其他分享
首页 > 其他分享> > 软件定义网络实验六

软件定义网络实验六

作者：互联网

实验6：开源控制器实践——RYU

第一部分：基本实验

实验步骤1

实验步骤2

实验步骤3

实验步骤4

h1 ping h2

h1 ping h3

不同点：POX的下发流表可以查看，L2Switch的下发流表无法查看。

第二部分：进阶实验

实验内容：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：
注释结果如下:

  # 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)
    # 定义保存mac地址到端口的映射
    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):   
    #增加流表项
  # 获取交换机信息
    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)
    else:
        mod = parser.OFPFlowMod(datapath=datapath, priority=priority,
                                match=match, instructions=inst)
    datapath.send_msg(mod)

#触发Packet_In事件时调用_packet_in_handler函数
@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]
   
   #忽略LLDP类型
    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)

    # 了解mac地址以避免下次泛滥。
    self.mac_to_port[dpid][src] = in_port
     # 查看是否已学习该目的mac地址
    if dst in self.mac_to_port[dpid]:
        out_port = self.mac_to_port[dpid][dst]
    else:   # 否则进行洪泛
        out_port = ofproto.OFPP_FLOOD

    actions = [parser.OFPActionOutput(out_port)]

    # 安装一个流以避免下次出现数据包_
    if out_port != ofproto.OFPP_FLOOD:
        match = parser.OFPMatch(in_port=in_port, eth_dst=dst, eth_src=src)
        # 验证是否有有效的缓冲区id，如果是，则避免同时发送这两个id
        # 流量模块和数据包输出
        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)
    datapath.send_msg(out)  #发送流表

a) 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

b) simple_switch和simple_switch_13在dpid的输出上有何不同
可见在simple_switch_13中，会在前端加上0以填充至16位，simple_switch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？
实现了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？
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？
switch_features_handler下发流表的优先级相对较高

第三部分：反思与总结

标签：定义,datapath,ofproto,switch,实验,msg,软件,ryu,port
来源： https://www.cnblogs.com/fzux/p/15417595.html