netdev - Re: [PATCH] net: dsa: ksz: Fix port membership

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Date:   Fri, 7 Dec 2018 21:05:25 +0100
From:   Andrew Lunn <andrew@...n.ch>
To:     Tristram.Ha@...rochip.com
Cc:     marex@...x.de, f.fainelli@...il.com,
        vivien.didelot@...oirfairelinux.com, Woojung.Huh@...rochip.com,
        UNGLinuxDriver@...rochip.com, davem@...emloft.net,
        netdev@...r.kernel.org
Subject: Re: [PATCH] net: dsa: ksz: Fix port membership

> I think if you do this without setting offload_fwd_mark you will
> receive duplicate frame.

I don't think it will, at least not in the normal case. The hardware
should know the egress port, so there is no need to forward a copy to
the CPU. The only time it should forward to the CPU is when the egress
port is not known, so it floods. Without offload_fwd_mark set, the SW
bridge will flood it back out the ports causing duplication. But that
is not too bad. The Marvell driver did this for a while and nothing
bad was reported.

    Andrew