[libvirt-users] Libvirt "tc ingress qdisc" automatically removed by ovs vlan tag setting, how?

[Qiu Yu]

With outbound QoS setting in Libvirt XML, libvirt will add a tc
ingress qdisc for traffic shaping. Then if you set VLAN tag to that
tap device, this qdisc will automatically gone by no reason.

Could anyone shed some lights where should I look into? I'm really
confused and got no clue here. Thanks!

Steps to reproduce
--
# virsh start instance-name
# virsh dumpxml instance-name

...
    <interface type='bridge'>
      <mac address='fa:16:3e:b9:8f:2a'/>
      <source bridge='br-int'/>
      <virtualport type='openvswitch'>
        <parameters interfaceid='0a2b02ca-4824-4bda-baa9-05fff7a3146d'/>
      </virtualport>
      <target dev='tap0a2b02ca-48'/>
      <model type='virtio'/>
      <bandwidth>
        <outbound average='256' peak='512' burst='512'/>
      </bandwidth>
      <alias name='net0'/>
      <address type='pci' domain='0x0000' bus='0x00' slot='0x03'
function='0x0'/>
    </interface>
...

# tc qdisc ls dev tap0a2b02ca-48
qdisc htb 1: root refcnt 2 r2q 10 default 1 direct_packets_stat 0
qdisc sfq 2: parent 1:1 limit 127p quantum 1514b perturb 10sec
qdisc ingress ffff: parent ffff:fff1 ----------------  (<-- already showed up)

# ovs-vsctl set port tap0a2b02ca-48 tag=1
# tc qdisc ls dev tap0a2b02ca-48
qdisc htb 1: root refcnt 2 r2q 10 default 1 direct_packets_stat 0
qdisc sfq 2: parent 1:1 limit 127p quantum 1514b perturb 10sec
(<-- ingress qdisc is gone)

After that, if add this qdisc manually and re-set vlan tag, problem no
longer exists. But it can always be reproduced after "virsh destroy /
start" cycle.

# tc qdisc add dev tap0a2b02ca-48 handle ffff: ingress
# ovs-vsctl clear port tap0a2b02ca-48 tag
# ovs-vsctl set port tap0a2b02ca-48 tag=1
# tc qdisc ls dev tap0a2b02ca-48
qdisc htb 1: root refcnt 2 r2q 10 default 1 direct_packets_stat 0
qdisc sfq 2: parent 1:1 limit 127p quantum 1514b perturb 10sec
qdisc ingress ffff: parent ffff:fff1 ----------------  (<-- still exists)

Other information
--
# ovs-vsctl --version
ovs-vsctl (Open vSwitch) 1.9.2
Compiled May 27 2013 14:19:16
# uname -r
2.6.32-358.111.1.openstack.el6.x86_64
# virsh --version (This is a version I built from libvirt upstream
origin/v0.9.11-stable branch)
0.9.11.9

--
Qiu Yu