#!/usr/bin/perl
#################################################################
# Anastasios Monachos (secuid0) - [anastasiosm(at)gmail(dot)com]
#
# Usage: perl dnsforver.pl start_ip_address end_ip_address
#	Example: perl dnsforver.pl 172.28.108.1 172.28.108.179
#
# Purpose: Check for consistency your reverse-forward DNS entries 
#
# Version: 0.1
#
# Demo:
#$perl dnsforver.pl 172.28.108.30 172.28.108.42
#
#IP is 172.28.108.30		Reverse lookup failed to find name	Hostname is 172.28.108.30 and maps to IPs: IP: 172.28.108.30	--No Reverse DNS record exists-- --DNS record matches--
#IP is 172.28.108.31		Hostname is lthp24xk.corp.dom.com	Lookup failed to find address	 and maps to IPs:  --No Forward DNS record exists--
#IP is 172.28.108.32		Reverse lookup failed to find name	Hostname is 172.28.108.32 and maps to IPs: IP: 172.28.108.32	--No Reverse DNS record exists-- --DNS record matches--
#IP is 172.28.108.33		Hostname is lthp1p8j.corp.dom.com	Lookup failed to find address	 and maps to IPs:  --No Forward DNS record exists--
#IP is 172.28.108.34		Hostname is lthp1plb.corp.dom.com	Lookup failed to find address	 and maps to IPs:  --No Forward DNS record exists--
#IP is 172.28.108.35		Hostname is lthp206q.corp.dom.com and maps to IPs: IP: 172.27.106.48	 --Probable MISMATCH !!!--
#IP is 172.28.108.36		Reverse lookup failed to find name	Hostname is 172.28.108.36 and maps to IPs: IP: 172.28.108.36	--No Reverse DNS record exists-- --DNS record matches--
#IP is 172.28.108.37		Reverse lookup failed to find name	Hostname is 172.28.108.37 and maps to IPs: IP: 172.28.108.37	--No Reverse DNS record exists-- --DNS record matches--
#IP is 172.28.108.38		Reverse lookup failed to find name	Hostname is 172.28.108.38 and maps to IPs: IP: 172.28.108.38	--No Reverse DNS record exists-- --DNS record matches--
#IP is 172.28.108.39		Reverse lookup failed to find name	Hostname is 172.28.108.39 and maps to IPs: IP: 172.28.108.39	--No Reverse DNS record exists-- --DNS record matches--
#IP is 172.28.108.40		Hostname is srv01.corp.dom.com		Lookup failed to find address	 and maps to IPs:  --No Forward DNS record exists--
#IP is 172.28.108.41		Hostname is dthp2gwh.corp.dom.com and maps to IPs: IP: 172.28.108.41	 --DNS record matches--
#IP is 172.28.108.42		Hostname is lthp1r87.corp.dom.com and maps to IPs: IP: 172.28.110.147	 --Probable MISMATCH !!!--
#################################################################
use strict;
use warnings;
use Socket qw(AF_INET);

sub usage()
{
        print STDERR << "EOF";
        ********************************************************************************************
        Usage: perl $0 start_ip_address end_ip_address 
        ********************************************************************************************
EOF
        exit;
}

if ($#ARGV != 1 ) 
{
	usage();
}

my $start = ip_from_dotted($ARGV[0]);
my $end = ip_from_dotted($ARGV[1]);
my $ip1;
my $ip2; 

for (my $ip=$start; $ip<=$end; $ip++) 
{
	dnslookup_info(ip_to_dotted($ip));
}

sub dnslookup_info 
{
	foreach (shift) 
	{
	my $host1='0';

  	my ($ip, $host, $aliases, $addrtype, $length, @addrs);
  	$ip = $_;
  	
	if ( /^(\d+)\.(\d+)\.(\d+)\.(\d+)$/ ) 
	{
    		print "IP is $ip\t"; $ip1=$ip;
    		($host, $aliases, $addrtype, $length, @addrs) = gethostbyaddr( pack( 'C4', $1, $2, $3, $4 ), AF_INET );

    		unless($host)
        	{
                	print "\tReverse lookup failed to find name\t";
                	$host1='-1';
        	}
  	}

	$host = $ip unless $host;
  	print "\tHostname is ".$host;
  	($host, $aliases, $addrtype, $length, @addrs) = gethostbyname( $host );

	unless(@addrs)
	{
   	  	print "\tLookup failed to find address\t"; 
		$ip1='-2';
	}
	
  	print " and maps to IPs: ";

  	foreach (@addrs) 
	{
    		print "IP: ".join( '.', unpack( 'C4', $_ ) )."\t"; $ip2= join( '.', unpack( 'C4', $_ ) );
  	}

        if ($host1 eq '-1')
                {print "--No Reverse DNS record exists--";}
	
	if ($ip1 eq '-2')
		{print " --No Forward DNS record exists--";}
	elsif ($ip1 eq $ip2)
		{print " --DNS record matches--";}
	elsif ($ip1 ne $ip2)
		{print " --Probable MISMATCH !!!--";}
	}
	
	print "\n";
}

sub ip_from_dotted { unpack 'N', pack 'C4', split /\./, $_[0] }
sub ip_to_dotted { join '.', unpack 'C4', pack 'N', $_[0] }