Openvswitch手册(4): Mirror

这一节我们来分析Mirror

Mirror就是配置一个bridge，将某些包发给指定的mirrored ports

对于包的选择：

• select_all，所有的包
• select_dst_port
• select_src_port
• select_vlan

对于指定的目的：

• output_port (SPAN)
• output_vlan (RSPAN)

Port mirroring on a Cisco Systems switch is generally referred to as Switched Port ANalyzer (SPAN) or Remote Switched Port ANalyzer (RSPAN)

(1) Configure Mirroring
root@XorPlus# ovs-vsctl --db=tcp:10.10.50.215:6633 -- set bridge br0 mirrors=@m -- --id=@te-1/1/1 get Port te-1/1/1 -- --id=@te-1/1/2 get Port te-1/1/2 -- --id=@te-1/1/3 get Port te-1/1/3 -- --id=@m create Mirror name=mymirror select-dst-port=@te-1/1/1,@te-1/1/2 select-src-port=@te-1/1/1,@te-1/1/2 output-port=@te-1/1/3 root@XorPlus#
In above configuration, user configure the te-1/1/1, te-1/1/2 and te-1/1/3 in the mirroring, in which the source port are te-1/1/1 and te-1/1/2 (including the ingress and egress), the output port (monitor port) is te-1/1/3.
The “select-dst-port” means some packet (in switch chip) will go-out from the specified port (egress).
The “select-src-port” means some packet enter the specified port (ingress).
(2) Delete the Mirroring
root@XorPlus# ovs-vsctl --db=tcp:10.10.50.215:6633 -- remove bridge br0 mirrors mymirror

• Ingress traffic-Traffic that enters the switch.
• Egress traffic-Traffic that leaves the switch.
• Source (SPAN) port -A port that is monitored with use of the SPAN feature.
• Source (SPAN) VLAN -A VLAN whose traffic is monitored with use of the SPAN feature.
• Destination (SPAN) port -A port that monitors source ports, usually where a network analyzer is connected.
• Reflector Port -A port that copies packets onto an RSPAN VLAN.
• Local SPAN-The SPAN feature is local when the monitored ports are all located on the same switch as the destination port.
• Remote SPAN (RSPAN)-Some source ports are not located on the same switch as the destination port. RSPAN is an advanced feature that requires a special VLAN to carry the traffic that is monitored by SPAN between switches.
• Port-based SPAN (PSPAN)-The user specifies one or several source ports on the switch and one destination port.
• VLAN-based SPAN (VSPAN)-On a particular switch, the user can choose to monitor all the ports that belong to a particular VLAN in a single command.

RSPAN allows you to monitor source ports that are spread all over a switched network, not only locally on a switch with SPAN.

The functionality works exactly as a regular SPAN session. The traffic that is monitored by SPAN is not directly copied to the destination port, but flooded into a special RSPAN VLAN. The destination port can then be located anywhere in this RSPAN VLAN. There can even be several destination ports.

These are a few remarks on this design:

• S1 is called a source switch. Packets only enter the RSPAN VLAN in switches that are configured as RSPAN source. Currently, a switch can only be the source for one RSPAN session, which means that a source switch can only feed one RSPAN VLAN at a time.
• S2 and S3 are intermediate switches. They are not RSPAN sources and do not have destination ports. A switch can be intermediate for any number of RSPAN sessions.
• S4 and S5 are destination switches. Some of their ports are configured to be destination for an RSPAN session.
• You can see that RSPAN packets are flooded into the RSPAN VLAN. Even switches that are not on the path to a destination port, such as S2, receive the traffic for the RSPAN VLAN. You can find it useful to prune this VLAN on such S1-S2 links.
• In order to achieve the flooding, learning is disabled on the RSPAN VLAN.
• In order to prevent loops, the STP has been maintained on the RSPAN VLAN. Therefore, RSPAN cannot monitor Bridge Protocol Data Units (BPDUs).

我们先来测试SPAN

我们按照下面的拓扑结构创建vswitch

$ sudo ovs-vsctl add-port helloworld first_br
$ sudo ovs-vsctl add-port helloworld second_br -- set Port second_br tag=110      
$ sudo ovs-vsctl add-br helloworld1
$ sudo ovs-vsctl add-port helloworld1 second_if -- set Port second_if tag=110
$ sudo ovs-vsctl add-port helloworld1 third_br -- set Port third_br tag=110         
$ sudo ovs-vsctl show
c24322e6-8453-402a-afaf-64757ef231e9
    Bridge helloworld
        Controller "tcp:16.158.165.102:6633"
            is_connected: true
        Port "vnet8"
            Interface "vnet8"
        Port first_br
            Interface first_br
        Port second_br
            tag: 110
            Interface second_br
        Port "vnet10"
            Interface "vnet10"
        Port helloworld
            Interface helloworld
                type: internal
        Port "vnet9"
            Interface "vnet9"
    Bridge "helloworld1"
        Port second_if
            tag: 110
            Interface second_if
        Port "helloworld1"
            Interface "helloworld1"
                type: internal
        Port third_br
            tag: 110
            Interface third_br
    ovs_version: "2.0.1"

然后我们在first_br上面mirror所有进出vnet8的包

$ sudo ovs-vsctl -- set bridge helloworld mirrors=@m -- --id=@vnet8 get Port vnet8 -- --id=@first_br get Port first_br -- --id=@m create Mirror name=mirrorvnet8 select-dst-port=@vnet8 select-src-port=@vnet8 output-port=@first_br
19ed2f51-3245-4d5b-8e6c-67ccbb7c7ebd

这时候我们监听first_if，并且从instance01里面ping 10.10.10.3，可以看到下面的效果

$ sudo tcpdump  -n -i first_if icmp
tcpdump: WARNING: first_if: no IPv4 address assigned
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on first_if, link-type EN10MB (Ethernet), capture size 65535 bytes
23:58:02.310198 IP 10.10.10.1 > 10.10.10.3: ICMP echo request, id 3200, seq 1, length 64
23:58:02.312447 IP 10.10.10.1 > 10.10.10.3: ICMP echo request, id 3200, seq 1, length 64
23:58:02.314314 IP 10.10.10.3 > 10.10.10.1: ICMP echo reply, id 3200, seq 1, length 64
23:58:03.311894 IP 10.10.10.1 > 10.10.10.3: ICMP echo request, id 3200, seq 2, length 64
23:58:03.312266 IP 10.10.10.3 > 10.10.10.1: ICMP echo reply, id 3200, seq 2, length 64
23:58:04.313522 IP 10.10.10.1 > 10.10.10.3: ICMP echo request, id 3200, seq 3, length 64
23:58:04.313739 IP 10.10.10.3 > 10.10.10.1: ICMP echo reply, id 3200, seq 3, length 64
23:58:05.314827 IP 10.10.10.1 > 10.10.10.3: ICMP echo request, id 3200, seq 4, length 64
23:58:05.314979 IP 10.10.10.3 > 10.10.10.1: ICMP echo reply, id 3200, seq 4, length 64
23:58:06.316870 IP 10.10.10.1 > 10.10.10.3: ICMP echo request, id 3200, seq 5, length 64
23:58:06.317156 IP 10.10.10.3 > 10.10.10.1: ICMP echo reply, id 3200, seq 5, length 64
23:58:07.318242 IP 10.10.10.1 > 10.10.10.3: ICMP echo request, id 3200, seq 6, length 64
23:58:07.318481 IP 10.10.10.3 > 10.10.10.1: ICMP echo reply, id 3200, seq 6, length 64
23:58:08.319579 IP 10.10.10.1 > 10.10.10.3: ICMP echo request, id 3200, seq 7, length 64
23:58:08.319802 IP 10.10.10.3 > 10.10.10.1: ICMP echo reply, id 3200, seq 7, length 64

然后我们来配置RSPAN

我们对进入vnet9的所有进出包，然而ouput到一个vlan 110

$ sudo ovs-vsctl -- set bridge helloworld mirrors=@m -- --id=@vnet9 get Port vnet9 -- --id=@m create Mirror name=mirrorvnet9 select-dst-port=@vnet9 select-src-port=@vnet9 output-vlan=110
cb361fa2-914d-494b-94ef-c625d194247c

在helloworld1中也要配置从110来的，都output到vlan 110

$ sudo ovs-vsctl -- set bridge helloworld1 mirrors=@m -- --id=@m create Mirror name=mirrorvlan select-vlan=110 output-vlan=110
cef13445-c6ea-45e7-bb9d-1a267b24c91c

disable mac address learning for vlan 110

$ sudo ovs-vsctl set bridge helloworld flood-vlans=110
$ sudo ovs-vsctl set bridge helloworld1 flood-vlans=110

这时候我们监听third_if，并且从instance02里面ping 10.10.10.3，可以看到下面的效果

$ sudo tcpdump  -n -i third_if icmp                   
tcpdump: WARNING: third_if: no IPv4 address assigned
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on third_if, link-type EN10MB (Ethernet), capture size 65535 bytes
00:24:38.089192 IP 10.10.10.2 > 10.10.10.3: ICMP echo request, id 2999, seq 1, length 64
00:24:38.090844 IP 10.10.10.2 > 10.10.10.3: ICMP echo request, id 2999, seq 1, length 64
00:24:38.093228 IP 10.10.10.3 > 10.10.10.2: ICMP echo reply, id 2999, seq 1, length 64
00:24:39.090506 IP 10.10.10.2 > 10.10.10.3: ICMP echo request, id 2999, seq 2, length 64
00:24:39.091024 IP 10.10.10.3 > 10.10.10.2: ICMP echo reply, id 2999, seq 2, length 64
00:24:40.091945 IP 10.10.10.2 > 10.10.10.3: ICMP echo request, id 2999, seq 3, length 64
00:24:40.092202 IP 10.10.10.3 > 10.10.10.2: ICMP echo reply, id 2999, seq 3, length 64
00:24:41.093826 IP 10.10.10.2 > 10.10.10.3: ICMP echo request, id 2999, seq 4, length 64
00:24:41.093917 IP 10.10.10.3 > 10.10.10.2: ICMP echo reply, id 2999, seq 4, length 64
00:24:42.095681 IP 10.10.10.2 > 10.10.10.3: ICMP echo request, id 2999, seq 5, length 64
00:24:42.095915 IP 10.10.10.3 > 10.10.10.2: ICMP echo reply, id 2999, seq 5, length 64
00:24:43.097414 IP 10.10.10.2 > 10.10.10.3: ICMP echo request, id 2999, seq 6, length 64
00:24:43.097586 IP 10.10.10.3 > 10.10.10.2: ICMP echo reply, id 2999, seq 6, length 64