一、基本要求

• 建立拓?fù)洌簊udo mn --topo=single,3 --mac --controller=remote,ip=127.0.0.1,port=6633 --switch ovsk,protocols=OpenFlow10
• 連接ryu: ryu-manager gui_topology.py --observe-links

1、通過(guò)Ryu的圖形界面查看網(wǎng)絡(luò)拓?fù)洌?a target="_blank" rel="noopener nofollow">http://192.168.43.209:8080）

2、閱讀Ryu文檔的The First Application一節(jié)，運(yùn)行當(dāng)中的L2Switch，h1 ping h2，在目標(biāo)主機(jī)使用 tcpdump 驗(yàn)證L2Switch，分析L2Switch和POX的Hub模塊有何不同。

• 運(yùn)行L2Switch（ryu-manager L2Switch.py）

• 打開終端：xterm h2 h3；在終端輸入：(tcpdump -nn -i h2-eth0)(tcpdump -nn -i h3-eth0)

• L2Switch和POX的Hub模塊不同：Hub和L2Switch模塊都是洪泛轉(zhuǎn)發(fā)，但L2Switch模塊下發(fā)的流表無(wú)法查看，而Hub模塊下發(fā)的流表可以查看

3、編程修改L2Switch.py，改為L(zhǎng)2032002225.py，使之和POX的Hub模塊變得一致。

代碼

from ryu.base import app_manager
from ryu.ofproto import ofproto_v1_3
from ryu.controller import ofp_event
from ryu.controller.handler import MAIN_DISPATCHER, CONFIG_DISPATCHER
from ryu.controller.handler import set_ev_cls
 
 
class hub(app_manager.RyuApp):
    OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]
 
    def __init__(self, *args, **kwargs):
        super(hub, self).__init__(*args, **kwargs)
 
    @set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER)
    def switch_feathers_handler(self, ev):
        datapath = ev.msg.datapath
        ofproto = datapath.ofproto
        ofp_parser = datapath.ofproto_parser
 
        # install flow table-miss flow entry
        match = ofp_parser.OFPMatch()
        actions = [ofp_parser.OFPActionOutput(ofproto.OFPP_CONTROLLER, ofproto.OFPCML_NO_BUFFER)]
        # 1\OUTPUT PORT, 2\BUFF IN SWITCH?
        self.add_flow(datapath, 0, match, actions)
 
    def add_flow(self, datapath, priority, match, actions):
        # 1\ datapath for the switch, 2\priority for flow entry, 3\match field, 4\action for packet
        ofproto = datapath.ofproto
        ofp_parser = datapath.ofproto_parser
        # install flow
        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):
        msg = ev.msg
        datapath = msg.datapath
        ofproto = datapath.ofproto
        ofp_parser = datapath.ofproto_parser
        in_port = msg.match['in_port']  # get in port of the packet
 
        # add a flow entry for the packet
        match = ofp_parser.OFPMatch()
        actions = [ofp_parser.OFPActionOutput(ofproto.OFPP_FLOOD)]
        self.add_flow(datapath, 1, match, actions)
 
        # to output the current packet. for install rules only output later packets
        out = ofp_parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id, in_port=in_port, actions=actions)
        # buffer id: locate the buffered packet
        datapath.send_msg(out)

• 查看流表（dpctl dump-flows）

二、進(jìn)階要求

1.simple_switch_13.py其代碼的注釋:

# 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.
# 引入數(shù)據(jù)包
from ryu.base import app_manager
from ryu.controller import ofp_event
from ryu.controller.handler import CONFIG_DISPATCHER, MAIN_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 ether_types


class SimpleSwitch13(app_manager.RyuApp): #繼承了ryu.base.app_manager
    OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]  # 定義openflow版本，為1.3

    def __init__(self, *args, **kwargs):
        super(SimpleSwitch13, self).__init__(*args, **kwargs)
        self.mac_to_port = {}  #self.mac_to_port是一個(gè)保存(交換機(jī)id, mac地址)到轉(zhuǎn)發(fā)端口的字典，保存mac地址到端口的一個(gè)映射。

        #開始處理SwitchFeatures事件
　　	#控制器事件（Event)，Event具體見ryu/controller/ofp_event.py，其事件名稱是由接收到的報(bào)文類型來(lái)命名的，名字為Event+報(bào)文類型，例如本例中，控制器收到的是交換機(jī)發(fā)送的FEATURE_REPLY	報(bào)文,所以事件名稱為EventOFPSwitchFeatures。所以本事件其實(shí)就是當(dāng)控制器接收到FEATURE_REPLY報(bào)文觸發(fā)。
    @set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER)
    def switch_features_handler(self, ev):
        datapath = ev.msg.datapath  #datapath存儲(chǔ)交換機(jī)的信息
        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指流表項(xiàng)匹配，這里OFPMatch()指不匹配任何信息
        actions = [parser.OFPActionOutput(ofproto.OFPP_CONTROLLER,
                                          ofproto.OFPCML_NO_BUFFER)] #actions是動(dòng)作，表示匹配成功不緩存數(shù)據(jù)包并發(fā)送給控制器
        self.add_flow(datapath, 0, match, actions) #add_flow是添加流表項(xiàng)的函數(shù),我們可以從add_flow的函數(shù)中看到其調(diào)用了send_msg(mod),因此本函數(shù)的目的即為下發(fā)流表。
          # add_flow()增加流表項(xiàng)
          # priority：此規(guī)則的優(yōu)先權(quán)
          # match：此規(guī)則的 Match 條件
          # actions：動(dòng)作
	  # 參數(shù)有datapath，優(yōu)先級(jí)，匹配項(xiàng)，動(dòng)作，buffer_id；
          # 此流表項(xiàng)匹配成功后應(yīng)立即執(zhí)行所規(guī)定的動(dòng)作。如果此函數(shù)參數(shù)有buffer_id(就是交換機(jī)發(fā)送來(lái)的數(shù)據(jù)包有buffer_id，即交換機(jī)有緩存），那發(fā)送的Flow_Mod報(bào)文就帶上buffer_id，若沒(méi)有buffer_id，buffer_id就是None。最后，發(fā)出Flow_Mod報(bào)文
    def add_flow(self, datapath, priority, match, actions, buffer_id=None):
          # 獲取交換機(jī)信息
        ofproto = datapath.ofproto
        parser = datapath.ofproto_parser
          # 對(duì)action進(jìn)行包裝
        inst = [parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS,
                                             actions)]
          # 判斷是否存在buffer_id，并生成mod對(duì)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)
           # 發(fā)送出去
        datapath.send_msg(mod)
        
	#處理處理PacketIn事件，說(shuō)明控制器在MAIN_DISPATCHER狀態(tài)并且觸發(fā)Packet_In事件時(shí)調(diào)用_packet_in_handler函數(shù)
    @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: #傳輸出錯(cuò)，打印debug信息
            self.logger.debug("packet truncated: only %s of %s bytes",
                              ev.msg.msg_len, ev.msg.total_len)
        #開始解析數(shù)據(jù)結(jié)構(gòu)
        #這里是從接收到的Packet_In報(bào)文中取出各種信息，如果報(bào)文是lldp報(bào)文，忽略它。隨后用此dpid（交換機(jī)id)初始化mac_to_port，并在日志打印此Packet_In的基本信息。       
        msg = ev.msg   # ev.msg 是代表packet_in data structure對(duì)象
        datapath = msg.datapath
        ofproto = datapath.ofproto 
        # dp. ofproto 和 dp.ofproto_parser 是代表 Ryu 和交換機(jī)談判的 OpenFlow 協(xié)議的對(duì)象
        # dp.ofproto and dp.ofproto_parser are objects that represent the OpenFlow protocol that Ryu and the switch negotiated
        parser = datapath.ofproto_parser
        in_port = msg.match['in_port']    # 獲取源端口

        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        # 獲取目的端口
        src = eth.src        # 獲取源端口

        dpid = format(datapath.id, "d").zfill(16)
        self.mac_to_port.setdefault(dpid, {}) 
         
        # 學(xué)習(xí)包的源地址，和交換機(jī)上的入端口綁定
        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 #交換機(jī)自學(xué)習(xí)，取來(lái)往數(shù)據(jù)包的交換機(jī)id、源mac和入端口綁定來(lái)構(gòu)造表。
        
        # 查看是否已經(jīng)學(xué)習(xí)過(guò)該目的mac地址
        if dst in self.mac_to_port[dpid]: #若在表中找到出端口信息，指示出端口（存放mac地址到交換機(jī)端口的映射。）
            out_port = self.mac_to_port[dpid][dst]
        else:
            out_port = ofproto.OFPP_FLOOD  # OFPP_FLOOD標(biāo)志表示應(yīng)在所有端口發(fā)送數(shù)據(jù)包，即洪泛

        actions = [parser.OFPActionOutput(out_port)]

        # 下發(fā)流表避免下次觸發(fā) 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:#有buffer_id，帶上buffer_id，然后只發(fā)送Flow_mod報(bào)文，因?yàn)榻粨Q機(jī)已經(jīng)有緩存數(shù)據(jù)包，就不需要發(fā)送packet_out報(bào)文
                self.add_flow(datapath, 1, match, actions, msg.buffer_id)#add_flow函數(shù)內(nèi)部就已發(fā)送了Flow_mod報(bào)文。，后面不用send_msg()
                return
            else:
                self.add_flow(datapath, 1, match, actions)#若沒(méi)有buffer_id，發(fā)送的Flow_Mod報(bào)文就無(wú)需要帶上buffer_id，但是下一步要再發(fā)送一個(gè)Packet_out報(bào)文帶上原數(shù)據(jù)包信息。
        data = None
        if msg.buffer_id == ofproto.OFP_NO_BUFFER:
            data = msg.data
	#發(fā)送Packet_out數(shù)據(jù)包 帶上交換機(jī)發(fā)來(lái)的數(shù)據(jù)包的信息
        out = parser.OFPPacketOut(datapath=datapath, buffer_id=msg.buffer_id,
                                  in_port=in_port, actions=actions, data=data)
        # 發(fā)送流表
        datapath.send_msg(out)

a)代碼當(dāng)中的mac_to_port的作用

存放mac地址到交換機(jī)端口的映射。

b)simple_switch和simple_switch_13在dpid的輸出上不同:

simple_switch_13會(huì)把dpid用前置0填充到16位，而simple_switch不會(huì)填充而是直接輸出。

c)相比simple_switch，simple_switch_13增加的switch_feature_handler實(shí)現(xiàn)的功能:

實(shí)現(xiàn)了交換機(jī)以特性應(yīng)答消息來(lái)響應(yīng)特性請(qǐng)求的功能。

d)simple_switch_13實(shí)現(xiàn)流規(guī)則下發(fā)的方法：

在觸發(fā)Packet_In事件后，會(huì)先解析相關(guān)數(shù)據(jù)結(jié)構(gòu)，獲取協(xié)議信息、獲取源端口、包學(xué)習(xí)，交換機(jī)信息，以太網(wǎng)信息等。

如果以太網(wǎng)類型是LLDP類型，則忽略。

如果以太網(wǎng)類型不是LLDP類型，則獲取目的端口、源端口還有交換機(jī)id。然后進(jìn)行交換機(jī)自學(xué)習(xí)，先學(xué)習(xí)源地址對(duì)應(yīng)的交換機(jī)的入端口，再查看是否已經(jīng)學(xué)習(xí)目的mac地址，如果沒(méi)有就洪泛轉(zhuǎn)發(fā)。

如果學(xué)習(xí)過(guò)，則查看是否有buffer_id，如果有則在添加流時(shí)加上buffer_id，向交換機(jī)發(fā)送數(shù)據(jù)包和流表。

e)switch_features_handler和_packet_in_handler兩個(gè)事件在發(fā)送流規(guī)則的優(yōu)先級(jí)上的不同：

switch_features_handler優(yōu)先級(jí)比_packet_in_handler要高。

2、編程實(shí)現(xiàn)和ODL實(shí)驗(yàn)的一樣的硬超時(shí)功能。

代碼032002225timeout.py(ryu-manager 032002225timeout.py調(diào)用)

# 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
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 ether_types


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=5
            if msg.buffer_id != ofproto.OFP_NO_BUFFER:
                self.add_flow(datapath, 2, match,actions_timeout, msg.buffer_id,hard_timeout)
                self.add_flow(datapath, 1, match, actions, msg.buffer_id)
                return
            else:
                self.add_flow(datapath, 2, match, actions_timeout, hard_timeout=5)
                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)

• h1 ping h3，hard_timeout = 5

三、個(gè)人總結(jié)

基礎(chǔ)部分我感覺(jué)還是挺簡(jiǎn)單的（相比較與實(shí)驗(yàn)四和實(shí)驗(yàn)五來(lái)說(shuō)）
但是在實(shí)驗(yàn)過(guò)程中，“編程修改L2Switch.py，改為L(zhǎng)2032002225.py，使之和POX的Hub模塊變得一致”這一步的時(shí)候，總是ping不同。
后來(lái)詢問(wèn)了其他同學(xué)要把構(gòu)建拓?fù)涞膕udo mn --topo=single,3 --mac --controller=remote,ip=127.0.0.1,port=6633 --switch ovsk,protocols=OpenFlow10
中的“,protocols=OpenFlow10”語(yǔ)句刪除。
進(jìn)階部分我感覺(jué)難度挺高的，是在同學(xué)的幫助下才把注釋理解完并了解了各個(gè)文件的不同。
編寫“編程實(shí)現(xiàn)和ODL實(shí)驗(yàn)的一樣的硬超時(shí)功能”后，剛開始無(wú)法實(shí)現(xiàn)硬中斷，后來(lái)修改了各命令的順序解決了這個(gè)問(wèn)題。