On Tue, Mar 26, 2019 at 11:08:36AM +0100, Jiri Pirko wrote:

I don't think we should put permaddr if driver did not set it. 2
solutions:
1) provide a helper that driver will use to set the perm_addr. This
   helper sets a "valid bit". Then you only put IFLA_PERM_ADDRESS
   in case the "valid bit" is set.
2) Assuming that no driver would set permaddr to all zeroes,
   don't put IFLA_PERM_ADDRESS in case permadd is all zeroes.

I already replied to similar suggestion in v4 discussion:

  http://patchwork.ozlabs.org/patch/1060164/#2117512

But I don't have really strong opinion about this. The problem with not
being able to distinguish between "no/unknown permanent address" and
"old kernel not providing the information" is going to become less
important over time.

Michal