ssl: Improve close handling

We want to make sure that the sender process that may get stuck in
prim_inet:send will die if the tls_connection process is
terminated.  And we also like to make sure that it terminates as
gracefully as possible. So when the tls_connection process dies it
spawns a killer process that will brutaly kill the sender if it is
unresponsive and does not terminate due to its monitor of the
tls_connetion process triggering.

When the sender process also acts as distribution controller it
may also have other processess that it is linked with that it
should bring down or that could bring the connection down.

1 files changed, 43 insertions, 7 deletions

diff --git a/lib/ssl/src/tls_sender.erl b/lib/ssl/src/tls_sender.erl
index 2746d89048..007fd345dd 100644
--- a/lib/ssl/src/tls_sender.erl
+++ b/lib/ssl/src/tls_sender.erl
@@ -25,6 +25,7 @@
 -include("ssl_internal.hrl").
 -include("ssl_alert.hrl").
 -include("ssl_handshake.hrl").
+-include("ssl_api.hrl").
 
 %% API
 -export([start/0, start/1, initialize/2, send_data/2, send_alert/2, renegotiate/1,
@@ -32,7 +33,7 @@
 
 %% gen_statem callbacks
 -export([callback_mode/0, init/1, terminate/3, code_change/4]).
--export([init/3, connection/3, handshake/3]).
+-export([init/3, connection/3, handshake/3, death_row/3]).
 
 -define(SERVER, ?MODULE).
 
@@ -53,6 +54,7 @@
 %%%===================================================================
 %%% API
 %%%===================================================================
+%%--------------------------------------------------------------------
 -spec start() -> {ok, Pid :: pid()} |
                  ignore |
                  {error, Error :: term()}.
@@ -65,7 +67,7 @@
 %%  same process is sending and receiving 
 %%--------------------------------------------------------------------
 start() ->
-    gen_statem:start(?MODULE, [], []).
+    gen_statem:start_link(?MODULE, [], []).
 start(SpawnOpts) ->
     gen_statem:start_link(?MODULE, [], SpawnOpts).
 
@@ -77,10 +79,19 @@ start(SpawnOpts) ->
 initialize(Pid, InitMsg) ->
     gen_statem:call(Pid, {self(), InitMsg}).
 
+%%--------------------------------------------------------------------
+-spec send_data(pid(), iodata()) -> ok. 
+%%  Description: Send application data
+%%--------------------------------------------------------------------
 send_data(Pid, AppData) ->
     %% Needs error handling for external API
     call(Pid, {application_data, AppData}).
 
+%%--------------------------------------------------------------------
+-spec send_alert(pid(), #alert{}) -> _. 
+%% Description: TLS connection process wants to end an Alert
+%% in the connection state.
+%%--------------------------------------------------------------------
 send_alert(Pid, Alert) ->
     gen_statem:cast(Pid, Alert).
 
@@ -99,10 +110,16 @@ renegotiate(Pid) ->
 %%--------------------------------------------------------------------
 update_connection_state(Pid, NewState, Version) ->
     gen_statem:cast(Pid, {new_write, NewState, Version}).
-
+%%--------------------------------------------------------------------
+-spec dist_handshake_complete(pid(), node(), term()) -> ok. 
+%%  Description: Erlang distribution callback 
+%%--------------------------------------------------------------------
 dist_handshake_complete(ConnectionPid, Node, DHandle) ->
     gen_statem:call(ConnectionPid, {dist_handshake_complete, Node, DHandle}).
-
+%%--------------------------------------------------------------------
+-spec dist_tls_socket(pid()) -> {ok, #sslsocket{}}. 
+%%  Description: To enable distribution startup to get a proper "#sslsocket{}" 
+%%--------------------------------------------------------------------
 dist_tls_socket(Pid) ->
     gen_statem:call(Pid, dist_get_tls_socket).
 
@@ -120,6 +137,9 @@ callback_mode() ->
                   gen_statem:init_result(atom()).
 %%--------------------------------------------------------------------
 init(_) ->
+    %% Note: Should not trap exits so that this process
+    %% will be terminated if tls_connection process is
+    %% killed brutally
     {ok, init, #data{}}.
 
 %%--------------------------------------------------------------------
@@ -233,6 +253,18 @@ handshake(info, Msg, StateData) ->
     handle_info(Msg, ?FUNCTION_NAME, StateData).
 
 %%--------------------------------------------------------------------
+-spec death_row(gen_statem:event_type(),
+                Msg :: term(),
+                StateData :: term()) ->
+                       gen_statem:event_handler_result(atom()).
+%%--------------------------------------------------------------------
+death_row(state_timeout, Reason, _State) ->
+    {stop, {shutdown, Reason}};
+death_row(_Type, _Msg, _State) ->
+    %% Waste all other events
+    keep_state_and_data.
+
+%%--------------------------------------------------------------------
 -spec terminate(Reason :: term(), State :: term(), Data :: term()) ->
                        any().
 %%--------------------------------------------------------------------
@@ -254,8 +286,12 @@ code_change(_OldVsn, State, Data, _Extra) ->
 %%% Internal functions
 %%%===================================================================
 handle_info({'DOWN', Monitor, _, _, Reason}, _, 
+            #data{connection_monitor = Monitor,
+                  dist_handle = Handle} = StateData) when Handle =/= undefined->
+    {next_state, death_row, StateData, [{state_timeout, 5000, Reason}]};
+handle_info({'DOWN', Monitor, _, _, _}, _, 
             #data{connection_monitor = Monitor} = StateData) ->
-    {stop, {shutdown, Reason}, StateData};
+    {stop, normal, StateData};
 handle_info(_,_,_) ->
     {keep_state_and_data}.
 
@@ -290,8 +326,8 @@ send_application_data(Data, From, StateName,
 	    case Connection:send(Transport, Socket, Msgs) of
                 ok when DistHandle =/=  undefined ->
                     {next_state, StateName, StateData, []};
-                Error when DistHandle =/= undefined ->
-                    ssl_connection:stop({shutdown, Error}, StateData);
+                Reason when DistHandle =/= undefined ->
+                    {next_state, death_row, StateData, [{state_timeout, 5000, Reason}]};
                 ok ->
                     {next_state, StateName, StateData,  [{reply, From, ok}]};
                 Result ->