Re: [PATCH wpan/next v3 5/9] net: mac802154: Drop IEEE802154_HW_RX_DROP_BAD_CKSUM

From: Alexander Aring <aahringo@redhat.com>
To: Miquel Raynal <miquel.raynal@bootlin.com>
Cc: Alexander Aring <alex.aring@gmail.com>,
	Stefan Schmidt <stefan@datenfreihafen.org>,
	linux-wpan@vger.kernel.org,
	"David S. Miller" <davem@davemloft.net>,
	Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
	Eric Dumazet <edumazet@google.com>,
	netdev@vger.kernel.org, David Girault <david.girault@qorvo.com>,
	Romuald Despres <romuald.despres@qorvo.com>,
	Frederic Blain <frederic.blain@qorvo.com>,
	Nicolas Schodet <nico@ni.fr.eu.org>,
	Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Subject: Re: [PATCH wpan/next v3 5/9] net: mac802154: Drop IEEE802154_HW_RX_DROP_BAD_CKSUM
Date: Sat, 24 Sep 2022 15:50:51 -0400	[thread overview]
Message-ID: <CAK-6q+i64s=u-K3-t4So8jtQQxx_+FuWVc_THPxtFw6ruJ-zrg@mail.gmail.com> (raw)
In-Reply-To: <20220921174932.37f2938f@xps-13>

Hi,

On Wed, Sep 21, 2022 at 11:49 AM Miquel Raynal
<miquel.raynal@bootlin.com> wrote:
>
> Hi Alexander,
>
> aahringo@redhat.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@bootlin.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