> -----Original Message-----
> From: Eric Dumazet <eduma...@google.com>
> Sent: Thursday, September 11, 2025 12:36 PM
> To: Chia-Yu Chang (Nokia) <chia-yu.ch...@nokia-bell-labs.com>
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> Subject: Re: [PATCH v17 net-next 12/14] tcp: accecn: AccECN option failure
> handling
>
>
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>
> On Mon, Sep 8, 2025 at 10:34 AM <chia-yu.ch...@nokia-bell-labs.com> wrote:
> >
> > From: Chia-Yu Chang <chia-yu.ch...@nokia-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 <i...@kernel.org>
> > Signed-off-by: Chia-Yu Chang <chia-yu.ch...@nokia-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
