REST Linkage
该小结主要介绍如何添加一个REST Link 函数
RYU本身提供了一个类似WSGI的web服务器功能。借助这个功能，我们可以创建一个REST API。
基于创建的REST API，可以快速的将RYU系统与其他系统或者是浏览器相连接，非常实用的一个功能。
程序解析
在案例中，实现了两个类
- SimpleSwitchRest13
- 继承SimpleSwitch13的功能，即具备父类的三层交换机的基本功能。
- 注册WSGI服务
- 配置mac_to_port
- SimpleSwitchController
- REST API功能实现的主体类
- 返回指定交换机的mac_table
- 更新指定的mac_table条目
SimpleSwitchRest13类实现
_CONTEXTS = {'wsgi': WSGIApplication}该成员变量用于指明Ryu的兼容WSGI的web服务对象。
wsgi = kwargs['wsgi']
wsgi.register(SimpleSwitchController,
{simple_switch_instance_name: self})通过上一步设置的_CONTEXTS成员变量，可以通过kwargs进行实例化一个WSGIApplication。同时使用register方法注册该服务到
controller类上。
@set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER)
def switch_features_handler(self, ev):
super(SimpleSwitchRest13, self).switch_features_handler(ev)
datapath = ev.msg.datapath
self.switches[datapath.id] = datapath
self.mac_to_port.setdefault(datapath.id, {})重写父类的switch_features_handler函数
- 存储datapath到
switches - 初始化MAC 地址表
def set_mac_to_port(self, dpid, entry):
# 获取MAC table
mac_table = self.mac_to_port.setdefault(dpid, {})
# 获取datapath,如果为None，证明没有该交换机
datapath = self.switches.get(dpid)
entry_port = entry['port']
entry_mac = entry['mac']
if datapath is not None:
parser = datapath.ofproto_parser
# 如果entry_port不在mac_table中
if entry_port not in mac_table.values():
# 下发流表
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)
# 添加entry_mac, entry_port到mac_table
mac_table.update({entry_mac: entry_port})
return mac_table该方法将MAC地址和端口注册到指定的交换机。该方法主要被REST API的PUT方法所调用。
SimpleSwitchController类实现
@route('simpleswitch', url, methods=['GET'],
requirements={'dpid': dpid_lib.DPID_PATTERN})借助route装饰器关联方法和URL。参数如下：
- 第一个参数：任何自定义名称
- 第二个参数：指明URL
- 第三个参数：指定http方法
- 第四个参数：指明指定位置的格式，URL(/simpleswitch/mactable/{dpid} 匹配
DPID_PATTERN的描述
当使用GET方式访问到该REST API接口时，调用list_mac_table函数
def list_mac_table(self, req, **kwargs):
simple_switch = self.simple_switch_app
# 获取{dpid}
dpid = dpid_lib.str_to_dpid(kwargs['dpid'])
# 如果没有dpid,返回404
if dpid not in simple_switch.mac_to_port:
return Response(status=404)
# 获取mac_table
mac_table = simple_switch.mac_to_port.get(dpid, {})
body = json.dumps(mac_table)
return Response(content_type='application/json', body=body)# 使用PUT方式设置mac_table
@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)
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)运行分析
启动mininet创建网络拓扑图
sudo mn --topo single,3 --mac --switch ovsk,protocols=OpenFlow13 --controller remote -x启动控制器程序，打印log信息如下：
debugging is available (--enable-debugger option is turned on)
loading app SimpleSwitchRest13
loading app ryu.controller.ofp_handler
creating context wsgi
instantiating app SimpleSwitchRest13 of SimpleSwitchRest13
instantiating app ryu.controller.ofp_handler of OFPHandler
BRICK SimpleSwitchRest13
CONSUMES EventOFPPacketIn
CONSUMES EventOFPSwitchFeatures
BRICK ofp_event
PROVIDES EventOFPPacketIn TO {'SimpleSwitchRest13': set(['main'])}
PROVIDES EventOFPSwitchFeatures TO {'SimpleSwitchRest13': set(['config'])}
CONSUMES EventOFPEchoReply
CONSUMES EventOFPSwitchFeatures
CONSUMES EventOFPPortDescStatsReply
CONSUMES EventOFPHello
CONSUMES EventOFPErrorMsg
CONSUMES EventOFPEchoRequest
CONSUMES EventOFPPortStatus
(22238) wsgi starting up on http://0.0.0.0:8080这里我们可以看到，wsgi服务已经启动，端口号为8080
查询s1的默认MAC table
curl -X GET http://127.0.0.1:8080/simpleswitch/mactable/0000000000000001返回为{}
在mininet中执行
mininet> h1 ping -c 1 h2log信息打印如下信息：
EVENT ofp_event->SimpleSwitchRest13 EventOFPPacketIn
packet in 1 00:00:00:00:00:01 ff:ff:ff:ff:ff:ff 1
EVENT ofp_event->SimpleSwitchRest13 EventOFPPacketIn
packet in 1 00:00:00:00:00:02 00:00:00:00:00:01 2
EVENT ofp_event->SimpleSwitchRest13 EventOFPPacketIn
packet in 1 00:00:00:00:00:01 00:00:00:00:00:02 1返回了三条PackageIn消息（ARP过程）
- host1发起的ARP请求，并广播
- host2发起的ARP请求，MAC地址是host1
- ICMP echo reply request 从host1 发生到host2
此刻按照设计，已经添加了两条条目到MAC table,再次查询进行验证。
curl -X GET http://127.0.0.1:8080/simpleswitch/mactable/0000000000000001返回如下,证明符合实验预期：
{"00:00:00:00:00:02": 2, "00:00:00:00:00:01": 1}测试POST API接口,添加h3到MAC Table
curl -X PUT -d '{"mac" : "00:00:00:00:00:03", "port" : 3}' http://127.0.0.1:8080/simpleswitch/mactable/0000000000000001返回：
{"00:00:00:00:00:03": 3, "00:00:00:00:00:02": 2, "00:00:00:00:00:01": 1}证明h3 mac已经被添加到MAC table。因为h3已经被添加到MAC Table中，所以理论上当h1 ping h3时将不再通过ARP查找到h3.
测试：在mininet中执行命令
mininet> h1 ping c1 h3
PING 10.0.0.3 (10.0.0.3) 56(84) bytes of data.
64 bytes from 10.0.0.3: icmp_seq=1 ttl=64 time=2.48 ms
--- 10.0.0.3 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 2.480/2.480/2.480/0.000 ms控制器log信息如下：
EVENT ofp_event->SimpleSwitchRest13 EventOFPPacketIn
packet in 1 00:00:00:00:00:01 ff:ff:ff:ff:ff:ff 1我们可以看到，只有h1在不知道h3地址的情况下，发起ARP广播，将PackageIn消息发送到控制器，而不再出现以后的一系列消息。这证明
MAC Table中添加的条目成功生效，符合预期情况。
