$cb->(map $_->[3], @_);
   });
}

sub any($$) {
   my ($domain, $cb) = @_;

   resolver->resolve ($domain => "*", $cb);
}

# convert textual ip address into reverse lookup form
sub _munge_ptr($) {
   my $ipn = $_[0]
      or return;

   my $ptr;

   my $af = AnyEvent::Socket::address_family ($ipn);

   if ($af == AF_INET6) {
      $ipn = substr $ipn, 0, 16; # anticipate future expansion

      # handle v4mapped and v4compat
      if ($ipn =~ s/^\x00{10}(?:\xff\xff|\x00\x00)//) {
         $af = AF_INET;
      } else {
         $ptr = join ".", (reverse split //, unpack "H32", $ipn), "ip6.arpa.";
      }
   }

   if ($af == AF_INET) {
      $ptr = join ".", (reverse unpack "C4", $ipn), "in-addr.arpa.";
   }

   $ptr
}

sub reverse_lookup($$) {
   my ($ip, $cb) = @_;

   $ip = _munge_ptr AnyEvent::Socket::parse_address ($ip)
      or return $cb->();

   resolver->resolve ($ip => "ptr", sub {
      $cb->(map $_->[3], @_);
   });
}

sub reverse_verify($$) {
   my ($ip, $cb) = @_;
   
   my $ipn = AnyEvent::Socket::parse_address ($ip)
      or return $cb->();

   my $af = AnyEvent::Socket::address_family ($ipn);

   my @res;
   my $cnt;

   my $ptr = _munge_ptr $ipn
      or return $cb->();

   $ip = AnyEvent::Socket::format_address ($ipn); # normalise into the same form

   ptr $ptr, sub {
      for my $name (@_) {
         ++$cnt;
         
         # () around AF_INET to work around bug in 5.8
         resolver->resolve ("$name." => ($af == (AF_INET) ? "a" : "aaaa"), sub {
            for (@_) {
               push @res, $name
                  if $_->[3] eq $ip;
            }
            $cb->(@res) unless --$cnt;
         });
      }

      $cb->() unless $cnt;
   };
}

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

=back

=head2 LOW-LEVEL DNS EN-/DECODING FUNCTIONS

=over 4

=item $AnyEvent::DNS::EDNS0

This variable decides whether dns_pack automatically enables EDNS0
support. By default, this is disabled (C<0>), unless overridden by
C<$ENV{PERL_ANYEVENT_EDNS0}>, but when set to C<1>, AnyEvent::DNS will use
EDNS0 in all requests.

=cut

our $EDNS0 = $ENV{PERL_ANYEVENT_EDNS0} * 1; # set to 1 to enable (partial) edns0