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From:   Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@toke.dk>
To:     Lorenzo Bianconi <lorenzo.bianconi@redhat.com>
Cc:     Jesper Dangaard Brouer <brouer@redhat.com>,
        Kalle Valo <kvalo@codeaurora.org>,
        linux-wireless@vger.kernel.org, nbd@nbd.name,
        Daniel Borkmann <borkmann@iogearbox.net>,
        Alexei Starovoitov <alexei.starovoitov@gmail.com>,
        "netdev\@vger.kernel.org" <netdev@vger.kernel.org>
Subject: Re: [RFC 0/5] add XDP support to mt76x2e/mt76x0e drivers
In-Reply-To: <20181129154502.GA29066@localhost.localdomain>
References: <cover.1543343124.git.lorenzo.bianconi@redhat.com> <8736rla4ow.fsf@purkki.adurom.net> <20181128104436.GA2298@localhost.localdomain> <87bm69v0ol.fsf@toke.dk> <20181128164306.0135ca83@redhat.com> <20181129103054.GA6365@localhost.localdomain> <87sgzkqaip.fsf@toke.dk> <20181129135825.GD6365@localhost.localdomain> <87h8g0q8py.fsf@toke.dk> <20181129154502.GA29066@localhost.localdomain>
Date:   Thu, 29 Nov 2018 17:06:54 +0100
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Lorenzo Bianconi <lorenzo.bianconi@redhat.com> writes:

>> Lorenzo Bianconi <lorenzo.bianconi@redhat.com> writes:
>>=20
>> >> Lorenzo Bianconi <lorenzo.bianconi@redhat.com> writes:
>> >>=20
>> >> >> On Wed, 28 Nov 2018 13:36:26 +0100
>> >> >> Toke H=C3=B8iland-J=C3=B8rgensen <toke@toke.dk> wrote:
>> >> >>=20
>
> [...]
>
>> >> >
>> >> > I guess it will be enough to avoid loading a 'non-WiFi' bpf program=
 on
>> >> > a 802.11 netdevice (and vice versa). We could add a flag (or someth=
ing
>> >> > similar) in XDP_SETUP_PROG section of netdev_bpf data structure and
>> >> > use ieee80211_ptr netdevice pointer in order to guarantee that the =
bpf
>> >> > program will work on the expected 'frame-type'
>> >>=20
>> >> Yeah, a flag would be good; we've been discussing that for other XDP =
use
>> >> cases; it's not a done deal yet, but I think it would be useful.
>> >
>> > Do you think something wifi specific is ok (e.g bool wifi) or do you p=
refer
>> > something more general (e.g u32 frame_type)?
>>=20
>> My thought was a feature flag where the program can set a flag which
>> means "I expect 802.11 frames", and the driver can set a flag saying "I
>> emit 802.11 frames", and if those two flags don't match, the verifier
>> can refuse to load the program. This would not be fool-proof (an XDP
>> program can still corrupt things if written incorrectly), but it would
>> at least protect against the most obvious mistakes.
>
> I guess we can use iee80211_ptr in dev_xdp_install to double check if it =
is
> allowed to upload a 802.11 (or 802.3) bpf program

Yeah, I think it's more an issue of convincing the wider XDP community
that support for feature flags is in fact needed ;)

-Toke