Mininet 系列实验（四）

• 实验内容

本次实验拓扑图：



在该环境下，h0 向 h1 发送数据包，由于在 mininet 脚本中设置了连接损耗率，在传输过程中会丢失一些包，本次实验的目的是展示如何通过控制器计算路径损耗速率（h0-s0-s1-h1）。这里假设控制器预先知道网络拓扑，所以没有显示发现网络的代码以及其他相关代码。控制器将向 s0 和 s1 发送 flow_stats_request，当控制器接收到来自 s0 的 response 时，将特定流的数据包数保存在 input_pkts 中，当控制器接收到来自 s1 的 response 时，将接收到特定流的数据包数保存在 output_pkts 中，差值就是丢失的数据包数量。

• 参考

基于Mininet测量路径的损耗率

• 实验环境

虚拟机: Oracle VM VirtualBox Ubuntu16.04LTS

本次实验需要安装 POX、支持 OpenFlow1.3 协议的 Mininet

安装 POX 的命令：

# git clone http://github.com/noxrepo/pox

如果 Mininet 不支持OpenFlow1.3 我能想到方法就只有卸载重装。具体方法见：Mininet 系列实验（三）

• 实验步骤

1. 编写 Mininet 脚本

# touch mymininet.py
# vim mymininet.py

然后编辑文件 mymininet.py，内容如下：

#!/usr/bin/python

from mininet.net import Mininet
from mininet.node import Node
from mininet.link import TCLink
from mininet.log import  setLogLevel, info
from threading import Timer
from mininet.util import quietRun
from time import sleep

def myNet(cname='controller', cargs='-v ptcp:'):
    "Create network from scratch using Open vSwitch."
    info( "*** Creating nodes\n" )
    controller = Node( 'c0', inNamespace=False )
    switch = Node( 's0', inNamespace=False )
    switch1 = Node( 's1', inNamespace=False )
    h0 = Node( 'h0' )
    h1 = Node( 'h1' )

    info( "*** Creating links\n" )
    linkopts0=dict(bw=100, delay='1ms', loss=0)
    linkopts1=dict(bw=100, delay='1ms', loss=10)
    link0=TCLink( h0, switch, **linkopts0)
    link1 = TCLink( switch, switch1, **linkopts1)
    link2 = TCLink( h1, switch1, **linkopts0)
    #print link0.intf1, link0.intf2
    link0.intf2.setMAC("0:0:0:0:0:1")
    link1.intf1.setMAC("0:0:0:0:0:2")
    link1.intf2.setMAC("0:1:0:0:0:1")
    link2.intf2.setMAC("0:1:0:0:0:2")

    info( "*** Configuring hosts\n" )
    h0.setIP( '192.168.123.1/24' )
    h1.setIP( '192.168.123.2/24' )

    info( "*** Starting network using Open vSwitch\n" )
    switch.cmd( 'ovs-vsctl del-br dp0' )
    switch.cmd( 'ovs-vsctl add-br dp0' )
    switch1.cmd( 'ovs-vsctl del-br dp1' )
    switch1.cmd( 'ovs-vsctl add-br dp1' )

    controller.cmd( cname + ' ' + cargs + '&' )
    for intf in switch.intfs.values():
        print intf
        print switch.cmd( 'ovs-vsctl add-port dp0 %s' % intf )
    for intf in switch1.intfs.values():
        print intf
        print switch1.cmd( 'ovs-vsctl add-port dp1 %s' % intf )

    # Note: controller and switch are in root namespace, and we
    # can connect via loopback interface
    switch.cmd( 'ovs-vsctl set-controller dp0 tcp:10.0.0.13:6633' )
    //这里改为自己的 IP 地址，例如我的是 10.0.2.15，端口号6633不变
    switch1.cmd( 'ovs-vsctl set-controller dp1 tcp:10.0.0.13:6633')
    //这里改为自己的 IP 地址，例如我的是 10.0.2.15，端口号6633不变
    info( '*** Waiting for switch to connect to controller' )
    while 'is_connected' not in quietRun( 'ovs-vsctl show' ):
        sleep( 1 )
        info( '.' )
    info( '\n' )

    #info( "*** Running test\n" )
    h0.cmdPrint( 'ping -Q 0x64 -c 20 ' + h1.IP() )

    sleep( 1 )
    info( "*** Stopping network\n" )
    controller.cmd( 'kill %' + cname )
    switch.cmd( 'ovs-vsctl del-br dp0' )
    switch.deleteIntfs()
    switch1.cmd( 'ovs-vsctl del-br dp1' )
    switch1.deleteIntfs()
    info( '\n' )

if __name__ == '__main__':
    setLogLevel( 'info' )
    info( '*** Scratch network demo (kernel datapath)\n' )
    Mininet.init()
    myNet()

2. 编写 POX 脚本

# cd pox
# touch flow_stats.py
# vim flow_stats.py

同样编辑文件 flow_stats.py，内容如下：

#!/usr/bin/python
# Copyright 2012 William Yu
# wyu@ateneo.edu
#
# This file is part of POX.
#
# POX is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# POX is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with POX. If not, see <http://www.gnu.org/licenses/>.
#

"""
This is a demonstration file created to show how to obtain flow
and port statistics from OpenFlow 1.0-enabled switches. The flow
statistics handler contains a summary of web-only traffic.
"""

# standard includes
from pox.core import core
from pox.lib.util import dpidToStr
import pox.openflow.libopenflow_01 as of
from pox.lib.addresses import IPAddr, EthAddr

# include as part of the betta branch
from pox.openflow.of_json import *
from pox.lib.recoco import Timer
import time

log = core.getLogger()

src_dpid = 0
dst_dpid = 0
input_pkts = 0
output_pkts = 0

def getTheTime():  #fuction to create a timestamp
  flock = time.localtime()
  then = "[%s-%s-%s" %(str(flock.tm_year),str(flock.tm_mon),str(flock.tm_mday))

  if int(flock.tm_hour)<10:
    hrs = "0%s" % (str(flock.tm_hour))
  else:
    hrs = str(flock.tm_hour)
  if int(flock.tm_min)<10:
    mins = "0%s" % (str(flock.tm_min))
  else:
    mins = str(flock.tm_min)
  if int(flock.tm_sec)<10:
    secs = "0%s" % (str(flock.tm_sec))
  else:
    secs = str(flock.tm_sec)
  then +="]%s.%s.%s" % (hrs,mins,secs)
  return then

# handler for timer function that sends the requests to all the
# switches connected to the controller.
def _timer_func ():
  for connection in core.openflow._connections.values():
    connection.send(of.ofp_stats_request(body=of.ofp_flow_stats_request()))
    connection.send(of.ofp_stats_request(body=of.ofp_port_stats_request()))
  log.debug("Sent %i flow/port stats request(s)", len(core.openflow._connections))

# handler to display flow statistics received in JSON format
# structure of event.stats is defined by ofp_flow_stats()
def _handle_flowstats_received (event):
   #stats = flow_stats_to_list(event.stats)
   #log.debug("FlowStatsReceived from %s: %s", dpidToStr(event.connection.dpid), stats)
   global src_dpid, dst_dpid, input_pkts, output_pkts
   #print "src_dpid=", dpidToStr(src_dpid), "dst_dpid=", dpidToStr(dst_dpid)
   for f in event.stats:
     if f.match.dl_type==0x0800 and f.match.nw_dst==IPAddr("192.168.123.2") and f.match.nw_tos==0x64 and event.connection.dpid==src_dpid:
       #print "input: ", f.byte_count, f.packet_count
       input_pkts = f.packet_count
     if f.match.dl_type==0x0800 and f.match.nw_dst==IPAddr("192.168.123.2") and f.match.nw_tos==0x64 and event.connection.dpid==dst_dpid:
       #print "output: ", f.byte_count, f.packet_count
       output_pkts = f.packet_count
       if input_pkts !=0:
         print getTheTime(), "Path Loss Rate =", (input_pkts-output_pkts)*1.0/input_pkts*100, "%"

# handler to display port statistics received in JSON format
def _handle_portstats_received (event):
   #print "\n<<<STATS-REPLY: Return PORT stats for Switch", event.connection.dpid,"at ",getTheTime()
   #for f in event.stats:
      #if int(f.port_no)<65534:
        #print "   PortNo:", f.port_no, " Fwd's Pkts:", f.tx_packets, " Fwd's Bytes:", f.tx_bytes, " Rc'd Pkts:", f.rx_packets, " Rc's Bytes:", f.rx_bytes
        #print "   PortNo:", f.port_no,  " TxDrop:", f.tx_dropped, " RxDrop:", f.rx_dropped, " TxErr:", f.tx_errors, " RxErr:", f.rx_errors, " CRC:", f.rx_crc_err, " Coll:", f.collisions
  stats = flow_stats_to_list(event.stats)
  log.debug("PortStatsReceived from %s: %s", dpidToStr(event.connection.dpid), stats)

def _handle_ConnectionUp (event):
  global src_dpid, dst_dpid
  print "ConnectionUp: ", dpidToStr(event.connection.dpid)
  for m in event.connection.features.ports:
    if m.name == "s0-eth0":
      src_dpid = event.connection.dpid
    elif m.name == "s1-eth0":
      dst_dpid = event.connection.dpid

  msg = of.ofp_flow_mod()
  msg.priority =1
  msg.idle_timeout = 0
  msg.match.in_port =1
  msg.actions.append(of.ofp_action_output(port = of.OFPP_ALL))
  event.connection.send(msg)

  msg = of.ofp_flow_mod()
  msg.priority =1
  msg.idle_timeout = 0
  msg.match.in_port =2
  msg.actions.append(of.ofp_action_output(port = of.OFPP_ALL))
  event.connection.send(msg)

  msg = of.ofp_flow_mod()
  msg.priority =10
  msg.idle_timeout = 0
  msg.hard_timeout = 0
  msg.match.dl_type = 0x0800
  msg.match.nw_tos = 0x64
  msg.match.in_port=1
  msg.match.nw_dst = "192.168.123.2"
  msg.actions.append(of.ofp_action_output(port = 2))
  event.connection.send(msg)

  msg = of.ofp_flow_mod()
  msg.priority =10
  msg.idle_timeout = 0
  msg.hard_timeout = 0
  msg.match.dl_type = 0x0800
  msg.match.nw_tos = 0x64
  msg.match.nw_dst = "192.168.123.1"
  msg.actions.append(of.ofp_action_output(port = 1))
  event.connection.send(msg)

# main functiont to launch the module
def launch ():
  # attach handsers to listners
  core.openflow.addListenerByName("FlowStatsReceived",
    _handle_flowstats_received)
  core.openflow.addListenerByName("PortStatsReceived",
    _handle_portstats_received)
  core.openflow.addListenerByName("ConnectionUp", _handle_ConnectionUp)

  # timer set to execute every five seconds
  Timer(1, _timer_func, recurring=True)

3. 运行 flow_stats.py

# ./pox.py flow_stats

4. 运行 myminiet.py

在打开一个终端，执行以下命令

# chmod +x mymininet.py
# ./mymininet.py

或者

# python mymininet.py

结果发现，交换机无法与 POX 控制器连接上。结果十分不理想。

• 总结

1. 实验过程中遇到的问题

• 最大的问题就是 Python 没有掌握，基本看不懂脚本。
• 对 POX 没有了解，不知道用法也不知道如何配置。
• 没有达到预期的实验结果，分析之后，个人认为主要还是上面两个问题没有解决，这个坑就先留在这里，等学有所成再回过头来解决