暑期实训SDN--负载均衡

暑期实训的第一个SDN项目。

0x01 实验要求：

在生活中遇到这样的场景，对Server的性能要求很高；但无论再好的硬件，也有力不足的时候，特别是还可能遇到宕机的时候:~~（不得不吐槽一下某语言等级考试报名网站凸(艹皿艹) ）~~

如上图的服务器部署，就能有效减少上述情况；所以负载均衡在现实生活中很有必要。

0x02 网络拓扑

网络拓扑很简单，就如下图所示。由控制器下发流表，实现h3、h4分担h2服务的压力。

提供网络拓扑构建的源码：基于Mininet的拓扑构建

from mininet.net import Mininet
from mininet.cli import CLI
from mininet.node import RemoteController,Controller
from mininet.log import info
import sys

if len(sys.argv) == 1:
    controller_ip = '127.0.0.1'
else:
    controller_ip = sys.argv[1]

# net = Mininet(controller=Controller)
# controller=net.addController(ip='127.0.0.1',port=6653)
net = Mininet(controller=RemoteController)
odl_controller=net.addController('ODL_controller',
                                controller=RemoteController,
                                ip=controller_ip,port=6633)
print("*** Add Switch\n")
s1=net.addSwitch('s1')
print("*** Add Hosts\n")
h1=net.addHost('h1')
print("*** Addd Servers\n")
server1 = net.addHost('server1')
server2 = net.addHost('server2')
server3 = net.addHost('server3')

net.addLink(s1,h1)
net.addLink(s1,server1)
net.addLink(s1,server2)
net.addLink(s1,server3)


h1.setIP('10.0.0.1',24)
h1.setMAC('00:00:00:00:00:01')

server1.setIP('10.0.0.2',24)
server2.setIP('10.0.0.3',24)
server3.setIP('10.0.0.4',24)
server1.setMAC('00:00:00:00:00:02')
server2.setMAC('00:00:00:00:00:03')
server3.setMAC('00:00:00:00:00:04')

net.start()

CLI(net)

提前运行ODL控制器，命令行再运行：# python mytopo.py；回到ODL控制器查看拓扑如下：

0x03 流表下发：

我们是通过编写python脚本实现流表的下发，以达到修改数据包信息的目的，从而实现转发至server2(h3)和sever3(h4)的目的。关键部分就是 macth_set和action的编写。

流表的脚本如下：

import base64
import json
import httplib
import time
import math
from threading import Timer
import random
import sys

def pre_put(url, body):
    try:
        auth = base64.b64encode('admin:admin'.encode())
        headers = {"Authorization": "Basic " + auth, "Content-Type": "application/json"}
        conn = httplib.HTTPConnection('127.0.0.1:8181', timeout=3)    
        conn.request("PUT", url, body, headers)
        response = conn.getresponse()
        
        if response.status in [200,201]:
            print 'add success'
        else:
            print 'add failure'
   
    except Exception as e:
        import traceback
        traceback.print_exc()

def add_flow(port,ip,mac):
    
    switch_id = 'openflow:1'
    url = "/restconf/config/opendaylight-inventory:nodes/node/" + switch_id + "/flow-node-inventory:table/0/flow/5"
    flow_set = {
    'id': '5',
    'flow-name': '5',
    'table_id': 0,
    # 'hard-timeout':'5'
    'priority': "200"
    }

    #match
    # match_set = {'in-port':switch_id+':23'}
    ethernet_match ={'ethernet-type':{'type':"2048"}}
    match_set = {
        'ethernet-match':ethernet_match,
        'ipv4-destination':'10.0.0.2/32'
    }

    #action
    # action_set = {
    # 'order': "0",
    # 'output-action':{"output-node-connector": switch_id +':' + port }
    # }
    action_mod_mac={
        'order':"0",
        'set-dl-dst-action':{'address':mac}
    }
    action_mod_ip = {
        'order':"1",
        'set-nw-dst-action':{'ipv4-address':ip}
    }
    
    action_set = {
        'order':"2",
        'output-action':{"output-node-connector":switch_id+':'+port}
    }


    instruc_set = {
        "instruction": [{
            "order": "0",
            "apply-actions": {
                "action": [action_mod_mac,action_mod_ip,action_set]
            }
        }]
    }

    flow_set['match'] = match_set
    flow_set['instructions'] = instruc_set
    body = json.dumps({"flow":flow_set})
    pre_put(url, body)



def flow_change(s1_node_id):
    port_flag = random.randint(0,2)
    # print(port_flag)
    if port_flag == 0:
        port = '2'
        ip = '10.0.0.2/32'
        mac = '00:00:00:00:00:02'
    elif port_flag == 1:
        port = '3'
        ip = '10.0.0.3/32'
        mac = '00:00:00:00:00:03'
    elif port_flag == 2:
        port = '4'
        ip = '10.0.0.4/32'
        mac = '00:00:00:00:00:04'

    add_flow(port,ip,mac)

    print("backend server is:server%s"%ip)


if __name__=="__main__":
    while True:
        flow_change('1')
        time.sleep(5)