Pox代码疑问

 1 # Method for just sending a packet to any port (broadcast by default)
 2 def send_packet (event, dst_port = of.OFPP_ALL):
 3   msg = of.ofp_packet_out(in_port=event.ofp.in_port)
 4   if event.ofp.buffer_id != -1 and event.ofp.buffer_id is not None:

 5     # We got a buffer ID from the switch; use that
 6     msg.buffer_id = event.ofp.buffer_id
 7   else:
 8     # No buffer ID from switch -- we got the raw data
 9     if event.ofp.data:
10       # No raw_data specified -- nothing to send!
11       return
12     msg.data = event.ofp.data
13   msg.actions.append(of.ofp_action_output(port = dst_port))
14   event.connection.send(msg)