new network plugin added: wireless_channel_occupation

This plugin tracks the occupation of the shared medium (wifi channel).
It uses the "iw" tool for extracting the time slices spent by
the wireless driver receiving, transmitting or ignoring (noise) on the
current channel. This ratio is a good indication for the remaining
capacity of the shared communication medium.

plugins/network/wireless_channel_occupation_

@@ -0,0 +1,105 @@
+#!/bin/sh
+#
+# Monitor the wifi channel occupation (taken from "iw dev wlan0 survey dump").
+#
+# Symlink this plugin with the name of the wifi interface added (e.g. "wlan0").
+#
+#
+# Copyright (C) 2015 Lars Kruse <devel@sumpfralle.de>
+#
+#    This program is free software: you can redistribute it and/or modify
+#    it under the terms of the GNU General Public License as published by
+#    the Free Software Foundation, either version 3 of the License, or
+#    (at your option) any later version.
+#
+#    This program is distributed in the hope that it will be useful,
+#    but WITHOUT ANY WARRANTY; without even the implied warranty of
+#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+#    GNU General Public License for more details.
+#
+#    You should have received a copy of the GNU General Public License
+#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#
+# Magic markers
+#%# capabilities=autoconf suggest
+#%# family=auto
+
+set -eu
+
+
+SCRIPT_PREFIX="wireless_channel_occupation_"
+
+
+clean_fieldname() {
+	echo "$1" | sed 's/^\([^A-Za-z_]\)/_\1/; s/[^A-Za-z0-9_]/_/g'
+}
+
+
+get_wifi_devices() {
+	iw dev | grep Interface | awk '{print $2}'
+}
+
+
+get_wifi_device_from_suffix() {
+	local suffix
+	local called
+	called=$(basename "$0")
+	suffix="${called#$SCRIPT_PREFIX}"
+	# empty result if the prefix did not match (and was not removed)
+	[ "$suffix" = "$0" ] && echo "" || echo "$suffix"
+}
+
+
+if [ "${1:-}" = "autoconf" ]; then
+	if which iw 2>/dev/null; then
+		if [ -n "$(get_wifi_devices)" ]; then
+			echo "yes"
+		else
+			echo "no (missing wifi devices)"
+		fi
+	else
+		echo "no (missing 'iw' dependency)"
+	fi
+elif [ "${1:-}" = "suggest" ]; then
+	get_wifi_devices
+elif [ "${1:-}" = "config" ]; then
+	device=$(get_wifi_device_from_suffix)
+	[ -z "$device" ] && echo >&2 "Invalid wifi device name given" && exit 1
+	echo "graph_title Channel Occupation of $device"
+	echo "graph_vlabel %"
+	echo "graph_category wireless"
+	echo "graph_args --base 1000 -r --lower-limit 0 --upper-limit 100"
+	dev_field=$(clean_fieldname "$device")
+
+	# active: listening time on this channel (usually: 5 minutes = 300000ms)
+	echo "${dev_field}_active.label Transmit"
+	echo "${dev_field}_active.type DERIVE"
+	echo "${dev_field}_active.graph no"
+
+	# busy = receive + transmit + unknown
+	echo "${dev_field}_busy.label unknown"
+	echo "${dev_field}_busy.type DERIVE"
+	echo "${dev_field}_busy.draw AREA"
+	echo "${dev_field}_busy.cdef 100,1,${dev_field}_active,${dev_field}_busy,${dev_field}_receive,${dev_field}_transmit,+,-,/,/,*"
+
+	# receive: this radio receives traffic for itself
+	echo "${dev_field}_receive.label Receive"
+	echo "${dev_field}_receive.type DERIVE"
+	echo "${dev_field}_receive.draw STACK"
+	echo "${dev_field}_receive.cdef 100,${dev_field}_receive,${dev_field}_active,/,*"
+
+	# transmit: this radio transmits traffic
+	echo "${dev_field}_transmit.label Transmit"
+	echo "${dev_field}_transmit.type DERIVE"
+	echo "${dev_field}_transmit.draw STACK"
+	echo "${dev_field}_transmit.cdef 100,${dev_field}_transmit,${dev_field}_active,/,*"
+else
+	device=$(get_wifi_device_from_suffix)
+	[ -z "$device" ] && echo >&2 "Invalid wifi device name given" && exit 1
+	iw dev "$device" survey dump \
+		| grep -F -A 5 "[in use]" \
+		| grep -E "channel (busy|receive|transmit|active) time:" \
+		| awk '{print "'${device}_'"$2"'.value'",$4}'
+fi
+
+exit 0