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cgroup filter on physics interface can't container

DISCUSSION Libo Chen 1 participant 3 messages Dec 9, 2013 – Dec 18, 2013

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Libo Chen

author
#0 lore raw

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

author
#1 lore raw

Re: cgroup filter on physics interface can't control container

ping...

Quoted 32 lines · Libo Chen

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

author
#2 lore raw

Re: cgroup filter on physics interface can't control container

hello guys,

I said before "we can save sk_classid before skb_scrub_packet and restore it after that" since skb->sk had been freed in skb_scrub_packet(), so it is not reasonable. yes?

I have another idea.
commit:f84517253(cls_cgroup: Store classid in struct sock) introduces sk_classid and put it in skb->sk pointer. can we put sk_classid form struct sock to struct sk_buff? then sk_classid will not be affected by dev_forward_skb()->skb_scrub_packet() ?

any comment are welcome!

thanks,
Libo

Quoted 36 lines · Libo Chen

ping...

Quoted 32 lines · Libo Chen

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