网络工程 - 在 OpenFlow ryu 交换机中解码数据包 - 吾爱随笔录

在 OpenFlow ryu 交换机中解码数据包

网络工程包分析 linux 开放流迷你网

2021-07-09 01:31:40

我正在尝试检查一个简单的 OpenFlow ryu 交换机，并从中获取目标地址和源地址。

我正在使用迷你网。

例如对于下一个命令：

h1 python -m SimpleHTTPServer 80 &
h2 wget -O - h3

目标是 h3，源是 h2。

这是我正在使用的简单开关（我正在使用 Ryu）：

    # 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.

import logging
import struct
from ryu.base import app_manager
from ryu.controller import mac_to_port
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_str




class SimpleSwitch(app_manager.RyuApp):
    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, actions):
        ofproto = datapath.ofproto

        wildcards = ofproto_v1_0.OFPFW_ALL
        wildcards &= ~ofproto_v1_0.OFPFW_IN_PORT
        wildcards &= ~ofproto_v1_0.OFPFW_DL_DST

        match = datapath.ofproto_parser.OFPMatch(
            wildcards, in_port, 0, dst,
            0, 0, 0, 0, 0, 0, 0, 0, 0)

        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)
        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

        dst, src, _eth_type = struct.unpack_from('!6s6sH', buffer(msg.data), 0)

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

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

        actions = [datapath.ofproto_parser.OFPActionOutput(out_port)]

        # install a flow to avoid packet_in next time
        if out_port != ofproto.OFPP_FLOOD:
            self.add_flow(datapath, msg.in_port, dst, actions)

        out = datapath.ofproto_parser.OFPPacketOut(
            datapath=datapath, buffer_id=msg.buffer_id, in_port=msg.in_port,
            actions=actions)
        datapath.send_msg(out)

    @set_ev_cls(ofp_event.EventOFPPortStatus, MAIN_DISPATCHER)
    def _port_status_handler(self, ev):
        msg = ev.msg
        reason = msg.reason
        port_no = msg.desc.port_no

        ofproto = msg.datapath.ofproto
        if reason == ofproto.OFPPR_ADD:
            self.logger.info("port added %s", port_no)
        elif reason == ofproto.OFPPR_DELETE:
            self.logger.info("port deleted %s", port_no)
        elif reason == ofproto.OFPPR_MODIFY:
            self.logger.info("port modified %s", port_no)
        else:
            self.logger.info("Illeagal port state %s %s", port_no, reason)

我试图打印 haddr_to_str(src)、haddr_to_str(dst) 并得到 00:00:00:00:00:03 和 ff:ff:ff:ff:ff:ff 这不是我所期望的。我想得到 2 作为源，3 作为目标。

1个回答

抱歉，我花了一段时间才弄明白mininet和 OpenFlow ryu 控制器，但我终于明白了......

我试图打印 haddr_to_str(src)、haddr_to_str(dst) 并得到 00:00:00:00:00:03 和 ff:ff:ff:ff:ff:ff 这不是我所期望的。我想得到 2 作为源，3 作为目标。

简而言之，您正在正确解码目标 mac 地址……但是，IP 必须通过 ARP 才能解析 mac 地址，这就是您看到的原因ff:ff:ff:ff:ff:ff……那些只是ryu 控制器中的 ARP 帧。

这是一个完整的控制器，可以工作和解码到 IPv4 层......

更新 ryu 开关包解码器

您一直在解码 raw structs，但使用ryu Packet 库而不是解包原始数据包要容易得多struct。这是我非常快速的替换_packet_in_handler()，它只是打印出源和目标 mac 地址，以及上层协议......

from ryu.lib.packet import packet, ethernet, arp, ipv4
import array

@set_ev_cls(ofp_event.EventOFPPacketIn, MAIN_DISPATCHER)
def _packet_in_handler(self, ev):

    ### Mike Pennington's logging modifications
    ## Set up to receive the ethernet src / dst addresses
    pkt = packet.Packet(array.array('B', ev.msg.data))
    eth_pkt = pkt.get_protocol(ethernet.ethernet)
    arp_pkt = pkt.get_protocol(arp.arp)
    ip4_pkt = pkt.get_protocol(ipv4.ipv4)
    if arp_pkt:
        pak = arp_pkt
    elif ip4_pkt:
        pak = ip4_pkt
    else:
        pak = eth_pkt
    self.logger.info('  _packet_in_handler: src_mac -> %s' % eth_pkt.src)
    self.logger.info('  _packet_in_handler: dst_mac -> %s' % eth_pkt.dst)
    self.logger.info('  _packet_in_handler: %s' % pak)
    self.logger.info('  ------')
    src = eth_pkt.src  # Set up the src and dst variables so you can use them
    dst = eth_pkt.dst
    ## Mike Pennington's modifications end here

    
    msg = ev.msg
    datapath = msg.datapath
    ofproto = datapath.ofproto

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

    # 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

    actions = [datapath.ofproto_parser.OFPActionOutput(out_port)]

    # install a flow to avoid packet_in next time
    if out_port != ofproto.OFPP_FLOOD:
        self.add_flow(datapath, msg.in_port, dst, actions)

    out = datapath.ofproto_parser.OFPPacketOut(
        datapath=datapath, buffer_id=msg.buffer_id, in_port=msg.in_port,
        actions=actions)
    datapath.send_msg(out)

现在，无论何时发送以太网数据包，您都会在 mininet 会话中看到它...

  _packet_in_handler: src_mac -> 00:00:00:00:00:03
  _packet_in_handler: dst_mac -> 33:33:00:00:00:02
  _packet_in_handler: ethernet(dst='33:33:00:00:00:02',ethertype=34525,src='00:00:00:00:00:03')
  ------

ARP 数据包看起来像这样...

  _packet_in_handler: src_mac -> 00:00:00:00:00:01
  _packet_in_handler: dst_mac -> ff:ff:ff:ff:ff:ff
  _packet_in_handler: arp(dst_ip='10.0.0.2',dst_mac='00:00:00:00:00:00',hlen=6,hwtype=1,opcode=1,plen=4,proto=2048,src_ip='10.0.0.1',src_mac='00:00:00:00:00:01')
  ------

演示

假设我将上面修改后的代码（包括源代码的其他部分）保存为ne_question.py.

首先，我在mininet 中设置了ryu 控制器：

root@mininet-vm:/home/mininet# ryu-manager ne_question.py &
                 [1] 14073
loading app ne_question.py
loading app ryu.controller.ofp_handler
instantiating app ryu.controller.ofp_handler of OFPHandler
instantiating app ne_question.py of SimpleSwitch

root@mininet-vm:/home/mininet#

接下来我构建交换机拓扑，正如您在评论中提到的

root@mininet-vm:/home/mininet# mn --topo single,3 --mac --switch ovsk --controller remote
*** Creating network
*** Adding controller
*** Adding hosts:
h1 h2 h3
*** Adding switches:
s1
*** Adding links:
(h1, s1) (h2, s1) (h3, s1)
*** Configuring hosts
h1 h2 h3
*** Starting controller
*** Starting 1 switches
s1
*** Starting CLI:
mininet>   _packet_in_handler: src_mac -> 00:00:00:00:00:02
  _packet_in_handler: dst_mac -> 33:33:00:00:00:02
  _packet_in_handler: ethernet(dst='33:33:00:00:00:02',ethertype=34525,src='00:00:00:00:00:02')
  ------
  _packet_in_handler: src_mac -> 00:00:00:00:00:01
  _packet_in_handler: dst_mac -> 33:33:00:00:00:02
  _packet_in_handler: ethernet(dst='33:33:00:00:00:02',ethertype=34525,src='00:00:00:00:00:01')
  ------
  _packet_in_handler: src_mac -> 00:00:00:00:00:03
  _packet_in_handler: dst_mac -> 33:33:00:00:00:02
  _packet_in_handler: ethernet(dst='33:33:00:00:00:02',ethertype=34525,src='00:00:00:00:00:03')
  ------

最后，我运行 web 服务器，并尝试拉一个页面...注意发送 ARP 来解析 http GET 的目标地址。ARP 的目的地址是ff:ff:ff:ff:ff:ff. 顺便说一句，如果您更改wget为h2 wget h1，一切正常...

mininet> h1 python -m SimpleHTTPServer 80 &
mininet> h2 wget -O - h1
--2014-03-28 04:22:25--  http://10.0.0.1/
Connecting to 10.0.0.1:80...   _packet_in_handler: src_mac -> 00:00:00:00:00:02
  _packet_in_handler: dst_mac -> ff:ff:ff:ff:ff:ff
  _packet_in_handler: arp(dst_ip='10.0.0.1',dst_mac='00:00:00:00:00:00',hlen=6,hwtype=1,opcode=1,plen=4,proto=2048,src_ip='10.0.0.2',src_mac='00:00:00:00:00:02')
  ------
--2014-03-28 04:00:58--  http://10.0.0.1/
Connecting to 10.0.0.1:80...   _packet_in_handler: src_mac -> 00:00:00:00:00:02
  _packet_in_handler: dst_mac -> 00:00:00:00:00:01
  _packet_in_handler: ipv4(csum=33886,dst='10.0.0.1',flags=2,header_length=5,identification=41563,offset=0,option=None,proto=6,src='10.0.0.2',tos=0,total_length=60,ttl=64,version=4)
  ------
  _packet_in_handler: src_mac -> 00:00:00:00:00:01
  _packet_in_handler: dst_mac -> 00:00:00:00:00:02
  _packet_in_handler: ipv4(csum=9914,dst='10.0.0.2',flags=2,header_length=5,identification=0,offset=0,option=None,proto=6,src='10.0.0.1',tos=0,total_length=60,ttl=64,version=4)
  ------
connected.
HTTP request sent, awaiting response...   _packet_in_handler: src_mac -> 00:00:00:00:00:02
  _packet_in_handler: dst_mac -> 00:00:00:00:00:01
  _packet_in_handler: ipv4(csum=33893,dst='10.0.0.1',flags=2,header_length=5,identification=41564,offset=0,option=None,proto=6,src='10.0.0.2',tos=0,total_length=52,ttl=64,version=4)
  ------
  _packet_in_handler: src_mac -> 00:00:00:00:00:02
  _packet_in_handler: dst_mac -> 00:00:00:00:00:01
  _packet_in_handler: ipv4(csum=33784,dst='10.0.0.1',flags=2,header_length=5,identification=41565,offset=0,option=None,proto=6,src='10.0.0.2',tos=0,total_length=160,ttl=64,version=4)
  ------
  _packet_in_handler: src_mac -> 00:00:00:00:00:01
  _packet_in_handler: dst_mac -> 00:00:00:00:00:02
  _packet_in_handler: ipv4(csum=61034,dst='10.0.0.2',flags=2,header_length=5,identification=14423,offset=0,option=None,proto=6,src='10.0.0.1',tos=0,total_length=52,ttl=64,version=4)
  ------
  _packet_in_handler: src_mac -> 00:00:00:00:00:01
  _packet_in_handler: dst_mac -> 00:00:00:00:00:02
  _packet_in_handler: ipv4(csum=61016,dst='10.0.0.2',flags=2,header_length=5,identification=14424,offset=0,option=None,proto=6,src='10.0.0.1',tos=0,total_length=69,ttl=64,version=4)
  ------
  _packet_in_handler: src_mac -> 00:00:00:00:00:01
  _packet_in_handler: dst_mac -> 00:00:00:00:00:02
  _packet_in_handler: ipv4(csum=60037,dst='10.0.0.2',flags=2,header_length=5,identification=14425,offset=0,option=None,proto=6,src='10.0.0.1',tos=0,total_length=1047,ttl=64,version=4)
  ------
200 OK
Length: 858 [text/html]
Saving to: `STDOUT'
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html>
<title>Directory listing for /</title>
<body>
<h2>Directory listing for /</h2>
<hr>
<ul>
<li><a href=".bash_history">.bash_history</a>
<li><a href=".bash_logout">.bash_logout</a>
<li><a href=".bashrc">.bashrc</a>
<li><a href=".cache/">.cache/</a>
<li><a href=".gitconfig">.gitconfig</a>
<li><a href=".profile">.profile</a>
<li><a href=".rnd">.rnd</a>
<li><a href=".wireshark/">.wireshark/</a>
<li><a href="install-mininet-vm.sh">install-mininet-vm.sh</a>
<li><a href="mininet/">mininet/</a>
<li><a href="ne_question.py">ne_question.py</a>
<li><a href="ne_question.pyc">ne_question.pyc</a>
<li><a href="of-dissector/">of-dissector/</a>
<li><a href="oflops/">oflops/</a>
<li><a href="oftest/">oftest/</a>
<li><a href="openflow/">openflow/</a>
<li><a href="pox/">pox/</a>
</ul>
<hr>
</body>
</html>

     0K                                                       100%  161M=0s

2014-03-28 04:00:58 (161 MB/s) - written to stdout [858/858]

  _packet_in_handler: src_mac -> 00:00:00:00:00:02
mininet>   _packet_in_handler: dst_mac -> 00:00:00:00:00:01
  _packet_in_handler: ipv4(csum=33891,dst='10.0.0.1',flags=2,header_length=5,identification=41566,offset=0,option=None,proto=6,src='10.0.0.2',tos=0,total_length=52,ttl=64,version=4)
  ------
  _packet_in_handler: src_mac -> 00:00:00:00:00:02
  _packet_in_handler: dst_mac -> 00:00:00:00:00:01
  _packet_in_handler: ipv4(csum=33890,dst='10.0.0.1',flags=2,header_length=5,identification=41567,offset=0,option=None,proto=6,src='10.0.0.2',tos=0,total_length=52,ttl=64,version=4)
  ------
  _packet_in_handler: src_mac -> 00:00:00:00:00:02
  _packet_in_handler: dst_mac -> 00:00:00:00:00:01
  _packet_in_handler: ipv4(csum=33889,dst='10.0.0.1',flags=2,header_length=5,identification=41568,offset=0,option=None,proto=6,src='10.0.0.2',tos=0,total_length=52,ttl=64,version=4)
  ------
  _packet_in_handler: src_mac -> 00:00:00:00:00:01
  _packet_in_handler: dst_mac -> 00:00:00:00:00:02
  _packet_in_handler: ipv4(csum=9922,dst='10.0.0.2',flags=2,header_length=5,identification=0,offset=0,option=None,proto=6,src='10.0.0.1',tos=0,total_length=52,ttl=64,version=4)
  ------

mininet>
mininet>

其它你可能感兴趣的问题

上一篇什么是 IFL IFD 和 IFA 下一篇非管理型交换机对 RSTP 环的影响？