mlxsw: spectrum_switchdev: Add locked bridge port support

mlxsw: spectrum_switchdev: Add locked bridge port support

Add locked bridge port support by reacting to changes in the
'BR_PORT_LOCKED' flag. When set, enable security checks on the local
port via the previously added SPFSR register.

When security checks are enabled, an incoming packet will trigger an FDB
lookup with the packet's source MAC and the FID it was classified to. If
an FDB entry was not found or was found to be pointing to a different
port, the packet will be dropped. Such packets increment the
"discard_ingress_general" ethtool counter. For added visibility, user
space can trap such packets to the CPU by enabling the "locked_port"
trap. Example:

 # devlink trap set pci/0000:06:00.0 trap locked_port action trap

Unlike other configurations done via bridge port flags (e.g., learning,
flooding), security checks are enabled in the device on a per-port basis
and not on a per-{port, VLAN} basis. As such, scenarios where user space
can configure different locking settings for different VLANs configured
on a port need to be vetoed. To that end, veto the following scenarios:

1. Locking is set on a bridge port that is a VLAN upper

2. Locking is set on a bridge port that has VLAN uppers

3. VLAN upper is configured on a locked bridge port

Examples:

 # bridge link set dev swp1.10 locked on
 Error: mlxsw_spectrum: Locked flag cannot be set on a VLAN upper.

 # ip link add link swp1 name swp1.10 type vlan id 10
 # bridge link set dev swp1 locked on
 Error: mlxsw_spectrum: Locked flag cannot be set on a bridge port that has VLAN uppers.

 # bridge link set dev swp1 locked on
 # ip link add link swp1 name swp1.10 type vlan id 10
 Error: mlxsw_spectrum: VLAN uppers are not supported on a locked port.

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Petr Machata <petrm@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>