gotomypc/node-dns

Replacement dns module in pure javascript for node.js

native-dns -- A replacement DNS stack for node.js

Installation

npm install native-dns and then var dns = require('native-dns');

Client

native-dns exports what should be a 1:1 mapping of the upstream node.js dns module. That is to say if it's listed in the docs it should behave similarly. If it doesn't please file an issue

Request

Beyond matching the upstream module, native-dns also provides a method for customizing queries.

var dns = require('../dns'),
  util = require('util');

var question = dns.Question({
  name: 'www.google.com',
  type: 'A',
});

var start = new Date().getTime();

var req = dns.Request({
  question: question,
  server: { address: '8.8.8.8', port: 53, type: 'udp' },
  timeout: 1000,
});

req.on('timeout', function () {
  console.log('Timeout in making request');
});

req.on('message', function (err, answer) {
  answer.answer.forEach(function (a) {
    console.log(a.address);
  });
});

req.on('end', function () {
  var delta = (new Date().getTime()) - start;
  console.log('Finished processing request: ' + delta.toString() + 'ms');
});

req.send();

Request creation takes an object with the following fields

• question -- an instance of Question (required)
• server -- defines the remote end point (required)

• as an object it should be
  • address -- a string ip address (required)
  • port -- a number for the remote port (optional, default 53)
  • type -- a string indicating udp or tcp (optional, default udp) You do not need to indicate ipv4 or ipv6, the backend will handle that
• a string ip address

• timeout -- a number in milliseconds indicating how long to wait for the request to finish. (optional, default 4000)
• try_edns -- a boolean indicating whether to use an EDNSPacket (optional)
• cache -- can be false to disable caching, or implement the cache model, or an instance of Cache but with a different store (optional, default platform.cache)

There are only two methods

• send -- sends the actual request to the remote endpoint
• cancel -- cancels the request and ignores any responses

Request emits the following events

• message -- This is where you get a response, passes (err, answer) where answer is an instance of Packet
• timeout -- Fired when the timeout is reached
• cancelled -- Fired if the request is cancelled
• end -- Always fired after a request finished, regardless of disposition

Platform

If you want to customize all resolve or lookups with the replacement client stack you can modify the platform settings accessible in the top level platform object.

Methods:

• reload -- Re-read system configuration files to populate name servers and hosts

Properties:

• ready -- Boolean whether requests are safe to transit, true after hosts and name servers are filled
• watching -- Boolean indicating if system configuration files are watched for changes, default to false (currently can only be enabled on !win32)
• name_servers -- An array of servers used for resolving queries against

• Each entry is an object of { address: <string ip>, port: 53 }
• On win32 this is hard coded to be google dns until there's a sane way to get the data

• search_path -- An array of domains to try and append after a failed lookup
• attempts -- The number of retries for a failed lookup/timeout (default: 5)
• timeout -- The time each query is allowed to take before trying another server. (in milliseconds, default: 5000 (5 seconds))
• edns -- Whether to try and send edns queries first (default: false)
• cache -- The system wide cache used by default for lookup and resolve, set this to false to disable caching

Events:

• ready -- Emitted after hosts and name servers have been loaded
• unready -- Emitted when hosts and name servers configuration is being reloaded.

Server

There is also a rudimentary server implementation

var dns = require('../dns'),
  server = dns.createServer();

server.on('request', function (request, response) {
  //console.log(request)
  response.answer.push(dns.A({
    name: request.question[0].name,
    address: '127.0.0.1',
    ttl: 600,
  }));
  response.answer.push(dns.A({
    name: request.question[0].name,
    address: '127.0.0.2',
    ttl: 600,
  }));
  response.additional.push(dns.A({
    name: 'hostA.example.org',
    address: '127.0.0.3',
    ttl: 600,
  }));
  response.send();
});

server.on('error', function (err, buff, req, res) {
  console.log(err.stack);
});

server.serve(15353);

Server creation

• createServer and createUDPServer -- both create a UDP based server, they accept an optional object for configuration,

• { dgram_type: 'udp4' } is the default option, the other is udp6

• createTCPServer -- creates a TCP based server

Server methods

• serve(port, [address]) -- specify which port and optional address to listen on
• close() -- stop the server/close sockets.

Server events

• listening -- emitted when underlying socket is listening
• close -- emitted when the underlying socket is closed
• request -- emitted when a dns message is received, and the packet was successfully unpacked, passes (request, response)

• Both request and response are instances of Packet when you're finished creating the response, you merely need to call .send() and the packet will DoTheRightThing

• error -- emitted when unable to properly unpack the packet, passed (err, msg, response)
• socketError -- remap of the underlying socket for the server, passes (err, socket)

Packet

Properties:

• header

• id -- request id
• qdcount -- the number of questions (inferred from array size)
• ancount -- the number of questions (inferred from array size)
• nscount -- the number of questions (inferred from array size)
• arcount -- the number of questions (inferred from array size)
• qr -- is a query response
• opcode
• aa -- Authoritative Answer
• tc -- Truncation bit
• rd -- Recursion Desired
• ra -- Recursion Available
• res1 -- Reserved field
• res2 -- Reserved field
• res3 -- Reserved field
• rcode -- Response Code (see consts.NAME_TO_RCODE)

• question -- array of Questions
• answer -- array of ResourceRecords
• authority -- array of ResourceRecords
• additional -- array of ResourceRecords

Methods:

• send() -- Handles sending the packet to the right end point

Question

A Question is instantiated by passing an object like:

• name -- i.e. 'www.google.com' (required)
• type -- Either the string representation of the record type, or the integer value, see consts.NAME_TO_QTYPE (default: 'A')
• class -- The class of service, default to 1 meaning internet

ResourceRecord

ResourceRecords are what populate answer, authority, and additional. This is a generic type, and each derived type inherits the following properties:

• name -- The name of the resource
• type -- The numerical representation of the resource record type
• class -- The numerical representation of the class of service (usually 1 for internet)
• ttl -- The Time To Live for the record, in seconds

Available Types:

• SOA

• primary -- string
• admin -- string
• serial -- number
• refresh -- number
• retry -- number
• expiration -- number
• minimum -- number

• A and AAAA

• address -- string

• MX

• priority -- number
• exchange -- string

• TXT

• data -- string

• SRV

• priority -- number
• weight -- number
• port -- number
• target -- string

• NS

• data -- string

• CNAME

• data -- string

• PTR

• data -- string

• NAPTR

• order -- number
• preference -- number
• flags -- string
• service -- string
• regexp -- string
• replacement -- string

Cache

If you perform a query on an A or AAAA type and it doesn't exist, the cache will attempt to lookup a CNAME and then resolve that.

The constructor takes an optional object with the following properties:

• store -- implements the cache store model (optional, default MemoryStore)

Methods:

• lookup(question, cb) -- for a given question check the cache store for existence
• store(packet) -- iterates over the resource records in a packet and sends them to the cache store
• purge() -- clears the cache store of all entries

MemoryStore / Cache store model

MemoryStore(opts) -- An in memory store based on a js object

Methods:

• get(domain, key, cb)

• domain is the holder under which keys will be applied, key is the subdomain that is being queried for. If you get('example.com', 'www', cb) you are really asking for www.example.com.
• cb(err, results) -- results is an object of types and array of answers

• { 1: [{address: '127.0.0.1', ttl: 300, type: 1, class: 1}] }
• set(domain, key, data, cb)

• domain is the parent under which this key is stored. key is the subdomain we are storing, data is an object of types with an array of answers.

• set('example.com', 'www', {1: [{class:1, type:1, ttl:300, address:'127.0.0.1'}]}, cb)

• cb(err, data) -- cb merely returns the data that was passed.

• delete(domain[, key[, type]], cb) -- delete all from a domain, a domain and key, or a domain a key and a type.

Lookup

Is a mechanism that given a store performs the common resolution pattern.

Given example.com previous added to a store:

• www.example.com CNAME foo.bar.example.com.
• *.example.com A 127.0.0.1

A Lookup(store, 'example.com', {name:'www.example.com', type:1}, cb) will resolve www to the CNAME and then search for foo.bar.example.com which will return no results, and then search for *.bar.example.com which will also return no results, and ultimately searches for *.example.com which will return the desired record.

Callback will be called with (err, results) where results is an array suitable for use in Packet.answer