[PATCH 3.12 103/103] net-gro: reset skb->truesize in napi_reuse_skb()

From: Jiri Slaby
Date: Thu May 29 2014 - 09:53:53 EST


From: Eric Dumazet <edumazet@xxxxxxxxxx>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

[ Upstream commit e33d0ba8047b049c9262fdb1fcafb93cb52ceceb ]

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@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
net/core/dev.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/net/core/dev.c b/net/core/dev.c
index 5a50e98aee2c..01d53d62a2ec 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3959,6 +3959,7 @@ 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;
}
--
1.9.3

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