RE: [PATCH v15 net-next 10/14] tcp: accecn: AccECN option

["Ilpo Järvinen" <ij@kernel.org>]

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On Thu, 21 Aug 2025, Chia-Yu Chang (Nokia) wrote:

> > -----Original Message-----
> > From: Eric Dumazet <edumazet@google.com> 
> > Sent: Thursday, August 21, 2025 2:30 PM
> > To: Chia-Yu Chang (Nokia) <chia-yu.chang@nokia-bell-labs.com>
> > Cc: pabeni@redhat.com; linux-doc@vger.kernel.org; corbet@lwn.net; horms@kernel.org; dsahern@kernel.org; kuniyu@amazon.com; bpf@vger.kernel.org; netdev@vger.kernel.org; dave.taht@gmail.com; jhs@mojatatu.com; kuba@kernel.org; stephen@networkplumber.org; xiyou.wangcong@gmail.com; jiri@resnulli.us; davem@davemloft.net; andrew+netdev@lunn.ch; donald.hunter@gmail.com; ast@fiberby.net; liuhangbin@gmail.com; shuah@kernel.org; linux-kselftest@vger.kernel.org; ij@kernel.org; ncardwell@google.com; Koen De Schepper (Nokia) <koen.de_schepper@nokia-bell-labs.com>; g.white@cablelabs.com; ingemar.s.johansson@ericsson.com; mirja.kuehlewind@ericsson.com; cheshire@apple.com; rs.ietf@gmx.at; Jason_Livingood@comcast.com; vidhi_goel@apple.com
> > 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@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?

Wouldn't it also make sense to change the byte counters to __u64?

(It won't help the alignment though if the CE counter is left __u32.)

-- 
 i.