Mastering Python Networking

Ryu packet generation

In order to respond to the ARP requests, we need to do the following:

• Catch the ARP request based on the right switch, or datapath, and know the IP it is sending an ARP for
• Build the ARP response packet
• Send the response back out the port it was originally received from

In initial part of the PacketIn function, most of the code is identical to the switch function, which corresponds to decoding the OpenFlow event as well as the packet itself. For our purposes, we do not need ofproto and parser for OpenFlow events, but for consistency, we are leaving them in:

@set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)def _packet_in_handler(self, ev):    msg = ev.msg    datapath = msg.datapath    ofproto = datapath.ofproto    parser ...