async dns support

Netdisco/lib/App/Netdisco/Util/DNS.pm

@@ -4,11 +4,12 @@ use strict;
 use warnings FATAL => 'all';
 
 use Net::DNS;
+use AnyEvent::DNS;
 
 use base 'Exporter';
 our @EXPORT = ();
 our @EXPORT_OK = qw/
-  hostname_from_ip ipv4_from_hostname
+  hostname_from_ip hostnames_resolve_async ipv4_from_hostname
 /;
 our %EXPORT_TAGS = (all => \@EXPORT_OK);
 
@@ -75,5 +76,46 @@ sub ipv4_from_hostname {
   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.  The resolver does also
+forward-lookups to verify that the resolved hostnames point to the
+address.
+
+Returns the supplied reference to an array of hashes with dns values for
+addresses which resolved.
+
+=cut
+
+sub hostnames_resolve_async {
+  my $ips = shift;
+
+  my $resolver = AnyEvent::DNS->new();
+    
+  # Set up the condvar
+  my $done = AE::cv;
+  $done->begin( sub { shift->send } );
+
+  foreach my $hash_ref (@$ips) {
+    my $ip = $hash_ref->{'ip'} || $hash_ref->{'alias'};
+    $done->begin;
+    AnyEvent::DNS::reverse_verify $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;
+
+  return $ips;
+}
+
 1;