实验六：开源控制器实践——RYU
一、实验目的
- 能够独立部署RYU控制器；
- 能够理解RYU控制器实现软件定义的集线器原理；
- 能够理解RYU控制器实现软件定义的交换机原理。
二、实验环境
- 下载虚拟机软件Oracle VisualBox或VMware；
- 在虚拟机中安装Ubuntu 20.04 Desktop amd64，并完整安装Mininet；
三、实验要求
（一）基本要求
-
完成Ryu控制器的安装。
-
搭建下图所示SDN拓扑，协议使用Open Flow 1.0，并连接Ryu控制器。
*
- 使用如下代码创建拓扑，在并且查看ｒｙｕ可视化拓扑
sudo mn --topo=single,3 --mac --controller=remote,ip=127.0.0.1,port=6633 --switch ovsk,protocols=OpneFlow10
但是这里的可视化界面无法显现（目前还没找到原因）
4. 阅读Ryu文档的The First Application一节，运行并使用 tcpdump 验证L2Switch，分析和POX的Hub模块有何不同。
- 编写L2Switch.py的脚本
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
class L2Switch(app_manager.RyuApp):
OFP_VERSIONS = [ofproto_v1_0.OFP_VERSION]
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
actions = [ofp_parser.OFPActionOutput(ofp.OFPP_FLOOD)]
data = None
if msg.buffer_id == ofp.OFP_NO_BUFFER:
data = msg.data
out = ofp_parser.OFPPacketOut(
datapath=dp, buffer_id=msg.buffer_id, in_port=msg.in_port,
actions=actions, data = data)
dp.send_msg(out)
-
h1 ping h2
-
h1 ping h3
-
无论ping哪个主机，拓扑的每个主机都会收到数据包，跟POX控制器的HUB一样采用洪泛式方式，区别是HUB会显示下发的流表，而ryu不会。
（二）进阶要求
- 阅读Ryu关于simple_switch.py和simple_switch_1x.py的实现，以simple_switch_13.py为例，完成其代码的注释工作，并回答下列问题：
# Copyright (C) 2011 Nippon Telegraph and Telephone Corporation.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
# implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#引入包
from ryu.base import app_manager
from ryu.controller import ofp_event
from ryu.controller.handler import CONFIG_DISPATCHER, MAIN_DISPATCHER
from ryu.controller.handler import set_ev_cls
from ryu.ofproto import ofproto_v1_3
from ryu.lib.packet import packet
from ryu.lib.packet import ethernet
from ryu.lib.packet import ether_types
class SimpleSwitch13(app_manager.RyuApp):
#定义openflow版本
OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]
def __init__(self, *args, **kwargs):
super(SimpleSwitch13, self).__init__(*args, **kwargs)
self.mac_to_port = {} #更新转发表
#相应ofp_event.EventOFPSwitchFeatures
@set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER)
def switch_features_handler(self, ev):
datapath = ev.msg.datapath #存储交换机信息
ofproto = datapath.ofproto
parser = datapath.ofproto_parser
# install table-miss flow entry
#
# We specify NO BUFFER to max_len of the output action due to
# OVS bug. At this moment, if we specify a lesser number, e.g.,
# 128, OVS will send Packet-In with invalid buffer_id and
# truncated packet data. In that case, we cannot output packets
# correctly. The bug has been fixed in OVS v2.1.0.
match = parser.OFPMatch()
actions = [parser.OFPActionOutput(ofproto.OFPP_CONTROLLER,
ofproto.OFPCML_NO_BUFFER)]
self.add_flow(datapath, 0, match, actions)
#添加流表函数
def add_flow(self, datapath, priority, match, actions, buffer_id=None):
#获取交换机信息
ofproto = datapath.ofproto
parser = datapath.ofproto_parser
#对action进行包装
inst = [parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS,
actions)]
#判断是否有buffer_id，生成mod对象
if buffer_id:
mod = parser.OFPFlowMod(datapath=datapath, buffer_id=buffer_id,
priority=priority, match=match,
instructions=inst)
else:
mod = parser.OFPFlowMod(datapath=datapath, priority=priority,
match=match, instructions=inst)
#发送mod
datapath.send_msg(mod)
#处理时间packet in事件
@set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
def _packet_in_handler(self, ev):
# If you hit this you might want to increase
# the "miss_send_length" of your switch
if ev.msg.msg_len < ev.msg.total_len:
self.logger.debug("packet truncated: only %s of %s bytes",
ev.msg.msg_len, ev.msg.total_len)
# 获取包信息，交换机信息，协议等等
msg = ev.msg
datapath = msg.datapath
ofproto = datapath.ofproto
parser = datapath.ofproto_parser
in_port = msg.match['in_port']
pkt = packet.Packet(msg.data)
eth = pkt.get_protocols(ethernet.ethernet)[0]
# 忽略LLDP类型
if eth.ethertype == ether_types.ETH_TYPE_LLDP:
# ignore lldp packet
return
# 获取源端口，目的端口
dst = eth.dst
src = eth.src
dpid = format(datapath.id, "d").zfill(16)
self.mac_to_port.setdefault(dpid, {})
self.logger.info("packet in %s %s %s %s", dpid, src, dst, in_port)
# 学习包的源地址，和交换机上的入端口绑定
# learn a mac address to avoid FLOOD next time.
self.mac_to_port[dpid][src] = in_port
# 查看是否已经学习过该目的mac地址
if dst in self.mac_to_port[dpid]:
out_port = self.mac_to_port[dpid][dst]
# 否则进行洪泛
else:
out_port = ofproto.OFPP_FLOOD
actions = [parser.OFPActionOutput(out_port)]
# 下发流表处理后续包，不再触发 packet in 事件
# install a flow to avoid packet_in next time
if out_port != ofproto.OFPP_FLOOD:
match = parser.OFPMatch(in_port=in_port, eth_dst=dst, eth_src=src)
# verify if we have a valid buffer_id, if yes avoid to send both
# flow_mod & packet_out
if msg.buffer_id != ofproto.OFP_NO_BUFFER:
self.add_flow(datapath, 1, match, actions, msg.buffer_id)
return
else:
self.add_flow(datapath, 1, match, actions)
data = None
if msg.buffer_id == ofproto.OFP_NO_BUFFER:
data = msg.data
out = parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id,
in_port=in_port, actions=actions, data=data)
# 发送流表
datapath.send_msg(out)
a) 代码当中的mac_to_port的作用是什么？
答：保存新的转发地址到转发表
b) simple_switch和simple_switch_13在dpid的输出上有何不同？
答：二者的dpid的赋值语句不同
#simple_switch
dpid = datapath.id
self.mac_to_port.setdefault(dpid, {})
#simple_switch_13
dpid = format(datapath.id, "d").zfill(16）
self.mac_to_port.setdefault(dpid, {})
c) 相比simple_switch，simple_switch_13增加的switch_feature_handler实现了什么功能？
答:实现交换机以特性应答消息响应特性请求
d) simple_switch_13是如何实现流规则下发的？
答：在接收到packetin事件后，首先获取包学习，交换机信息，以太网信息，协议信息等。如果以太网类型是LLDP类型，则不予处理。如果不是，则获取源端口目的端口，以及交换机id，先学习源地址对应的交换机的入端口，再查看是否已经学习目的mac地址，如果没有则进行洪泛转发。如果学习过该mac地址，则查看是否有buffer_id，如果有的话，则在添加流动作时加上buffer_id，向交换机发送流表。
e) switch_features_handler和_packet_in_handler两个事件在发送流规则的优先级上有何不同？
答：switch_features_handler下发流表的优先级比_packet_in_handler高
四、个人总结
实验难度：较难
遇到的问题及解决办法：
1. ryu的可视化界面无法出现，目前尚未解决
2. 创建拓扑之后，下发流表但是显示无法连接
但是在我重新试了很多遍之后它又可以了，晕
个人感想：这次是的实验和实验五差不太多，只是控制器不同，打开输入的命令也不相同而已，但是在这次实验中我遇到了一些奇怪的问题，然后莫名其妙的这些问题又解决了，不知道是不是系统配置的问题，还是虚拟机的版本问题，在windows桌面copy文件到虚拟机里面的时候老是蓝屏，大无语事件，还有就是与一个ryu的视图无法解决。
