[3.11.y.z extended stable] Patch "net-gro: reset skb->truesize in napi_reuse_skb()" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    net-gro: reset skb->truesize in napi_reuse_skb()

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From a5fcb6c6cc1a1b0bc03ba8132b878253d6d5f201 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet at google.com>
Date: Thu, 3 Apr 2014 09:28:10 -0700
Subject: net-gro: reset skb->truesize in napi_reuse_skb()

commit e33d0ba8047b049c9262fdb1fcafb93cb52ceceb upstream.

Recycling skb always had been very tough...

This time it appears GRO layer can accumulate skb->truesize
adjustments made by drivers when they attach a fragment to skb.

skb_gro_receive() can only subtract from skb->truesize the used part
of a fragment.

I spotted this problem seeing TcpExtPruneCalled and
TcpExtTCPRcvCollapsed that were unexpected with a recent kernel, where
TCP receive window should be sized properly to accept traffic coming
from a driver not overshooting skb->truesize.

Signed-off-by: Eric Dumazet <edumazet at google.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 net/core/dev.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/core/dev.c b/net/core/dev.c
index ab07f35d0f38..363e06e58c81 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3962,6 +3962,7 @@ static void napi_reuse_skb(struct napi_struct *napi, struct sk_buff *skb)
 	skb->vlan_tci = 0;
 	skb->dev = napi->dev;
 	skb->skb_iif = 0;
+	skb->truesize = SKB_TRUESIZE(skb_end_offset(skb));

 	napi->skb = skb;
 }
--
1.9.1