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
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
（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
