最近学习了有关SDN中路由的选择，发现Ryu中没有像POX那样给出默认的最短路径，我就试着把POX中的l2_multi.py修改了一下移植到Ryu中，最终实现在Ryu中计算源点和目的节点的最短路径。
源码：
# Copyright (C) 2011 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.
from ryu.base import app_manager
from ryu.controller import ofp_event
from ryu.controller.handler import CONFIG_DISPATCHER, MAIN_DISPATCHER, DEAD_DISPATCHER
from ryu.controller.handler import set_ev_cls
from ryu.ofproto import ofproto_v1_3
from ryu.lib.packet import packet
from ryu.lib.packet import ethernet
from ryu.lib.packet import arp
from ryu.lib.packet import ipv4
from collections import defaultdict
from ryu.topology.api import get_switch,get_link
from ryu.topology import event,switches
ARP = arp.arp.__name__
ETHERNET = ethernet.ethernet.__name__
ETHERNET_MULTICAST = "ff:ff:ff:ff:ff:ff"
adjacency = defaultdict(lambda: defaultdict(lambda: None))
path_map = defaultdict(lambda: defaultdict(lambda: (None, None)))
sws = []
switches={}
mac_map={}
def _get_raw_path(src, dst):
"""
Get a raw path (just a list of nodes to traverse)
"""
if len(path_map) == 0: _dijkstra_paths()
if src is dst:
# We're here!
return []
if path_map[src][dst][0] is None:
return None
intermediate = path_map[src][dst][1]
if intermediate is None:
# Directly connected
return []
return _get_raw_path(src, intermediate) + [intermediate] + \
_get_raw_path(intermediate, dst)
def _get_path(src, dst, first_port, final_port):
"""
Gets a cooked path -- a list of (node,in_port,out_port)
"""
# Start with a raw path...
print src
print dst
if src == dst:
path = [src]
else:
path = _get_raw_path(src, dst)
if path is None: return None
path = [src] + path + [dst]
# Now add the ports
r = []
in_port = first_port
for s1, s2 in zip(path[:-1], path[1:]):
out_port = adjacency[s1][s2]
r.append((s1, in_port, out_port))
in_port = adjacency[s2][s1]
r.append((dst, in_port, final_port))
print 'R is %s' % r
return r
def _dijkstra_paths():
path_map.clear()
for k in sws:
for j, port in adjacency[k].iteritems():
if port is None:
continue
path_map[k][j] = (1, None)
path_map[k][k] = (0, None)
print adjacency[k]
for t in sws:
final_point = []
final_point.append(t)
for i in range(len(sws) - 1):
min_path = 999
for p in sws:
if p not in final_point:
if path_map[t][p][0] is not None and path_map[t][p][0] < min_path:
min_path = path_map[t][p][0]
temp = p
final_point.append(temp)
for m in sws:
if m not in final_point:
if path_map[t][m][0] is None and path_map[t][temp][0] is not None and path_map[temp][m][
0] is not None:
path_map[t][m] = (path_map[t][temp][0] + path_map[temp][m][0], temp)
elif path_map[t][temp][0] is not None and path_map[temp][m][0] is not None and path_map[t][m][
0] is not None:
if path_map[t][temp][0] + path_map[temp][m][0] < path_map[t][m][0]:
path_map[t][m] = (path_map[t][temp][0] + path_map[temp][m][0], temp)
print path_map
class SimpleSwitch13(app_manager.RyuApp):
OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]
def __init__(self, *args, **kwargs):
super(SimpleSwitch13, self).__init__(*args, **kwargs)
self.mac_to_port = {}
self.arp_table = {}
self.sw = {}
self.port_tx = {}
self.datapaths = {}
self.datapath_list={}
self.topology_api_app=self
@set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER)
def switch_features_handler(self, ev):
datapath = ev.msg.datapath
ofproto = datapath.ofproto
parser = datapath.ofproto_parser
switches[datapath.id]=datapath
# install table-miss flow entry
#
# We specify NO BUFFER to max_len of the output action due to
# OVS bug. At this moment, if we specify a lesser number, e.g.,
# 128, OVS will send Packet-In with invalid buffer_id and
# truncated packet data. In that case, we cannot output packets
# correctly. The bug has been fixed in OVS v2.1.0.
match = parser.OFPMatch()
actions = [parser.OFPActionOutput(ofproto.OFPP_CONTROLLER,
ofproto.OFPCML_NO_BUFFER)]
self.add_flow(datapath, 0, match, actions)
def add_flow(self, datapath, priority, match, actions):
ofproto = datapath.ofproto
parser = datapath.ofproto_parser
inst = [parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS,
actions)]
mod = parser.OFPFlowMod(datapath=datapath, priority=priority,
hard_timeout=20,
match=match, instructions=inst)
datapath.send_msg(mod)
@set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
def _packet_in_handler(self, ev):
# If you hit this you might want to increase
# the "miss_send_length" of your switch
if ev.msg.msg_len < ev.msg.total_len:
self.logger.debug("packet truncated: only %s of %s bytes",
ev.msg.msg_len, ev.msg.total_len)
msg = ev.msg
datapath = msg.datapath
ofproto = datapath.ofproto
parser = datapath.ofproto_parser
in_port = msg.match['in_port']
pkt = packet.Packet(msg.data)
eth = pkt.get_protocols(ethernet.ethernet)[0]
#avoid broadcast from LLDP
if eth.ethertype==35020:
return
dst = eth.dst
src = eth.src
loc=('00-00-00-00-00-0'+str(datapath.id),in_port)
oldloc=mac_map.get(src)
if oldloc is None:
mac_map[src]=loc
elif src not in mac_map:
mac_map[src]=loc
dpid = datapath.id
self.mac_to_port.setdefault(dpid, {})
header_list = dict(
(p.protocol_name, p) for p in pkt.protocols if type(p) != str)
if ARP in header_list:
self.arp_table[header_list[ARP].src_ip] = src # ARP learning
self.logger.info("packet in %s %s %s %s", dpid, src, dst, in_port)
# learn a mac address to avoid FLOOD next time.
if src not in self.mac_to_port[dpid]: #record only one in_port
self.mac_to_port[dpid][src] = in_port
if dst in self.mac_to_port[dpid]:
out_port = self.mac_to_port[dpid][dst]
temp_src=mac_map[src]
temp_dst=mac_map[dst]
self.install_path(temp_src[0],temp_dst[0], temp_src[1], temp_dst[1], ev)
self.logger.info("out_port: %s", out_port)
else:
out_port = ofproto.OFPP_FLOOD
print"flood!"
actions = [parser.OFPActionOutput(out_port)]
# install a flow to avoid packet_in next time
if out_port != ofproto.OFPP_FLOOD:
match = parser.OFPMatch(in_port=in_port, eth_dst=dst)
data = None
if msg.buffer_id == ofproto.OFP_NO_BUFFER:
data = msg.data
out = parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id,
in_port=in_port, actions=actions, data=data)
datapath.send_msg(out)
@set_ev_cls(ofp_event.EventOFPStateChange, [MAIN_DISPATCHER, DEAD_DISPATCHER])
def state_change_handler(self, ev):
datapath = ev.datapath
if ev.state == MAIN_DISPATCHER:
if datapath.id == 1:
self.datapaths[datapath.id] = datapath
if not datapath.id in self.datapath_list:
self.datapath_list[datapath.id]=datapath
elif ev.state == DEAD_DISPATCHER:
if datapath.id in self.datapaths:
del self.datapaths[datapath.id]
def install_path(self,src_sw, dst_sw, in_port, last_port, ev):
"""
Attempts to install a path between this switch and some destination
"""
p = _get_path(src_sw, dst_sw, in_port, last_port)
self._install_path(p, ev)
# Now reverse it and install it backwards
# (we'll just assume that will work)
p = [(sw, out_port, in_port) for sw, in_port, out_port in p]
self._install_path(p, ev)
def _install_path(self, p, ev):
msg = ev.msg
datapath = msg.datapath
ofproto = datapath.ofproto
parser = datapath.ofproto_parser
for sw, in_port, out_port in p:
match = parser.OFPMatch(in_port=in_port)
actions = [parser.OFPActionOutput(out_port)]
ID=int(sw[-1:])
datapath=self.datapath_list[ID]
self.add_flow(datapath, 1, match, actions)
@set_ev_cls(event.EventSwitchEnter)
def get_topology(self,ev):
switch_list=get_switch(self.topology_api_app,None)
global sws
# assign mac for swtich to easy read
sws=['00-00-00-00-00-0'+ str(switch.dp.id) for switch in switch_list]
links_list=get_link(self.topology_api_app,None)
for link in links_list:
sw_src='00-00-00-00-00-0'+ str(link.src.dpid)
sw_dst='00-00-00-00-00-0'+ str(link.dst.dpid)
adjacency[sw_src][sw_dst]=link.src.port_no
实验环境：Ryu 3.15 + Openflow1.3 +Openvswitch 2.1.3
部分代码说明：
1.
@set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
def _packet_in_handler(self, ev):
# If you hit this you might want to increase
# the "miss_send_length" of your switch
if ev.msg.msg_len < ev.msg.total_len:
self.logger.debug("packet truncated: only %s of %s bytes",
ev.msg.msg_len, ev.msg.total_len)
：
：if eth.ethertype==35020: return 是为了防止因链路发现协议导致网络瘫痪。
mac_map存储的是host和与它相连接的switch的映射。
在此函数中要对arp广播包进行处理避免由广播风暴造成网络瘫痪。
2.
@set_ev_cls(ofp_event.EventOFPStateChange, [MAIN_DISPATCHER, DEAD_DISPATCHER])
def state_change_handler(self, ev):
datapath = ev.datapath
if ev.state == MAIN_DISPATCHER:
if datapath.id == 1:
self.datapaths[datapath.id] = datapath
if not datapath.id in self.datapath_list:
self.datapath_list[datapath.id]=datapath
elif ev.state == DEAD_DISPATCHER:
if datapath.id in self.datapaths:
del self.datapaths[datapath.id]datapath_list存储的是网络中所有的datapath，为了将流表安装到指定的交换机。
3.
@set_ev_cls(event.EventSwitchEnter)
def get_topology(self,ev):
switch_list=get_switch(self.topology_api_app,None)
global sws
# assign mac for swtich to easy read
sws=['00-00-00-00-00-0'+ str(switch.dp.id) for switch in switch_list]
links_list=get_link(self.topology_api_app,None)
for link in links_list:
sw_src='00-00-00-00-00-0'+ str(link.src.dpid)
sw_dst='00-00-00-00-00-0'+ str(link.dst.dpid)
adjacency[sw_src][sw_dst]=link.src.port_no此函数是发现网络拓扑结构：交换机、链路、端口，adjacency存储的是整个网络的拓扑。
启动模块时要添加–observe-links，否则链路发现模块不起作用。
