实验7：基于REST API的SDN北向应用实践

(一)基本要求

1.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。

点击查看代码

def http_detele(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_detele(url)
    print(resp.content)

(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。

点击查看代码

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

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

点击查看代码

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/operational/opendaylight-inventory:nodes/node/openflow:1/flow-node-inventory:table/0/opendaylight-flow-table-statistics:flow-table-statistics'
    with open('test.json') as f:
        jstr = f.read()
    resp = http_get(url)

2.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。

点击查看代码

def http_post(url, js):
    headers = {'Content-Type': 'application/json'}
    resp = requests.post(url, jstr, headers=headers)
    print(resp)


if __name__ == '__main__':
    url = 'http://localhost:8080/stats/flowentry/add'
    with open('test.json') as f:
        jstr = f.read()
    http_post(url, jstr)

{
  "dpid": 1,
  "match": {
    "in-port": "1",
    "dl_dst": "00:00:00:00:00:03"
  },
  "priority": 65535,
  "hard_timeout": 20,
  "cookie": "2",
  "table_id": 0,
  "actions": []
}

（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。

点击查看代码

curl -X POST -d '{
  "dpid": 1,
  "match": {
    "in_port": 1
  },
  "actions": [
    {
      "type": "PUSH_VLAN",
      "ethertype": 33024
    },
    {
      "type": "SET_FIELD",
      "field": "vlan_vid",
      "value": 4096
    },
    {
      "type":"OUTPUT",
      "port": 3
    }
    ],
    "priority":5
}' http://localhost:8080/stats/flowentry/add

curl -X POST -d '
{
  "dpid": 1,
  "priority":5,
  "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,
  "match": {
    "vlan_vid": 0
  },
  "actions": [
    {
      "type": "POP_VLAN",
      "ethertype": 33024
    },
    {
      "type":"OUTPUT",
      "port": 1
    }
    ],
    "priority":5
}
' http://localhost:8080/stats/flowentry/add

curl -X POST -d'
{
  "dpid": 1,
  "match": {
    "vlan_vid": 1
  },
  "actions": [
    {
      "type": "POP_VLAN",
      "ethertype": 33024
    },
    {
      "type":"OUTPUT",
      "port": 2
    }
    ],
    "priority":5
}
' http://localhost:8080/stats/flowentry/add
curl -X POST -d '{
  "dpid": 2,
  "match": {
    "in_port": 1
  },
  "actions": [
    {
      "type": "PUSH_VLAN",
      "ethertype": 33024
    },
    {
      "type": "SET_FIELD",
      "field": "vlan_vid",
      "value": 4096
    },
    {
      "type":"OUTPUT",
      "port": 3
    }
    ],
    "priority":5
}' http://localhost:8080/stats/flowentry/add

curl -X POST -d '
{
  "dpid": 2,
  "match": {
    "in_port": 2
  },
  "actions": [
    {
      "type": "PUSH_VLAN",
      "ethertype": 33024
    },
    {
      "type": "SET_FIELD",
      "field": "vlan_vid",
      "value": 4097
    },
    {
      "type":"OUTPUT",
      "port": 3
    }
    ],
    "priority":5
}' http://localhost:8080/stats/flowentry/add

curl -X POST -d '
{
  "dpid": 2,
  "match": {
    "vlan_vid": 0
  },
  "actions": [
    {
      "type": "POP_VLAN",
      "ethertype": 33024
    },
    {
      "type":"OUTPUT",
      "port": 1
    }
    ],
    "priority":5
}
' http://localhost:8080/stats/flowentry/add

curl -X POST -d'
{
  "dpid": 2,
  "match": {
    "vlan_vid": 1
  },
  "actions": [
    {
      "type": "POP_VLAN",
      "ethertype": 33024
    },
    {
      "type":"OUTPUT",
      "port": 2
    }
    ],
    "priority":5
}' http://localhost:8080/stats/flowentry/add

（三）实验报告

本次实验难度适中，实验期间遇到的第一个问题是运行上一次实验创建的 L2Switch.py 出现错误，报错“AttributeError: module 'ryu.ofproto.ofproto_v1_0' has no attribute 'OFPET_EXPERIMENTER'
”，未找到最终原因。改用安装 Ryu 时自带的 simple_switch_13.py，成功启动。

第二个问题是启动 simple_switch_13.py 时没有一起运行 ofctl_rest.py 开启控制器的北向接口，导致下发流表失败。

通过这次实验学习了使用 python 向指定 url 发送请求来调用 REST API，了解了相关 API 的使用。