dns2

A DNS Server and Client Implementation in Pure JavaScript with no dependencies.

Features

• Server and Client
• Lot of Type Supported
• Extremely lightweight
• DNS over UDP, TCP, HTTPS Supported

Installation

$ npm install dns2

DNS Client (default UDP)

Lookup any records available for the domain lsong.org. DNS client will use UDP by default.

constdns2=require('dns2');constoptions={// nameServers: ['8.8.8.8'] — array of DNS server IPs (default: Google + 114dns)// port: 53 — DNS server port (number)// recursive: true — Recursion Desired flag (boolean, default true)};constdns=newdns2(options);(async()=>{constresult=awaitdns.resolveA('google.com');console.log(result.answers);})();

The high-level DNS class exposes convenience methods for common record types:

Method	Record type	Key answer fields
resolveA(domain)	A	address
resolveAAAA(domain)	AAAA	address
resolveMX(domain)	MX	exchange, priority
resolveCNAME(domain)	CNAME	domain
resolveSOA(domain)	SOA	primary, admin, serial, refresh, retry, expiration, minimum
resolvePTR(domain)	PTR	domain
resolveDNSKEY(domain)	DNSKEY	publicKey, algorithm
resolveRRSIG(domain)	RRSIG	varies

For any record type not listed above, use dns.resolve(domain, 'TYPE') directly.

Example: SOA record lookup

SOA (Start of Authority) records contain the authoritative zone information for a domain. If the authoritative nameserver returns the SOA record in the answer section, it will appear in result.answers. Otherwise check result.authorities.

constdns2=require('dns2');constdns=newdns2({nameServers: ['8.8.8.8']});(async()=>{constresult=awaitdns.resolveSOA('google.com');constsoa=result.answers[0]||result.authorities[0];if(soa){console.log(soa.primary);// ns1.google.comconsole.log(soa.admin);// dns-admin.google.comconsole.log(soa.serial);// zone serial numberconsole.log(soa.refresh);// refresh interval (seconds)console.log(soa.retry);// retry interval (seconds)console.log(soa.expiration);// expiry (seconds)console.log(soa.minimum);// minimum TTL (seconds)}})();

Another way to instanciate dns2 UDP Client:

const{ UDPClient }=require('dns2');constresolve=UDPClient();(async()=>{constresponse=awaitresolve('google.com')console.log(response.answers);})();

DNS Client (TCP)

Lookup any records available for the domain lsong.org. By default, DNS requests will use UDP.

const{ TCPClient }=require('dns2');constresolve=TCPClient();(async()=>{try{constresponse=awaitresolve('lsong.org')console.log(response.answers);}catch(error){// some DNS servers (i.e cloudflare 1.1.1.1, 1.0.0.1) // may send an empty response when using TCPconsole.log(error);}})();

Client Custom DNS Server

You can pass your own DNS Server.

const{ TCPClient }=require('dns2');constresolve=TCPClient({dns: '1.1.1.1'});(async()=>{try{constresult=awaitresolve('google.com');console.log(result.answers);}catch(error){console.log(error);}})();

System DNS Server

You can use the first DNS server from your OS with native node dns.

constdns=require('dns');const{ TCPClient }=require('dns2');constresolve=TCPClient({dns: dns.getServers()[0]});(async()=>{try{constresult=awaitresolve('google.com');console.log(result.answers);}catch(error){console.log(error);}})();

Example Server

constdns2=require('dns2');const{ Packet }=dns2;constserver=dns2.createServer({udp: true,handle: (request,send,rinfo)=>{constresponse=Packet.createResponseFromRequest(request);const[question]=request.questions;const{ name }=question;response.answers.push({
name,type: Packet.TYPE.A,class: Packet.CLASS.IN,ttl: 300,address: '8.8.8.8'});send(response);}});server.on('request',(request,response,rinfo)=>{console.log(request.header.id,request.questions[0]);});server.on('requestError',(error)=>{console.log('Client sent an invalid request',error);});server.on('listening',()=>{console.log(server.addresses());});server.on('close',()=>{console.log('server closed');});server.listen({// Optionally specify port, address and/or the family of socket() for udp server:udp: {port: 5333,address: "127.0.0.1",},// Optionally specify port and/or address for tcp server:tcp: {port: 5333,address: "127.0.0.1",},});// eventuallyserver.close();

Then you can test your DNS server:

$ dig @127.0.0.1 -p5333 lsong.org

Note that when implementing your own lookups, the contents of the query will be found in request.questions[0].name.

Responding with DNS Error Codes

Use Packet.RCODE to send standard DNS error responses from your handler:

Constant	Value	Meaning
Packet.RCODE.NOERROR	0	No error
Packet.RCODE.FORMERR	1	Format error
Packet.RCODE.SERVFAIL	2	Server failure
Packet.RCODE.NXDOMAIN	3	Non-existent domain
Packet.RCODE.NOTIMP	4	Not implemented
Packet.RCODE.REFUSED	5	Query refused

constdns2=require('dns2');const{ Packet }=dns2;constserver=dns2.createServer({udp: true,handle: (request,send)=>{constresponse=Packet.createResponseFromRequest(request);const[question]=request.questions;if(question.name.endsWith('.internal')){// Refuse queries for internal namesresponse.header.rcode=Packet.RCODE.REFUSED;returnsend(response);}if(!isKnownDomain(question.name)){// Domain does not existresponse.header.rcode=Packet.RCODE.NXDOMAIN;returnsend(response);}// Normal answer ...response.answers.push({name: question.name,type: Packet.TYPE.A,class: Packet.CLASS.IN,ttl: 300,address: '1.2.3.4'});send(response);}});

Performance and Benchmarking

see benchmark/README.md

Relevant Specifications

• RFC-1034 - Domain Names - Concepts and Facilities
• RFC-1035 - Domain Names - Implementation and Specification
• RFC-2782 - A DNS RR for specifying the location of services (DNS SRV)
• RFC-7766 - DNS Transport over TCP - Implementation Requirements
• RFC-8484 - DNS Queries over HTTPS (DoH)

Contributing

• Fork this Repo first
• Clone your Repo
• Install dependencies by $ npm install
• Checkout a feature branch
• Feel free to add your features
• Make sure your features are fully tested
• Publish your local branch, Open a pull request
• Enjoy hacking <3

MIT license

Copyright (c) 2016 LIU SONG song940@gmail.com & contributors.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS," WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.