Bug#812575: udev: predictable network device names fails for USB devices without a permanent hw address

[Michael Biebl]

Hi Bjørn,

On Mon, 25 Jan 2016 09:27:31 +0100 =?utf-8?q?Bj=C3=B8rn_Mork?=
<bjorn at mork.no> wrote:
> I just noticed that the new "predictable" network device names logic
> fails in a most ugly way with USB devices with no permanent mac
> address:
> 
>  [   10.989584] qmi_wwan 6-4:1.10 wwx2ac56637bccb: renamed from wwan1
>  [   11.019362] qmi_wwan 6-4:1.8 rename4: renamed from wwan0
> 
> 
> There are two issues here:
> 
> 1) the name is derived from a random mac address, which is regenerated
>    on each boot.  Note that the address does have the 'local' bit set:
>     2a:c5:66:37:bc:cb
> 
> 2) there are two such network interfaces present. The 'usbnet' driver
>   infrastructure will generate an address on module init and reuse
>   the very same address for every USB device needing one. Naturally,
>   trying to name more than one interface after the same address fails,
>   and you end up with an even uglier 'rename4' device name...

That sounds like a bug in the driver to me.


> The old persistent network device logic used to avoid mapping against
> locally administered mac addresses.  This logic needs to be kept for
> the new  "predictable" names too.  Anything else is a regression.

Is there a way to detect such "locally administered mac addresses"?

> But even with this in place, the new logic should be prepared for
> duplicate mac addresses.  There are plenty of USB devices with non-
> unique mac addresses out there.  It's more of a rule than an exception
> for GSM/LTE modem devices...

Please consider raising this issue upstream and filing a bug at
https://github.com/systemd/systemd/issues/new


Regards,
Michael



-- 
Why is it that all of the instruments seeking intelligent life in the
universe are pointed away from Earth?

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