Re: [PATCH net-next] net: core: Expose number of link up/down transitions

[Andrei Vagin <avagin@virtuozzo.com>]

On Wed, Jan 17, 2018 at 03:06:57PM -0800, Florian Fainelli wrote:
> From: David Decotigny <decot@googlers.com>
> 
> 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), count_link_up (4.16) and count_link_down (4.16)

What is the idea to have two separate counters? Can a delta between them
be a bigger than 1?

> 
> 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>
> ---
>  Documentation/ABI/testing/sysfs-class-net | 24 ++++++++++++++++++++++++
>  include/linux/netdevice.h                 |  6 ++++--
>  include/uapi/linux/if_link.h              |  2 ++
>  net/core/net-sysfs.c                      | 23 ++++++++++++++++++++++-
>  net/core/rtnetlink.c                      | 13 +++++++++++--
>  net/sched/sch_generic.c                   |  4 ++--
>  6 files changed, 65 insertions(+), 7 deletions(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-class-net b/Documentation/ABI/testing/sysfs-class-net
> index 6856da99b6f7..e4b0d5157305 100644
> --- a/Documentation/ABI/testing/sysfs-class-net
> +++ b/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/count_link_up
> +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/count_link_down
> +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
> diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
> index ed0799a12bf2..28f68f7513d0 100644
> --- a/include/linux/netdevice.h
> +++ b/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		count_link_up;
> +	atomic_t		count_link_down;
> +
>  #ifdef CONFIG_WIRELESS_EXT
>  	const struct iw_handler_def *wireless_handlers;
>  	struct iw_public_data	*wireless_data;
> diff --git a/include/uapi/linux/if_link.h b/include/uapi/linux/if_link.h
> index f8f04fed6186..6e44b0674ba4 100644
> --- a/include/uapi/linux/if_link.h
> +++ b/include/uapi/linux/if_link.h
> @@ -161,6 +161,8 @@ enum {
>  	IFLA_EVENT,
>  	IFLA_NEW_NETNSID,
>  	IFLA_IF_NETNSID,
> +	IFLA_COUNT_LINK_UP,
> +	IFLA_COUNT_LINK_DOWN,
>  	__IFLA_MAX
>  };
>  
> diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
> index 7bf8b85ade16..9f732c3dc2ce 100644
> --- a/net/core/net-sysfs.c
> +++ b/net/core/net-sysfs.c
> @@ -295,10 +295,29 @@ 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->count_link_up) +
> +		       atomic_read(&netdev->count_link_down));
>  }
>  static DEVICE_ATTR_RO(carrier_changes);
>  
> +static ssize_t count_link_up_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->count_link_up));
> +}
> +static DEVICE_ATTR_RO(count_link_up);
> +
> +static ssize_t count_link_down_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->count_link_down));
> +}
> +static DEVICE_ATTR_RO(count_link_down);
> +
>  /* read-write attributes */
>  
>  static int change_mtu(struct net_device *dev, unsigned long new_mtu)
> @@ -547,6 +566,8 @@ 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_count_link_up.attr,
> +	&dev_attr_count_link_down.attr,
>  	NULL,
>  };
>  ATTRIBUTE_GROUPS(net_class);
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index 16d644a4f974..68f69a956713 100644
> --- a/net/core/rtnetlink.c
> +++ b/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_COUNT_LINK_UP */
> +	       + nla_total_size(4)  /* IFLA_COUNT_LINK_DOWN */
>  	       + 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->count_link_up) +
> +			atomic_read(&dev->count_link_down)) ||
> +	    nla_put_u8(skb, IFLA_PROTO_DOWN, dev->proto_down) ||
> +	    nla_put_u32(skb, IFLA_COUNT_LINK_UP,
> +			atomic_read(&dev->count_link_up)) ||
> +	    nla_put_u32(skb, IFLA_COUNT_LINK_DOWN,
> +			atomic_read(&dev->count_link_down)))
>  		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_COUNT_LINK_UP]	= { .type = NLA_U32 },
> +	[IFLA_COUNT_LINK_DOWN]	= { .type = NLA_U32 },
>  };
>  
>  static const struct nla_policy ifla_info_policy[IFLA_INFO_MAX+1] = {
> diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
> index ef8b4ecde2ac..28941636afa3 100644
> --- a/net/sched/sch_generic.c
> +++ b/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->count_link_up);
>  		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->count_link_down);
>  		linkwatch_fire_event(dev);
>  	}
>  }
> -- 
> 2.14.1
>