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

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Date:   Tue, 19 Jan 2021 16:46:01 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     "Bedel, Alban" <alban.bedel@...q.com>
CC:     Claudiu Manoil <claudiu.manoil@....com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        "UNGLinuxDriver@...rochip.com" <UNGLinuxDriver@...rochip.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net v2] net: mscc: ocelot: Fix multicast to the CPU port

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@...q.com>
> Fixes: 9403c158b872 ("net: mscc: ocelot: support IPv4, IPv6 and plain Ethernet mdb entries")
> 
> ---

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

Thanks!