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

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Date:   Wed, 07 Sep 2016 07:22:37 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     "Francis Y. Yan" <francisyyan@...il.com>
Cc:     davem@...emloft.net, netdev@...r.kernel.org, edumazet@...gle.com,
        soheil@...gle.com, 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, 2016-09-06 at 18:32 -0700, Francis Y. Yan 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: Eric Dumazet <edumazet@...gle.com>