netdev - Re: tcpdump's capture filter: "vlan" doesn't match

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Date:	Thu, 16 Oct 2014 16:39:07 -0700
From:	Ani Sinha <ani@...sta.com>
To:	Lukas Tribus <luky-37@...mail.com>
Cc:	Daniel Borkmann <dborkman@...hat.com>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	John Fastabend <john.r.fastabend@...el.com>,
	Michał Mirosław <mirq-linux@...e.qmqm.pl>,
	Jiri Pirko <jpirko@...hat.com>,
	Ben Hutchings <bhutchings@...arflare.com>,
	Atzm Watanabe <atzm@...atosphere.co.jp>,
	Patrick McHardy <kaber@...sh.net>,
	Jesse Gross <jesse@...ira.com>,
	Michael Richardson <mcr@...delman.ca>,
	Ani Sinha <ani@...stanetworks.com>, fenner <fenner@...sta.com>
Subject: Re: tcpdump's capture filter: "vlan" doesn't match

+fenner.

I had spent some considerable time in the past looking into this and
proposing a patch :

http://seclists.org/tcpdump/2013/q1/0

However, there was no feedback and I got sucked into a different
project and this work fell through the cracks. If someone else picks
it up, I will be glad to help/lend a hand.

Cheers,
ani


On Thu, Oct 16, 2014 at 4:25 PM, Lukas Tribus <luky-37@...mail.com> wrote:
>>> Isn't disabling rx-vlan-offloading supposed to remedy those problems?
>>
>> There were some discussions on this in the past e.g. [1]. We have
>> SKF_AD_VLAN_TAG and SKF_AD_VLAN_TAG_PRESENT for the BPF filter on
>> this, but libpcap is currently not making use of any of them.
>>
>> [1] http://thread.gmane.org/gmane.linux.network/247947
>
> Thanks for the link. I see the situation is unfortunate and although those
> new BPF filters in the kernel may fix the actual filtering problem, one
> thing seems to remain impossible: disabling all this kernel magic and
> passing the frame as-is to libpcap without interception (avoiding any
> kind of artificial header reconstruction).
>
> How is the situation with netsniff-ng anyway? Does it use vlan BPF filter
> in the kernel?
>
>
>
> Regards,
>
> Lukas
>
>
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