實驗7：基於REST API的SDN北向應用實踐

實驗步驟

一、搭建拓撲，連接 OpenDaylight，下發流表

• 編寫Python程序，調用OpenDaylight的北向接口下發指令刪除s1上的流表數據

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

if __name__ == "__main__":
    url='http://127.0.0.1:8181/restconf/config/opendaylight-inventory:nodes/node/openflow:1/'
    resp = http_delete(url)
    print (resp.content)

• 編寫Python程序，調用OpenDaylight的北向接口下發硬超時流表，實現拓撲內主機h1和h3網絡中斷20s

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

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('h_timeout.json') as f:
        jstr = f.read()
    resp = http_put(url,jstr)
    print (resp.content)

{
    "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"
        }
    ]
}

• 編寫Python程序，調用OpenDaylight的北向接口獲取s1上活動的流表數

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

if __name__ == "__main__":
    url='http://127.0.0.1:8181/restconf/config/opendaylight-inventory:nodes/node/openflow:1/flow-node-inventory:table/0'
    resp = http_get(url)
    res = json.loads(resp.text)
    # print(resp.text)
    print(len(res['flow-node-inventory:table'][0]['flow']))

二、搭建拓撲，連接 Ryu，下發流表

• 編寫Python程序，調用Ryu的北向接口，實現上述OpenDaylight實驗拓撲上相同的硬超時流表下發

#!/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('ryu_htimeout.json') as f:
        jstr = f.read()
    resp = http_post(url,jstr)
    print (resp.content)

{
    "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
        }
    ]
 }

個人總結

• 本次實驗難度適中，實驗期間遇到的第一個問題是運行上一次實驗創建的 L2Switch.py 出現錯誤，報錯“AttributeError: module 'ryu.ofproto.ofproto_v1_0' has no attribute 'OFPET_EXPERIMENTER'
  ”，未找到最終原因。改用安裝 Ryu 時自帶的 simple_switch_13.py，成功啟動。

• 第二個問題是啟動 simple_switch_13.py 時沒有一起運行 ofctl_rest.py 開啟控制器的北向接口，導致下發流表失敗。

• 通過這次實驗學習了使用 python 向指定 url 發送請求來調用 REST API，了解了相關 API 的使用。