netdev - RE: question on random MAC in usbnet

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Message-ID: <64dfec9e75a744cf8e7f50807140ba9a@AcuMS.aculab.com>
Date: Sun, 19 Nov 2023 11:09:33 +0000
From: David Laight <David.Laight@...LAB.COM>
To: 'Bjørn Mork' <bjorn@...k.no>, Oliver Neukum
	<oneukum@...e.com>
CC: "netdev@...r.kernel.org" <netdev@...r.kernel.org>, USB list
	<linux-usb@...r.kernel.org>
Subject: RE: question on random MAC in usbnet

From: Bjørn Mork
> Sent: 16 November 2023 11:32
...
> > Do you think that behavior should be changed to using
> > a separate random MAC for each device that requires it?
> 
> I'm in favour.
> 
> I could be wrong, but I don't expect anything to break if we did that.
> The current static address comes from eth_random_addr() in any case, so
> the end result as seen from the mini drivers should be identical.  The
> difference will be seen in userspace and surrounding equipment, And
> those should be for the better.

It might cause grief when a USB device 'bounces' [1].
At the moment it will pick up the same 'random' MAC address.
But afterwards it will change.

So you might want to save the MAC on device removal and
re-use it on the next insert.

[1] We ended up putting the USB interface inside a 'bond'
in order to stop the interface everything was using
randomly disappearing due to common-mode noise on the
USB data lines causing a disconnect.

	David

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