veth: add software timestamping

Provide a software TX timestamp as well as the ethtool query interface
and report the software timestamp capabilities.

Tested with "ethtool -T" and two linuxptp instances each bound to a
tunnel endpoint.
Signed-off-by: Michael Walle <michael@walle.cc>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/veth.c

@@ -24,6 +24,7 @@
 #include <linux/filter.h>
 #include <linux/ptr_ring.h>
 #include <linux/bpf_trace.h>
+#include <linux/net_tstamp.h>
 
 #define DRV_NAME	"veth"
 #define DRV_VERSION	"1.0"
@@ -114,6 +115,18 @@ static void veth_get_ethtool_stats(struct net_device *dev,
 	data[0] = peer ? peer->ifindex : 0;
 }
 
+static int veth_get_ts_info(struct net_device *dev,
+			    struct ethtool_ts_info *info)
+{
+	info->so_timestamping =
+		SOF_TIMESTAMPING_TX_SOFTWARE |
+		SOF_TIMESTAMPING_RX_SOFTWARE |
+		SOF_TIMESTAMPING_SOFTWARE;
+	info->phc_index = -1;
+
+	return 0;
+}
+
 static const struct ethtool_ops veth_ethtool_ops = {
 	.get_drvinfo		= veth_get_drvinfo,
 	.get_link		= ethtool_op_get_link,
@@ -121,6 +134,7 @@ static const struct ethtool_ops veth_ethtool_ops = {
 	.get_sset_count		= veth_get_sset_count,
 	.get_ethtool_stats	= veth_get_ethtool_stats,
 	.get_link_ksettings	= veth_get_link_ksettings,
+	.get_ts_info		= veth_get_ts_info,
 };
 
 /* general routines */
@@ -201,6 +215,7 @@ static netdev_tx_t veth_xmit(struct sk_buff *skb, struct net_device *dev)
 			skb_record_rx_queue(skb, rxq);
 	}
 
+	skb_tx_timestamp(skb);
 	if (likely(veth_forward_skb(rcv, skb, rq, rcv_xdp) == NET_RX_SUCCESS)) {
 		struct pcpu_vstats *stats = this_cpu_ptr(dev->vstats);