netdev - Re: [PATCH wpan/next v3 5/9] net: mac802154: Drop IEEE802154_HW_RX_DROP_BAD

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Date:   Sat, 24 Sep 2022 15:50:51 -0400
From:   Alexander Aring <aahringo@...hat.com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Alexander Aring <alex.aring@...il.com>,
        Stefan Schmidt <stefan@...enfreihafen.org>,
        linux-wpan@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org,
        David Girault <david.girault@...vo.com>,
        Romuald Despres <romuald.despres@...vo.com>,
        Frederic Blain <frederic.blain@...vo.com>,
        Nicolas Schodet <nico@...fr.eu.org>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH wpan/next v3 5/9] net: mac802154: Drop IEEE802154_HW_RX_DROP_BAD_CKSUM

Hi,

On Wed, Sep 21, 2022 at 11:49 AM Miquel Raynal
<miquel.raynal@...tlin.com> wrote:
>
> Hi Alexander,
>
> aahringo@...hat.com wrote on Thu, 8 Sep 2022 20:49:36 -0400:
>
> > Hi,
> >
> > On Mon, Sep 5, 2022 at 4:34 PM Miquel Raynal <miquel.raynal@...tlin.com> wrote:
> > >
> > > This IEEE802154_HW_RX_DROP_BAD_CKSUM flag was only used by hwsim to
> > > reflect the fact that it would not validate the checksum (FCS). In other
> > > words, the filtering level of hwsim is always "NONE" while the core
> > > expects it to be higher.
> > >
> > > Now that we have access to real filtering levels, we can actually use
> > > them and always enforce the "NONE" level in hwsim. This case is already
> > > correctly handled in the receive so we can drop the flag.
> > >
> >
> > I would say the whole hwsim driver currently only works because we
> > don't transmit wrong frames on a virtual hardware... However this can
> > be improved, yes. In my opinion the hwsim driver should pretend to
> > work like other transceivers sending frames to mac802154. That means
> > the filtering level should be implemented in hwsim not in mac802154 as
> > on real hardware the hardware would do filtering.
> >
> > I think you should assume for now the previous behaviour that hwsim
> > does not send bad frames out. Of course there is a bug but it was
> > already there before, but the fix would be to change hwsim driver.
>
> Well, somehow I already implemented all the filtering by software in
> one of the other patches. I now agree that it was not relevant (because
> of the AACK issue you raised), but instead of fully dropping this code
> I might just move it to hwsim because there it would perfectly make
> sense?
>

Yes, I agree. You should make the "in-driver receive path" acting like
other hardware (In sense what we currently agree on what filtering
they do) if promiscuous mode is turned off/on.

It makes sense and should be done there. The
IEEE802154_HW_RX_DROP_BAD_CKSUM flag should still be dropped.

- Alex