tessl/npm-dns-packet

An abstract-encoding compliant module for encoding and decoding DNS packets with support for all major DNS record types and transport protocols

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Utility Functions

Name: tessl/npm-dns-packet
Author: tessl

Type conversion utilities for DNS record types, response codes, operation codes, DNS classes, and EDNS0 option codes.

Capabilities

DNS Record Types

Conversion between DNS record type names and numeric values.

const types = require('dns-packet/types');

// Convert type number to string
types.toString(type);

// Convert type string to number
types.toType(name);

Supported Record Types:

Basic: A (1), AAAA (28), CNAME (5), NS (2), PTR (12), TXT (16)
Mail: MX (15), SOA (6)
Service: SRV (33), NAPTR (35)
Security: DNSKEY (48), RRSIG (46), DS (43), NSEC (47), NSEC3 (50)
Other: CAA (257), HINFO (13), NULL (10), OPT (41), TLSA (52), SSHFP (44)

Usage Examples:

const types = require('dns-packet/types');

// Type to string conversion
console.log(types.toString(1));    // 'A'
console.log(types.toString(28));   // 'AAAA'
console.log(types.toString(15));   // 'MX'
console.log(types.toString(999));  // 'UNKNOWN_999'

// String to type conversion
console.log(types.toType('A'));      // 1
console.log(types.toType('AAAA'));   // 28
console.log(types.toType('MX'));     // 15
console.log(types.toType('INVALID')); // 0

// Case insensitive
console.log(types.toType('a'));      // 1
console.log(types.toType('Aaaa'));   // 28

// Special handling for UNKNOWN_ prefix
console.log(types.toType('UNKNOWN_999')); // 999

DNS Response Codes

Conversion between DNS response code names and numeric values.

const rcodes = require('dns-packet/rcodes');

// Convert response code number to string
rcodes.toString(rcode);

// Convert response code string to number
rcodes.toRcode(code);

Supported Response Codes:

NOERROR (0): No error
FORMERR (1): Format error
SERVFAIL (2): Server failure
NXDOMAIN (3): Name does not exist
NOTIMP (4): Not implemented
REFUSED (5): Query refused
YXDOMAIN (6): Name should not exist
YXRRSET (7): RRset should not exist
NXRRSET (8): RRset does not exist
NOTAUTH (9): Not authoritative
NOTZONE (10): Name not in zone

Usage Examples:

const rcodes = require('dns-packet/rcodes');

// Response code to string
console.log(rcodes.toString(0));   // 'NOERROR'
console.log(rcodes.toString(3));   // 'NXDOMAIN'
console.log(rcodes.toString(2));   // 'SERVFAIL'
console.log(rcodes.toString(99));  // 'RCODE_99'

// String to response code
console.log(rcodes.toRcode('NOERROR'));   // 0
console.log(rcodes.toRcode('NXDOMAIN'));  // 3
console.log(rcodes.toRcode('SERVFAIL'));  // 2
console.log(rcodes.toRcode('INVALID'));   // 0

// Case insensitive
console.log(rcodes.toRcode('noerror'));   // 0
console.log(rcodes.toRcode('NxDomain'));  // 3

DNS Operation Codes

Conversion between DNS operation code names and numeric values.

const opcodes = require('dns-packet/opcodes');

// Convert operation code number to string
opcodes.toString(opcode);

// Convert operation code string to number
opcodes.toOpcode(code);

Supported Operation Codes:

QUERY (0): Standard query
IQUERY (1): Inverse query (obsolete)
STATUS (2): Server status request
NOTIFY (4): Zone change notification
UPDATE (5): Dynamic update

Usage Examples:

const opcodes = require('dns-packet/opcodes');

// Operation code to string
console.log(opcodes.toString(0));   // 'QUERY'
console.log(opcodes.toString(4));   // 'NOTIFY'
console.log(opcodes.toString(5));   // 'UPDATE'
console.log(opcodes.toString(99));  // 'OPCODE_99'

// String to operation code
console.log(opcodes.toOpcode('QUERY'));   // 0
console.log(opcodes.toOpcode('NOTIFY'));  // 4
console.log(opcodes.toOpcode('UPDATE'));  // 5
console.log(opcodes.toOpcode('INVALID')); // 0

// Case insensitive
console.log(opcodes.toOpcode('query'));   // 0
console.log(opcodes.toOpcode('Notify'));  // 4

DNS Classes

Conversion between DNS class names and numeric values.

const classes = require('dns-packet/classes');

// Convert class number to string
classes.toString(klass);

// Convert class string to number
classes.toClass(name);

Supported DNS Classes:

IN (1): Internet class (most common)
CS (2): CSNET class (obsolete)
CH (3): Chaos class
HS (4): Hesiod class
ANY (255): Any class (queries only)

Usage Examples:

const classes = require('dns-packet/classes');

// Class to string
console.log(classes.toString(1));    // 'IN'
console.log(classes.toString(3));    // 'CH'
console.log(classes.toString(255));  // 'ANY'
console.log(classes.toString(99));   // 'UNKNOWN_99'

// String to class
console.log(classes.toClass('IN'));      // 1
console.log(classes.toClass('CH'));      // 3
console.log(classes.toClass('ANY'));     // 255
console.log(classes.toClass('INVALID')); // 0

// Case insensitive
console.log(classes.toClass('in'));      // 1
console.log(classes.toClass('Ch'));      // 3

EDNS0 Option Codes

Conversion between EDNS0 option code names and numeric values.

const optioncodes = require('dns-packet/optioncodes');

// Convert option code number to string
optioncodes.toString(type);

// Convert option code string/number to number
optioncodes.toCode(name);

Supported EDNS0 Options:

LLQ (1): Long-Lived Queries
UL (2): Update Lease
NSID (3): Name Server Identifier
DAU (5): DNSSEC Algorithm Understood
DHU (6): DS Hash Understood
N3U (7): NSEC3 Hash Understood
CLIENT_SUBNET (8): Client subnet information
EXPIRE (9): EDNS Expire
COOKIE (10): DNS Cookies
TCP_KEEPALIVE (11): TCP keepalive
PADDING (12): Padding
CHAIN (13): Chain query
KEY_TAG (14): Key tag
DEVICEID (26946): Device ID

Usage Examples:

const optioncodes = require('dns-packet/optioncodes');

// Option code to string
console.log(optioncodes.toString(8));     // 'CLIENT_SUBNET'
console.log(optioncodes.toString(12));    // 'PADDING'
console.log(optioncodes.toString(10));    // 'COOKIE'
console.log(optioncodes.toString(999));   // 'OPTION_999'

// String/number to option code
console.log(optioncodes.toCode('CLIENT_SUBNET')); // 8
console.log(optioncodes.toCode('PADDING'));       // 12
console.log(optioncodes.toCode('COOKIE'));        // 10
console.log(optioncodes.toCode(12));              // 12 (number passthrough)
console.log(optioncodes.toCode('OPTION_999'));    // 999
console.log(optioncodes.toCode('INVALID'));       // -1

// Case insensitive
console.log(optioncodes.toCode('client_subnet')); // 8
console.log(optioncodes.toCode('Padding'));       // 12

// Pattern matching for OPTION_N format
console.log(optioncodes.toCode('OPTION_123'));    // 123

Utility Usage in Practice

Building a DNS Query:

const dnsPacket = require('dns-packet');
const types = require('dns-packet/types');
const classes = require('dns-packet/classes');

const packet = {
  type: 'query',
  id: 1234,
  flags: dnsPacket.RECURSION_DESIRED,
  questions: [{
    type: types.toString(1),     // 'A'
    class: classes.toString(1),  // 'IN'
    name: 'example.com'
  }]
};

Processing a DNS Response:

const response = dnsPacket.decode(buffer);
const rcodes = require('dns-packet/rcodes');

// Check response code
const rcode = response.flags & 0x0F; // Extract RCODE from flags
if (rcode !== 0) {
  console.log('DNS error:', rcodes.toString(rcode));
}

// Process answers
response.answers.forEach(answer => {
  console.log(`${answer.name} ${answer.type} ${answer.data}`);
});

EDNS0 Option Processing:

const optioncodes = require('dns-packet/optioncodes');

// Find OPT record in additionals
const optRecord = packet.additionals.find(r => r.type === 'OPT');
if (optRecord) {
  optRecord.options.forEach(option => {
    const optionName = optioncodes.toString(option.code);
    console.log(`EDNS0 option: ${optionName} (${option.code})`);
  });
}

Install with Tessl CLI