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

[ 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@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/net/core/dev.c b/net/core/dev.c
index 7bcf37d..854da15 100644 (file)
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -3648,6 +3648,7 @@ 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;
 }