linux-kernel - Re: [PATCH net v2] net: dsa: tag_rtl4

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Date:   Mon, 30 Oct 2023 15:37:24 +0100
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Vladimir Oltean <olteanv@...il.com>
Cc:     Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net v2] net: dsa: tag_rtl4_a: Bump min packet size

On Mon, Oct 30, 2023 at 3:16 PM Vladimir Oltean <olteanv@...il.com> wrote:

> Could you please try to revert the effect of commit 339133f6c318 ("net:
> dsa: tag_rtl4_a: Drop bit 9 from egress frames") by setting that bit in
> the egress tag again? Who knows, maybe it is the bit which tells the
> switch to bypass the forwarding process.

I have already tried that, it was one of the first things I tried,
just looking over the git log and looking for usual suspects.

Sadly it has no effect whatsoever, the problem persists :(

> Or maybe there is a bit in a
> different position which does this. You could try to fill in all bits in
> unknown positions, check that there are no regressions with packet sizes
> < 1496, and then see if that made any changes to packet sizes >= 1496.
> If it did, try to see which bit made the difference.

Hehe now we're talking :D

I did something similar before, I think just switching a different bit
every 10 packets or so and running a persistent ping until it succeeds
or not.

I'll see what I can come up with.

Yours,
Linus Walleij