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

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

var start = Date.now();

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 = (Date.now()) - 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
ad -- Reserved field
cd -- 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

RRSIG

typeCovered -- string
algorithm -- number
labels -- number
originalTtl -- number
signatureExpiration -- number
signatureInception -- number
keytag -- number
signerName -- string
signature -- string

DS

keytag -- number
algorithm -- number
digestType -- number
digest -- string

DNSKEY

flags -- string
protocol -- number
algorithm -- string
publicKey -- string

NSEC

next -- string
types -- string

NSEC3

hashAlgorithm -- number
flags -- number
iterations -- number
salt -- string
nextHashedOwnerName -- string

NSEC3PARAM

hashAlgorithm -- number
flags -- number
iterations -- number
salt -- string
nextHashedOwnerName -- string

Keywords

FAQs

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Package last updated on 11 Feb 2023

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