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Date:	Tue,  2 Oct 2012 18:14:17 +0200
From:	Antonio Quartulli <>
To:	Patrick McHardy <>
Cc:	"David S. Miller" <>,,
	Antonio Quartulli <>
Subject: [PATCH net] 8021q: fix mac_len recomputation in vlan_untag()

skb_reset_mac_len() relies on the value of the skb->network_header pointer,
therefore we must wait for such pointer to be recalculated before computing
the new mac_len value.

Signed-off-by: Antonio Quartulli <>

* such bug has been found because in the batman-adv module we do check the value
of mac_len to drop bad packets and we realised that all packets coming from the
untagging procedure (so coming from any eth0.x) were being dropped.

* I'd consider this patch to be submitted to stable


 net/8021q/vlan_core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/8021q/vlan_core.c b/net/8021q/vlan_core.c
index 8ca533c..830059d 100644
--- a/net/8021q/vlan_core.c
+++ b/net/8021q/vlan_core.c
@@ -105,7 +105,6 @@ static struct sk_buff *vlan_reorder_header(struct sk_buff *skb)
 		return NULL;
 	memmove(skb->data - ETH_HLEN, skb->data - VLAN_ETH_HLEN, 2 * ETH_ALEN);
 	skb->mac_header += VLAN_HLEN;
-	skb_reset_mac_len(skb);
 	return skb;
@@ -139,6 +138,8 @@ struct sk_buff *vlan_untag(struct sk_buff *skb)
+	skb_reset_mac_len(skb);
 	return skb;

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