#!/usr/bin/perl -w
#
# Run through a list of ip addresses and "stealthly" get
# the fqdn's for them.
# Hopefully, this will be a "quiet" zone transfer tool. :-)
# Harry Hoffman <hhoffman@ip-solutions.net>
#
use strict;
use Net::DNS;
use Net::IP;
use Getopt::Long;
use diagnostics;
use vars qw($opt_h $opt_n $opt_o $opt_s @servers $n $res 
            $packet $iaddr $record $fqdn);

$| = 1;

GetOptions('help|usage' => \$opt_h,
	   "netblock=s" => \$opt_n,
           "outfile|write=s" => \$opt_o,
           "servers=s" => \$opt_s
	  );

sub usage
{
my $name = $0;
print << "EOF";
Usage: $name -h 
Usage: $name -n <ipaddress/cidr> -w <file>
Usage: $name -n <ipaddress/cidr> -w <file> -s <file>
Usage: This script requires the "-n" flag followed by an ipaddress/cidr
       including the slash between them.
       The "-w" flag takes an argument of the directory and file to write
       the mappings of ipaddress to fqdn. It is required.
       The "-s" flag is optional and should be a file containing a list of
       nameservers, one per line.
EOF
exit(0);
}

sub getnsservers
{
   open (SERVERS, "$opt_s") or die "Can't open $opt_s, $!\n";
   while(<SERVERS>) {
        chomp;
        next if /^$/;
        if (/^\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3}$/) {
           push (@servers, $_);
        }
   }
   close (SERVERS);
}

{
	my $count=0;
   sub lookup
   {
      my @nsservers = @servers;
      $n = int($count++ % $#nsservers);
      $res = Net::DNS::Resolver->new;
      $res->nameservers("$nsservers[$n]");
      $packet = $res->query("$iaddr","PTR");
         if ($packet) {
            $record = ($packet->answer)[0];
            $fqdn = $record->rdatastr;
            chop($fqdn);
         }
   }
}

if ($opt_s) {
   getnsservers();
} else {
   @servers = ( "144.118.24.20",
                "144.118.24.10",
                "155.247.166.2",
                "155.247.19.2",
                "128.175.13.17",
                "128.91.2.13",
                "128.91.254.1",
                "18.72.0.3",
                "128.186.6.103",
                "128.186.8.8",
                "146.186.163.66",
                "130.132.1.9",
                "130.132.1.10",
                "130.132.1.11",
                "130.132.89.9",
                "128.135.4.2",
                "128.135.12.73",
                "128.135.20.100",
                "128.135.228.2",
                "128.109.131.40",
                "152.3.250.1",
                "152.3.250.2"
              );
}


if ($opt_h || !$opt_o || !$opt_n) { usage(); }

my $ip = new Net::IP("$opt_n") or die "No netblock/cidr supplied.\n";
open(OUTFILE, "> $opt_o") or die "Can't open file: $! \n";

do {
    $iaddr = $ip->ip();
    lookup($iaddr);
    if($fqdn)
    {
      print OUTFILE $iaddr."\t". $fqdn."\n";
    }
    else
    {
      print OUTFILE $iaddr."\t"."unassgn"."\n";
    }
    $fqdn = "";
} while (++$ip);

close(OUTFILE) or die "$opt_o didn't close $!";