netdev - Re: [PATCH net-next v2 02/12] net-timestamp: open gate for bpf

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Message-ID: <CAL+tcoASCO5_N+cY0bJYBn8+6C7FzhQ2QtB=8q5zEnrYFNBa3w@mail.gmail.com>
Date: Wed, 23 Oct 2024 11:49:09 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc: Martin KaFai Lau <martin.lau@...ux.dev>, 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, 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, 
	bpf@...r.kernel.org, netdev@...r.kernel.org, 
	Jason Xing <kernelxing@...cent.com>
Subject: Re: [PATCH net-next v2 02/12] net-timestamp: open gate for bpf_setsockopt

On Wed, Oct 23, 2024 at 8:06 AM Willem de Bruijn
<willemdebruijn.kernel@...il.com> wrote:
>
> Jason Xing wrote:
> > On Wed, Oct 16, 2024 at 5:56 AM Willem de Bruijn
> > <willemdebruijn.kernel@...il.com> wrote:
> > >
> > > Martin KaFai Lau wrote:
> > > > On 10/11/24 9:06 PM, Jason Xing wrote:
> > > > >   static int sol_socket_sockopt(struct sock *sk, int optname,
> > > > >                           char *optval, int *optlen,
> > > > >                           bool getopt)
> > > > >   {
> > > > > +   struct so_timestamping ts;
> > > > > +   int ret = 0;
> > > > > +
> > > > >     switch (optname) {
> > > > >     case SO_REUSEADDR:
> > > > >     case SO_SNDBUF:
> > > > > @@ -5225,6 +5245,13 @@ static int sol_socket_sockopt(struct sock *sk, int optname,
> > > > >             break;
> > > > >     case SO_BINDTODEVICE:
> > > > >             break;
> > > > > +   case SO_TIMESTAMPING_NEW:
> > > > > +   case SO_TIMESTAMPING_OLD:
> > > >
> > > > How about remove the "_OLD" support ?
> > >
> > > +1 I forgot to mention that yesterday.
> >
> > Hello Willem, Martin,
> >
> > I did a test on this and found that if we only use
> > SO_TIMESTAMPING_NEW, we will never enter the real set sk_tsflags_bpf
> > logic, unless there is "case SO_TIMESTAMPING_OLD".
> >
> > And I checked SO_TIMESTAMPING in include/uapi/asm-generic/socket.h:
> > #if __BITS_PER_LONG == 64 || (defined(__x86_64__) && defined(__ILP32__))
> > /* on 64-bit and x32, avoid the ?: operator */
> > ...
> > #define SO_TIMESTAMPING         SO_TIMESTAMPING_OLD
> > ...
> > #else
> > ...
> > #define SO_TIMESTAMPING (sizeof(time_t) == sizeof(__kernel_long_t) ?
> > SO_TIMESTAMPING_OLD : SO_TIMESTAMPING_NEW)
> > ...
> > #endif
> >
> > The SO_TIMESTAMPING is defined as SO_TIMESTAMPING_OLD. I wonder if I
> > missed something? Thanks in advance.
>
> The _NEW vs _OLD aim to deal with y2038 issues on 32-bit platforms.
>
> For new APIs, like BPF timestamping, we should always use the safe
> structs, such as timespec64.

Thanks, I learned a lot.

>
> Then we can just use SO_TIMESTAMPING without the NEW or OLD suffix.

Weird thing is that the SO_TIMESTAMPING would be converted to
SO_TIMESTAMPING_OLD in kernel if I use this :
bpf_setsockopt(skops, SOL_SOCKET, SO_TIMESTAMPING, &flags, sizeof(flags));

As I mentioned before, SO_TIMESTAMPING exists in
include/uapi/asm-generic/socket.h:
#if __BITS_PER_LONG == 64 || (defined(__x86_64__) && defined(__ILP32__))
/* on 64-bit and x32, avoid the ?: operator */
...
#define SO_TIMESTAMPING         SO_TIMESTAMPING_OLD
...
#else
...
#define SO_TIMESTAMPING (sizeof(time_t) == sizeof(__kernel_long_t) ?
SO_TIMESTAMPING_OLD : SO_TIMESTAMPING_NEW)
...
#endif

So I wonder if there is something unexpected?

BTW, I conducted the test on a VM with x86_64 cpu.

Thanks,
Jason