net: Add testing sysfs attribute

Similar to speed, duplex and dorment, report the testing status
in sysfs.
Signed-off-by: Andrew Lunn <andrew@lunn.ch>
Reviewed-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/ABI/testing/sysfs-class-net

@@ -124,6 +124,19 @@ Description:
 		authentication is performed (e.g: 802.1x). 'link_mode' attribute
 		will also reflect the dormant state.
 
+What:		/sys/class/net/<iface>/testing
+Date:		April 2002
+KernelVersion:	5.8
+Contact:	netdev@vger.kernel.org
+Description:
+		Indicates whether the interface is under test. Possible
+		values are:
+		0: interface is not being tested
+		1: interface is being tested
+
+		When an interface is under test, it cannot be expected
+		to pass packets as normal.
+
 What:		/sys/clas/net/<iface>/duplex
 Date:		October 2009
 KernelVersion:	2.6.33

net/core/net-sysfs.c

@@ -243,6 +243,18 @@ static ssize_t duplex_show(struct device *dev,
 }
 static DEVICE_ATTR_RO(duplex);
 
+static ssize_t testing_show(struct device *dev,
+			    struct device_attribute *attr, char *buf)
+{
+	struct net_device *netdev = to_net_dev(dev);
+
+	if (netif_running(netdev))
+		return sprintf(buf, fmt_dec, !!netif_testing(netdev));
+
+	return -EINVAL;
+}
+static DEVICE_ATTR_RO(testing);
+
 static ssize_t dormant_show(struct device *dev,
 			    struct device_attribute *attr, char *buf)
 {
@@ -260,7 +272,7 @@ static const char *const operstates[] = {
 	"notpresent", /* currently unused */
 	"down",
 	"lowerlayerdown",
-	"testing", /* currently unused */
+	"testing",
 	"dormant",
 	"up"
 };
@@ -524,6 +536,7 @@ static struct attribute *net_class_attrs[] __ro_after_init = {
 	&dev_attr_speed.attr,
 	&dev_attr_duplex.attr,
 	&dev_attr_dormant.attr,
+	&dev_attr_testing.attr,
 	&dev_attr_operstate.attr,
 	&dev_attr_carrier_changes.attr,
 	&dev_attr_ifalias.attr,