使用 ryu 控制器在 sdn 交换机中空闲超时后的数据包输入请求

编程问答 2022-04-22

问题描述

我正在使用 Ryu 控制器来设置流的空闲和硬超时。我将空闲超时指定为 10 秒，将硬超时指定为 30 秒。首先，当我在 mininet 上运行 pingall 时，这将通过生成数据包不匹配请求来安装流规则。当超时事件发生时，它将从流表中删除流规则。现在，当我再次在 mininet 上运行 pingall 时，它不会生成数据包不匹配请求。所有数据包都被丢弃。请帮我解决这个问题。 Ryu 应用的代码如下。

# 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,match,actions)

    def add_flow(self,datapath,priority,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,idle_timeout=10,hard_timeout=30,priority=priority,match=match,instructions=inst)
        else:
            mod = parser.OFPFlowMod(datapath=datapath,instructions=inst)
        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 = datapath.id
        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)]

        # 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,msg.buffer_id)
                return
            else:
                self.add_flow(datapath,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)

解决方法

当您发送第一个 pingall 时，数据包将通过 table-miss 流条目发送到控制器。此流条目通过 self.add_flow 安装，因此与所有其他流具有相同的超时。很可能，当您发送第二个 pingall 时，table-miss 流条目已经超时并且不再安装在交换机上，导致交换机丢弃数据包而不是将它们发送到控制器。尝试在没有超时的情况下安装 table-miss 流条目，这应该可以解决问题。

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