implement minimal NIF to create and read from a TUN device

lib/p2p_chat/transport/tuntap.ex

@@ -0,0 +1,33 @@
+defmodule P2pChat.Transport.TunTap do
+  use GenServer
+
+  defstruct [:tun_fd]
+
+  @impl true
+  def init(args) do
+    {:ok, io_device} = setup_tap_device()
+    {:ok, {}}
+  end
+
+  @impl true
+  def terminate(_reason, state) do
+    
+  end
+
+  def setup_tap_device(name \\ "tunP2P") do
+    {:ok, io_device} = :file.open(~c"/dev/net/tun", [:read, :write, :raw])
+    :ok = :file.close(io_device)
+    :ok
+  end
+
+  def teardown_tap_device(io_device) do
+  end
+
+  #
+  # Client API
+  # 
+  
+  def start_link(args) do
+    GenServer.start_link(__MODULE__, args)
+  end
+end

lib/p2p_chat/transport/tuntapport.ex

@@ -0,0 +1,8 @@
+defmodule P2pChat.Transport.TunTapPort do
+  use Rustler, otp_app: :p2p_chat, crate: "p2pchat_transport_tuntapport"
+
+  def make_tun_device(), do: :erlang.nif_error(:nif_not_loaded)
+
+  def read(_handle, _length \\ 2**16), do: :erlang.nif_error(:nif_not_loaded)
+end
+