netdev - Re: [PATCH wpan-next 17/20] net: ieee802154: Handle limited devices with only datagram support

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Date:   Fri, 19 Aug 2022 19:13:15 +0200
From:   Miquel Raynal <miquel.raynal@...tlin.com>
To:     Alexander Aring <aahringo@...hat.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 17/20] net: ieee802154: Handle limited devices
 with only datagram support

Hi Alexander,

aahringo@...hat.com wrote on Thu, 14 Jul 2022 23:16:33 -0400:

> Hi,
> 
> On Fri, Jul 1, 2022 at 10:37 AM Miquel Raynal <miquel.raynal@...tlin.com> wrote:
> >
> > Some devices, like HardMAC ones can be a bit limited in the way they
> > handle mac commands. In particular, they might just not support it at
> > all and instead only be able to transmit and receive regular data
> > packets. In this case, they cannot be used for any of the internal
> > management commands that we have introduced so far and must be flagged
> > accordingly.
> >
> > Signed-off-by: Miquel Raynal <miquel.raynal@...tlin.com>
> > ---
> >  include/net/cfg802154.h   | 3 +++
> >  net/ieee802154/nl802154.c | 6 ++++++
> >  2 files changed, 9 insertions(+)
> >
> > diff --git a/include/net/cfg802154.h b/include/net/cfg802154.h
> > index d6ff60d900a9..20ac4df9dc7b 100644
> > --- a/include/net/cfg802154.h
> > +++ b/include/net/cfg802154.h
> > @@ -178,12 +178,15 @@ wpan_phy_cca_cmp(const struct wpan_phy_cca *a, const struct wpan_phy_cca *b)
> >   *     setting.
> >   * @WPAN_PHY_FLAG_STATE_QUEUE_STOPPED: Indicates that the transmit queue was
> >   *     temporarily stopped.
> > + * @WPAN_PHY_FLAG_DATAGRAMS_ONLY: Indicates that transceiver is only able to
> > + *     send/receive datagrams.
> >   */
> >  enum wpan_phy_flags {
> >         WPAN_PHY_FLAG_TXPOWER           = BIT(1),
> >         WPAN_PHY_FLAG_CCA_ED_LEVEL      = BIT(2),
> >         WPAN_PHY_FLAG_CCA_MODE          = BIT(3),
> >         WPAN_PHY_FLAG_STATE_QUEUE_STOPPED = BIT(4),
> > +       WPAN_PHY_FLAG_DATAGRAMS_ONLY    = BIT(5),
> >  };
> >
> >  struct wpan_phy {
> > diff --git a/net/ieee802154/nl802154.c b/net/ieee802154/nl802154.c
> > index 00b03c33e826..b31a0bd36b08 100644
> > --- a/net/ieee802154/nl802154.c
> > +++ b/net/ieee802154/nl802154.c
> > @@ -1404,6 +1404,9 @@ static int nl802154_trigger_scan(struct sk_buff *skb, struct genl_info *info)
> >         if (wpan_dev->iftype == NL802154_IFTYPE_MONITOR)
> >                 return -EPERM;
> >
> > +       if (wpan_phy->flags & WPAN_PHY_FLAG_DATAGRAMS_ONLY)
> > +               return -EOPNOTSUPP;
> > +  
> 
> for doing a scan it's also required to turn the transceiver into
> promiscuous mode, right?
> 
> There is currently a flag if a driver supports promiscuous mode or
> not... I am not sure if all drivers have support for it. For me it
> looks like a mandatory feature but I am not sure if every driver
> supports it.
> We have a similar situation with acknowledge retransmit handling...
> some transceivers can't handle it and for normal dataframes we have a
> default behaviour that we don't set it. However sometimes it's
> required by the spec, then we can't do anything here.
> 
> I think we should check on it but we should plan to drop this flag if
> promiscuous mode is supported or not.

Yes, you are right, I should check this flag is set, I will do it at
the creation of the MONITOR interface, which anyway does not make sense
if the device has no filtering support (promiscuous being a very
standard one, but, as you said below, will later be replaced by some
more advanced levels).

> I also think that the
> promiscuous driver_ops should be removed and moved as a parameter for
> start() driver_ops to declare which "receive mode" should be
> enabled... but we can do that in due course.

Agreed.

Thanks,
Miquèl