netdev - Re: [PATCH] AF_PACKET doesnt strip VLAN information

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Date:   Tue, 1 Oct 2019 11:52:11 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     Willem de Bruijn <willemdebruijn.kernel@...il.com>,
        Sriram Krishnan <srirakr2@...co.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        xe-linux-external@...co.com,
        "David S. Miller" <davem@...emloft.net>,
        Network Development <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] AF_PACKET doesnt strip VLAN information

On Tue, Oct 1, 2019 at 11:44 AM Stephen Hemminger
<stephen@...workplumber.org> wrote:
>
> On Mon, 30 Sep 2019 11:16:14 -0400
> Willem de Bruijn <willemdebruijn.kernel@...il.com> wrote:
>
> > On Mon, Sep 30, 2019 at 1:24 AM Sriram Krishnan <srirakr2@...co.com> wrote:
> > >
> > > When an application sends with AF_PACKET and places a vlan header on
> > > the raw packet; then the AF_PACKET needs to move the tag into the skb
> > > so that it gets processed normally through the rest of the transmit
> > > path.
> > >
> > > This is particularly a problem on Hyper-V where the host only allows
> > > vlan in the offload info.
> >
> > This sounds like behavior that needs to be addressed in the driver, instead?
>
> This was what we did first, but the problem was more general.
> For example, many filtering functions assume that vlan tag is in
> skb meta data, not the packet data itself.

Out of curiosity, can you share an example?

> Therefore AF_PACKET would
> get around any filter rules.

Packet sockets are not the only way to inject packets into the kernel.
This probably also affects tap.