Re: [PATCH net v2] net: mscc: ocelot: Fix multicast to the CPU port

From: Vladimir Oltean
Date: Tue Jan 19 2021 - 11:47:46 EST

On Tue, Jan 19, 2021 at 03:06:38PM +0100, Alban Bedel wrote:
> Multicast entries in the MAC table use the high bits of the MAC
> address to encode the ports that should get the packets. But this port
> mask does not work for the CPU port, to receive these packets on the
> CPU port the MAC_CPU_COPY flag must be set.
> Because of this IPv6 was effectively not working because neighbor
> solicitations were never received. This was not apparent before commit
> 9403c158 (net: mscc: ocelot: support IPv4, IPv6 and plain Ethernet mdb
> entries) as the IPv6 entries were broken so all incoming IPv6
> multicast was then treated as unknown and flooded on all ports.
> To fix this problem rework the ocelot_mact_learn() to set the
> MAC_CPU_COPY flag when a multicast entry that target the CPU port is
> added. For this we have to read back the ports endcoded in the pseudo
> MAC address by the caller. It is not a very nice design but that avoid
> changing the callers and should make backporting easier.
> Signed-off-by: Alban Bedel <alban.bedel@xxxxxxxx>
> Fixes: 9403c158b872 ("net: mscc: ocelot: support IPv4, IPv6 and plain Ethernet mdb entries")
> ---

Reviewed-by: Vladimir Oltean <vladimir.oltean@xxxxxxx>
Tested-by: Vladimir Oltean <vladimir.oltean@xxxxxxx>