8021q: set hard_header_len when VLAN offload features are toggled

Toggling the vlan tx|rx hw offloads needs to set the hard_header_len
as well otherwise we end up using LL_RESERVED_SPACE incorrectly.
This results in pskb_expand_head() being used unnecessarily.
Signed-off-by: NJohn Fastabend <john.r.fastabend@intel.com>
Acked-by: NJesse Gross <jesse@nicira.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/8021q/vlan.c

@@ -334,6 +334,12 @@ static void vlan_transfer_features(struct net_device *dev,
 	vlandev->features &= ~dev->vlan_features;
 	vlandev->features |= dev->features & dev->vlan_features;
 	vlandev->gso_max_size = dev->gso_max_size;
+
+	if (dev->features & NETIF_F_HW_VLAN_TX)
+		vlandev->hard_header_len = dev->hard_header_len;
+	else
+		vlandev->hard_header_len = dev->hard_header_len + VLAN_HLEN;
+
 #if defined(CONFIG_FCOE) || defined(CONFIG_FCOE_MODULE)
 	vlandev->fcoe_ddp_xid = dev->fcoe_ddp_xid;
 #endif