Commit a9985444 authored by Vladimir Oltean's avatar Vladimir Oltean Committed by David S. Miller
Browse files

Documentation: networking: dsa: add paragraph for the LAG offload 



Add a short summary of the methods that a driver writer must implement
for offloading a link aggregation group, and what is still missing.

Cc: Tobias Waldekranz <tobias@waldekranz.com>
Signed-off-by: default avatarVladimir Oltean <vladimir.oltean@nxp.com>
Reviewed-by: default avatarFlorian Fainelli <f.fainelli@gmail.com>
Reviewed-by: default avatarTobias Waldekranz <tobias@waldekranz.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 8411abbc

Documentation/networking/dsa/dsa.rst

+33 −0
Original line number Diff line number Diff line
@@ -724,6 +724,39 @@ Bridge VLAN filtering 
  function that the driver has to call for each MAC address known to be behind

  the given port. A switchdev object is used to carry the VID and MDB info.



Link aggregation

----------------



Link aggregation is implemented in the Linux networking stack by the bonding

and team drivers, which are modeled as virtual, stackable network interfaces.

DSA is capable of offloading a link aggregation group (LAG) to hardware that

supports the feature, and supports bridging between physical ports and LAGs,

as well as between LAGs. A bonding/team interface which holds multiple physical

ports constitutes a logical port, although DSA has no explicit concept of a

logical port at the moment. Due to this, events where a LAG joins/leaves a

bridge are treated as if all individual physical ports that are members of that

LAG join/leave the bridge. Switchdev port attributes (VLAN filtering, STP

state, etc) and objects (VLANs, MDB entries) offloaded to a LAG as bridge port

are treated similarly: DSA offloads the same switchdev object / port attribute

on all members of the LAG. Static bridge FDB entries on a LAG are not yet

supported, since the DSA driver API does not have the concept of a logical port

ID.



- ``port_lag_join``: function invoked when a given switch port is added to a

  LAG. The driver may return ``-EOPNOTSUPP``, and in this case, DSA will fall

  back to a software implementation where all traffic from this port is sent to

  the CPU.

- ``port_lag_leave``: function invoked when a given switch port leaves a LAG

  and returns to operation as a standalone port.

- ``port_lag_change``: function invoked when the link state of any member of

  the LAG changes, and the hashing function needs rebalancing to only make use

  of the subset of physical LAG member ports that are up.



Drivers that benefit from having an ID associated with each offloaded LAG

can optionally populate ``ds->num_lag_ids`` from the ``dsa_switch_ops::setup``

method. The LAG ID associated with a bonding/team interface can then be

retrieved by a DSA switch driver using the ``dsa_lag_id`` function.



TODO

====