Re: [PATCH net-next v6] tcp: Add RFC4898 tcpEStatsPerfDataSegsOut/In

[David Miller <davem@davemloft.net>]

From: Martin KaFai Lau <kafai@fb.com>
Date: Mon, 14 Mar 2016 10:52:15 -0700

> Per RFC4898, they count segments sent/received
> containing a positive length data segment (that includes
> retransmission segments carrying data).  Unlike
> tcpi_segs_out/in, tcpi_data_segs_out/in excludes segments
> carrying no data (e.g. pure ack).
> 
> The patch also updates the segs_in in tcp_fastopen_add_skb()
> so that segs_in >= data_segs_in property is kept.
> 
> Together with retransmission data, tcpi_data_segs_out
> gives a better signal on the rxmit rate.
> 
> v6: Rebase on the latest net-next
> 
> v5: Eric pointed out that checking skb->len is still needed in
> tcp_fastopen_add_skb() because skb can carry a FIN without data.
> Hence, instead of open coding segs_in and data_segs_in, tcp_segs_in()
> helper is used.  Comment is added to the fastopen case to explain why
> segs_in has to be reset and tcp_segs_in() has to be called before
> __skb_pull().
> 
> v4: Add comment to the changes in tcp_fastopen_add_skb()
> and also add remark on this case in the commit message.
> 
> v3: Add const modifier to the skb parameter in tcp_segs_in()
> 
> v2: Rework based on recent fix by Eric:
> commit a9d99ce28ed3 ("tcp: fix tcpi_segs_in after connection establishment")
> 
> Signed-off-by: Martin KaFai Lau <kafai@fb.com>
> Cc: Chris Rapier <rapier@psc.edu>
> Cc: Eric Dumazet <edumazet@google.com>
> Cc: Marcelo Ricardo Leitner <mleitner@redhat.com>
> Cc: Neal Cardwell <ncardwell@google.com>
> Cc: Yuchung Cheng <ycheng@google.com>
> Acked-by: Eric Dumazet <edumazet@google.com>

Applied, thanks.