mac802154: Only allow PAN controllers to process association requests

It is not very clear in the specification whether simple coordinators
are allowed or not to answer to association requests themselves. As
there is no synchronization mechanism, it is probably best to rely on
the relay feature of these coordinators and avoid processing them in
this case.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Stefan Schmidt <stefan@datenfreihafen.org>
Acked-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/linux-wpan/20231128111655.507479-4-miquel.raynal@bootlin.com

mac80254: Provide real PAN coordinator info in beacons

Sending a beacon is a way to advertise a PAN, but also ourselves as
coordinator in the PAN. There is only one PAN coordinator in a PAN, this
is the device without parent (not associated itself to an "upper"
coordinator). Instead of blindly saying that we are the PAN coordinator,
let's actually use our internal information to fill this field.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Stefan Schmidt <stefan@datenfreihafen.org>
Acked-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/linux-wpan/20231128111655.507479-2-miquel.raynal@bootlin.com

mac802154: Handle disassociation notifications from peers

Peers may decided to disassociate from us, their coordinator, in this
case they will send a disassociation notification which we must
acknowledge. If we don't, the peer device considers itself disassociated
anyway. We also need to drop the reference to this child from our
internal structures.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Stefan Schmidt <stefan@datenfreihafen.org>
Acked-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/linux-wpan/20230927181214.129346-11-miquel.raynal@bootlin.com

mac802154: Follow the number of associated devices

Track the count of associated devices. Limit the number of associations
using the value provided by the user if any. If we reach the maximum
number of associations, we tell the device we are at capacity. If the
user do not want to accept any more associations, it may specify the
value 0 to the maximum number of associations, which will lead to an
access denied error status returned to the peers trying to associate.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Stefan Schmidt <stefan@datenfreihafen.org>
Acked-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/linux-wpan/20230927181214.129346-10-miquel.raynal@bootlin.com

mac802154: Handle association requests from peers

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>
Acked-by: Stefan Schmidt <stefan@datenfreihafen.org>
Acked-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/linux-wpan/20230927181214.129346-8-miquel.raynal@bootlin.com

mac802154: Handle disassociations

Devices may decide to disassociate from their coordinator for different
reasons (device turning off, coordinator signal strength too low, etc),
the MAC layer just has to send a disassociation notification.

If the ack of the disassociation notification is not received, the
device may consider itself disassociated anyway.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Stefan Schmidt <stefan@datenfreihafen.org>
Acked-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/linux-wpan/20230927181214.129346-7-miquel.raynal@bootlin.com

mac802154: Handle associating

Joining a PAN officially goes by associating with a coordinator. This
coordinator may have been discovered thanks to the beacons it sent in
the past. Add support to the MAC layer for these associations, which
require:
- Sending an association request
- Receiving an association response

The association response contains the association status, eventually a
reason if the association was unsuccessful, and finally a short address
that we should use for intra-PAN communication from now on, if we
required one (which is the default, and not yet configurable).

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Stefan Schmidt <stefan@datenfreihafen.org>
Acked-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/linux-wpan/20230927181214.129346-5-miquel.raynal@bootlin.com

mac802154: Handle received BEACON_REQ

When performing an active scan, devices emit BEACON_REQ which
must be answered by other PANs receiving the request, unless they are
already passively sending beacons.

Answering a beacon request becomes a duty when the user tells us to send
beacons and the request provides an interval of 15.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/r/20230310145346.1397068-5-miquel.raynal@bootlin.com
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>

mac802154: Handle active scanning

Active scan support is based on the current passive scan support,
cheered up with beacon requests sent after every channel change.

Co-developed-by: David Girault <david.girault@qorvo.com>
Signed-off-by: David Girault <david.girault@qorvo.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/r/20230310145346.1397068-3-miquel.raynal@bootlin.com
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>

mac802154: Rename kfree_rcu() to kvfree_rcu_mightsleep()

The k[v]free_rcu() macro's single-argument form is deprecated.
Therefore switch to the new k[v]free_rcu_mightsleep() variant. The goal
is to avoid accidental use of the single-argument forms, which can
introduce functionality bugs in atomic contexts and latency bugs in
non-atomic contexts.

The callers are holding a mutex so the context allows blocking. Hence
using the API with a single argument will be fine, but use its new name.

There is no functionality change with this patch.

Fixes: 57588c71177f ("mac802154: Handle passive scanning")
Acked-by: Stefan Schmidt <stefan@datenfreihafen.org>
Reviewed-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>

mac802154: Fix an always true condition

At this stage we simply do not care about the delayed work value,
because active scan is not yet supported, so we can blindly queue
another work once a beacon has been sent.

It fixes a smatch warning:
mac802154_beacon_worker() warn: always true condition
'(local->beacon_interval >= 0) => (0-u32max >= 0)'

Fixes: 3accf4762734 ("mac802154: Handle basic beaconing")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/r/20230214135035.1202471-6-miquel.raynal@bootlin.com
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>

mac802154: Send beacons using the MLME Tx path

Using ieee802154_subif_start_xmit() to bypass the net queue when
sending beacons is broken because it does not acquire the
HARD_TX_LOCK(), hence not preventing datagram buffers to be smashed by
beacons upon contention situation. Using the mlme_tx helper is not the
best fit either but at least it is not buggy and has little-to-no
performance hit. More details are given in the comment explaining this
choice in the code.

Fixes: 3accf4762734 ("mac802154: Handle basic beaconing")
Reported-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/r/20230214135035.1202471-5-miquel.raynal@bootlin.com
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>

mac802154: Avoid superfluous endianness handling

When compiling scan.c with C=1, Sparse complains with:

sparse: expected unsigned short [usertype] val
sparse: got restricted __le16 [usertype] pan_id
sparse: sparse: cast from restricted __le16

sparse: expected unsigned long long [usertype] val
sparse: got restricted __le64 [usertype] extended_addr
sparse: sparse: cast from restricted __le64

The tool is right, both pan_id and extended_addr already are rightfully
defined as being __le16 and __le64 on both sides of the operations and
do not require extra endianness handling.

Fixes: 3accf4762734 ("mac802154: Handle basic beaconing")
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/r/20230130154306.114265-1-miquel.raynal@bootlin.com
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>

mac802154: Handle basic beaconing

Implement the core hooks in order to provide the softMAC layer support
for sending beacons. Coordinators may be requested to send beacons in a
beacon enabled PAN in order for the other devices around to self
discover the available PANs automatically.

Changing the channels is prohibited while a beacon operation is
ongoing.

The implementation uses a workqueue triggered at a certain interval
depending on the symbol duration for the current channel and the
interval order provided.

Sending beacons in response to a BEACON_REQ frame (ie. answering active
scans) is not yet supported.

This initial patchset has no security support (llsec).

Co-developed-by: David Girault <david.girault@qorvo.com>
Signed-off-by: David Girault <david.girault@qorvo.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/r/20230125102923.135465-3-miquel.raynal@bootlin.com
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>

mac802154: Handle passive scanning

Implement the core hooks in order to provide the softMAC layer support
for passive scans. Scans are requested by the user and can be aborted.

Changing channels manually is prohibited during scans.

The implementation uses a workqueue triggered at a certain interval
depending on the symbol duration for the current channel and the
duration order provided. More advanced drivers with internal scheduling
capabilities might require additional care but there is none mainline
yet.

Received beacons during a passive scan are processed in a work queue and
their result forwarded to the upper layer.

Active scanning is not supported yet.

Co-developed-by: David Girault <david.girault@qorvo.com>
Signed-off-by: David Girault <david.girault@qorvo.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Alexander Aring <aahringo@redhat.com>
Link: https://lore.kernel.org/r/20230103165644.432209-7-miquel.raynal@bootlin.com
Signed-off-by: Stefan Schmidt <stefan@datenfreihafen.org>