Patch "tcp: fix double-counted receiver RTT when leaving receiver fast path" has been added to the 3.8-stable tree

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This is a note to let you know that I've just added the patch titled

    tcp: fix double-counted receiver RTT when leaving receiver fast path

to the 3.8-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     tcp-fix-double-counted-receiver-rtt-when-leaving-receiver-fast-path.patch
and it can be found in the queue-3.8 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.


>From 2d2809452253a92adcabba4d897bf58a5c9794fb Mon Sep 17 00:00:00 2001
From: Neal Cardwell <ncardwell@xxxxxxxxxx>
Date: Mon, 4 Mar 2013 06:23:05 +0000
Subject: tcp: fix double-counted receiver RTT when leaving receiver fast path


From: Neal Cardwell <ncardwell@xxxxxxxxxx>

[ Upstream commit aab2b4bf224ef8358d262f95b568b8ad0cecf0a0 ]

We should not update ts_recent and call tcp_rcv_rtt_measure_ts() both
before and after going to step5. That wastes CPU and double-counts the
receiver-side RTT sample.

Signed-off-by: Neal Cardwell <ncardwell@xxxxxxxxxx>
Acked-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/ipv4/tcp_input.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5498,6 +5498,9 @@ int tcp_rcv_established(struct sock *sk,
 				if (tcp_checksum_complete_user(sk, skb))
 					goto csum_error;
 
+				if ((int)skb->truesize > sk->sk_forward_alloc)
+					goto step5;
+
 				/* Predicted packet is in window by definition.
 				 * seq == rcv_nxt and rcv_wup <= rcv_nxt.
 				 * Hence, check seq<=rcv_wup reduces to:
@@ -5509,9 +5512,6 @@ int tcp_rcv_established(struct sock *sk,
 
 				tcp_rcv_rtt_measure_ts(sk, skb);
 
-				if ((int)skb->truesize > sk->sk_forward_alloc)
-					goto step5;
-
 				NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITS);
 
 				/* Bulk data transfer: receiver */


Patches currently in stable-queue which might be from ncardwell@xxxxxxxxxx are

queue-3.8/tcp-fix-double-counted-receiver-rtt-when-leaving-receiver-fast-path.patch
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