Re: [PATCH bluetooth-next 2/2] mac802154: fix wpan mac setting while lowpan

[Alexander Aring <alex.aring@gmail.com>]

On Thu, Jul 30, 2015 at 06:17:44PM +0200, Stefan Schmidt wrote:
> Hello.
> 
> On 24/07/15 15:01, Alexander Aring wrote:
> >If we currently change the mac address inside the wpan interface while
> >we have a lowpan interface on top of the wpan interface, the mac address
> >setting doesn't reach the lowpan interface. The effect would be that the
> >IPv6 lowpan interface has the old SLAAC address and isn't working
> >anymore because the lowpan interface use in internal mechanism sometimes
> >dev->addr which is the old mac address of the wpan interface.
> >
> >This patch checks if a wpan interface belongs to lowpan interface, if
> >yes then we need to check if the lowpan interface is down and change the
> >mac address also at the lowpan interface. When the lowpan interface will
> >be set up afterwards, it will use the correct SLAAC address which based
> >on the updated mac address setting.
> >
> >Signed-off-by: Alexander Aring <alex.aring@gmail.com>
> Reviewed-by: Stefan Schmidt <stefan@osg.samsung.com>
> 
> I have a bit trouble testing it though. With iwpan we only allow to set the
> short address while the extended address is set during device registration.
> Removing this device also removes the connected lowpan device so I wonder
> where we would run into this problem. Patch is fine in any case but having

1. have running lowpan setup
2. ifdown wpan only, let lowpan up
3. change mac (extended_addr) of wpan interface
4. do it up again

-> something is wrong because the mac of lowpan isn't the same like wpan
   anymore. We have several issues, maybe we could deal with that in
   802.15.4 6LoWPAN code, but also the SLAAC address isn't right
   anymore. IPv6 can deal with this address only when the interface is
   down, because on ifup IPv6 on able interface -> the IPv6 stack will
   generate the SLAAC address then according to the mac address.

   What I mean in this case with "SLAAC" address is the standard
   link-local address "fe:80::$EUI64_ADDRESS_WITH_UE_BIT/64"

- Alex