netdev - [PATCH v3] tcp: properly update lost_cnt

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Message-ID: <4E88737E.5030906@intel.com>
Date:	Sun, 02 Oct 2011 22:21:50 +0800
From:	"Yan, Zheng" <zheng.z.yan@...el.com>
To:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>,
	Nandita Dukkipati <nanditad@...gle.com>, ycheng@...gle.com,
	"davem@...emloft.net" <davem@...emloft.net>
Subject: [PATCH v3] tcp: properly update lost_cnt_hint during shifting

lost_skb_hint is used by tcp_mark_head_lost() to mark the first unhandled skb.
lost_cnt_hint is the number of packets or sacked packets before the lost_skb_hint;
When shifting a skb that is before the lost_skb_hint, if tcp_is_fack() is ture,
the skb has already been counted in the lost_cnt_hint; if tcp_is_fack() is false,
tcp_sacktag_one() will increase the lost_cnt_hint. So tcp_shifted_skb() does not
need to adjust the lost_cnt_hint by itself. When shifting a skb that is equal to
lost_skb_hint, the shifted packets will not be counted by tcp_mark_head_lost().
So tcp_shifted_skb() should adjust the lost_cnt_hint even tcp_is_fack(tp) is true.

Signed-off-by: Zheng Yan <zheng.z.yan@...el.com>
---
Changes since v2:
 adjust the lost_cnt_hint even tcp_is_fack(tp) is true.

 net/ipv4/tcp_input.c |    4 +---
 1 files changed, 1 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 21fab3e..d73aab3 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1389,9 +1389,7 @@ static int tcp_shifted_skb(struct sock *sk, struct sk_buff *skb,

 	BUG_ON(!pcount);

-	/* Tweak before seqno plays */
-	if (!tcp_is_fack(tp) && tcp_is_sack(tp) && tp->lost_skb_hint &&
-	    !before(TCP_SKB_CB(tp->lost_skb_hint)->seq, TCP_SKB_CB(skb)->seq))
+	if (skb == tp->lost_skb_hint)
 		tp->lost_cnt_hint += pcount;

 	TCP_SKB_CB(prev)->end_seq += shifted;
-- 
1.7.4.4
--
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