vxlan: Add tx-vlan offload support.

Following patch allows transmit side vlan offload for vxlan
devices.
Signed-off-by: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/vxlan.c

@@ -27,6 +27,7 @@
 #include <linux/igmp.h>
 #include <linux/etherdevice.h>
 #include <linux/if_ether.h>
+#include <linux/if_vlan.h>
 #include <linux/hash.h>
 #include <linux/ethtool.h>
 #include <net/arp.h>
@@ -1139,13 +1140,23 @@ int vxlan_xmit_skb(struct net *net, struct vxlan_sock *vs,
 	}
 
 	min_headroom = LL_RESERVED_SPACE(rt->dst.dev) + rt->dst.header_len
-			+ VXLAN_HLEN + sizeof(struct iphdr);
+			+ VXLAN_HLEN + sizeof(struct iphdr)
+			+ (vlan_tx_tag_present(skb) ? VLAN_HLEN : 0);
 
 	/* Need space for new headers (invalidates iph ptr) */
 	err = skb_cow_head(skb, min_headroom);
 	if (unlikely(err))
 		return err;
 
+	if (vlan_tx_tag_present(skb)) {
+		if (WARN_ON(!__vlan_put_tag(skb,
+					    skb->vlan_proto,
+					    vlan_tx_tag_get(skb))))
+			return -ENOMEM;
+
+		skb->vlan_tci = 0;
+	}
+
 	vxh = (struct vxlanhdr *) __skb_push(skb, sizeof(*vxh));
 	vxh->vx_flags = htonl(VXLAN_FLAGS);
 	vxh->vx_vni = vni;
@@ -1560,8 +1571,11 @@ static void vxlan_setup(struct net_device *dev)
 	dev->features   |= NETIF_F_RXCSUM;
 	dev->features   |= NETIF_F_GSO_SOFTWARE;
 
+	dev->vlan_features = dev->features;
+	dev->features |= NETIF_F_HW_VLAN_CTAG_TX | NETIF_F_HW_VLAN_STAG_TX;
 	dev->hw_features |= NETIF_F_SG | NETIF_F_HW_CSUM | NETIF_F_RXCSUM;
 	dev->hw_features |= NETIF_F_GSO_SOFTWARE;
+	dev->hw_features |= NETIF_F_HW_VLAN_CTAG_TX | NETIF_F_HW_VLAN_STAG_TX;
 	dev->priv_flags	&= ~IFF_XMIT_DST_RELEASE;
 	dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;