netdev - Re: [PATCH wpan-next 01/20] net: mac802154: Allow the creation of coordinator interfaces

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Date:   Thu, 1 Sep 2022 22:09:38 -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 - ML <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>,
        Network Development <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 01/20] net: mac802154: Allow the creation of
 coordinator interfaces

Hi,

On Wed, Aug 31, 2022 at 11:39 AM Miquel Raynal
<miquel.raynal@...tlin.com> wrote:
>
> Hi Alexander & Stefan,
>
> aahringo@...hat.com wrote on Mon, 29 Aug 2022 22:23:09 -0400:
>
> I am currently testing my code with the ATUSB devices, the association
> works, so it's a good news! However I am struggling to get the
> association working for a simple reason: the crafted ACKs are
> transmitted (the ATUSB in monitor mode sees it) but I get absolutely

What is a crafted ACK here?

> nothing on the receiver side.
>
> The logic is:
>
> coord0                 coord1
> association req ->
>                 <-     ack
>                 <-     association response
> ack             ->
>
> The first ack is sent by coord1 but coord0 never sees anything. In
> practice coord0 has sent an association request and received a single
> one-byte packet in return which I guess is the firmware saying "okay, Tx
> has been performed". Shall I interpret this byte differently? Does it
> mean that the ack has also been received?
>
> I could not find a documentation of the firmware interface, I went
> through the wiki but I did not find something clear about what to
> expect or "what the driver should do". But perhaps this will ring a
> bell on your side?
>
> [...]
>
> > I did not see the v2 until now. Sorry for that.
>
> Ah! Ok, no problem :)
>
> >
> > However I think there are missing bits here at the receive handling
> > side. Which are:
> >
> > 1. Do a stop_tx(), stop_rx(), start_rx(filtering_level) to go into
> > other filtering modes while ifup.
>
> Who is supposed to change the filtering level?
>

depending on what mac802154 is doing, for scan it's required to switch
the filter level to promiscuous?

> For now there is only the promiscuous mode being applied and the user
> has no knowledge about it, it's just something internal.
>

Okay, sounds good.

> Changing how the promiscuous mode is applied (using a filtering level
> instead of a "promiscuous on" boolean) would impact all the drivers
> and for now we don't really need it.
>

no, it does not. Okay, you can hide the promiscuous mode driver
callback from start()... but yes the goal would be to remove the
promiscuous mode op in future.

> > I don't want to see all filtering modes here, just what we currently
> > support with NONE (then with FCS check on software if necessary),
> > ?THIRD/FOURTH? LEVEL filtering and that's it. What I don't want to see
> > is runtime changes of phy flags. To tell the receive path what to
> > filter and what's not.
>
> Runtime changes on a dedicated "filtering" PHY flag is what I've used
> and it works okay for this situation, why don't you want that? It
> avoids the need for (yet) another rework of the API with the drivers,
> no?
>

I am not sure what exactly here is "dedicated "filtering" PHY flag" if
it's the hwflags it was never made to be changed during runtime.

I also don't know what "yet another rework of the API" means here,
there is a current behaviour which we can assume and only hwsim is a
little bit out of range which should overwrite the "default".

> > 2. set the pan coordinator bit for hw address filter. And there is a
> > TODO about setting pkt_type in mac802154 receive path which we should
> > take a look into. This bit should be addressed for coordinator support
> > even if there is the question about coordinator vs pan coordinator,
> > then the kernel needs a bit as coordinator iface type parameter to
> > know if it's a pan coordinator and not coordinator.
>
> This is not really something that we can "set". Either the device
> had performed an association and it is a child device: it is not the
> PAN coordinator, or it initiated the PAN and it is the PAN coordinator.
> There are commands to change that later on but those are not supported.
>
> The "PAN coordinator" information is being added in the association
> series (which comes after the scan). I have handled the pkt_type you are
> mentioning.
>

okay.

- Alex