new_contents: import struct
  import socket
  from common import checksum
  
  class UDP(object):
      def __init__(self, src, dst, payload=''):
          self.srcp = src
          self.dstp = dst
          self.payload = payload
          self.checksum = 0
          self.length = 8 # UDP Header length
      def pack(self, src, dst, proto=socket.IPPROTO_UDP):
          length = self.length + len(self.payload)
          pseudo_header = struct.pack('!4s4sBBH', src, dst, 0, 
              proto, length)
          self.checksum = checksum(pseudo_header)
          packet = struct.pack('!HHHH',
              self.srcp, self.dstp, length, 0)
          return packet
  
subject: Update and rename latest/protocol to latest/protocol/udp.py