# 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](https://hex.pm) and can be installed as:

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

        def deps do
          [{:dns, "~> 0.0.3"}]
        end

  2. Ensure dns is started before your application:

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

## Usage

### DNS client

```elixir
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

```elixir
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
```

For more information, see [API Reference](http://hexdocs.pm/dns/0.0.3/api-reference.html)

## License

BSD-3-Clauses