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 3.4-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-3.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From dde9364409613d724007a54f92f6b6d0f1945f4a 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
@@ -5519,6 +5519,9 @@ 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:
@@ -5530,9 +5533,6 @@ 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-3.4/tcp-fix-double-counted-receiver-rtt-when-leaving-receiver-fast-path.patch
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