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SubjectRe: [RFC net-next v2 1/4] net: dsa: mt7530: enable assisted learning on CPU port
On Sun, Aug 01, 2021 at 03:10:19AM +0800, DENG Qingfang wrote:
> Consider the following bridge configuration, where bond0 is not
> offloaded:
>
> +-- br0 --+
> / / | \
> / / | \
> / | | bond0
> / | | / \
> swp0 swp1 swp2 swp3 swp4
> . . .
> . . .
> A B C
>
> Address learning is enabled on offloaded ports (swp0~2) and the CPU
> port, so when client A sends a packet to C, the following will happen:
>
> 1. The switch learns that client A can be reached at swp0.
> 2. The switch probably already knows that client C can be reached at the
> CPU port, so it forwards the packet to the CPU.
> 3. The bridge core knows client C can be reached at bond0, so it
> forwards the packet back to the switch.
> 4. The switch learns that client A can be reached at the CPU port.
> 5. The switch forwards the packet to either swp3 or swp4, according to
> the packet's tag.
>
> That makes client A's MAC address flap between swp0 and the CPU port. If
> client B sends a packet to A, it is possible that the packet is
> forwarded to the CPU. With offload_fwd_mark = 1, the bridge core won't
> forward it back to the switch, resulting in packet loss.
>
> As we have the assisted_learning_on_cpu_port in DSA core now, enable
> that and disable hardware learning on the CPU port.
>
> Signed-off-by: DENG Qingfang <dqfext@gmail.com>
> ---

Reviewed-by: Vladimir Oltean <oltean@gmail.com>

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