mDNSGw Sources: src/app.js@42e83b3431d9 (annotated)

src/app.js@42e83b3431d9 (annotated)

src/app.js

Wed, 13 Aug 2014 21:00:15 +0200

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 13 Aug 2014 21:00:15 +0200
changeset 3: 42e83b3431d9
parent 0: eb6d4ce6fd78
permissions: -rwxr-xr-x

Include signal handler and complete most of service daemon logic.

 #! /usr/bin/env nodejs
 //
 //  mDNSGw - Zero Configuration DNS Gateway for Mesh Networks
 //  Copyright © 2014 Michael Schloh von Bennewitz <michael@schloh.com>
 //
 //  Permission to use, copy, modify, and/or distribute this software for
 //  any purpose with or without fee is hereby granted, provided that the
 //  above copyright notice and this permission notice appear in all copies.
 //
 //  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
 //  WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
 //  WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
 //  AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
 //  DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
 //  PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS
 //  ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
 //  THIS SOFTWARE.
 //
 //  This file is part of mDNSGw, a Zero configuration DNS gateway
 //  which can be found at http://dev.europalab.com/mdnsgw/
 //
 //  app.js: ECMA JavaScript implementation
 //
 /***********************************************************
 |                  ____  _   _ ____   ____                 |
 |        _ __ ___ |  _ \| \ | / ___| / ___|_      __       |
 |       | '_ ` _ \| | | |  \| \___ \| |  _\ \ /\ / /       |
 |       | | | | | | |_| | |\  |___) | |_| |\ V  V /        |
 |       |_| |_| |_|____/|_| \_|____/ \____| \_/\_/         |
 |                                                          |
 | Requirements: Redis server with standard configuration   |
 |               NodeJS and NPM modules (see package.json)  |
 |                                                          |
 | Execute: To start this application, launch it with the   |
 |          script named fork.js: $ ./fork.js               |
 |                                                          |
 | Support: http://list.europalab.com/mailman/mdnsgs/       |
 |                                                          |
 ***********************************************************/
 // import module dependencies
 var mdnsinst = require('mdns');
 var redisdat = require('redis');
 var nameinst = require('native-dns');
 // install POSIX signal handlers
 process.on('SIGUSR2', function() {
   console.log('SIGUSR2: Dumping mDNSGw entries at', Date());
   rediscli.hgetall('hostnames', function (error, object) {console.dir(object);});
 });
 process.on('SIGHUP', function() {
   console.log('SIGHUP: Cleared all database entries at', Date());
   cleardb();
 });
 // instantiate a new redis client
 // http://www.rediscookbook.org/
 var rediscli = redisdat.createClient();
 rediscli.on('error', function (error) {
   console.log('Error ' + error);
 });
 // clear mDNS service keys
 function cleardb () {
   rediscli.del('hostnames');
   // this is not working unfortunately for the loop
   rediscli.keys('*', function (error, replies) {
     replies.forEach(function (reply, ident) {
       rediscli.del(reply, function (error, value) {
         if (error) throw(error);
       });
     });
   });
 }
 // scan all advertised mDNS service types
 cleardb(); // clear old data first
 var browsall = mdnsinst.browseThemAll();
 browsall.on('serviceUp', function(service) {
     // iterate through hosts and watch accordingly
     if (service.type.name.match(/^[a-zA-Z0-9\-]+$/)) { // mdns module hack
       if (service.type.protocol == 'tcp') {
         var browserv = mdnsinst.createBrowser(mdnsinst.tcp(service.type.name));
       }
       else if (service.type.protocol == 'udp') {
         var browserv = mdnsinst.createBrowser(mdnsinst.udp(service.type.name));
       }
       else if (service.type.protocol == 'sctp') {
         var browserv = mdnsinst.createBrowser(mdnsinst.sctp(service.type.name));
       }
       else throw(error);
       // common logic for all transports (TCP, UDP, SCTP, etcetera)
       browserv.on('serviceUp', function(service) {
         //console.log('service up: ', service);
         //{interfaceIndex: 2, type: {name: 'ssh', protocol: 'tcp', subtypes: [], fullyQualified: true}, replyDomain: 'local.', flags: 2, name: 'hostname-mich', networkInterface: 'eth0', fullname: 'hostname-mich._ssh._tcp.local.', host: 'hostname-mich.local.', port: 22, addresses: ['192.168.1.50']}
         // insert one or more IP addresses for each hostname.local.
         rediscli.hset('hostnames', service.host.replace(/\.$/, ''), service.addresses);
       });
       browserv.on('serviceDown', function(service) {
         console.log('service down: ', service);
         //FIXME: still need to selectively remove hosts
       });
       browserv.on('serviceChanged', function(service) {
         console.log('service changed: ', service);
         //FIXME: still need to selectively update hosts
       });
       browserv.start();
     }
 });
 browsall.start();
 // instantiate a new DNS server
 var nameserv = nameinst.createServer();
 nameserv.on('request', function (request, response) {
   //console.log(request)
   // ensure that requested hostname is present
   rediscli.hget('hostnames', request.question[0].name, function (error, value) {
     // handle unexpected errors
     if (error) throw(error);
     if (value) { // the db succeeded in finding a match
       // populate the DNS response with the chosen hostname
       rediscli.hkeys('hostnames', function (error, replies) {
           replies.forEach(function (host, index) {
             if (request.question[0].name == host) {
               rediscli.hget('hostnames', host, function (error, value) {
                 // handle unexpected errors
                 if (error) throw(error);
                 // FIXME: still must handle multihomed hosts
                 //// a host might have more than one address
                 //value.forEach(function (addr, iter)
                 // set the nameserver address
                 response.answer.push(nameinst.A({
                   name: host,
                   address: value,
                   ttl: 600,
                 }));
                 response.send();
               });
             }
           });
       });
     }
     else {
       response.answer.push(nameinst.A({
       name: request.question[0].name,
       address: '127.0.0.1',
       ttl: 600,
       }));
       response.send();
     }
   });
 });
 // DNS error handler logic
 nameserv.on('error', function (err, buff, req, res) {
   console.log('DNS problem: ', err.stack);
 });
 //// debug process user
 //console.log('Start.');
 //console.log(process.env.USER);
 //console.log(process.env.SUDO_USER);
 //console.log('Done.');
 //
 // <1024 must run privileged
 var nudpport = 53; // default DNS
 if (nudpport < 1024 && process.getuid() !== 0) {
   //console.log('Serving on port <1024 from an unprivileged user.\nChange to root if using a privileged port number.')
   throw new Error('Serving on port <1024 from an unprivileged user.')
 }
 // start the DNS process
 nameserv.serve(nudpport, function () {
   try {
     console.log('Starting mDNSGw on', Date());
     process.stdout.write('Old UID: ' + process.getuid() + ', Old GID: ' + process.getgid() + '... ');
     process.umask('0644');
     process.setgid('daemon');
     if (process.env.SUDO_USER)
       process.setuid(process.env.SUDO_USER);
     else
       process.setuid('daemon');
     console.log('New UID: ' + process.getuid() + ', New GID: ' + process.getgid());
   } catch (err) {
     console.log('Cowardly refusing to keep the process alive as root.');
     process.exit(1);
   }
 });
 //// debug print all key and value database entries
 //rediscli.hgetall('hostnames', function (error, object) {console.dir(object);});
 //// display stored mDNS service data entries
 //rediscli.hkeys('hostnames', function (error, replies) {
 //  console.log(replies.length + ' replies:');
 //  replies.forEach(function (reply, ident) {
 //    console.log('    ' + ident + ': ' + reply);
 //  });
 //});
 //// block executes on program termination
 //rediscli.quit();  // cleanup db connection
 //browserv.stop();  // zombie scope too bad
 //browsall.stop();