wireless_signal_noise_: various improvements

* add perldoc header
* support dirty config
* support "arp" (tool) and /proc/net/arp
* fix autoconf handling

plugins/wifi/wireless_signal_noise_

@@ -1,23 +1,59 @@
 #!/bin/sh
-#
+
-# Show current signal strength and noise for all connected peers of wifi devices.
+: << =cut
-# This plugin is suitable for wifi interfaces with a stable selection of peers
+
-# (e.g. infrastructure).
+=head1 NAME
-# Author: Lars Kruse, devel@sumpfralle.de
+
-# License: GPL v3 or later
+wireless_signal_noise_ - Show signal strength and noise for all connected peers of wifi interface
-#
+
-# Requirements:
+=head1 APPLICABLE SYSTEMS
-#  * "iwinfo" tool (alternatively: fall back to "iw" - with incomplete data)
+
-#  * root privileges (for "iw" and "iwinfo")
+This plugin is suitable for wifi interfaces with a stable selection of peers (e.g. infrastructure).
-#
+It is probably not useful for hotspot-like scenarios.
-# Magic markers
+
-#%# capabilities=autoconf suggest
+Information is parsed from the output of the tool "iwinfo" (OpenWrt) or "iw" (most systems,
-#%# family=auto
+incomplete information).
+
+
+=head1 CONFIGURATION
+
+Symlink this plugin with the name of the wifi interface added (e.g. "wlan0").
+
+Root permissions are probably required for accessing "iw".
+
+  [wireless_signal_noise_*]
+  user root
+
+
+=head1 VERSION
+
+  1.1
+
+
+=head1 AUTHOR
+
+Lars Kruse <devel@sumpfralle.de>
+
+
+=head1 LICENSE
+
+GPLv3 or above
+
+
+=head1 MAGIC MARKERS
+
+  #%# family=auto
+  #%# capabilities=autoconf suggest
+
+=cut
 
 
 set -eu
 
 
+SCRIPT_PREFIX="wireless_signal_noise_"
+
+
 # prefer "iwinfo" for information retrieval, if it is available
 if which iwinfo >/dev/null; then
 	# "iwinfo" has a stable output format but is only available on openwrt
@@ -34,6 +70,12 @@ else
 	# TODO: there seems to be no way to retrieve the noise level via "iw"
 	get_wifi_noise() { echo; }
 fi
+if which arp >/dev/null; then
+	# openwrt does not provide 'arp' by default
+	get_arp() { arp -n; }
+else
+	get_arp() { cat /proc/net/arp; }
+fi
 
 
 clean_fieldname() {
@@ -43,7 +85,7 @@ clean_fieldname() {
 
 get_ip_for_mac() {
 	local ip
-	ip=$(arp -n | grep -iw "$1$" | awk '{print $1}' | sort | head -1)
+	ip=$(get_arp | grep -iw "$1$" | awk '{print $1}' | sort | head -1)
 	[ -n "$ip" ] && echo "$ip" && return 0
 	# no IP found - return MAC instead
 	echo "$1"
@@ -54,55 +96,77 @@ get_wifi_device_from_suffix() {
 	local suffix
 	local real_dev
 	# pick the part after the basename of the real file
-	suffix=$(basename "$0" | sed "s/^$(basename "$(readlink "$0")")//")
+	suffix=$(basename "$0" | sed "s/^$SCRIPT_PREFIX//")
 	for real_dev in $(get_wifi_interfaces); do
 		[ "$suffix" != "$(clean_fieldname "$real_dev")" ] || echo "$real_dev"
 	done | head -1
 }
 
 
+do_config() {
+	local wifi
+	wifi=$(get_wifi_device_from_suffix)
+	[ -z "$wifi" ] && echo >&2 "Missing wifi: $wifi" && return 1
+	echo "graph_title Wireless signal quality - $wifi"
+	echo "graph_args --upper-limit 0"
+	echo "graph_vlabel Signal and noise [dBm]"
+	echo "graph_category network"
+	echo "graph_info This graph shows the signal and noise for all wifi peers"
+	echo "noise.label Noise floor"
+	echo "noise.draw LINE"
+	# sub graphs for all peers
+	get_wifi_peers "$wifi" | while read -r mac signal; do
+		fieldname=$(clean_fieldname "peer_${mac}")
+		peer=$(get_ip_for_mac "$mac")
+		echo "signal_${fieldname}.label $peer"
+		echo "signal_${fieldname}.draw LINE"
+	done
+}
+
+
+do_fetch() {
+	local wifi
+	local peer_data
+	local noise
+	wifi=$(get_wifi_device_from_suffix)
+	[ -z "$wifi" ] && echo >&2 "Missing wifi: $wifi" && return 1
+	peer_data=$(get_wifi_peers "$wifi")
+	echo "$peer_data" | while read -r mac signal; do
+		# ignore empty datasets
+		[ -z "$signal" ] && continue
+		fieldname=$(clean_fieldname "peer_${mac}")
+		echo "signal_${fieldname}.value $signal"
+	done
+	noise=$(get_wifi_noise "$wifi")
+	echo "noise.value ${noise:-U}"
+}
+
+
 ACTION="${1:-}"
 
 case "$ACTION" in
 	config)
-		wifi=$(get_wifi_device_from_suffix)
+		do_config || exit 1
-		echo "graph_title Wireless signal quality - $wifi"
+		[ "${MUNIN_CAP_DIRTYCONFIG:-0}" = 1 ] && do_fetch
-		echo "graph_args --upper-limit 0"
-		echo "graph_vlabel Signal and noise [dBm]"
-		echo "graph_category network"
-		echo "graph_info This graph shows the signal and noise for all wifi peers"
-		echo "noise.label Noise floor"
-		echo "noise.draw LINE"
-		# sub graphs for all peers
-		get_wifi_peers "$wifi" | while read mac signal; do
-			fieldname=$(clean_fieldname "peer_${mac}")
-			peer=$(get_ip_for_mac "$mac")
-			echo "signal_${fieldname}.label $peer"
-			echo "signal_${fieldname}.draw LINE"
-		done
 		;;
 	autoconf)
-		[ -z "$(get_wifi_interfaces)" ] && echo "no (no wifi interfaces found)" && exit 1
+		if [ -z "$(get_wifi_interfaces)" ]; then
-		echo "yes"
+			echo "no (no wifi interfaces found)"
+		else
+			echo "yes"
+		fi
 		;;
 	suggest)
-		get_wifi_interfaces | while read ifname; do
+		get_wifi_interfaces | while read -r ifname; do
 			clean_fieldname "$ifname"
 		done
 		;;
 	"")
-		wifi=$(get_wifi_device_from_suffix)
+		do_fetch
-		peer_data=$(get_wifi_peers "$wifi")
-		echo "$peer_data" | while read mac signal; do
-			# ignore empty datasets
-			[ -z "$signal" ] && continue
-			fieldname=$(clean_fieldname "peer_${mac}")
-			echo "signal_${fieldname}.value $signal"
-		done
-		echo "noise.value $(get_wifi_noise "$wifi")"
 		;;
 	*)
-		echo >&2 "Invalid action (valid: config)"
+		echo >&2 "Invalid action (valid: config / suggest / autoconf / <empty>)"
 		echo >&2
+		exit 2
 		;;
 esac