[PATCH] defconfig: espressobin: enable NET_RANDOM_ETHADDR

[Tom Rini]

On Fri, Sep 11, 2020 at 06:47:02PM +0200, Andre Heider wrote:
> On 11/09/2020 18:22, Marek Behún wrote:
> > On Fri, 11 Sep 2020 17:52:26 +0200
> > Andre Heider <a.heider at gmail.com> wrote:
> > 
> > > Hi Marek,
> > > 
> > > On 11/09/2020 13:55, Marek Behún wrote:
> > > > On Wed, 9 Sep 2020 00:38:31 +0200 Pali Rohár <pali at kernel.org>
> > > > wrote:
> > > > > On Tuesday 08 September 2020 08:52:56 Tom Rini wrote:
> > > > > > Note that when CONFIG_NET_RANDOM_ETHADDR is set, we only use a
> > > > > > random MAC address when we haven't found one either on the
> > > > > > hardware or environment.
> > > > > 
> > > > > I know.
> > > > > > It also prints a warning that you are using a random MAC,
> > > > > > so if it's documented on how to recover the real MAC a user should
> > > > > > see that warning and fix it.
> > > > > 
> > > > > In case you did backup of MAC address or you have MAC address
> > > > > printed on sticker, you can restore it. If you loaded distribution
> > > > > U-Boot which erase MAC address and you have not did any backup,
> > > > > then your MAC address is forever lost.
> > > > 
> > > > On Turris MOX we write the MAC address into OTP of the SOC during
> > > > manufacturing.
> > > > 
> > > > It is possible to write code that burns the MAC address into OTP, I
> > > > consider this a better option than enabling random MAC address.
> > > > 
> > > > Maybe we can enable random MAC address, and if MAC address is not
> > > > found in environment nor OTP, issue a warning, something like
> > > >     "WARNING: MAC address lost, please burn the MAC address of your
> > > > device to OTP with command xyz"
> > > > 
> > > > What do you think?
> > > 
> > > if there's a mac stored in otp during manufacturing, that's of course
> > > the best solution. There's no need for CONFIG_NET_RANDOM_ETHADDR
> > > then. But globalscale does not do that.
> > > 
> > > Doing it afterwards, so u-boot claiming some otp space for itself,
> > > and instructing the user how to write to it sounds too
> > > dangerous/error-prone.
> > > 
> > > For me CONFIG_NET_RANDOM_ETHADDR is a knob that should be enabled if
> > > there's no mac address stored in a sane way (where saving it just to
> > > an u-boot env during manufacturing doesn't count as sane, especially
> > > if the vendor moves the spi env offset around in a firmware update).
> > > 
> > > So I think CONFIG_NET_RANDOM_ETHADDR is enough.
> > > 
> > 
> > I understand Pali's concerns, though.
> > 
> > The thing is that if we enable CONFIG_NET_RANDOM_ETHADDR by default,
> > many users that have managed to wipe their env won't care about that
> > they are using randomly generated MAC address and won't solve the issue,
> > which is again the spirit of correctly configure networks.
> > 
> > If we do not enable CONFIG_NET_RANDOM_ETHADDR, the worst that can
> > happen is that the device won't boot from network. This will force the
> > users to solve the issue, which is not that hard
> >    setenv ethaddr aa:bb:cc:dd:ee:ff (address from the sticker)
> >    saveenv
> > If the users boots from SD/eMMC/SATA/USB, Linux won't have problem with
> > network, since it will generate random MAC address anyway.
> 
> Good point, so let's assume the user doesn't have a mac stored.
> 
> Without CONFIG_NET_RANDOM_ETHADDR:
> * u-boot refuses to do anything network related
> * Linux generates a random mac, network works
> 
> With CONFIG_NET_RANDOM_ETHADDR:
> * u-boot generates a random mac, network works
> * Linux uses the same random mac, passed on from u-boot throught the
> device-tree, network works
> 
> It's still random, but at least it's consistent ;)

It's also only used when we cannot find the MAC.  At the end of the day,
the final decision here is Konstantin's (as the listed maintainer).  I
personally think enabling the option is good given the apparent number
of ways the real MAC will have been lost from SW, but if the maintainer
wants to instead opt for a verbose failure message, that's fine too.

-- 
Tom
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