How is the Ethernet MAC address for usb0 defined?

Mikko Rauhala mjrauhal at cc.helsinki.fi
Tue Aug 7 23:17:57 CEST 2007


ti, 2007-08-07 kello 16:56 -0400, Dr. H. Nikolaus Schaller kirjoitti:
> Am 07.08.2007 um 16:35 schrieb Mikko Rauhala:
> > Incidentally, using the Bluetooth MAC directly wouldn't be such a  
> > silly idea. Different interfaces on the same host can share the same MAC  
> > just
> 
> Hm. I remember that the only unique identifier in the world is the 48  
> bit Ethernet address...

...for the host, sure :)

> > 'course, you couldn't hook two interfaces with the same
> > advertised MAC onto the same LAN segment, but that's not really a
> > relevant limitation here.
> 
> Are you sure? The same computer could be used to connect through
> USB and BT in parallel.

Interface-spesific IP-based routing can take care about which physical
interface to use.

> IMHO a better solution would be to rehash (MD5, CRC48 or something) the
> Bluetooth MAC - so that probability of conflicts is approx. 2^-48

There is a process for generating random MACs and you're not meant to
use just whichever one. But sure, you can generate a valid
"well-behaved" random USB MAC from the BT MAC. Perhaps this _would_ in
practice be a better idea, since some systems just might get confused
otherwise.

Luckily as Michael explained this is doable in userspace however you do
it. Have a /etc file that fixes the USB interface ethernet address, and
if it doesn't exist, generate it somehow (copy BT MAC or hash and mangle
it so that it becomes a well-behaved random MAC, whatever you want).

-- 
Mikko Rauhala   - mjr at iki.fi     - <URL:http://www.iki.fi/mjr/>
Transhumanist   - WTA member     - <URL:http://www.transhumanism.org/>
Singularitarian - SIAI supporter - <URL:http://www.singinst.org/>




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