netdev - Re: [PATCH v15 net-next 12/14] tcp: accecn: AccECN option failure handling

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Message-ID: <CANn89i+xNs7jfc3OF42J0jat=-ivrQgTfycJPyKW28yTJPaaDg@mail.gmail.com>
Date: Thu, 21 Aug 2025 05:55:41 -0700
From: Eric Dumazet <edumazet@...gle.com>
To: chia-yu.chang@...ia-bell-labs.com
Cc: pabeni@...hat.com, linux-doc@...r.kernel.org, corbet@....net, 
	horms@...nel.org, dsahern@...nel.org, kuniyu@...zon.com, bpf@...r.kernel.org, 
	netdev@...r.kernel.org, jhs@...atatu.com, kuba@...nel.org, 
	stephen@...workplumber.org, xiyou.wangcong@...il.com, jiri@...nulli.us, 
	davem@...emloft.net, andrew+netdev@...n.ch, donald.hunter@...il.com, 
	ast@...erby.net, liuhangbin@...il.com, shuah@...nel.org, 
	linux-kselftest@...r.kernel.org, ij@...nel.org, ncardwell@...gle.com, 
	koen.de_schepper@...ia-bell-labs.com, g.white@...lelabs.com, 
	ingemar.s.johansson@...csson.com, mirja.kuehlewind@...csson.com, 
	cheshire@...le.com, rs.ietf@....at, Jason_Livingood@...cast.com, 
	vidhi_goel@...le.com
Subject: Re: [PATCH v15 net-next 12/14] tcp: accecn: AccECN option failure handling

On Fri, Aug 15, 2025 at 1:40 AM <chia-yu.chang@...ia-bell-labs.com> wrote:
>
> From: Chia-Yu Chang <chia-yu.chang@...ia-bell-labs.com>
>
> AccECN option may fail in various way, handle these:
> - Attempt to negotiate the use of AccECN on the 1st retransmitted SYN
>         - From the 2nd retransmitted SYN, stop AccECN negotiation
> - Remove option from SYN/ACK rexmits to handle blackholes
> - If no option arrives in SYN/ACK, assume Option is not usable
>         - If an option arrives later, re-enabled
> - If option is zeroed, disable AccECN option processing
>
> This patch use existing padding bits in tcp_request_sock and
> holes in tcp_sock without increasing the size.
>
> Signed-off-by: Ilpo Järvinen <ij@...nel.org>
> Signed-off-by: Chia-Yu Chang <chia-yu.chang@...ia-bell-labs.com>

Truly invasive changes, what can I say....

Not sure why you CC so many folks which will very unlikely give any feedback.

What is the purpose of WARN_ON_ONCE() in tcp_accecn_option_init() ?

Just to feed syzbot ?