netdev - Re: [PATCH net-next] tcp: fix TCP_DEFER

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Message-ID: <CANn89iKo1BAkcbnPfTfgN8sd=6trg37sghzFXqSS6vJAOU70PA@mail.gmail.com>
Date: Wed, 11 Jun 2025 04:20:47 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: Jeremy Harris <jgh@...m.org>
Cc: netdev@...r.kernel.org, ncardwell@...gle.com
Subject: Re: [PATCH net-next] tcp: fix TCP_DEFER_ACCEPT for Fast Open

On Wed, Jun 11, 2025 at 4:15 AM Jeremy Harris <jgh@...m.org> wrote:
>
> The TCP_DEFER_ACCEPT socket option defers sending the 3rd-ack segment
> for a connection until a data write (or timeout).  The existing
> implementation works for traditional connections but not for Fast Open,
> where the syn moves us to ESTABLISHED and data in the SYN then causes an
> ACK to be sent.
>
> Fix by adding checks in those ACK paths for the state set by the
> setsockopt, and clear down that state when we send data.
>
> Signed-off-by: Jeremy Harris <jgh@...m.org>

You seem to prefer patches adding code in the fast path, again for a
very seldom used TCP feature.

Please find a better way ?

Thank you.