netdev - Re: [wpan-next v2 08/27] net: ieee802154: Drop symbol duration settings when the core does it already

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Message-ID: <CAB_54W4Z0H5ubvOBjpnCpGOWYrNXYOJvxB4_kZsp8LqdJrTLkg@mail.gmail.com>
Date:   Tue, 18 Jan 2022 17:43:00 -0500
From:   Alexander Aring <alex.aring@...il.com>
To:     Miquel Raynal <miquel.raynal@...tlin.com>
Cc:     Stefan Schmidt <stefan@...enfreihafen.org>,
        linux-wpan - ML <linux-wpan@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "open list:NETWORKING [GENERAL]" <netdev@...r.kernel.org>,
        Michael Hennerich <michael.hennerich@...log.com>,
        Harry Morris <h.morris@...coda.com>,
        Varka Bhadram <varkabhadram@...il.com>,
        Xue Liu <liuxuenetmail@...il.com>, Alan Ott <alan@...nal11.us>,
        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>,
        "linux-wireless@...r.kernel.org Wireless" 
        <linux-wireless@...r.kernel.org>
Subject: Re: [wpan-next v2 08/27] net: ieee802154: Drop symbol duration
 settings when the core does it already

Hi,

On Tue, 18 Jan 2022 at 05:38, Miquel Raynal <miquel.raynal@...tlin.com> wrote:
>
> Hi Alexander,
>
> > > > btw:
> > > > Also for testing with hwsim and the missing features which currently
> > > > exist. Can we implement some user space test program which replies
> > > > (active scan) or sends periodically something out via AF_PACKET raw
> > > > and a monitor interface that should work to test if it is working?
> > >
> > > We already have all this handled, no need for extra software. You can
> > > test active and passive scans between two hwsim devices already:
> > >
> > > # iwpan dev wpan0 beacons send interval 15
> > > # iwpan dev wpan1 scan type active duration 1
> > > # iwpan dev wpan0 beacons stop
> > >
> > > or
> > >
> > > # iwpan dev wpan0 beacons send interval 1
> > > # iwpan dev wpan1 scan type passive duration 2
> > > # iwpan dev wpan0 beacons stop
> > >
> > > > Ideally we could do that very easily with scapy (not sure about their
> > > > _upstream_ 802.15.4 support). I hope I got that right that there is
> > > > still something missing but we could fake it in such a way (just for
> > > > hwsim testing).
> > >
> > > I hope the above will match your expectations.
> > >
> >
> > I need to think and read more about... in my mind is currently the
> > following question: are not coordinators broadcasting that information
> > only? Means, isn't that a job for a coordinator?
>
> My understanding right now:
> - The spec states that coordinators only can send beacons and perform
>   scans.

ok.

> - I don't yet have the necessary infrastructure to give coordinators
>   more rights than regular devices or RFDs (but 40+ patches already,
>   don't worry this is something we have in mind)
> - Right now this is the user to decide whether a device might answer
>   beacon requests or not. This will soon become more limited but it
>   greatly simplifies the logic for now.
>

There was always the idea behind it to make an "coordinator" interface
type and there is a reason for that because things e.g. filtering
becomes different than a non-coordinator interface type (known as node
interface in wpan).
At the end interface types should make a big difference in how the
"role" inside the network should be, which you can also see in
wireless as "station"/"access point" interface devices.

A non full functional device should then also not be able to act as a
coordinator e.g. it cannot create coordinator types.

However we can still make some -EOPNOTSUPP if something in a different
way should be done. This clearly breaks userspace and I am not sure if
we should worry or not worry about it in the current state of
802.15.4...

- Alex