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 10:24:04 -0800
From:   Jesus Sanchez-Palencia <jesus.sanchez-palencia@...el.com>
To:     Willem de Bruijn <willemdebruijn.kernel@...il.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.

Hi,


On 01/19/2018 01:15 PM, Willem de Bruijn wrote:
> 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.


Ok, will do.


> 
> 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?



> 
>> @@ -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.



> 
>> +               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?


Sure, will fix.


Thanks,
Jesus