Re: [PATCH 7/8] socket: Add SO_TIMESTAMP[NS]_NEW

[Willem de Bruijn]

On Sat, Nov 24, 2018 at 10:59 PM Willem de Bruijn
<willemdebruijn.kernel@xxxxxxxxx> wrote:
>
> On Sat, Nov 24, 2018 at 3:58 AM Deepa Dinamani <deepa.kernel@xxxxxxxxx> wrote:
> >
> > Add SO_TIMESTAMP_NEW and SO_TIMESTAMPNS_NEW variants of
> > socket timestamp options.
> > These are the y2038 safe versions of the SO_TIMESTAMP_OLD
> > and SO_TIMESTAMPNS_OLD for all architectures.
> >
> > Note that the format of scm_timestamping.ts[0] is not changed
> > in this patch.
> >
> > Signed-off-by: Deepa Dinamani <deepa.kernel@xxxxxxxxx>
> > Cc: jejb@xxxxxxxxxxxxxxxx
> > Cc: ralf@xxxxxxxxxxxxxx
> > Cc: rth@xxxxxxxxxxx
> > Cc: linux-alpha@xxxxxxxxxxxxxxx
> > Cc: linux-mips@xxxxxxxxxxxxxx
> > Cc: linux-parisc@xxxxxxxxxxxxxxx
> > Cc: linux-rdma@xxxxxxxxxxxxxxx
> > Cc: netdev@xxxxxxxxxxxxxxx
> > Cc: sparclinux@xxxxxxxxxxxxxxx
> > ---
>
> > diff --git a/include/net/sock.h b/include/net/sock.h
> > index 8143c4c1a49d..9edf909dc176 100644
> > --- a/include/net/sock.h
> > +++ b/include/net/sock.h
> > @@ -801,6 +801,7 @@ enum sock_flags {
> >         SOCK_RCU_FREE, /* wait rcu grace period in sk_destruct() */
> >         SOCK_TXTIME,
> >         SOCK_XDP, /* XDP is attached */
> > +       SOCK_TSTAMP_NEW, /* Indicates 64 bit timestamps always */
>
> sk_flags is getting exhausted. Commit b9f40e21ef42 ("net-timestamp:
> move timestamp flags out of sk_flags") added a new u16 sk_tsflags
> specifically for timestamps. That may be a better choice here, too.
>
> > diff --git a/net/core/sock.c b/net/core/sock.c
> > index e60036618205..7b485dfaa400 100644
> > --- a/net/core/sock.c
> > +++ b/net/core/sock.c
> > @@ -652,15 +652,23 @@ static void setsockopt_timestamp(struct sock *sk, int type, int val)
> >         if (!val) {
> >                 sock_reset_flag(sk, SOCK_RCVTSTAMP);
> >                 sock_reset_flag(sk, SOCK_RCVTSTAMPNS);
> > +               sock_reset_flag(sk, SOCK_TSTAMP_NEW);
> >                 return;
> >         }
> >
> > +       if (type == SO_TIMESTAMP_NEW || type == SO_TIMESTAMPNS_NEW)
> > +               sock_set_flag(sk, SOCK_TSTAMP_NEW);
> > +       else
> > +               sock_reset_flag(sk, SOCK_TSTAMP_NEW);
> > +
>
> if adding a boolean whether the socket uses new or old-style
> timestamps, perhaps fail hard if a process tries to set a new-style
> option while an old-style is already set and vice versa. Also include
> SO_TIMESTAMPING_NEW as it toggles the same option.
>
> > diff --git a/net/socket.c b/net/socket.c
> > index d3defba55547..9abeb6bc9cfe 100644
> > --- a/net/socket.c
> > +++ b/net/socket.c
> > @@ -699,6 +699,38 @@ static void put_ts_pktinfo(struct msghdr *msg, struct sk_buff *skb)
> >                  sizeof(ts_pktinfo), &ts_pktinfo);
> >  }
> >
> > +static void sock_recv_sw_timestamp(struct msghdr *msg, struct sock *sk,
> > +                                  struct sk_buff *skb)
> > +{
> > +       if (sock_flag(sk, SOCK_TSTAMP_NEW)) {
> > +               if (!sock_flag(sk, SOCK_RCVTSTAMPNS)) {
> > +                       struct sock_timeval tv;
> > +
> > +                       skb_get_new_timestamp(skb, &tv);
> > +                       put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMP_NEW,
> > +                                sizeof(tv), &tv);
> > +               } else {
> > +                       struct __kernel_timespec ts;
> > +
> > +                       skb_get_new_timestampns(skb, &ts);
> > +                       put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMPNS_NEW,
> > +                                sizeof(ts), &ts);
> > +               }
> > +       }
> > +       if (!sock_flag(sk, SOCK_RCVTSTAMPNS)) {
> > +               struct __kernel_old_timeval tv;
> > +
> > +               skb_get_timestamp(skb, &tv);
> > +               put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMP_OLD,
> > +                        sizeof(tv), &tv);
> > +       } else {
> > +               struct timespec ts;
> > +
> > +               skb_get_timestampns(skb, &ts);
> > +               put_cmsg(msg, SOL_SOCKET, SO_TIMESTAMPNS_OLD,
> > +                        sizeof(ts), &ts);
> > +       }
> > +}
> >  /*
> >   * called from sock_recv_timestamp() if sock_flag(sk, SOCK_RCVTSTAMP)
> >   * or sock_flag(sk, SOCK_RCVTSTAMPNS)
> > @@ -719,19 +751,8 @@ void __sock_recv_timestamp(struct msghdr *msg, struct sock *sk,
> >                 false_tstamp = 1;
> >         }
> > -       if (need_software_tstamp) {
>
> Considerably less code churn if adding __sock_recv_timestamp_2038 and
> calling that here:
>
>                    if (sock_flag(sk, SOCK_TSTAMP_NEW))
>                            __sock_recv_timestamp_2038(msg, sk, skb);
>                    else if ...
>
> Same for the tcp case above, really, and in the case of the next patch
> for SO_TIMESTAMPING_NEW

That naming convention, ..._2038, is not the nicest, of course. That
is not the relevant bit in the above comment.

Come to think of it, and related to my question in patch 2 why the
need to rename at all, could all new structs, constants and functions
be named consistently with 64 suffix? __sock_recv_timestamp64,
SO_TIMESTAMPING64 and timeval64 (instead of sock_timeval,
it isn't really a sock specific struct)?

I guess that there is a good reason for the renaming exercise and
conditional mapping of SO_TIMESTAMP onto old or new interface.
Please elucidate in the commit message.