add vanilla wifi.lua

from `prometheus-node-exporter-lua-wifi` package

files/wifi.lua

@@ -0,0 +1,45 @@
+local ubus = require "ubus"
+local iwinfo = require "iwinfo"
+
+local function scrape()
+  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_dbm","gauge")
+  local metric_wifi_network_signal = metric("wifi_network_signal_dbm","gauge")
+
+  local u = ubus.connect()
+  local status = u:call("network.wireless", "status", {})
+
+  for dev, dev_table in pairs(status) do
+    for _, intf in ipairs(dev_table['interfaces']) do
+      local ifname = intf['ifname']
+      if ifname ~= nil then
+        local iw = iwinfo[iwinfo.type(ifname)]
+        local labels = {
+          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,
+        }
+
+        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)
+      end
+    end
+  end
+end
+
+return { scrape = scrape }