> -----Original Message-----
> From: Eric Dumazet <eduma...@google.com>
> Sent: Thursday, August 21, 2025 7:46 PM
> To: Chia-Yu Chang (Nokia) <chia-yu.ch...@nokia-bell-labs.com>; Neal Cardwell
> <ncardw...@google.com>
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> Schepper (Nokia) <koen.de_schep...@nokia-bell-labs.com>;
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> 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.ch...@nokia-bell-labs.com> wrote:
> >
> > > -----Original Message-----
> > > From: Eric Dumazet <eduma...@google.com>
> > > Sent: Thursday, August 21, 2025 2:30 PM
> > > To: Chia-Yu Chang (Nokia) <chia-yu.ch...@nokia-bell-labs.com>
> > > Cc: pab...@redhat.com; linux-doc@vger.kernel.org; cor...@lwn.net;
> > > ho...@kernel.org; dsah...@kernel.org; kun...@amazon.com;
> > > b...@vger.kernel.org; net...@vger.kernel.org; dave.t...@gmail.com;
> > > j...@mojatatu.com; k...@kernel.org; step...@networkplumber.org;
> > > xiyou.wangc...@gmail.com; j...@resnulli.us; da...@davemloft.net;
> > > andrew+net...@lunn.ch; donald.hun...@gmail.com; a...@fiberby.net;
> > > liuhang...@gmail.com; sh...@kernel.org;
> > > linux-kselft...@vger.kernel.org; i...@kernel.org;
> > > ncardw...@google.com; Koen De Schepper (Nokia)
> > > <koen.de_schep...@nokia-bell-labs.com>; g.wh...@cablelabs.com;
> > > ingemar.s.johans...@ericsson.com; mirja.kuehlew...@ericsson.com;
> > > chesh...@apple.com; rs.i...@gmx.at; jason_living...@comcast.com;
> > > vidhi_g...@apple.com
> > > Subject: Re: [PATCH v15 net-next 10/14] tcp: accecn: AccECN option
> > >
> > >
> > > CAUTION: This is an external email. Please be very careful when clicking
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> > >
> > >
> > > On Fri, Aug 15, 2025 at 1:40 AM <chia-yu.ch...@nokia-bell-labs.com> 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
