netdev - RE: [PATCH v17 net-next 12/14] tcp: accecn: AccECN option failure handling

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Message-ID:
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Date: Thu, 11 Sep 2025 10:38:19 +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 v17 net-next 12/14] tcp: accecn: AccECN option failure
 handling

> -----Original Message-----
> From: Eric Dumazet <edumazet@...gle.com> 
> Sent: Thursday, September 11, 2025 12:36 PM
> To: Chia-Yu Chang (Nokia) <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; 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@...le.com; rs.ietf@....at; Jason_Livingood@...cast.com; vidhi_goel@...le.com
> Subject: Re: [PATCH v17 net-next 12/14] tcp: accecn: AccECN option failure handling
> 
> 
> 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, Sep 8, 2025 at 10:34 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>
> >
> 
> 
> ...
> 
> > diff --git a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h index 
> > 53e0e85b52be..00604b7f2f3f 100644
> > --- a/include/uapi/linux/tcp.h
> > +++ b/include/uapi/linux/tcp.h
> > @@ -316,6 +316,8 @@ struct tcp_info {
> >                                          * in milliseconds, including any
> >                                          * unfinished recovery.
> >                                          */
> > +       __u16   tcpi_accecn_fail_mode;
> > +       __u16   tcpi_accecn_opt_seen;
> 
> We never add fields in the middle of tcp_info , even in a patch series.
> 
> Some people might miss this rule in the future, by looking at a patch doing this, and repeating the mistake...
> 
> 
> >         __u32   tcpi_received_ce;    /* # of CE marks received */
> >         __u32   tcpi_delivered_e1_bytes;  /* Accurate ECN byte counters */
> >         __u32   tcpi_delivered_e0_bytes;

Thanks Eric.

I will fix this in the next version.

Chia-Yu