wireless: add new plugin to get info about OpenWRT's APs

Following info is returned, per AP:
- Signal strength (dBm)
- Number of associated clients

Makefile

@@ -1,4 +1,4 @@
-PLUGINS ?= df cpu if_ if_err_ load memory processes swap netstat uptime interrupts irqstats ntpdate plugindir_
+PLUGINS ?= df cpu if_ if_err_ load memory processes swap netstat uptime interrupts irqstats ntpdate wireless plugindir_
 CONFIGURATION_FILE ?= muninlite.conf
 INPUT_FILE ?= muninlite.in
 TARGET_FILE ?= muninlite

muninlite.in

@@ -86,6 +86,11 @@ for PLUG in $PLUGINS; do
         RES="$RES netstat"
       fi
       ;;
+    wireless)
+      if iwinfo >/dev/null 2>&1; then
+          RES="${RES} ${PLUG}"
+      fi
+      ;;
     plugindir_)
       for MYPLUGIN in $(if [ -d "$PLUGIN_DIRECTORY" ]; then find -L "$PLUGIN_DIRECTORY" -type f -name "$PLUGINPATTERN"; fi); do
         if [ -f "$MYPLUGIN" ] && [ -x "$MYPLUGIN" ]; then

plugins/wireless

@@ -0,0 +1,38 @@
+config_wireless() {
+  interfaces=$(iwinfo 2> /dev/null | sed '/^wlan/!d; s/ .*//g; /-/d')
+  for interface in ${interfaces}
+  do
+    echo "multigraph wireless_${interface}
+graph_title WLAN ${interface} AP Statistics
+graph_vlabel Strength (dBm)
+graph_category network
+graph_scale no
+signal.label Signal
+noise.label Noise"
+  done
+  interfaces=$(iwinfo 2> /dev/null | sed '/^wlan/!d; s/ .*//g')
+  for interface in ${interfaces}
+  do
+    echo "multigraph wireless_assoc_${interface/-/_}
+graph_title WLAN ${interface} associations
+graph_vlabel Clients
+graph_args --lower-limit 0
+graph_category network
+graph_scale no
+clients.label Clients"
+  done
+}
+fetch_wireless() {
+  interfaces=$(iwinfo 2> /dev/null | sed '/^wlan/!d; s/ .*//g; /-/d')
+  for interface in ${interfaces}
+  do
+    echo "multigraph wireless_${interface}"
+    iwinfo ${interface} info | sed -r 's/unknown/0 dBm/g; /Signal.*Noise/!d; s/^.* Signal: ([-0-9]+) dBm  Noise: ([-0-9]+) dBm/signal.value \1\nnoise.value \2/'
+  done
+  interfaces=$(iwinfo 2> /dev/null | sed '/^wlan/!d; s/ .*//g')
+  for interface in ${interfaces}
+  do
+    echo "multigraph wireless_assoc_${interface/-/_}"
+    echo "clients.value $(iwinfo ${interface} assoc | grep -c SNR)"
+  done
+}