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

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Message-ID:
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Date: Tue, 20 Jan 2026 10:10:32 +0000
From: "Chia-Yu Chang (Nokia)" <chia-yu.chang@...ia-bell-labs.com>
To: Eric Dumazet <edumazet@...gle.com>
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Subject: RE: [PATCH v9 net-next 04/15] tcp: ECT_1_NEGOTIATION and NEEDS_ACCECN
 identifiers

> -----Original Message-----
> From: Eric Dumazet <edumazet@...gle.com> 
> Sent: Tuesday, January 20, 2026 10:54 AM
> To: Chia-Yu Chang (Nokia) <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; bpf@...r.kernel.org; netdev@...r.kernel.org; dave.taht@...il.com; 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 (Nokia) <koen.de_schepper@...ia-bell-labs.com>; g.white@...lelabs.com; ingemar.s.johansson@...csson.com; mirja.kuehlewind@...csson.com; cheshire <cheshire@...le.com>; rs.ietf@....at; Jason_Livingood@...cast.com; Vidhi Goel <vidhi_goel@...le.com>; Olivier Tilmans (Nokia) <olivier.tilmans@...ia.com>
> Subject: Re: [PATCH v9 net-next 04/15] tcp: ECT_1_NEGOTIATION and NEEDS_ACCECN identifiers
> 
> 
> CAUTION: This is an external email. Please be very careful when clicking links or opening attachments. See the URL nok.it/ext for additional information.
> 
> 
> 
> 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>

Thanks for feedback, I will change into CC in the next version.

Chia-Yu