An abstract-encoding compliant module for encoding / decoding DNS packets. Lifted out of multicast-dns as a separate module.
npm install dns-packet
var packet = require('dns-packet') var dgram = require('dgram') var socket = dgram.createSocket('udp4') var buf = packet.encode({ type: 'query', id: 1, flags: packet.RECURSION_DESIRED, questions: [{ type: 'A', name: 'google.com' }] }) socket.on('message', function (message) { console.log(packet.decode(message)) // prints out a response from google dns }) socket.send(buf, 0, buf.length, 53, '8.8.8.8')
var buf = packets.encode(packet, [buf], [offset])
Encodes a DNS packet into a buffer.
var packet = packets.decode(buf, [offset])
Decode a DNS packet from a buffer
var len = packets.encodingLength(packet)
Returns how many bytes are needed to encode the DNS packet
Packets look like this
{ type: 'query|response', id: optionalIdNumber, flags: optionalBitFlags, questions: [...], answers: [...], additionals: [...], authorities: [...] }
The bit flags available are
packet.RECURSION_DESIRED packet.RECURSION_AVAILABLE packet.TRUNCATED_RESPONSE packet.AUTHORITATIVE_ANSWER packet.AUTHENTIC_DATA packet.CHECKING_DISABLED
To use more than one flag bitwise-or them together
var flags = packet.RECURSION_DESIRED | packet.RECURSION_AVAILABLE
And to check for a flag use bitwise-and
var isRecursive = message.flags & packet.RECURSION_DESIRED
A question looks like this
{ type: 'A', // or SRV, AAAA, etc name: 'google.com' // which record are you looking for }
And an answers, additional, or authority looks like this
{ type: 'A', // or SRV, AAAA, etc name: 'google.com', // which name is this record for ttl: optionalTimeToLiveInSeconds, (record specific data, see below) }
Currently the different available records are
A
{ data: 'IPv4 address' // fx 127.0.0.1 }
AAAA
{ data: 'IPv6 address' // fx fe80::1 }
TXT
{ data: Buffer('some text') }
NS
{ data: nameServer }
NULL
{ data: Buffer('any binary data') }
SOA
{ data: { mname: domainName, rname: mailbox, serial: zoneSerial, refresh: refreshInterval, retry: retryInterval, expire: expireInterval, minimum: minimumTTL } }
SRV
{ data: { port: servicePort, target: serviceHostName, priority: optionalServicePriority, weight: optionalServiceWeight } }
HINFO
{ data: { cpu: 'cpu info', os: 'os info' } }
PTR
{ data: 'points.to.another.record' }
CNAME
{ data: 'cname.to.another.record' }
DNAME
{ data: 'dname.to.another.record' }
CAA
{ flags: 128, // octet tag: 'issue|issuewild|iodef', value: 'ca.example.net' }
If you need another one, open an issue and we'll try to add it.
MIT