Hi Alexander,
aahringo@xxxxxxxxxx wrote on Sun, 24 Sep 2023 20:13:34 -0400:
> Hi,
>
> On Fri, Sep 22, 2023 at 11:51 AM Miquel Raynal
> <miquel.raynal@xxxxxxxxxxx> 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@xxxxxxxxxxx>
> > ---
> > include/net/cfg802154.h | 7 ++
> > include/net/ieee802154_netdev.h | 6 ++
> > net/ieee802154/core.c | 7 ++
> > net/ieee802154/pan.c | 30 +++++++
> > net/mac802154/ieee802154_i.h | 2 +
> > net/mac802154/rx.c | 8 ++
> > net/mac802154/scan.c | 142 ++++++++++++++++++++++++++++++++
> > 7 files changed, 202 insertions(+)
> >
> > diff --git a/include/net/cfg802154.h b/include/net/cfg802154.h
> > index 9b036ab20079..c844ae63bc04 100644
> > --- a/include/net/cfg802154.h
> > +++ b/include/net/cfg802154.h
> > @@ -583,4 +583,11 @@ 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 a08d75dd56ad..1670a71327a7 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);
> >
> > kfree(wpan_dev->parent);
> > wpan_dev->parent = NULL;
> >
> > + list_for_each_entry_safe(child, tmp, &wpan_dev->children, node) {
> > + list_del(&child->node);
> > + kfree(child);
> > + }
> > +
> > mutex_unlock(&wpan_dev->association_lock);
> > }
> >
> > diff --git a/net/ieee802154/pan.c b/net/ieee802154/pan.c
> > index 9e1f1973c294..e99c64054dcb 100644
> > --- a/net/ieee802154/pan.c
> > +++ b/net/ieee802154/pan.c
> > @@ -73,3 +73,33 @@ 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);
> > + if (addr == cpu_to_le16(IEEE802154_ADDR_SHORT_BROADCAST) ||
> > + addr == cpu_to_le16(IEEE802154_ADDR_SHORT_UNSPEC))
> > + continue;
> > +
> > + if (wpan_dev->short_addr == addr)
> > + continue;
> > +
> > + if (wpan_dev->parent && wpan_dev->parent->short_addr == addr)
> > + continue;
> > +
> > + list_for_each_entry(child, &wpan_dev->children, node)
> > + if (child->short_addr == addr)
> > + continue;
> > +
> > + break;
> > + } while (1);
> > +
>
> I still believe that this random 2 bytes and check if it's already
> being used is wrong here. We need something to use the next free
> available number according to the data we are storing here.
This issue I still have in mind is when you have this typology:
device A -------> device B --------> device C <-------- device D
(leaf) (coord) (PAN coord) (leaf)
B associates with C
A associates with B
D associates with C
If B and C run Linux's stack, they will always have the same short
address. Yes this can be handled (realignment procedure). But any time
this happens, you'll have a load of predictable realignments when A and
D get in range with B or C.
> However it is acceptable and can be changed later...
Ok.
Thanks,
Miquèl
