xen-netback: add software timestamp capabilities

Add software timestamp capabilities to the xen-netback driver
by advertising it on the struct ethtool_ops and calling
skb_tx_timestamp before passing the buffer to the queue.
Signed-off-by: Luca Fancellu <luca.fancellu@arm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/xen-netback/interface.c

@@ -252,6 +252,9 @@ xenvif_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	if (vif->hash.alg == XEN_NETIF_CTRL_HASH_ALGORITHM_NONE)
 		skb_clear_hash(skb);
 
+	/* timestamp packet in software */
+	skb_tx_timestamp(skb);
+
 	if (!xenvif_rx_queue_tail(queue, skb))
 		goto drop;
 
@@ -458,7 +461,7 @@ static void xenvif_get_strings(struct net_device *dev, u32 stringset, u8 * data)
 
 static const struct ethtool_ops xenvif_ethtool_ops = {
 	.get_link	= ethtool_op_get_link,
-
+	.get_ts_info 	= ethtool_op_get_ts_info,
 	.get_sset_count = xenvif_get_sset_count,
 	.get_ethtool_stats = xenvif_get_ethtool_stats,
 	.get_strings = xenvif_get_strings,