1.浏览RYU官网学习RYU控制器的安装和RYU开发入门教程，提交你对于教程代码的理解，包括但不限于：
描述官方教程实现了一个什么样的交换机功能？
Add some features to enable the switch to forward the received packets to all ports.
控制器设定交换机支持什么版本的OpenFlow？
支持OpenFlow v1.0
控制器设定了交换机如何处理数据包？
@set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
//表明当Ryu收到OpenFlow packet_in消息时，将产生事件（调用“packet_in_handler”方法）
def packet_in_handler(self, ev):
msg = ev.msg
dp = msg.datapath
ofp = dp.ofproto
ofp_parser = dp.ofproto_parser
actions = [ofp_parser.OFPActionOutput(ofp.OFPP_FLOOD)]
//动作列表。OFPActionOutput类与packet_out消息一起使用，以指定要从中发送数据包的交换机端口。该应用程序使用OFPP_FLOOD标志来指示应在所有端口上发送数据包。
out = ofp_parser.OFPPacketOut(
datapath=dp, buffer_id=msg.buffer_id, in_port=msg.in_port,
actions=actions)
dp.send_msg(out)2.根据官方教程和提供的示例代码（SimpleSwitch.py），将具有自学习功能的交换机代码（SelfLearning.py）补充完整
补充后的完整代码：
from ryu.base import app_manager
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_0
from ryu.lib.mac import haddr_to_bin
from ryu.lib.packet import packet
from ryu.lib.packet import ethernet
from ryu.lib.packet import ether_types
class SimpleSwitch(app_manager.RyuApp):
# TODO define OpenFlow 1.0 version for the switch
OFP_VERSIONS = [ofproto_v1_0.OFP_VERSION]
# add your code here
def __init__(self, *args, **kwargs):
super(SimpleSwitch, self).__init__(*args, **kwargs)
self.mac_to_port = {}
def add_flow(self, datapath, in_port, dst, src, actions):
ofproto = datapath.ofproto
match = datapath.ofproto_parser.OFPMatch(
in_port=in_port,
dl_dst=haddr_to_bin(dst), dl_src=haddr_to_bin(src))
mod = datapath.ofproto_parser.OFPFlowMod(
datapath=datapath, match=match, cookie=0,
command=ofproto.OFPFC_ADD, idle_timeout=0, hard_timeout=0,
priority=ofproto.OFP_DEFAULT_PRIORITY,
flags=ofproto.OFPFF_SEND_FLOW_REM, actions=actions)
# TODO send modified message out
# add your code here
datapath.send_msg(mod)
@set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
def _packet_in_handler(self, ev):
msg = ev.msg
datapath = msg.datapath
ofproto = datapath.ofproto
pkt = packet.Packet(msg.data)
eth = pkt.get_protocol(ethernet.ethernet)
if eth.ethertype == ether_types.ETH_TYPE_LLDP:
# ignore lldp packet
return
if eth.ethertype == ether_types.ETH_TYPE_IPV6:
# ignore ipv6 packet
return
dst = eth.dst
src = eth.src
dpid = datapath.id
self.mac_to_port.setdefault(dpid, {})
self.logger.info("packet in DPID:%s MAC_SRC:%s MAC_DST:%s IN_PORT:%s", dpid, src, dst, msg.in_port)
# learn a mac address to avoid FLOOD next time.
self.mac_to_port[dpid][src] = msg.in_port
if dst in self.mac_to_port[dpid]:
out_port = self.mac_to_port[dpid][dst]
else:
out_port = ofproto.OFPP_FLOOD
# TODO define the action for output
# add your code here
actions = [datapath.ofproto_parser.OFPActionOutput(out_port)]
# install a flow to avoid packet_in next time
if out_port != ofproto.OFPP_FLOOD:
self.logger.info("add flow s:DPID:%s Match:[ MAC_SRC:%s MAC_DST:%s IN_PORT:%s ], Action:[OUT_PUT:%s] ", dpid, src, dst, msg.in_port, out_port)
self.add_flow(datapath, msg.in_port, dst, src, actions)
data = None
if msg.buffer_id == ofproto.OFP_NO_BUFFER:
data = msg.data
out = datapath.ofproto_parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id, in_port=msg.in_port,actions=actions, data=data)
datapath.send_msg(out)3.创建一个最简拓扑，并连接RYU控制器
在SimpleSwitch.py目录下运行：
ryu-manager selflearning.py在本机使用mininet创建最简拓扑：
sudo mn --controller=remote,ip=127.0.0.1,port=66334.验证自学习交换机的功能，提交分析过程和验证结果
此时交换机s1上并无流表：
在Mininet CLI运行h1 ping h2，h1发送广播寻找h2，
再次使用sudo ovs-ofctl dump-flows s1查看流表：
h1 ping h2时，在wireshark抓包分析如下：
5.写下你的实验体会
安装是个漫长又艰难的过程，面临着虚拟机随时可能崩溃的危险，但按照老师的教程一步一步走下来，最终还是成功安装好了。ryu控制器的框架理解起来也有一定的困难，看了不少教程，稍微有些理解，通过实践，进一步加深理解。ryu比较灵活，可以用来打造属于自己风格的自定义控制器。