2019 SDN上机第5次作业

1.浏览RYU官网学习RYU控制器的安装和RYU开发入门教程，提交你对于教程代码的理解，包括但不限于：

• 描述官方教程实现了一个什么样的交换机功能？

答：将接收到的数据包发送到所有端口的功能

• 控制器设定交换机支持什么版本的OpenFlow？

答：OpenFlow1.0

• 控制器设定了交换机如何处理数据包？

答：当ryu控制器接收到数据包时，通过set_ev_cls来告知交换机，调用新增函数packet_in_handler来处理数据包，即：

@set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)

packet_in_handler函数中，通过OFPActionOutput（packet_out）指定将要发送数据包的端口（packet_out=OFPP_FLOOD意为发送所有端口），OFPPacketOut用于构建packet_out数据，然后调用send_msg发送数据。

def packet_in_handler(self, ev):
    msg = ev.msg
    dp = msg.datapath
    ofp = dp.ofproto
    ofp_parser = dp.ofproto_parser

    actions = [ofp_parser.OFPActionOutput(ofp.OFPP_FLOOD)]
    out = ofp_parser.OFPPacketOut(
        datapath=dp, buffer_id=msg.buffer_id, in_port=msg.in_port,
        actions=actions)
    dp.send_msg(out)

2.根据官方教程和提供的示例代码（SimpleSwitch.py），将具有自学习功能的交换机代码（SelfLearning.py）补充完整

• 交换机代码：

from ryu.base import app_manager
from ryu.controller import ofp_event
from ryu.controller.handler import MAIN_DISPATCHER
from ryu.controller.handler import set_ev_cls
from ryu.ofproto import ofproto_v1_0

from ryu.lib.mac import haddr_to_bin
from ryu.lib.packet import packet
from ryu.lib.packet import ethernet
from ryu.lib.packet import ether_types
from ryu.lib.packet import ipv4


class SimpleSwitch(app_manager.RyuApp):
    # TODO define OpenFlow 1.0 version for the switch
    # add your code here
    OFP_VERSIONS = [ofproto_v1_0.OFP_VERSION]


    def __init__(self, *args, **kwargs):
        super(SimpleSwitch, self).__init__(*args, **kwargs)
        self.mac_to_port = {}
    
    
    def add_flow(self, datapath, in_port, dst, src, actions):
        ofproto = datapath.ofproto

        match = datapath.ofproto_parser.OFPMatch(
            in_port=in_port,
            dl_dst=haddr_to_bin(dst), dl_src=haddr_to_bin(src))

        mod = datapath.ofproto_parser.OFPFlowMod(
            datapath=datapath, match=match, cookie=0,
            command=ofproto.OFPFC_ADD, idle_timeout=0, hard_timeout=0,
            priority=ofproto.OFP_DEFAULT_PRIORITY,
            flags=ofproto.OFPFF_SEND_FLOW_REM, actions=actions)
        # TODO send modified message out
        # add your code here
        datapath.send_msg(mod)
    @set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
    def _packet_in_handler(self, ev):
        msg = ev.msg
        datapath = msg.datapath
        ofproto = datapath.ofproto

        pkt = packet.Packet(msg.data)
        eth = pkt.get_protocol(ethernet.ethernet)

        if eth.ethertype == ether_types.ETH_TYPE_LLDP:
            # ignore lldp packet
            return
        if eth.ethertype == ether_types.ETH_TYPE_IPV6:
            # ignore ipv6 packet
            return       
        
        dst = eth.dst
        src = eth.src
        dpid = datapath.id
        self.mac_to_port.setdefault(dpid, {})

        self.logger.info("packet in DPID:%s MAC_SRC:%s MAC_DST:%s IN_PORT:%s", dpid, src, dst, msg.in_port)

        # learn a mac address to avoid FLOOD next time.
        self.mac_to_port[dpid][src] = msg.in_port

        if dst in self.mac_to_port[dpid]:
            out_port = self.mac_to_port[dpid][dst]
        else:
            out_port = ofproto.OFPP_FLOOD

        # TODO define the action for output
        # add your code here
        actions = [datapath.ofproto_parser.OFPActionOutput(out_port)]

        # install a flow to avoid packet_in next time
        if out_port != ofproto.OFPP_FLOOD:
            self.logger.info("add flow s:DPID:%s Match:[ MAC_SRC:%s MAC_DST:%s IN_PORT:%s ], Action:[OUT_PUT:%s] ", dpid, src, dst, msg.in_port, out_port)
            self.add_flow(datapath, msg.in_port, dst, src, actions)

        data = None
        if msg.buffer_id == ofproto.OFP_NO_BUFFER:
            data = msg.data
        

        # TODO define the OpenFlow Packet Out
        # add your code here
        out = datapath.ofproto_parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id, in_port=msg.in_port,  actions=actions, data=data)
        datapath.send_msg(out)
        print ("PACKET_OUT...")

• 四个补充代码：

# TODO define OpenFlow 1.0 version for the switch
# add your code here
OFP_VERSIONS = [ofproto_v1_0.OFP_VERSION]

# TODO send modified message out
# add your code here
datapath.send_msg(mod)

# TODO define the action for output
# add your code here
actions = [datapath.ofproto_parser.OFPActionOutput(out_port)]

# TODO define the OpenFlow Packet Out
# add your code here
out = datapath.ofproto_parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id, in_port=msg.in_port,  actions=actions, data=data)
datapath.send_msg(out)

3.在mininet创建一个最简拓扑，并连接RYU控制器

• mininet创建拓扑:
  (注:控制器必须改为远程控制)

• 连接ryu控制器:

ryu-manager SelfLearning.py

4.验证自学习交换机的功能，提交分析过程和验证结果

• pingall：
  发现h1,h2可以ping通了

• 查看下发流表：
  (第一次无下发流表，第二次为连接ryu控制器并pingall后)

• 结果图

5.写下你的实验体会

• 实验感想
  虽然实验并不复杂，主要过程是读懂代码，但是空格缩进的问题让我纠结了好久，属实心态爆炸。
  源代码中缩进4个字符，直接复制到linux虚拟机中会变成缩进8个字符，导致py文件运行时报错，需要格外注意。