index.js 4.73 KB
Newer Older
liang ce committed
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180
var packet = require('dns-packet')
var dgram = require('dgram')
var thunky = require('thunky')
var events = require('events')
var os = require('os')

var noop = function () {}

module.exports = function (opts) {
  if (!opts) opts = {}

  var that = new events.EventEmitter()
  var port = typeof opts.port === 'number' ? opts.port : 5353
  var type = opts.type || 'udp4'
  var ip = opts.ip || opts.host || (type === 'udp4' ? '224.0.0.251' : null)
  var me = {address: ip, port: port}
  var memberships = {}
  var destroyed = false
  var interval = null

  if (type === 'udp6' && (!ip || !opts.interface)) {
    throw new Error('For IPv6 multicast you must specify `ip` and `interface`')
  }

  var socket = opts.socket || dgram.createSocket({
    type: type,
    reuseAddr: opts.reuseAddr !== false,
    toString: function () {
      return type
    }
  })

  socket.on('error', function (err) {
    if (err.code === 'EACCES' || err.code === 'EADDRINUSE') that.emit('error', err)
    else that.emit('warning', err)
  })

  socket.on('message', function (message, rinfo) {
    try {
      message = packet.decode(message)
    } catch (err) {
      that.emit('warning', err)
      return
    }

    that.emit('packet', message, rinfo)

    if (message.type === 'query') that.emit('query', message, rinfo)
    if (message.type === 'response') that.emit('response', message, rinfo)
  })

  socket.on('listening', function () {
    if (!port) port = me.port = socket.address().port
    if (opts.multicast !== false) {
      that.update()
      interval = setInterval(that.update, 5000)
      socket.setMulticastTTL(opts.ttl || 255)
      socket.setMulticastLoopback(opts.loopback !== false)
    }
  })

  var bind = thunky(function (cb) {
    if (!port) return cb(null)
    socket.once('error', cb)
    socket.bind(port, opts.interface, function () {
      socket.removeListener('error', cb)
      cb(null)
    })
  })

  bind(function (err) {
    if (err) return that.emit('error', err)
    that.emit('ready')
  })

  that.send = function (value, rinfo, cb) {
    if (typeof rinfo === 'function') return that.send(value, null, rinfo)
    if (!cb) cb = noop
    if (!rinfo) rinfo = me

    bind(onbind)

    function onbind (err) {
      if (destroyed) return cb()
      if (err) return cb(err)
      var message = packet.encode(value)
      socket.send(message, 0, message.length, rinfo.port, rinfo.address || rinfo.host, cb)
    }
  }

  that.response =
  that.respond = function (res, rinfo, cb) {
    if (Array.isArray(res)) res = {answers: res}

    res.type = 'response'
    res.flags = (res.flags || 0) | packet.AUTHORITATIVE_ANSWER
    that.send(res, rinfo, cb)
  }

  that.query = function (q, type, rinfo, cb) {
    if (typeof type === 'function') return that.query(q, null, null, type)
    if (typeof type === 'object' && type && type.port) return that.query(q, null, type, rinfo)
    if (typeof rinfo === 'function') return that.query(q, type, null, rinfo)
    if (!cb) cb = noop

    if (typeof q === 'string') q = [{name: q, type: type || 'ANY'}]
    if (Array.isArray(q)) q = {type: 'query', questions: q}

    q.type = 'query'
    that.send(q, rinfo, cb)
  }

  that.destroy = function (cb) {
    if (!cb) cb = noop
    if (destroyed) return process.nextTick(cb)
    destroyed = true
    clearInterval(interval)
    socket.once('close', cb)
    socket.close()
  }

  that.update = function () {
    var ifaces = opts.interface ? [].concat(opts.interface) : allInterfaces()
    var updated = false

    for (var i = 0; i < ifaces.length; i++) {
      var addr = ifaces[i]

      if (memberships[addr]) continue
      memberships[addr] = true
      updated = true

      try {
        socket.addMembership(ip, addr)
      } catch (err) {
        that.emit('warning', err)
      }
    }

    if (!updated || !socket.setMulticastInterface) return
    socket.setMulticastInterface(opts.interface || defaultInterface())
  }

  return that
}

function defaultInterface () {
  var networks = os.networkInterfaces()
  var names = Object.keys(networks)

  for (var i = 0; i < names.length; i++) {
    var net = networks[names[i]]
    for (var j = 0; j < net.length; j++) {
      var iface = net[j]
      if (iface.family === 'IPv4' && !iface.internal) return iface.address
    }
  }

  return '127.0.0.1'
}

function allInterfaces () {
  var networks = os.networkInterfaces()
  var names = Object.keys(networks)
  var res = []

  for (var i = 0; i < names.length; i++) {
    var net = networks[names[i]]
    for (var j = 0; j < net.length; j++) {
      var iface = net[j]
      if (iface.family === 'IPv4') {
        res.push(iface.address)
        // could only addMembership once per interface (https://nodejs.org/api/dgram.html#dgram_socket_addmembership_multicastaddress_multicastinterface)
        break
      }
    }
  }

  return res
}