package App::Netdisco::Util::DNS;
use strict;
use warnings;
use Dancer ':script';
use Net::DNS;
use AnyEvent::DNS;
use NetAddr::IP::Lite ':lower';
use base 'Exporter';
our @EXPORT = ();
our @EXPORT_OK = qw/
hostname_from_ip hostnames_resolve_async ipv4_from_hostname
/;
our %EXPORT_TAGS = (all => \@EXPORT_OK);
# AE::DNS::EtcHosts only works for A/AAAA/SRV, but we want PTR.
# this loads+parses /etc/hosts file using AE. dirty hack.
use AnyEvent::Socket 'format_address';
use AnyEvent::DNS::EtcHosts;
AnyEvent::DNS::EtcHosts::_load_hosts_unless(sub{},AE::cv);
no AnyEvent::DNS::EtcHosts; # unimport
our %HOSTS = ();
$HOSTS{$_} = [ map { [ $_ ? (format_address $_->[0]) : '' ] }
@{$AnyEvent::DNS::EtcHosts::HOSTS{$_}} ]
for keys %AnyEvent::DNS::EtcHosts::HOSTS;
=head1 NAME
App::Netdisco::Util::DNS
=head1 DESCRIPTION
A set of helper subroutines to support parts of the Netdisco application.
There are no default exports, however the C<:all> tag will export all
subroutines.
=head1 EXPORT_OK
=head2 hostname_from_ip( $ip )
Given an IP address (either IPv4 or IPv6), return the canonical hostname.
Returns C<undef> if no PTR record exists for the IP.
=cut
sub hostname_from_ip {
my $ip = shift;
return unless $ip;
# check /etc/hosts file and short-circuit if found
foreach my $name (reverse sort keys %HOSTS) {
if ($HOSTS{$name}->[0]->[0] eq $ip) {
return $name;
}
}
my $res = Net::DNS::Resolver->new;
my $query = $res->search($ip);
if ($query) {
foreach my $rr ($query->answer) {
next unless $rr->type eq "PTR";
return $rr->ptrdname;
}
}
return undef;
}
=head2 ipv4_from_hostname( $name )
Given a host name will return the first IPv4 address.
Returns C<undef> if no A record exists for the name.
=cut
sub ipv4_from_hostname {
my $name = shift;
return unless $name;
# check /etc/hosts file and short-circuit if found
if (exists $HOSTS{$name} and $HOSTS{$name}->[0]->[0]) {
my $ip = NetAddr::IP::Lite->new($HOSTS{$name}->[0]->[0]);
return $ip->addr if $ip and $ip->bits == 32;
}
my $res = Net::DNS::Resolver->new;
my $query = $res->search($name);
if ($query) {
foreach my $rr ($query->answer) {
next unless $rr->type eq "A";
return $rr->address;
}
}
return undef;
}
=head2 hostnames_resolve_async( $ips )
This method uses a fully asynchronous and high-performance pure-perl stub
resolver C<AnyEvent::DNS>.
Given a reference to an array of hashes will resolve the C<IPv4> or C<IPv6>
address in the C<ip> or C<alias> key of each hash into its hostname which
will be inserted in the C<dns> key of the hash.
Returns the supplied reference to an array of hashes with dns values for
addresses which resolved.
=cut
sub hostnames_resolve_async {
my $ips = shift;
# Set up the condvar
my $done = AE::cv;
$done->begin( sub { shift->send } );
IP: foreach my $hash_ref (@$ips) {
my $ip = $hash_ref->{'ip'} || $hash_ref->{'alias'};
next IP if no_resolve($ip);
# check /etc/hosts file and short-circuit if found
foreach my $name (reverse sort keys %HOSTS) {
if ($HOSTS{$name}->[0]->[0] eq $ip) {
$hash_ref->{'dns'} = $name;
next IP;
}
}
$done->begin;
AnyEvent::DNS::reverse_lookup $ip,
sub { $hash_ref->{'dns'} = shift; $done->end; };
}
# Decrement the cv counter to cancel out the send declaration
$done->end;
# Wait for the resolver to perform all resolutions
$done->recv;
# Remove reference to resolver so that we close sockets
undef $AnyEvent::DNS::RESOLVER if $AnyEvent::DNS::RESOLVER;
return $ips;
}
=head2 no_resolve( $ip )
Given an IP address, returns true if excluded from DNS resolution by the
C<dns_no> configuration directive, otherwise returns false.
=cut
sub no_resolve {
my $ip = shift;
my $config = setting('dns')->{no} || [];
return 0 if not scalar @$config;
my $addr = NetAddr::IP::Lite->new($ip);
foreach my $item (@$config) {
my $c_ip = NetAddr::IP::Lite->new($item)
or next;
next unless $c_ip->bits == $addr->bits;
return 1 if ($c_ip->contains($addr));
}
return 0;
}
1;