diff --git a/net/openvswitch/vport.c b/net/openvswitch/vport.c
index 6b21fd0..8f19843 100644
--- a/net/openvswitch/vport.c
+++ b/net/openvswitch/vport.c
@@ -485,9 +485,14 @@
 {
 	unsigned int length = skb->len - ETH_HLEN;
 
-	if (skb->protocol == htons(ETH_P_8021Q))
+	if (skb_vlan_tagged(skb))
 		length -= VLAN_HLEN;
 
+	/* Don't subtract for multiple VLAN tags. Most (all?) drivers allow
+	 * (ETH_LEN + VLAN_HLEN) in addition to the mtu value, but almost none
+	 * account for 802.1ad. e.g. is_skb_forwardable().
+	 */
+
 	return length;
 }