check_openwrt_wlan_clients.sh

#!/bin/ash
# to keep track of the amount of clients associated to an OpenWrt AccessPoint
# dependency is the iw package
# it automatically finds all wifi adapter-names by parsing them from ifconfig's output
# you can also define the states for disabled wifi and some client thresholds
# output is containing wifi state, transmit power and number of clients and the mac addresses of those
# for dual band you may need to run this twice for each band to keep those client numbers separated...

FILTER="wlan" #search-filter for autodetection, e.g. 'wlan' or 'ath' depending on your hardware
NAME="WLAN-Stations" #the check's name in Check_MK
WARN_CLIENTS=6 #threshold for WARNING state
CRIT_CLIENTS=8 #threshold for CRITIAL state
STATE_DISABLED=0 #state if wifi is detected as disabled, 0 = OK, 1 = WARN, 2 = CRIT, 3 = UNKNOWN

####

CLIENTS=$(ifconfig | grep $FILTER | awk {'print $1'} | while read line ; do iw dev $line station dump | grep "Station" ; done | wc -l)
if [ $CLIENTS -lt $WARN_CLIENTS ]; then
	STATE=0
elif [ $CLIENTS -ge $WARN_CLIENTS ] && [ $CLIENTS -lt CRIT_CLIENTS ]; then
	STATE=1
elif [ $CLIENTS -ge $CRIT_CLIENTS ]; then
	STATE=2
else
	STATE=3
fi

if [ $(uci get wireless.radio0.disabled) == 1 ] ; then
	DESCRIPTION="WLAN is disabled!"
	STATE=$STATE_DISABLED
else
	DESCRIPTION="$(uci get wireless.radio0.txpower) dBm, $CLIENTS Clients: $CLIENTS"
fi

echo "$STATE $NAME clients=$CLIENTS $DESCRIPTION"