netdev - Re: [PATCH net-next v2] tcp: provide timestamps for partial writes

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Date:   Thu, 05 Jan 2017 14:56:40 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     soheil.kdev@...il.com
Cc:     netdev@...r.kernel.org, soheil@...gle.com, willemb@...gle.com,
        edumazet@...gle.com, ncardwell@...gle.com, kafai@...com
Subject: Re: [PATCH net-next v2] tcp: provide timestamps for partial writes

From: Soheil Hassas Yeganeh <soheil.kdev@...il.com>
Date: Wed,  4 Jan 2017 11:19:34 -0500

> From: Soheil Hassas Yeganeh <soheil@...gle.com>
> 
> For TCP sockets, TX timestamps are only captured when the user data
> is successfully and fully written to the socket. In many cases,
> however, TCP writes can be partial for which no timestamp is
> collected.
> 
> Collect timestamps whenever any user data is (fully or partially)
> copied into the socket. Pass tcp_write_queue_tail to tcp_tx_timestamp
> instead of the local skb pointer since it can be set to NULL on
> the error path.
> 
> Note that tcp_write_queue_tail can be NULL, even if bytes have been
> copied to the socket. This is because acknowledgements are being
> processed in tcp_sendmsg(), and by the time tcp_tx_timestamp is
> called tcp_write_queue_tail can be NULL. For such cases, this patch
> does not collect any timestamps (i.e., it is best-effort).
> 
> This patch is written with suggestions from Willem de Bruijn and
> Eric Dumazet.
> 
> Change-log V1 -> V2:
> 	- Use sockc.tsflags instead of sk->sk_tsflags.
> 	- Use the same code path for normal writes and errors.
> 
> Signed-off-by: Soheil Hassas Yeganeh <soheil@...gle.com>
> Acked-by: Yuchung Cheng <ycheng@...gle.com>

Applied, thanks.