Re: [PATCH bpf-next v8 05/12] net-timestamp: prepare for isolating two modes of SO_TIMESTAMPING

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On Thu, Feb 6, 2025 at 4:43 PM Jason Xing <kerneljasonxing@xxxxxxxxx> wrote:
>
> On Wed, Feb 5, 2025 at 11:34 PM Willem de Bruijn
> <willemdebruijn.kernel@xxxxxxxxx> wrote:
> >
> > Jason Xing wrote:
> > > No functional changes here, only add skb_enable_app_tstamp() to test
> > > if the orig_skb matches the usage of application SO_TIMESTAMPING
> > > or its bpf extension. And it's good to support two modes in
> > > parallel later in this series.
> > >
> > > Also, this patch deliberately distinguish the software and
> > > hardware SCM_TSTAMP_SND timestamp by passing 'sw' parameter in order
> > > to avoid such a case where hardware may go wrong and pass a NULL
> > > hwstamps, which is even though unlikely to happen. If it really
> > > happens, bpf prog will finally consider it as a software timestamp.
> > > It will be hardly recognized. Let's make the timestamping part
> > > more robust.
> >
> > Disagree. Don't add a crutch that has not shown to be necessary for
> > all this time.
> >
> > Just infer hw from hwtstamps != NULL.
>
> I can surely modify this part as you said, but may I ask why? I cannot
> find a good reason to absolutely trust the hardware behaviour. If that
> corner case happens, it would be very hard to trace the root cause...

No offense, just curious. I can keep the same approach as
SO_TIMESTAMPING since you disagree. I have no strong preference
because I found It's simpler after rewriting this part.

I will simplify this patch in v9 :)

Thanks,
Jason





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