR(
name => $rr->name,
type => $rr->type,
class => 'NONE'
);
}
sub yxdomain {
my ($domain) = split /\s+/, shift;
return new Net::DNS::RR("$domain ANY ANY");
}
sub nxdomain {
my ($domain) = split /\s+/, shift;
return new Net::DNS::RR("$domain NONE ANY");
}
sub rr_add {
my $rr = new Net::DNS::RR(shift);
$rr->{ttl} = 86400 unless defined( $rr->{ttl} );
return $rr;
}
sub rr_del {
my ( $head, @tail ) = split /\s+/, shift;
my $rr = new Net::DNS::RR( scalar @tail ? "$head @tail" : "$head ANY" );
$rr->ttl(0);
$rr->class( $rr->rdata ? 'NONE' : 'ANY' );
return $rr;
}
1;
__END__
=head2 Resolver Objects
A resolver object is an instance of the L<Net::DNS::Resolver> class.
A program can have multiple resolver objects, each maintaining its
own state information such as the nameservers to be queried, whether
recursion is desired, etc.
=head2 Packet Objects
L<Net::DNS::Resolver> queries return L<Net::DNS::Packet> objects.
Packet objects have five sections:
=over 3
=item *
The header section, a L<Net::DNS::Header> object.
=item *
The question section, a list of L<Net::DNS::Question> objects.
=item *
The answer section, a list of L<Net::DNS::RR> objects.
=item *
The authority section, a list of L<Net::DNS::RR> objects.
=item *
The additional section, a list of L<Net::DNS::RR> objects.
=back
=head2 Update Objects
L<Net::DNS::Update> is a subclass of L<Net::DNS::Packet>
used to create dynamic update requests.
=head2 Header Objects
L<Net::DNS::Header> objects represent the header
section of a DNS packet.
=head2 Question Objects
L<Net::DNS::Question> objects represent the content of the question
section of a DNS packet.
=head2 RR Objects
L<Net::DNS::RR> is the base class for DNS resource record (RR) objects
in the answer, authority, and additional sections of a DNS packet.
Do not assume that RR objects will be of the type requested.
The type of an RR object must be checked before calling any methods.
=head1 METHODS
See the manual pages listed above for other class-specific methods.
=head2 version
print Net::DNS->version, "\n";
Returns the version of Net::DNS.
=head2 mx
# Use a default resolver -- can not get an error string this way.
use Net::DNS;
my @mx = mx("example.com");
# Use your own resolver object.
use Net::DNS;
my $res = Net::DNS::Resolver->new;
my @mx = mx($res, "example.com");
Returns a list of L<Net::DNS::RR::MX> objects representing the MX
records for the specified name.
The list will be sorted by preference.
Returns an empty list if the query failed or no MX record was found.
This method does not look up A records; it only performs MX queries.
See L</EXAMPLES> for a more complete example.
=head1 Dynamic DNS Update Support
The Net::DNS module provides auxiliary functions which support
dynamic DNS update requests.
=head2 yxrrset
Use this method to add an "RRset exists" prerequisite to a dynamic
update packet. There are two forms, value-independent and
value-dependent:
# RRset exists (value-independent)
$update->push(pre => yxrrset("host.example.com A"));
Meaning: At least one RR with the specified name and type must
exist.
# RRset exists (value-dependent)
$packet->push(pre => yxrrset("host.example.com A 10.1.2.3"));
Meaning: At least one RR with the specified name and type must
exist and must have matching data.
Returns a C<Net::DNS::RR> object or C<undef> if the object could not
be created.
=head2 nxrrset
Use this method to add an "RRset does not exist" prerequisite to
a dynamic update packet.
$packet->push(pre => nxrrset("host.example.com A"));
Meaning: No RRs with the specified name and type can exist.
Returns a C<Net::DNS::RR> object or C<undef> if the object could not
be created.
=head2 yxdomain
Use this method to add a "name is in use" prerequisite to a dynamic
update packet.
$packet->push(pre => yxdomain("host.example.com"));
Meaning: At least one RR with the specified name must exist.
Returns a C<Net::DNS::RR> object or C<undef> if the object could not
be created.
=head2 nxdomain
Use this method to add a "name is not in use" prerequisite to a
dynamic update packet.
$packet->push(pre => nxdomain("host.example.com"));
Meaning: No RR with the specified name can exist.
Returns a C<Net::DNS::RR> object or C<undef> if the object could not
be created.
=head2 rr_add
Use this method to add RRs to a zone.
$packet->push(update => rr_add("host.example.com A 10.1.2.3"));
Meaning: Add this RR to the zone.
RR objects created by this method should be added to the "update"
section of a dynamic update packet. The TTL defaults to 86400
seconds (24 hours) if not specified.
Returns a C<Net::DNS::RR> object or C<undef> if the object could not
be created.
=head2 rr_del
Use this method to delete RRs from a zone. There are three forms:
delete an RRset, delete all RRsets, and delete an RR.
# Delete an RRset.
$packet->push(update => rr_del("host.example.com A"));
Meaning: Delete all RRs having the specified name and type.
# Delete all RRsets.
$packet->push(update => rr_del("host.example.com"));
Meaning: Delete all RRs having the specified name.
# Delete an RR.
$packet->push(update => rr_del("host.example.com A 10.1.2.3"));
Meaning: Delete all RRs having the specified name, type, and data.
RR objects created by this method should be added to the "update"
section of a dynamic update packet.
Returns a C<Net::DNS::RR> object or C<undef> if the object could not
be created.
=head1 Zone Serial Number Management
The Net::DNS module provides auxiliary functions which support
policy-driven zone serial numbering regimes.
=head2 SEQUENTIAL
$successor = $soa->serial( SEQUENTIAL );
The existing serial number is incremented modulo 2**32.
=head2 UNIXTIME
$successor = $soa->serial( UNIXTIME );
The Unix time scale will be used as the basis for zone serial
numbering. The serial number will be incremented if the time
elapsed since the previous update is less than one second.
=head2 YYYYMMDDxx
$successor = $soa->serial( YYYYMMDDxx );
The 32 bit value returned by the auxiliary YYYYMMDDxx() function
will be used as the base for the date-coded zone serial number.
Serial number increments must be limited to 100 per day for the
date information to remain useful.
=head1 Sorting of RR arrays
As of version 0.55 there is functionality to help you sort RR arrays.
rrsort() is the function that is available to do the sorting. In most
cases rrsort() will give you the answer that you want but you can specify
your own sorting method by using the Net::DNS::RR::FOO->set_rrsort_func()
class method. See Net::DNS::RR for details.
=head2 rrsort()
use Net::DNS qw(rrsort);
@sorted = rrsort( $rrtype, $attribute, @rr_array );
rrsort() selects all RRs from the input array that are of the type defined
by the first argument. Those RRs are sorted based on the attribute that is
specified as second argument.
There are a number of RRs for which the sorting function is defined in the
code. The function can be overidden using the set_rrsort_func() method.
For instance:
@prioritysorted = rrsort( "SRV", "priority", @rr_array );
returns the SRV records sorted from lowest to highest priority and for
equal priorities from highest to lowest weight.
If the function does not exist then a numerical sort on the attribute
value is performed.
@portsorted = rrsort( "SRV", "port", @rr_array );
If the attribute is not defined then either the default_sort() function or
"canonical sorting" (as defined by DNSSEC) will be used.
rrsort() returns a sorted array containing only elements of the specified
RR type or undef.
rrsort() returns undef when arguments are incorrect.
=head1 EXAMPLES
The following examples show how to use the C<Net::DNS> modules.
See the other manual pages and the demo scripts included with the
source code for additional examples.
See the C<Net::DNS::Update> manual page for an example of performing
dynamic updates.
=head2 Look up host addresses.
use Net::DNS;
my $res = Net::DNS::Resolver->new;
my $reply = $res->search("host.example.com");
if ($reply) {
foreach my $rr ($reply->answer) {
next unless $rr->type eq "A";
print $rr->address, "\n";
}
} else {
warn "query failed: ", $res->errorstring, "\n";
}
=head2 Find the nameservers for a domain.
use Net::DNS;
my $res = Net::DNS::Resolver->new;
my $reply = $res->query("example.com", "NS");
if ($reply) {
foreach $rr (grep { $_->type eq 'NS' } $reply->answer) {
print $rr->nsdname, "\n";
}
}
else {
warn "query failed: ", $res->errorstring, "\n";
}
=head2 Find the MX records for a domain.
use Net::DNS;
my $name = "example.com";
my $res = Net::DNS::Resolver->new;
my @mx = mx($res, $name);
if (@mx) {
foreach $rr (@mx) {
print $rr->preference, " ", $rr->exchange, "\n";
}
} else {
warn "Can not find MX records for $name: ", $res->errorstring, "\n";
}
=head2 Print domain SOA record in zone file format.
use Net::DNS;
my $res = Net::DNS::Resolver->new;
my $reply = $res->query("example.com", "SOA");
if ($reply) {
($reply->answer)[0]->print;
} else {
print "query failed: ", $res->errorstring, "\n";
}
=head2 Perform a zone transfer and print all the records.
use Net::DNS;
my $res = Net::DNS::Resolver->new;
$res->nameservers("ns.example.com");
my @zone = $res->axfr("example.com");
foreach $rr (@zone) {
$rr->print;
}
=head2 Perform a background query for the answer.
use Net::DNS;
my $res = Net::DNS::Resolver->new;
my $socket = $res->bgsend("host.example.com");
until ($res->bgisready($socket)) {
# do some work here while waiting for the answer
# ...and some more here
}
my $packet = $res->bgread($socket);
$packet->print;
=head2 Send a background query using select to detect completion
use Net::DNS;
use IO::Select;
my $timeout = 5;
my $res = Net::DNS::Resolver->new;
my $bgsock = $res->bgsend("host.example.com");
my $sel = IO::Select->new($bgsock);
# Add more sockets to $sel if desired.
my @ready = $sel->can_read($timeout);
if (@ready) {
foreach my $sock (@ready) {
if ($sock == $bgsock) {
my $packet = $res->bgread($bgsock);
$packet->print;
$bgsock = undef;
}
# Check for the other sockets.
$sel->remove($sock);
$sock = undef;
}
} else {
warn "timed out after $timeout seconds\n";
}
=head1 BUGS
C<Net::DNS> is slow.
For other items to be fixed, or if you discover a bug in this
distribution please use the CPAN bug reporting system.
=head1 COPYRIGHT
Copyright (c)1997-2000 Michael Fuhr.
Portions Copyright (c)2002,2003 Chris Reinhardt.
Portions Copyright (c)2005 Olaf Kolkman (RIPE NCC)
Portions Copyright (c)2006 Olaf Kolkman (NLnet Labs)
Portions Copyright (c)2014 Dick Franks
All rights reserved.
=head1 LICENSE
Permission to use, copy, modify, and distribute this software and its
documentation for any purpose and without fee is hereby granted, provided
that the above copyright notice appear in all copies and that both that
copyright notice and this permission notice appear in supporting
documentation, and that the name of the author not be used in advertising
or publicity pertaining to distribution of the software without specific
prior written permission.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
DEALINGS IN THE SOFTWARE.
=head1 AUTHOR INFORMATION
Net::DNS is maintained at NLnet Labs (www.nlnetlabs.nl) by Willem Toorop.
Between 2005 and 2012 Net::DNS was maintained by Olaf Kolkman.
Between 2002 and 2004 Net::DNS was maintained by Chris Reinhardt.
Net::DNS was created in 1997 by Michael Fuhr.
=head1 SEE ALSO
L<perl>, L<Net::DNS::Resolver>, L<Net::DNS::Question>, L<Net::DNS::RR>,
L<Net::DNS::Packet>, L<Net::DNS::Update>,
RFC1035, L<http://www.net-dns.org/>,
I<DNS and BIND> by Paul Albitz & Cricket Liu
=cut