Re: [PATCH v4 net-next 11/15] net: bridge: switchdev: allow the TX data plane forwarding to be offloaded

[Florian Fainelli <f.fainelli@gmail.com>]

On 7/18/2021 2:44 PM, Vladimir Oltean wrote:
> From: Tobias Waldekranz <tobias@waldekranz.com>
> 
> Allow switchdevs to forward frames from the CPU in accordance with the
> bridge configuration in the same way as is done between bridge
> ports. This means that the bridge will only send a single skb towards
> one of the ports under the switchdev's control, and expects the driver
> to deliver the packet to all eligible ports in its domain.
> 
> Primarily this improves the performance of multicast flows with
> multiple subscribers, as it allows the hardware to perform the frame
> replication.
> 
> The basic flow between the driver and the bridge is as follows:
> 
> - When joining a bridge port, the switchdev driver calls
>    switchdev_bridge_port_offload() with tx_fwd_offload = true.
> 
> - The bridge sends offloadable skbs to one of the ports under the
>    switchdev's control using skb->offload_fwd_mark = true.
> 
> - The switchdev driver checks the skb->offload_fwd_mark field and lets
>    its FDB lookup select the destination port mask for this packet.
> 
> v1->v2:
> - convert br_input_skb_cb::fwd_hwdoms to a plain unsigned long
> - introduce a static key "br_switchdev_fwd_offload_used" to minimize the
>    impact of the newly introduced feature on all the setups which don't
>    have hardware that can make use of it
> - introduce a check for nbp->flags & BR_FWD_OFFLOAD to optimize cache
>    line access
> - reorder nbp_switchdev_frame_mark_accel() and br_handle_vlan() in
>    __br_forward()
> - do not strip VLAN on egress if forwarding offload on VLAN-aware bridge
>    is being used
> - propagate errors from .ndo_dfwd_add_station() if not EOPNOTSUPP
> 
> v2->v3:
> - replace the solution based on .ndo_dfwd_add_station with a solution
>    based on switchdev_bridge_port_offload
> - rename BR_FWD_OFFLOAD to BR_TX_FWD_OFFLOAD
> v3->v4: rebase
> 
> Signed-off-by: Tobias Waldekranz <tobias@waldekranz.com>
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>

Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
-- 
Florian