Introduction

In this lab we will connect write our first SDN application and run it on the controller.

Goals

• Write an SDN application using the Ryu framework
• Start the application on the controller.

Notes

• Commands preceded with "$" imply that you should execute the command as a general user - not as root.
• Commands preceded with "#" imply that you should be working as root.
• Commands with more specific command lines (e.g. "RTR-GW>" or "mysql>") imply that you are executing commands on remote equipment, or within another program.

Installation

A very simple switch.

Open up a terminal on the controller and create the following file

$ vi ~/l2.py

It should contain the following

from ryu.base import app_manager
from ryu.controller import mac_to_port
from ryu.controller import ofp_event
from ryu.controller.handler import MAIN_DISPATCHER
from ryu.controller.handler import set_ev_cls
from ryu.ofproto import ofproto_v1_3
from ryu.lib.mac import haddr_to_bin
from ryu.lib.packet import packet
from ryu.lib.packet import ethernet

class L2Switch(app_manager.RyuApp):
    def __init__(self, *args, **kwargs):
        super(L2Switch, self).__init__(*args, **kwargs)

    @set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
    def packet_in_handler(self, ev):
        msg = ev.msg
        dp = msg.datapath
        ofp = dp.ofproto
        ofp_parser = dp.ofproto_parser
        in_port = msg.match['in_port']

        actions = [ofp_parser.OFPActionOutput(ofp.OFPP_FLOOD)]
        out = ofp_parser.OFPPacketOut(
            datapath=dp, buffer_id=msg.buffer_id, in_port=in_port,
            actions=actions)
        dp.send_msg(out)

With one window open on your controller, and the other window on your datapath element, start this application on the controller with the following command.

$ ryu-manager --verbose ~/l2.py

Then run the following on the datapath element

# /root/bootovs-rb532.sh 

Once everything has started you can confirm that the datapath element has contacted the controller

2014-01-28T04:56:02Z|00030|rconn|INFO|br0<->tcp:10.10.0.1:6633: connected

Every time a packet arrives on either of the datapath ports the following message will be printed on the controller screen

EVENT ofp_event->L2Switch EventOFPPacketIn
EVENT ofp_event->L2Switch EventOFPPacketIn
EVENT ofp_event->L2Switch EventOFPPacketIn
EVENT ofp_event->L2Switch EventOFPPacketIn
EVENT ofp_event->L2Switch EventOFPPacketIn
EVENT ofp_event->L2Switch EventOFPPacketIn

You can confirm this by having someone plug a laptop into the rb532

A more complicated switch

git clone https://code.google.com/r/dean-nsss/

ryu-manager --verbose ./dean-nsss/simple_switch_13.py

On the datapath element run the monitor_flows command

$ ./monitor_flows.sh

This should give the output similar to the following

Tue Jan 28 05:01:57 UTC 2014
OFPST_FLOW reply (OF1.3) (xid=0x2):
 cookie=0x0, duration=10.535s, table=0, n_packets=27, n_bytes=4624, priority=1,in_port=1,dl_src=3c:07:54:49:ee:97 actions=goto_table:1
 cookie=0x0, duration=93.21s, table=1, n_packets=3, n_bytes=1026, priority=10,dl_dst=ff:ff:ff:ff:ff:ff actions=ALL
 cookie=0x0, duration=93.21s, table=1, n_packets=0, n_bytes=0, priority=5,dl_type=0x88cc actions=drop
 cookie=0x0, duration=93.21s, table=1, n_packets=0, n_bytes=0, priority=5,dl_type=0x05ff actions=drop
 cookie=0x0, duration=93.21s, table=1, n_packets=15, n_bytes=3058, priority=11,dl_dst=33:33:00:00:00:00/ff:ff:00:00:00:00 actions=ALL
 cookie=0x0, duration=93.21s, table=1, n_packets=0, n_bytes=0, priority=10,dl_dst=01:00:00:00:00:00/01:00:00:00:00:00 actions=ALL
 cookie=0x0, duration=93.21s, table=1, n_packets=9, n_bytes=540, priority=0 actions=FLOOD,CONTROLLER:64

--End