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cel committed Disable pointer compression which was failingLatest: 012e32d on 7/19/2017, 3:48:58 AM
📄.gitignore
📄LICENSE
📄README.md
📁_test_data
📄constants.js
📄convenient.js
📄encode.js
📄message.js
📄named.js
📄package.json
📄parse.js
📄server.js
📁test
📁util
README.md

dnsd: DNS encoder, decoder, and server

dnsd is a Node.js package for working with DNS. It converts binary DNS messages to and from convenient JavaScript objects; and it provides a server API, for running a custom name server.

dnsd is available as an npm module.

$ npm install dnsd

Example: Running a server

This simple DNS server responds with an "A" (address) record of 1.2.3.4 for every request.

var dnsd = require('dnsd')
dnsd.createServer(function(req, res) {
  res.end('1.2.3.4')
}).listen(5353, '127.0.0.1')
console.log('Server running at 127.0.0.1:5353')

Now test your server:

$ dig @localhost -p 5353 foo.example A

; <<>> DiG 9.8.1-P1 <<>> @localhost -p 5353 foo.example A
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 27955
;; flags: qr rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
;; WARNING: recursion requested but not available

;; QUESTION SECTION:
;foo.example.            IN    A

;; ANSWER SECTION:
foo.example.        3600    IN    A    1.2.3.4

;; Query time: 1 msec
;; SERVER: 127.0.0.1#5353(127.0.0.1)
;; WHEN: Wed Aug  8 05:10:40 2012
;; MSG SIZE  rcvd: 45

This example logs all requests. For address (A) queries, it returns two records, with a random TTL, and the final octet of the IP address is the length of the hostname queried.

var dnsd = require('dnsd')

var server = dnsd.createServer(handler)
server.zone('example.com', 'ns1.example.com', 'us@example.com', 'now', '2h', '30m', '2w', '10m')
      .listen(5353, '127.0.0.1')
console.log('Server running at 127.0.0.1:5353')

function handler(req, res) {
  console.log('%s:%s/%s %j', req.connection.remoteAddress, req.connection.remotePort, req.connection.type, req)

  var question = req.question[0]
    , hostname = question.name
    , length = hostname.length
    , ttl = Math.floor(Math.random() * 3600)

  if(question.type == 'A') {
    res.answer.push({name:hostname, type:'A', data:"1.1.1."+length, 'ttl':ttl})
    res.answer.push({name:hostname, type:'A', data:"2.2.2."+length, 'ttl':ttl})
  }
  res.end()
}

Test the SOA response:

$ dig @localhost -p 5353 example.com soa

; <<>> DiG 9.8.1-P1 <<>> @localhost -p 5353 example.com soa
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 30176
;; flags: qr aa rd; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0
;; WARNING: recursion requested but not available

;; QUESTION SECTION:
;example.com.            IN    SOA

;; ANSWER SECTION:
example.com.        600    IN    SOA    ns1.example.com. us.example.com. 1344403648 7200 1800 1209600 600

;; Query time: 5 msec
;; SERVER: 127.0.0.1#5353(127.0.0.1)
;; WHEN: Wed Aug  8 05:27:32 2012
;; MSG SIZE  rcvd: 72

And test the address (A) response:

$ dig @localhost -p 5353 example.com a

; <<>> DiG 9.8.1-P1 <<>> @localhost -p 5353 example.com a
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 19419
;; flags: qr aa rd; QUERY: 1, ANSWER: 2, AUTHORITY: 0, ADDITIONAL: 0
;; WARNING: recursion requested but not available

;; QUESTION SECTION:
;example.com.            IN    A

;; ANSWER SECTION:
example.com.        1222    IN    A    1.1.1.11
example.com.        1222    IN    A    2.2.2.11

;; Query time: 1 msec
;; SERVER: 127.0.0.1#5353(127.0.0.1)
;; WHEN: Wed Aug  8 05:27:34 2012
;; MSG SIZE  rcvd: 61

Server output for these queries:

Server running at 127.0.0.1:5353
127.0.0.1:34427/udp4 {"id":30176,"type":"request","responseCode":0,"opcode":"query","authoritative":false,"truncated":false,"recursion_desired":true,"recursion_available":false,"authenticated":false,"checking_disabled":false,"question":[{"name":"example.com","type":"SOA","class":"IN"}]}
127.0.0.1:59596/udp4 {"id":19419,"type":"request","responseCode":0,"opcode":"query","authoritative":false,"truncated":false,"recursion_desired":true,"recursion_available":false,"authenticated":false,"checking_disabled":false,"question":[{"name":"example.com","type":"A","class":"IN"}]}

Example: MX Records

This is an example if you need to route your mail server with an MX record.

// Example MX response with dnsd
//
// To test:
// 1. Run this program
// 2. dig @localhost -p 5353 example.com mx

var dnsd = require('dnsd')

var server = dnsd.createServer(handler)
server.zone('example.com', 'ns1.example.com', 'us@example.com', 'now', '2h', '30m', '2w', '10m')
server.listen(5353, '127.0.0.1')
console.log('Listening at 127.0.0.1:5353')

function handler(req, res) {
  var question = res.question && res.question[0]

  if(question.type != 'MX')
    return res.end()

  console.log('MX lookup for domain: %s', question.name)
  res.answer.push({'name':question.name, 'type':'MX', 'data':[10, 'mail.example.com']})
  res.answer.push({'name':question.name, 'type':'MX', 'data':[20, 'mail.backupexample.com']})

  return res.end()
}

The MX data attribute needs to be an Array to work properly, the first value is the priority, the second is the server. This server name must be a domain string and not an IP address. Make sure you have an A record or CNAME setup for this.

See http://support.google.com/a/bin/answer.py?hl=en&answer=140034 for more info on MX records and configuration.

Example: Parse a message

var fs = require('fs')
var dnsd = require('dnsd')

var msg_file = require.resolve('dnsd/_test_data/registry.npmjs.org-response')
  , msg_data = fs.readFileSync(msg_file)
  , message = dnsd.parse(msg_data)

console.dir(message)

Output

{ id: 34233,
  type: 'response',
  responseCode: 0,
  opcode: 'query',
  authoritative: false,
  truncated: false,
  recursion_desired: true,
  recursion_available: true,
  authenticated: false,
  checking_disabled: false,
  question: [ { name: 'registry.npmjs.org', type: 'A', class: 'IN' } ],
  answer:
   [ { name: 'registry.npmjs.org',
       type: 'CNAME',
       class: 'IN',
       ttl: 85,
       data: 'isaacs.iriscouch.net' },
     { name: 'isaacs.iriscouch.net',
       type: 'CNAME',
       class: 'IN',
       ttl: 2821,
       data: 'ec2-23-23-147-24.compute-1.amazonaws.com' },
     { name: 'ec2-23-23-147-24.compute-1.amazonaws.com',
       type: 'A',
       class: 'IN',
       ttl: 356336,
       data: '23.23.147.24' } ] }

Example: Encode a message

var dnsd = require('dnsd')

var questions = [ {name:'example.com', class:'IN', type:'TXT'} ]
  , message = {type:'query', id:123, opcode:'query', recursion_desired:true, question:questions}
  , msg_data = dnsd.binify(message)

console.log('Encoded = %j', Array.prototype.slice.apply(msg_data))

message = dnsd.parse(msg_data)

console.log('Round trip:')
console.dir(message)

Output:

Encoded = [0,123,1,0,0,1,0,0,0,0,0,0,7,101,120,97,109,112,108,101,3,99,111,109,0,0,16,0,1]
Round trip:
{ id: 123,
  type: 'request',
  responseCode: 0,
  opcode: 'query',
  authoritative: false,
  truncated: false,
  recursion_desired: true,
  recursion_available: false,
  authenticated: false,
  checking_disabled: false,
  question: [ { name: 'example.com', type: 'TXT', class: 'IN' } ] }

Defaults

dnsd is defaultable. The option convenient (true by default) adds convenience code when running a server. Convenience mode adds several features, mostly to build standards-compliant name servers.

var dnsd_easy = require('dnsd')
var dnsd_hard = dnsd_easy.defaults({convenient: false})

First, your handler's response object already has .type = "response" set; then there are many helpers processing your response:

Without convenience mode, dnsd will simply send your response verbatim, as you define it (or throw an encoding error for missing or bad data).

Tests

Follow uses node-tap. If you clone this Git repository, tap is included.

$ tap test
ok test/api.js ........................................ 10/10
ok test/convenience.js ................................ 22/22
ok test/message.js .................................. 176/176
ok test/print.js ...................................... 10/10
ok test/server.js ..................................... 35/35
total ............................................... 253/253

ok

License

Apache 2.0

See the Apache 2.0 license.

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