netdev - Re: [PATCH net v2 1/2] socket: fix option SO_TIMESTAMPING

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Message-ID: <CA+FuTSfkBHtKqjppMmqudj9GwZBidSqvOP6WCzoxLGihqiz5Qw@mail.gmail.com>
Date:   Mon, 12 Oct 2020 09:37:49 -0400
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Christian Eggers <ceggers@...i.de>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Deepa Dinamani <deepa.kernel@...il.com>,
        Christoph Hellwig <hch@....de>,
        Network Development <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH net v2 1/2] socket: fix option SO_TIMESTAMPING_NEW

On Mon, Oct 12, 2020 at 5:36 AM Christian Eggers <ceggers@...i.de> wrote:
>
> The comparison of optname with SO_TIMESTAMPING_NEW is wrong way around,
> so SOCK_TSTAMP_NEW will first be set and than reset again. Additionally
> move it out of the test for SOF_TIMESTAMPING_RX_SOFTWARE as this seems
> unrelated.
>
> This problem happens on 32 bit platforms were the libc has already
> switched to struct timespec64 (from SO_TIMExxx_OLD to SO_TIMExxx_NEW
> socket options). ptp4l complains with "missing timestamp on transmitted
> peer delay request" because the wrong format is received (and
> discarded).
>
> Fixes: 9718475e6908 ("socket: Add SO_TIMESTAMPING_NEW")
> Signed-off-by: Christian Eggers <ceggers@...i.de>
> Reviewed-by: Willem de Bruijn <willemdebruijn.kernel@...il.com>
> Reviewed-by: Deepa Dinamani <deepa.kernel@...il.com>

We have not yet reviewed this second patch. Please do not add such
tags on behalf of other people.

That said, I now have and do agree with the change, so

Acked-by: Willem de Bruijn <willemb@...gle.com>

> ---
> v2:
> -----
> - integrated proposal from Willem de Bruijn
> - added Reviewed-by: from Willem and Deepa
>
>
> On Saturday, 10 October 2020, 02:23:10 CEST, Willem de Bruijn wrote:
> > This suggested fix still sets and clears the flag if calling
> > SO_TIMESTAMPING_NEW to disable timestamping.
> where is it cleared?
>
> > Instead, how about
> >
> >         case SO_TIMESTAMPING_NEW:
> > -               sock_set_flag(sk, SOCK_TSTAMP_NEW);
> >                 fallthrough;
> >         case SO_TIMESTAMPING_OLD:
> > [..]
> > +               sock_valbool_flag(sk, SOCK_TSTAMP_NEW,
> > +                                 optname == SO_TIMESTAMPING_NEW);
> > +
> using you version looks clearer
>
> >                 if (val & SOF_TIMESTAMPING_OPT_ID &&
> >
> I would like to keep this below the "ret = -FOO; break" statements. IMHO the
> setsockopt() call should either completely fail or succeed.

Agreed.


>  net/core/sock.c | 10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)
>
> diff --git a/net/core/sock.c b/net/core/sock.c
> index 34a8d12e38d7..669cf9b8bb44 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -994,8 +994,6 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
>                 __sock_set_timestamps(sk, valbool, true, true);
>                 break;
>         case SO_TIMESTAMPING_NEW:
> -               sock_set_flag(sk, SOCK_TSTAMP_NEW);
> -               fallthrough;
>         case SO_TIMESTAMPING_OLD:
>                 if (val & ~SOF_TIMESTAMPING_MASK) {
>                         ret = -EINVAL;
> @@ -1024,16 +1022,14 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
>                 }
>
>                 sk->sk_tsflags = val;
> +               sock_valbool_flag(sk, SOCK_TSTAMP_NEW, optname == SO_TIMESTAMPING_NEW);
> +
>                 if (val & SOF_TIMESTAMPING_RX_SOFTWARE)
>                         sock_enable_timestamp(sk,
>                                               SOCK_TIMESTAMPING_RX_SOFTWARE);
> -               else {
> -                       if (optname == SO_TIMESTAMPING_NEW)
> -                               sock_reset_flag(sk, SOCK_TSTAMP_NEW);
> -
> +               else
>                         sock_disable_timestamp(sk,
>                                                (1UL << SOCK_TIMESTAMPING_RX_SOFTWARE));
> -               }
>                 break;
>
>         case SO_RCVLOWAT:
> --
> Christian Eggers
> Embedded software developer
>
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