path: root/net/core
diff options
authorVlad Yasevich <>2015-11-16 15:43:44 -0500
committerDavid S. Miller <>2015-11-17 14:38:35 -0500
commita6e18ff111701b4ff6947605bfbe9594ec42a6e8 (patch)
treeb6905bc0ea1eadc2a237dcefe3d88f14fd1e00e0 /net/core
parent6c606fa32c4272894248c1abbc15257fc04250be (diff)
vlan: Fix untag operations of stacked vlans with REORDER_HEADER off
When we have multiple stacked vlan devices all of which have turned off REORDER_HEADER flag, the untag operation does not locate the ethernet addresses correctly for nested vlans. The reason is that in case of REORDER_HEADER flag being off, the outer vlan headers are put back and the mac_len is adjusted to account for the presense of the header. Then, the subsequent untag operation, for the next level vlan, always use VLAN_ETH_HLEN to locate the begining of the ethernet header and that ends up being a multiple of 4 bytes short of the actuall beginning of the mac header (the multiple depending on the how many vlan encapsulations ethere are). As a reslult, if there are multiple levles of vlan devices with REODER_HEADER being off, the recevied packets end up being dropped. To solve this, we use skb->mac_len as the offset. The value is always set on receive path and starts out as a ETH_HLEN. The value is also updated when the vlan header manupations occur so we know it will be correct. Signed-off-by: Vladislav Yasevich <> Signed-off-by: David S. Miller <>
Diffstat (limited to 'net/core')
1 files changed, 2 insertions, 1 deletions
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index aa41e6dd6429..152b9c70e252 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -4268,7 +4268,8 @@ static struct sk_buff *skb_reorder_vlan_header(struct sk_buff *skb)
return NULL;
- memmove(skb->data - ETH_HLEN, skb->data - VLAN_ETH_HLEN, 2 * ETH_ALEN);
+ memmove(skb->data - ETH_HLEN, skb->data - skb->mac_len,
+ 2 * ETH_ALEN);
skb->mac_header += VLAN_HLEN;
return skb;