netdev - Re: [PATCH net-next 2/2] tcp: put a TLV list of TCP stats in error queue

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Message-ID: <CACSApvYRcBLLc9QZmts7CDxRcqaF+g4fJsGY52t7jDWXy3fw9g@mail.gmail.com>
Date:   Wed, 7 Sep 2016 01:04:38 -0400
From:   Soheil Hassas Yeganeh <soheil@...gle.com>
To:     "Francis Y. Yan" <francisyyan@...il.com>
Cc:     David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Neal Cardwell <ncardwell@...gle.com>,
        Yuchung Cheng <ycheng@...gle.com>
Subject: Re: [PATCH net-next 2/2] tcp: put a TLV list of TCP stats in error queue

On Tue, Sep 6, 2016 at 9:32 PM, Francis Y. Yan <francisyyan@...il.com> wrote:
>
> To export useful TCP statistics along with timestamps, such as
> rwnd-limited time and min RTT, we enqueue a TLV list in error queue
> immediately when a timestamp is generated.
>
> Specifically, if user space requests SOF_TIMESTAMPING_TX_* timestamps
> and sets SOF_TIMESTAMPING_OPT_STATS, the kernel will create a list of
> TLVs (struct nlattr) containing all the statistics and store the list
> in payload of the skb that is going to be enqueued into error queue.
> Notice that SOF_TIMESTAMPING_OPT_STATS can only be set together with
> SOF_TIMESTAMPING_OPT_TSONLY.
>
> In addition, if the application in user space also enables receiving
> timestamp (e.g. by SOF_TIMESTAMPING_SOFTWARE), calling recvfrom() on
> error queue will return one more control message with a cmsg_type of
> SCM_OPT_STATS containing the list of TLVs in its cmsg_data.
>
> Signed-off-by: Francis Y. Yan <francisyyan@...il.com>
> Signed-off-by: Yuchung Cheng <ycheng@...gle.com>

Acked-by: Soheil Hassas Yeganeh <soheil@...gle.com>