On Thu, 25 Feb 2021 14:18:34 +0200 Vladimir Oltean wrote:

Quoting from the blamed commit:

    In promiscuous mode, it is more intuitive that all traffic is received,
    including VLAN tagged traffic. It appears that it is necessary to set
    the flag in PSIPVMR for that to be the case, so VLAN promiscuous mode is
    also temporarily enabled. On exit from promiscuous mode, the setting
    made by ethtool is restored.

Intuitive or not, there isn't any definition issued by a standards body
which says that promiscuity has anything to do with VLAN filtering - it
only has to do with accepting packets regardless of destination MAC address.

In fact people are already trying to use this misunderstanding/bug of
the enetc driver as a justification to transform promiscuity into
something it never was about: accepting every packet (maybe that would
be the "rx-all" netdev feature?):
https://lore.kernel.org/netdev/20201110153958.ci5ekor3o2ekg3ky@ipetronik.com/ (local)

So we should avoid that and delete the bogus logic in enetc.

I don't understand what you're fixing tho.

Are we trying to establish vlan-filter-on as the expected behavior?