netdev - Re: [PATCH bpf-next v10 09/12] bpf: add BPF_SOCK_OPS_TS_ACK_OPT

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Message-ID: <CAL+tcoA-5noB0rfHwU=FxANd9yifADFoq-vGkkzW=ZJ=BOnGUA@mail.gmail.com>
Date: Thu, 13 Feb 2025 08:07:19 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc: davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, 
	pabeni@...hat.com, dsahern@...nel.org, willemb@...gle.com, ast@...nel.org, 
	daniel@...earbox.net, andrii@...nel.org, martin.lau@...ux.dev, 
	eddyz87@...il.com, song@...nel.org, yonghong.song@...ux.dev, 
	john.fastabend@...il.com, kpsingh@...nel.org, sdf@...ichev.me, 
	haoluo@...gle.com, jolsa@...nel.org, shuah@...nel.org, ykolal@...com, 
	bpf@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH bpf-next v10 09/12] bpf: add BPF_SOCK_OPS_TS_ACK_OPT_CB callback

On Wed, Feb 12, 2025 at 11:26 PM Willem de Bruijn
<willemdebruijn.kernel@...il.com> wrote:
>
> Jason Xing wrote:
> > Support the ACK case for bpf timestamping.
> >
> > Add a new sock_ops callback, BPF_SOCK_OPS_TS_ACK_OPT_CB. This
> > callback will occur at the same timestamping point as the user
> > space's SCM_TSTAMP_ACK. The BPF program can use it to get the
> > same SCM_TSTAMP_ACK timestamp without modifying the user-space
> > application.
> >
> > This patch extends txstamp_ack to two bits: 1 stands for
> > SO_TIMESTAMPING mode, 2 bpf extension.
> >
> > Signed-off-by: Jason Xing <kerneljasonxing@...il.com>
> > ---
> >  include/net/tcp.h              | 6 ++++--
> >  include/uapi/linux/bpf.h       | 5 +++++
> >  net/core/skbuff.c              | 5 ++++-
> >  net/dsa/user.c                 | 2 +-
> >  net/ipv4/tcp.c                 | 2 +-
> >  net/socket.c                   | 2 +-
> >  tools/include/uapi/linux/bpf.h | 5 +++++
> >  7 files changed, 21 insertions(+), 6 deletions(-)
>
> > diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
> > index 0d704bda6c41..aa080f7ccea4 100644
> > --- a/net/ipv4/tcp.c
> > +++ b/net/ipv4/tcp.c
> > @@ -488,7 +488,7 @@ static void tcp_tx_timestamp(struct sock *sk, struct sockcm_cookie *sockc)
> >
> >               sock_tx_timestamp(sk, sockc, &shinfo->tx_flags);
> >               if (tsflags & SOF_TIMESTAMPING_TX_ACK)
> > -                     tcb->txstamp_ack = 1;
> > +                     tcb->txstamp_ack = TSTAMP_ACK_SK;
>
> Similar to the BPF code, should this by |= TSTAMP_ACK_SK?
>
> Does not matter in practice if the BPF setter can never precede this.

I gave the same thought on this too. We've already fixed the position
and order (of using socket timestamping and bpf timestamping).

I have no strong preference. If you insist, I can surely adjust it.

Thanks,
Jason