Merge branch 'mirroring-to-dsa-cpu-port'

Vladimir Oltean says:

====================
Mirroring to DSA CPU port

Users of the NXP LS1028A SoC (drivers/net/dsa/ocelot L2 switch inside)
have requested to mirror packets from the ingress of a switch port to
software. Both port-based and flow-based mirroring is required.

The simplest way I could come up with was to set up tc mirred actions
towards a dummy net_device, and make the offloading of that be accepted
by the driver. Currently, the pattern in drivers is to reject mirred
towards ports they don't know about, but I'm now permitting that,
precisely by mirroring "to the CPU".

For testers, this series depends on commit 34d35b4edbbe ("net/sched:
act_api: deny mismatched skip_sw/skip_hw flags for actions created by
classifiers") from net/main, which is absent from net-next as of the
day of posting (Oct 23). Without the bug fix it is possible to create
invalid configurations which are not rejected by the kernel.

v2:  https://lore.kernel.org/20241017165215.3709000-1-vladimir.oltean@nxp.com
RFC: https://lore.kernel.org/20240913152915.2981126-1-vladimir.oltean@nxp.com

For historical purposes, link to a much older (and much different) attempt:
https://lore.kernel.org/20191002233750.13566-1-olteanv@gmail.com
====================

Link: https://patch.msgid.link/20241023135251.1752488-1-vladimir.oltean@nxp.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>