network: implement a module to get IP addresses and check network connectivity

This module now uses the native node `os.networkInterfaces()` to retrieve the addresses,
instead of the gosuper endpoint.

We also add the very simple "blink" library that is also used by the Supervisor API.

Signed-off-by: Pablo Carranza Velez <pablo@resin.io>

src/lib/blink.coffee

@@ -0,0 +1,2 @@
+constants = require './constants'
+module.exports = require('blinking')(constants.ledFile)

src/network.coffee

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+Promise = require 'bluebird'
+_ = require 'lodash'
+url = require 'url'
+networkCheck = require 'network-checker'
+os = require 'os'
+fs = Promise.promisifyAll(require('fs'))
+
+constants = require './lib/constants'
+{ checkTruthy } = require './lib/validation'
+blink = require './lib/blink'
+
+networkPattern =
+	blinks: 4
+	pause: 1000
+
+pauseConnectivityCheck = false
+enableConnectivityCheck = true
+
+# options: An object of net.connect options, with the addition of:
+#	timeout: 10s
+checkHost = (options) ->
+	if !enableConnectivityCheck or pauseConnectivityCheck
+		return true
+	else
+		return networkCheck.checkHost(options)
+
+# Custom monitor that uses checkHost function above.
+customMonitor = (options, fn) ->
+	networkCheck.monitor(checkHost, options, fn)
+
+# enable: A Boolean to enable/disable the connectivity checks
+exports.enableCheck = enableCheck = (enable) ->
+	enableConnectivityCheck = enable
+
+# Call back for inotify triggered when the VPN status is changed.
+vpnStatusInotifyCallback = ->
+	fs.lstatAsync(constants.vpnStatusPath + '/active')
+	.then ->
+		pauseConnectivityCheck = true
+	.catch ->
+		pauseConnectivityCheck = false
+
+# Use the following to catch EEXIST errors
+EEXIST = (err) -> err.code is 'EEXIST'
+
+exports.startConnectivityCheck = _.once (apiEndpoint, enable) ->
+	exports.enableConnectivityCheck(enable)
+	if !apiEndpoint?
+		console.log('No API endpoint specified, skipping connectivity check')
+		return
+	parsedUrl = url.parse(apiEndpoint)
+	fs.mkdirAsync(constants.vpnStatusPath)
+	.catch EEXIST, (err) ->
+		console.log('VPN status path exists.')
+	.then ->
+		fs.watch(constants.vpnStatusPath, vpnStatusInotifyCallback)
+
+	# Manually trigger the call back to detect cases when VPN was switched on before the supervisor starts.
+	vpnStatusInotifyCallback() if enable
+	customMonitor
+		host: parsedUrl.hostname
+		port: parsedUrl.port ? (if parsedUrl.protocol is 'https:' then 443 else 80)
+		interval: 10 * 1000
+		(connected) ->
+			if connected
+				console.log('Internet Connectivity: OK')
+				blink.pattern.stop()
+			else
+				console.log('Waiting for connectivity...')
+				blink.pattern.start(networkPattern)
+
+# Callback function to enable/disable tcp pings
+exports.enableConnectivityCheck = (val) ->
+	enabled = checkTruthy(val) ? true
+	enableCheck(enabled)
+	console.log("Connectivity check enabled: #{enabled}")
+
+exports.connectivityCheckEnabled = Promise.method ->
+	return enableConnectivityCheck
+
+exports.getIPAddresses = ->
+	_.flatten(_.map(_.omitBy(os.networkInterfaces(), (interfaceFields, interfaceName) ->
+		/(docker[0-9]+)|(rce[0-9]+)|(tun[0-9]+)|(resin-vpn)|(lo)/.test(interfaceName))
+	, (validInterfaces) ->
+		_.map(_.omitBy(validInterfaces, (a) -> a.family != 'IPv4' ), 'address'))
+	)
+
+exports.startIPAddressUpdate = do ->
+	_lastIPValues = null
+	return (callback, interval) ->
+		getAndReportIP = ->
+			ips = exports.getIPAddresses()
+			if !_.isEmpty(_.xor(ips , _lastIPValues))
+				_lastIPValues = ips
+				callback(ips)
+		setInterval( ->
+			getAndReportIP()
+		, interval)
+		getAndReportIP()