File Coverage

blib/lib/Net/DNS/RR.pm

Criterion	Covered	Total	%
statement	294	294	100.0
branch	142	142	100.0
path			n/a
condition	42	42	100.0
subroutine	48	48	100.0
pod	19	21	100.0
total	545	547	100.0

package Net::DNS::RR;

use strict;
use warnings;

our $VERSION = (qw$Id: RR.pm 2037 2025-08-18 14:39:32Z willem $)[2];


=head1 NAME

Net::DNS::RR - DNS resource record base class

=head1 SYNOPSIS

	use Net::DNS;

	$rr = Net::DNS::RR->new('example.com IN AAAA 2001:DB8::1');

	$rr = Net::DNS::RR->new(
			owner	=> 'example.com',
			type	=> 'AAAA',
			address => '2001:DB8::1'
			);


=head1 DESCRIPTION

Net::DNS::RR is the base class for DNS Resource Record (RR) objects.
See also the manual pages for each specific RR type.

=cut


use integer;
use Carp;

use constant LIB => grep { $_ ne '.' } grep { !ref($_) } @INC;

use Net::DNS::Parameters qw(%classbyname :class :type);
use Net::DNS::DomainName;


=head1 METHODS

B  Do not assume the RR objects you receive from a query
are of a particular type.  You must always check the object type
before calling any of its methods.  If you call an unknown method,
you will get an error message and execution will be terminated.

=cut

sub new {
	my ( $class, @list ) = @_;
	my $rr = eval {
		local $SIG{__DIE__};
		scalar @list > 1 ? &_new_hash : &_new_string;
	};
	return $rr if $rr;
	my @param = map { defined($_) ? split /\s+/ : 'undef' } @list;
	my $stmnt = substr "$class->new( @param )", 0, 80;
	croak "${@}in $stmnt\n";
}


=head2 new (from string)

	$aaaa	= Net::DNS::RR->new('host.example.com. 86400 AAAA 2001:DB8::1');
	$mx	= Net::DNS::RR->new('example.com. 7200 MX 10 mailhost.example.com.');
	$cname	= Net::DNS::RR->new('www.example.com 300 IN CNAME host.example.com');
	$txt	= Net::DNS::RR->new('txt.example.com 3600 HS TXT "text data"');

Returns an object of the appropriate RR type, or a L object
if the type is not implemented. The attribute values are extracted from the
string passed by the user. The syntax of the argument string follows the
RFC1035 specification for zone files, and is compatible with the result
returned by the string method.

The owner and RR type are required; all other information is optional.
Omitting the optional fields is useful for creating the empty RDATA
sections required for certain dynamic update operations.
See the L manual page for additional examples.

All names are interpreted as fully qualified domain names.
The trailing dot (.) is optional.

=cut

my $PARSE_REGEX = q/("[^"]*")|;[^\n]*|[ \t\n\r\f()]+/;		# NB: *not* \s (matches Unicode white space)

sub _new_string {
	my ( $base, $string ) = @_;
	die 'argument absent or undefined' unless defined $string;
	die 'non-scalar argument' if ref $string;

	# parse into quoted strings, contiguous non-whitespace and (discarded) comments
	local $_ = $string;
	s/\\\\/\\092/g;						# disguise escaped escape
	s/\\"/\\034/g;						# disguise escaped quote
	s/\\\(/\\040/g;						# disguise escaped bracket
	s/\\\)/\\041/g;						# disguise escaped bracket
	s/\\;/\\059/g;						# disguise escaped semicolon
	my ( $owner, @token ) = grep { defined && length } split /$PARSE_REGEX/o;

	die 'unable to parse RR string' unless scalar @token;
	my $t1 = $token[0];
	my $t2 = $token[1];

	my ( $ttl, $class );
	if ( not defined $t2 ) {				#
		@token = ('ANY') if $classbyname{uc $t1};	#
	} elsif ( $t1 =~ /^\d/ ) {
		$ttl   = shift @token;				#   []
		$class = shift @token if $classbyname{uc $t2} || $t2 =~ /^CLASS\d/i;
	} elsif ( $classbyname{uc $t1} || $t1 =~ /^CLASS\d/i ) {
		$class = shift @token;				#   []
		$ttl   = shift @token if $t2 =~ /^\d/;
	}

	my $type      = shift(@token);
	my $populated = scalar @token;

	my $self = $base->_subclass( $type, $populated );	# create RR object
	$self->owner($owner);
	&class( $self, $class );				# specify CLASS
	&ttl( $self, $ttl );					# specify TTL

	return $self unless $populated;				# empty RR

	if ( $#token && $token[0] =~ /^[\\]?#$/ ) {
		shift @token;					# RFC3597 hexadecimal format
		my $rdlen = shift(@token) || 0;
		my $rdata = pack 'H*', join( '', @token );
		die 'length and hexadecimal data inconsistent' unless $rdlen == length $rdata;
		$self->rdata($rdata);				# unpack RDATA
	} else {
		$self->_parse_rdata(@token);			# parse arguments
	}

	$self->_post_parse();
	return $self;
}


=head2 new (from hash)

	$rr = Net::DNS::RR->new(%hash);

	$rr = Net::DNS::RR->new(
			owner	=> 'host.example.com',
			ttl	=> 86400,
			class	=> 'IN',
			type	=> 'AAAA',
			address => '2001:DB8::1'
			);

	$rr = Net::DNS::RR->new(
			owner	=> 'txt.example.com',
			type	=> 'TXT',
			txtdata => [ 'one', 'two' ]
			);

Returns an object of the appropriate RR type, or a L object
if the type is not implemented. Consult the relevant manual pages for the
usage of type specific attributes.

The owner and RR type are required; all other information is optional.
Omitting optional attributes is useful for creating the empty RDATA
sections required for certain dynamic update operations.

=cut

my @core = qw(owner name type class ttl rdlength);

sub _new_hash {
	my $base = shift;

	my %argument = ( owner => '.', type => 'NULL' );
	my @attribute;
	while ( my $key = shift ) {
		push @attribute, $key;
		$argument{lc $key} = shift;
	}

	my ( $owner, $name, $type, $class, $ttl ) = delete @argument{@core};

	my $self = $base->_subclass( $type, scalar(%argument) );
	$self->owner( $name ? $name : $owner );
	$self->class($class) if defined $class;			# optional CLASS
	$self->ttl($ttl)     if defined $ttl;			# optional TTL

	eval {
		foreach my $attribute (@attribute) {
			my $value = $argument{lc $attribute};
			next unless defined $value;
			$self->$attribute( ref($value) eq 'ARRAY' ? @$value : $value );
		}
	};
	die ref($self) eq __PACKAGE__ ? "type $type not implemented" : () if $@;

	$self->_post_parse();
	return $self;
}


=head2 decode

	( $rr, $next ) = Net::DNS::RR->decode( \$data, $offset, @opaque );

Decodes a DNS resource record at the specified location within a
DNS packet.

The argument list consists of a reference to the buffer containing
the packet data and offset indicating where resource record begins.
Any remaining arguments are passed as opaque data to subordinate
decoders and do not form part of the published interface.

Returns a C object and the offset of the next record
in the packet.

An exception is raised if the data buffer contains insufficient or
corrupt data.

=cut

use constant RRFIXEDSZ => length pack 'n2 N n', (0) x 4;

sub decode {
	my ( $base, @argument ) = @_;

	my ( $owner, $fixed ) = Net::DNS::DomainName1035->decode(@argument);
	my $index = $fixed + RRFIXEDSZ;
	my ( $data, $offset, @opaque ) = @argument;
	die 'corrupt wire-format data' if length $$data < $index;
	my $self = $base->_subclass( unpack "\@$fixed n", $$data );
	$self->{owner} = $owner;
	@{$self}{qw(class ttl rdlength)} = unpack "\@$fixed x2 n N n", $$data;

	my $next = $index + $self->{rdlength};
	die 'corrupt wire-format data' if length $$data < $next;

	if ( $next > $index or $self->type eq 'OPT' ) {
		local $self->{offset} = $offset;
		eval { $self->_decode_rdata( $data, $index, @opaque ) };
		warn $@ if $@;
	}

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


=head2 encode

	$data = $rr->encode( $offset, @opaque );

Returns the C in binary format suitable for inclusion
in a DNS packet buffer.

The offset indicates the intended location within the packet data
where the C is to be stored.

Any remaining arguments are opaque data which are passed intact to
subordinate encoders.

=cut

sub encode {
	my ( $self, $offset, @opaque ) = @_;
	( $offset, @opaque ) = ( 0x4000, {} ) unless defined $offset;

	my $owner = $self->{owner}->encode( $offset, @opaque );
	my ( $type, $class, $ttl ) = @{$self}{qw(type class ttl)};
	my $rdata = $self->_empty ? '' : $self->_encode_rdata( $offset + length($owner) + RRFIXEDSZ, @opaque );
	return pack 'a* n2 N n a*', $owner, $type, $class || 1, $ttl || 0, length $rdata, $rdata;
}


=head2 canonical

	$data = $rr->canonical;

Returns the C in canonical binary format suitable for
DNSSEC signature validation.

The absence of the associative array argument signals to subordinate
encoders that the canonical uncompressed form of embedded domain
names is to be used.

=cut

sub canonical {
	my $self = shift;

	my $owner = $self->{owner}->canonical;
	my ( $type, $class, $ttl ) = @{$self}{qw(type class ttl)};
	my $rdata = $self->_empty ? '' : $self->_encode_rdata( length($owner) + RRFIXEDSZ );
	return pack 'a* n2 N n a*', $owner, $type, $class || 1, $ttl || 0, length $rdata, $rdata;
}


=head2 print

	$rr->print;

Prints the resource record to the currently selected output filehandle.
Calls the string method to get the formatted RR representation.

=cut

sub print {
	print shift->string, "\n";
	return;
}


=head2 string

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

Returns a string representation of the RR using the master file format
mandated by RFC1035.
All domain names are fully qualified with trailing dot.
This differs from RR attribute methods, which omit the trailing dot.

=cut

sub string {
	my $self = shift;

	my $owner = $self->{owner}->string;
	my @ttl	  = defined $self->{ttl}   ? $self->{ttl} : ();
	my @class = defined $self->{class} ? $self->class : ();
	my @core  = ( $owner, @ttl, @class, $self->type );

	local $SIG{__DIE__};
	my $empty = $self->_empty;
	my @rdata = $empty ? () : eval { $self->_format_rdata };
	carp $@ if $@;

	my $tab	 = length($owner) < 72 ? "\t" : ' ';
	my @line = _wrap( join( $tab, @core, '(' ), @rdata, ')' );

	my $last = pop(@line);					# last or only line
	$last = join $tab, @core, "@rdata" unless scalar(@line);

	$self->_annotation('no data') if $empty;
	return join "\n\t", @line, _wrap( $last, $self->_annotation );
}


=head2 plain

	$plain = $rr->plain;

Returns a simplified single-line representation of the RR.
This facilitates interaction with programs like nsupdate
which have rudimentary parsers.

=cut

sub plain {
	return join ' ', shift->token;
}


=head2 token

	@token = $rr->token;

Returns a token list representation of the RR zone file string.

=cut

sub token {
	my $self = shift;

	my @ttl	  = defined $self->{ttl}   ? $self->{ttl} : ();
	my @class = defined $self->{class} ? $self->class : ();
	my @core  = ( $self->{owner}->string, @ttl, @class, $self->type );

	# parse into quoted strings, contiguous non-whitespace and (discarded) comments
	local $_ = $self->_empty ? '' : join( ' ', $self->_format_rdata );
	s/\\\\/\\092/g;						# disguise escaped escape
	s/\\"/\\034/g;						# disguise escaped quote
	s/\\\(/\\040/g;						# disguise escaped bracket
	s/\\\)/\\041/g;						# disguise escaped bracket
	s/\\;/\\059/g;						# disguise escaped semicolon
	return ( @core, grep { defined && length } split /$PARSE_REGEX/o );
}


=head2 generic

	$generic = $rr->generic;

Returns the generic RR representation defined in RFC3597. This facilitates
creation of zone files containing RRs unrecognised by outdated nameservers
and provisioning software.

=cut

sub generic {
	my $self = shift;

	my @ttl	  = defined $self->{ttl}   ? $self->{ttl}	   : ();
	my @class = defined $self->{class} ? "CLASS$self->{class}" : ();
	my @core  = ( $self->{owner}->string, @ttl, @class, "TYPE$self->{type}" );
	my $data  = $self->rdata;
	my @data  = ( '\\#', length($data), split /(\S{32})/, unpack 'H*', $data );
	my @line  = _wrap( "@core (", @data, ')' );
	return join "\n\t", @line if scalar(@line) > 1;
	return join ' ', @core, @data;
}


=head2 owner name

	$name = $rr->owner;

Returns the owner name of the record.

=cut

sub owner {
	my ( $self, @name ) = @_;
	for (@name) { $self->{owner} = Net::DNS::DomainName1035->new($_) }
	return defined wantarray ? $self->{owner}->name : undef;
}

sub name { return &owner; }		## historical


=head2 type

	$type = $rr->type;

Returns the record type.

=cut

sub type {
	my ( $self, @value ) = @_;
	for (@value) { croak 'not possible to change RR->type' }
	return typebyval( $self->{type} );
}


=head2 class

	$class = $rr->class;

Resource record class.

=cut

sub class {
	my ( $self, $class ) = @_;
	return $self->{class} = classbyname($class) if defined $class;
	return defined $self->{class} ? classbyval( $self->{class} ) : 'IN';
}


=head2 ttl

	$ttl = $rr->ttl;
	$ttl = $rr->ttl(3600);

Resource record time to live in seconds.

=cut

# The following time units are recognised, but are not part of the
# published API.  These are required for parsing BIND zone files but
# should not be used in other contexts.
my %unit = ( W => 604800, D => 86400, H => 3600, M => 60, S => 1 );

sub ttl {
	my ( $self, $time ) = @_;

	return $self->{ttl} || 0 unless defined $time;		# avoid defining rr->{ttl}

	my $ttl	 = 0;
	my %time = reverse split /(\D)\D*/, $time . 'S';
	while ( my ( $u, $t ) = each %time ) {
		my $scale = $unit{uc $u} || die qq(bad time: $t$u);
		$ttl += $t * $scale;
	}
	return $self->{ttl} = $ttl;
}


################################################################################
##
##	Default implementation for unknown RR type
##
################################################################################

sub _decode_rdata {			## decode rdata from wire-format octet string
	my ( $self, $data, $offset ) = @_;
	return $self->{rdata} = substr $$data, $offset, $self->{rdlength};
}


sub _encode_rdata {			## encode rdata as wire-format octet string
	return shift->{rdata};
}


sub _format_rdata {			## format rdata portion of RR string
	my $rdata = shift->rdata;				# RFC3597 unknown RR format
	return ( '\\#', length($rdata), split /(\S{32})/, unpack 'H*', $rdata );
}


sub _parse_rdata {			## parse RR attributes in argument list
	my $self = shift;
	die join ' ', 'type', $self->type, 'not implemented' if ref($self) eq __PACKAGE__;
	die join ' ', 'no zone file representation defined for', $self->type;
}


sub _post_parse { }			## parser post processing


sub _defaults { }			## set attribute default values


sub dump {				## print internal data structure
	my @data = @_;						# uncoverable pod
	require Data::Dumper;
	local $Data::Dumper::Maxdepth = $Data::Dumper::Maxdepth || 6;
	local $Data::Dumper::Sortkeys = $Data::Dumper::Sortkeys || 1;
	local $Data::Dumper::Useqq    = $Data::Dumper::Useqq	|| 1;
	return print Data::Dumper::Dumper(@data);
}

sub rdatastr {				## historical RR subtype method
	my $self = shift;					# uncoverable pod
	$self->_deprecate('prefer $rr->rdstring()');
	return $self->rdstring;
}


=head2 rdata

	$rr = Net::DNS::RR->new( type => NULL, rdata => 'arbitrary' );

Resource record data section when viewed as opaque octets.

=cut

sub rdata {
	my $self = shift;

	return $self->_empty ? '' : eval { $self->_encode_rdata( 0x4000, {} ) } unless @_;

	my $data = shift || '';
	$self->_decode_rdata( \$data, 0 ) if ( $self->{rdlength} = length $data );
	return;
}


=head2 rdstring

	$rdstring = $rr->rdstring;

Returns a string representation of the RR-specific data.

=cut

sub rdstring {
	my $self = shift;
	local $SIG{__DIE__};

	my @rdata = $self->_empty ? () : eval { $self->_format_rdata };
	carp $@ if $@;

	return join "\n\t", _wrap(@rdata);
}


=head2 rdlength

	$rdlength = $rr->rdlength;

Returns the uncompressed length of the encoded RR-specific data.

=cut

sub rdlength {
	return length shift->rdata;
}


###################################################################################

=head1 Sorting of RR arrays

Sorting of RR arrays is done by Net::DNS::rrsort(), see documentation
for L. This package provides class methods to set the
comparator function used for a particular RR based on its attributes.


=head2 set_rrsort_func

	my $function = sub {	## numerically ascending order
		$Net::DNS::a->{'preference'} <=> $Net::DNS::b->{'preference'};
		};

	Net::DNS::RR::MX->set_rrsort_func( 'preference', $function );

	Net::DNS::RR::MX->set_rrsort_func( 'default_sort', $function );

set_rrsort_func() must be called as a class method. The first argument is
the attribute name on which the sorting is to take place. If you specify
"default_sort" then that is the sort algorithm that will be used when
get_rrsort_func() is called without an RR attribute as argument.

The second argument is a reference to a comparator function that uses the
global variables $a and $b in the Net::DNS package. During sorting, the
variables $a and $b will contain references to objects of the class whose
set_rrsort_func() was called. The above sorting function will only be
applied to Net::DNS::RR::MX objects.

The above example is the sorting function implemented in MX.

=cut

our %rrsortfunct;

sub set_rrsort_func {
	my $class     = shift;
	my $attribute = shift;
	my $function  = shift;

	my ($type) = $class =~ m/::([^:]+)$/;
	$rrsortfunct{$type}{$attribute} = $function;
	return;
}


=head2 get_rrsort_func

	$function = Net::DNS::RR::MX->get_rrsort_func('preference');
	$function = Net::DNS::RR::MX->get_rrsort_func();

get_rrsort_func() returns a reference to the comparator function.

=cut

my $default = sub { return $Net::DNS::a->canonical() cmp $Net::DNS::b->canonical(); };

sub get_rrsort_func {
	my $class     = shift;
	my $attribute = shift || 'default_sort';

	my ($type) = $class =~ m/::([^:]+)$/;

	return $rrsortfunct{$type}{$attribute} || return $default;
}


################################################################################
#
#  Net::DNS::RR->_subclass($rrname)
#  Net::DNS::RR->_subclass($rrname, $default)
#
# Create a new object blessed into appropriate RR subclass, after
# loading the subclass module (if necessary).  A subclass with no
# corresponding module will be regarded as unknown and blessed
# into the RR base class.
#
# The optional second argument indicates that default values are
# to be copied into the newly created object.

our %_MINIMAL = ( 255 => bless ['type' => 255], __PACKAGE__ );
our %_LOADED  = %_MINIMAL;

sub _subclass {
	my ( $class, $rrname, $default ) = @_;

	unless ( $_LOADED{$rrname} ) {
		my $rrtype = typebyname($rrname);

		unless ( $_LOADED{$rrtype} ) {			# load once only
			local @INC = LIB;

			my $identifier = typebyval($rrtype);
			$identifier =~ s/\W/_/g;		# kosher Perl identifier

			my $subclass = join '::', __PACKAGE__, $identifier;

			unless ( eval "require $subclass" ) {	## no critic ProhibitStringyEval
				my $perl = Net::DNS::Parameters::_typespec("$rrtype.RRTYPE");
				$subclass = join '::', __PACKAGE__, "TYPE$rrtype";
				push @INC, sub {		# see perldoc -f require
					my @line = split /\n/, $perl;
					return ( sub { defined( $_ = shift @line ) } );
				};
				eval "require $subclass";	## no critic ProhibitStringyEval
			}

			$subclass = __PACKAGE__ if $@;

			# cache pre-built minimal and populated default object images
			my @base = ( 'type' => $rrtype );
			$_MINIMAL{$rrtype} = bless [@base], $subclass;

			my $object = bless {@base}, $subclass;
			$object->_defaults;
			$_LOADED{$rrtype} = bless [%$object], $subclass;
		}

		$_MINIMAL{$rrname} = $_MINIMAL{$rrtype};
		$_LOADED{$rrname}  = $_LOADED{$rrtype};
	}

	my $prebuilt = $default ? $_LOADED{$rrname} : $_MINIMAL{$rrname};
	return bless {@$prebuilt}, ref($prebuilt);		# create object
}


sub _annotation {
	my ( $self, @note ) = @_;
	push @{$self->{annotation}}, "\t; @note" if scalar @note;
	return wantarray ? @{delete( $self->{annotation} ) || []} : undef;
}


my %warned;

sub _deprecate {
	my ( undef, @note ) = @_;
	carp "deprecated method; @note" unless $warned{"@note"}++;
	return;
}


my %ignore = map { ( $_ => 1 ) } @core, 'annotation', '#';

sub _empty {
	my $self = shift;
	return not( $self->{'#'} ||= scalar grep { !$ignore{$_} } keys %$self );
}


sub _wrap {
	my @text = @_;
	my $cols = 80;
	my $coln = 0;

	my ( @line, @fill );
	foreach (@text) {
		$coln += ( length || next ) + 1;
		if ( $coln > $cols ) {				# start new line
			push( @line, join ' ', @fill ) if @fill;
			$coln = length;
			@fill = ();
		}
		$coln = $cols	  if chomp;			# force line break
		push( @fill, $_ ) if length;
	}
	return ( @line, join ' ', @fill );
}


################################################################################

sub DESTROY { }				## Avoid tickling AUTOLOAD (in cleanup)

## no critic
sub AUTOLOAD {				## Default method
	my ($self) = @_;

	no strict 'refs';		## no critic ProhibitNoStrict
	our $AUTOLOAD;
	my ($method) = reverse split /::/, $AUTOLOAD;

	my $canonical = lc($method);	## tolerate mixed-case attribute name
	if ( $self->can($canonical) ) {
		*{$AUTOLOAD} = sub { shift->$canonical(@_) };
		return &$AUTOLOAD;
	}

	my $oref = ref($self);
	*{$AUTOLOAD} = sub { };		## suppress deep recursion
	croak qq[$self has no class method "$method"] unless $oref;

	my $string = $self->string;
	my @object = grep { defined($_) } $oref, $oref->VERSION;
	my $module = join '::', __PACKAGE__, $self->type;
	eval("require $module") if $oref eq __PACKAGE__;	## no critic ProhibitStringyEval

	@_ = (<<"END");
***  FATAL PROGRAM ERROR!!	Unknown instance method "$method"
***  which the program has attempted to call for the object:
***
$string
***
***  THIS IS A BUG IN THE CALLING SOFTWARE, which incorrectly assumes
***  that the object would be of a particular type.  The type of an
***  object should be checked before calling any of its methods.
***
@object
$@
END
	goto &Carp::confess;
}


1;
__END__