implement a bunch of utility functions on tun device primitive

lib/p2p_chat.ex

@@ -1,7 +1,7 @@
 defmodule P2pChat do
   def hello do
     {:ok, pid1} = P2pChat.Transport.start_link(port: 12345)
-    netid1 = P2pChat.Transport.get_netid(pid1)
+    _netid1 = P2pChat.Transport.get_netid(pid1)
 
     {:ok, pid2} = P2pChat.Transport.start_link(port: 12346)
     netid2 = P2pChat.Transport.get_netid(pid2)

lib/p2p_chat/transport/gen_tun.ex

@@ -1,6 +1,6 @@
 defmodule P2pChat.Transport.GenTun do
   require Logger
-  use Rustler, otp_app: :p2p_chat, crate: "p2pchat_transport_gen_tun"
+  require P2pChat.Transport.PrimTun, as: PrimTun
 
   @behaviour GenServer
 
@@ -10,15 +10,15 @@ defmodule P2pChat.Transport.GenTun do
   # Server API
   # 
   @impl true
-  def init(args) do
-    {:ok, tun_handle} = make_tun_device()
+  def init(_args) do
+    {:ok, tun_handle} = PrimTun.make_tun_device(true)
     state = %__MODULE__{tun_handle: tun_handle}
     { :ok, state, { :continue, :recv } }
   end
 
   @impl true
   def handle_continue(:recv, state) do
-    case tun_recv(state.tun_handle) do
+    case PrimTun.tun_recv(state.tun_handle, 2**16) do
        {:ok, buf} ->
          Logger.debug("Received #{byte_size(buf)} bytes")
        {:error, :would_block} -> {}
@@ -26,13 +26,13 @@ defmodule P2pChat.Transport.GenTun do
          Logger.error("Error during receive: #{e}")
     end
     
-    {:noreply, state, { :continue, :recv }}
+    {:noreply, state}
   end
 
   @impl true
-  def handle_call({:recv}, _from, state) do
-    data = tun_recv(state.tun_handle)
-    { :reply, data, state }
+  def handle_call({:get_addrs}, _from, state) do
+    result = PrimTun.get_addrs(state.tun_handle)
+    {:reply, result, state}
   end
 
   #
@@ -40,13 +40,10 @@ defmodule P2pChat.Transport.GenTun do
   # 
   def open() do
     GenServer.start_link(__MODULE__, nil)
-  end  
+  end
 
-  #
-  # NIFs
-  # 
-
-  defp make_tun_device(), do: :erlang.nif_error(:nif_not_loaded)
-  defp tun_recv(_handle, _bufsize \\ 2*16), do: :erlang.nif_error(:nif_not_loaded)
+  def get_addrs(pid) do
+    GenServer.call(pid, {:get_addrs})
+  end
 end
 

lib/p2p_chat/transport/prim_tun.ex

@@ -0,0 +1,17 @@
+defmodule P2pChat.Transport.PrimTun do
+  use Rustler, otp_app: :p2p_chat, crate: "p2pchat_transport_prim_tun"
+
+  def make_tun_device(_packet_info), do: :erlang.nif_error(:nif_not_loaded)
+  def recv(_handle, _bufsize), do: :erlang.nif_error(:nif_not_loaded)
+  def send(_handle, _buf), do: :erlang.nif_error(:nif_not_loaded)
+  def get_addrs(_handle), do: :erlang.nif_error(:nif_not_loaded)
+  def get_broadcast(_handle), do: :erlang.nif_error(:nif_not_loaded)
+  def get_name(_handle), do: :erlang.nif_error(:nif_not_loaded)
+  def set_name(_handle, _name), do: :erlang.nif_error(:nif_not_loaded)
+  def is_running(_handle), do: :erlang.nif_error(:nif_not_loaded)
+  def set_running(_handle, _should_run), do: :erlang.nif_error(:nif_not_loaded)
+  def add_address(_handle, _address, _prefix_length), do: :erlang.nif_error(:nif_not_loaded)
+  def remove_address(_handle, _address), do: :erlang.nif_error(:nif_not_loaded)
+  def get_mtu(_handle), do: :erlang.nif_error(:nif_not_loaded)
+  def set_mtu(_handle, _mtu), do: :erlang.nif_error(:nif_not_loaded)
+end