Tobias reports that after the blamed patch, VLAN objects being added to
a bridge device are being added to all slave ports instead (swp2, swp3).

ip link add br0 type bridge vlan_filtering 1
ip link set swp2 master br0
ip link set swp3 master br0
bridge vlan add dev br0 vid 100 self

This is because the fix was too broad: we made dsa_port_offloads_netdev
say "yes, I offload the br0 bridge" for all slave ports, but we didn't
add the checks whether the switchdev object was in fact meant for the
physical port or for the bridge itself. So we are reacting on events in
a way in which we shouldn't.

The reason why the fix was too broad is because the question itself,
"does this DSA port offload this netdev", was too broad in the first
place. The solution is to disambiguate the question and separate it into
two different functions, one to be called for each switchdev attribute /
object that has an orig_dev == net_bridge (dsa_port_offloads_bridge),
and the other for orig_dev == net_bridge_port (*_offloads_bridge_port).

In the case of VLAN objects on the bridge interface, this solves the
problem because we know that VLAN objects are per bridge port and not
per bridge. And when orig_dev is equal to the net_bridge, we offload it
as a bridge, but not as a bridge port; that's how we are able to skip
reacting on those events. Note that this is compatible with future plans
to have explicit offloading of VLAN objects on the bridge interface as a
bridge port (in DSA, this signifies that we should add that VLAN towards
the CPU port).

Fixes: 99b8202b ("net: dsa: fix SWITCHDEV_ATTR_ID_BRIDGE_VLAN_FILTERING getting ignored")
Reported-by: Tobias Waldekranz <tobias@waldekranz.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: Tobias Waldekranz <tobias@waldekranz.com>
Tested-by: Tobias Waldekranz <tobias@waldekranz.com>
Signed-off-by: David S. Miller <davem@davemloft.net>