code: def _add_flow_v1_2(self, src, port, timeout, datapath):
          
          ofproto = datapath.ofproto
          parser = datapath.ofproto_parser
  
          match = parser.OFPMatch(
              in_port=port, eth_src=src, eth_type=ether.ETH_TYPE_SLOW)
          actions = [parser.OFPActionOutput(
              ofproto.OFPP_CONTROLLER, ofproto.OFPCML_MAX)]
          inst = [parser.OFPInstructionActions(
              ofproto.OFPIT_APPLY_ACTIONS, actions)]
          mod = parser.OFPFlowMod(
              datapath=datapath, command=ofproto.OFPFC_ADD,
              idle_timeout=timeout, priority=65535,
              flags=ofproto.OFPFF_SEND_FLOW_REM, match=match,
              instructions=inst)
          datapath.send_msg(mod)
docs: enter a flow entry for the packet from the slave i/f
          with idle_timeout. for OpenFlow ver1.2 and ver1.3.