# File lib/racket.rb, line 45
  def initialize(payload="")
    @layers = []
    @mtu = 1500
    @timeout = 10
    @payload = payload
    1.upto(7) do |l|
      self.class.send(:define_method, "layer#{l}", lambda { @layers[l] })
      self.class.send(:define_method, "l#{l}", lambda { @layers[l] })
      self.class.send(:define_method, "layer#{l}=", lambda { |x| @layers[l] = x; })
      self.class.send(:define_method, "l#{l}=", lambda { |x| @layers[l] = x; })
    end
  end

# File lib/racket.rb, line 59
  def pack
    last_payload = ""
    orig_payload = ""
    @layers.compact.reverse.each do |l|
      # save the original payload
      orig_payload = l.payload
      # tack on the last payload in
      # case fix needs it...
      l.payload += last_payload
      if (l.autofix?)
        l.fix!
      end

      if (l.payload == orig_payload + last_payload)
        # payload was not modified by fix, so reset it to what
        # it used to be
        l.payload = orig_payload
      else
        # payload was modified by fix.  chop off what we added.
        # XXX: this assumes that what we added is still at the end.  
        # XXX: this is not always true
        l.payload = l.payload.slice(0, l.payload.length - last_payload.length)
      end

      # save this layer for the next guy
      last_payload += l
      
    end
    
    payload = ""
    @layers.compact.each do |l|
      payload += l
    end
    payload
  end

# File lib/racket.rb, line 95
  def pretty
    s = ""
    @layers.compact.each do |l|
      s << "#{l.class}: "
      s << l.pretty
      s << "\n"
    end
    s
  end

# File lib/racket.rb, line 116
  def send2
    begin
      p = Pcap::open_live(@iface, @mtu, false, @timeout)
    rescue Exception => e
      puts "Pcap: can't open device '#{@iface}' (#{e})"
      return
    end

    begin
      b = p.inject(pack)
      p.close
      return b
    rescue Exception => e
      puts "Pcap: error while sending packet on '#{@iface}' (#{e})"
    end
  end

# File lib/racket.rb, line 134
  def send3
    begin
      s = Socket.open(Socket::PF_INET, Socket::SOCK_RAW, Socket::IPPROTO_RAW)
      #s.setsockopt(Socket::SOL_IP, Socket::IP_HDRINCL, true)
    rescue Errno::EPERM
      $stderr.puts "Must run #{$0} as root."
      exit!
    end

    return s.send(pack, 0, Socket.pack_sockaddr_in(1024, @layers[3].dst_ip))
  end

# File lib/racket.rb, line 107
  def sendpacket
    if (@layers[2])
      send2
    else
      send3
    end
  end