hello network hackers,

        A linux container was builded with veth pair(veth0 inside container, 
veth1 outside container),

the config as below:

  lxc.network.type = veth
  lxc.network.flags = up
  lxc.network.link = br0  // base on eth0
  lxc.network.name = eth0
  lxc.network.ipv4 = 128.5.130.26/24

then I use tc command with cgroup filter on veth0, it works well. But when 
setting on eth0, it doesn`t work.

The reason is dev_forward_skb() in veth_xmit will call skb_scrub_packet and 
clean all information including skb->sk
in the skb, so if cls_cgroup_classify is working in serving softirq state, it 
will return failer, see below:

        if (in_serving_softirq()) {
                /* If there is an sk_classid we'll use that. */
                if (!skb->sk)
                        return -1;
                classid = skb->sk->sk_classid;
        }


Qdisc with cgroup filter on physics interface can not control a container 
network, it is disappointed.

we can save sk_classid before skb_scrub_packet and restore it after that. Is it 
reasonable?  or any way to achieve this?

thanks,
Libo

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