diff options
| -rw-r--r-- | Documentation/networking/switchdev.rst | 47 |
1 files changed, 35 insertions, 12 deletions
diff --git a/Documentation/networking/switchdev.rst b/Documentation/networking/switchdev.rst index 016531a3d471..1b56367d85ad 100644 --- a/Documentation/networking/switchdev.rst +++ b/Documentation/networking/switchdev.rst @@ -181,18 +181,41 @@ To offloading L2 bridging, the switchdev driver/device should support: Static FDB Entries ^^^^^^^^^^^^^^^^^^ -The switchdev driver should implement ndo_fdb_add, ndo_fdb_del and ndo_fdb_dump -to support static FDB entries installed to the device. Static bridge FDB -entries are installed, for example, using iproute2 bridge cmd:: - - bridge fdb add ADDR dev DEV [vlan VID] [self] - -The driver should use the helper switchdev_port_fdb_xxx ops for ndo_fdb_xxx -ops, and handle add/delete/dump of SWITCHDEV_OBJ_ID_PORT_FDB object using -switchdev_port_obj_xxx ops. - -XXX: what should be done if offloading this rule to hardware fails (for -example, due to full capacity in hardware tables) ? +A driver which implements the ``ndo_fdb_add``, ``ndo_fdb_del`` and +``ndo_fdb_dump`` operations is able to support the command below, which adds a +static bridge FDB entry:: + + bridge fdb add dev DEV ADDRESS [vlan VID] [self] static + +(the "static" keyword is non-optional: if not specified, the entry defaults to +being "local", which means that it should not be forwarded) + +The "self" keyword (optional because it is implicit) has the role of +instructing the kernel to fulfill the operation through the ``ndo_fdb_add`` +implementation of the ``DEV`` device itself. If ``DEV`` is a bridge port, this +will bypass the bridge and therefore leave the software database out of sync +with the hardware one. + +To avoid this, the "master" keyword can be used:: + + bridge fdb add dev DEV ADDRESS [vlan VID] master static + +The above command instructs the kernel to search for a master interface of +``DEV`` and fulfill the operation through the ``ndo_fdb_add`` method of that. +This time, the bridge generates a ``SWITCHDEV_FDB_ADD_TO_DEVICE`` notification +which the port driver can handle and use it to program its hardware table. This +way, the software and the hardware database will both contain this static FDB +entry. + +Note: for new switchdev drivers that offload the Linux bridge, implementing the +``ndo_fdb_add`` and ``ndo_fdb_del`` bridge bypass methods is strongly +discouraged: all static FDB entries should be added on a bridge port using the +"master" flag. The ``ndo_fdb_dump`` is an exception and can be implemented to +visualize the hardware tables, if the device does not have an interrupt for +notifying the operating system of newly learned/forgotten dynamic FDB +addresses. In that case, the hardware FDB might end up having entries that the +software FDB does not, and implementing ``ndo_fdb_dump`` is the only way to see +them. Note: by default, the bridge does not filter on VLAN and only bridges untagged traffic. To enable VLAN support, turn on VLAN filtering:: |