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

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Message-ID: <67183df34e8e3_1420e5294a2@willemb.c.googlers.com.notmuch>
Date: Tue, 22 Oct 2024 20:06:11 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Jason Xing <kerneljasonxing@...il.com>, 
 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

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.

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