Fix ignored connect timer

There are two timers governing the establishment of peer connections:
connect_timer and watchdog_timer. The former is the RFC 6733 Tc timer
and is used by diameter_service to establish an initial connection. The
latter is RFC 3539 TwInit and is used by diameter_watchdog for
connection reestablishment after the watchdog leaves state INITIAL. A
connecting transport ignored the connect timer since the watchdog
process never died, regardless of the watchdog state, causing the
watchdog timer to handle reconnection.

This seems to have been broken for some time.

1 files changed, 17 insertions, 19 deletions

diff --git a/lib/diameter/src/base/diameter_watchdog.erl b/lib/diameter/src/base/diameter_watchdog.erl
index eff5096745..b7f2d24941 100644
--- a/lib/diameter/src/base/diameter_watchdog.erl
+++ b/lib/diameter/src/base/diameter_watchdog.erl
@@ -255,11 +255,15 @@ close({'DOWN', _, process, TPid, {shutdown, Reason}},
 close(_, _) ->
     ok.
 
-event(_, #watchdog{status = T}, #watchdog{status = T}) ->
-    ok;
-
-event(_, #watchdog{transport = undefined}, #watchdog{transport = undefined}) ->
+event(_,
+      #watchdog{status = From, transport = F},
+      #watchdog{status = To, transport = T})
+  when F == undefined, T == undefined;  %% transport not started
+       From == initial, To == down;     %% never really left INITIAL
+       From == To ->                    %% no state transition
     ok;
+%% Note that there is no INITIAL -> DOWN transition in RFC 3539: ours
+%% is just a consequence of stop.
 
 event(Msg,
       #watchdog{status = From, transport = F, parent = Pid},
@@ -411,7 +415,7 @@ transition({'DOWN', _, process, TPid, _Reason},
     stop;
 
 %% ... or not.
-transition({'DOWN', _, process, TPid, _Reason},
+transition({'DOWN', _, process, TPid, _Reason} = D,
            #watchdog{transport = TPid,
                      status = T,
                      restrict = {_,R}}
@@ -422,20 +426,14 @@ transition({'DOWN', _, process, TPid, _Reason},
 
     %% Close an accepting watchdog immediately if there's no
     %% restriction on the number of connections to the same peer: the
-    %% state machine never enters state REOPEN in this case. The
-    %% 'close' message (instead of stop) is so as not to bypass the
-    %% sending of messages to the service process in handle_info/2.
-
-    if T /= initial, M == accept, not R ->
-            send(self(), close),
-            S#watchdog{status = down};
-       T /= initial ->
-            set_watchdog(S#watchdog{status = down});
-       M == connect ->
-            set_watchdog(S);
-       M == accept ->
-            send(self(), close),
-            S
+    %% state machine never enters state REOPEN in this case.
+
+    if T == initial;
+       M == accept, not R ->
+            close(D, S0),
+            stop;
+       true ->
+            set_watchdog(S#watchdog{status = down})
     end;
 
 %% Incoming message.