bindns

bindns: Fast DNS library, server and client for Node.js based on libbind-6

A DNS client and server built from a port of libbind with zero dependencies. It's very fast: it has about the same throughput as a server written with the evldns C library (~50k QPS on a 4.0 GHz i7-6700k CPU), and given that it's a port of libbind, hopefully it's low on bugs.

See history at the bottom for info on all of the forks of ndns and how this library came to be.

This module isn't published to npm yet, so install it from github: yarn add primitybio/bindns.

Example

An example DNS server which responds with a "Hello World" TXT record:

const bindns = require("bindns");

const server = new bindns.Server("udp4", (req, res) => {
    res.header.aa = 1; // Authoritative for this zone.
    res.header.rcode = bindns.ns_rcode.noerror; // NOERROR response code
    res.addRR(
        bindns.ns_sect.an,    // answer section
        req.question[0].name, // host name
        bindns.ns_type.txt,   // TXT record
        bindns.ns_class.in,   // IN
        3600,                 // TTL
        "hello, world"        // data
    );
    res.send();
});

server.on("listening", () => console.log("Server running at 0.0.0.0:5300"));

server.bind(5300);

See the examples folder for two additional examples.

API

DNS request and response messages are represented by an object like this:

ServerRequest {
    header: MessageHeader {
        id: 39545,
        qr: 0,
        opcode: 0,
        aa: 0,
        tc: 0,
        rd: 1,
        ra: 0,
        z: 0,
        ad: 0,
        cd: 0,
        rcode: 0,
        qdcount: 1,
        ancount: 0,
        nscount: 0,
        arcount: 1
    },
    question: [
        MessageQuestion {
            name: "example.com",
            type: 1,
            class: 1
        }
    ],
    answer: [],
    authoritative: [],
    additional: [
        MessageRR {
            name: ".",
            type: 41,
            class: 4096,
            ttl: 0,
            rdata: [ ... ]
        }
    ],
    socket: dgram.Socket { ... },
    rinfo: {
        address: "127.0.0.1",
        family: "IPv4",
        port: 52289,
        size: 41
    }
})

There are several enums that you need to construct a response, including the common ones listed below. See lib/nameser.js for the full list.

• ns_rcode - Response codes
• ns_sect - Section constants
• ns_class - Values for the class field
• ns_type - Values for the type field. To convert an ns_type number to its corresponding string, use ns_type_str(ns_type_t).
• ns_flag - Flag constants

ndns.Server

Constructor

new Server(type: "udp4"|"udp6"[, listener: (req, res) => void])

listener is an optional listener for the "request" event.

Event: "request"

function (request: ServerRequest, response: ServerResponse) {}

Event: "listening"

Inherited from dgram.Socket.

Event: "close"

Inherited from dgram.Socket.

Evenet: "error"

Inherited from dgram.Socket.

ServerRequest

This object is created internally by a DNS server as the result of a DNS query, not by the user, and passed as the first argument to a 'request' listener. Note: answer, authoritative and additional properties are present, but are meaningless in queries.

request.header

This object is an instance of MessageHeader. Properties:

• id (read-only) ID of query.
• qr (read-only) Query/response flag.
• opcode (read-only) Operation code (one of ns_opcode).
• aa (N/A for queries) Authoritative answer.
• tc (N/A for queries) Truncation flag.
• rd (read-only) Recursion desired.
• ra (N/A for queries) Recursion available.
• z (read-only) Three bits set to zero.
• ad (N/A for queries) Authentic data (DNSSEC).
• cd (read-only) Checking disabled (DNSSEC).
• rcode Response code (one of ns_rcode).
• qdcount, ancount, nscount and arcount (read-only) The number of questions, answers, name servers and additional records, respectively. Only qdcount should be non-zero for queries.

request.question

An array of MessageQuestions.

ServerResponse

This object is created internally by a DNS server, not by the user. It is passed as the second argument to the 'request' event.

response.header

This object is an instance of MessageHeader. Properties:

• id (read-only) ID of query, copied from the request.
• qr (read-only) Query/response flag, set to 1 for responses.
• opcode (read-only) Operation code, copied from the request (one of ns_opcode).
• aa Authoritative answer.
• tc Truncation flag.
• rd (read-only) Recursion desired, copied from the request.
• ra Recursion available.
• z (read-only) Three bits set to zero.
• ad Authentic data (DNSSEC).
• cd (read-only) Checking disabled (DNSSEC), copied from the request.
• rcode Response code (one of ns_rcode).
• qdcount, ancount, nscount and arcount (read-only) The number of questions, answers, name servers and additional records, respectively. These are incremented when you call response.addRR().

response.addRR(sect, name, type, klass, ttl, ...info)

Adds an RR to the response.

• @param {number} sect An ns_sect value.
• @param {string} name
• @param {number} type An ns_type value.
• @param {number} klass An ns_class value.
• @param {number} ttl
• @param {Array} info

response.answer

An array of MessageRRs.

response.authoritative

An array of MessageRRs.

response.additional

An array of MessageRRs.

ClientRequest

This object is created by client.request(port, host, callback).

request.addQuestion(name, type, class)

Sets the question.

Benchmarks and Other Libraries

Check out https://github.com/zbjornson/node-dnsperf for benchmarking.

Library	Throughput (QPS)	Latency (ms)	Notes
this library	50,295	1.9
https://github.com/raybellis/evldns	50,570	1.9	C library
https://github.com/tjfontaine/node-dns (published to npm as native-dns)	35,042	2.8	Working. No longer maintained. Many forks exist.
https://github.com/trevoro/node-named or the fork https://github.com/kaija/dns-express	24,300	4.1	Some bugs and not a lot of maintenance activity.
https://github.com/jhs/dnsd	18,000	5.7	Working and simple, but doesn't appear to be maintained.
https://github.com/chjj/bns	12,900	6.9	Not fully working

To-Do List and Technical Details

• There is no TCP fallback support.
• I haven't looked yet if the truncation flag is set automatically on overflow.
• Improve test suite (see test.js for info).
• DNSSEC - the flags are here for it, but I've never used it and don't know what a full implementation looks like.

History

As far as I can tell... the original source of this was jsjohnst/ndns. The ndns module published to npm is from someone named "skmplr" or "skampler" (can't find their source repo). The fork at atrniv/ndns has some changes to the original source.

This module pulls from all three, and has some additional significant changes:

• Code organization, ES6-ification, JSDoc.
  • Split code into separate files, following the organization of libbind.
  • Restored some of the names back to the original ones used in libbind (e.g. ns_f -> ns_flag).
  • Added JSDoc with type annotations, taking from libbind. VSCode's analyzer reports no type errors.
• Code errors fixed.
  • errno consistently set to numbers.
  • Remove use of reserved word class.
  • Remove usage of node's deprecated sys module.
  • Remove freelist dependency.
  • Some typos ("authorative" -> "authoritative", "buffer.Length" -> "buffer.length")
  • ClientRequest sets an ID automatically.
  • ClientRequest increments qdcount automatically when adding a question.
  • client.request now accepts a callback. While you can still listen to the "response" event on the client, I'm not sure what the utility would be. Might remove that functionality.
  • Don't make globals.
  • Fix possible infinite loop (https://github.com/primitybio/bindns/issues/1).
• Docs and examples updated.