實驗6：開源控制器實踐——RYU

一、基礎要求

L2Switch是無法查看流表的，但是POX的Hub是可以查看流表的
L2Switch下查看流表：

pox的hub下查看流表：
./pox.py log.level --DEBUG forwarding.hub
修改之后的L2212006208.py代碼：

from ryu.base import app_manager
from ryu.controller import ofp_event
from ryu.controller.handler import MAIN_DISPATCHER
from ryu.controller.handler import CONFIG_DISPATCHER, MAIN_DISPATCHER
from ryu.controller.handler import set_ev_cls
from ryu.ofproto import ofproto_v1_3

class L2Switch(app_manager.RyuApp):
    OFP_VERSIONS = [ofproto_v1_3.OFP_VERSION]

    def __init__(self, *args, **kwargs):
        super(L2Switch, self).__init__(*args, **kwargs)

    @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):
        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)
        else:
            mod = 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
        dp = msg.datapath
        ofp = dp.ofproto
        ofp_parser = dp.ofproto_parser
        in_port = msg.match['in_port']

        actions = [ofp_parser.OFPActionOutput(ofp.OFPP_FLOOD)]

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

        out = ofp_parser.OFPPacketOut(
            datapath=dp, buffer_id=msg.buffer_id, in_port=in_port,
            actions=actions, data = data)
        dp.send_msg(out)

二、進階要求

回答問題：
a)代碼當中的mac_to_port的作用是什么？
mac地址到交換機端口的一個映射
b) simple_switch和simple_switch_13在dpid的輸出上有何不同？

simple_switch：
  dpid = datapath.id
        self.mac_to_port.setdefault(dpid, {})

直接輸出dpid

simple_switch_13：
  dpid = format(datapath.id, "d").zfill(16)
        self.mac_to_port.setdefault(dpid, {})

用0在dpid前填充，直到dpid總長度達到16位。
c) 相比simple_switch，simple_switch_13增加的switch_feature_handler實現了什么功能？
實現了交換機以特性應答消息去響應特性請求這一功能
d) simple_switch_13是如何實現流規則下發的？
當接收到packetin事件后，首先獲取交換機信息，包學習，協議信息，以太網信息等。如果以太網類型是LLDP類型，就不進行任何處理。若不是，則獲取源端口、目的端口和交換機id，先學習源地址對應的交換機入端口，再查看是否學習了目的mac地址，若沒有則進行洪泛轉發，但若學習過該mac地址，則查看是否有buffer_id，若有，先在添加流動作時加上buffer_id，再向交換機發送流表。
e) switch_features_handler和_packet_in_handler兩個事件在發送流規則的優先級上有何不同？
switch_features_handler下發流表的優先級高于_packet_in_handler

代碼注釋

# 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.

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] #定義openflow的版本為1.3

    def __init__(self, *args, **kwargs):
        super(SimpleSwitch13, self).__init__(*args, **kwargs)
        self.mac_to_port = {}

    @set_ev_cls(ofp_event.EventOFPSwitchFeatures, CONFIG_DISPATCHER) # 處理EventOFPSwitchFeatures事件
    def switch_features_handler(self, ev):
        datapath = ev.msg.datapath #ev.msg 是用來存儲對應事件的 OpenFlow 消息類別實體
        ofproto = datapath.ofproto # ofproto表示使用的OpenFlow版本所對應的ryu.ofproto.ofproto_v1_3
        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): #添加流表
        ofproto = datapath.ofproto
        parser = datapath.ofproto_parser #獲取交換機信息

        inst = [parser.OFPInstructionActions(ofproto.OFPIT_APPLY_ACTIONS,
                                             actions)]  #包裝action
        
        #判斷是否有buffer_id,生成相應的mod對象
        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)
        #發送mod
        datapath.send_msg(mod)

# 處理 packet in 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)
        # 獲取包信息，交換機信息，協議等等
        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# 獲取源端口，目的端口

        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) #dpid是交換機的id，src是數據包的源mac地址，in_port是交換機接受到包的端口

        # learn a mac address to avoid FLOOD next time.
        self.mac_to_port[dpid][src] = in_port  # 查看是否已經學習過該目的mac地址,如果已經學習到，則向交換機下發流表,并讓交換機向相應端口轉發包
        if dst in self.mac_to_port[dpid]:
            out_port = self.mac_to_port[dpid][dst]
        else:  #沒有就進行洪泛
            out_port = ofproto.OFPP_FLOOD

        actions = [parser.OFPActionOutput(out_port)]
	
	# 下發流表處理后續包，不再觸發PACKETIN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
            #buffer_id不為None，控制器只需下發流表的命令，交換機增加了流表項后，位于緩沖區的數據包，會自動轉發出去。
            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                                          #buffer_id為None，則控制器不僅要更改交換機的流表項，還要把數據包的信息傳給交換機，讓交換機把數據包轉發出去。
        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)   #發送流表

編程實現和ODL實驗的一樣的硬超時功能。

# 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)

#添加流表函數（執行add_flow()方法以發送flow mod消息）這里加了一個hardtime參數
    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 #設置硬超時時間為10s
#buffer_id不為None，控制器只需下發流表的命令同時實現硬超時功能，交換機增加了流表項后，位于緩沖區的數據包，會自動轉發出去。
#此條中帶有硬超時功能的優先級為2
            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
#buffer_id為None，則控制器不僅要更改交換機的流表項，還要把數據包的信息傳給交換機，讓交換機把數據包轉發出去。
#此條中帶有硬超時功能的優先級為2
            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)

個人總結
本次實驗主要是通過閱讀ryu的相關文章以及查看了解ryu的代碼，來了解ryu控制器的工作原理，能夠獨立部署ryu控制器，理解ryu控制器再軟件定義網絡中的一些原理，并且區分ryu和pox的Hub模板之間的區別，在這次實驗中，讓我體會到了python文件縮進的重要性，只要一行的縮進不對就會導致代碼不能正確運行。在進階實驗中，了解了代碼的含義并且對代碼進行了注釋，有了更加深刻的印象，并且實現了硬超時的功能。
問題一：

解決辦法：需要將openflow的版本改成1.3，并且是要先運行ryu,再創建拓撲才是可以

問題二：

解決辦法：因為縮進的問題導致運行錯誤

發表于 2022-11-04 17:11 青青子衿l 閱讀(226) 評論(0) 收藏舉報

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實驗6：開源控制器實踐——RYU

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