netdev - Re: [PATCH v1 net] tcp: Don't drop SYN+ACK for simultaneous connect().

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Message-ID: <CAJwJo6bFnNKXvxtpEBC5TqrQ0ATXJeFr7onivgNM1cqz3HJWgg@mail.gmail.com>
Date: Thu, 4 Jul 2024 21:47:34 +0100
From: Dmitry Safonov <0x7f454c46@...il.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: Paolo Abeni <pabeni@...hat.com>, Kuniyuki Iwashima <kuniyu@...zon.com>, 
	Lawrence Brakmo <brakmo@...com>, Kuniyuki Iwashima <kuni1840@...il.com>, netdev@...r.kernel.org, 
	"David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, David Ahern <dsahern@...nel.org>
Subject: Re: [PATCH v1 net] tcp: Don't drop SYN+ACK for simultaneous connect().

On Thu, 4 Jul 2024 at 13:23, Eric Dumazet <edumazet@...gle.com> wrote:
>
> On Thu, Jul 4, 2024 at 1:16 PM Paolo Abeni <pabeni@...hat.com> wrote:
[..]
> >
> > Apparently this behavior change is causing TCP AO self-tests failures:
> >
> > https://netdev.bots.linux.dev/contest.html?pw-n=0&branch=net-next-2024-07-04--09-00
> > e.g.
> > https://netdev-3.bots.linux.dev/vmksft-tcp-ao-dbg/results/668061/22-self-connect-ipv4/stdout
> >
>
> These tests seem to have broken assumptions on a kernel behavior which
> are orthogonal to TCP AO.

Yes, I think my intention here was to verify that it tests
simultaneous connect code-path. Which is quite guaranteed in
self-connect tcp case, I guess, but some experience tells that
anything may go or evolve with time in unexpected ways (aka paranoia),
I thought it's reasonable to check TCPChallengeACK & TCPSYNChallenge
counters to verify. It seems those checks can be just dropped.

Thanks,
             Dmitry