vlan: Warn the user if lowerdev has bad vlan features.

Some drivers incorrectly assign vlan acceleration features to
vlan_features thus causing issues for Q-in-Q vlan configurations.
Warn the user of such cases.

Signed-off-by: Vlad Yasevich <vyasevic@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netdev_features.h b/include/linux/netdev_features.h
index 1005ebf..5a09a48 100644
--- a/include/linux/netdev_features.h
+++ b/include/linux/netdev_features.h
@@ -163,4 +163,11 @@
 /* changeable features with no special hardware requirements */
 #define NETIF_F_SOFT_FEATURES	(NETIF_F_GSO | NETIF_F_GRO)
 
+#define NETIF_F_VLAN_FEATURES	(NETIF_F_HW_VLAN_CTAG_FILTER | \
+				 NETIF_F_HW_VLAN_CTAG_RX | \
+				 NETIF_F_HW_VLAN_CTAG_TX | \
+				 NETIF_F_HW_VLAN_STAG_FILTER | \
+				 NETIF_F_HW_VLAN_STAG_RX | \
+				 NETIF_F_HW_VLAN_STAG_TX)
+
 #endif	/* _LINUX_NETDEV_FEATURES_H */