Hi!

Could you please explain me such strange situation:

I have Openstack with OVS and VMs up and running
OVS is configured with GRE


I have compute node (where VMs are started) with the following OVS
configuration:

alias ovs='ovs-vsctl'

ovs show
7f013a19-b6d5-4038-8ba8-ae548b581605
...
    Bridge br-int
        Port "qvo22eb488a-9a"
            tag: 1
            Interface "qvo22eb488a-9a"
        Port br-int
            Interface br-int
                type: internal
        Port "qvo6715963b-e7"
            tag: 1
            Interface "qvo6715963b-e7"
        Port patch-tun
            Interface patch-tun
                type: patch
                options: {peer=patch-int}
    Bridge br-tun
        Port patch-int
            Interface patch-int
                type: patch
                options: {peer=patch-tun}
        Port "gre-2"
            Interface "gre-2"
                type: gre
                options: {in_key=flow, out_key=flow,
remote_ip="192.168.4.253"}
        Port br-tun
            Interface br-tun
                type: internal
    ovs_version: "1.10.0"


As you can see, I have 2 ports in br-int:
* qvo22eb488a-9a
* qvo6715963b-e7
These ports are attached to VMs with ip addresses 192.168.1.2 and
192.168.1.4

ip link show dev qvo22eb488a-9a
35: qvo22eb488a-9a: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500
qdisc pfifo_fast state UP qlen 1000
    link/ether 3a:01:46:ad:33:cc brd ff:ff:ff:ff:ff:ff
[root@compute1 ~]# ip link show dev qvo6715963b-e7
27: qvo6715963b-e7: <BROADCAST,MULTICAST,PROMISC,UP,LOWER_UP> mtu 1500
qdisc pfifo_fast state UP qlen 1000
    link/ether ee:da:16:bd:93:ac brd ff:ff:ff:ff:ff:ff



I'm trying to understand traffic flow with tcpdump  and got unexpected (for
me) results (for one VM. other have same results):


tcpdump  -n -i qvo22eb488a-9a
listening on qvo22eb488a-9a, link-type EN10MB (Ethernet), capture size
65535 bytes
17:20:35.139298 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP,
Request from fa:16:3e:27:07:47, length 280
17:20:36.905414 IP 0.0.0.0.bootpc > 255.255.255.255.bootps: BOOTP/DHCP,
Request from fa:16:3e:5f:4f:28, length 280
17:20:36.906830 IP 192.168.1.3.bootps > 192.168.1.4.bootpc: BOOTP/DHCP,
Reply, length 321
17:20:36.906961 IP 192.168.1.4 > 192.168.1.3: ICMP 192.168.1.4 udp port
bootpc unreachable, length 357
17:20:43.755827 IP 192.168.1.3 > 192.168.1.4: ICMP echo request, id 11567,
seq 2, length 64

So I see traffic.

BUT I can't see it on OVS ifaces:


tcpdump  -n -i br-int
listening on br-int, link-type EN10MB (Ethernet), capture size 65535 bytes

0 packets captured
0 packets received by filter
0 packets dropped by kernel

[root@compute1 ~]# tcpdump  -n -i br-tun

0 packets captured
0 packets received by filter
0 packets dropped by kernel



Could you please explain me how can I use tcpdump (or other pcap-based
tools) with OVS?

BTW, how can I dump traffic on OVS-only ports, which does not have system
interfaces.


Best Regards,
Max Mazur
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