ibmvnic: Account for VLAN tag in L2 Header descriptor

If a VLAN tag is present in the Ethernet header, account
for that when providing the L2 header to firmware.
Signed-off-by: NThomas Falcon <tlfalcon@linux.vnet.ibm.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/ibm/ibmvnic.c

@@ -1221,6 +1221,9 @@ static int build_hdr_data(u8 hdr_field, struct sk_buff *skb,
 	int len = 0;
 	u8 *hdr;
 
+	if (skb_vlan_tagged(skb) && !skb_vlan_tag_present(skb))
+		hdr_len[0] = sizeof(struct vlan_ethhdr);
+	else
 		hdr_len[0] = sizeof(struct ethhdr);
 
 	if (skb->protocol == htons(ETH_P_IP)) {