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

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Date:   Thu, 1 Sep 2022 22:39:08 -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 Thu, Sep 1, 2022 at 10:23 PM Alexander Aring <aahringo@...hat.com> wrote:
>
> Hi,
>
> On Wed, Aug 31, 2022 at 8:09 PM Miquel Raynal <miquel.raynal@...tlin.com> wrote:
> >
> > Hello again,
> >
> > miquel.raynal@...tlin.com wrote on Wed, 31 Aug 2022 17:39:03 +0200:
> >
> > > 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
> > > 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 think I now have a clearer understanding on how the devices behave.
> >
> > I turned the devices into promiscuous mode and could observe that some
> > frames were considered wrong. Indeed, it looks like the PHYs add the
> > FCS themselves, while the spec says that the FCS should be provided to
> > the PHY. Anyway, I dropped the FCS calculations from the different MLME
> > frames forged and it helped a lot.
> >
>
> This is currently the case because monitor interfaces and AF_PACKET
> will not have the FCS in the payload. As you already figured out you
> can't refer 802.15.4 promiscuous mode to mac802154 promiscuous mode,
> it was a historically growing term as people wanted to have a sniffer
> device and used a promiscuous term from a datasheet (my guess).
> Vendors has a different meaning of promiscuous mode as the one from
> 802.15.4. IFF_PROMISC should be mapped to non-filtered mode which is
> more equal to a sniffer device. However we need to find solutions
> which fulfill everybody.
>
> > I also kind of "discovered" the concept of hardware address filtering
> > on atusb which makes me realize that maybe we were not talking about
> > the same "filtering" until now.
> >
> > Associations and disassociations now work properly, I'm glad I fixed
> > "everything". I still need to figure out if using the promiscuous mode
> > everywhere is really useful or not (maybe the hardware filters were
> > disabled in this mode and it made it work). However, using the
> > promiscuous mode was the only way I had to receive acknowledgements,
> > otherwise they were filtered out by the hardware (the monitor was
> > showing that the ack frames were actually being sent).
> >
>
> This is correct, the most hardware will turn off automatic
> ackknowledge handling if address filtering is off (I am sure I said
> that before). We cannot handle acks on mac802154 if they are time
> critical.
>

If this is required we should discuss this topic...

- Alex