实验6：开源控制器实践——RYU

实验目的

1、能够独立部署RYU控制器；
2、能够理解RYU控制器实现软件定义的集线器原理；
3、能够理解RYU控制器实现软件定义的交换机原理。

实验要求

（一）基本要求

1.搭建下图所示SDN拓扑，协议使用Open Flow 1.0，并连接Ryu控制器，通过Ryu的图形界面查看网络拓扑。

建立拓扑 sudo mn --topo=single,3 --mac --controller=remote,ip=127.0.0.1,port=6633 --switch ovsk

连接Ryu控制器 ryu-manager ryu/ryu/app/gui_topology/gui_topology.py --observe-links

通过Ryu的图形界面查看网络拓扑
在浏览器中输入地址http://127.0.0.1:8080即可打开ryu的图形界面

2.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。
创建L2Switch文件并添加代码

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

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)

运行L2Switch ryu-manager L2Switch.py
pingall可以ping通

开启主机终端 mininet>xterm h2 h3
在h2主机终端中输入tcpdump -nn -i h2-eth0
在h3主机终端中输入tcpdump -nn -i h3-eth0
h1 ping h2

h1 ping h3

分析L2Switch和POX的Hub模块有何不同
Hub和L2Switch模块都是洪泛转发，但L2Switch模块下发的流表无法查看，而Hub模块下发的流表可以查看
3.编程修改L2Switch.py，另存为L2xxxxxxxxx.py，使之和POX的Hub模块的变得一致？（xxxxxxxxx为学号）
代码

from ryu.base import app_manager
from ryu.ofproto import ofproto_v1_3
from ryu.controller import ofp_event
from ryu.controller.handler import MAIN_DISPATCHER, CONFIG_DISPATCHER
from ryu.controller.handler import set_ev_cls


class hub(app_manager.RyuApp):
   OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]

   def __init__(self, *args, **kwargs):
       super(hub, self).__init__(*args, **kwargs)

   @set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER)
   def switch_feathers_handler(self, ev):
       datapath = ev.msg.datapath
       ofproto = datapath.ofproto
       ofp_parser = datapath.ofproto_parser

       # install flow table-miss flow entry
       match = ofp_parser.OFPMatch()
       actions = [ofp_parser.OFPActionOutput(ofproto.OFPP_CONTROLLER, ofproto.OFPCML_NO_BUFFER)]
       # 1\OUTPUT PORT, 2\BUFF IN SWITCH?
       self.add_flow(datapath, 0, match, actions)

   def add_flow(self, datapath, priority, match, actions):
       # 1\ datapath for the switch, 2\priority for flow entry, 3\match field, 4\action for packet
       ofproto = datapath.ofproto
       ofp_parser = datapath.ofproto_parser
       # install flow
       inst = [ofp_parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS, actions)]
       mod = ofp_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):
       msg = ev.msg
       datapath = msg.datapath
       ofproto = datapath.ofproto
       ofp_parser = datapath.ofproto_parser
       in_port = msg.match['in_port']  # get in port of the packet

       # add a flow entry for the packet
       match = ofp_parser.OFPMatch()
       actions = [ofp_parser.OFPActionOutput(ofproto.OFPP_FLOOD)]
       self.add_flow(datapath, 1, match, actions)

       # to output the current packet. for install rules only output later packets
       out = ofp_parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id, in_port=in_port, actions=actions)
       # buffer id: locate the buffered packet
       datapath.send_msg(out)

运行结果：
运行ryu-manager L2xxxxxxxxx.py
mininet>dpctl dump-flows

（二）进阶要求

1.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.

# 引入数据包
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 = {}  # 定义保存mac地址到端口的一个映射

   # 处理SwitchFeatures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()  # match指流表项匹配，OFPMatch()指不匹配任何信息
       actions = [parser.OFPActionOutput(ofproto.OFPP_CONTROLLER,
                                         ofproto.OFPCML_NO_BUFFER)]
       self.add_flow(datapath, 0, match, actions)

   # add_flow()增加流表项
   # datapath：指定的 Switch
   # priority：此规则的优先权
   # match：此规则的 Match 条件
   # actions：动作
   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)]
       # 判断是否存在buffer_id，并生成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)
       # 发送出去
       datapath.send_msg(mod)

   # 处理PacketIn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)
       # 解析数据结构
       msg = ev.msg    # ev.msg 是代表packet_in data structure对象
       datapath = msg.datapath
       # dp. ofproto 和 dp.ofproto_parser 是代表 Ryu 和交换机谈判的 OpenFlow 协议的对象
       # dp.ofproto and dp.ofproto_parser are objects that represent the OpenFlow protocol that Ryu and the switch negotiated
       ofproto = datapath.ofproto
       parser = datapath.ofproto_parser
       in_port = msg.match['in_port']  # 获取源端口

       pkt = packet.Packet(msg.data)
       eth = pkt.get_protocols(ethernet.ethernet)[0]

       if eth.ethertype == ether_types.ETH_TYPE_LLDP:
           # 忽略LLDP类型的数据包
           # ignore lldp packet
           return
       dst = eth.dst  # 获取目的端口
       src = eth.src  # 获取源端口

       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]:  # 如果目的地址存在于mac_to_port中
           out_port = self.mac_to_port[dpid][dst]
       # 否则，洪泛
       else:
           out_port = ofproto.OFPP_FLOOD  # OFPP_FLOOD标志表示应在所有端口发送数据包，即洪泛

       actions = [parser.OFPActionOutput(out_port)]

       # 下发流表避免下次触发 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

       # 发送Packet_out数据包
       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？

mac_to_port的作用是保存mac地址到交换机端口的映射

b) simple_switch和simple_switch_13在dpid的输出上有何不同？

在simple_switch_13.py中为dpid = format(datapath.id, "d").zfill(16)
在simple_switch.py中为dpid = datapath.id
在simple_switch_13.py中使用了zfill() 方法返回指定长度为16的字符串，原字符串右对齐，前面填充0；而simple_switch.py直接输出dpid

c) 相比simple_switch，simple_switch_13增加的switch_feature_handler实现了什么功能？

增加了实现交换机以特性应答消息响应特性请求功能

d) simple_switch_13是如何实现流规则下发的？

在触发PacketIn事件后，首先解析相关数据结构，获取协议信息、获取源端口、包学习，交换机信息，以太网信息，等。如果以太网类型是LLDP类型，则忽略。如果不是LLDP类型，则获取目的端口和源端口还有交换机id，然后进行交换机自学习，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，如果没有就洪泛转发。如果学习过，则查看是否有buffer_id，如果有则在添加流时加上buffer_id，向交换机发送数据包和流表。

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？

switch_features_handler下发流表的优先级比_packet_in_handler高

2.编程实现和ODL实验的一样的硬超时功能。
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)

建立拓扑sudo mn --topo=single,3 --mac --controller=remote,ip=127.0.0.1,port=6633 --switch ovsk
运行ryu-manager timeout.py
h1 ping h2

查看流表 dpctl dump-flows

个人总结

实验最开始，在打开ryu的时候遇到了各种bug，耗费了较大的时间通过网络各种查找资料询问同学，最终得以解决，比如'AttributeError: module 'collections' has no attribute 'MutableMapping'错误，在查询之后，网上给出的答案是python3.10中'MutableMapping,MutableSet'放的位置变了，所以需要在'Nameddict.py'文件中将'collections.MutableMapping'改为'collections.abc.MutableMapping'，按照这种方法做了也确实成功。本次实验的难度和上次差不多，但是有了上次的经验，要觉得更为简单，也是很顺利地完成了。通过这次实验，也学到了独立部署RYU控制器，大致了解了ryu控制器实现软件定义地交换机原理。