#!/usr/bin/env ruby
#
# $Id: tcp2udp 174 2010-08-21 22:26:52Z jhart $
#
#
# Spew TCP packets back at the source but in UDP form.  Gross.
# Pointless.
require 'rubygems'
require 'pcaprub'
require 'racket'
include Racket
if (ARGV.size < 1)
  puts "Usage: #{$0} <iface> [filter]"
  exit
end
begin
  p = Pcap::open_live(ARGV[0], 1500, true, 1000)
  unless (ARGV[1].nil?)
    p.setfilter(ARGV[1])
  end
rescue Exception => e
  puts "Pcap: Cannot open device #{ARGV[0]}: #{e}"
  exit
end
p.each do |pkt|
  if (p.datalink == Pcap::DLT_EN10MB) 
    eth = L2::Ethernet.new(pkt)
    case eth.ethertype
      when 0x0800:
        orig_ipv4 = L3::IPv4.new(eth.payload)
        if (orig_ipv4.protocol == 6) 
          n = Racket::Racket.new
          orig_tcp = L4::TCP.new(orig_ipv4.payload)
          if (!orig_tcp.payload.nil?)
            n.l3 = L3::IPv4.new
            n.l4 = L4::UDP.new
            n.l4.src_port = orig_tcp.dst_port
            n.l4.dst_port = orig_tcp.src_port
            n.l3.src_ip = orig_ipv4.dst_ip
            n.l3.dst_ip = orig_ipv4.src_ip
            n.l3.protocol = 17
            n.l4.payload = orig_tcp.payload
            n.l4.fix!(n.l3.src_ip, n.l3.dst_ip)
            f = n.sendpacket
            puts "Sent #{f}"
            n.layers.compact.each do |l|
              puts l.pretty
            end
            exit
          end
        end
    end
  end
end
# vim: set ts=2 et sw=2: