cgroup filter on physics interface can't container

[Libo Chen <clbchenlibo.chen@huawei.com>]

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