netdev - Re: [RFC PATCH 0/4] net: dsa: link aggregation support

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Message-ID: <87h7qfv5j7.fsf@waldekranz.com>
Date:   Tue, 27 Oct 2020 20:21:32 +0100
From:   Tobias Waldekranz <tobias@...dekranz.com>
To:     Vladimir Oltean <olteanv@...il.com>,
        Marek Behun <marek.behun@....cz>
Cc:     Andrew Lunn <andrew@...n.ch>, vivien.didelot@...il.com,
        f.fainelli@...il.com, netdev@...r.kernel.org
Subject: Re: [RFC PATCH 0/4] net: dsa: link aggregation support

On Tue, Oct 27, 2020 at 21:04, Vladimir Oltean <olteanv@...il.com> wrote:
> On Tue, Oct 27, 2020 at 07:33:37PM +0100, Marek Behun wrote:
>> > In order for this to work on transmit, we need to add forward offloading
>> > to the bridge so that we can, for example, send one FORWARD from the CPU
>> > to send an ARP broadcast to swp1..4 instead of four FROM_CPUs.
>> 
>> Wouldn't this be solved if the CPU master interface was a bonding interface?
>
> I don't see how you would do that. Would DSA keep returning -EPROBE_DEFER
> until user space decides to set up a bond over the master interfaces?
> How would you even describe that in device tree?

Yeah that would be very hard indeed. Since this is going to be
completely transparent to the user I think the best way is to just setup
the hardware to see the two CPU ports as a LAG whenever you find
e.g. "cpu0" and "cpu1", but have no representation of it as a separate
netdev.

DSA will have an rx_handler attached to both ports anyway, so it can
just run the same handler for both. On Tx it can just load-balance in
software like team does.