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

1.编写Python程序，调用OpenDaylight的北向接口实现以下功能

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

• 连接OpenDaylight

./distribution-karaf-0.6.4-Carbon/bin/karaf

• 创建拓扑

sudo mn --topo=single,3 --controller=remote,ip=127.0.0.1,port=6633 --switch ovsk,protocols=OpenFlow13

（2） 下发指令删除s1上的流表数据

• 编写Python程序,代码delete.py如下

#!/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)

• 运行delete.pysudo python delete.py

• 查看s1上的流表数据

（3） 下发硬超时流表，实现拓扑内主机h1和h3网络中断20s

• 编写Python程序，代码hardtime.py

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("./hardtime.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)

• 代码hardtime.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"
    }
  ]
}

• 运行hardtime.py结果如下

（4） 获取s1上活动的流表数

• 编写Python程序，代码getflow.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)

• 运行getflow.pysudo python getflow.py

2.编写Python程序，调用Ryu的北向接口实现以下功能

（1） 实现上述OpenDaylight实验拓扑上相同的硬超时流表下发。

• 关闭ODL控制器，关闭上次的拓扑并清除拓扑后 sudo mn -c

• 使用命令打开Ryu控制器ryu-manager ryu.app.simple_switch_13 ryu.app.ofctl_rest

• 重新创建拓扑sudo mn --topo=single,3 --mac --controller=remote,ip=127.0.0.1,port=6633 --switch ovsk,protocols=OpenFlow13

• 代码Ryuhardtime.py

#!/usr/bin/python
import requests

if __name__ == "__main__":
    url = 'http://127.0.0.1:8080/stats/flowentry/add'
    with open("./Ryuhardtime.json") as f:
        jstr = f.read()
    headers = {'Content-Type': 'application/json'}
    res = requests.post(url, jstr, headers=headers)
    print (res.content)

• 代码Ryuhardtime.json

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

    ]
 }

• 运行Ryuhardtime.py sudo python Ryuhardtime.py

（2） 参考Ryu REST API的文档，基于VLAN实验的网络拓扑，编程实现相同的VLAN配置。

• 关闭ODL控制器，关闭上次的拓扑并清除拓扑后 sudo mn -c

• 使用命令打开Ryu控制器.ryu-manager ryu.app.simple_switch_13 ryu.app.ofctl_rest

• 代码topo.py

#topo.py
from mininet.topo import Topo

class MyTopo(Topo):
    def __init__(self):
        # initilaize topology
        Topo.__init__(self)

        self.addSwitch("s1")
        self.addSwitch("s2")

        self.addHost("h1")
        self.addHost("h2")
        self.addHost("h3")
        self.addHost("h4")

        self.addLink("s1", "h1")
        self.addLink("s1", "h2")
        self.addLink("s2", "h3")
        self.addLink("s2", "h4")
        self.addLink("s1", "s2")

topos = {'mytopo': (lambda: MyTopo())}

• 运行topo.py.sudo mn --custom topo.py --topo mytopo --mac --controller=remote,ip=127.0.0.1,port=6633 --switch ovsk,protocols=OpenFlow13

• 删除流表

curl -X DELETE http://localhost:8080/stats/flowentry/clear/1
curl -X DELETE http://localhost:8080/stats/flowentry/clear/2

• 代码Ryuvlan.py

import json

import requests

if __name__ == "__main__":
    url = 'http://127.0.0.1:8080/stats/flowentry/add'
    headers = {'Content-Type': 'application/json'}
    flow1 = {
        "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
            }
        ]
    }
    flow2 = {
        "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
            }
        ]
    }
    flow3 = {
        "dpid": 1,
        "priority": 1,
        "match":{
            "vlan_vid": 0
        },
        "actions":[
            {
                "type": "POP_VLAN",    
                "ethertype": 33024     
            },
            {
                "type": "OUTPUT",
                "port": 1
            }
        ]
    }
    flow4 = {
        "dpid": 1,
        "priority": 1,
        "match": {
            "vlan_vid": 1
        },
        "actions": [
            {
                "type": "POP_VLAN", 
                "ethertype": 33024  
            },
            {
                "type": "OUTPUT",
                "port": 2
            }
        ]
    }
    flow5 = {
        "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
            }
        ]
    }
    flow6 = {
        "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
            }
        ]
    }
    flow7 = {
        "dpid": 2,
        "priority": 1,
        "match": {
            "vlan_vid": 0
        },
        "actions": [
            {
                "type": "POP_VLAN", 
                "ethertype": 33024  
            },
            {
                "type": "OUTPUT",
                "port": 1
            }
        ]
    }
    flow8 = {
        "dpid": 2,
        "priority": 1,
        "match": {
            "vlan_vid": 1
        },
        "actions": [
            {
                "type": "POP_VLAN", 
                "ethertype": 33024  
            },
            {
                "type": "OUTPUT",
                "port": 2
            }
        ]
    }
    res1 = requests.post(url, json.dumps(flow1), headers=headers)
    res2 = requests.post(url, json.dumps(flow2), headers=headers)
    res3 = requests.post(url, json.dumps(flow3), headers=headers)
    res4 = requests.post(url, json.dumps(flow4), headers=headers)
    res5 = requests.post(url, json.dumps(flow5), headers=headers)
    res6 = requests.post(url, json.dumps(flow6), headers=headers)
    res7 = requests.post(url, json.dumps(flow7), headers=headers)
    res8 = requests.post(url, json.dumps(flow8), headers=headers)

• 运行Ryuvlan.py

提示：拓扑生成后需连接Ryu，且Ryu应能够提供REST API服务

（二）进阶要求

OpenDaylight或Ryu任选其一，编程实现查看前序VLAN实验拓扑中所有节点（含交换机、主机）的名称，以及显示每台交换机的所有流表项。

• 代码getnodes.py

import requests
import time
import re


class GetNodes:
    def __init__(self, ip):
        self.ip = ip
        
    def get_switch_id(self):
        url = 'http://' + self.ip + '/stats/switches'
        re_switch_id = requests.get(url=url).json()
        switch_id_hex = []
        for i in re_switch_id:
            switch_id_hex.append(hex(i))

        return switch_id_hex

    def getflow(self):
        url = 'http://' + self.ip + '/stats/flow/%d'
        switch_list = self.get_switch_id()
        ret_flow = []
        for switch in switch_list:
            new_url = format(url % int(switch, 16))
            re_switch_flow = requests.get(url=new_url).json()
            ret_flow.append(re_switch_flow)
        return ret_flow

    def show(self):
        flow_list = self.getflow()
        for flow in flow_list:
            for dpid in flow.keys():
                dp_id = dpid
                switchnum= '{1}'.format(hex(int(dp_id)), int(dp_id))        
                print('s'+switchnum,end = " ")
                switchnum = int(switchnum)
            for list_table in flow.values():
                for table in list_table:          
                    string1 = str(table)
                    if re.search("'dl_vlan': '(.*?)'", string1) is not None:
                       num = re.search("'dl_vlan': '(.*?)'", string1).group(1);
                       if num == '0' and switchnum == 1:
                          print('h1',end = " ")
                       if num == '1' and switchnum == 1:
                          print('h2',end = " ")
                       if num == '0' and switchnum == 2:
                          print('h3',end = " ")
                       if num == '1' and switchnum == 2:
                          print('h4',end = " ")
        print("")
        flow_list = self.getflow()
        for flow in flow_list:
            for dpid in flow.keys():
                dp_id = dpid
                print('switch_name:s{1}'.format(hex(int(dp_id)), int(dp_id)))
            for list_table in flow.values():
                for table in list_table:
                    print(table)
s1 = GetNodes("127.0.0.1:8080")
s1.show()

• 查看前序VLAN实验拓扑中所有节点（含交换机、主机）的名称,查看每台交换机的所有流表项

（三）实验总结

实验中遇到的问题及解决办法

• 做VLAN划分时下发流表后还是全部都能互相ping通。解决方法：应该先把所有流表删除在进行新流表的下发
• 在进行Ryu的（3）操作时，遇到了好多困难，不知道要先删除流表，以及整理好的脚本用sh命令却报错，可Ryu控制器是处于running状态的，后来听同学的直接将其黏贴进命令行使用，并且要先用curl命令删除流表
• 在使用curl命令时，提示command not found。解决办法：sudo apt-get install curl 执行命令就好了

个人感想

• 通过这次实验，进一步学习了用OpenDaylight和Ryu的rest API来实现特定的网络功能，除此之外还进一步学习了python的request库，为接下来做大作业打下了基础。同时在实验中遇到问题查看了相关文档，锻炼了阅读文档的能力。这次实验中是由几个小实验组成的，做完一个做下一个的时候，要记得把前一次的拓扑清空。实验中要记得先把流表清空