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
> >
> >
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> >
> >
> > 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.
