On Tue, Nov 16, 2021 at 03:56:45PM +0100, Wolfgang Denk wrote: > Dear Tom, > > In message <20211116141855.GD24579@bill-the-cat> you wrote: > > > > So, to quote lib/Kconfig: > > config NET_RANDOM_ETHADDR > > bool "Random ethaddr if unset" > > help > > Selecting this will allow the Ethernet interface to function > > even when the ethaddr variable for that interface is unset. > > A new MAC address will be generated on every boot and it will > > not be added to the environment. > > This description is at least incomplete, because it makes no > difference between the persistent copy of the environment and it's > in-memory copy. For network to function, I think the MAC address > must be stored in the in-memory copy of the environment.
Well, networking has been working with NET_RANDOM_ETHADDR not updating the environment, with caveats that user display information that reads from the environment rather than ->enetaddr. In so far as the networking stack cares, ->enetaddr is what matters. We look at the environment for a MAC, and if it doesn't match the HW we use environment MAC, but warn. Now, I think RFC7042 is the current correct and relevant RFC here and it doesn't mention persistence. So I don't see a clear external authority on if locally administered MAC addresses like this should be persistent or not in this manner. > > We need either a re-spin or follow-up as we're changing the documented > > behavior. And as I mentioned in the other thread related on-going > > thread, perhaps "ethmacskip" should play a role in preserving existing > > behavior? > > We have way too many ways to do the same thing - nearly, just a > little different :-( Well, in this case I'm not sure that's the right problem to point at. We can just set ethmacskip as a bit of corner-case functionality and move on. Because honestly, the more I read this, the more I think https://patchwork.ozlabs.org/project/uboot/patch/20211115121152.3470910-1-mich...@walle.cc/ is essentially the right direction. There's no reason for 'net list' to be using the environment here when ->enetaddr is what's being used by the stack. The use case of "I want to make my locally administered MAC persist because my USB ethernet adapter lacks a MAC address" is solved via the environment already. -- Tom
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