node-named-client

A DNS client library using the packet parsing/generating code from node-mname.

Example

const mod_mname_client = require('mname-client');

var client = new mod_name_client.DnsClient({
    /* Will try all of the set name servers in parallel. */
    resolvers: ['8.8.8.8', '8.8.4.4']
});

client.lookup({
    domain: 'google.com',
    type: 'AAAA',
    timeout: 3000
}, function (err, message) {
        if (err) {
                /* ... */
                return;
        }
        var ans = msg.getAnswers();
        /* ans will look like: */
        ans = [ { name: 'google.com',
          type: 'A',
          class: 'IN',
          ttl: 299,
          target: '216.58.192.14' } ];
});

Example (low-level API)

const mod_mname_client = require('mname-client');

var req = new mod_mname_client.DnsMessage();

req.addQuestion('google.com', 'A');
req.addEDNS({ maxUDPLength: 1480 });

req.on('error', function (err) {
  /*
   * For socket-level errors that occurred while our request was
   * outstanding
   */
  ...
});
req.on('reply', function (msg, done) {
  if (msg.isError()) {
    /* For successful DNS queries that returned an error code. */
    var e = msg.toError();
    ...
    done();
    return;
  }
  var ans = msg.getAnswers();
  /* ans will look like: */
  ans = [ { name: 'google.com',
    type: 'A',
    class: 'IN',
    ttl: 299,
    target: '216.58.192.14' } ];

  /*
   * Need to call done() to indicate that this query is complete.
   * This is important so that AXFR and similar queries that can result
   * in multiple replies know when they are finished (the receiver of
   * the results can tell by comparing the SOA at the top and bottom)
   */
  done();
});

var sock = new mod_mname_client.DnsTcpSocket({
  address: '8.8.8.8',
  port: 53
});
sock.on('ready', function () {
  /*
   * sock.send can throw if the query cannot be encoded (e.g. it's
   * way too big)
   */
  sock.send(req);

  /* Call end once you've added all pipelined queries you want. */
  sock.end();
});
sock.on('error', function (err) {
  /*
   * A socket-level error resulting in this connection being unusable.
   * If this happens after sock.send() was called in on('ready') above, then
   * we will get an 'error' event on the req as well.
   */
});

var sock = new mod_mname_client.DnsUdpSocket({ family: 'udp4' });
sock.on('ready', function () {
  /*
   * You have to provide a destination to send on a DnsUdpSocket, as you
   * can re-use the one bound socket for multiple destinations.
   */
  sock.send(req, { address: '8.8.8.8', port: 53 });

  /* Will cause the socket to close after the last outstanding query returns. */
  sock.end();
});
sock.on('error', function (err) {
  /* A socket-level error resulting in this socket being unusable. */
});

API

new mod_mname_client.DnsClient([options])

Parameters:

• options -- an optional Object, with keys:
  • resolvers -- an optional Array of String, IP addresses of nameservers to use
  • concurrency -- an optional Number, max number of requests to send at once, default 3

DnsClient#close()

Ends all sockets and waits for outstanding DNS requests to finish or time out before closing.

DnsClient#lookup(options, cb)

Look up a name and return the first successful result as a DnsMessage.

Parameters:

• options -- Object, with keys:
  • domain -- String, domain to look up
  • type -- String, the query type (qtype), e.g. "AAAA"
  • timeout -- Number, milliseconds
  • resolvers -- optional Array of String, resolvers to use just for this request
  • filter -- optional Func (msg), if provided will run on each DnsMessage before sending (useful to set flags or sign requests)
• cb -- Func (err, message) with parameters:
  • err -- either null or an Error instance
  • message -- a DnsMessage (if err is null)

new mod_mname_client.DnsMessage()

Construct a new, empty DNS message. The message is also an EventEmitter.

DnsMessage->error(err)

Event emitted when the DNS message experiences an error because of a network or system failure. This is not emitted if the message receives a reply that is an error-type reply (e.g. isError() on the reply would return true).

Parameters:

• err -- an Error object

DnsMessage->reply(msg)

Event emitted when a reply to the DNS message is received.

Parameters:

• msg -- a DnsMessage instance

DnsMessage#isError()

Returns true if this message indicates an error (either by the rcode being something other than NOERROR, or the truncation flag being set).

DnsMessage#toError([resolver])

Converts the DnsMessage into an Error object with a descriptive message about the error that occurred. The optional resolver parameter is included in the Error messages.

If the DnsMessage does not represent any kind of error condition, this function returns null. The returned errors will be named either TruncationError or DnsError.

Parameters:

• resolver -- optional String, resolver IP or name to include in error message

DnsMessage#getAnswers()

Returns the answer part of the DNS message as an Array of Record Objects, of the form:

{
  "name": "domain.foo.com",
  "type": "AAAA",
  "class": "IN",
  "ttl": 30,
  "address": "abcd::1"
}

The name, type, class and ttl properties are available on all types of record. Other fields such as address appear only on the relevant type.

DnsMessage#getAuthority()

Returns the authority section of the DNS message as an Array of Record Objects (see getAnswers()).

DnsMessage#getAdditionals()

Returns the additional section of the DNS message as an Array of Record Objects (see getAnswers()).

DnsMessage#testFlag(flag)

Returns true if a given flag is set in the message header. Valid flag names:

• qr, response
• aa, authoritative
• rd, recursionDesired
• ra, recursionAvailable
• ad, authenticated
• cd, noChecking
• cd, checkingDisabled

Parameters:

• flag -- a String

DnsMessage#setFlag(flag)

DnsMessage#clearFlag(flag)

Sets or clears a given flag (see testFlag() for a list of values).

Parameters:

• flag -- a String

DnsMessage#addQuestion(name, type, qclass)

Adds a question section to the DNS message.

Parameters:

• name -- a String, the domain name to be questioned
• type -- a String, the record type desired (e.g. 'AAAA')
• qclass -- a String, the query class (e.g. 'IN')

DnsMessage#addEDNS(options)

Adds EDNS to the message.

Parameters

• options -- an Object, with keys:
  • maxUDPLength -- a Number, the maximum length of UDP frames

new mod_mname_client.DnsTcpSocket(options)

Creates a new TCP-based DNS client socket.

Parameters:

• options -- an Object, with keys:
  • address -- a String, IP address of remote machine
  • port -- a Number, the port to connect to

new mod_mname_client.DnsUdpSocket(options)

Creates a new UDP-based DNS client socket.

Parameters:

• options -- an Object, with keys:
  • family -- a String, either 'udp4' or 'udp6'

DnsSocket->ready()

Event emitted by DnsTcpSocket or DnsUdpSocket when the socket is open and ready for use.

DnsSocket->error(err)

Event emitted by DnsTcpSocket or DnsUdpSocket when a socket-level error is experienced.

Parameters:

• err -- an Error object

DnsSocket#end()

Wait for any outstanding requests to complete, and then close the socket.

DnsSocket#isReady()

Returns true if the socket has emitted the ->ready event.

DnsSocket#send(msg[, destination])

Sends a DnsMessage over the socket.

Parameters:

• msg -- a DnsMessage object
• destination -- a String, optional for TCP sockets, required for UDP (must be remote address to send message to)