package App::Netdisco::Util::DNS;
use strict;
use warnings;
use Dancer ':script';
use Net::DNS;
use NetAddr::IP::Lite ':lower';
use base 'Exporter';
our @EXPORT = ();
our @EXPORT_OK = qw/hostname_from_ip ipv4_from_hostname/;
our %EXPORT_TAGS = (all => \@EXPORT_OK);
=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( $ip, \%opts? )
Given an IP address (either IPv4 or IPv6), return the canonical hostname.
C<< %opts >> can override the various timeouts available in
L<Net::DNS::Resolver>:
=over 4
=item C<tcp_timeout>: 120 (seconds)
=item C<udp_timeout>: 30 (seconds)
=item C<retry>: 4 (attempts)
=item C<retrans>: 5 (timeout)
=back
Returns C<undef> if no PTR record exists for the IP.
=cut
sub hostname_from_ip {
my ($ip, $opts) = @_;
return unless $ip;
my $ETCHOSTS = setting('dns')->{'ETCHOSTS'};
# check /etc/hosts file and short-circuit if found
foreach my $name (reverse sort keys %$ETCHOSTS) {
if ($ETCHOSTS->{$name}->[0]->[0] eq $ip) {
return $name;
}
}
my $res = Net::DNS::Resolver->new;
$res->tcp_timeout($opts->{tcp_timeout} || 120);
$res->udp_timeout($opts->{udp_timeout} || 30);
$res->retry($opts->{retry} || 4);
$res->retrans($opts->{retrans} || 5);
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;
my $ETCHOSTS = setting('dns')->{'ETCHOSTS'};
# check /etc/hosts file and short-circuit if found
if (exists $ETCHOSTS->{$name} and $ETCHOSTS->{$name}->[0]->[0]) {
my $ip = NetAddr::IP::Lite->new($ETCHOSTS->{$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;
}
1;