#!/usr/bin/perl -w
#
# simple frontend for dig(1)
#

use strict;
my $tracing = 1;

sub usage {
        print <<EOM;
usage: $0 ipaddr
EOM
        exit(1);
}

my $ipaddr = shift @ARGV || usage();
my @ipaddr = split(/\./ , $ipaddr);

# work our way through the parts of the ip address, stopping
# when we're down to 1.
do {
    dig_on(@ipaddr);
    pop @ipaddr;
} until ( @ipaddr == 1 );

sub dig_on {
    my @addr = @_;

    my $subaddr = join('.', @addr);
    my $revaddr = join('.', reverse @ipaddr);

    print "going after $subaddr ...\n" if $tracing;

    open(IN, "dig -x $subaddr | grep $revaddr | ")
        or die "open(): $!";
    while ( <IN> ) {
        next if /^;/;
        print;
    }
    close(IN);
}