This is the implementation of CFM netlink configuration
get information interface.

Add new nested netlink attributes. These attributes are used by the
user space to get configuration information.

GETLINK:
    Request filter RTEXT_FILTER_CFM_CONFIG:
    Indicating that CFM configuration information must be delivered.

    IFLA_BRIDGE_CFM:
        Points to the CFM information.

    IFLA_BRIDGE_CFM_MEP_CREATE_INFO:
        This indicate that MEP instance create parameters are following.
    IFLA_BRIDGE_CFM_MEP_CONFIG_INFO:
        This indicate that MEP instance config parameters are following.
    IFLA_BRIDGE_CFM_CC_CONFIG_INFO:
        This indicate that MEP instance CC functionality
        parameters are following.
    IFLA_BRIDGE_CFM_CC_RDI_INFO:
        This indicate that CC transmitted CCM PDU RDI
        parameters are following.
    IFLA_BRIDGE_CFM_CC_CCM_TX_INFO:
        This indicate that CC transmitted CCM PDU parameters are
        following.
    IFLA_BRIDGE_CFM_CC_PEER_MEP_INFO:
        This indicate that the added peer MEP IDs are following.

CFM nested attribute has the following attributes in next level.

GETLINK RTEXT_FILTER_CFM_CONFIG:
    IFLA_BRIDGE_CFM_MEP_CREATE_INSTANCE:
        The created MEP instance number.
        The type is u32.
    IFLA_BRIDGE_CFM_MEP_CREATE_DOMAIN:
        The created MEP domain.
        The type is u32 (br_cfm_domain).
        It must be BR_CFM_PORT.
        This means that CFM frames are transmitted and received
        directly on the port - untagged. Not in a VLAN.
    IFLA_BRIDGE_CFM_MEP_CREATE_DIRECTION:
        The created MEP direction.
        The type is u32 (br_cfm_mep_direction).
        It must be BR_CFM_MEP_DIRECTION_DOWN.
        This means that CFM frames are transmitted and received on
        the port. Not in the bridge.
    IFLA_BRIDGE_CFM_MEP_CREATE_IFINDEX:
        The created MEP residence port ifindex.
        The type is u32 (ifindex).

    IFLA_BRIDGE_CFM_MEP_DELETE_INSTANCE:
        The deleted MEP instance number.
        The type is u32.

    IFLA_BRIDGE_CFM_MEP_CONFIG_INSTANCE:
        The configured MEP instance number.
        The type is u32.
    IFLA_BRIDGE_CFM_MEP_CONFIG_UNICAST_MAC:
        The configured MEP unicast MAC address.
        The type is 6*u8 (array).
        This is used as SMAC in all transmitted CFM frames.
    IFLA_BRIDGE_CFM_MEP_CONFIG_MDLEVEL:
        The configured MEP unicast MD level.
        The type is u32.
        It must be in the range 1-7.
        No CFM frames are passing through this MEP on lower levels.
    IFLA_BRIDGE_CFM_MEP_CONFIG_MEPID:
        The configured MEP ID.
        The type is u32.
        It must be in the range 0-0x1FFF.
        This MEP ID is inserted in any transmitted CCM frame.

    IFLA_BRIDGE_CFM_CC_CONFIG_INSTANCE:
        The configured MEP instance number.
        The type is u32.
    IFLA_BRIDGE_CFM_CC_CONFIG_ENABLE:
        The Continuity Check (CC) functionality is enabled or disabled.
        The type is u32 (bool).
    IFLA_BRIDGE_CFM_CC_CONFIG_EXP_INTERVAL:
        The CC expected receive interval of CCM frames.
        The type is u32 (br_cfm_ccm_interval).
        This is also the transmission interval of CCM frames when enabled.
    IFLA_BRIDGE_CFM_CC_CONFIG_EXP_MAID:
        The CC expected receive MAID in CCM frames.
        The type is CFM_MAID_LENGTH*u8.
        This is MAID is also inserted in transmitted CCM frames.

    IFLA_BRIDGE_CFM_CC_PEER_MEP_INSTANCE:
        The configured MEP instance number.
        The type is u32.
    IFLA_BRIDGE_CFM_CC_PEER_MEPID:
        The CC Peer MEP ID added.
        The type is u32.
        When a Peer MEP ID is added and CC is enabled it is expected to
        receive CCM frames from that Peer MEP.

    IFLA_BRIDGE_CFM_CC_RDI_INSTANCE:
        The configured MEP instance number.
        The type is u32.
    IFLA_BRIDGE_CFM_CC_RDI_RDI:
        The RDI that is inserted in transmitted CCM PDU.
        The type is u32 (bool).

    IFLA_BRIDGE_CFM_CC_CCM_TX_INSTANCE:
        The configured MEP instance number.
        The type is u32.
    IFLA_BRIDGE_CFM_CC_CCM_TX_DMAC:
        The transmitted CCM frame destination MAC address.
        The type is 6*u8 (array).
        This is used as DMAC in all transmitted CFM frames.
    IFLA_BRIDGE_CFM_CC_CCM_TX_SEQ_NO_UPDATE:
        The transmitted CCM frame update (increment) of sequence
        number is enabled or disabled.
        The type is u32 (bool).
    IFLA_BRIDGE_CFM_CC_CCM_TX_PERIOD:
        The period of time where CCM frame are transmitted.
        The type is u32.
        The time is given in seconds. SETLINK IFLA_BRIDGE_CFM_CC_CCM_TX
        must be done before timeout to keep transmission alive.
        When period is zero any ongoing CCM frame transmission
        will be stopped.
    IFLA_BRIDGE_CFM_CC_CCM_TX_IF_TLV:
        The transmitted CCM frame update with Interface Status TLV
        is enabled or disabled.
        The type is u32 (bool).
    IFLA_BRIDGE_CFM_CC_CCM_TX_IF_TLV_VALUE:
        The transmitted Interface Status TLV value field.
        The type is u8.
    IFLA_BRIDGE_CFM_CC_CCM_TX_PORT_TLV:
        The transmitted CCM frame update with Port Status TLV is enabled
        or disabled.
        The type is u32 (bool).
    IFLA_BRIDGE_CFM_CC_CCM_TX_PORT_TLV_VALUE:
        The transmitted Port Status TLV value field.
        The type is u8.
Signed-off-by: Henrik Bjoernlund  <henrik.bjoernlund@microchip.com>
Reviewed-by: Horatiu Vultur  <horatiu.vultur@microchip.com>
Acked-by: Nikolay Aleksandrov <nikolay@nvidia.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>