veth: extend features to support tunneling

While investigating on a recent vxlan regression, I found veth
was using a zero features set for vxlan tunnels.

We have to segment GSO frames, copy the payload, and do the checksum.

This patch brings a ~200% performance increase

We probably have to add hw_enc_features support
on other virtual devices.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/veth.c

@@ -261,6 +261,8 @@ static const struct net_device_ops veth_netdev_ops = {
 
 #define VETH_FEATURES (NETIF_F_SG | NETIF_F_FRAGLIST | NETIF_F_ALL_TSO |    \
 		       NETIF_F_HW_CSUM | NETIF_F_RXCSUM | NETIF_F_HIGHDMA | \
+		       NETIF_F_GSO_GRE | NETIF_F_GSO_UDP_TUNNEL |	    \
+		       NETIF_F_GSO_IPIP | NETIF_F_GSO_SIT | NETIF_F_UFO	|   \
 		       NETIF_F_HW_VLAN_CTAG_TX | NETIF_F_HW_VLAN_CTAG_RX | \
 		       NETIF_F_HW_VLAN_STAG_TX | NETIF_F_HW_VLAN_STAG_RX )
 
@@ -279,6 +281,7 @@ static void veth_setup(struct net_device *dev)
 	dev->destructor = veth_dev_free;
 
 	dev->hw_features = VETH_FEATURES;
+	dev->hw_enc_features = VETH_FEATURES;
 }
 
 /*