netdev - Re: cgroup matches in INPUT chain

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Date:	Fri, 20 Mar 2015 13:55:11 -0700
From:	Cong Wang <cwang@...pensource.com>
To:	Daniel Mack <daniel@...que.org>
Cc:	Florian Westphal <fw@...len.de>,
	Daniel Borkmann <dborkman@...hat.com>,
	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 Fri, Mar 20, 2015 at 9:21 AM, Daniel Mack <daniel@...que.org> 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.
>

Loopback is special because the skb->dst is kept across TX and RX.

How possible is your external interface sets dst for the packets?
Are you using a tunnel device or you have some other setup you didn't mention?
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