vxlan: implement get_link_ksettings ethtool method

Similar to VLAN and similar drivers, we can forward get_link_ksettings to
the lower dev if we have one to get meaningful speed/duplex data.

Signed-off-by: Matthias Schiffer <mschiffer@universe-factory.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/vxlan.c

@@ -3175,9 +3175,29 @@ static void vxlan_get_drvinfo(struct net_device *netdev,
 	strlcpy(drvinfo->driver, "vxlan", sizeof(drvinfo->driver));
 }
 
+static int vxlan_get_link_ksettings(struct net_device *dev,
+				    struct ethtool_link_ksettings *cmd)
+{
+	struct vxlan_dev *vxlan = netdev_priv(dev);
+	struct vxlan_rdst *dst = &vxlan->default_dst;
+	struct net_device *lowerdev = __dev_get_by_index(vxlan->net,
+							 dst->remote_ifindex);
+
+	if (!lowerdev) {
+		cmd->base.duplex = DUPLEX_UNKNOWN;
+		cmd->base.port = PORT_OTHER;
+		cmd->base.speed = SPEED_UNKNOWN;
+
+		return 0;
+	}
+
+	return __ethtool_get_link_ksettings(lowerdev, cmd);
+}
+
 static const struct ethtool_ops vxlan_ethtool_ops = {
-	.get_drvinfo	= vxlan_get_drvinfo,
-	.get_link	= ethtool_op_get_link,
+	.get_drvinfo		= vxlan_get_drvinfo,
+	.get_link		= ethtool_op_get_link,
+	.get_link_ksettings	= vxlan_get_link_ksettings,
 };
 
 static struct socket *vxlan_create_sock(struct net *net, bool ipv6,