nodedns

This is a server implementation of the DNS protocol.

Useful information

• freesoft.org's documentation of the DNS protcol
• justanapplication.wordpress.com's documentation on, among other things, how to encode an SRV record

Usage

const nodedns = require('nodedns');

const server = new nodedns.DNSServer(function(req, res) {
    var record = new nodedns.DNSMessageResource();

    // Name: www.example.com
    record.name = nodedns.DNSDomainName.fromLabels(['www', 'example', 'com']);

    // Record type: A
    record.type = 1;

    // Record class: IN
    record.rclass = 1;

    // TTL: 1 hour
    record.ttl = 3600;

    // Data: 127.0.0.1
    record.data = new Buffer([127, 0, 0, 1]);

    // Add record to 'answers' section of the response message
    res.answers.push(record);

    // Send response
    res.send();
});

server.listen(53);

Messages

Both requests and responses come in the form of DNSMessage instances. DNSMessage contains the following fields:

• header: DNSMessageHeader
• questions: DNSMessageQuestion
• answers: DNSMessageResource[]
• authorities: DNSMessageResource[]
• additionals: DNSMessageResource[]

Question structure

Requests typically contain 1 question in the questions array of the DNSMessage. This question contains the following fields:

• qname: DNSDomainName
• qtype: Number
• qclass: Number

Domain names

Domain names are represented by DNSDomainName. Instances of the class contain an array of labels.

To quickly convert a DNSDomainName to a readable domain one can use domain.labels.join('.')

There are two ways of creating a DNSDomainName:

// From an array of labels
var domain = nodedns.DNSDomainName.fromLabels(['www', 'example', 'com']);

// From a string representation
var domain = nodedns.DNSDomainName.fromString('www.example.com');

Resources

Resources or records are represented by DNSMessageResource objects. A DNSMessageResource contains the following fields:

• name: DNSDomainName
• type: Number
• rclass: Number
• ttl: Number
• rdlength: Number (This is ignored when encoding messages)
• rdata: Buffer