netdev - Re: [PATCH net-next v4 5/6] net-timestamp: TCP timestamping

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Date:	Wed, 6 Aug 2014 09:08:16 -0400
From:	Willem de Bruijn <willemb@...gle.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	Network Development <netdev@...r.kernel.org>,
	David Miller <davem@...emloft.net>,
	Richard Cochran <richardcochran@...il.com>
Subject: Re: [PATCH net-next v4 5/6] net-timestamp: TCP timestamping

On Wed, Aug 6, 2014 at 2:55 AM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Mon, 2014-08-04 at 22:11 -0400, Willem de Bruijn wrote:
>> TCP timestamping extends SO_TIMESTAMPING to bytestreams.
>
>>
>> +void tcp_tx_timestamp(struct sock *sk, struct sk_buff *skb)
>> +{
>> +     struct skb_shared_info *shinfo = skb_shinfo(skb);
>> +
>> +     sock_tx_timestamp(sk, &shinfo->tx_flags);
>
> Arg, this breaks SKBTX_SHARED_FRAG support.
>
> And sock_tx_timestamp() is quite expensive for TCP where only
> SKBTX_ACK_TSTAMP could possibly be supported ?

The other options can also be set. But it is expensive. It can
actually be wrapped into a branch if (sk->sk_tsflags), to avoid
calling the function in the common case.

>
> static void tcp_tx_timestamp(const struct sock *sk, struct sk_buff *skb)
>
> I'll send a cumulative patch.

Thanks for spotting and fixing the critical shared frags issue. I
can send a patch for this, the two static functions identified by
sparse and the sequence number arithmetic in tcp_gso_tstamp.
>
>
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