#!/usr/bin/env ruby
#
# $Id: udp 174 2010-08-21 22:26:52Z jhart $
#
# Send random garbage to a UDP port 
require 'rubygems'
require 'racket'
include Racket
unless (ARGV.size == 4) 
  puts "Usage: #{$0} <srcip> <dstip> <dst_port> <size>"
  exit
end
# create a new Racket object and pick an interface
n = Racket::Racket.new
n.iface = "eth0"
# skip right to layer3, layer2 will be done automatically
# build a new IPv4 layer, and assign src and dst ip from the command line
n.l3 = L3::IPv4.new
n.l3.src_ip = ARGV[0] 
n.l3.dst_ip = ARGV[1]
n.l3.protocol = 0x11
# tack on UDP
n.l4 = L4::UDP.new
# randomize source port
n.l4.src_port = 1024 + rand(65535-1024)
# take destination port from the commandline
n.l4.dst_port = ARGV[2].to_i
# build a random amount of garbage for the payload
n.l4.payload = Misc.randstring(ARGV[3].to_i)
# fix 'er  up (checksum, length) prior to sending
n.l4.fix!(n.l3.src_ip, n.l3.dst_ip)
# off you go
f = n.sendpacket
# print out what we built
n.layers.compact.each do |l|
  puts l.pretty
end
puts "Sent #{f}"