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

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Date:   Tue, 23 Jan 2018 21:02:48 +0100
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 <vinicius.gomes@...el.com>,
        Richard Cochran <richardcochran@...il.com>,
        intel-wired-lan@...ts.osuosl.org, anna-maria@...utronix.de,
        Henrik Austad <henrik@...tad.us>,
        Thomas Gleixner <tglx@...utronix.de>,
        John Stultz <john.stultz@...aro.org>, andre.guedes@...el.com,
        Ivan Briano <ivan.briano@...el.com>,
        Levi Pearson <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.

>> If using ns_capable, skb->tstamp must continue to be scrubbed when traversing
>> network namespaces.
>
>
> I was planning to follow Eric's suggestion and move the tstamp scrubbing out of
> skb_scrub_packet() into ____dev_forward_skb() instead. Would that break when
> traversing namespaces?

That implies namespace traversal, so sounds perfect for this purpose.

>>
>>> @@ -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.
>
>
> Ok. SO_MARK is doing the same so it might have "mis-inspired" me. I should
> probably fix both.

The SO_MARK cmsg does need a check on each invocation,
because it is not conditional on a sock_flag like SO_TXTIME.