goldilocks.js/lib/mdns.js

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'use strict';
var PromiseA = require('bluebird');
var queryName = '_cloud._tcp.local';
var dnsSuite = require('dns-suite');
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function createResponse(name, ownerIds, packet, ttl, mainPort) {
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var rpacket = {
header: {
id: packet.header.id
, qr: 1
, opcode: 0
, aa: 1
, tc: 0
, rd: 0
, ra: 0
, res1: 0
, res2: 0
, res3: 0
, rcode: 0
, }
, question: packet.question
, answer: []
, authority: []
, additional: []
, edns_options: []
};
rpacket.answer.push({
name: queryName
, typeName: 'PTR'
, ttl: ttl
, className: 'IN'
, data: name + '.' + queryName
});
var ifaces = require('./local-ip').find();
Object.keys(ifaces).forEach(function (iname) {
var iface = ifaces[iname];
iface.ipv4.forEach(function (addr) {
rpacket.additional.push({
name: name + '.local'
, typeName: 'A'
, ttl: ttl
, className: 'IN'
, address: addr.address
});
});
iface.ipv6.forEach(function (addr) {
rpacket.additional.push({
name: name + '.local'
, typeName: 'AAAA'
, ttl: ttl
, className: 'IN'
, address: addr.address
});
});
});
rpacket.additional.push({
name: name + '.' + queryName
, typeName: 'SRV'
, ttl: ttl
, className: 'IN'
, priority: 1
, weight: 0
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, port: mainPort
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, target: name + ".local"
});
rpacket.additional.push({
name: name + '._device-info.' + queryName
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, typeName: 'TXT'
, ttl: ttl
, className: 'IN'
, data: ["model=CloudHome1,1", "dappsvers=1"]
});
ownerIds.forEach(function (id) {
rpacket.additional.push({
name: name + '._owner-id.' + queryName
, typeName: 'TXT'
, ttl: ttl
, className: 'IN'
, data: [id]
});
});
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return dnsSuite.DNSPacket.write(rpacket);
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}
module.exports.create = function (deps, config) {
var socket;
var nextBroadcast = -1;
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function handlePacket(message, rinfo) {
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// console.log('Received %d bytes from %s:%d', message.length, rinfo.address, rinfo.port);
var packet;
try {
packet = dnsSuite.DNSPacket.parse(message);
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}
catch (er) {
// `dns-suite` actually errors on a lot of the packets floating around in our network,
// so don't bother logging any errors. (We still use `dns-suite` because unlike `dns-js`
// it can successfully craft the one packet we want to send.)
return;
}
// Only respond to queries.
if (packet.header.qr !== 0) { return; }
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// Only respond if they were asking for cloud devices.
if (packet.question.length !== 1) { return; }
if (packet.question[0].name !== queryName) { return; }
if (packet.question[0].typeName !== 'PTR') { return; }
if (packet.question[0].className !== 'IN' ) { return; }
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var proms = [
deps.storage.mdnsId.get()
, deps.storage.owners.all().then(function (owners) {
// The ID is the sha256 hash of the PPID, which shouldn't be reversible and therefore
// should be safe to expose without needing authentication.
return owners.map(function (owner) {
return owner.id;
});
})
];
PromiseA.all(proms).then(function (results) {
var resp = createResponse(results[0], results[1], packet, config.mdns.ttl, deps.tcp.mainPort);
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var now = Date.now();
if (now > nextBroadcast) {
socket.send(resp, config.mdns.port, config.mdns.broadcast);
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nextBroadcast = now + config.mdns.ttl * 1000;
} else {
socket.send(resp, rinfo.port, rinfo.address);
}
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});
}
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function start() {
socket = require('dgram').createSocket({ type: 'udp4', reuseAddr: true });
socket.on('message', handlePacket);
return new Promise(function (resolve, reject) {
socket.once('error', reject);
socket.bind(config.mdns.port, function () {
var addr = this.address();
console.log('bound on UDP %s:%d for mDNS', addr.address, addr.port);
socket.setBroadcast(true);
socket.addMembership(config.mdns.broadcast);
// This is supposed to be a local device discovery mechanism, so we shouldn't
// need to hop through any gateways. This helps with security by making it
// much more difficult for someone to use us as part of a DDoS attack by
// spoofing the UDP address a request came from.
socket.setTTL(1);
socket.removeListener('error', reject);
resolve();
});
});
}
function stop() {
return new Promise(function (resolve, reject) {
socket.once('error', reject);
socket.close(function () {
socket.removeListener('error', reject);
socket = null;
resolve();
});
});
}
function updateConf() {
var promise;
if (config.mdns.disabled) {
if (socket) {
promise = stop();
}
} else {
if (!socket) {
promise = start();
} else if (socket.address().port !== config.mdns.port) {
promise = stop().then(start);
} else {
// Can't check membership, so just add the current broadcast address to make sure
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// it's set. If it's already set it will throw an exception (at least on linux).
try {
socket.addMembership(config.mdns.broadcast);
} catch (e) {}
promise = Promise.resolve();
}
}
}
updateConf();
return {
updateConf
};
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};