RYU 滅龍戰 fourth day (2)

前言

之前試過在ODL調用他們的rest api，一直想自己寫一個基于ODL的rest api，結果還是無果而終。這個小目标卻在RYU身上實作了。今日說法，為你帶來，基于RYU的北向rest api開發

目的

• mac位址表擷取 API

  取得基于RYU 滅龍戰 third day實驗的mac位址表内容。即 對應的mac位址和連接配接端口 以JSON的形式回傳

• mac位址表注冊 API

  向mac位址表加入新的mac位址和端口号，同時加到交換機的流表中

實驗方案

附錄源碼

# Copyright (C) 2016 Nippon Telegraph and Telephone Corporation.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
# implied.
# See the License for the specific language governing permissions and
# limitations under the License.

import json

from ryu.app import simple_switch_13
from ryu.controller import ofp_event
from ryu.controller.handler import CONFIG_DISPATCHER
from ryu.controller.handler import set_ev_cls
from ryu.app.wsgi import ControllerBase
from ryu.app.wsgi import Response
from ryu.app.wsgi import route
from ryu.app.wsgi import WSGIApplication
from ryu.lib import dpid as dpid_lib

simple_switch_instance_name = 'simple_switch_api_app'
url = '/simpleswitch/mactable/{dpid}'

#SimpleSwitchRest13用來擴充實驗一的功能,讓它可以更新mac位址表，其中switch_features_handler方法由于需要更新mac位址表，是以這個地方繼承原方法，進行重寫
class SimpleSwitchRest13(simple_switch_13.SimpleSwitch13):

    #指定RYU使用的為WSGI網頁伺服器
    _CONTEXTS = {'wsgi': WSGIApplication}

    def __init__(self, *args, **kwargs):
        super(SimpleSwitchRest13, self).__init__(*args, **kwargs)
        #已連接配接交換機集合
        self.switches = {}
        wsgi = kwargs['wsgi']
        wsgi.register(SimpleSwitchController,
                      {simple_switch_instance_name: self})

    #接收消息為OPFSwitchFeatures,交換機狀态為接收SwitchFeatures消息
    @set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER)
    def switch_features_handler(self, ev):
        #繼承原方法
        super(SimpleSwitchRest13, self).switch_features_handler(ev)
        datapath = ev.msg.datapath
        self.switches[datapath.id] = datapath
        self.mac_to_port.setdefault(datapath.id, {})

    def set_mac_to_port(self, dpid, entry):
        mac_table = self.mac_to_port.setdefault(dpid, {})
        datapath = self.switches.get(dpid)

        #entry用來存儲已經注冊的mac位址和端口
        entry_port = entry['port']
        entry_mac = entry['mac']

        if datapath is not None:
            parser = datapath.ofproto_parser
            if entry_port not in mac_table.values():

                for mac, port in mac_table.items():

                    # from known device to new device
                    actions = [parser.OFPActionOutput(entry_port)]
                    match = parser.OFPMatch(in_port=port, eth_dst=entry_mac)
                    self.add_flow(datapath, 1, match, actions)

                    # from new device to known device
                    actions = [parser.OFPActionOutput(port)]
                    match = parser.OFPMatch(in_port=entry_port, eth_dst=mac)
                    self.add_flow(datapath, 1, match, actions)

                mac_table.update({entry_mac: entry_port})
        return mac_table

#SimpleSwitchController用來實作收到HTTP請求時所需要回應的方法
class SimpleSwitchController(ControllerBase):

    def __init__(self, req, link, data, **config):
        super(SimpleSwitchController, self).__init__(req, link, data, **config)
        self.simple_switch_app = data[simple_switch_instance_name]

    #參數說明，第一個參數任意名稱，第二個參數url，指定url，使得對應的url為http://<IP>:8080/simpleswitch/mactable/<datapath ID>,第三個參數為GET方法，
    # 第四個參數為指定的URL形式，即simpleswitch/mactable/<datapath ID>的<datapapath ID>要和目标檔案的值相對應
    @route('simpleswitch', url, methods=['GET'],
           requirements={'dpid': dpid_lib.DPID_PATTERN})
    def list_mac_table(self, req, **kwargs):

        simple_switch = self.simple_switch_app
        dpid = dpid_lib.str_to_dpid(kwargs['dpid'])
        #如果dpid不在表中的話，就會傳回404
        if dpid not in simple_switch.mac_to_port:
            return Response(status=404)
        #把對應的dpid對應的mac位址表用json的形式傳回
        mac_table = simple_switch.mac_to_port.get(dpid, {})
        body = json.dumps(mac_table)
        return Response(content_type='application/json', body=body)

    #同上
    @route('simpleswitch', url, methods=['PUT'],
           requirements={'dpid': dpid_lib.DPID_PATTERN})
    def put_mac_table(self, req, **kwargs):

        simple_switch = self.simple_switch_app
        dpid = dpid_lib.str_to_dpid(kwargs['dpid'])
        try:
            new_entry = req.json if req.body else {}
        except ValueError:
            raise Response(status=400)

        if dpid not in simple_switch.mac_to_port:
            return Response(status=404)

        #調用set_mac_to_port方法，注冊相應的mac，port，并下發流表
        try:
            mac_table = simple_switch.set_mac_to_port(dpid, new_entry)
            body = json.dumps(mac_table)
            return Response(content_type='application/json', body=body)
        except Exception as e:
            return Response(status=500)

           

實驗過程

• mininet端

sudo mn --topo single,3 --mac --switch ovsk,protocols=OpenFlow13 --controller remote
           

• 另外一個終端，目錄為ryu/app

ryu-manager --verbose ./simple_switch_rest_13.py
           

• mininet端,讓h1 ping h2 ，看RYU端的變化

h1 ping -c1 h2
           

• 使用curl調用rest api進行擷取mac位址表

• 使用curl調用rest api進行mac位址表的注冊

• 在OVS上檢視流表

可以看得到剛剛PUT的請求，也轉化為流表的形式下發了

總結

學習到這裡，基本了解一些RYU的一些大概架構和結構，知道如何相應事件去做相應的處理。接下來我将

• 學一下RYU對LLDP封包的機制
• 對該機制進行這3天來的實驗彙總，功能包括對LLDP封包做相應處理，并在這基礎上增加rest api的調用