Question.pm   [plain text]

package Net::DNS::Question;
#
# $Id: Question.pm 704 2008-02-06 21:30:59Z olaf $
#
use strict;
BEGIN { 
    eval { require bytes; }
} 

use vars qw($VERSION $AUTOLOAD);

use Carp;
use Net::DNS;

$VERSION = (qw$LastChangedRevision: 704 $)[1];

=head1 NAME

Net::DNS::Question - DNS question class

=head1 SYNOPSIS

C<use Net::DNS::Question>

=head1 DESCRIPTION

A C<Net::DNS::Question> object represents a record in the
question section of a DNS packet.

=head1 METHODS

=head2 new

    $question = Net::DNS::Question->new("example.com", "MX", "IN");

Creates a question object from the domain, type, and class passed
as arguments.

RFC4291 and RFC4632 IP address/prefix notation is supported for
queries in in-addr.arpa and ip6.arpa subdomains.

=cut

sub new {
	my $class = shift;

	my $qname = shift;
	my $qtype = uc (shift || 'A');
	my $qclass = uc (shift || 'IN');

	$qname = '' unless defined $qname;	# || ''; is NOT same!
	$qname =~ s/\.+$//o;			# strip gratuitous trailing dot

	# Check if the caller has the type and class reversed.
	# We are not that kind for unknown types.... :-)
	($qtype, $qclass) = ($qclass, $qtype)
		if exists $Net::DNS::classesbyname{$qtype}
		and exists $Net::DNS::typesbyname{$qclass};

	# if argument is an IP address, do appropriate reverse lookup
	my $reverse = _dns_addr($qname) if $qname =~ m/:|\d$/o;
	if ( $reverse ) {
		$qname = $reverse;
		$qtype = 'PTR' if $qtype =~ m/^(A|AAAA)$/o;
	}

	my $self = {	qname	=> $qname,
			qtype	=> $qtype,
			qclass	=> $qclass
			};

	bless $self, $class;
}


sub _dns_addr {
	my $arg = shift;	# name or IP address

	# IP address must contain address characters only
	return undef if $arg =~ m#[^a-fA-F0-9:./]#o;

	# if arg looks like IPv4 address then map to in-addr.arpa space
	if ( $arg =~ m#(^|:.*:)((^|\d+\.)+\d+)(/(\d+))?$#o ) {
		my @parse = split /\./, $2;
		my $prefx = $5 || @parse<<3;
		my $last = $prefx > 24 ? 3 : ($prefx-1)>>3;
		return join '.', reverse( (@parse,(0)x3)[0 .. $last] ), 'in-addr.arpa';
	}

	# if arg looks like IPv6 address then map to ip6.arpa space
	if ( $arg =~ m#^((\w*:)+)(\w*)(/(\d+))?$#o ) {
		my @parse = split /:/, (reverse "0${1}0${3}"), 9;
		my @xpand = map{/./ ? $_ : ('0')x(9-@parse)} @parse;	# expand ::
		my $prefx = $5 || @xpand<<4;		# implicit length if unspecified
		my $hex = pack 'A4'x8, map{$_.'000'} ('0')x(8-@xpand), @xpand;
		my $len = $prefx > 124 ? 32 : ($prefx+3)>>2;
		return join '.', split(//, substr($hex,-$len) ), 'ip6.arpa';
	}

	return undef;
}


=head2 parse

    ($question, $offset) = Net::DNS::Question->parse(\$data, $offset);

Parses a question section record at the specified location within a DNS packet.
The first argument is a reference to the packet data.
The second argument is the offset within the packet where the question record begins.

Returns a Net::DNS::Question object and the offset of the next location in the packet.

Parsing is aborted if the question object cannot be created (e.g., corrupt or insufficient data).

=cut

use constant PACKED_LENGTH => length pack 'n2', (0)x2;

sub parse {
	my ($class, $data, $offset) = @_;

	my ($qname, $index) = Net::DNS::Packet::dn_expand($data, $offset);
	die 'Exception: corrupt or incomplete data' unless $index;

	my $next = $index + PACKED_LENGTH;
	die 'Exception: incomplete data' if length $$data < $next;
	my ($qtype, $qclass) = unpack("\@$index n2", $$data);

	my $self = {	qname	=> $qname,
			qtype	=> Net::DNS::typesbyval($qtype),
			qclass	=> Net::DNS::classesbyval($qclass)
			};

	bless $self, $class;

	return wantarray ? ($self, $next) : $self;
}


#
# Some people have reported that Net::DNS dies because AUTOLOAD picks up
# calls to DESTROY.
#
sub DESTROY {}

=head2 qname, zname

    print "qname = ", $question->qname, "\n";
    print "zname = ", $question->zname, "\n";

Returns the domain name.  In dynamic update packets, this field is
known as C<zname> and refers to the zone name.

=head2 qtype, ztype

    print "qtype = ", $question->qtype, "\n";
    print "ztype = ", $question->ztype, "\n";

Returns the record type.  In dymamic update packets, this field is
known as C<ztype> and refers to the zone type (must be SOA).

=head2 qclass, zclass

    print "qclass = ", $question->qclass, "\n";
    print "zclass = ", $question->zclass, "\n";

Returns the record class.  In dynamic update packets, this field is
known as C<zclass> and refers to the zone's class.

=cut

sub zname  { &qname;  }
sub ztype  { &qtype;  }
sub zclass { &qclass; }


sub AUTOLOAD {
	my $self = shift;

	my $name = $AUTOLOAD;
	$name =~ s/.*://o;

	croak "$AUTOLOAD: no such method" unless exists $self->{$name};

	return $self->{$name} unless @_;

	my $value = shift;
	$value =~ s/\.+$//o if defined $value;	# strip gratuitous trailing dot
	$self->{$name} = $value;
}

=head2 print

    $question->print;

Prints the question record on the standard output.

=cut

sub print {	print &string, "\n"; }

=head2 string

    print $qr->string, "\n";

Returns a string representation of the question record.

=cut

sub string {
	my $self = shift;
	return "$self->{qname}.\t$self->{qclass}\t$self->{qtype}";
}

=head2 data

    $qdata = $question->data($packet, $offset);

Returns the question record in binary format suitable for inclusion
in a DNS packet.

Arguments are a C<Net::DNS::Packet> object and the offset within
that packet's data where the C<Net::DNS::Question> record is to
be stored.  This information is necessary for using compressed
domain names.

=cut

sub data {
	my ($self, $packet, $offset) = @_;

	my $data = $packet->dn_comp($self->{qname}, $offset);

	$data .= pack('n2',	Net::DNS::typesbyname(uc $self->{qtype}),
				Net::DNS::classesbyname(uc $self->{qclass})
				);
	return $data;
}

=head1 COPYRIGHT

Copyright (c) 1997-2002 Michael Fuhr. 

Portions Copyright (c) 2002-2004 Chris Reinhardt.

Portions Copyright (c) 2003,2006-2007 Dick Franks.

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

=head1 SEE ALSO

L<perl(1)>, L<Net::DNS>, L<Net::DNS::Resolver>, L<Net::DNS::Packet>,
L<Net::DNS::Update>, L<Net::DNS::Header>, L<Net::DNS::RR>,
RFC 1035 Section 4.1.2

=cut

1;