wireless_signal_noise_

#!/bin/sh

: << =cut

=head1 NAME

wireless_signal_noise_ - Show signal strength and noise for all connected peers of wifi interface

=head1 APPLICABLE SYSTEMS

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.

Information is parsed from the output of the tool "iwinfo" (OpenWrt) or "iw" (most systems,
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
	get_wifi_interfaces() { iwinfo | grep "^[a-zA-Z]" | awk '{print $1}'; }
	# return MAC of peer and the signal strength
	get_wifi_peers() { iwinfo "$1" assoclist | grep "^[0-9a-fA-F]" | awk '{print $1,$2}'; }
	# the noise should be the same for all peers
	get_wifi_noise() { iwinfo "$1" info | sed -n 's/^.* Noise: \([0-9-]\+\).*/\1/p'; }
else
	# "iw" is available everywhere - but its output format is not recommended for non-humans
	get_wifi_interfaces() { iw dev | awk '{ if ($1 == "Interface") print $2; }'; }
	get_wifi_peers() { iw dev wlan0 station dump \
		| awk '{ if ($1 == "Station") mac=$2; if (($1 == "signal") && ($2 == "avg:")) print mac,$3}'; }
	# 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() {
	echo "$1" | sed 's/^\([^A-Za-z_]\)/_\1/; s/[^A-Za-z0-9_]/_/g'
}


get_ip_for_mac() {
	local ip
	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"
}


get_wifi_device_from_suffix() {
	local suffix
	local real_dev
	# pick the part after the basename of the real file
	suffix=$(basename "$0" | sed "s/^$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 - $wifi"
	echo "graph_args --upper-limit 0"
	echo "graph_vlabel Signal and noise [dBm]"
	echo "graph_category wireless"
	echo "graph_info This graph shows the signal and noise for all wifi peers"
	echo "noise.label Noise floor"
	echo "noise.draw LINE"
	# sub graphs for all peers
	get_wifi_peers "$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 "$ACTION" in
	config)
		do_config || exit 1
		if [ "${MUNIN_CAP_DIRTYCONFIG:-0}" = "1" ]; then do_fetch; fi
		;;
	autoconf)
		if [ -z "$(get_wifi_interfaces)" ]; then
			echo "no (no wifi interfaces found)"
		else
			echo "yes"
		fi
		;;
	suggest)
		get_wifi_interfaces | while read -r ifname; do
			clean_fieldname "$ifname"
		done
		;;
	"")
		do_fetch
		;;
	*)
		echo >&2 "Invalid action (valid: config / suggest / autoconf / <empty>)"
		echo >&2
		exit 2
		;;
esac