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追踪openvswitch对特定数据报文的流表匹配与处理结果的实例

时间:2018-11-09 12:13:03      阅读:30      评论:0      收藏:0      [点我收藏+]

标签:generate   hand   dump   关键字   ttl   rom   就是   put   文件中   

SDN环境中,每一个openvswitch的datapath实例中都会有大量的流表项,无论是使用各种关键字的grep手段或者是其他方法来确认是否由控制器下发了预期正确流表项,还是看关于特定数据包的匹配与最终action都是一件非常繁琐和头疼的事情。使用ovs-appctl工具结合linux自带的tcpdump抓包工具就可以很轻松直观的最终流表匹配情况,来完成自己繁琐的查找工作,还能避免自己的判断的错误。

?? 主要步骤如下:
? ? 1、确认你需要跟踪的数据包的各项参数;

? ? 2、将其转化成openflow的match域的描述;

? ? 3、使用openvswitch提供的ofproto/trace功能跟踪流表匹配情况;

如何获取包特征参数?
? ? 可以找到自己需要验证的虚拟机,在其上发出需要验证的协议数据包,在物理计算节点上找到该虚拟机的后端虚拟网卡,在该虚拟网卡上使用tcpdump抓包,也可以从已有的抓包文件中获取,当然,也可以完全由自己指定openflow match域的内容。比如我读一下事先抓好的数据包。

[[email protected] ~]# tcpdump -ennvv -r /home/vnet31.0.pcap 

<code?class="language-plain">reading?from?file?/home/vnet31.0.pcap,?link-type?EN10MB?(Ethernet)??
10:25:17.693773?fa:16:3e:8c:eb:5b?>?fa:16:3e:a5:15:f3,?ethertype?IPv4?(0x0800),?length?74:?(tos?0x0,?ttl?128,?id?8060,?offset?0,?flags?[none],?proto?ICMP?(1),?length?60)??
????20.20.20.104?>?20.20.20.101:?ICMP?echo?request,?id?1,?seq?40197,?length?40</code>??

转换成openflow的描述就是:

dl_src=fa:16:3e:8c:eb:5b,dl_dst=fa:16:3e:a5:15:f3,ip,nw_src=20.20.20.104,nw_dst=20.20.20.101,nw_proto=1

由于该虚拟网卡连接openvswitch的ofport 是37,所以要加上?in_port=37,完整的就如下所示:

in_port=37,dl_src=fa:16:3e:8c:eb:5b,dl_dst=fa:16:3e:a5:15:f3,ip,nw_src=20.20.20.104,nw_dst=20.20.20.101,nw_proto=1

确定了数据包的openflow的特征描述,就可以使用ovs-appctl提供的ofproto/trace功能来跟踪啦,命令如下:

[[email protected] ~]# ovs-appctl ofproto/trace dvs2_dp in_port=37,dl_src=fa:16:3e:8c:eb:5b,dl_dst=fa:16:3e:a5:15:f3,ip,nw_src=20.20.20.104,nw_dst=20.20.20.101,nw_proto=1 -generat

其中dvs2_dp是我实测环境中的bridge名称,-generate的意思是构造该数据报文,此时是确实有一个该报文通过ovs被处理了的。最终跟踪的效果下:

[[email protected] ~]# ovs-appctl ofproto/trace dvs2_dp in_port=37,dl_src=fa:16:3e:8c:eb:5b,dl_dst=fa:16:3e:a5:15:f3,ip,nw_src=20.20.20.104,nw_dst=20.20.20.101,nw_proto=1 -generate

Bridge: dvs2_dp
Flow: icmp,metadata=0,in_port=37,vlan_tci=0x0000,dl_src=fa:16:3e:8c:eb:5b,dl_dst=fa:16:3e:a5:15:f3,nw_src=20.20.20.104,nw_dst=20.20.20.101,nw_tos=0,nw_ecn=0,nw_ttl=0,icmp_type=0,icmp_code=0
Rule: table=0 cookie=0xd4 priority=0
OpenFlow actions=goto_table:1

        Resubmitted flow: unchanged
        Resubmitted regs: reg0=0x0 reg1=0x0 reg2=0x0 reg3=0x0 reg4=0x0 reg5=0x0 reg6=0x0 reg7=0x0
        Resubmitted  odp: drop
        Resubmitted megaflow: recirc_id=0,skb_priority=0,icmp,in_port=37,dl_src=fa:16:3e:8c:eb:5b,dl_dst=fa:16:3e:a5:15:f3,nw_src=20.20.20.104,nw_dst=20.20.20.101,nw_frag=no

        Rule: table=1 cookie=0x616 priority=221,in_port=37
        OpenFlow actions=write_metadata:0x3000009c4,goto_table:4

                Resubmitted flow: icmp,metadata=0x3000009c4,in_port=37,vlan_tci=0x0000,dl_src=fa:16:3e:8c:eb:5b,dl_dst=fa:16:3e:a5:15:f3,nw_src=20.20.20.104,nw_dst=20.20.20.101,nw_tos=0,nw_ecn=0,nw_ttl=0,icmp_type=0,icmp_code=0
                Resubmitted regs: reg0=0x0 reg1=0x0 reg2=0x0 reg3=0x0 reg4=0x0 reg5=0x0 reg6=0x0 reg7=0x0
                Resubmitted  odp: drop
                Resubmitted megaflow: recirc_id=0,skb_priority=0,icmp,in_port=37,dl_src=fa:16:3e:8c:eb:5b,dl_dst=fa:16:3e:a5:15:f3,nw_src=20.20.20.104,nw_dst=20.20.20.101,nw_frag=no

                Rule: table=4 cookie=0x617 priority=161,dl_src=fa:16:3e:8c:eb:5b
                OpenFlow actions=write_metadata:0x3000009c4,goto_table:5

                        Resubmitted flow: unchanged
                        Resubmitted regs: reg0=0x0 reg1=0x0 reg2=0x0 reg3=0x0 reg4=0x0 reg5=0x0 reg6=0x0 reg7=0x0
                        Resubmitted  odp: drop
                        Resubmitted  megaflow:
     recirc_id=0,skb_priority=0,icmp,in_port=37,dl_src=fa:16:3e:8c:eb:5b,dl_dst=fa:16:3e:a5:15:f3,nw_src=20.20.20.104,nw_dst=20.20.20.101,nw_frag=no

                        Rule: table=5 cookie=0xd9 priority=0
                        OpenFlow actions=goto_table:6

                                Resubmitted flow: unchanged
                                Resubmitted regs: reg0=0x0 reg1=0x0 reg2=0x0 reg3=0x0 reg4=0x0 reg5=0x0 reg6=0x0 reg7=0x0
                                Resubmitted  odp: drop
                                Resubmitted megaflow: recirc_id=0,skb_priority=0,icmp,metadata=0/0xffffff,in_port=37,dl_src=fa:16:3e:8c:eb:5b,dl_dst=fa:16:3e:a5:15:f3,nw_src=20.20.20.104,nw_dst=20.20.20.101,nw_frag=no

                                Rule: table=6 cookie=0x5e8 priority=102,metadata=0x9c4/0xffffff,dl_dst=fa:16:3e:a5:15:f3
                                OpenFlow actions=write_actions(set_field:0x9c4->tun_id,output:12)

Final flow: icmp,tun_id=0x9c4,metadata=0x3000009c4,in_port=37,vlan_tci=0x0000,dl_src=fa:16:3e:8c:eb:5b,dl_dst=fa:16:3e:a5:15:f3,nw_src=20.20.20.104,nw_dst=20.20.20.101,nw_tos=0,nw_ecn=0,nw_ttl=0,icmp_type=0,icmp_code=0
Megaflow: recirc_id=0,skb_priority=0,icmp,tun_id=0,metadata=0/0xffffff,in_port=37,dl_src=fa:16:3e:8c:eb:5b,dl_dst=fa:16:3e:a5:15:f3,nw_src=20.20.20.104,nw_dst=20.20.20.101,nw_ecn=0,nw_frag=no
Datapath actions: set(tunnel(tun_id=0x9c4,src=172.47.205.45,dst=172.47.205.46,tos=0x0,ttl=64,flags(df,key))),11

上面的例子是最终数据包被打上了tun_id并从隧道端口被转发的跟踪,下面再举一个table miss被丢弃的例子:

[[email protected] ~]# ovs-appctl ofproto/trace sdn_dvs_dp in_port=127,dl_src=fa:16:3e:a5:85:78,dl_dst=00:d0:d0:1c:3d:2d,ip,nw_src=192.168.150.2,nw_dst=10.47.159.89,nw_proto=1 -generate
Bridge: sdn_dvs_dp
Flow: icmp,metadata=0,in_port=127,vlan_tci=0x0000,dl_src=fa:16:3e:a5:85:78,dl_dst=00:d0:d0:1c:3d:2d,nw_src=192.168.150.2,nw_dst=10.47.159.89,nw_tos=0,nw_ecn=0,nw_ttl=0,icmp_type=0,icmp_code=0
Rule: table=0 cookie=0x1ea priority=0
OpenFlow actions=goto_table:1

        Resubmitted flow: unchanged
        Resubmitted regs: reg0=0x0 reg1=0x0 reg2=0x0 reg3=0x0 reg4=0x0 reg5=0x0 reg6=0x0 reg7=0x0
        Resubmitted  odp: drop
        Resubmitted megaflow: recirc_id=0,skb_priority=0,icmp,in_port=127,dl_src=fa:16:3e:a5:85:78,dl_dst=00:d0:d0:1c:3d:2d,nw_src=192.168.150.2,nw_dst=10.47.159.89,nw_frag=no
        Rule: table=1 cookie=0x294 priority=221,in_port=127
        OpenFlow actions=write_metadata:0xa00000191,goto_table:4

                Resubmitted flow: icmp,metadata=0xa00000191,in_port=127,vlan_tci=0x0000,dl_src=fa:16:3e:a5:85:78,dl_dst=00:d0:d0:1c:3d:2d,nw_src=192.168.150.2,nw_dst=10.47.159.89,nw_tos=0,nw_ecn=0,nw_ttl=0,icmp_type=0,icmp_code=0
                Resubmitted regs: reg0=0x0 reg1=0x0 reg2=0x0 reg3=0x0 reg4=0x0 reg5=0x0 reg6=0x0 reg7=0x0
                Resubmitted  odp: drop
                Resubmitted megaflow: recirc_id=0,skb_priority=0,icmp,in_port=127,dl_src=fa:16:3e:a5:85:78,dl_dst=00:d0:d0:1c:3d:2d,nw_src=192.168.150.2,nw_dst=10.47.159.89,nw_frag=no
                Rule: table=4 cookie=0x295 priority=161,dl_src=fa:16:3e:a5:85:78
                OpenFlow actions=write_metadata:0xa00000191,goto_table:5

                        Resubmitted flow: unchanged
                        Resubmitted regs: reg0=0x0 reg1=0x0 reg2=0x0 reg3=0x0 reg4=0x0 reg5=0x0 reg6=0x0 reg7=0x0
                        Resubmitted  odp: drop
                        Resubmitted megaflow: recirc_id=0,skb_priority=0,icmp,in_port=127,dl_src=fa:16:3e:a5:85:78,dl_dst=00:d0:d0:1c:3d:2d,nw_src=192.168.150.2,nw_dst=10.47.159.89,nw_frag=no
                        Rule: table=5 cookie=0x1ef priority=0
                        OpenFlow actions=goto_table:6

                                Resubmitted flow: unchanged
                                Resubmitted regs: reg0=0x0 reg1=0x0 reg2=0x0 reg3=0x0 reg4=0x0 reg5=0x0 reg6=0x0 reg7=0x0
                                Resubmitted  odp: drop
                                Resubmitted megaflow: recirc_id=0,skb_priority=0,icmp,in_port=127,dl_src=fa:16:3e:a5:85:78,dl_dst=00:d0:d0:1c:3d:2d,nw_src=192.168.150.2,nw_dst=10.47.159.89,nw_frag=no
                                Rule: table=6 cookie=0x1f4 priority=111,dl_dst=00:d0:d0:1c:3d:2d
                                OpenFlow actions=goto_table:7

                                        Resubmitted flow: unchanged
                                        Resubmitted regs: reg0=0x0 reg1=0x0 reg2=0x0 reg3=0x0 reg4=0x0 reg5=0x0 reg6=0x0 reg7=0x0
                                        Resubmitted  odp: drop
                                        Resubmitted megaflow: recirc_id=0,skb_priority=0,icmp,metadata=0/0xffffffff00000000,in_port=127,dl_src=fa:16:3e:a5:85:78,dl_dst=00:d0:d0:1c:3d:2d,nw_src=192.168.150.2,nw_dst=10.47.159.89,nw_frag=no
                                        Rule: table=7 cookie=0x1f1 priority=0
                                        OpenFlow actions=CONTROLLER:65535

Final flow: icmp,metadata=0xa00000191,in_port=127,vlan_tci=0x0000,dl_src=fa:16:3e:a5:85:78,dl_dst=00:d0:d0:1c:3d:2d,nw_src=192.168.150.2,nw_dst=10.47.159.89,nw_tos=0,nw_ecn=0,nw_ttl=0,icmp_type=0,icmp_code=0
Megaflow: recirc_id=0,skb_priority=0,icmp,metadata=0/0xffffffff00000000,in_port=127,dl_src=fa:16:3e:a5:85:78,dl_dst=00:d0:d0:1c:3d:2d,nw_src=192.168.150.2,nw_dst=10.47.159.89,nw_frag=no
Datapath actions: drop
This flow is handled by the userspace slow path because it:
        - Sends "packet-in" messages to the OpenFlow controller.

追踪openvswitch对特定数据报文的流表匹配与处理结果的实例

标签:generate   hand   dump   关键字   ttl   rom   就是   put   文件中   

原文地址:http://blog.51cto.com/smoke520/2314922

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