netdev - Re: [PATCH v2 net-next 06/14] tcp: accecn: handle unexpected AccECN negotiation feedback

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Message-ID: <feca7414-31fc-4eb2-9b25-e8adc70c2394@redhat.com>
Date: Tue, 23 Sep 2025 12:14:10 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: chia-yu.chang@...ia-bell-labs.com, edumazet@...gle.com,
 linux-doc@...r.kernel.org, corbet@....net, horms@...nel.org,
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Subject: Re: [PATCH v2 net-next 06/14] tcp: accecn: handle unexpected AccECN
 negotiation feedback

On 9/18/25 6:21 PM, chia-yu.chang@...ia-bell-labs.com wrote:
> From: Chia-Yu Chang <chia-yu.chang@...ia-bell-labs.com>
> 
> According to Section 3.1.2 of AccECN spec (RFC9768), if a TCP Client
> has sent a SYN requesting AccECN feedback with (AE,CWR,ECE) = (1,1,1)
> then receives a SYN/ACK with the currently reserved combination
> (AE,CWR,ECE) = (1,0,1) but it does not have logic specific to such a
> combination, the Client MUST enable AccECN mode as if the SYN/ACK
> confirmed that the Server supported AccECN and as if it fed back that
> the IP-ECN field on the SYN had arrived unchanged.
> 
> Signed-off-by: Chia-Yu Chang <chia-yu.chang@...ia-bell-labs.com>

This looks like a fix for an incorrect behavior introduced by a previous
AccECN patch. If so, please add a suitable fixes tag. We accept such
tags even for net-next material, and it's better to explicitly call out
needed fixes.

Thanks,

Paolo