实验7：基于REST API的SDN北向应用实践

一、实验目的

能够编写程序调用OpenDaylight REST API实现特定网络功能；
能够编写程序调用Ryu REST API实现特定网络功能。

二、实验环境

下载虚拟机软件Oracle VisualBox或VMware；
在虚拟机中安装Ubuntu 20.04 Desktop amd64，并完整安装Mininet、OpenDaylight（Carbon版本）、Postman和Ryu；

三、实验要求

（一）基本要求

OpenDaylight

（1）利用Mininet平台搭建下图所示网络拓扑，并连接OpenDaylight；

（2）编写Python程序，调用OpenDaylight的北向接口下发指令删除s1上的流表数据。

delete.py

#!/usr/bin/python
import requests
from requests.auth import HTTPBasicAuth

if __name__ == "__main__":
    url = 'http://127.0.0.1:8181/restconf/config/opendaylight-inventory:nodes/node/openflow:1/'
    headers = {'Content-Type': 'application/json'}
    res = requests.delete(url, headers=headers, auth=HTTPBasicAuth('admin', 'admin'))
    print (res.content)

结果

（3）编写Python程序，调用OpenDaylight的北向接口下发硬超时流表，实现拓扑内主机h1和h3网络中断20s。

put.py

#!/usr/bin/python
import requests
from requests.auth import HTTPBasicAuth

if __name__ == "__main__":
    url = 'http://127.0.0.1:8181/restconf/config/opendaylight-inventory:nodes/node/openflow:1/flow-node-inventory:table/0/flow/1'
    with open("./flowtable.json") as f:
        jstr = f.read()
    headers = {'Content-Type': 'application/json'}
    res = requests.put(url, jstr, headers=headers, auth=HTTPBasicAuth('admin', 'admin'))
    print (res.content)

flowtable.json

{
  "flow": [
    {
      "id": "1",
      "match": {
        "in-port": "1",
        "ethernet-match": {
          "ethernet-type": {
            "type": "0x0800"
          }
        },
        "ipv4-destination": "10.0.0.3/32"
      },
      "instructions": {
        "instruction": [
          {
            "order": "0",
            "apply-actions": {
              "action": [
                {
                  "order": "0",
                  "drop-action": {}
                }
              ]
            }
          }
        ]
      },
      "flow-name": "flow1",
      "priority": "65535",
      "hard-timeout": "20",
      "cookie": "2",
      "table_id": "0"
    }
  ]
}

结果

（4）编写Python程序，调用OpenDaylight的北向接口获取s1上活动的流表数。

get.py

#!/usr/bin/python
import requests
from requests.auth import HTTPBasicAuth

if __name__ == "__main__":
    url = 'http://127.0.0.1:8181/restconf/operational/opendaylight-inventory:nodes/node/openflow:1/flow-node-inventory:table/0/opendaylight-flow-table-statistics:flow-table-statistics'
    headers = {'Content-Type': 'application/json'}
    res = requests.get(url,headers=headers, auth=HTTPBasicAuth('admin', 'admin'))
    print (res.content)

结果

Ryu

（1）编写Python程序，调用Ryu的北向接口，实现上述OpenDaylight实验拓扑上相同的硬超时流表下发。

put1.py

#!/usr/bin/python
import requests
from requests.auth import HTTPBasicAuth
def http_post(url,jstr):
    url= url
    headers = {'Content-Type':'application/json'}
    resp = requests.post(url,jstr,headers=headers)
    return resp

if __name__ == "__main__":
    url='http://127.0.0.1:8080/stats/flowentry/add'
    with open('flowtable1.json') as f:
        jstr = f.read()
    resp = http_post(url,jstr)
    print (resp.content)

flowtable1.json

{
    "dpid": 1,
    "cookie": 1,
    "cookie_mask": 1,
    "table_id": 0,
    "hard_timeout": 20,
    "priority": 65535,
    "flags": 1,
    "match":{
        "in_port":1
    },
    "actions":[
        {
            "type":"OUTPUT",
            "port": 2
        }
    ]
}

结果

（2）利用Mininet平台搭建下图所示网络拓扑，要求支持OpenFlow 1.3协议，主机名、交换机名以及端口对应正确。拓扑生成后需连接Ryu，且Ryu应能够提供REST API服务。

（3）整理一个Shell脚本，参考Ryu REST API的文档，利用curl命令，实现和实验2相同的VLAN。

VLAN_ID	Hosts
0	h1 h3
1	h2 h4

shell脚本

curl -X POST -d '{
    "dpid": 1,
    "priority": 1,
    "match":{
        "in_port": 1
    },
    "actions":[
        {
            "type": "PUSH_VLAN",     
            "ethertype": 33024       
        },
        {
            "type": "SET_FIELD",
            "field": "vlan_vid",    
            "value": 4096            
        },
        {
            "type": "OUTPUT",
            "port": 3
        }
    ]
 }' http://localhost:8080/stats/flowentry/add

 curl -X POST -d '{
    "dpid": 1,
    "priority": 1,
    "match":{
        "in_port": 2
    },
    "actions":[
        {
            "type": "PUSH_VLAN",    
            "ethertype": 33024      
        },
        {
            "type": "SET_FIELD",
            "field": "vlan_vid",     
            "value": 4097           
        },
        {
            "type": "OUTPUT",
            "port": 3
        }
    ]
 }' http://localhost:8080/stats/flowentry/add

 curl -X POST -d '{
    "dpid": 1,
    "priority": 1,
    "match":{
        "vlan_vid": 0
    },
    "actions":[
        {
            "type": "POP_VLAN",    
            "ethertype": 33024       
        },
        {
            "type": "OUTPUT",
            "port": 1
        }
    ]
 }' http://localhost:8080/stats/flowentry/add

 curl -X POST -d '{
    "dpid": 1,
    "priority": 1,
    "match":{
        "vlan_vid": 1
    },
    "actions":[
        {
            "type": "POP_VLAN",    
            "ethertype": 33024      
        },
        {
            "type": "OUTPUT",
            "port": 2
        }
    ]
 }' http://localhost:8080/stats/flowentry/add

 curl -X POST -d '{
    "dpid": 2,
    "priority": 1,
    "match":{
        "in_port": 1
    },
    "actions":[
        {
            "type": "PUSH_VLAN",    
            "ethertype": 33024      
        },
        {
            "type": "SET_FIELD",
            "field": "vlan_vid",    
            "value": 4096          
        },
        {
            "type": "OUTPUT",
            "port": 3
        }
    ]
 }' http://localhost:8080/stats/flowentry/add

 curl -X POST -d '{
    "dpid": 2,
    "priority": 1,
    "match":{
        "in_port": 2
    },
    "actions":[
        {
            "type": "PUSH_VLAN",    
            "ethertype": 33024      
        },
        {
            "type": "SET_FIELD",
            "field": "vlan_vid",   
            "value": 4097           
        },
        {
            "type": "OUTPUT",
            "port": 3
        }
    ]
 }' http://localhost:8080/stats/flowentry/add

 curl -X POST -d '{
    "dpid": 2,
    "priority": 1,
    "match":{
        "vlan_vid": 0
    },
    "actions":[
        {
            "type": "POP_VLAN",    
            "ethertype": 33024      
        },
        {
            "type": "OUTPUT",
            "port": 1
        }
    ]
 }' http://localhost:8080/stats/flowentry/add

 curl -X POST -d '{
    "dpid": 2,
    "priority": 1,
    "match":{
        "vlan_vid": 1
    },
    "actions":[
        {
            "type": "POP_VLAN",    
            "ethertype": 33024      
        },
        {
            "type": "OUTPUT",
            "port": 2
        }
    ]
 }' http://localhost:8080/stats/flowentry/add

结果

四、个人总结

实验难度：有点难了啊
实验困难及解决办法：

忘记了一定要在创拓扑之前开控制器的前车之鉴，导致拓扑又无法ping通。清除关闭拓扑，先启动 ODL 或 RYU 后再创建执行拓扑，成功解决。以及ryu控制器使用时，命令行搭建拓扑用OpenFlow1.0协议的拓扑无法pingall，需要改成OpenFlow1.3协议。
不知道发生什么错误导致 mininet 可视化拓扑暂时无法使用，改用 python 创建实验所需要的拓扑，借鉴了同学的代码（如下图），使用命令sudo mn --custom topo.py --topo mytopo --mac --controller=remote,ip=127.0.0.1,port=6633 --switch ovsk,protocols=OpenFlow13运行。
使用 Shell 脚本即sh shell.sh后，再pingall发现并未发生改变，仍全通。参考同学做法，首先在命令行先执行curl -X DELETE http://localhost:8080/stats/flowentry/clear/1 curl -X DELETE http://localhost:8080/stats/flowentry/clear/2删除流表，再使用 Shell 脚本再pingall，成功达成目标。
使用 Shell 脚本的时候，出现下图提示，发现并未安装 crul，于是在命令行执行sudo apt-get install curl

个人感想：学习到了使用程序调用两种控制器接口的具体方法，感觉对控制器了解程度更深了。整体实验给我的大体感受就是，一定要学习如何编写 Python 程序调用接口啊！个人而言，这个实验里编写代码就是个非常困难且耗时间的事情，要做到完全理解语句和做到实验要求的功能，是需要去仔细琢磨的。而即使是在有参考的情况下照猫画虎、按部就班地实验，也还是会遇到各种各样诡异的事阻碍实验，“活用搜索引擎”可能要变成我的人生信条了。

posted @ 2021-10-25 17:33 AnEweLamb 阅读(100) 评论(0) 编辑收藏举报

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