SDN實驗---Ryu的應用開發（四）基於跳數的最短路徑轉發原理

時間  2019-11-06
標籤 sdn 實驗 ryu 應用 開發 基於 最短 路徑 轉發 原理 简体版
原文   原文鏈接

一：實現最短跳數轉發

 （一）原理

 

推文：迪傑斯特拉算法和弗洛伊德算法

二：代碼實現 

（一）所有代碼

from ryu.base import app_manager
from ryu.controller.handler import set_ev_cls
from ryu.controller import ofp_event
from ryu.controller.handler import MAIN_DISPATCHER,CONFIG_DISPATCHER
from ryu.lib.packet import packet,ethernet
from ryu.topology import event
from ryu.topology.api import get_switch,get_link
from ryu.ofproto import ofproto_v1_3

import networkx as nx

class MyShortestForwarding(app_manager.RyuApp):
    '''
    class to achive shortest path to forward, based on minimum hop count
    '''
    OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]

    def __init__(self,*args,**kwargs):
        super(MyShortestForwarding,self).__init__(*args,**kwargs)

        #set data structor for topo construction
        self.network = nx.DiGraph()        #store the dj graph
        self.paths = {}        #store the shortest path
        self.topology_api_app = self

    @set_ev_cls(ofp_event.EventOFPSwitchFeatures,CONFIG_DISPATCHER)
    def switch_features_handler(self,ev):
        '''
        manage the initial link between switch and controller
        '''
        msg = ev.msg
        datapath = msg.datapath
        ofproto = datapath.ofproto
        ofp_parser = datapath.ofproto_parser

        match = ofp_parser.OFPMatch()    #for all packet first arrive, match it successful, send it ro controller
        actions  = [ofp_parser.OFPActionOutput(
                            ofproto.OFPP_CONTROLLER,ofproto.OFPCML_NO_BUFFER
                            )]

        self.add_flow(datapath, 0, match, actions)

    def add_flow(self,datapath,priority,match,actions):
        '''
        fulfil the function to add flow entry to switch
        '''
        ofproto = datapath.ofproto
        ofp_parser = datapath.ofproto_parser

        inst = [ofp_parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS,actions)]

        mod = ofp_parser.OFPFlowMod(datapath=datapath,priority=priority,match=match,instructions=inst)

        datapath.send_msg(mod)


    @set_ev_cls(ofp_event.EventOFPPacketIn,MAIN_DISPATCHER)
    def packet_in_handler(self,ev):
        '''
        manage the packet which comes from switch
        '''
        #first get event infomation
        msg = ev.msg
        datapath = msg.datapath
        ofproto = datapath.ofproto
        ofp_parser = datapath.ofproto_parser

        in_port = msg.match['in_port']
        dpid = datapath.id

        #second get ethernet protocol message
        pkt = packet.Packet(msg.data)
        eth_pkt = pkt.get_protocol(ethernet.ethernet)

        eth_src = eth_pkt.src     #note: mac info willn`t  change in network
        eth_dst = eth_pkt.dst

        out_port = self.get_out_port(datapath,eth_src,eth_dst,in_port)
        actions = [ofp_parser.OFPActionOutput(out_port)]

        if out_port != ofproto.OFPP_FLOOD:
            match = ofp_parser.OFPMatch(in_port=in_port,eth_dst=eth_dst)
            self.add_flow(datapath,1,match,actions)

        out = ofp_parser.OFPPacketOut(
                datapath=datapath,buffer_id=msg.buffer_id,in_port=in_port,
                actions=actions,data=msg.data
            )

        datapath.send_msg(out)

    @set_ev_cls(event.EventSwitchEnter,[CONFIG_DISPATCHER,MAIN_DISPATCHER])    #event is not from openflow protocol, is come from switchs` state changed, just like: link to controller at the first time or send packet to controller
    def get_topology(self,ev):
        '''
        get network topo construction, save info in the dict
        '''

        #store nodes info into the Graph
        switch_list = get_switch(self.topology_api_app,None)    #------------need to get info,by debug
        switches = [switch.dp.id for switch in switch_list]
        self.network.add_nodes_from(switches)

        #store links info into the Graph
        link_list = get_link(self.topology_api_app,None)
        #port_no, in_port    ---------------need to debug, get diffirent from  both
        links = [(link.src.dpid,link.dst.dpid,{'attr_dict':{'port':link.dst.port_no}}) for link in link_list]    #add edge, need src,dst,weigtht
        self.network.add_edges_from(links)

        links  = [(link.dst.dpid,link.src.dpid,{'attr_dict':{'port':link.dst.port_no}}) for link in link_list]
        self.network.add_edges_from(links)

    def get_out_port(self,datapath,src,dst,in_port):
        '''
        datapath: is current datapath info
        src,dst: both are the host info
        in_port: is current datapath in_port
        '''
        dpid = datapath.id

        #the first :Doesn`t find src host at graph
        if src not in self.network:
            self.network.add_node(src)
            self.network.add_edge(dpid, src, attr_dict={'port':in_port})
            self.network.add_edge(src, dpid)
            self.paths.setdefault(src, {})

        #second: search the shortest path, from src to dst host
        if dst in self.network:
            if dst not in self.paths[src]:    #if not cache src to dst path,then to find it
                path = nx.shortest_path(self.network,src,dst)
                self.paths[src][dst]=path

            path = self.paths[src][dst]
            next_hop = path[path.index(dpid)+1]
            #print("1ooooooooooooooooooo")
            #print(self.network[dpid][next_hop])
            out_port = self.network[dpid][next_hop]['attr_dict']['port']
            #print("2ooooooooooooooooooo")
            #print(out_port)

            #get path info
            #print("6666666666 find dst")
            print(path)
        else:
            out_port = datapath.ofproto.OFPP_FLOOD    #By flood, to find dst, when dst get packet, dst will send a new back,the graph will record dst info
            #print("8888888888 not find dst")
        return out_port

（二）注意：因爲各類版本的不一樣，致使咱們使用函數的時候可能有所不一樣，須要咱們本身去調試

1.安裝networkx模塊

pip3 install networkx
pip3 install multiqc

2.出現self.network.add_edge(dpid, src, {'port':in_port})使用時，會出現參數太多

self.network.add_edge(dpid, src, attr_dict={'port':in_port})　　attr_dict是對咱們提供的擴展成熟

3.學會代碼調試和思考

三：代碼講解

（一）不變代碼：實現初始鏈接處理和公共函數--下發流表

    @set_ev_cls(ofp_event.EventOFPSwitchFeatures,CONFIG_DISPATCHER)
    def switch_features_handler(self,ev):
        '''
        manage the initial link between switch and controller
        '''
        msg = ev.msg
        datapath = msg.datapath
        ofproto = datapath.ofproto
        ofp_parser = datapath.ofproto_parser

        match = ofp_parser.OFPMatch()    #for all packet first arrive, match it successful, send it ro controller
        actions  = [ofp_parser.OFPActionOutput(
                            ofproto.OFPP_CONTROLLER,ofproto.OFPCML_NO_BUFFER
                            )]

        self.add_flow(datapath, 0, match, actions)

    def add_flow(self,datapath,priority,match,actions):
        '''
        fulfil the function to add flow entry to switch
        '''
        ofproto = datapath.ofproto
        ofp_parser = datapath.ofproto_parser

        inst = [ofp_parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS,actions)]

        mod = ofp_parser.OFPFlowMod(datapath=datapath,priority=priority,match=match,instructions=inst)

        datapath.send_msg(mod)

（二）實現獲取網絡拓撲結構

class MyShortestForwarding(app_manager.RyuApp):
    '''
    class to achive shortest path to forward, based on minimum hop count
    '''
    OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]

    def __init__(self,*args,**kwargs):
        super(MyShortestForwarding,self).__init__(*args,**kwargs)

        #set data structor for topo construction
 self.network = nx.DiGraph() #store the dj graph　　設置圖結構存儲信息 self.paths = {} #store the shortest path self.topology_api_app = self

    @set_ev_cls(event.EventSwitchEnter,[CONFIG_DISPATCHER,MAIN_DISPATCHER])    #event is not from openflow protocol, is come from switchs` state changed, just like: link to controller at the first time or send packet to controller
    def get_topology(self,ev):
        '''
 get network topo construction, save info in the dict　　因爲監聽交換機信息進入，觸發，注意事件不在flow協議類，在from ryu.topology import event中 '''

        #store nodes info into the Graph
        switch_list = get_switch(self.topology_api_app,None)    #------------need to get info,by debug
        switches = [switch.dp.id for switch in switch_list]
        self.network.add_nodes_from(switches)

        #store links info into the Graph
        link_list = get_link(self.topology_api_app,None)
        #port_no, in_port    ---------------need to debug, get diffirent from  both
        links = [(link.src.dpid,link.dst.dpid,{'attr_dict':{'port':link.dst.port_no}}) for link in link_list]    #add edge, need src,dst,weigtht
        self.network.add_edges_from(links)

        links  = [(link.dst.dpid,link.src.dpid,{'attr_dict':{'port':link.dst.port_no}}) for link in link_list]
        self.network.add_edges_from(links)

補充：event.EventSwitchEnter---因爲監聽交換機信息進入，觸發，注意事件不在flow協議類，在from ryu.topology import event中

（三）實現下一跳端口獲取（根據圖獲取最短路徑，從中獲取信息）

    def get_out_port(self,datapath,src,dst,in_port):
        '''
        datapath: is current datapath info
        src,dst: both are the host info
        in_port: is current datapath in_port
        '''
        dpid = datapath.id

        #the first :Doesn`t find src host at graph
        if src not in self.network:　　　　#根據src主機是否在網絡中，決定是否新添加進入 self.network.add_node(src) self.network.add_edge(dpid, src, attr_dict={'port':in_port}) self.network.add_edge(src, dpid) self.paths.setdefault(src, {})　　#設置數據結構：用於保存每一個源主機到各個目的主機的最短路徑{src1:{dst1:[],dst2:[],dst3:[]....},src2:{dst1:[],dst2:[],dst3:[]....},}

        #second: search the shortest path, from src to dst host
        if dst in self.network: if dst not in self.paths[src]: #if not cache src to dst path,then to find it path = nx.shortest_path(self.network,src,dst) self.paths[src][dst]=path  path = self.paths[src][dst] next_hop = path[path.index(dpid)+1]　　#根據數據結構獲取下一跳datapath信息
            #print("1ooooooooooooooooooo")
            #print(self.network[dpid][next_hop])
            out_port = self.network[dpid][next_hop]['attr_dict']['port']　　#根據該id和下一跳id去獲取出端口，進行數據轉發
            #print("2ooooooooooooooooooo")
            #print(out_port)

            #get path info
            #print("6666666666 find dst")
            print(path)
        else:　　#不然是泛洪處理
            out_port = datapath.ofproto.OFPP_FLOOD    #By flood, to find dst, when dst get packet, dst will send a new back,the graph will record dst info
            #print("8888888888 not find dst")
        return out_port

（四）實現包接收，計算最短路徑，按照最短路徑進行動做下發《重點》

    @set_ev_cls(ofp_event.EventOFPPacketIn,MAIN_DISPATCHER)
    def packet_in_handler(self,ev):
        '''
        manage the packet which comes from switch
        '''
        #first get event infomation
 msg = ev.msg datapath = msg.datapath ofproto = datapath.ofproto ofp_parser = datapath.ofproto_parser in_port = msg.match['in_port'] dpid = datapath.id

        #second get ethernet protocol message
 pkt = packet.Packet(msg.data) eth_pkt = pkt.get_protocol(ethernet.ethernet) eth_src = eth_pkt.src #note: mac info willn`t change in network eth_dst = eth_pkt.dst   out_port = self.get_out_port(datapath,eth_src,eth_dst,in_port)　　#這裏進行獲取下一跳端口 actions = [ofp_parser.OFPActionOutput(out_port)] if out_port != ofproto.OFPP_FLOOD:
            match = ofp_parser.OFPMatch(in_port=in_port,eth_dst=eth_dst)
            self.add_flow(datapath,1,match,actions)

        out = ofp_parser.OFPPacketOut(
                datapath=datapath,buffer_id=msg.buffer_id,in_port=in_port,
                actions=actions,data=msg.data
            )

        datapath.send_msg(out)

三：實驗演示：注意開啓順序，不然可能致使其餘錯誤

（一）啓動Ryu控制器  observe-links命令會致使控制器在運行期間 會不間斷地發送LLDP數據包進行鏈路探測

ryu-manager my_shortest_forward.py --observe-links --verbose

（二）啓動Mininet

sudo mn --topo=tree,2,2 --controller=remote --mac

（三）Ryu查看信息

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