package Net::DNS::Resolver::Recurse;
#
# $Id: Recurse.pm 102 2004-08-12 05:16:06Z ctriv $
#
use strict;
use Net::DNS::Resolver;
use vars qw($VERSION @ISA);
$VERSION = (qw$LastChangedRevision: 102 $)[1];
@ISA = qw(Net::DNS::Resolver);
sub hints {
my $self = shift;
my @hints = @_;
print ";; hints(@hints)\n" if $self->{'debug'};
if (!@hints && $self->nameservers) {
$self->hints($self->nameservers);
} else {
$self->nameservers(@hints);
}
print ";; verifying (root) zone...\n" if $self->{'debug'};
# bind always asks one of the hint servers
# for who it thinks is authoritative for
# the (root) zone as a sanity check.
# Nice idea.
my $packet = $self->query(".", "NS", "IN");
my %hints = ();
if ($packet) {
if (my @ans = $packet->answer) {
foreach my $rr (@ans) {
if ($rr->name =~ /^\.?$/ and
$rr->type eq "NS") {
# Found root authority
my $server = lc $rr->rdatastr;
$server =~ s/\.$//;
print ";; FOUND HINT: $server\n" if $self->{'debug'};
$hints{$server} = [];
}
}
foreach my $rr ($packet->additional) {
print ";; ADDITIONAL: ",$rr->string,"\n" if $self->{'debug'};
if (my $server = lc $rr->name and
$rr->type eq "A") {
#print ";; ADDITIONAL HELP: $server -> [".$rr->rdatastr."]\n" if $self->{'debug'};
if ($hints{$server}) {
print ";; STORING IP: $server IN A ",$rr->rdatastr,"\n" if $self->{'debug'};
push @{ $hints{$server} }, $rr->rdatastr;
}
}
}
}
foreach my $server (keys %hints) {
if (!@{ $hints{$server} }) {
# Wipe the servers without lookups
delete $hints{$server};
}
}
$self->{'hints'} = \%hints;
} else {
$self->{'hints'} = {};
}
if (%{ $self->{'hints'} }) {
if ($self->{'debug'}) {
print ";; USING THE FOLLOWING HINT IPS:\n";
foreach my $ips (values %{ $self->{'hints'} }) {
foreach my $server (@{ $ips }) {
print ";; $server\n";
}
}
}
} else {
warn "Server [".($self->nameservers)[0]."] did not give answers";
}
# Disable recursion flag.
$self->recurse(0);
return $self->nameservers( map { @{ $_ } } values %{ $self->{'hints'} } );
}
sub recursion_callback {
my ($self, $sub) = @_;
if ($sub && UNIVERSAL::isa($sub, 'CODE')) {
$self->{'callback'} = $sub;
}
return $self->{'callback'};
}
# $res->query_dorecursion( args );
# Takes same args as Net::DNS::Resolver->query
# Purpose: Do that "hot pototo dance" on args.
sub query_dorecursion {
my $self = shift;
my @query = @_;
# Make sure the hint servers are initialized.
$self->hints unless $self->{'hints'};
# Make sure the authority cache is clean.
# It is only used to store A records of
# authoritative name servers.
$self->{'authority_cache'} = {};
# Obtain real question Net::DNS::Packet
my $query_packet = $self->make_query_packet(@query);
# Seed name servers with hints
return $self->_dorecursion( $query_packet, ".", $self->{'hints'}, 0);
}
sub _dorecursion {
my $self = shift;
my $query_packet = shift;
my $known_zone = shift;
my $known_authorities = shift;
my $depth = shift;
my $cache = $self->{'authority_cache'};
print ";; _dorecursion() depth=[$depth] known_zone=[$known_zone]\n" if $self->{'debug'};
die "Recursion too deep, aborting..." if $depth > 255;
$known_zone =~ s/\.*$/./;
# Get IPs from authorities
my @ns = ();
foreach my $ns (keys %{ $known_authorities }) {
if (scalar @{ $known_authorities->{$ns} }) {
$cache->{$ns} = $known_authorities->{$ns};
push (@ns, @{ $cache->{$ns} });
} elsif ($cache->{$ns}) {
$known_authorities->{$ns} = $cache->{$ns};
push (@ns, @{ $cache->{$ns} });
}
}
if (!@ns) {
my $found_auth = 0;
if ($self->{'debug'}) {
require Data::Dumper;
print ";; _dorecursion() Failed to extract nameserver IPs:\n";
print Data::Dumper::Dumper([$known_authorities,$cache]);
}
foreach my $ns (keys %{ $known_authorities }) {
if (!@{ $known_authorities->{$ns} }) {
print ";; _dorecursion() Manual lookup for authority [$ns]\n" if $self->{'debug'};
my $auth_packet =
$self->_dorecursion
($self->make_query_packet($ns,"A"), # packet
".", # known_zone
$self->{'hints'}, # known_authorities
$depth+1); # depth
if ($auth_packet and my @ans = $auth_packet->answer) {
print ";; _dorecursion() Answers found for [$ns]\n" if $self->{'debug'};
foreach my $rr (@ans) {
if ($rr->type eq "CNAME") {
# Follow CNAME
if (my $server = lc $rr->name) {
$server =~ s/\.*$/./;
if ($server eq $ns) {
my $cname = lc $rr->rdatastr;
$cname =~ s/\.*$/./;
print ";; _dorecursion() Following CNAME ns [$ns] -> [$cname]\n" if $self->{'debug'};
$known_authorities->{$cname} ||= [];
delete $known_authorities->{$ns};
next;
}
}
} elsif ($rr->type eq "A") {
if (my $server = lc $rr->name) {
$server =~ s/\.*$/./;
if ($known_authorities->{$server}) {
my $ip = $rr->rdatastr;
print ";; _dorecursion() Found ns: $server IN A $ip\n" if $self->{'debug'};
$cache->{$server} = $known_authorities->{$server};
push (@{ $cache->{$ns} }, $ip);
$found_auth++;
next;
}
}
}
print ";; _dorecursion() Ignoring useless answer: ",$rr->string,"\n" if $self->{'debug'};
}
} else {
print ";; _dorecursion() Could not find A records for [$ns]\n" if $self->{'debug'};
}
}
}
if ($found_auth) {
print ";; _dorecursion() Found $found_auth new NS authorities...\n" if $self->{'debug'};
return $self->_dorecursion( $query_packet, $known_zone, $known_authorities, $depth+1);
}
print ";; _dorecursion() No authority information could be obtained.\n" if $self->{'debug'};
return undef;
}
# Cut the deck of IPs in a random place.
print ";; _dorecursion() cutting deck of (".scalar(@ns).") authorities...\n" if $self->{'debug'};
splice(@ns, 0, 0, splice(@ns, int(rand @ns)));
print ";; _dorecursion() First nameserver [$ns[0]]\n" if $self->{'debug'};
$self->nameservers(@ns);
if (my $packet = $self->send( $query_packet )) {
if ($self->{'callback'}) {
$self->{'callback'}->($packet);
}
my $of = undef;
print ";; _dorecursion() Response received from [",$self->answerfrom,"]\n" if $self->{'debug'};
if (my $status = $packet->header->rcode) {
if ($status eq "NXDOMAIN") {
# I guess NXDOMAIN is the best we'll ever get
print ";; _dorecursion() returning NXDOMAIN\n" if $self->{'debug'};
return $packet;
} elsif (my @ans = $packet->answer) {
print ";; _dorecursion() Answers were found.\n" if $self->{'debug'};
return $packet;
} elsif (my @authority = $packet->authority) {
my %auth = ();
foreach my $rr (@authority) {
if ($rr->type =~ /^(NS|SOA)$/) {
my $server = lc ($1 eq "NS" ? $rr->nsdname : $rr->mname);
$server =~ s/\.*$/./;
$of = lc $rr->name;
$of =~ s/\.*$/./;
print ";; _dorecursion() Received authority [$of] [",$rr->type(),"] [$server]\n" if $self->{'debug'};
if (length $of <= length $known_zone) {
print ";; _dorecursion() Deadbeat name server did not provide new information.\n" if $self->{'debug'};
} elsif ($of =~ /$known_zone$/) {
print ";; _dorecursion() FOUND closer authority for [$of] at [$server].\n" if $self->{'debug'};
$auth{$server} ||= [];
} else {
print ";; _dorecursion() Confused name server [",$self->answerfrom,"] thinks [$of] is closer than [$known_zone]?\n" if $self->{'debug'};
last;
}
} else {
print ";; _dorecursion() Ignoring NON NS entry found in authority section: ",$rr->string,"\n" if $self->{'debug'};
}
}
foreach my $rr ($packet->additional) {
if ($rr->type eq "CNAME") {
# Store this CNAME into %auth too
if (my $server = lc $rr->name) {
$server =~ s/\.*$/./;
if ($auth{$server}) {
my $cname = lc $rr->rdatastr;
$cname =~ s/\.*$/./;
print ";; _dorecursion() FOUND CNAME authority: ",$rr->string,"\n" if $self->{'debug'};
$auth{$cname} ||= [];
$auth{$server} = $auth{$cname};
next;
}
}
} elsif ($rr->type eq "A") {
if (my $server = lc $rr->name) {
$server =~ s/\.*$/./;
if ($auth{$server}) {
print ";; _dorecursion() STORING: $server IN A ",$rr->rdatastr,"\n" if $self->{'debug'};
push @{ $auth{$server} }, $rr->rdatastr;
next;
}
}
}
print ";; _dorecursion() Ignoring useless: ",$rr->string,"\n" if $self->{'debug'};
}
if ($of =~ /$known_zone$/) {
return $self->_dorecursion( $query_packet, $of, \%auth, $depth+1 );
} else {
return $self->_dorecursion( $query_packet, $known_zone, $known_authorities, $depth+1 );
}
}
}
}
return undef;
}
1;
__END__
=head1 NAME
Net::DNS::Resolver::Recurse - Perform recursive dns lookups
=head1 SYNOPSIS
use Net::DNS::Resolver::Recurse;
my $res = Net::DNS::Resolver::Recurse->new;
=head1 DESCRIPTION
This module is a sub class of Net::DNS::Resolver. So the methods for
Net::DNS::Resolver still work for this module as well. There are just a
couple methods added:
=head2 hints
Initialize the hint servers. Recursive queries need a starting name
server to work off of. This method takes a list of IP addresses to use
as the starting servers. These name servers should be authoritative for
the root (.) zone.
$res->hints(@ips);
If no hints are passed, the default nameserver is asked for the hints.
Normally these IPs can be obtained from the following location:
ftp://ftp.internic.net/domain/named.root
=head2 recursion_callback
This method is takes a code reference, which is then invoked each time a
packet is received during the recursive lookup. For example to emulate
dig's C<+trace> function:
$res->recursion_callback(sub {
my $packet = shift;
$_->print for $packet->additional;
printf(";; Received %d bytes from %s\n\n",
$packet->answersize,
$packet->answerfrom
);
});
=head2 query_dorecursion
This method is much like the normal query() method except it disables
the recurse flag in the packet and explicitly performs the recursion.
$packet = $res->query_dorecursion( "www.netscape.com.", "A");
=head1 AUTHOR
Rob Brown, bbb@cpan.org
=head1 SEE ALSO
L<Net::DNS::Resolver>,
=head1 COPYRIGHT
Copyright (c) 2002, Rob Brown. All rights reserved.
This module is free software; you can redistribute
it and/or modify it under the same terms as Perl itself.
$Id: Recurse.pm 102 2004-08-12 05:16:06Z ctriv $
=cut
Example lookup process:
[root@box root]# dig +trace www.rob.com.au.
; <<>> DiG 9.2.0 <<>> +trace www.rob.com.au.
;; global options: printcmd
. 507343 IN NS C.ROOT-SERVERS.NET.
. 507343 IN NS D.ROOT-SERVERS.NET.
. 507343 IN NS E.ROOT-SERVERS.NET.
. 507343 IN NS F.ROOT-SERVERS.NET.
. 507343 IN NS G.ROOT-SERVERS.NET.
. 507343 IN NS H.ROOT-SERVERS.NET.
. 507343 IN NS I.ROOT-SERVERS.NET.
. 507343 IN NS J.ROOT-SERVERS.NET.
. 507343 IN NS K.ROOT-SERVERS.NET.
. 507343 IN NS L.ROOT-SERVERS.NET.
. 507343 IN NS M.ROOT-SERVERS.NET.
. 507343 IN NS A.ROOT-SERVERS.NET.
. 507343 IN NS B.ROOT-SERVERS.NET.
;; Received 436 bytes from 127.0.0.1#53(127.0.0.1) in 9 ms
;;; But these should be hard coded as the hints
;;; Ask H.ROOT-SERVERS.NET gave:
au. 172800 IN NS NS2.BERKELEY.EDU.
au. 172800 IN NS NS1.BERKELEY.EDU.
au. 172800 IN NS NS.UU.NET.
au. 172800 IN NS BOX2.AUNIC.NET.
au. 172800 IN NS SEC1.APNIC.NET.
au. 172800 IN NS SEC3.APNIC.NET.
;; Received 300 bytes from 128.63.2.53#53(H.ROOT-SERVERS.NET) in 322 ms
;;; A little closer than before
;;; Ask NS2.BERKELEY.EDU gave:
com.au. 259200 IN NS ns4.ausregistry.net.
com.au. 259200 IN NS dns1.telstra.net.
com.au. 259200 IN NS au2ld.CSIRO.au.
com.au. 259200 IN NS audns01.syd.optus.net.
com.au. 259200 IN NS ns.ripe.net.
com.au. 259200 IN NS ns1.ausregistry.net.
com.au. 259200 IN NS ns2.ausregistry.net.
com.au. 259200 IN NS ns3.ausregistry.net.
com.au. 259200 IN NS ns3.melbourneit.com.
;; Received 387 bytes from 128.32.206.12#53(NS2.BERKELEY.EDU) in 10312 ms
;;; A little closer than before
;;; Ask ns4.ausregistry.net gave:
com.au. 259200 IN NS ns1.ausregistry.net.
com.au. 259200 IN NS ns2.ausregistry.net.
com.au. 259200 IN NS ns3.ausregistry.net.
com.au. 259200 IN NS ns4.ausregistry.net.
com.au. 259200 IN NS ns3.melbourneit.com.
com.au. 259200 IN NS dns1.telstra.net.
com.au. 259200 IN NS au2ld.CSIRO.au.
com.au. 259200 IN NS ns.ripe.net.
com.au. 259200 IN NS audns01.syd.optus.net.
;; Received 259 bytes from 137.39.1.3#53(ns4.ausregistry.net) in 606 ms
;;; Uh... yeah... I already knew this
;;; from what NS2.BERKELEY.EDU told me.
;;; ns4.ausregistry.net must have brain damage
;;; Ask ns1.ausregistry.net gave:
rob.com.au. 86400 IN NS sy-dns02.tmns.net.au.
rob.com.au. 86400 IN NS sy-dns01.tmns.net.au.
;; Received 87 bytes from 203.18.56.41#53(ns1.ausregistry.net) in 372 ms
;;; Ah, much better. Something more useful.
;;; Ask sy-dns02.tmns.net.au gave:
www.rob.com.au. 7200 IN A 139.134.5.123
rob.com.au. 7200 IN NS sy-dns01.tmns.net.au.
rob.com.au. 7200 IN NS sy-dns02.tmns.net.au.
;; Received 135 bytes from 139.134.2.18#53(sy-dns02.tmns.net.au) in 525 ms
;;; FINALLY, THE ANSWER!