linux-kernel - Re: [PATCH v2 6/8] socket: Add SO_TIMESTAMP[NS]

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Message-ID: <CAF=yD-L4xTU-KXsQ=uU36fEKv5St=69mmKqT8sD1mAmT_hfuVQ@mail.gmail.com>
Date:   Sat, 15 Dec 2018 10:11:24 -0500
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Deepa Dinamani <deepa.kernel@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Network Devel Mailing List <netdev@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        y2038 Mailman List <y2038@...ts.linaro.org>,
        "James E.J. Bottomley" <jejb@...isc-linux.org>,
        Ralf Baechle <ralf@...ux-mips.org>, rth@...ddle.net,
        linux-alpha@...r.kernel.org,
        "open list:RALINK MIPS ARCHITECTURE" <linux-mips@...ux-mips.org>,
        Parisc List <linux-parisc@...r.kernel.org>,
        linux-rdma@...r.kernel.org, sparclinux <sparclinux@...r.kernel.org>
Subject: Re: [PATCH v2 6/8] socket: Add SO_TIMESTAMP[NS]_NEW

On Fri, Dec 14, 2018 at 8:07 PM Deepa Dinamani <deepa.kernel@...il.com> wrote:
>
> > > diff --git a/arch/alpha/include/uapi/asm/socket.h b/arch/alpha/include/uapi/asm/socket.h
> > > index 00e45c80e574..352e3dc0b3d9 100644
> > > --- a/arch/alpha/include/uapi/asm/socket.h
> > > +++ b/arch/alpha/include/uapi/asm/socket.h
> > > @@ -3,6 +3,7 @@
> > >  #define _UAPI_ASM_SOCKET_H
> > >
> > >  #include <asm/sockios.h>
> > > +#include <asm/bitsperlong.h>
> > >
> > >  /* For setsockopt(2) */
> > >  /*
> > > @@ -110,12 +111,22 @@
> > >
> > >  #define SO_TIMESTAMP_OLD         29
> > >  #define SO_TIMESTAMPNS_OLD       35
> > > +
> > >  #define SO_TIMESTAMPING_OLD      37
> > >
> > > +#define SO_TIMESTAMP_NEW         62
> > > +#define SO_TIMESTAMPNS_NEW       63
> > > +
> > >  #if !defined(__KERNEL__)
> > >
> > > -#define SO_TIMESTAMP           SO_TIMESTAMP_OLD
> > > -#define SO_TIMESTAMPNS         SO_TIMESTAMPNS_OLD
> > > +#if __BITS_PER_LONG == 64
> > > +#define SO_TIMESTAMP           SO_TIMESTAMP_OLD
> > > +#define SO_TIMESTAMPNS         SO_TIMESTAMPNS_OLD
> > > +#else
> > > +#define SO_TIMESTAMP (sizeof(time_t) == sizeof(__kernel_long_t) ? SO_TIMESTAMP_OLD : SO_TIMESTAMP_NEW)
> > > +#define SO_TIMESTAMPNS (sizeof(time_t) == sizeof(__kernel_long_t) ? SO_TIMESTAMPNS_OLD : SO_TIMESTAMPNS_NEW)
> > > +#endif
> > > +
> >
> > This is not platform specific. Perhaps it can be deduplicated. The
> > interface expects callers to include <linux/socket.h>, not
> > <asm/socket.h> directly. So perhaps it can go there?
>
> I'm not following what you are saying here.
>
> Are you talking about in kernel users or userspace interface?
>
> Userspace should always include sys/socket.h according to the man page.
> I'm not sure if userspace can even include linux/socket.h directly.
> On my distribution this includes bits/socket.h which in turn includes
> asm/socket.h.

I meant include/uapi/linux/socket.h.

But you're right that that is not referenced from sys/socket.h.

I do see a reference to it in my bits/socket.h

    /* Socket level message types.  This must match the definitions in
       <linux/socket.h>.  */

so perhaps the logic could be both there and in libc bits/socket.h.

> Which file gets installed as asm/socket.h is defined per architecture
> in the kbuild file such as
> arch/ia64/include/uapi/asm/Kbuild (without series applied):
>
>  generic-y += poll.h
>  generic-y += sembuf.h
>  generic-y += shmbuf.h
>  generic-y += socket.h
>
> Also the new timestamp numbers being added are not the same for all
> architectures.
>
> So I'm not sure how this can be moved to linux/socket.h.

Does that matter, as long as they are defined? This basic block is the
same between all archs:

    -#define SO_TIMESTAMP           SO_TIMESTAMP_OLD
    -#define SO_TIMESTAMPNS         SO_TIMESTAMPNS_OLD
    +#if __BITS_PER_LONG == 64
    +#define SO_TIMESTAMP           SO_TIMESTAMP_OLD
    +#define SO_TIMESTAMPNS         SO_TIMESTAMPNS_OLD
    +#else
    +#define SO_TIMESTAMP (sizeof(time_t) == sizeof(__kernel_long_t) ?
SO_TIMESTAMP_OLD : SO_TIMESTAMP_NEW)
    +#define SO_TIMESTAMPNS (sizeof(time_t) == sizeof(__kernel_long_t)
? SO_TIMESTAMPNS_OLD : SO_TIMESTAMPNS_NEW)
    +#endif

It might be too complex to coordinate changes between kernel and libc
headers, in which case you're right that this just has to live in
(each arch's) asm/socket.h directly.