netdev - Re: [PATCH] fix TSO FACK loss marking in tcp_mark_head

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Message-ID: <alpine.DEB.2.00.1009271520560.26447@wel-95.cs.helsinki.fi>
Date:	Mon, 27 Sep 2010 15:22:09 +0300 (EEST)
From:	"Ilpo Järvinen" <ilpo.jarvinen@...sinki.fi>
To:	Yuchung Cheng <ycheng@...gle.com>
cc:	David Miller <davem@...emloft.net>, Netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH] fix TSO FACK loss marking in tcp_mark_head_lost

On Fri, 24 Sep 2010, Yuchung Cheng wrote:

> When TCP uses FACK algorithm to mark lost packets in
> tcp_mark_head_lost(), if the number of packets in the (TSO) skb is
> greater than the number of packets that should be marked lost, TCP
> incorrectly exits the loop and marks no packets lost in the skb. This
> underestimates tp->lost_out and affects the recovery/retransmission.
> This patch fargments the skb and marks the correct amount of packets
> lost.
> 
> Signed-off-by: Yuchung Cheng <ycheng@...gle.com>
> ---
>  net/ipv4/tcp_input.c |    3 ++-
>  1 files changed, 2 insertions(+), 1 deletions(-)
> 
> diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
> index 1bc87a0..e4f472e 100644
> --- a/net/ipv4/tcp_input.c
> +++ b/net/ipv4/tcp_input.c
> @@ -2532,7 +2532,8 @@ static void tcp_mark_head_lost(struct sock *sk, int packets)
>  			cnt += tcp_skb_pcount(skb);
>  
>  		if (cnt > packets) {
> -			if (tcp_is_sack(tp) || (oldcnt >= packets))
> +			if ((tcp_is_sack(tp) && !tcp_is_fack(tp)) ||
> +			    (oldcnt >= packets))
>  				break;
>  
>  			mss = skb_shinfo(skb)->gso_size;
> 

Acked-by: Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>

-- 
 i.