#!/usr/bin/perl
##################
# Copyright (c) 2003, Anthony Volodkin <anthonyv@brainlink.com>
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
#
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
#
# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.
###################
# Rewrites diverted UDP broadcasts to be sent directly to certain hosts.

#note that the custom Net::Divert is required. Maybe it will be v0.02? 
use Net::Divert; 
use NetPacket::IP qw(IP_PROTO_UDP); 
use NetPacket::UDP;

#this is the list of all desired recipients of the received broadcast packets.
@master_target_list=("10.10.10.2", "192.168.44.2" );

#target_list is the dynamic array where each entry that
#already received a packet is removed. 
@target_list=@master_target_list;

#makes a DIVERT socket on host 192.168.1.1 port 9999 and defines the handler function
$divobj = Net::Divert->new('192.168.1.1',9999); 
$divobj->getPackets(\&alterPacket); 

sub alterPacket { 

	#separate the packet from the ipfw rule tag
	my ($data, $fwtag) = @_; 

	#create proper IP and UDP objects for packet processing
    	$ip_obj = NetPacket::IP->decode($data);
	$udp_obj = NetPacket::UDP->decode($ip_obj->{data});
   
	#not really necessary but it does make sure this is a
	#udp packet. 
	if($ip_obj->{proto} == IP_PROTO_UDP) {


	#if there is more than 1 ip left in the array --
	#this matters because depending on the number of 
	#elements in the array, we have to either reinitialize it 
	#and tell the Divert module that this is our last packet to be copied
	#or send another packet.
	if ( $target_list[1] ) { 

		$ip = shift(@target_list);

		#makes sure we dont send the packet where it came from	
	 	unless ($ip eq $ip_obj->{src_ip}) { 	
			#changes the destination ip to one from the array
			#and recalculates the checksums, etc of the packet
			$ip_obj->{dest_ip}=$ip;
			$ip_obj->{data} = $udp_obj->encode($ip_obj);
			$data= $ip_obj->encode;
		
			#the 1 in the arguments indicates there are more
			#packet copies to follow.
			$divobj->putPacket($data,$fwtag,1);
		} else {
		#get rid of it by sending to localhost.
			$ip_obj->{dest_ip}="127.0.0.1";
			$ip_obj->{data} = $udp_obj->encode($ip_obj);
                        $data= $ip_obj->encode;

                	$divobj->putPacket($data,$fwtag,1);
		}
	#if the array is empty, then load it with a copy of master_target_list
	#and start anew. This occurs when the program is started or
	#when a _BRAND_NEW_ packet is received.
	} elsif (! $target_list[0]) {
		@target_list=@master_target_list;
		$ip = shift(@target_list);
	
		unless ($ip eq $ip_obj->{src_ip}) {
                	$ip_obj->{dest_ip}=$ip;
			$ip_obj->{data} = $udp_obj->encode($ip_obj);
                        $data= $ip_obj->encode;

        	        $divobj->putPacket($data,$fwtag,1);
		} else {
			$ip_obj->{dest_ip}="127.0.0.1";
			$ip_obj->{data} = $udp_obj->encode($ip_obj);
                        $data= $ip_obj->encode;

       		        $divobj->putPacket($data,$fwtag,1);
		}
	#we have exactly 1 destination left to send to
	} else {
		$ip = shift(@target_list);
        
		unless ($ip eq $ip_obj->{src_ip}) {
	     		 $ip_obj->{dest_ip}=$ip;
			 $ip_obj->{data} = $udp_obj->encode($ip_obj);
                         $data= $ip_obj->encode;
			
			 #the 0 is set to indicate that this is the last packet
			 #in the series of re-transmissions to different hosts.
			 #the module discards the packet and then waits for a new one.
       		         $divobj->putPacket($data,$fwtag,0);
		} else {
			$ip_obj->{dest_ip}="127.0.0.1";
			$ip_obj->{data} = $udp_obj->encode($ip_obj);
                        $data= $ip_obj->encode;

                	$divobj->putPacket($data,$fwtag,0);
		}

	}

 	}

}