netdev - Re: [PATCH] filter: introduce SKF_AD_VLAN

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Date:	Thu, 5 Mar 2015 08:24:13 +0100
From:	Michal Kubecek <mkubecek@...e.cz>
To:	Jiri Pirko <jpirko@...hat.com>
Cc:	Alexei Starovoitov <ast@...mgrid.com>,
	Guy Harris <guy@...m.mit.edu>,
	Michal Sekletar <msekleta@...hat.com>, netdev@...r.kernel.org
Subject: Re: [PATCH] filter: introduce SKF_AD_VLAN_PROTO BPF extension

On Thu, Mar 05, 2015 at 07:50:53AM +0100, Jiri Pirko wrote:
> Thu, Mar 05, 2015 at 12:47:06AM CET, ast@...mgrid.com wrote:
> >On 3/4/15 1:14 PM, Guy Harris wrote:
> >>
> >>On Mar 4, 2015, at 1:03 PM, Alexei Starovoitov <ast@...mgrid.com> wrote:
> >>
> >>>the patch is correct and looks clean, but I don't understand
> >>>the motivation for the patch.
> >>>There is already SKF_AD_VLAN_TAG_PRESENT. If it is set then only
> >>>two possible values of vlan_proto are ETH_P_8021Q or ETH_P_8021AD.
> >>>If there another vlan header inside the packet, it's AD.
> >>>So you can do the filtering already without adding new bpf extension...
> >>
> >>I presume he's referring to
> >>
> >>	https://github.com/the-tcpdump-group/libpcap/issues/397
> >>
> >>or
> >>
> >>	https://github.com/the-tcpdump-group/libpcap/issues/390
> >
> >ok. context is clear.
> >yet, it still sounds like something to fix inside libpcap.
> 
> Libpcap need to somehow let kernel now what vlan proto it should filter on.

To be more precise, it does not need it now as there is no syntax for
pcap filter on TPID, one can only filter by VID. But if someone wanted
to implement such feature, it could not work with in-kernel filtering at
the moment.

                                                          Michal Kubecek

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