netdev - Re: cgroup matches in INPUT chain

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Message-ID: <550C8094.5000508@iogearbox.net>
Date:	Fri, 20 Mar 2015 21:18:28 +0100
From:	Daniel Borkmann <daniel@...earbox.net>
To:	Daniel Mack <daniel@...que.org>, Florian Westphal <fw@...len.de>
CC:	Alexey Perevalov <a.perevalov@...sung.com>,
	Pablo Neira Ayuso <pablo@...filter.org>,
	netdev <netdev@...r.kernel.org>
Subject: Re: cgroup matches in INPUT chain

On 03/20/2015 05:21 PM, Daniel Mack wrote:
> On 03/20/2015 05:11 PM, Florian Westphal wrote:
>> Daniel Mack <daniel@...que.org> wrote:
>>> In my simple test setup, when skbs are dequeued by process_backlog(),
>>> they have skb->_skb_refdst set, and hence ip_rcv_finish() does not call
>>> into early_demux() prior to iterating the INPUT chain:
>>
>> Yes, because we already have a route set.
>>
>> Are we talking about loopback?
>
> I'm testing this on the lookback device, but I've seen similar behavior
> on external interfaces too. However, I fail to see a pattern in that.
>
>> What are you trying to do?
>
> Basically, I have a simple server that listens to a TCP port, accepts a
> connection, writes out a short string and closes the connection again.
> The process is put into a netcls cgroup controller, and a classid is
> assigned to it, and I'm trying catch all traffic sent to it (regardless
> of the interface in use) with a netfilter rule.
>
> However, that doesn't work, because under the described circumstances,
> the match callback of the cgroup netfilter module is always called with
> an skb that has no sk set.

Thanks for the report Daniel. I see the same here, so let me look
closer into it on Monday and get back to you. Looks like commit
a00e76349f3564bb is not sufficient.

Cheers,
Daniel
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