Re: [PATCH wpan-next 07/11] mac802154: Handle association requests from peers

[Miquel Raynal <miquel.raynal@bootlin.com>]

Hi Alexander,

aahringo@redhat.com wrote on Sat, 3 Jun 2023 07:28:25 -0400:

> Hi,
> 
> On Thu, Jun 1, 2023 at 11:50 AM Miquel Raynal <miquel.raynal@bootlin.com> wrote:
> >
> > Coordinators may have to handle association requests from peers which
> > want to join the PAN. The logic involves:
> > - Acknowledging the request (done by hardware)
> > - If requested, a random short address that is free on this PAN should
> >   be chosen for the device.
> > - Sending an association response with the short address allocated for
> >   the peer and expecting it to be ack'ed.
> >
> > If anything fails during this procedure, the peer is considered not
> > associated.
> >
> > Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
> > ---
> >  include/net/cfg802154.h         |   7 ++
> >  include/net/ieee802154_netdev.h |   6 ++
> >  net/ieee802154/core.c           |   7 ++
> >  net/ieee802154/pan.c            |  27 ++++++
> >  net/mac802154/ieee802154_i.h    |   2 +
> >  net/mac802154/rx.c              |   8 ++
> >  net/mac802154/scan.c            | 147 ++++++++++++++++++++++++++++++++
> >  7 files changed, 204 insertions(+)
> >
> > diff --git a/include/net/cfg802154.h b/include/net/cfg802154.h
> > index 01bc6c2da7b9..4404072365e7 100644
> > --- a/include/net/cfg802154.h
> > +++ b/include/net/cfg802154.h
> > @@ -582,4 +582,11 @@ struct ieee802154_pan_device *
> >  cfg802154_device_is_child(struct wpan_dev *wpan_dev,
> >                           struct ieee802154_addr *target);
> >
> > +/**
> > + * cfg802154_get_free_short_addr - Get a free address among the known devices
> > + * @wpan_dev: the wpan device
> > + * @return: a random short address expectedly unused on our PAN
> > + */
> > +__le16 cfg802154_get_free_short_addr(struct wpan_dev *wpan_dev);
> > +
> >  #endif /* __NET_CFG802154_H */
> > diff --git a/include/net/ieee802154_netdev.h b/include/net/ieee802154_netdev.h
> > index 16194356cfe7..4de858f9929e 100644
> > --- a/include/net/ieee802154_netdev.h
> > +++ b/include/net/ieee802154_netdev.h
> > @@ -211,6 +211,12 @@ struct ieee802154_association_req_frame {
> >         struct ieee802154_assoc_req_pl assoc_req_pl;
> >  };
> >
> > +struct ieee802154_association_resp_frame {
> > +       struct ieee802154_hdr mhr;
> > +       struct ieee802154_mac_cmd_pl mac_pl;
> > +       struct ieee802154_assoc_resp_pl assoc_resp_pl;
> > +};
> > +
> >  struct ieee802154_disassociation_notif_frame {
> >         struct ieee802154_hdr mhr;
> >         struct ieee802154_mac_cmd_pl mac_pl;
> > diff --git a/net/ieee802154/core.c b/net/ieee802154/core.c
> > index 8bf01bb7e858..39674db64336 100644
> > --- a/net/ieee802154/core.c
> > +++ b/net/ieee802154/core.c
> > @@ -200,11 +200,18 @@ EXPORT_SYMBOL(wpan_phy_free);
> >
> >  static void cfg802154_free_peer_structures(struct wpan_dev *wpan_dev)
> >  {
> > +       struct ieee802154_pan_device *child, *tmp;
> > +
> >         mutex_lock(&wpan_dev->association_lock);
> >
> >         if (wpan_dev->parent)
> >                 kfree(wpan_dev->parent);
> >
> > +       list_for_each_entry_safe(child, tmp, &wpan_dev->children, node) {
> > +               list_del(&child->node);
> > +               kfree(child);
> > +       }
> > +
> >         wpan_dev->association_generation++;
> >
> >         mutex_unlock(&wpan_dev->association_lock);
> > diff --git a/net/ieee802154/pan.c b/net/ieee802154/pan.c
> > index 477e8dad0cf0..7756906c201d 100644
> > --- a/net/ieee802154/pan.c
> > +++ b/net/ieee802154/pan.c
> > @@ -66,3 +66,30 @@ cfg802154_device_is_child(struct wpan_dev *wpan_dev,
> >         return NULL;
> >  }
> >  EXPORT_SYMBOL_GPL(cfg802154_device_is_child);
> > +
> > +__le16 cfg802154_get_free_short_addr(struct wpan_dev *wpan_dev)
> > +{
> > +       struct ieee802154_pan_device *child;
> > +       __le16 addr;
> > +
> > +       lockdep_assert_held(&wpan_dev->association_lock);
> > +
> > +       do {
> > +               get_random_bytes(&addr, 2);  
> 
> This is combined with the max associations setting? I am not sure if
> this is the best way to get free values from a u16 value where we have
> some data structure of "given" addresses to a node. I recently was
> looking into idr/xarray data structure... maybe we can use something
> from there.

I actually thought about using an increasing index, but the pseudo
random generator seemed appropriate because of its "unpredictability",
but there is not real use for that (besides maybe testing purposes). I
can definitely switch to another solution.

Thanks,
Miquèl