linux-kernel - Re: [PATCH v1] net-sysfs: expose number of link up/down transitions

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Date:	Fri, 28 Mar 2014 09:51:03 -0700
From:	Florian Fainelli <f.fainelli@...il.com>
To:	Jiri Pirko <jiri@...nulli.us>
Cc:	David Decotigny <decot@...glers.com>,
	"David S. Miller" <davem@...emloft.net>,
	Jamal Hadi Salim <jhs@...atatu.com>,
	netdev <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Eric Dumazet <edumazet@...gle.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Weilong Chen <chenweilong@...wei.com>,
	Amir Vadai <amirv@...lanox.com>,
	Michael Dalton <mwdalton@...gle.com>,
	Al Viro <viro@...iv.linux.org.uk>, Tejun Heo <tj@...nel.org>
Subject: Re: [PATCH v1] net-sysfs: expose number of link up/down transitions

2014-03-27 23:25 GMT-07:00 Jiri Pirko <jiri@...nulli.us>:
> Fri, Mar 28, 2014 at 05:35:00AM CET, decot@...glers.com wrote:
>>Tested:
>>  grep . /sys/class/net/*/count_link_*
>>  + ip link set dev X down/up
>>
>>Signed-off-by: David Decotigny <decot@...glers.com>
>>---
>> include/linux/netdevice.h |  4 ++++
>> net/core/net-sysfs.c      | 18 ++++++++++++++++++
>> net/sched/sch_generic.c   |  2 ++
>> 3 files changed, 24 insertions(+)
>>
>>diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
>>index 4b6d12c..cf52869 100644
>>--- a/include/linux/netdevice.h
>>+++ b/include/linux/netdevice.h
>>@@ -1315,6 +1315,10 @@ struct net_device {
>>                                            * Do not use this in drivers.
>>                                            */
>>
>>+      /* Stats to monitor link on/off, flapping */
>>+      atomic_t                count_link_up;
>>+      atomic_t                count_link_down;
>>+
>> #ifdef CONFIG_WIRELESS_EXT
>>       /* List of functions to handle Wireless Extensions (instead of ioctl).
>>        * See <net/iw_handler.h> for details. Jean II */
>>diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
>>index daed9a6..a65ac54 100644
>>--- a/net/core/net-sysfs.c
>>+++ b/net/core/net-sysfs.c
>>@@ -253,6 +253,22 @@ static ssize_t operstate_show(struct device *dev,
>> }
>> static DEVICE_ATTR_RO(operstate);
>>
>>+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 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_up);
>>+static DEVICE_ATTR_RO(count_link_down);
>>+
>
>
> If this is exposed in sysfs, this needs to be exposed via RT netlink as
> well.

This makes me wonder if this really needs to be a kernel-maintained
pair of counters. Since this seems to be useful for monitoring e.g:
servers for link flapping, I would assume that some user-space
script/program does read these sysfs entries periodically to report a
healthy link. If that's the case, what prevents the same
script/program from listening to netlink events and count the link
UP/DOWN events from there and report that?

>
>
>> /* read-write attributes */
>>
>> static int change_mtu(struct net_device *net, unsigned long new_mtu)
>>@@ -386,6 +402,8 @@ static struct attribute *net_class_attrs[] = {
>>       &dev_attr_duplex.attr,
>>       &dev_attr_dormant.attr,
>>       &dev_attr_operstate.attr,
>>+      &dev_attr_count_link_up.attr,
>>+      &dev_attr_count_link_down.attr,
>>       &dev_attr_ifalias.attr,
>>       &dev_attr_carrier.attr,
>>       &dev_attr_mtu.attr,
>>diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
>>index e82e43b..2d06943 100644
>>--- a/net/sched/sch_generic.c
>>+++ b/net/sched/sch_generic.c
>>@@ -310,6 +310,7 @@ 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->count_link_up);
>>               linkwatch_fire_event(dev);
>>               if (netif_running(dev))
>>                       __netdev_watchdog_up(dev);
>>@@ -328,6 +329,7 @@ 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->count_link_down);
>>               linkwatch_fire_event(dev);
>>       }
>> }
>>--
>>1.9.1.423.g4596e3a
>>
> --
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-- 
Florian
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