netdev - Re: [RFC v2 net-next 01/10] net: Add a new socket option for a future transmit time.

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Message-ID: <CAF=yD-JCN483_e9U7tb_4+2jGyWKfhS0TzooOui+kS4Gh7RSqw@mail.gmail.com>
Date:   Fri, 19 Jan 2018 16:15:46 -0500
From:   Willem de Bruijn <willemdebruijn.kernel@...il.com>
To:     Jesus Sanchez-Palencia <jesus.sanchez-palencia@...el.com>
Cc:     Network Development <netdev@...r.kernel.org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiří Pírko <jiri@...nulli.us>,
        vinicius.gomes@...el.com,
        Richard Cochran <richardcochran@...il.com>,
        intel-wired-lan@...ts.osuosl.org, anna-maria@...utronix.de,
        henrik@...tad.us, Thomas Gleixner <tglx@...utronix.de>,
        John Stultz <john.stultz@...aro.org>, andre.guedes@...el.com,
        ivan.briano@...el.com, levi.pearson@...man.com,
        Richard Cochran <rcochran@...utronix.de>
Subject: Re: [RFC v2 net-next 01/10] net: Add a new socket option for a future
 transmit time.

On Wed, Jan 17, 2018 at 6:06 PM, Jesus Sanchez-Palencia
<jesus.sanchez-palencia@...el.com> wrote:
> From: Richard Cochran <rcochran@...utronix.de>
>
> This patch introduces SO_TXTIME.  User space enables this option in
> order to pass a desired future transmit time in a CMSG when calling
> sendmsg(2).
>
> A new field is added to struct sockcm_cookie, and the tstamp from
> skbuffs will be used later on.
>
> Signed-off-by: Richard Cochran <rcochran@...utronix.de>
> Signed-off-by: Jesus Sanchez-Palencia <jesus.sanchez-palencia@...el.com>
> ---

> diff --git a/net/core/sock.c b/net/core/sock.c
> index abf4cbff99b2..37ef4b33fd92 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -1061,6 +1061,13 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
>                         sock_valbool_flag(sk, SOCK_ZEROCOPY, valbool);
>                 break;
>
> +       case SO_TXTIME:
> +               if (ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN))
> +                       sock_valbool_flag(sk, SOCK_TXTIME, valbool);
> +               else
> +                       ret = -EPERM;
> +               break;
> +
>         default:
>                 ret = -ENOPROTOOPT;
>                 break;

Please add getsockopt alongside setsockopt.

I would also restrict input to [0, 1] exactly to allow for future extensions.

If using ns_capable, skb->tstamp must continue to be scrubbed when traversing
network namespaces.

> @@ -2130,6 +2137,15 @@ int __sock_cmsg_send(struct sock *sk, struct msghdr *msg, struct cmsghdr *cmsg,
>                 sockc->tsflags &= ~SOF_TIMESTAMPING_TX_RECORD_MASK;
>                 sockc->tsflags |= tsflags;
>                 break;
> +       case SO_TXTIME:
> +               if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN))
> +                       return -EPERM;
> +               if (!sock_flag(sk, SOCK_TXTIME))
> +                       return -EINVAL;

No need for ns_capable check on each packet when already required to
toggle socket option.

> +               if (cmsg->cmsg_len != CMSG_LEN(sizeof(ktime_t)))
> +                       return -EINVAL;

I don't see any existing reference to ktime_t in include/uapi. Just use a s64?