code: def eth_addr(f):
      
      data = "%.2x:%.2x:%.2x:%.2x:%.2x:%.2x" % (f[0],
                                                f[1],
                                                f[2],
                                                f[3],
                                                f[4],
                                                f[5])
      return data
docs: eth_addr
  
      :param f: eth frame