实验6：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
Ubuntu 20.04 Desktop amd64
三、实验要求
（一）基本要求
阅读Ryu文档的The First Application一节，运行当中的L2Switch，h1 ping h2或h3，在目标主机使用 tcpdump 验证L2Switch，分析L2Switch和POX的Hub模块有何不同。
h1 ping h2
h1 ping h3
区别：L2Switch无法查看下发流表
编程修改L2Switch.py，另存为L2xxxxxxxxx.py，使之和POX的Hub模块的变得一致
运行结果
（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
点击查看代码
# 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.
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
# set_ev_cls指定事件类别得以接受事件消息和交换机状态作为参数
# set_ev_cls第一个参数表示事件发生时应该调用的函数，第二个参数告诉交换机只有在交换机握手完成之后，才可以被调用。
# ofp_event完成了事件的定义，从而我们可以在函数中注册handler，监听事件，并作出回应
# packet_in_handler方法用于处理packet_in事件。
# @set_ev_cls修饰符用于告知RYU，被修饰的函数应该被调用。
class SimpleSwitch13(app_manager.RyuApp):
OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION] # 指定OpenFlow 1.3版本
def __init__(self, *args, **kwargs):
super(SimpleSwitch13, self).__init__(*args, **kwargs)
# 定义MAC地址列表，mac_to_port表对应交换机的二层通信查询表
self.mac_to_port = {}
@set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER)
def switch_features_handler(self, ev):
# ev.msg 是用来存储对应事件的 OpenFlow 消息类别实体
# msg.datapath是用来存储OpenFlow交换机ryu.controller.controller.Datapath 类别所对应的实体
datapath = ev.msg.datapath
ofproto = datapath.ofproto
parser = datapath.ofproto_parser
# 下发table-miss流表项，让交换机对于不会处理的数据包通过packet-in消息上交给Ryu控制器
match = parser.OFPMatch()
actions = [parser.OFPActionOutput(ofproto.OFPP_CONTROLLER,
ofproto.OFPCML_NO_BUFFER)]
# 第一个是端口，第二是bufferid，若不为空，则去指定缓存区去查找流表
# 执行 add_flow() 方法以发送 Flow Mod 消息
self.add_flow(datapath, 0, match, actions)
# priority = 0 ，优先级最低，为了所有流表都匹配不到的时候，才会发送到controller
def add_flow(self, datapath, priority, match, actions, buffer_id=None):
# 新增流表项
ofproto = datapath.ofproto
parser = datapath.ofproto_parser
inst = [parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS,
actions)]
# 通过 Flow Mod 消息将 Flow Entry 新增到 Flow table 中
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)
datapath.send_msg(mod)
@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)
msg = ev.msg
datapath = msg.datapath
ofproto = datapath.ofproto
parser = datapath.ofproto_parser
# 更新Mac地址表
in_port = msg.match['in_port']
pkt = packet.Packet(msg.data)
eth = pkt.get_protocols(ethernet.ethernet)[0]
# pkt.get_protocols 传入的是 协议类 参数
if eth.ethertype == ether_types.ETH_TYPE_LLDP:
# ignore lldp packet
return
dst = eth.dst
src = eth.src
dpid = format(datapath.id, "d").zfill(16)
self.mac_to_port.setdefault(dpid, {})
# 指定交换机dpid，默认mac_to_port表为空
self.logger.info("packet in %s %s %s %s", dpid, src, dst, in_port)
# learn a mac address to avoid FLOOD next time.
self.mac_to_port[dpid][src] = in_port
if dst in self.mac_to_port[dpid]:
out_port = self.mac_to_port[dpid][dst]
# 有目的地址寻找端口号，否则泛洪
else:
out_port = ofproto.OFPP_FLOOD
actions = [parser.OFPActionOutput(out_port)]
# 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 # 不用泛洪退出函数
else:
self.add_flow(datapath, 1, match, actions)
# 在 MAC 地址表中找寻目的 MAC 地址，若是有找到则发送 Packet-Out 讯息，并且转送数据包。
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)
datapath.send_msg(out)
并回答下列问题：
a) 代码当中的mac_to_port的作用是什么？
mac_to_port表对应交换机的二层通信查询表 ，默认mac_to_port表为空
b) simple_switch和simple_switch_13在dpid的输出上有何不同？
simple_13中的dpid输出为：dpid = format(datapath.id, "d").zfill(16)，输出为指定字符串的长度，原字符串右对齐，前面填充0。
c) 相比simple_switch，simple_switch_13增加的switch_feature_handler实现了什么功能？
下发table-miss流表项
d) simple_switch_13是如何实现流规则下发的？
添加的if语句，表示流表下发缓存区id有无来区分下发,有缓存区id，到对应缓存区下发，无则自动分配，不传参buffer_id
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？
switch_features_handler下发流表的优先级高于_packet_in_handler
编程实现和ODL实验的一样的硬超时功能
代码
点击查看代码
# 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.
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):
OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]
def __init__(self, *args, **kwargs):
super(SimpleSwitch13, self).__init__(*args, **kwargs)
self.mac_to_port = {}
@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)
def add_flow(self, datapath, priority, match, actions, buffer_id=None, hard_timeout=0):
ofproto = datapath.ofproto
parser = datapath.ofproto_parser
inst = [parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS,
actions)]
if buffer_id:
mod = parser.OFPFlowMod(datapath=datapath, buffer_id=buffer_id,
priority=priority, match=match,
instructions=inst, hard_timeout=hard_timeout)
else:
mod = parser.OFPFlowMod(datapath=datapath, priority=priority,
match=match, instructions=inst, hard_timeout=hard_timeout)
datapath.send_msg(mod)
@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)
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]
if eth.ethertype == ether_types.ETH_TYPE_LLDP:
# ignore lldp packet
return
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)
# learn a mac address to avoid FLOOD next time.
self.mac_to_port[dpid][src] = in_port
if dst in self.mac_to_port[dpid]:
out_port = self.mac_to_port[dpid][dst]
else:
out_port = ofproto.OFPP_FLOOD
actions = [parser.OFPActionOutput(out_port)]\
actions_timeout=[]
# 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
hard_timeout=10
if msg.buffer_id != ofproto.OFP_NO_BUFFER:
self.add_flow(datapath, 2, match,actions_timeout, msg.buffer_id,hard_timeout=10)
self.add_flow(datapath, 1, match, actions, msg.buffer_id)
return
else:
self.add_flow(datapath, 2, match, actions_timeout, hard_timeout=10)
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)
datapath.send_msg(out)
流表
四、实验心得
- 本次实验总体难度不高，但由于在安装ryu时未将python-dev以及相关依赖创建好，导致花费了很多时间，后来了解到利用aptitude解决安装依赖问题的方法，才使得相关命令可以正确运行；
- 在进行进阶部分的实验时，由于对于实验原理不清楚，导致相关拓扑文件一直处于未连通状态。后来提前建立拓扑并启动ryu控制器以及运行ryu-manager timeout.py顺利完成硬超时实验；
- 本次实验主要了解了如何使用ryu控制器来查看网络拓扑，以及使用ryu-manager运行代码来更改连通性以及实现硬超时功能
