402 lines
6.9 KiB
Markdown
402 lines
6.9 KiB
Markdown
# dns-packet
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[](https://www.npmjs.org/package/dns-packet) [](https://www.npmjs.org/package/dns-packet) [](https://github.com/github/mafintosh/dns-packet/workflows/ci.yml) [](https://coveralls.io/github/mafintosh/dns-packet?branch=master)
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An [abstract-encoding](https://github.com/mafintosh/abstract-encoding) compliant module for encoding / decoding DNS packets. Lifted out of [multicast-dns](https://github.com/mafintosh/multicast-dns) as a separate module.
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```
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npm install dns-packet
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```
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## UDP Usage
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``` js
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const dnsPacket = require('dns-packet')
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const dgram = require('dgram')
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const socket = dgram.createSocket('udp4')
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const buf = dnsPacket.encode({
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type: 'query',
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id: 1,
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flags: dnsPacket.RECURSION_DESIRED,
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questions: [{
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type: 'A',
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name: 'google.com'
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}]
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})
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socket.on('message', message => {
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console.log(dnsPacket.decode(message)) // prints out a response from google dns
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})
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socket.send(buf, 0, buf.length, 53, '8.8.8.8')
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```
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Also see [the UDP example](examples/udp.js).
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## TCP, TLS, HTTPS
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While DNS has traditionally been used over a datagram transport, it is increasingly being carried over TCP for larger responses commonly including DNSSEC responses and TLS or HTTPS for enhanced security. See below examples on how to use `dns-packet` to wrap DNS packets in these protocols:
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- [TCP](examples/tcp.js)
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- [DNS over TLS](examples/tls.js)
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- [DNS over HTTPS](examples/doh.js)
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## API
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#### `var buf = packets.encode(packet, [buf], [offset])`
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Encodes a DNS packet into a buffer containing a UDP payload.
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#### `var packet = packets.decode(buf, [offset])`
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Decode a DNS packet from a buffer containing a UDP payload.
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#### `var buf = packets.streamEncode(packet, [buf], [offset])`
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Encodes a DNS packet into a buffer containing a TCP payload.
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#### `var packet = packets.streamDecode(buf, [offset])`
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Decode a DNS packet from a buffer containing a TCP payload.
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#### `var len = packets.encodingLength(packet)`
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Returns how many bytes are needed to encode the DNS packet
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## Packets
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Packets look like this
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``` js
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{
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type: 'query|response',
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id: optionalIdNumber,
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flags: optionalBitFlags,
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questions: [...],
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answers: [...],
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additionals: [...],
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authorities: [...]
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}
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```
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The bit flags available are
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``` js
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packet.RECURSION_DESIRED
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packet.RECURSION_AVAILABLE
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packet.TRUNCATED_RESPONSE
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packet.AUTHORITATIVE_ANSWER
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packet.AUTHENTIC_DATA
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packet.CHECKING_DISABLED
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```
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To use more than one flag bitwise-or them together
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``` js
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var flags = packet.RECURSION_DESIRED | packet.RECURSION_AVAILABLE
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```
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And to check for a flag use bitwise-and
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``` js
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var isRecursive = message.flags & packet.RECURSION_DESIRED
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```
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A question looks like this
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``` js
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{
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type: 'A', // or SRV, AAAA, etc
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class: 'IN', // one of IN, CS, CH, HS, ANY. Default: IN
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name: 'google.com' // which record are you looking for
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}
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```
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And an answer, additional, or authority looks like this
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``` js
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{
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type: 'A', // or SRV, AAAA, etc
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class: 'IN', // one of IN, CS, CH, HS
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name: 'google.com', // which name is this record for
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ttl: optionalTimeToLiveInSeconds,
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(record specific data, see below)
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}
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```
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## Supported record types
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#### `A`
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``` js
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{
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data: 'IPv4 address' // fx 127.0.0.1
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}
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```
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#### `AAAA`
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``` js
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{
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data: 'IPv6 address' // fx fe80::1
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}
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```
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#### `CAA`
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``` js
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{
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flags: 128, // octet
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tag: 'issue|issuewild|iodef',
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value: 'ca.example.net',
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issuerCritical: false
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}
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```
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#### `CNAME`
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``` js
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{
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data: 'cname.to.another.record'
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}
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```
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#### `DNAME`
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``` js
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{
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data: 'dname.to.another.record'
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}
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```
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#### `DNSKEY`
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``` js
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{
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flags: 257, // 16 bits
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algorithm: 1, // octet
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key: Buffer
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}
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```
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#### `DS`
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``` js
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{
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keyTag: 12345,
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algorithm: 8,
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digestType: 1,
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digest: Buffer
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}
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```
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#### `HINFO`
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``` js
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{
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data: {
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cpu: 'cpu info',
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os: 'os info'
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}
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}
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```
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#### `MX`
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``` js
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{
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preference: 10,
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exchange: 'mail.example.net'
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}
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```
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#### `NAPTR`
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``` js
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{
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data:
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{
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order: 100,
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preference: 10,
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flags: 's',
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services: 'SIP+D2U',
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regexp: '!^.*$!sip:customer-service@example.com!',
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replacement: '_sip._udp.example.com'
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}
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}
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```
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#### `NS`
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``` js
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{
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data: nameServer
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}
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```
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#### `NSEC`
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``` js
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{
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nextDomain: 'a.domain',
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rrtypes: ['A', 'TXT', 'RRSIG']
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}
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```
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#### `NSEC3`
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``` js
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{
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algorithm: 1,
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flags: 0,
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iterations: 2,
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salt: Buffer,
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nextDomain: Buffer, // Hashed per RFC5155
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rrtypes: ['A', 'TXT', 'RRSIG']
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}
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```
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#### `NULL`
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``` js
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{
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data: Buffer('any binary data')
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}
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```
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#### `OPT`
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[EDNS0](https://tools.ietf.org/html/rfc6891) options.
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``` js
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{
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type: 'OPT',
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name: '.',
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udpPayloadSize: 4096,
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flags: packet.DNSSEC_OK,
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options: [{
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// pass in any code/data for generic EDNS0 options
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code: 12,
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data: Buffer.alloc(31)
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}, {
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// Several EDNS0 options have enhanced support
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code: 'PADDING',
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length: 31,
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}, {
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code: 'CLIENT_SUBNET',
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family: 2, // 1 for IPv4, 2 for IPv6
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sourcePrefixLength: 64, // used to truncate IP address
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scopePrefixLength: 0,
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ip: 'fe80::',
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}, {
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code: 'TCP_KEEPALIVE',
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timeout: 150 // increments of 100ms. This means 15s.
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}, {
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code: 'KEY_TAG',
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tags: [1, 2, 3],
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}]
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}
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```
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The options `PADDING`, `CLIENT_SUBNET`, `TCP_KEEPALIVE` and `KEY_TAG` support enhanced de/encoding. See [optionscodes.js](https://github.com/mafintosh/dns-packet/blob/master/optioncodes.js) for all supported option codes. If the `data` property is present on a option, it takes precedence. On decoding, `data` will always be defined.
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#### `PTR`
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``` js
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{
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data: 'points.to.another.record'
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}
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```
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#### `RP`
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``` js
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{
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mbox: 'admin.example.com',
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txt: 'txt.example.com'
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}
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```
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#### `SSHFP`
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``` js
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{
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algorithm: 1,
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hash: 1,
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fingerprint: 'A108C9F834354D5B37AF988141C9294822F5BC00'
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}
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````
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#### `RRSIG`
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``` js
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{
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typeCovered: 'A',
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algorithm: 8,
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labels: 1,
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originalTTL: 3600,
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expiration: timestamp,
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inception: timestamp,
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keyTag: 12345,
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signersName: 'a.name',
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signature: Buffer
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}
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```
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#### `SOA`
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``` js
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{
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data:
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{
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mname: domainName,
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rname: mailbox,
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serial: zoneSerial,
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refresh: refreshInterval,
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retry: retryInterval,
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expire: expireInterval,
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minimum: minimumTTL
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}
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}
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```
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#### `SRV`
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``` js
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{
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data: {
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port: servicePort,
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target: serviceHostName,
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priority: optionalServicePriority,
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weight: optionalServiceWeight
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}
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}
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```
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#### `TLSA`
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``` js
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{
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usage: 3,
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selector: 1,
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matchingType: 1,
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certificate: Buffer
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}
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```
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#### `TXT`
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``` js
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{
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data: 'text' || Buffer || [ Buffer || 'text' ]
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}
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```
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When encoding, scalar values are converted to an array and strings are converted to UTF-8 encoded Buffers. When decoding, the return value will always be an array of Buffer.
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If you need another record type, open an issue and we'll try to add it.
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## License
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MIT
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