148 lines
4.3 KiB
JavaScript
148 lines
4.3 KiB
JavaScript
// mdns-sync.js
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// A single-file mDNS sync tool acting as client or server
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// Uses mdns-server for mDNS and Express for HTTP
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/*********************************
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*
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* 1. LIBRARY FUNCTIONS
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*
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*********************************/
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// 0. HELPER FUNCTIONS
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function convertBufferToString(a) {if (a.data) for (i in a.data) a.data[i] = a.data[i].toString(); return a;}
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// 1. Database functions
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function saveDbToFile(data, filename) {return fs.writeFileSync(filename,typeof data === 'object'?JSON.stringify(data):data);}
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function loadDbFromFile(filename) {if (!fs.existsSync(filename)) return {local:{},remote:{}}; else return JSON.parse(fs.readFileSync(filename));}
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// 2. Network functions
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function getLocalNetworkAddressesIPs() {
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const os = require('os');
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const interfaces = os.networkInterfaces();
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const addresses = [];
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for (const name of Object.keys(interfaces)) {
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for (const iface of interfaces[name]) {
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if (iface.family === 'IPv4' && !iface.internal) {
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addresses.push(iface.address);
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}
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}
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}
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return addresses;
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}
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function sniffmDNSLocalPackets() {
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// 1. Listen for responses
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mdns.on('response', function(response) {
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// console.log("got a new mDNS response.",response);
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for (k in response.answers) {
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let answer = response.answers[k];
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// 1. Handle DEVICES for a given SERVICE
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if (answer.type == "PTR") {
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// 1.1 Filter by RELEVANT SERVICE TYPES
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if (!["in-addr.arpa","_googlecast._tcp.local","_tcp.local"].some(suffix => answer.name.endsWith(suffix))) return;
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// 1.2 Initialize POINTERS (services) sub-database
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if (!db.local.PTR) db.local.PTR = {};
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// 1.3 Initialize this SERVICE TYPE (e.g. _googlecast._tcp.local), if needed
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if (!db.local.PTR[answer.name]) {
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db.local.PTR[answer.name] = [answer.data];
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} else {
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// Add a new DEVICE to this SERVICE TYPE if needed
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if (!db.local.PTR[answer.name].includes(answer.data))
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db.local.PTR[answer.name].push(answer.data);
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}
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}
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// 2. Handle DEVICE IP resolution
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if (answer.type == "A") {
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// 2.1 Initialize ADDRESSES sub-database
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if (!db.local.A) db.local.A = {};
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db.local.A[answer.name] = answer.data;
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}
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if (["TXT","SRV"].includes(answer.type)) {
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// Initialize this device / entry, if needed
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if (db.local[answer.name] === undefined) db.local[answer.name] = {"TXT":null,"SRV":null};
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db.local[answer.name][answer.type] = answer.data;
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}
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saveDbToFile(db,DB_FILENAME);
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}
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})
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// 2. Listen for queries
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mdns.on('query', function(query) {/* console.log("query requested",query);*/});
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// 3. Handle the server being destroyed
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mdns.on('destroyed', function () {console.log('Server destroyed.');process.exit(0);});
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// 4. Handle the onReady event
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mdns.on('ready', function () {
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console.log("mDNS server is ready...");
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// mdns.query({questions:[{ name: '_:googlecast._tcp.local', type: 'PTR', class: 'IN'}]} );
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})
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// initialize the server now that we are watching for events
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mdns.initServer()
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}
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function injectmDNSPacketLocally(type,name,data,flush = true,_class = 'IN',ttl = 120) {
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console.log(`sending packet ${name} of ${type} with data: ${data}`);
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mdns.respond({answers:[
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{
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name: name,
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type: type,
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ttl: ttl,
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class: _class,
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flush: flush,
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data: data
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}
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]});}
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/*********************************
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*
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* 100. MAIN / IMPERATIVE CODE
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*
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*********************************/
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const fs = require("fs");
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const DB_FILENAME = 'database.json';
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const db = loadDbFromFile(DB_FILENAME);
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const LOCAL_IP_ADDR = getLocalNetworkAddressesIPs()[0];
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const mdns = require('mdns-server')({interface: LOCAL_IP_ADDR,reuseAddr: true,loopback: false,noInit: true});
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sniffmDNSLocalPackets();
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setInterval(function(){
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// INJECT PTR - Pointers services
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for (name in db.remote.PTR) {
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for (i in db.remote.PTR[name])
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injectmDNSPacketLocally('PTR',name,db.remote.PTR[name][i]);
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}
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// INJECT A - Addresses
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for (name in db.remote.A) {
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injectmDNSPacketLocally('A',name,db.remote.A[name]);
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}
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// INJECT SRV,TXT
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for (name in db.remote) {
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if (["PTR","A"].includes(name)) continue;
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if (db.remote[name].SRV !== null)
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injectmDNSPacketLocally('SRV',name,db.remote[name].SRV);
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if (db.remote[name].TXT !== null)
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injectmDNSPacketLocally('TXT',name,Buffer.from(db.remote[name].TXT, 'utf8'));
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}
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},5000); |