Standard library · Network

net/dns

Finding the address of a name and asking for any kind of DNS record.

import net.dns

On this page

Types
Constants and variables
Functions

DNS turns names such as salamlang.ir into IP addresses. Lookup is the simplest way and does what a browser does. The Lookup... functions ask the DNS server for one particular kind of record and are what you want for building network tools or checking the configuration of a domain.

Types

`Question`

struct Question

One question.

Name	Type	Description
`name`	`str = ""`	The domain name.
`qtype`	`int = 0`	The record type.
`qclass`	`int = 0`	The class.

net-dns-Message.salam

import net.dns
import compress

func main:
    query := dns.EncodeQuery("salamlang.ir", dns.TypeA, 42)
    println compress.BufLen(query), compress.BufToBase64(query)
    m := dns.Decode(query.data, query.len)
    println m.id, m.qr, m.rd, m.opcode, m.rcode, m.questions.items.len()
    q := m.questions.items[0]
    println q.name, q.qtype == dns.TypeA, q.qclass == dns.ClassIN
    println m.answers.items.len(), m.authorities.items.len(), m.extras.items.len(), m.aa, m.tc, m.ra
    println dns.TypeNS, dns.TypeCNAME, dns.TypeSOA, dns.TypePTR, dns.TypeMX, dns.TypeTXT, dns.TypeAAAA
    println dns.Lookup("localhost")
    println dns.DefaultServers().len() > 0
end

Output30 ACoBAAABAAAAAAAACXNhbGFtbGFuZwJpcgAAAQAB 42 false true 0 0 1 salamlang.ir true true 0 0 0 false false false 2 5 6 12 15 16 28 127.0.0.1 true

`Questions`

struct Questions

A list of questions.

Name	Type	Description
`items`	`Vector`	The questions.

The example for this item is shown with the ones above: net-dns-Message.salam

`Record`

struct Record

One answer record.

Name	Type	Description
`name`	`str = ""`	The domain name.
`rtype`	`int = 0`	The record type.
`rclass`	`int = 0`	The class.
`ttl`	`int = 0`	How many seconds the answer may be kept.
`priority`	`int = 0`	The priority of an MX record; a smaller number means a higher priority.
`data`	`str = ""`	The record data as text: an address, a name or some text.

net-dns-Lookup.salam

import net.dns

func main:
    println dns.LookupA("salamlang.ir")
    println dns.LookupAAAA("salamlang.ir")
    println dns.LookupCNAME("www.github.com")
    mx := dns.LookupMX("gmail.com")
    each m in mx.items:
        println m.priority, m.data, m.ttl, m.rtype, m.rclass, m.name
    end
    println dns.LookupTXT("salamlang.ir")
    println dns.LookupPTR("8.8.8.8")
    answer := dns.QueryServer("1.1.1.1", "salamlang.ir", dns.TypeA, 2000)
    println answer.answers.items.len()
end

`Records`

struct Records

A list of records.

Name	Type	Description
`items`	`Vector`	The records.

The example for this item is shown with the ones above: net-dns-Lookup.salam

`Message`

struct Message

One DNS message, a question or an answer.

Name	Type	Description
`id`	`int = 0`	The id that ties an answer to its question.
`qr`	`bool = false`	The message is an answer.
`opcode`	`int = 0`	The kind of operation; zero is an ordinary question.
`aa`	`bool = false`	The answer comes from the authoritative server.
`tc`	`bool = false`	The answer was truncated.
`rd`	`bool = false`	A recursive lookup was asked for.
`ra`	`bool = false`	The server supports recursive lookups.
`rcode`	`int = 0`	The result code; zero means no error, 3 means the name does not exist.
`questions`	`Questions`	The questions.
`answers`	`Records`	The answers.
`authorities`	`Records`	The authority records.
`extras`	`Records`	The additional records.

The example for this item is shown with the ones above: net-dns-Message.salam

Constants and variables

`TypeA`

const TypeA: i32 = 1

An IPv4 address record.

The example for this item is shown with the ones above: net-dns-Message.salam

`TypeNS`

const TypeNS: i32 = 2

A name server of the domain.

The example for this item is shown with the ones above: net-dns-Message.salam

`TypeCNAME`

const TypeCNAME: i32 = 5

An alias.

The example for this item is shown with the ones above: net-dns-Message.salam

`TypeSOA`

const TypeSOA: i32 = 6

The start of authority of the domain.

The example for this item is shown with the ones above: net-dns-Message.salam

`TypePTR`

const TypePTR: i32 = 12

The name for an address (a reverse lookup).

The example for this item is shown with the ones above: net-dns-Message.salam

`TypeMX`

const TypeMX: i32 = 15

A mail server.

The example for this item is shown with the ones above: net-dns-Message.salam

`TypeTXT`

const TypeTXT: i32 = 16

Free text, such as SPF records.

The example for this item is shown with the ones above: net-dns-Message.salam

`TypeAAAA`

const TypeAAAA: i32 = 28

An IPv6 address record.

The example for this item is shown with the ones above: net-dns-Message.salam

`ClassIN`

const ClassIN: i32 = 1

The internet class; nearly always this one.

The example for this item is shown with the ones above: net-dns-Message.salam

Functions

`EncodeQuery`

func EncodeQuery(name: str, qtype: int, id: int): compress.ByteBuf

Builds a DNS question message to send over UDP.

The example for this item is shown with the ones above: net-dns-Message.salam

`Decode`

func Decode(data: void*, n: int): Message

Reads a DNS message from bytes.

The example for this item is shown with the ones above: net-dns-Message.salam

`Lookup`

func Lookup(host: str): str

Finds the address of a host name using the operating system settings; the hosts file is read too.

The example for this item is shown with the ones above: net-dns-Message.salam

`QueryServer`

func QueryServer(server: str, name: str, qtype: int, timeout_ms: int): Message

Asks the given server directly and returns the answer message.

The example for this item is shown with the ones above: net-dns-Lookup.salam

`DefaultServers`

func DefaultServers(): Vector<str>

The system DNS servers, from the network configuration.

The example for this item is shown with the ones above: net-dns-Message.salam

`LookupA`

func LookupA(name: str): Vector<str>

The IPv4 addresses of a name.

The example for this item is shown with the ones above: net-dns-Lookup.salam

`LookupAAAA`

func LookupAAAA(name: str): Vector<str>

The IPv6 addresses of a name.

The example for this item is shown with the ones above: net-dns-Lookup.salam

`LookupCNAME`

func LookupCNAME(name: str): str

The real name behind an alias.

The example for this item is shown with the ones above: net-dns-Lookup.salam

`LookupMX`

func LookupMX(name: str): Records

The mail servers of a domain, with their priority.

The example for this item is shown with the ones above: net-dns-Lookup.salam

`LookupTXT`

func LookupTXT(name: str): Vector<str>

The text records of a domain.

The example for this item is shown with the ones above: net-dns-Lookup.salam

`LookupPTR`

func LookupPTR(ip: str): Vector<str>

The names of an IP address.

The example for this item is shown with the ones above: net-dns-Lookup.salam