Bond: Monitor bond mii_status not link operstate (#1124)

With a bond interface the state of the slave interface from the bond's
point of view is reflected in `mii_status` and is independent of the
link's `operstate`.

When a bond is monitored with `miimon`, `mii_status` will reflect the
state of the physical link as configured via the operator.

When a bond is monitored via `arp_interval` the `mii_status` will
reflect the results of the bond ARP checking.  This means the link can
be down from the bond's point of view, but up from a physical
connection point of view.

If a bond is not monitored via miimon or arp, the `mii_status` should
likely be always `up`, however I have observed a case where this is not
true and the `operstate` is `up` while `mii_status` is `down`.  Kernel
bond documentation stresses that a bond should not be configured without
one of `mii_mon` or `arp_interval` configured however.

This change results in the metric 'node_bonding_active' matching the
up/down state of the bond's point of view rather than operstate.

Signed-off-by: Sachi King <nakato@nakato.io>

1 files changed, 2 insertions, 0 deletions

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 77f84cb..6d6abb2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,6 +6,7 @@
   other network metrics #1224
 * The cpufreq metrics now separate the `cpufreq` and `scaling` data based on what the driver provides. #1248
 * The labels for the network_up metric have changed, see issue #1236
+* Bonding collector now uses `mii_status` instead of `operstatus` #1124
 
 ### Changes
 
@@ -21,6 +22,7 @@
 * [FEATURE] Add kstat-based Solaris metrics for boottime, cpu and zfs collectors #1197
 * [FEATURE] Add uname collector for FreeBSD #1239
 * [FEATURE] Add diskstats collector for OpenBSD #1250
+* [CHANGE] Bonding state uses mii_status #1124
 
 ## 0.17.0 / 2018-11-30