package Net::DNS::Resolver::Recurse;

#

# $Id: Recurse.pm 1623 2018-01-26 14:23:54Z willem $

#

our $VERSION = (qw$LastChangedRevision: 1623 $)[1];

=head1 NAME

Net::DNS::Resolver::Recurse - DNS recursive resolver

=head1 SYNOPSIS

    use Net::DNS::Resolver::Recurse;

    $resolver = new Net::DNS::Resolver::Recurse();

    $packet = $resolver->query ( 'www.example.com', 'A' );

    $packet = $resolver->search( 'www.example.com', 'A' );

    $packet = $resolver->send  ( 'www.example.com', 'A' );

=head1 DESCRIPTION

This module is a subclass of Net::DNS::Resolver.

=cut

use strict;

use warnings;

use base qw(Net::DNS::Resolver);

=head1 METHODS

This module inherits almost all the methods from Net::DNS::Resolver.

Additional module-specific methods are described below.

=head2 hints

This method specifies a list of the IP addresses of nameservers to

be used to discover the addresses of the root nameservers.

    $resolver->hints(@ip);

If no hints are passed, the priming query is directed to nameservers

drawn from a built-in list of IP addresses.

=cut

my @hints;

my $root = [];

sub hints {

	my $self = shift;

	splice @hints, 0, 0, splice( @hints, int( rand scalar @hints ) );    # cut deck

	return @hints unless scalar @_;

	$root  = [];

	@hints = @_;

}

=head2 query, search, send

The query(), search() and send() methods produce the same result

as their counterparts in Net::DNS::Resolver.

    $packet = $resolver->send( 'www.example.com.', 'A' );

Server-side recursion is suppressed by clearing the recurse flag in

query packets and recursive name resolution is performed explicitly.

The query() and search() methods are inherited from Net::DNS::Resolver

and invoke send() indirectly.

=cut

sub send {

	return &Net::DNS::Resolver::Base::send if ref $_[1];	# send Net::DNS::Packet

	my $self = shift;

	my $res = bless {persistent => {'.' => $root}, %$self}, ref($self);

	my $question = new Net::DNS::Question(@_);

	my $original = pop(@_);					# sneaky extra argument needed

	$original = $question unless ref($original);		# to preserve original request

	my ( $head, @tail ) = $question->{qname}->label;

	my $domain = lc( join( '.', @tail ) || '.' );

	my $nslist = $res->{persistent}->{$domain} ||= [];

	unless ( defined $head ) {

		my $defres = new Net::DNS::Resolver();

		$defres->nameservers( $res->_hints );		# fall back to inbuilt list

		$defres->udppacketsize(1024);			# RFC8109

		my @config = $defres->nameserver( $res->hints );

		return $defres->send(qw(. NS));

	}

	if ( scalar @$nslist ) {

		$self->_diag("using cached nameservers for $domain");

	} else {

		$domain = lc $question->qname if $question->qtype ne 'NULL';

		my $packet = $res->send( $domain, 'NULL', 'IN', $original );

		return unless $packet;

		my @answer = $packet->answer;			# return authoritative answer

		return $packet if $packet->header->aa && grep $_->name eq $original->qname, @answer;

		my @auth = grep $_->type eq 'NS', $packet->answer, $packet->authority;

		my %auth = map { lc $_->nsdname => lc $_->name } @auth;

		my %glue;

		my @glue = grep $_->can('address'), $packet->additional;

		foreach ( grep $auth{lc $_->name}, @glue ) {

			push @{$glue{lc $_->name}}, $_->address;

		}

		my %zone = reverse %auth;

		foreach my $zone ( keys %zone ) {

			my @nsname = grep $auth{$_} eq $zone, keys %auth;

			my @list = map $glue{$_} ? $glue{$_} : $_, @nsname;

			@{$res->{persistent}->{$zone}} = @list;

			return $packet if length($zone) > length($domain);

			$self->_diag("cache nameservers for $zone");

			@$nslist = @list;

		}

	}

	my $query = new Net::DNS::Packet();

	$query->{question} = [$original];

	$res = bless {%$res}, qw(Net::DNS::Resolver) if $nslist eq $root;

	$res->udppacketsize(1024);

	$res->recurse(0);

	splice @$nslist, 0, 0, splice( @$nslist, int( rand scalar @$nslist ) );	   # cut deck

	foreach my $ns (@$nslist) {

		if ( ref $ns ) {

			my @ip = map @$_, grep ref($_), @$nslist;

			$res->nameservers(@ip);			# cached IP list

		} else {

			$self->_diag("find missing glue for $ns");

			my $name = $ns;				# suppress deep recursion by

			$ns = [];				# inserting placeholder in cache

			$ns = [$res->nameservers($name)];	# substitute IP list in situ

		}

		my $reply = $res->send($query);

		next unless $reply;

		$self->_callback($reply);

		return $reply;

	}

}

sub query_dorecursion { &sen;; }				# uncoverable pod

=head2 callback

This method specifies a code reference to a subroutine,

which is then invoked at each stage of the recursive lookup.

For example to emulate dig's C<+trace> function:

    my $coderef = sub {

	my $packet = shift;

	printf ";; Received %d bytes from %s\n\n",

		$packet->answersize, $packet->answerfrom;

    };

    $resolver->callback($coderef);

The callback subroutine is not called

for queries for missing glue records.

=cut

sub callback {

	my $self = shift;

	( $self->{callback} ) = grep ref($_) eq 'CODE', @_;

}

sub _callback {

	my $callback = shift->{callback};

	$callback->(@_) if $callback;

}

sub recursion_callback { &callback; }				# uncoverable pod

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

{

	require Net::DNS::ZoneFile;

	my $dug = new Net::DNS::ZoneFile( \*DATA );

	my @rr	= $dug->read;

	my @auth = grep $_->type eq 'NS', @rr;

	my %auth = map { lc $_->nsdname => 1 } @auth;

	my %glue;

	my @glue = grep $auth{lc $_->name}, @rr;

	foreach ( grep $_->can('address'), @glue ) {

		push @{$glue{lc $_->name}}, $_->address;

	}

	my @ip = map @$_, values %glue;

	sub _hints {			## default hints

		splice @ip, 0, 0, splice( @ip, int( rand scalar @ip ) );    # cut deck

		return @ip;

	}

}

1;

=head1 ACKNOWLEDGEMENT

This package is an improved and compatible reimplementation of the

Net::DNS::Resolver::Recurse.pm created by Rob Brown in 2002,

whose contribution is gratefully acknowledged.

=head1 COPYRIGHT

Copyright (c)2014 Dick Franks.

Portions Copyright (c)2002 Rob Brown.

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 SEE ALSO

L<Net::DNS::Resolver>

=cut

__DATA__	## DEFAULT HINTS

; <<>> DiG 9.9.4-P2-RedHat-9.9.4-18.P2.fc20 <<>> @b.root-servers.net . -t NS

; (2 servers found)

;; global options: +cmd

;; Got answer:

;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 47020

;; flags: qr aa rd; QUERY: 1, ANSWER: 13, AUTHORITY: 0, ADDITIONAL: 27

;; WARNING: recursion requested but not available

;; OPT PSEUDOSECTION:

; EDNS: version: 0, flags:; udp: 4096

;; QUESTION SECTION:

;.				IN	NS

;; ANSWER SECTION:

.			518400	IN	NS	c.root-servers.net.

.			518400	IN	NS	k.root-servers.net.

.			518400	IN	NS	l.root-servers.net.

.			518400	IN	NS	j.root-servers.net.

.			518400	IN	NS	b.root-servers.net.

.			518400	IN	NS	g.root-servers.net.

.			518400	IN	NS	h.root-servers.net.

.			518400	IN	NS	d.root-servers.net.

.			518400	IN	NS	a.root-servers.net.

.			518400	IN	NS	f.root-servers.net.

.			518400	IN	NS	i.root-servers.net.

.			518400	IN	NS	m.root-servers.net.

.			518400	IN	NS	e.root-servers.net.

;; ADDITIONAL SECTION:

a.root-servers.net.	3600000	IN	A	198.41.0.4

b.root-servers.net.	3600000	IN	A	192.228.79.201

c.root-servers.net.	3600000	IN	A	192.33.4.12

d.root-servers.net.	3600000	IN	A	199.7.91.13

e.root-servers.net.	3600000	IN	A	192.203.230.10

f.root-servers.net.	3600000	IN	A	192.5.5.241

g.root-servers.net.	3600000	IN	A	192.112.36.4

h.root-servers.net.	3600000	IN	A	198.97.190.53

i.root-servers.net.	3600000	IN	A	192.36.148.17

j.root-servers.net.	3600000	IN	A	192.58.128.30

k.root-servers.net.	3600000	IN	A	193.0.14.129

l.root-servers.net.	3600000	IN	A	199.7.83.42

m.root-servers.net.	3600000	IN	A	202.12.27.33

a.root-servers.net.	3600000	IN	AAAA	2001:503:ba3e::2:30

b.root-servers.net.	3600000	IN	AAAA	2001:500:84::b

c.root-servers.net.	3600000	IN	AAAA	2001:500:2::c

d.root-servers.net.	3600000	IN	AAAA	2001:500:2d::d

e.root-servers.net.	3600000	IN	AAAA	2001:500:a8::e

f.root-servers.net.	3600000	IN	AAAA	2001:500:2f::f

g.root-servers.net.	3600000	IN	AAAA	2001:500:12::d0d

h.root-servers.net.	3600000	IN	AAAA	2001:500:1::53

i.root-servers.net.	3600000	IN	AAAA	2001:7fe::53

j.root-servers.net.	3600000	IN	AAAA	2001:503:c27::2:30

k.root-servers.net.	3600000	IN	AAAA	2001:7fd::1

l.root-servers.net.	3600000	IN	AAAA	2001:500:9f::42

m.root-servers.net.	3600000	IN	AAAA	2001:dc3::35