netdev - Re: [PATCH net 2/2] tcp: Merge tx_flags and tskey in tcp_shifted

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Message-ID: <CACSApvYcuCLYxdjOmG7uywqM9b_dDx0QwwARSiByxU0OYCmnxA@mail.gmail.com>
Date:	Wed, 20 Apr 2016 15:14:42 -0400
From:	Soheil Hassas Yeganeh <soheil@...gle.com>
To:	Martin KaFai Lau <kafai@...com>
Cc:	netdev <netdev@...r.kernel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	Neal Cardwell <ncardwell@...gle.com>,
	Willem de Bruijn <willemb@...gle.com>,
	Yuchung Cheng <ycheng@...gle.com>,
	Kernel Team <kernel-team@...com>
Subject: Re: [PATCH net 2/2] tcp: Merge tx_flags and tskey in tcp_shifted_skb

On Wed, Apr 20, 2016 at 1:39 AM, Martin KaFai Lau <kafai@...com> wrote:
> After receiving sacks, tcp_shifted_skb() will collapse
> skbs if possible.  tx_flags and tskey also have to be
> merged.
>
> This patch reuses the tcp_skb_collapse_tstamp() to handle
> them.
>
> BPF Output Before:
> ~~~~~
> <no-output-due-to-missing-tstamp-event>
>
> BPF Output After:
> ~~~~~
> <...>-2024  [007] d.s.    88.644374: : ee_data:14599
>
> Packetdrill Script:
> ~~~~~
> +0 `sysctl -q -w net.ipv4.tcp_min_tso_segs=10`
> +0 `sysctl -q -w net.ipv4.tcp_no_metrics_save=1`
> +0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
> +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
> +0 bind(3, ..., ...) = 0
> +0 listen(3, 1) = 0
>
> 0.100 < S 0:0(0) win 32792 <mss 1460,sackOK,nop,nop,nop,wscale 7>
> 0.100 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 7>
> 0.200 < . 1:1(0) ack 1 win 257
> 0.200 accept(3, ..., ...) = 4
> +0 setsockopt(4, SOL_TCP, TCP_NODELAY, [1], 4) = 0
>
> 0.200 write(4, ..., 1460) = 1460
> +0 setsockopt(4, SOL_SOCKET, 37, [2688], 4) = 0
> 0.200 write(4, ..., 13140) = 13140
>
> 0.200 > P. 1:1461(1460) ack 1
> 0.200 > . 1461:8761(7300) ack 1
> 0.200 > P. 8761:14601(5840) ack 1
>
> 0.300 < . 1:1(0) ack 1 win 257 <sack 1461:14601,nop,nop>
> 0.300 > P. 1:1461(1460) ack 1
> 0.400 < . 1:1(0) ack 14601 win 257
>
> 0.400 close(4) = 0
> 0.400 > F. 14601:14601(0) ack 1
> 0.500 < F. 1:1(0) ack 14602 win 257
> 0.500 > . 14602:14602(0) ack 2
>
> Signed-off-by: Martin KaFai Lau <kafai@...com>
> Cc: Eric Dumazet <edumazet@...gle.com>
> Cc: Neal Cardwell <ncardwell@...gle.com>
> Cc: Soheil Hassas Yeganeh <soheil@...gle.com>
> Cc: Willem de Bruijn <willemb@...gle.com>
> Cc: Yuchung Cheng <ycheng@...gle.com>
Acked-by: Soheil Hassas Yeganeh <soheil@...gle.com>
Tested-by: Soheil Hassas Yeganeh <soheil@...gle.com>
> ---
>  include/net/tcp.h     | 2 ++
>  net/ipv4/tcp_input.c  | 1 +
>  net/ipv4/tcp_output.c | 4 ++--
>  3 files changed, 5 insertions(+), 2 deletions(-)
>
> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index b91370f..6db1022 100644
> --- a/include/net/tcp.h
> +++ b/include/net/tcp.h
> @@ -552,6 +552,8 @@ void tcp_send_ack(struct sock *sk);
>  void tcp_send_delayed_ack(struct sock *sk);
>  void tcp_send_loss_probe(struct sock *sk);
>  bool tcp_schedule_loss_probe(struct sock *sk);
> +void tcp_skb_collapse_tstamp(struct sk_buff *skb,
> +                            const struct sk_buff *next_skb);
>
>  /* tcp_input.c */
>  void tcp_resume_early_retransmit(struct sock *sk);
> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> index 0edb071..c124c3c 100644
> --- a/net/ipv4/tcp_input.c
> +++ b/net/ipv4/tcp_input.c
> @@ -1309,6 +1309,7 @@ static bool tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,
>         if (skb == tcp_highest_sack(sk))
>                 tcp_advance_highest_sack(sk, skb);
>
> +       tcp_skb_collapse_tstamp(prev, skb);
>         tcp_unlink_write_queue(skb, sk);
>         sk_wmem_free_skb(sk, skb);
>
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index 5bc3c30..441ae9d 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -2441,8 +2441,8 @@ u32 __tcp_select_window(struct sock *sk)
>         return window;
>  }
>
> -static void tcp_skb_collapse_tstamp(struct sk_buff *skb,
> -                                   const struct sk_buff *next_skb)
> +void tcp_skb_collapse_tstamp(struct sk_buff *skb,
> +                            const struct sk_buff *next_skb)
>  {
>         const struct skb_shared_info *next_shinfo = skb_shinfo(next_skb);
>         u8 tsflags = next_shinfo->tx_flags & SKBTX_ANY_TSTAMP;
> --
> 2.5.1
>