实验6：开源控制器实践——RYU

一、实验目的
能够独立部署RYU控制器；
能够理解RYU控制器实现软件定义的集线器原理；
能够理解RYU控制器实现软件定义的交换机原理。
二、实验环境
Ubuntu 20.04 Desktop amd64

三、实验要求
（一）基本要求
搭建下图所示SDN拓扑，协议使用Open Flow 1.0，并连接Ryu控制器，通过Ryu的图形界面查看网络拓扑。

阅读Ryu文档的The First Application一节，运行当中的L2Switch，h1 ping h2或h3，在目标主机使用 tcpdump 验证L2Switch，分析L2Switch和POX的Hub模块有何不同。

二者实现的都是洪泛发送ICMP报文，所以在h2和h3可以看到都有抓到数据包。
不同之处在于：Ryu中，L2Switch下发的流表无法查看；而POX中Hub则可以查看
编程修改L2Switch.py，另存为L2xxxxxxxxx.py，使之和POX的Hub模块的变得一致？（xxxxxxxxx为学号）



（二）进阶要求
阅读Ryu关于simple_switch.py和simple_switch_1x.py的实现，以simple_switch_13.py为例，完成其代码的注释工作，并回答下列问题：

def __init__(self, *args, **kwargs):
    super(SimpleSwitch13, self).__init__(*args, **kwargs)
    self.mac_to_port = {}  # 定义保存mac地址到端口的一个映射

# 处理SwitchFeatures事件
@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

    # 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()  # match指流表项匹配，OFPMatch()指不匹配任何信息
    actions = [parser.OFPActionOutput(ofproto.OFPP_CONTROLLER,
                                      ofproto.OFPCML_NO_BUFFER)]
    self.add_flow(datapath, 0, match, actions)

# add_flow()增加流表项
# datapath：指定的 Switch
# priority：此规则的优先权
# match：此规则的 Match 条件
# actions：动作
def add_flow(self, datapath, priority, match, actions, buffer_id=None):
    # 获取交换机信息
    ofproto = datapath.ofproto
    parser = datapath.ofproto_parser
    # 对action进行包装
    inst = [parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS,
                                         actions)]
    # 判断是否存在buffer_id，并生成mod对象
    if buffer_id:
        mod = parser.OFPFlowMod(datapath=datapath, buffer_id=buffer_id,
                                priority=priority, match=match,
                                instructions=inst)
    else:
        mod = parser.OFPFlowMod(datapath=datapath, priority=priority,
                                match=match, instructions=inst)
    # 发送出去
    datapath.send_msg(mod)

# 处理PacketIn事件
@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)
    # 解析数据结构
    msg = ev.msg    # ev.msg 是代表packet_in data structure对象
    datapath = msg.datapath
    # dp. ofproto 和 dp.ofproto_parser 是代表 Ryu 和交换机谈判的 OpenFlow 协议的对象
    # dp.ofproto and dp.ofproto_parser are objects that represent the OpenFlow protocol that Ryu and the switch negotiated
    ofproto = datapath.ofproto
    parser = datapath.ofproto_parser
    in_port = msg.match['in_port']  # 获取源端口

    pkt = packet.Packet(msg.data)
    eth = pkt.get_protocols(ethernet.ethernet)[0]

    if eth.ethertype == ether_types.ETH_TYPE_LLDP:
        # 忽略LLDP类型的数据包
        # ignore lldp packet
        return
    dst = eth.dst  # 获取目的端口
    src = eth.src  # 获取源端口

    dpid = format(datapath.id, "d").zfill(16)
    self.mac_to_port.setdefault(dpid, {})

    self.logger.info("packet in %s %s %s %s", dpid, src, dst, in_port)

    # 学习包的源地址，和交换机上的入端口绑定
    # learn a mac address to avoid FLOOD next time.
    self.mac_to_port[dpid][src] = in_port

    # 查看是否已经学习过该目的mac地址
    if dst in self.mac_to_port[dpid]:  # 如果目的地址存在于mac_to_port中
        out_port = self.mac_to_port[dpid][dst]
    # 否则，洪泛
    else:
        out_port = ofproto.OFPP_FLOOD  # OFPP_FLOOD标志表示应在所有端口发送数据包，即洪泛

    actions = [parser.OFPActionOutput(out_port)]

    # 下发流表避免下次触发 packet in 事件
    # 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, eth_src=src)
        # verify if we have a valid buffer_id, if yes avoid to send both
        # flow_mod & packet_out
        if msg.buffer_id != ofproto.OFP_NO_BUFFER:
            self.add_flow(datapath, 1, match, actions, msg.buffer_id)
            return
        else:
            self.add_flow(datapath, 1, match, actions)
    data = None
    if msg.buffer_id == ofproto.OFP_NO_BUFFER:
        data = msg.data

    # 发送Packet_out数据包
    out = parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id,
                              in_port=in_port, actions=actions, data=data)
    # 发送流表
    datapath.send_msg(out)

`

a) 代码当中的mac_to_port的作用是什么？
答：
保存mac地址到交换机端口的映射
b) simple_switch和simple_switch_13在dpid的输出上有何不同？
答：
在simple_switch_13.py中为dpid = format(datapath.id, "d").zfill(16)
在simple_switch.py中为dpid = datapath.id
在simple_switch_13.py中使用了zfill() 方法返回指定长度为16的字符串，原字符串右对齐，前面填充0；而simple_switch.py直接输出dpid
c) 相比simple_switch，simple_switch_13增加的switch_feature_handler实现了什么功能？
答：
simple_switch_13交换机可以以特性应答消息来响应特性请求
d) simple_switch_13是如何实现流规则下发的？
答：
在触发packetIn事件后，解析相关数据结构，获取协议信息、获取源端口、包学习，交换机信息，以太网信息等多种信息。如果以太网类型是LLDP类型，则忽略。 如果不是LLDP类型，则获取目的端口和源端口以及交换机id， 然后进行交换机自学习，先学习源地址对应的交换机的入端口， 再查看是否已经学习目的mac地址，如果没有就进行洪泛转发。如果学习过，查看是否有buffer_id，如果有则在添加流时加上buffer_id，向交换机发送数据包和流表。
e) switch_features_handler和_packet_in_handler两个事件在发送流规则的优先级上有何不同？
答：
switch_features_handler的优先级更高
编程实现和ODL实验的一样的硬超时功能。

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 = {}

@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

    # 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, buffer_id=None, hard_timeout=0):
    ofproto = datapath.ofproto
    parser = datapath.ofproto_parser

    inst = [parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS,
                                         actions)]
    if buffer_id:
        mod = parser.OFPFlowMod(datapath=datapath, buffer_id=buffer_id,
                                priority=priority, match=match,
                                instructions=inst, hard_timeout=hard_timeout)
    else:
        mod = parser.OFPFlowMod(datapath=datapath, priority=priority,
                                match=match, instructions=inst, hard_timeout=hard_timeout)
    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]

    if eth.ethertype == ether_types.ETH_TYPE_LLDP:
        # ignore lldp packet
        return
    dst = eth.dst
    src = eth.src

    dpid = format(datapath.id, "d").zfill(16)
    self.mac_to_port.setdefault(dpid, {})

    self.logger.info("packet in %s %s %s %s", dpid, src, dst, in_port)

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

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

    actions = [parser.OFPActionOutput(out_port)]\

    actions_timeout=[]

    # 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, eth_src=src)
        # verify if we have a valid buffer_id, if yes avoid to send both
        # flow_mod & packet_out
        hard_timeout=10
        if msg.buffer_id != ofproto.OFP_NO_BUFFER:
            self.add_flow(datapath, 2, match,actions_timeout, msg.buffer_id,hard_timeout=10)
            self.add_flow(datapath, 1, match, actions, msg.buffer_id)
            return
        else:
            self.add_flow(datapath, 2, match, actions_timeout, hard_timeout=10)
            self.add_flow(datapath, 1, match, actions)
    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)

（三）实验报告
个人总结，包括但不限于实验难度、实验过程遇到的困难及解决办法，个人感想，不少于200字。
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