commit 2d3b479df41a10e2f41f9259fcba775bd34de6e4
author david decotigny <decot@googlers.com> Sat Mar 29 09:48:35 2014 -0700
committer David S. Miller <davem@davemloft.net> Mon Mar 31 16:24:52 2014 -0400
tree 517291066c35188a41b005e81904e69865643e76
parent 9c76a114bbef10b4d44bd258006721dd896695dd

net-sysfs: expose number of carrier on/off changes

This allows to monitor carrier on/off transitions and detect link
flapping issues:
 - new /sys/class/net/X/carrier_changes
 - new rtnetlink IFLA_CARRIER_CHANGES (getlink)

Tested:
  - grep . /sys/class/net/*/carrier_changes
    + ip link set dev X down/up
    + plug/unplug cable
  - updated iproute2: prints IFLA_CARRIER_CHANGES
  - iproute2 20121211-2 (debian): unchanged behavior

Signed-off-by: David Decotigny <decot@googlers.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/rtnetlink.c

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index e7c6006..d4ff417 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -822,6 +822,7 @@
 	       + nla_total_size(4) /* IFLA_NUM_RX_QUEUES */
 	       + nla_total_size(1) /* IFLA_OPERSTATE */
 	       + nla_total_size(1) /* IFLA_LINKMODE */
+	       + nla_total_size(4) /* IFLA_CARRIER_CHANGES */
 	       + nla_total_size(ext_filter_mask
 			        & RTEXT_FILTER_VF ? 4 : 0) /* IFLA_NUM_VF */
 	       + rtnl_vfinfo_size(dev, ext_filter_mask) /* IFLA_VFINFO_LIST */
@@ -970,7 +971,9 @@
 	    (dev->qdisc &&
 	     nla_put_string(skb, IFLA_QDISC, dev->qdisc->ops->id)) ||
 	    (dev->ifalias &&
-	     nla_put_string(skb, IFLA_IFALIAS, dev->ifalias)))
+	     nla_put_string(skb, IFLA_IFALIAS, dev->ifalias)) ||
+	    nla_put_u32(skb, IFLA_CARRIER_CHANGES,
+			atomic_read(&dev->carrier_changes)))
 		goto nla_put_failure;
 
 	if (1) {
@@ -1147,6 +1150,7 @@
 	[IFLA_NUM_TX_QUEUES]	= { .type = NLA_U32 },
 	[IFLA_NUM_RX_QUEUES]	= { .type = NLA_U32 },
 	[IFLA_PHYS_PORT_ID]	= { .type = NLA_BINARY, .len = MAX_PHYS_PORT_ID_LEN },
+	[IFLA_CARRIER_CHANGES]	= { .type = NLA_U32 },  /* ignored */
 };
 
 static const struct nla_policy ifla_info_policy[IFLA_INFO_MAX+1] = {