An abstract-encoding compliant module for encoding / decoding DNS packets. Lifted out of multicast-dns as a separate module.
npm install dns-packet
``` js 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
js
{
type: 'query|response',
id: optionalIdNumber,
flags: optionalBitFlags,
questions: [...],
answers: [...],
additionals: [...],
authorities: [...]
}
The bit flags available are
js
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
js
var flags = packet.RECURSION_DESIRED | packet.RECURSION_AVAILABLE
And to check for a flag use bitwise-and
js
var isRecursive = message.flags & packet.RECURSION_DESIRED
A question looks like this
js
{
type: 'A', // or SRV, AAAA, etc
name: 'google.com' // which record are you looking for
}
And an answers, additional, or authority looks like this
js
{
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
Ajs
{
data: 'IPv4 address' // fx 127.0.0.1
}
AAAAjs
{
data: 'IPv6 address' // fx fe80::1
}
TXTjs
{
data: Buffer('some text')
}
NSjs
{
data: nameServer
}
NULLjs
{
data: Buffer('any binary data')
}
SOAjs
{
data:
{
mname: domainName,
rname: mailbox,
serial: zoneSerial,
refresh: refreshInterval,
retry: retryInterval,
expire: expireInterval,
minimum: minimumTTL
}
}
SRVjs
{
data: {
port: servicePort,
target: serviceHostName,
priority: optionalServicePriority,
weight: optionalServiceWeight
}
}
HINFOjs
{
data: {
cpu: 'cpu info',
os: 'os info'
}
}
PTRjs
{
data: 'points.to.another.record'
}
CNAMEjs
{
data: 'cname.to.another.record'
}
DNAMEjs
{
data: 'dname.to.another.record'
}
CAAjs
{
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