一：实现最短跳数转发
（一）原理
推文：迪杰斯特拉算法和弗洛伊德算法
二：代码实现
（一）全部代码
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：由于各种版本的不同，导致我们使用函数的时候可能有所不同，需要我们自己去调试
1.安装networkx模块，若是下载太慢或者出错，换国内源：在末尾加上-i https://pypi.tuna.tsinghua.edu.cn/simple
pip3 install networkx
pip3 install multiqc
2.出现self.network.add_edge(dpid, src, {'port':in_port})使用时，会出现参数太多
self.network.add_edge(dpid, src, attr_dict={'port':in_port}) attr_dict是对我们提供的扩展成熟
3.学会代码调试和思考
三：代码讲解
（一）不变代码：实现初始连接处理和公共函数--下发流表
@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）实现获取网络拓扑结构
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 设置图结构存储信息 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 由于监听交换机信息进入，触发，注意事件不在flow协议类，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)
补充：event.EventSwitchEnter---由于监听交换机信息进入，触发，注意事件不在flow协议类，在from ryu.topology import event中
（三）实现下一跳端口获取（根据图获取最短路径，从中获取信息）
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: #根据src主机是否在网络中，决定是否新添加进入 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, {}) #设置数据结构：用于保存每个源主机到各个目的主机的最短路径{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] #根据数据结构获取下一跳datapath信息 #print("1ooooooooooooooooooo") #print(self.network[dpid][next_hop]) out_port = self.network[dpid][next_hop]['attr_dict']['port'] #根据该id和下一跳id去获取出端口，进行数据转发 #print("2ooooooooooooooooooo") #print(out_port) #get path info #print("6666666666 find dst") print(path) else: #否则是泛洪处理 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）实现包接收，计算最短路径，按照最短路径进行动作下发《重点》
@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) #这里进行获取下一跳端口 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：实验演示：注意开启顺序，否则可能导致其他错误
（一）启动Ryu控制器 observe-links命令会导致控制器在运行期间 会不间断地发送LLDP数据包进行链路探测
ryu-manager my_shortest_forward.py --observe-links --verbose
（二）启动Mininet
sudo mn --topo=tree,2,2 --controller=remote --mac
（三）Ryu查看信息
