netdev - Re: [PATCH v9 net-next 04/15] tcp: ECT_1_NEGOTIATION and NEEDS

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Message-ID: <CANn89iLzynvieqZUVK3NqaSpMT=-toZ1M4QHvQin5gHQM7T8yA@mail.gmail.com>
Date: Tue, 20 Jan 2026 10:53:47 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: chia-yu.chang@...ia-bell-labs.com
Cc: pabeni@...hat.com, parav@...dia.com, linux-doc@...r.kernel.org, 
	corbet@....net, horms@...nel.org, dsahern@...nel.org, kuniyu@...gle.com, 
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	Jason_Livingood@...cast.com, vidhi_goel@...le.com, 
	Olivier Tilmans <olivier.tilmans@...ia.com>
Subject: Re: [PATCH v9 net-next 04/15] tcp: ECT_1_NEGOTIATION and NEEDS_ACCECN identifiers

On Mon, Jan 19, 2026 at 7:59 PM <chia-yu.chang@...ia-bell-labs.com> wrote:
>
> From: Chia-Yu Chang <chia-yu.chang@...ia-bell-labs.com>
>
> Two CA module flags are added in this patch related to AccECN negotiation.
> First, a new CA module flag (TCP_CONG_NEEDS_ACCECN) defines that the CA
> expects to negotiate AccECN functionality using the ECE, CWR and AE flags
> in the TCP header.
>
> Second, during ECN negotiation, ECT(0) in the IP header is used. This patch
> enables CA to control whether ECT(0) or ECT(1) should be used on a per-segment
> basis. A new flag (TCP_CONG_ECT_1_NEGOTIATION) defines the expected ECT value
> in the IP header by the CA when not-yet initialized for the connection.
>
> The detailed AccECN negotiaotn during the 3WHS can be found in the AccECN spec:
>   https://tools.ietf.org/id/draft-ietf-tcpm-accurate-ecn-28.txt

While for some reason linux uses icsk_ca_ops, I think the terminology
is about "CC : Congestion Control"

Not sure what CA means...

Reviewed-by: Eric Dumazet <edumazet@...gle.com>