> -----Original Message-----
> From: Eric Dumazet <edumazet@xxxxxxxxxx>
> Sent: Thursday, August 21, 2025 7:46 PM
> To: Chia-Yu Chang (Nokia) <chia-yu.chang@xxxxxxxxxxxxxxxxxxx>; Neal Cardwell <ncardwell@xxxxxxxxxx>
> Cc: pabeni@xxxxxxxxxx; linux-doc@xxxxxxxxxxxxxxx; corbet@xxxxxxx; horms@xxxxxxxxxx; dsahern@xxxxxxxxxx; kuniyu@xxxxxxxxxx; bpf@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; jhs@xxxxxxxxxxxx; kuba@xxxxxxxxxx; stephen@xxxxxxxxxxxxxxxxxx; xiyou.wangcong@xxxxxxxxx; jiri@xxxxxxxxxxx; davem@xxxxxxxxxxxxx; andrew+netdev@xxxxxxx; donald.hunter@xxxxxxxxx; ast@xxxxxxxxxxx; liuhangbin@xxxxxxxxx; shuah@xxxxxxxxxx; linux-kselftest@xxxxxxxxxxxxxxx; ij@xxxxxxxxxx; Koen De Schepper (Nokia) <koen.de_schepper@xxxxxxxxxxxxxxxxxxx>; g.white@xxxxxxxxxxxxx; ingemar.s.johansson@xxxxxxxxxxxx; mirja.kuehlewind@xxxxxxxxxxxx; cheshire@xxxxxxxxx; rs.ietf@xxxxxx; Jason_Livingood@xxxxxxxxxxx; vidhi_goel@xxxxxxxxx
> Subject: Re: [PATCH v15 net-next 10/14] tcp: accecn: AccECN option
>
>
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>
>
> On Thu, Aug 21, 2025 at 7:58 AM Chia-Yu Chang (Nokia) <chia-yu.chang@xxxxxxxxxxxxxxxxxxx> wrote:
> >
> > > -----Original Message-----
> > > From: Eric Dumazet <edumazet@xxxxxxxxxx>
> > > Sent: Thursday, August 21, 2025 2:30 PM
> > > To: Chia-Yu Chang (Nokia) <chia-yu.chang@xxxxxxxxxxxxxxxxxxx>
> > > Cc: pabeni@xxxxxxxxxx; linux-doc@xxxxxxxxxxxxxxx; corbet@xxxxxxx;
> > > horms@xxxxxxxxxx; dsahern@xxxxxxxxxx; kuniyu@xxxxxxxxxx;
> > > bpf@xxxxxxxxxxxxxxx; netdev@xxxxxxxxxxxxxxx; dave.taht@xxxxxxxxx;
> > > jhs@xxxxxxxxxxxx; kuba@xxxxxxxxxx; stephen@xxxxxxxxxxxxxxxxxx;
> > > xiyou.wangcong@xxxxxxxxx; jiri@xxxxxxxxxxx; davem@xxxxxxxxxxxxx;
> > > andrew+netdev@xxxxxxx; donald.hunter@xxxxxxxxx; ast@xxxxxxxxxxx;
> > > liuhangbin@xxxxxxxxx; shuah@xxxxxxxxxx;
> > > linux-kselftest@xxxxxxxxxxxxxxx; ij@xxxxxxxxxx;
> > > ncardwell@xxxxxxxxxx; Koen De Schepper (Nokia)
> > > <koen.de_schepper@xxxxxxxxxxxxxxxxxxx>; g.white@xxxxxxxxxxxxx;
> > > ingemar.s.johansson@xxxxxxxxxxxx; mirja.kuehlewind@xxxxxxxxxxxx;
> > > cheshire@xxxxxxxxx; rs.ietf@xxxxxx; Jason_Livingood@xxxxxxxxxxx;
> > > vidhi_goel@xxxxxxxxx
> > > Subject: Re: [PATCH v15 net-next 10/14] tcp: accecn: AccECN option
> > >
> > >
> > > 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 Fri, Aug 15, 2025 at 1:40 AM <chia-yu.chang@xxxxxxxxxxxxxxxxxxx> wrote:
> > [...]
> > > > /* Used for make_synack to form the ACE flags */ diff --git
> > > > a/include/uapi/linux/tcp.h b/include/uapi/linux/tcp.h index
> > > > bdac8c42fa82..53e0e85b52be 100644
> > > > --- a/include/uapi/linux/tcp.h
> > > > +++ b/include/uapi/linux/tcp.h
> > > > @@ -316,6 +316,13 @@ struct tcp_info {
> > > > * in milliseconds, including any
> > > > * unfinished recovery.
> > > > */
> > > > + __u32 tcpi_received_ce; /* # of CE marks received */
> > > > + __u32 tcpi_delivered_e1_bytes; /* Accurate ECN byte counters */
> > > > + __u32 tcpi_delivered_e0_bytes;
> > > > + __u32 tcpi_delivered_ce_bytes;
> > > > + __u32 tcpi_received_e1_bytes;
> > > > + __u32 tcpi_received_e0_bytes;
> > > > + __u32 tcpi_received_ce_bytes;
> > > > };
> > > >
> > >
> > > We do not add more fields to tcp_info, unless added fields are a multiple of 64 bits.
> > >
> > > Otherwise a hole is added and can not be recovered.
> >
> > Hi Eric,
> >
> > Thanks for the feedback.
> >
> > Then, would it make sense to add __u32 reserved; here or this is not an option?
> >
>
> I would prefer we take the opportunity to export a 32bit field right there, instead of a hole.
>
> A reserved field makes it difficult for ss commands to know if a new kernel is using it for a different purpose.
>
> Neal, any idea of what would be useful ?
>
> I was thinking lately of sk_err_soft, but I am not yet convinced.
Hi Eric,
I have not heard anything from Neal.
Do you think other fields can be exported to this 32-bit field?
Another way is to increase them from u32 to u64.
Chia-Yu
