prometheus-node-exporter-lua: rewrite wifi scraper

On my bullet m2, scrape duration goes from between 0.2 and 0.5 to a stable 0.025
We also don't depend on luci anymore

This remove wifi_network_up metric, but this metric was buggy
wifi_network_up{ifname="wlan0-1",ssid="test1",channel="11",mode="Master",bssid="12:34:56:78:9A:BC",country="FR",frequency="2.462"} 1
wifi_network_up{ifname="radio0.network2",ssid="test1",channel="11",mode="Master",country="US",frequency="2.462"} 0

Signed-off-by: Etienne Champetier <champetier.etienne@gmail.com>

utils/prometheus-node-exporter-lua/Makefile

@@ -16,7 +16,7 @@ define Package/prometheus-node-exporter-lua
   SECTION:=utils
   CATEGORY:=Utilities
   TITLE:=Provides system statistics as Prometheus scraping endpoint
-  DEPENDS:=+luasocket
+  DEPENDS:=+luasocket +libiwinfo-lua +libubus-lua +lua
   URL:=https://github.com/rbo/openwrt_exporter
   PKGARCH:=all
 endef

utils/prometheus-node-exporter-lua/files/usr/bin/prometheus-node-exporter-lua

@@ -69,11 +69,10 @@ function metric(name, mtype, labels, value)
   return outputter
 end
 
-function scraper_wifi()
-  local rv = { }
-  local ntm = require "luci.model.network".init()
+local ubus = require "ubus"
+local iwinfo = require "iwinfo"
 
-  local metric_wifi_network_up = metric("wifi_network_up","gauge")
+function scraper_wifi()
   local metric_wifi_network_quality = metric("wifi_network_quality","gauge")
   local metric_wifi_network_bitrate = metric("wifi_network_bitrate","gauge")
   local metric_wifi_network_noise = metric("wifi_network_noise","gauge")
@@ -83,53 +82,47 @@ function scraper_wifi()
   local metric_wifi_station_tx_packets = metric("wifi_station_tx_packets","gauge")
   local metric_wifi_station_rx_packets = metric("wifi_station_rx_packets","gauge")
 
-  local dev
-  for _, dev in ipairs(ntm:get_wifidevs()) do
-    local rd = {
-      up       = dev:is_up(),
-      device   = dev:name(),
-      name     = dev:get_i18n(),
-      networks = { }
-    }
+  local u = ubus.connect()
+  local status = u:call("network.wireless", "status", {})
 
-    local net
-    for _, net in ipairs(dev:get_wifinets()) do
+  for dev, dev_table in pairs(status) do
+    for _, intf in ipairs(dev_table['interfaces']) do
+      local ifname = intf['ifname']
+      local iw = iwinfo[iwinfo.type(ifname)]
       local labels = {
-        channel = net:channel(),
-        ssid = net:active_ssid(),
-        bssid = net:active_bssid(),
-        mode = net:active_mode(),
-        ifname = net:ifname(),
-        country = net:country(),
-        frequency = net:frequency(),
+        channel = iw.channel(ifname),
+        ssid = iw.ssid(ifname),
+        bssid = iw.bssid(ifname),
+        mode = iw.mode(ifname),
+        ifname = ifname,
+        country = iw.country(ifname),
+        frequency = iw.frequency(ifname),
+        device = dev,
       }
-      if net:is_up() then
-        metric_wifi_network_up(labels, 1)
-        local signal = net:signal_percent()
-        if signal ~= 0 then
-          metric_wifi_network_quality(labels, net:signal_percent())
-        end
-	metric_wifi_network_noise(labels, net:noise())
-	local bitrate = net:bitrate()
-	if bitrate then
-          metric_wifi_network_bitrate(labels, bitrate)
-	end
 
-        local assoclist = net:assoclist()
-        for mac, station in pairs(assoclist) do
-          local labels = {
-            ifname = net:ifname(),
-            mac = mac,
-          }
-          metric_wifi_station_signal(labels, station.signal)
-          metric_wifi_station_tx_packets(labels, station.tx_packets)
-          metric_wifi_station_rx_packets(labels, station.rx_packets)
-        end
-      else
-        metric_wifi_network_up(labels, 0)
+      local qc = iw.quality(ifname) or 0
+      local qm = iw.quality_max(ifname) or 0
+      local quality = 0
+      if qc > 0 and qm > 0 then
+        quality = math.floor((100 / qm) * qc)
+      end
+
+      metric_wifi_network_quality(labels, quality)
+      metric_wifi_network_noise(labels, iw.noise(ifname) or 0)
+      metric_wifi_network_bitrate(labels, iw.bitrate(ifname) or 0)
+      metric_wifi_network_signal(labels, iw.signal(ifname) or -255)
+
+      local assoclist = iw.assoclist(ifname)
+      for mac, station in pairs(assoclist) do
+        local labels = {
+          ifname = ifname,
+          mac = mac,
+        }
+        metric_wifi_station_signal(labels, station.signal)
+        metric_wifi_station_tx_packets(labels, station.tx_packets)
+        metric_wifi_station_rx_packets(labels, station.rx_packets)
       end
     end
-    rv[#rv+1] = rd
   end
 end