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
在Ryu安装目录下执行ryu --version查看版本
-
搭建下图所示SDN拓扑,协议使用Open Flow 1.0,并连接Ryu控制器。
-
拓扑可视化
-
tcpdump查看
h1 ping h2
h1 ping h3
可以看到均为洪泛转发
查看控制器流表,如下图:
看到没有流表,而使用pox的hub模块则会看到流表,如下图:
所以可以看到二者都是洪泛转发,但是不同之处在于POX是直接向交换机下发流表,而Ryu是在每个 Packet In 事件之后,向交换机下发动作。
(二)进阶要求
simple_switch_13.py
# 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)
# 定义保存mac地址到端口的一个映射
self.mac_to_port = {}
# 处理EventOFPSwitchFeatures事件
@set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER)
def switch_features_handler(self, ev):
datapath = ev.msg.datapath
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 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)
代码当中的mac_to_port的作用是什么?
保存mac地址到交换机端口的映射,为交换机自学习功能提供数据结构进行 mac-端口 的存储
simple_switch和simple_switch_13在dpid的输出上有何不同?
simple_switch的dpid赋值:dpid = datapath.id
simple_switch_13的dpid赋值:dpid = format(datapath.id, "d").zfill(16)
在python console进行测试,可以看到在simple_switch直接获取的id,在simple_switch_13中,会在前端加上0将其填充至16位
相比simple_switch,simple_switch_13增加的switch_feature_handler实现了什么功能?
实现交换机以特性应答消息响应特性请求
simple_switch_13是如何实现流规则下发的?
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。
实验总结
本次实验难度真的可以说是蛮大的,对源码分析和对openflow协议的理解的要求进一步提高,在拓扑可视化方面遇到了一些问题,但还是很好的解决了。体感实验六和实验五有一定相似性。在学习完本次实验后,我已经能够独立部署RYU控制器,并且能够理解RYU控制器实现软件定义的集线器原理,还能够理解RYU控制器实现软件定义的交换机原理。通过本次实验进一步加深了我对代码的理解,对我的学习有很大的帮助。