From a9985444f2b5b6e60c7b1faeceebe58367a08915 Mon Sep 17 00:00:00 2001 From: Vladimir Oltean Date: Tue, 16 Mar 2021 13:24:15 +0200 Subject: [PATCH] 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 Signed-off-by: Vladimir Oltean Reviewed-by: Florian Fainelli Reviewed-by: Tobias Waldekranz Signed-off-by: David S. Miller --- Documentation/networking/dsa/dsa.rst | 33 +++++++++++++++++++++++++++++++++ 1 file changed, 33 insertions(+) diff --git a/Documentation/networking/dsa/dsa.rst b/Documentation/networking/dsa/dsa.rst index af604fe..e8576e8 100644 --- a/Documentation/networking/dsa/dsa.rst +++ b/Documentation/networking/dsa/dsa.rst @@ -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 ==== -- 2.7.4