net: core: Expose number of link up/down transitions

Expose the number of times the link has been going UP or DOWN, and
update the "carrier_changes" counter to be the sum of these two events.
While at it, also update the sysfs-class-net documentation to cover:
carrier_changes (3.15), carrier_up_count (4.16) and carrier_down_count
(4.16)

Signed-off-by: David Decotigny <decot@googlers.com>
[Florian:
* rebase
* add documentation
* merge carrier_changes with up/down counters]
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/ABI/testing/sysfs-class-net

@@ -259,3 +259,27 @@ Contact:	netdev@vger.kernel.org
 Description:
 		Symbolic link to the PHY device this network device is attached
 		to.
+
+What:		/sys/class/net/<iface>/carrier_changes
+Date:		Mar 2014
+KernelVersion:	3.15
+Contact:	netdev@vger.kernel.org
+Description:
+		32-bit unsigned integer counting the number of times the link has
+		seen a change from UP to DOWN and vice versa
+
+What:		/sys/class/net/<iface>/carrier_up_count
+Date:		Jan 2018
+KernelVersion:	4.16
+Contact:	netdev@vger.kernel.org
+Description:
+		32-bit unsigned integer counting the number of times the link has
+		been up
+
+What:		/sys/class/net/<iface>/carrier_down_count
+Date:		Jan 2018
+KernelVersion:	4.16
+Contact:	netdev@vger.kernel.org
+Description:
+		32-bit unsigned integer counting the number of times the link has
+		been down

include/linux/netdevice.h

@@ -1680,8 +1680,6 @@ struct net_device {
 	unsigned long		base_addr;
 	int			irq;
 
-	atomic_t		carrier_changes;
-
 	/*
 	 *	Some hardware also needs these fields (state,dev_list,
 	 *	napi_list,unreg_list,close_list) but they are not
@@ -1719,6 +1717,10 @@ struct net_device {
 	atomic_long_t		tx_dropped;
 	atomic_long_t		rx_nohandler;
 
+	/* Stats to monitor link on/off, flapping */
+	atomic_t		carrier_up_count;
+	atomic_t		carrier_down_count;
+
 #ifdef CONFIG_WIRELESS_EXT
 	const struct iw_handler_def *wireless_handlers;
 	struct iw_public_data	*wireless_data;

include/uapi/linux/if_link.h

@@ -161,6 +161,8 @@ enum {
 	IFLA_EVENT,
 	IFLA_NEW_NETNSID,
 	IFLA_IF_NETNSID,
+	IFLA_CARRIER_UP_COUNT,
+	IFLA_CARRIER_DOWN_COUNT,
 	__IFLA_MAX
 };
 

net/core/net-sysfs.c

@@ -295,10 +295,31 @@ static ssize_t carrier_changes_show(struct device *dev,
 	struct net_device *netdev = to_net_dev(dev);
 
 	return sprintf(buf, fmt_dec,
-		       atomic_read(&netdev->carrier_changes));
+		       atomic_read(&netdev->carrier_up_count) +
+		       atomic_read(&netdev->carrier_down_count));
 }
 static DEVICE_ATTR_RO(carrier_changes);
 
+static ssize_t carrier_up_count_show(struct device *dev,
+				     struct device_attribute *attr,
+				     char *buf)
+{
+	struct net_device *netdev = to_net_dev(dev);
+
+	return sprintf(buf, fmt_dec, atomic_read(&netdev->carrier_up_count));
+}
+static DEVICE_ATTR_RO(carrier_up_count);
+
+static ssize_t carrier_down_count_show(struct device *dev,
+				       struct device_attribute *attr,
+				       char *buf)
+{
+	struct net_device *netdev = to_net_dev(dev);
+
+	return sprintf(buf, fmt_dec, atomic_read(&netdev->carrier_down_count));
+}
+static DEVICE_ATTR_RO(carrier_down_count);
+
 /* read-write attributes */
 
 static int change_mtu(struct net_device *dev, unsigned long new_mtu)
@@ -547,6 +568,8 @@ static struct attribute *net_class_attrs[] __ro_after_init = {
 	&dev_attr_phys_port_name.attr,
 	&dev_attr_phys_switch_id.attr,
 	&dev_attr_proto_down.attr,
+	&dev_attr_carrier_up_count.attr,
+	&dev_attr_carrier_down_count.attr,
 	NULL,
 };
 ATTRIBUTE_GROUPS(net_class);

net/core/rtnetlink.c

@@ -990,6 +990,8 @@ static noinline size_t if_nlmsg_size(const struct net_device *dev,
 	       + nla_total_size(4)  /* IFLA_NEW_NETNSID */
 	       + nla_total_size(1)  /* IFLA_PROTO_DOWN */
 	       + nla_total_size(4)  /* IFLA_IF_NETNSID */
+	       + nla_total_size(4)  /* IFLA_CARRIER_UP_COUNT */
+	       + nla_total_size(4)  /* IFLA_CARRIER_DOWN_COUNT */
 	       + 0;
 }
 
@@ -1551,8 +1553,13 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb,
 	     nla_put_string(skb, IFLA_QDISC, dev->qdisc->ops->id)) ||
 	    nla_put_ifalias(skb, dev) ||
 	    nla_put_u32(skb, IFLA_CARRIER_CHANGES,
-			atomic_read(&dev->carrier_changes)) ||
-	    nla_put_u8(skb, IFLA_PROTO_DOWN, dev->proto_down))
+			atomic_read(&dev->carrier_up_count) +
+			atomic_read(&dev->carrier_down_count)) ||
+	    nla_put_u8(skb, IFLA_PROTO_DOWN, dev->proto_down) ||
+	    nla_put_u32(skb, IFLA_CARRIER_UP_COUNT,
+			atomic_read(&dev->carrier_up_count)) ||
+	    nla_put_u32(skb, IFLA_CARRIER_DOWN_COUNT,
+			atomic_read(&dev->carrier_down_count)))
 		goto nla_put_failure;
 
 	if (event != IFLA_EVENT_NONE) {
@@ -1656,6 +1663,8 @@ static const struct nla_policy ifla_policy[IFLA_MAX+1] = {
 	[IFLA_EVENT]		= { .type = NLA_U32 },
 	[IFLA_GROUP]		= { .type = NLA_U32 },
 	[IFLA_IF_NETNSID]	= { .type = NLA_S32 },
+	[IFLA_CARRIER_UP_COUNT]	= { .type = NLA_U32 },
+	[IFLA_CARRIER_DOWN_COUNT] = { .type = NLA_U32 },
 };
 
 static const struct nla_policy ifla_info_policy[IFLA_INFO_MAX+1] = {

net/sched/sch_generic.c

@@ -510,7 +510,7 @@ void netif_carrier_on(struct net_device *dev)
 	if (test_and_clear_bit(__LINK_STATE_NOCARRIER, &dev->state)) {
 		if (dev->reg_state == NETREG_UNINITIALIZED)
 			return;
-		atomic_inc(&dev->carrier_changes);
+		atomic_inc(&dev->carrier_up_count);
 		linkwatch_fire_event(dev);
 		if (netif_running(dev))
 			__netdev_watchdog_up(dev);
@@ -529,7 +529,7 @@ void netif_carrier_off(struct net_device *dev)
 	if (!test_and_set_bit(__LINK_STATE_NOCARRIER, &dev->state)) {
 		if (dev->reg_state == NETREG_UNINITIALIZED)
 			return;
-		atomic_inc(&dev->carrier_changes);
+		atomic_inc(&dev->carrier_down_count);
 		linkwatch_fire_event(dev);
 	}
 }