elixir-dns's Introduction

DNS

DNS library for Elixir. Currently, the package provides:

Elixir structs to interface with inet_dns module.
DNS.Server behavior
DNS client

Note: the inet_dns module is considered internal to Erlang and subject to change. If this happened this library will be updated to accommodate for that, but for now inet_dns is simple and worked for me.

Installation

The package is available in Hex and can be installed as:

Add dns to your list of dependencies in mix.exs:

def deps do [{:dns, "~> 0.0.3"}] end
Ensure dns is started before your application:

def application do [applications: [:dns]] end

Usage

DNS client

iex> DNS.resolve("google.com")
{216, 58, 221, 110}

iex> DNS.query("google.com")
%DNS.Record{anlist: [%DNS.Resource{bm: [], class: :in, cnt: 0,
   data: {216, 58, 221, 110}, domain: 'google.com', func: false, tm: :undefined,
   ttl: 129, type: :a}], arlist: [],
 header: %DNS.Header{aa: false, id: 0, opcode: :query, pr: false, qr: true,
  ra: true, rcode: 0, rd: false, tc: false}, nslist: [],
 qdlist: [%DNS.Query{class: :in, domain: 'google.com', type: :a}]}

iex> DNS.resolve("google.com", {"8.8.8.8", 53})
...

DNS server

defmodule TestServer do
  use Application

  @behaviour DNS.Server

  def start(_args, _opts) do
    import Supervisor.Spec, warn: false

    port = Application.get_env(:dns, :server)[:port]
    children = [
      worker(Task, [DNS.Server, :accept, [port, __MODULE__]])
    ]

    opts = [strategy: :one_for_one, name: DNS.Server.Supervisor]
    Supervisor.start_link(children, opts)
  end

  def handle(record, {ip, _}) do
    query = hd(record.qdlist)

    resource = %DNS.Resource{
      domain: query.domain,
      class: query.class,
      type: query.type,
      ttl: 0,
      data: {127, 0, 0, 1}
    }

    %{record | anlist: [resource]}
  end
end