tuncer: persist interface on shutdown

If the caller has set the tuntap interface to persistent, do not destroy
or unconfigure the interface on shutdown as suggested by @alexshavelev
in #5

src/tuncer.erl

@@ -1,4 +1,4 @@
-%% Copyright (c) 2011-2016, Michael Santos <[email protected]>
+%% Copyright (c) 2011-2017, Michael Santos <[email protected]>
 %% All rights reserved.
 %%
 %% Redistribution and use in source and binary forms, with or without
@@ -64,7 +64,8 @@
  pid, % PID of controlling process
  fd, % TUN/TAP file descriptor
  dev, % device name
- flag % TUNSETIFF ifr flags
+ flag, % TUNSETIFF ifr flags
+ persist
  }).
 
 -define(IFNAMSIZ, 16).
@@ -254,7 +255,7 @@ handle_call({recv, _Len}, _From, State) ->
 
 handle_call({persist, Status}, _From, #state{fd = FD} = State) ->
  Reply = tunctl:persist(FD, Status),
- {reply, Reply, State};
+ {reply, Reply, State#state{persist = Status}};
 
 handle_call({owner, Owner}, _From, #state{fd = FD} = State) ->
  Reply = tunctl:owner(FD, Owner),
@@ -290,10 +291,15 @@ handle_info({'EXIT',_,normal}, State) ->
 handle_info({'EXIT', _, _}, #state{port = false} = State) ->
  {noreply, State};
 
-handle_info({'EXIT', Port, Error}, #state{port = Port, pid = Pid, fd = FD, dev = Dev} = State) ->
+handle_info({'EXIT', Port, Error}, #state{port = Port, pid = Pid, fd = FD, dev = Dev, persist = Persist} = State) ->
  Pid ! {tuntap_error, self(), Error},
- _ = tunctl:down(Dev),
- tunctl:persist(FD, false),
+ case Persist of
+ true ->
+ ok;
+ false ->
+ _ = tunctl:down(Dev),
+ tunctl:persist(FD, false)
+ end,
  procket:close(FD),
  {stop, normal, State};