实验六：开源控制器实践——RYU
任务一
完成Ryu控制器的安装。
任务二
搭建下图所示SDN拓扑，协议使用Open Flow 1.0，并连接Ryu控制器。
任务三
通过Ryu的图形界面查看网络拓扑。
任务四
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。
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h1 ping h2
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h1 ping h3
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分析和POX的Hub模块有何不同
此应用程序使用OFPP_FLOOD标志表示应在所有端口发送数据包。pox的hub也是对所以端口发送数据包。
只是集线器hub跟switch所基于转发的形式有所不同而已
进阶任务
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：
a) 代码当中的mac_to_port的作用是什么？
b) simple_switch和simple_switch_13在dpid的输出上有何不同？
c) 相比simple_switch，simple_switch_13增加的switch_feature_handler实现了什么功能？
d) simple_switch_13是如何实现流规则下发的？
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？
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代码注释
# 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
# 继承ryu.base.app_manager.RyuApp
class SimpleSwitch13(app_manager.RyuApp):
OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION] # 版本号为1.3
def __init__(self, *args, **kwargs): # 初始化类
super(SimpleSwitch13, self).__init__(*args, **kwargs)
self.mac_to_port = {} # 初始化mac_to_port数组
@set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER)
def switch_features_handler(self, ev): # 安装无目标的流表条目
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
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)
@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 # 用packet library分析收到的数据包
dpid = format(datapath.id, "d").zfill(16) # 获得Datapath ID以便于识别OpenFlow交换机
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 # 记录mac地址以避免下次的消息范洪
if dst in self.mac_to_port[dpid]: # 如果目标Mac地址已经被学习了，决定哪个从哪个端口发送数据包。否则范洪
out_port = self.mac_to_port[dpid][dst]
else:
out_port = ofproto.OFPP_FLOOD
actions = [parser.OFPActionOutput(out_port)] # 构造action表
# 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
# 构造一个pack_out消息然后发送
out = parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id,
in_port=in_port, actions=actions, data=data)
datapath.send_msg(out)
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问题
a) 代码当中的mac_to_port的作用是什么？
- 学习mac地址，保存mac地址到交换机端口的映射，就不使用洪泛转发
b) simple_switch和simple_switch_13在dpid的输出上有何不同？
- simple_switch_13对dpid进行了格式化，并填充为16位数字
c) 相比simple_switch，simple_switch_13增加的switch_feature_handler实现了什么功能？
- 安装无目标的流表条目
d) simple_switch_13是如何实现流规则下发的？
- 收到包后进行学习，如果mac地址存在则进行转发，不存在就使用洪泛转发
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发送的priority=0，_packet_in_handler发送的流表的priority设置为1
总结
- ryu下载时一直请求超时，问了同学他们就一直试，试到可以为止；
- 在写L2Switch.py文件的时候，用vim一直写不进去，后面在别的地方写完用代码移进去，但是打不开，报错模块找不到，一开始以为是python版本的问题，后面发现也不是，一直没找到方法 ，换了个虚拟机重新安装一遍就好了，感觉是在安装的时候哪一步没搞好导致的，还没找到具体原因；
- 进阶任务还是有难度，看得头很晕，找资料、参考已完成同学的博客才勉强完成。
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