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

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Message-ID: <67ae0b1ed4a6f_24be4529484@willemb.c.googlers.com.notmuch>
Date: Thu, 13 Feb 2025 10:09:18 -0500
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Jason Xing <kerneljasonxing@...il.com>, 
 Willem de Bruijn <willemdebruijn.kernel@...il.com>
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Subject: Re: [PATCH bpf-next v10 09/12] bpf: add BPF_SOCK_OPS_TS_ACK_OPT_CB
 callback

Jason Xing wrote:
> On Thu, Feb 13, 2025 at 8:07 AM Jason Xing <kerneljasonxing@...il.com> wrote:
> >
> > 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.
> 
> I updated it in the next version locally :)

Great. I was going to say that I do prefer this.