Merge branch 'anders/diameter/reopen/OTP-10692'

* anders/diameter/reopen/OTP-10692:
  Fix testcases in event suite
  Fix faulty watchdog transition INITIAL -> DOWN
  Fix faulty watchdog transition DOWN -> INITIAL
  Comment fixes
  Rename records peer/conn -> watchdog/peer in diameter_service
  Add testcases to traffic suite
  Simplify watchdog transitions in service process
  Simplify transport shutdown
  Remove upgrade code not needed after application restart
  Tweak (make) silent rules support

6 files changed, 397 insertions, 515 deletions

diff --git a/lib/diameter/src/Makefile b/lib/diameter/src/Makefile
index a08c204a23..2b02f1de2b 100644
--- a/lib/diameter/src/Makefile
+++ b/lib/diameter/src/Makefile
@@ -119,7 +119,8 @@ ERL_COMPILE_FLAGS += \
 
 # erl/hrl from dictionary file.
 gen/diameter_gen_%.erl gen/diameter_gen_%.hrl: dict/%.dia
-	$(dia_verbose)../bin/diameterc -o gen -i $(EBIN) $<
+	$(dia_verbose) \
+	../bin/diameterc -o gen -i $(EBIN) $<
 
 opt: $(TARGET_FILES)
 
@@ -134,11 +135,13 @@ debug:
 
 # The dictionary parser.
 gen/$(DICT_YRL).erl: compiler/$(DICT_YRL).yrl
-	$(yecc_verbose)$(ERLC) -Werror -o $(@D) $<
+	$(yecc_verbose) \
+	$(ERLC) -Werror -o $(@D) $<
 
 # Generate the app file.
 $(APP_TARGET): $(APP_SRC) ../vsn.mk modules.mk
-	$(gen_verbose)M=`echo $(notdir $(APP_MODULES)) | tr ' ' ,`; \
+	$(gen_verbose) \
+	M=`echo $(notdir $(APP_MODULES)) | tr ' ' ,`; \
 	R=`echo $(REGISTERED) | tr ' ' ,`; \
 	sed -e 's;%VSN%;$(VSN);' \
 	    -e "s;%MODULES%;$$M;" \
@@ -146,7 +149,8 @@ $(APP_TARGET): $(APP_SRC) ../vsn.mk modules.mk
 	  $< > $@
 
 $(APPUP_TARGET): $(APPUP_SRC) ../vsn.mk
-	$(vsn_verbose)sed -e 's;%VSN%;$(VSN);' $< > $@
+	$(vsn_verbose) \
+	sed -e 's;%VSN%;$(VSN);' $< > $@
 
 app:  $(APP_TARGET) $(APPUP_TARGET)
 dict: $(DICT_ERLS)
@@ -262,7 +266,7 @@ depend: depend.mk
 
 # Generate dependencies makefile.
 depend.mk: depend.sed $(MODULES:%=%.erl) Makefile
-	$(gen_verbose)(for f in $(MODULES); do \
+	(for f in $(MODULES); do \
 	     (echo $$f; cat $$f.erl) | sed -f $<; \
 	 done) \
 	> $@
diff --git a/lib/diameter/src/base/diameter_peer_fsm.erl b/lib/diameter/src/base/diameter_peer_fsm.erl
index 5dab6214b1..de341741db 100644
--- a/lib/diameter/src/base/diameter_peer_fsm.erl
+++ b/lib/diameter/src/base/diameter_peer_fsm.erl
@@ -126,24 +126,17 @@
 %% State Machine rather than closer to the transport. This is what we
 %% now do below: connect/accept call diameter_watchdog and return the
 %% pid of the watchdog process, and the watchdog in turn calls start/3
-%% below to start the process implementing the Peer State Machine. The
-%% former is a "peer" in diameter_service while the latter is a
-%% "conn". In a sense, diameter_service sees the watchdog as
-%% implementing the Peer State Machine and the process implemented
-%% here as being the transport, not being aware of the watchdog at
-%% all.
+%% below to start the process implementing the Peer State Machine.
 %%
 
-%%% ---------------------------------------------------------------------------
-%%% # start({connect|accept, Ref}, Opts, Service)
-%%%
-%%% Output: Pid
-%%% ---------------------------------------------------------------------------
+%% ---------------------------------------------------------------------------
+%% # start/3
+%% ---------------------------------------------------------------------------
 
 -spec start(T, [Opt], {diameter:sequence(),
                        diameter:restriction(),
                        #diameter_service{}})
-   -> pid()
+   -> {reference(), pid()}
  when T   :: {connect|accept, diameter:transport_ref()},
       Opt :: diameter:transport_opt().
 
@@ -152,9 +145,15 @@
 %% specified on the transport in question. Check here that the list is
 %% still non-empty.
 
-start({_,_} = Type, Opts, MS) ->
-    {ok, Pid} = diameter_peer_fsm_sup:start_child({self(), Type, Opts, MS}),
-    Pid.
+start({_,_} = Type, Opts, S) ->
+    Ack = make_ref(),
+    T = {Ack, self(), Type, Opts, S},
+    {ok, Pid} = diameter_peer_fsm_sup:start_child(T),
+    try
+        {erlang:monitor(process, Pid), Pid}
+    after
+        Pid ! Ack
+    end.
 
 start_link(T) ->
     {ok, _} = proc_lib:start_link(?MODULE,
@@ -163,8 +162,8 @@ start_link(T) ->
                                   infinity,
                                   diameter_lib:spawn_opts(server, [])).
 
-%%% ---------------------------------------------------------------------------
-%%% ---------------------------------------------------------------------------
+%% ---------------------------------------------------------------------------
+%% ---------------------------------------------------------------------------
 
 %% init/1
 
@@ -172,12 +171,13 @@ init(T) ->
     proc_lib:init_ack({ok, self()}),
     gen_server:enter_loop(?MODULE, [], i(T)).
 
-i({WPid, T, Opts, {Mask, Nodes, #diameter_service{applications = Apps,
-                                                  capabilities = LCaps}
-                                = Svc}}) ->
-    [] /= Apps orelse ?ERROR({no_apps, T, Opts}),
+i({Ack, WPid, {M, Ref} = T, Opts, {Mask,
+                                   Nodes,
+                                   #diameter_service{capabilities = LCaps}
+                                   = Svc}}) ->
+    erlang:monitor(process, WPid),
+    wait(Ack, WPid),
     putr(?DWA_KEY, dwa(LCaps)),
-    {M, Ref} = T,
     diameter_stats:reg(Ref),
     {[Cs,Ds], Rest} = proplists:split(Opts, [capabilities_cb, disconnect_cb]),
     putr(?CB_KEY, {Ref, [F || {_,F} <- Cs]}),
@@ -185,7 +185,6 @@ i({WPid, T, Opts, {Mask, Nodes, #diameter_service{applications = Apps,
     putr(?REF_KEY, Ref),
     putr(?SEQUENCE_KEY, Mask),
     putr(?RESTRICT_KEY, Nodes),
-    erlang:monitor(process, WPid),
     {TPid, Addrs} = start_transport(T, Rest, Svc),
     Tmo = proplists:get_value(capx_timeout, Opts, ?EVENT_TIMEOUT),
     ?IS_TIMEOUT(Tmo) orelse ?ERROR({invalid, {capx_timeout, Tmo}}),
@@ -203,6 +202,16 @@ i({WPid, T, Opts, {Mask, Nodes, #diameter_service{applications = Apps,
 %% watchdog start (start/2) succeeds regardless so as not to crash the
 %% service.
 
+%% Wait for the caller to have a monitor to avoid a race with our
+%% death. (Since the exit reason is used in diameter_service.)
+wait(Ref, Pid) ->
+    receive
+        Ref ->
+            ok;
+        {'DOWN', _, process, Pid, _} = D ->
+            exit({shutdown, D})
+    end.
+
 start_transport(T, Opts, #diameter_service{capabilities = LCaps} = Svc) ->
     Addrs0 = LCaps#diameter_caps.host_ip_address,
     start_transport(Addrs0, {T, Opts, Svc}).
@@ -274,13 +283,12 @@ handle_info(T, #state{} = State) ->
             {noreply, S};
         {stop, Reason} ->
             ?LOG(stop, Reason),
-            x(Reason, State);
+            {stop, {shutdown, Reason}, State};
         stop ->
             ?LOG(stop, T),
-            x(T, State)
+            {stop, {shutdown, T}, State}
     catch
         exit: {diameter_codec, encode, _} = Reason ->
-            close_wd(Reason, State#state.parent),
             ?LOG(stop, Reason),
             %% diameter_codec:encode/2 emits an error report. Only
             %% indicate the probable reason here.
@@ -300,10 +308,6 @@ handle_info(T, #state{} = State) ->
 %% succesfully encoded. It's not checked at diameter:add_transport/2
 %% since this can be called before creating the service.
 
-x(Reason, #state{} = S) ->
-    close_wd(Reason, S),
-    {stop, {shutdown, Reason}, S}.
-
 %% terminate/2
 
 terminate(_, _) ->
@@ -314,8 +318,8 @@ terminate(_, _) ->
 code_change(_, State, _) ->
     {ok, State}.
 
-%%% ---------------------------------------------------------------------------
-%%% ---------------------------------------------------------------------------
+%% ---------------------------------------------------------------------------
+%% ---------------------------------------------------------------------------
 
 putr(Key, Val) ->
     put({?MODULE, Key}, Val).
@@ -378,9 +382,8 @@ transition({diameter, {recv, Pkt}}, S) ->
     recv(Pkt, S);
 
 %% Timeout when still in the same state ...
-transition({timeout = T, PS}, #state{state = PS} = S) ->
-    close({capx(PS), T}, S),
-    stop;
+transition({timeout = T, PS}, #state{state = PS}) ->
+    {stop, {capx(PS), T}};
 
 %% ... or not.
 transition({timeout, _}, _) ->
@@ -393,8 +396,6 @@ transition({send, Msg}, #state{transport = TPid}) ->
 
 %% Request for graceful shutdown at remove_transport, stop_service of
 %% application shutdown.
-transition({shutdown = T, Pid}, S) ->
-    transition({T, Pid, transport}, S);
 transition({shutdown, Pid, Reason}, #state{parent = Pid, dpr = false} = S) ->
     dpr(Reason, S);
 transition({shutdown, Pid, _}, #state{parent = Pid}) ->
@@ -459,7 +460,7 @@ send_CER(#state{state = {'Wait-Conn-Ack', Tmo},
     OH = LCaps#diameter_caps.origin_host,
     req_send_CER(OH, Remote)
         orelse
-        close({already_connected, Remote, LCaps}, S),
+        close({already_connected, Remote, LCaps}),
     CER = build_CER(S),
     ?LOG(send, 'CER'),
     #diameter_packet{header = #diameter_header{end_to_end_id = Eid,
@@ -692,17 +693,17 @@ cea(CEA, RC) ->
     CEA#diameter_base_CEA{'Result-Code' = RC}.
 
 post('CER' = T, RC, Pkt, S) ->
-    [fun close/2, {T, caps(S), {RC, Pkt}}];
+    [fun(_) -> close({T, caps(S), {RC, Pkt}}) end];
 post(_, _, _, _) ->
     ok.
 
 rejected({capabilities_cb, _F, Reason}, T, S) ->
     rejected(Reason, T, S);
 
-rejected(discard, T, S) ->
-    close(T, S);
+rejected(discard, T, _) ->
+    close(T);
 rejected({N, Es}, T, S) ->
-    {answer('CER', N, Es, S), [fun close/2, T]};
+    {answer('CER', N, Es, S), [fun(_) -> close(T) end]};
 rejected(N, T, S) ->
     rejected({N, []}, T, S).
 
@@ -862,7 +863,7 @@ handle_CEA(#diameter_packet{bin = Bin}
     of
         _ -> open(DPkt, SApps, Caps, {connect, hd([_] = IS)}, S)
     catch
-        ?FAILURE(Reason) -> close({'CEA', Reason, Caps, DPkt}, S)
+        ?FAILURE(Reason) -> close({'CEA', Reason, Caps, DPkt})
     end.
 %% Check more than the result code since the peer could send success
 %% regardless. If not 2001 then a peer_up callback could do anything
@@ -882,7 +883,7 @@ recv_CEA(#diameter_packet{header = #diameter_header{version
     T;
 
 recv_CEA(Pkt, S) ->
-    close({'CEA', caps(S), Pkt}, S).
+    close({'CEA', caps(S), Pkt}).
 
 caps(#diameter_service{capabilities = Caps}) ->
     Caps;
@@ -935,14 +936,14 @@ open(Pkt, SupportedApps, Caps, {Type, IS}, #state{parent = Pid,
 
 %% We've advertised TLS support: tell the transport the result
 %% and expect a reply when the handshake is complete.
-tls_ack(true, Caps, Type, IS, #state{transport = TPid} = S) ->
+tls_ack(true, Caps, Type, IS, #state{transport = TPid}) ->
     Ref = make_ref(),
     TPid ! {diameter, {tls, Ref, Type, IS == ?TLS}},
     receive
         {diameter, {tls, Ref}} ->
             ok;
         {'DOWN', _, process, TPid, Reason} ->
-            close({tls_ack, Reason, Caps}, S)
+            close({tls_ack, Reason, Caps})
     end;
 
 %% Or not. Don't send anything to the transport so that transports
@@ -955,25 +956,11 @@ capz(#diameter_caps{} = L, #diameter_caps{} = R) ->
         = list_to_tuple([diameter_caps | lists:zip(tl(tuple_to_list(L)),
                                                    tl(tuple_to_list(R)))]).
 
-%% close/2
+%% close/1
 
-%% Tell the watchdog that our death isn't due to transport failure.
-close(Reason, #state{parent = Pid}) ->
-    close_wd(Reason, Pid),
+close(Reason) ->
     throw({?MODULE, close, Reason}).
 
-%% close_wd/2
-
-%% Ensure the watchdog dies if DPR has been sent ...
-close_wd(_, #state{dpr = false}) ->
-    ok;
-close_wd(Reason, #state{parent = Pid}) ->
-    close_wd(Reason, Pid);
-
-%% ... or otherwise
-close_wd(Reason, Pid) ->
-    Pid ! {close, self(), Reason}.
-
 %% dwa/1
 
 dwa(#diameter_caps{origin_host = OH,
diff --git a/lib/diameter/src/base/diameter_reg.erl b/lib/diameter/src/base/diameter_reg.erl
index 619b12ecad..ac58e4bf5b 100644
--- a/lib/diameter/src/base/diameter_reg.erl
+++ b/lib/diameter/src/base/diameter_reg.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 2010-2012. All Rights Reserved.
+%% Copyright Ericsson AB 2010-2013. All Rights Reserved.
 %%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -208,10 +208,6 @@ init(_) ->
 %% # handle_call/3
 %% ----------------------------------------------------------
 
-handle_call(Req, From, S)
-  when not is_record(S, state) ->
-    handle_call(Req, From, upgrade(S));
-
 handle_call({add, Fun, Key, Pid}, _, S) ->
     B = Fun(?TABLE, {Key, Pid}),
     monitor(B andalso no_monitor(Pid), Pid),
@@ -281,9 +277,6 @@ code_change(_OldVsn, State, _Extra) ->
 
 %% ===========================================================================
 
-upgrade(S) ->
-    #state{} = list_to_tuple(tuple_to_list(S) ++ [[]]).
-
 monitor(true, Pid) ->
     ets:insert(?TABLE, ?MONITOR(Pid, erlang:monitor(process, Pid)));
 monitor(false, _) ->
diff --git a/lib/diameter/src/base/diameter_service.erl b/lib/diameter/src/base/diameter_service.erl
index d2a416166f..3cab914fdb 100644
--- a/lib/diameter/src/base/diameter_service.erl
+++ b/lib/diameter/src/base/diameter_service.erl
@@ -64,15 +64,7 @@
 -include_lib("diameter/include/diameter.hrl").
 -include("diameter_internal.hrl").
 
-%% The states mirrored by peer_up/peer_down callbacks.
--define(STATE_UP,   up).
--define(STATE_DOWN, down).
-
--type op_state() :: ?STATE_UP
-                  | ?STATE_DOWN.
-
-%% The RFC 3539 watchdog states that are now maintained, albeit
-%% along with the old up/down. okay = up, else down.
+%% RFC 3539 watchdog states.
 -define(WD_INITIAL, initial).
 -define(WD_OKAY,    okay).
 -define(WD_SUSPECT, suspect).
@@ -122,8 +114,10 @@
         {id = now(),
          service_name,  %% as passed to start_service/2, key in ?STATE_TABLE
          service :: #diameter_service{},
-         peerT = ets_new(peers) :: ets:tid(),%% #peer{} at start_fsm
-         connT = ets_new(conns) :: ets:tid(),%% #conn{} at connection_up/reopen
+         watchdogT = ets_new(watchdogs) %% #watchdog{} at start
+                  :: ets:tid(),
+         peerT = ets_new(peers)         %% #peer{pid = TPid} at okay/reopen
+              :: ets:tid(),
          shared_peers = ?Dict:new(),         %% Alias -> [{TPid, Caps}, ...]
          local_peers = ?Dict:new(),          %% Alias -> [{TPid, Caps}, ...]
          monitor = false :: false | pid(),   %% process to die with
@@ -139,36 +133,26 @@
 %% service record is used to determine whether or not we need to call
 %% the process for a pick_peer callback.
 
-%% Record representing a watchdog process as implemented by
-%% diameter_watchdog. The term "peer" here is historical, made
-%% especially confusing by the fact that a peer_ref() in the
-%% documentation is the key of a #conn{} record, not a #peer{} record.
-%% The name is also unfortunate given the meaning of peer in the
-%% Diameter sense.
--record(peer,
+%% Record representing an RFC 3539 watchdog process implemented by
+%% diameter_watchdog.
+-record(watchdog,
         {pid  :: match(pid()),
          type :: match(connect | accept),
          ref  :: match(reference()),  %% key into diameter_config
          options :: match([diameter:transport_opt()]),%% from start_transport
-         op_state = {?STATE_DOWN, ?WD_INITIAL}
-                 :: match(op_state() | {op_state(), wd_state()}),
+         state = ?WD_INITIAL :: match(wd_state()),
          started = now(),      %% at process start
-         conn = false :: match(boolean() | pid())}).
-                      %% true at accepted, pid() at connection_up or reopen
-
-%% Record representing a peer process as implemented by
-%% diameter_peer_fsm. The term "conn" is historical. Despite the name
-%% here, comments refer to watchdog and peer processes, that are keys
-%% in #peer{} and #conn{} records respectively. To add to the
-%% confusion, a #request.transport is a peer process = key in a
-%% #conn{} record. The actual transport process (that the peer process
-%% knows about and that has a transport connection) isn't seen here.
--record(conn,
+         peer = false :: match(boolean() | pid())}).
+                      %% true at accepted, pid() at okay/reopen
+
+%% Record representing an Peer State Machine processes implemented by
+%% diameter_peer_fsm.
+-record(peer,
         {pid   :: pid(),
          apps  :: [{0..16#FFFFFFFF, diameter:app_alias()}], %% {Id, Alias}
          caps  :: #diameter_caps{},
          started = now(),  %% at process start
-         peer  :: pid()}). %% key into peerT
+         watchdog :: pid()}). %% key into watchdogT
 
 %% Record stored in diameter_request for each outgoing request.
 -record(request,
@@ -520,67 +504,39 @@ transition({accepted, Pid, TPid}, S) ->
     accepted(Pid, TPid, S),
     ok;
 
-%% Peer process has a new open connection.
-transition({connection_up, Pid, T}, S) ->
-    connection_up(Pid, T, S),
-    ok;
-
-%% Watchdog has a new connection that will be opened after DW[RA]
-%% exchange. This message was added long after connection_up, to
-%% communicate the information as soon as it's available. Leave
-%% connection_up as is it for now, duplicated information and all.
-transition({reopen, Pid, T}, S) ->
-    reopen(Pid, T, S),
-    ok;
-
-%% Watchdog has left state OKAY.
-transition({connection_down, Pid}, S) ->
-    connection_down(Pid, S),
-    ok;
-
-%% Watchdog has returned to state OKAY.
-transition({connection_up, Pid}, S) ->
-    connection_up(Pid, S),
-    ok;
-
-%% Accepting transport has lost connectivity.
-transition({close, Pid}, S) ->
-    close(Pid, S),
-    ok;
-
 %% Connecting transport is being restarted by watchdog.
 transition({reconnect, Pid}, S) ->
     reconnect(Pid, S),
     ok;
 
-%% Watchdog is sending notification of a state transition. Note that
-%% the connection_up/down messages pre-date this message and are still
-%% used. A watchdog message will follow these and communicate the same
-%% state as was set in handling connection_up/down.
-transition({watchdog, Pid, {TPid, From, To}}, #state{service_name = SvcName,
-                                                     peerT = PeerT}) ->
-    #peer{ref = Ref, type = T, options = Opts, op_state = {OS,_}}
-        = P
-        = fetch(PeerT, Pid),
-    insert(PeerT, P#peer{op_state = {OS, To}}),
+%% Watchdog is sending notification of transport death.
+transition({close, Pid, Reason}, #state{service_name = SvcName,
+                                        watchdogT = WatchdogT}) ->
+    #watchdog{state = WS,
+              ref = Ref,
+              type = Type,
+              options = Opts}
+        = fetch(WatchdogT, Pid),
+    WS /= ?WD_OKAY
+        andalso
+        send_event(SvcName, {closed, Ref, Reason, {type(Type), Opts}}),
+    ok;
+
+%% Watchdog is sending notification of a state transition.
+transition({watchdog, Pid, {[TPid | Data], From, To}},
+           #state{service_name = SvcName,
+                  watchdogT = WatchdogT}
+           = S) ->
+    #watchdog{ref = Ref, type = T, options = Opts}
+        = Wd
+        = fetch(WatchdogT, Pid),
+    watchdog(TPid, Data, From, To, Wd, S),
     send_event(SvcName, {watchdog, Ref, TPid, {From, To}, {T, Opts}}),
     ok;
-%% Death of a watchdog process (#peer.pid) results in the removal of
-%% it's peer and any associated conn record when 'DOWN' is received
-%% (after this) but the states will be {?STATE_UP, ?WD_DOWN} for a
-%% short time. (No real problem since ?WD_* is only used in
-%% service_info.) We set ?WD_OKAY as a consequence of connection_up
-%% since we know a watchdog is coming. We can't set anything at
-%% connection_down since we don't know if the subsequent watchdog
-%% message will be ?WD_DOWN or ?WD_SUSPECT. We don't (yet) set
-%% ?STATE_* as a consequence of a watchdog message since this requires
-%% changing some of the matching on ?STATE_*.
-%%
-%% Death of a peer process process (#conn.pid, #peer.conn) results in
-%% connection_down followed by watchdog ?WD_DOWN. The latter doesn't
-%% result in the conn record being deleted since 'DOWN' from death of
-%% its watchdog doesn't (yet) deal with the record having been
-%% removed.
+%% Death of a watchdog process (#watchdog.pid) results in the removal of
+%% it's peer and any associated conn record when 'DOWN' is received.
+%% Death of a peer process process (#peer.pid, #watchdog.peer) results in
+%% ?WD_DOWN.
 
 %% Monitor process has died. Just die with a reason that tells
 %% diameter_config about the happening. If a cleaner shutdown is
@@ -589,9 +545,9 @@ transition({'DOWN', MRef, process, _, Reason}, #state{monitor = MRef}) ->
     {stop, {monitor, Reason}};
 
 %% Local watchdog process has died.
-transition({'DOWN', _, process, Pid, Reason}, S)
+transition({'DOWN', _, process, Pid, _Reason}, S)
   when node(Pid) == node() ->
-    peer_down(Pid, Reason, S),
+    watchdog_down(Pid, S),
     ok;
 
 %% Remote service wants to know about shared peers.
@@ -716,49 +672,30 @@ mod_state(Alias, ModS) ->
 %%% # shutdown/2
 %%% ---------------------------------------------------------------------------
 
-%% remove_transport: ask watchdogs to terminate their transport.
-shutdown(Refs, #state{peerT = PeerT})
+%% remove_transport
+shutdown(Refs, #state{watchdogT = WatchdogT})
   when is_list(Refs) ->
-    ets:foldl(fun(P,ok) -> sp(P, Refs), ok end, ok, PeerT);
-
-%% application/service shutdown: ask transports to terminate themselves.
-shutdown(Reason, #state{peerT = PeerT}) ->
-    %% A transport might not be alive to receive the shutdown request
-    %% but give those that are a chance to shutdown gracefully.
-    shutdown(conn, Reason, PeerT),
-    %% Kill the watchdogs explicitly in case there was no transport.
-    shutdown(peer, Reason, PeerT).
-
-%% sp/2
-
-sp(#peer{ref = Ref, pid = Pid}, Refs) ->
-    lists:member(Ref, Refs)
-        andalso (Pid ! {shutdown, self()}).  %% 'DOWN' cleans up
+    ets:foldl(fun(P,ok) -> st(P, Refs), ok end, ok, WatchdogT);
 
-%% shutdown/3
-
-shutdown(Who, Reason, T) ->
-    diameter_lib:wait(ets:foldl(fun(X,A) -> shutdown(Who, X, Reason, A) end,
+%% application/service shutdown
+shutdown(Reason, #state{watchdogT = WatchdogT})
+  when Reason == application;
+       Reason == service ->
+    diameter_lib:wait(ets:foldl(fun(P,A) -> st(P, Reason, A) end,
                                 [],
-                                T)).
+                                WatchdogT)).
 
-shutdown(conn = Who, #peer{op_state = {OS,_}} = P, Reason, Acc) ->
-    shutdown(Who, P#peer{op_state = OS}, Reason, Acc);
+%% st/2
 
-shutdown(conn,
-         #peer{pid = Pid, op_state = ?STATE_UP, conn = TPid},
-         Reason,
-         Acc) ->
-    TPid ! {shutdown, Pid, Reason},
-    [TPid | Acc];
+st(#watchdog{ref = Ref, pid = Pid}, Refs) ->
+    lists:member(Ref, Refs)
+        andalso (Pid ! {shutdown, self(), transport}).  %% 'DOWN' cleans up
 
-shutdown(peer, #peer{pid = Pid}, _Reason, Acc)
-  when is_pid(Pid) ->
-    exit(Pid, shutdown),
-    [Pid | Acc];
+%% st/3
 
-shutdown(_, #peer{}, _, Acc) ->
-    Acc.
+st(#watchdog{pid = Pid}, Reason, Acc) ->
+    Pid ! {shutdown, self(), Reason},
+    [Pid | Acc].
 
 %%% ---------------------------------------------------------------------------
 %%% # call_service/2
@@ -787,8 +724,6 @@ cs(undefined, _) ->
 
 %%% ---------------------------------------------------------------------------
 %%% # i/1
-%%%
-%%% Output: #state{}
 %%% ---------------------------------------------------------------------------
 
 %% Intialize the state of a service gen_server.
@@ -891,22 +826,22 @@ type(connect = T) -> T.
 
 %% start/4
 
-start(Ref, Type, Opts, #state{peerT = PeerT,
-                              connT = ConnT,
+start(Ref, Type, Opts, #state{watchdogT = WatchdogT,
+                              peerT = PeerT,
                               options = SvcOpts,
                               service_name = SvcName,
                               service = Svc})
   when Type == connect;
        Type == accept ->
-    Pid = s(Type, Ref, {ConnT,
+    Pid = s(Type, Ref, {PeerT,
                         Opts,
                         SvcName,
                         SvcOpts,
                         merge_service(Opts, Svc)}),
-    insert(PeerT, #peer{pid = Pid,
-                        type = Type,
-                        ref = Ref,
-                        options = Opts}),
+    insert(WatchdogT, #watchdog{pid = Pid,
+                                type = Type,
+                                ref = Ref,
+                                options = Opts}),
     Pid.
 
 %% Note that the service record passed into the watchdog is the merged
@@ -953,23 +888,50 @@ ms(_, Svc) ->
 %%% # accepted/3
 %%% ---------------------------------------------------------------------------
 
-accepted(Pid, _TPid, #state{peerT = PeerT} = S) ->
-    #peer{ref = Ref, type = accept = T, conn = false, options = Opts}
-        = P
-        = fetch(PeerT, Pid),
-    insert(PeerT, P#peer{conn = true}),  %% mark replacement as started
-    start(Ref, T, Opts, S).              %% start new watchdog
+accepted(Pid, _TPid, #state{watchdogT = WatchdogT} = S) ->
+    #watchdog{ref = Ref, type = accept = T, peer = false, options = Opts}
+        = Wd
+        = fetch(WatchdogT, Pid),
+    insert(WatchdogT, Wd#watchdog{peer = true}),%% mark replacement as started
+    start(Ref, T, Opts, S).                     %% start new watchdog
 
 fetch(Tid, Key) ->
     [T] = ets:lookup(Tid, Key),
-    case T of
-        #peer{op_state = ?STATE_UP} = P ->
-            P#peer{op_state = {?STATE_UP, ?WD_OKAY}};
-        #peer{op_state = ?STATE_DOWN} = P ->
-            P#peer{op_state = {?STATE_DOWN, ?WD_DOWN}};
-        _ ->
-            T
-    end.
+    T.
+
+%%% ---------------------------------------------------------------------------
+%%% # watchdog/6
+%%%
+%%% React to a watchdog state transition.
+%%% ---------------------------------------------------------------------------
+
+%% Watchdog has a new open connection.
+watchdog(TPid, [T], _, ?WD_OKAY, Wd, State) ->
+    connection_up({TPid, T}, Wd, State);
+
+%% Watchdog has a new connection that will be opened after DW[RA]
+%% exchange.
+watchdog(TPid, [T], _, ?WD_REOPEN, Wd, State) ->
+    reopen({TPid, T}, Wd, State);
+
+%% Watchdog has recovered a suspect connection.
+watchdog(TPid, [], ?WD_SUSPECT, ?WD_OKAY, Wd, State) ->
+    #watchdog{peer = TPid} = Wd,  %% assert
+    connection_up(Wd, State);
+
+%% Watchdog has an unresponsive connection.
+watchdog(TPid, [], ?WD_OKAY, ?WD_SUSPECT = To, Wd, State) ->
+    #watchdog{peer = TPid} = Wd,  %% assert
+    connection_down(Wd, To, State);
+
+%% Watchdog has lost its connection.
+watchdog(TPid, [], _, ?WD_DOWN = To, Wd, #state{peerT = PeerT} = S) ->
+    close(Wd, S),
+    connection_down(Wd, To, S),
+    ets:delete(PeerT, TPid);
+
+watchdog(_, [], _, _, _, _) ->
+    ok.
 
 %%% ---------------------------------------------------------------------------
 %%% # connection_up/3
@@ -977,72 +939,61 @@ fetch(Tid, Key) ->
 
 %% Watchdog process has reached state OKAY.
 
-connection_up(Pid, {TPid, {Caps, SApps, Pkt}}, #state{peerT = PeerT,
-                                                      connT = ConnT}
-                                               = S) ->
-    P = fetch(PeerT, Pid),
-    C = #conn{pid = TPid,
-              apps = SApps,
-              caps = Caps,
-              peer = Pid},
-
-    insert(ConnT, C),
-    connection_up([Pkt], P#peer{conn = TPid}, C, S).
+connection_up({TPid, {Caps, SApps, Pkt}},
+              #watchdog{pid = Pid}
+              = Wd,
+              #state{peerT = PeerT}
+              = S) ->
+    Pr = #peer{pid = TPid,
+               apps = SApps,
+               caps = Caps,
+               watchdog = Pid},
+    insert(PeerT, Pr),
+    connection_up([Pkt], Wd#watchdog{peer = TPid}, Pr, S).
 
 %%% ---------------------------------------------------------------------------
 %%% # reopen/3
 %%% ---------------------------------------------------------------------------
 
-%% Note that this connection_up/3 rewrites the same #conn{} now
-%% written here. Both do so in case reopen has not happened in old
-%% code.
-
-reopen(Pid, {TPid, {Caps, SApps, _Pkt}}, #state{peerT = PeerT,
-                                                connT = ConnT}) ->
-    P = fetch(PeerT, Pid),
-    C = #conn{pid = TPid,
-              apps = SApps,
-              caps = Caps,
-              peer = Pid},
-
-    insert(ConnT, C),
-    #peer{op_state = {?STATE_DOWN, _}}
-        = P,
-    insert(PeerT, P#peer{op_state = {?STATE_DOWN, ?WD_REOPEN},
-                         conn = TPid}).
+reopen({TPid, {Caps, SApps, _Pkt}},
+       #watchdog{pid = Pid}
+       = Wd,
+       #state{watchdogT = WatchdogT,
+              peerT = PeerT}) ->
+    insert(PeerT, #peer{pid = TPid,
+                        apps = SApps,
+                        caps = Caps,
+                        watchdog = Pid}),
+    insert(WatchdogT, Wd#watchdog{state = ?WD_REOPEN,
+                                  peer = TPid}).
 
 %%% ---------------------------------------------------------------------------
 %%% # connection_up/2
 %%% ---------------------------------------------------------------------------
 
-%% Peer process has transitioned back into the open state. Note that there
-%% has been no new capabilties exchange in this case.
+%% Watchdog has recovered as suspect connection. Note that there has
+%% been no new capabilties exchange in this case.
 
-connection_up(Pid, #state{peerT = PeerT,
-                          connT = ConnT}
-                   = S) ->
-    #peer{conn = TPid} = P = fetch(PeerT, Pid),
-    C = fetch(ConnT, TPid),
-    connection_up([], P, C, S).
+connection_up(#watchdog{peer = TPid} = Wd, #state{peerT = PeerT} = S) ->
+    connection_up([], Wd, fetch(PeerT, TPid), S).
 
 %% connection_up/4
 
-connection_up(T, P, C, #state{peerT = PeerT,
-                              local_peers = LDict,
-                              service_name = SvcName,
-                              service
-                              = #diameter_service{applications = Apps}}
-                       = S) ->
-    #peer{conn = TPid, op_state = {?STATE_DOWN, _}}
-        = P,
-    #conn{apps = SApps, caps = Caps}
-        = C,
-
-    insert(PeerT, P#peer{op_state = {?STATE_UP, ?WD_OKAY}}),
-
+connection_up(Extra,
+              #watchdog{peer = TPid}
+              = Wd,
+              #peer{apps = SApps, caps = Caps}
+              = Pr,
+              #state{watchdogT = WatchdogT,
+                     local_peers = LDict,
+                     service_name = SvcName,
+                     service
+                     = #diameter_service{applications = Apps}}
+              = S) ->
+    insert(WatchdogT, Wd#watchdog{state = ?WD_OKAY}),
     request_peer_up(TPid),
     insert_local_peer(SApps, {{TPid, Caps}, {SvcName, Apps}}, LDict),
-    report_status(up, P, C, S, T).
+    report_status(up, Wd, Pr, S, Extra).
 
 insert_local_peer(SApps, T, LDict) ->
     lists:foldl(fun(A,D) -> ilp(A, T, D) end, LDict, SApps).
@@ -1078,41 +1029,38 @@ peer_cb(MFA, Alias) ->
     end.
 
 %%% ---------------------------------------------------------------------------
-%%% # connection_down/2
+%%% # connection_down/3
 %%% ---------------------------------------------------------------------------
 
-%% Watchdog has transitioned out of state OKAY.
-
-connection_down(Pid, #state{peerT = PeerT,
-                            connT = ConnT}
-                     = S) ->
-    #peer{op_state = {?STATE_UP, WS},  %% assert
-          conn = TPid}
-        = P
-        = fetch(PeerT, Pid),
-
-    C = fetch(ConnT, TPid),
-    insert(PeerT, P#peer{op_state = {?STATE_DOWN, WS}}),
-    connection_down(P,C,S).
-
-%% connection_down/3
-
-connection_down(#peer{op_state = {?STATE_DOWN, _}}, _, _) ->
-    ok;
-
-connection_down(#peer{conn = TPid,
-                      op_state = {?STATE_UP, _}}
-                = P,
-                #conn{caps = Caps,
+connection_down(#watchdog{state = ?WD_OKAY,
+                          peer = TPid}
+                = Wd,
+                #peer{caps = Caps,
                       apps = SApps}
-                = C,
+                = Pr,
                 #state{service_name = SvcName,
                        service = #diameter_service{applications = Apps},
                        local_peers = LDict}
                 = S) ->
-    report_status(down, P, C, S, []),
+    report_status(down, Wd, Pr, S, []),
     remove_local_peer(SApps, {{TPid, Caps}, {SvcName, Apps}}, LDict),
-    request_peer_down(TPid, S).
+    request_peer_down(TPid, S);
+
+connection_down(#watchdog{}, #peer{}, _) ->
+    ok;
+
+connection_down(#watchdog{state = WS,
+                          peer = TPid}
+                = Wd,
+                To,
+                #state{watchdogT = WatchdogT,
+                       peerT = PeerT}
+                = S)
+  when is_atom(To) ->
+    insert(WatchdogT, Wd#watchdog{state = To}),
+    ?WD_OKAY == WS
+        andalso
+        connection_down(Wd, fetch(PeerT, TPid), S).
 
 remove_local_peer(SApps, T, LDict) ->
     lists:foldl(fun(A,D) -> rlp(A, T, D) end, LDict, SApps).
@@ -1130,64 +1078,51 @@ down_conn(Id, Alias, TC, {SvcName, Apps}) ->
     peer_cb({ModX, peer_down, [SvcName, TC]}, Alias).
 
 %%% ---------------------------------------------------------------------------
-%%% # peer_down/3
+%%% # watchdog_down/2
 %%% ---------------------------------------------------------------------------
 
 %% Watchdog process has died.
 
-peer_down(Pid, Reason, #state{peerT = PeerT} = S) ->
-    P = fetch(PeerT, Pid),
-    ets:delete_object(PeerT, P),
-    closed(Reason, P, S),
-    restart(P,S),
-    peer_down(P,S).
-
-%% Send an event at connection establishment failure.
-closed({shutdown, {close, _TPid, Reason}},
-       #peer{op_state = {?STATE_DOWN, _},
-             ref = Ref,
-             type = Type,
-             options = Opts},
-       #state{service_name = SvcName}) ->
-    send_event(SvcName, {closed, Ref, Reason, {type(Type), Opts}});
-closed(_, _, _) ->
-    ok.
+watchdog_down(Pid, #state{watchdogT = WatchdogT} = S) ->
+    Wd = fetch(WatchdogT, Pid),
+    ets:delete_object(WatchdogT, Wd),
+    restart(Wd,S),
+    wd_down(Wd,S).
 
-%% The watchdog has never reached OKAY ...
-peer_down(#peer{conn = B}, _)
+%% Watchdog has never reached OKAY ...
+wd_down(#watchdog{peer = B}, _)
   when is_boolean(B) ->
     ok;
 
 %% ... or maybe it has.
-peer_down(#peer{conn = TPid} = P, #state{connT = ConnT} = S) ->
-    #conn{} = C = fetch(ConnT, TPid),
-    ets:delete_object(ConnT, C),
-    connection_down(P,C,S).
+wd_down(#watchdog{peer = TPid} = Wd, #state{peerT = PeerT} = S) ->
+    connection_down(Wd, ?WD_DOWN, S),
+    ets:delete(PeerT, TPid).
 
 %% restart/2
 
-restart(P,S) ->
-    q_restart(restart(P), S).
+restart(Wd, S) ->
+    q_restart(restart(Wd), S).
 
 %% restart/1
 
 %% Always try to reconnect.
-restart(#peer{ref = Ref,
-              type = connect = T,
-              options = Opts,
-              started = Time}) ->
+restart(#watchdog{ref = Ref,
+                  type = connect = T,
+                  options = Opts,
+                  started = Time}) ->
     {Time, {Ref, T, Opts}};
 
 %% Transport connection hasn't yet been accepted ...
-restart(#peer{ref = Ref,
-              type = accept = T,
-              options = Opts,
-              conn = false,
-              started = Time}) ->
+restart(#watchdog{ref = Ref,
+                  type = accept = T,
+                  options = Opts,
+                  peer = false,
+                  started = Time}) ->
     {Time, {Ref, T, Opts}};
 
 %% ... or it has: a replacement has already been spawned.
-restart(#peer{type = accept}) ->
+restart(#watchdog{type = accept}) ->
     false.
 
 %% q_restart/2
@@ -1248,14 +1183,13 @@ tc(false = No, _, _) ->  %% removed
 %% the accepting watchdog upon reception of a CER from the previously
 %% connected peer, or us after reconnect_timer timeout.
 
-close(Pid, #state{service_name = SvcName,
-                  peerT = PeerT}) ->
-    #peer{pid = Pid,
-          type = accept,
-          ref = Ref,
-          options = Opts}
-        = fetch(PeerT, Pid),
-
+close(#watchdog{type = connect}, _) ->
+    ok;
+close(#watchdog{type = accept,
+                pid = Pid,
+                ref = Ref,
+                options = Opts},
+      #state{service_name = SvcName}) ->
     c(Pid, diameter_config:have_transport(SvcName, Ref), Opts).
 
 %% Tell watchdog to (maybe) die later ...
@@ -1278,11 +1212,11 @@ c(Pid, false, _Opts) ->
 %%% ---------------------------------------------------------------------------
 
 reconnect(Pid, #state{service_name = SvcName,
-                      peerT = PeerT}) ->
-    #peer{ref = Ref,
-          type = connect,
-          options = Opts}
-        = fetch(PeerT, Pid),
+                      watchdogT = WatchdogT}) ->
+    #watchdog{ref = Ref,
+              type = connect,
+              options = Opts}
+        = fetch(WatchdogT, Pid),
     send_event(SvcName, {reconnect, Ref, Opts}).
 
 %%% ---------------------------------------------------------------------------
@@ -1742,6 +1676,8 @@ have_request(Pkt, TPid) ->
 
 %% request_peer_up/1
 
+%% Insert an element that is used to detect whether or not there has
+%% been a failover when inserting an outgoing request.
 request_peer_up(TPid) ->
     ets:insert(?REQUEST_TABLE, {TPid}).
 
@@ -1760,8 +1696,8 @@ request_peer_down(TPid, S) ->
 %%% recv_request/3
 %%% ---------------------------------------------------------------------------
 
-recv_request(TPid, Pkt, {ConnT, SvcName, Apps, Mask}) ->
-    try ets:lookup(ConnT, TPid) of
+recv_request(TPid, Pkt, {PeerT, SvcName, Apps, Mask}) ->
+    try ets:lookup(PeerT, TPid) of
         [C] ->
             recv_request(C, TPid, Pkt, SvcName, Apps, Mask);
         [] ->             %% transport has gone down
@@ -1773,7 +1709,7 @@ recv_request(TPid, Pkt, {ConnT, SvcName, Apps, Mask}) ->
 
 %% recv_request/5
 
-recv_request(#conn{apps = SApps, caps = Caps},
+recv_request(#peer{apps = SApps, caps = Caps},
              TPid,
              Pkt,
              SvcName,
@@ -2593,11 +2529,11 @@ rt(#request{packet = #diameter_packet{msg = Msg},
 %%% ---------------------------------------------------------------------------
 
 report_status(Status,
-              #peer{ref = Ref,
-                    conn = TPid,
-                    type = Type,
-                    options = Opts},
-              #conn{apps = [_|_] = As,
+              #watchdog{ref = Ref,
+                        peer = TPid,
+                        type = Type,
+                        options = Opts},
+              #peer{apps = [_|_] = As,
                     caps = Caps},
               #state{service_name = SvcName}
               = S,
@@ -2676,7 +2612,7 @@ rpd(Pid, Alias, PDict) ->
 %%% ---------------------------------------------------------------------------
 %%% find_transport/[34]
 %%%
-%%% Output: {TransportPid, #diameter_caps{}, #diameter_app{}}
+%%% Return: {TransportPid, #diameter_caps{}, #diameter_app{}}
 %%%         | false
 %%%         | {error, Reason}
 %%% ---------------------------------------------------------------------------
@@ -2814,7 +2750,7 @@ avp_decode(_, _, #diameter_avp{value = V}) ->
 %%% ---------------------------------------------------------------------------
 %%% # pick_peer(App, [DestRealm, DestHost], Filter, #state{})
 %%%
-%%% Output: {TransportPid, #diameter_caps{}, App}
+%%% Return: {TransportPid, #diameter_caps{}, App}
 %%%         | false
 %%%         | {error, Reason}
 %%% ---------------------------------------------------------------------------
@@ -2966,8 +2902,8 @@ eq(Any, Id, PeerId) ->
 
 %% transports/1
 
-transports(#state{peerT = PeerT}) ->
-    ets:select(PeerT, [{#peer{conn = '$1', _ = '_'},
+transports(#state{watchdogT = WatchdogT}) ->
+    ets:select(WatchdogT, [{#watchdog{peer = '$1', _ = '_'},
                         [{'is_pid', '$1'}],
                         ['$1']}]).
 
@@ -3021,11 +2957,12 @@ tagged_info(Item, S)
             undefined
     end;
 
-tagged_info(TPid, #state{peerT = PT, connT = CT})
+tagged_info(TPid, #state{watchdogT = WatchdogT, peerT = PeerT})
   when is_pid(TPid) ->
     try
-        [#conn{peer = Pid}] = ets:lookup(CT, TPid),
-        [#peer{ref = Ref, type = Type, options = Opts}] = ets:lookup(PT, Pid),
+        [#peer{watchdog = Pid}] = ets:lookup(PeerT, TPid),
+        [#watchdog{ref = Ref, type = Type, options = Opts}]
+            = ets:lookup(WatchdogT, Pid),
         [{ref, Ref},
          {type, Type},
          {options, Opts}]
@@ -3108,11 +3045,11 @@ complete(Pre) ->
 
 %% info_stats/1
 
-info_stats(#state{peerT = PeerT}) ->
-    MatchSpec = [{#peer{ref = '$1', conn = '$2', _ = '_'},
+info_stats(#state{watchdogT = WatchdogT}) ->
+    MatchSpec = [{#watchdog{ref = '$1', peer = '$2', _ = '_'},
                   [{'is_pid', '$2'}],
                   [['$1', '$2']]}],
-    try ets:select(PeerT, MatchSpec) of
+    try ets:select(WatchdogT, MatchSpec) of
         L ->
             diameter_stats:read(lists:append(L))
     catch
@@ -3122,7 +3059,8 @@ info_stats(#state{peerT = PeerT}) ->
 %% info_transport/1
 %%
 %% One entry per configured transport. Statistics for each entry are
-%% the accumulated values for the ref and associated peer pids.
+%% the accumulated values for the ref and associated watchdog/peer
+%% pids.
 
 info_transport(S) ->
     PeerD = peer_dict(S, config_dict(S)),
@@ -3155,43 +3093,42 @@ transport([[_,_] | L]) ->
 
 %% Possibly many peer entries for a listening transport. Note that all
 %% have the same options by construction, which is not terribly space
-%% efficient. (TODO: all entries for the same Ref should share options.)
+%% efficient.
 transport([[{type, accept}, {options, Opts} | _] | _] = Ls) ->
     [{type, listen},
      {options, Opts},
      {accept, [lists:nthtail(2,L) || L <- Ls]}].
 
-peer_dict(#state{peerT = PeerT, connT = ConnT}, Dict0) ->
-    try ets:tab2list(PeerT) of
+peer_dict(#state{watchdogT = WatchdogT, peerT = PeerT}, Dict0) ->
+    try ets:tab2list(WatchdogT) of
         L ->
-            lists:foldl(fun(T,A) -> peer_acc(ConnT, A, T) end, Dict0, L)
+            lists:foldl(fun(T,A) -> peer_acc(PeerT, A, T) end, Dict0, L)
     catch
         error: badarg -> Dict0  %% service has gone down
     end.
 
-peer_acc(ConnT, Acc, #peer{pid = Pid,
-                           type = Type,
-                           ref = Ref,
-                           options = Opts,
-                           op_state = OS,
-                           started = T,
-                           conn = TPid}) ->
-    WS = wd_state(OS),
+peer_acc(PeerT, Acc, #watchdog{pid = Pid,
+                               type = Type,
+                               ref = Ref,
+                               options = Opts,
+                               state = WS,
+                               started = At,
+                               peer = TPid}) ->
     dict:append(Ref,
                 [{type, Type},
                  {options, Opts},
-                 {watchdog, {Pid, T, WS}}
-                 | info_conn(ConnT, TPid, WS /= ?WD_DOWN)],
+                 {watchdog, {Pid, At, WS}}
+                 | info_peer(PeerT, TPid, WS)],
                 Acc).
 
-info_conn(ConnT, TPid, true)
-  when is_pid(TPid) ->
-    try ets:lookup(ConnT, TPid) of
-        T -> info_conn(T)
+info_peer(PeerT, TPid, WS)
+  when is_pid(TPid), WS /= ?WD_DOWN ->
+    try ets:lookup(PeerT, TPid) of
+        T -> info_peer(T)
     catch
         error: badarg -> []  %% service has gone down
     end;
-info_conn(_, _, _) ->
+info_peer(_, _, _) ->
     [].
 
 %% The point of extracting the config here is so that 'transport' info
@@ -3210,19 +3147,12 @@ config_acc({Ref, T, Opts}, Dict)
 config_acc(_, Dict) ->
     Dict.
 
-wd_state({_,S}) ->
-    S;
-wd_state(?STATE_UP) ->
-    ?WD_OKAY;
-wd_state(?STATE_DOWN) ->
-    ?WD_DOWN.
-
-info_conn([#conn{pid = Pid, apps = SApps, caps = Caps, started = T}]) ->
+info_peer([#peer{pid = Pid, apps = SApps, caps = Caps, started = T}]) ->
     [{peer, {Pid, T}},
      {apps, SApps},
      {caps, info_caps(Caps)}
      | try [{port, info_port(Pid)}] catch _:_ -> [] end];
-info_conn([] = No) ->
+info_peer([] = No) ->
     No.
 
 %% Extract information that the processes involved are expected to
diff --git a/lib/diameter/src/base/diameter_watchdog.erl b/lib/diameter/src/base/diameter_watchdog.erl
index a5429c967c..10ab246b88 100644
--- a/lib/diameter/src/base/diameter_watchdog.erl
+++ b/lib/diameter/src/base/diameter_watchdog.erl
@@ -62,11 +62,13 @@
          restrict :: {diameter:restriction(), boolean()},
          shutdown = false :: boolean()}).
 
+%% ---------------------------------------------------------------------------
 %% start/2
 %%
 %% Start a monitor before the watchdog is allowed to proceed to ensure
 %% that a failed capabilities exchange produces the desired exit
 %% reason.
+%% ---------------------------------------------------------------------------
 
 -spec start(Type, {RecvData, [Opt], SvcName, SvcOpts, #diameter_service{}})
    -> {reference(), pid()}
@@ -77,12 +79,12 @@
       SvcName :: diameter:service_name().
 
 start({_,_} = Type, T) ->
-    Ref = make_ref(),
-    {ok, Pid} = diameter_watchdog_sup:start_child({Ref, {Type, self(), T}}),
+    Ack = make_ref(),
+    {ok, Pid} = diameter_watchdog_sup:start_child({Ack, Type, self(), T}),
     try
         {erlang:monitor(process, Pid), Pid}
     after
-        Pid ! Ref
+        send(Pid, Ack)
     end.
 
 start_link(T) ->
@@ -101,22 +103,15 @@ init(T) ->
     proc_lib:init_ack({ok, self()}),
     gen_server:enter_loop(?MODULE, [], i(T)).
 
-i({Ref, {_, Pid, _} = T}) ->
-    MRef = erlang:monitor(process, Pid),
-    receive
-        Ref ->
-            make_state(T);
-        {'DOWN', MRef, process, _, _} = D ->
-            exit({shutdown, D})
-    end.
-
-make_state({T, Pid, {RecvData,
-                     Opts,
-                     SvcName,
-                     SvcOpts,
-                     #diameter_service{applications = Apps,
-                                       capabilities = Caps}
-                     = Svc}}) ->
+i({Ack, T, Pid, {RecvData,
+                 Opts,
+                 SvcName,
+                 SvcOpts,
+                 #diameter_service{applications = Apps,
+                                   capabilities = Caps}
+                 = Svc}}) ->
+    erlang:monitor(process, Pid),
+    wait(Ack, Pid),
     random:seed(now()),
     putr(restart, {T, Opts, Svc}),  %% save seeing it in trace
     putr(dwr, dwr(Caps)),           %%
@@ -124,9 +119,7 @@ make_state({T, Pid, {RecvData,
     Restrict = proplists:get_value(restrict_connections, SvcOpts),
     Nodes = restrict_nodes(Restrict),
     #watchdog{parent = Pid,
-              transport = monitor(diameter_peer_fsm:start(T,
-                                                        Opts,
-                                                      {Mask, Nodes, Svc})),
+              transport = start(T, Opts, Mask, Nodes, Svc),
               tw = proplists:get_value(watchdog_timer,
                                        Opts,
                                        ?DEFAULT_TW_INIT),
@@ -134,6 +127,21 @@ make_state({T, Pid, {RecvData,
               sequence = Mask,
               restrict = {Restrict, lists:member(node(), Nodes)}}.
 
+wait(Ref, Pid) ->
+    receive
+        Ref ->
+            ok;
+        {'DOWN', _, process, Pid, _} = D ->
+            exit({shutdown, D})
+    end.
+
+%% start/5
+
+start(T, Opts, Mask, Nodes, Svc) ->
+    {_MRef, Pid}
+        = diameter_peer_fsm:start(T, Opts, {Mask, Nodes, Svc}),
+    Pid.
+
 %% handle_call/3
 
 handle_call(_, _, State) ->
@@ -151,41 +159,59 @@ handle_info(T, #watchdog{} = State) ->
         ok ->
             {noreply, State};
         #watchdog{} = S ->
-            event(State, S),
+            close(T, State),     %% service expects 'close' message
+            event(T, State, S),  %%   before 'watchdog'
             {noreply, S};
         stop ->
             ?LOG(stop, T),
-            event(State, State#watchdog{status = down}),
+            event(T, State, State#watchdog{status = down}),
             {stop, {shutdown, T}, State}
-    end;
+    end.
 
-handle_info(T, S) ->
-    handle_info(T, upgrade(S)).
+close({'DOWN', _, process, TPid, {shutdown, Reason}},
+      #watchdog{transport = TPid,
+                parent = Pid}) ->
+    send(Pid, {close, self(), Reason});
 
-upgrade(S) ->
-    #watchdog{} = list_to_tuple(tuple_to_list(S)
-                                ++ [?NOMASK, {nodes, true}, false]).
+close(_, _) ->
+    ok.
 
-event(#watchdog{status = T}, #watchdog{status = T}) ->
+event(_, #watchdog{status = T}, #watchdog{status = T}) ->
     ok;
 
-event(#watchdog{transport = undefined}, #watchdog{transport = undefined}) ->
+event(_, #watchdog{transport = undefined}, #watchdog{transport = undefined}) ->
     ok;
 
-event(#watchdog{status = From, transport = F, parent = Pid},
+event(Msg,
+      #watchdog{status = From, transport = F, parent = Pid},
       #watchdog{status = To, transport = T}) ->
-    E = {tpid(F,T), From, To},
-    notify(Pid, E),
+    TPid = tpid(F,T),
+    E = {[TPid | data(Msg, TPid, From, To)], From, To},
+    send(Pid, {watchdog, self(), E}),
     ?LOG(transition, {self(), E}).
 
+data(Msg, TPid, reopen, okay) ->
+    {recv, TPid, 'DWA', _Pkt} = Msg,  %% assert
+    {TPid, T} = eraser(open),
+    [T];
+
+data({open, TPid, _Hosts, T}, TPid, _From, To)
+  when To == okay;
+       To == reopen ->
+    [T];
+
+data(_, _, _, _) ->
+    [].
+
 tpid(_, Pid)
   when is_pid(Pid) ->
     Pid;
+
 tpid(Pid, _) ->
     Pid.
 
-notify(Pid, E) ->
-    Pid ! {watchdog, self(), E}.
+send(Pid, T) ->
+    Pid ! T.
 
 %% terminate/2
 
@@ -215,15 +241,13 @@ transition(close, #watchdog{}) ->
     ok;
 
 %% Service is asking for the peer to be taken down gracefully.
-transition({shutdown, Pid}, #watchdog{parent = Pid,
-                                      transport = undefined,
-                                      status = S}) ->
-    down = S,  %% sanity check
+transition({shutdown, Pid, _}, #watchdog{parent = Pid,
+                                         transport = undefined}) ->
     stop;
-transition({shutdown = T, Pid}, #watchdog{parent = Pid,
-                                          transport = TPid}
-                                = S) ->
-    TPid ! {T, self()},
+transition({shutdown = T, Pid, Reason}, #watchdog{parent = Pid,
+                                                  transport = TPid}
+                                        = S) ->
+    send(TPid, {T, self(), Reason}),
     S#watchdog{shutdown = true};
 
 %% Parent process has died,
@@ -234,13 +258,9 @@ transition({'DOWN', _, process, Pid, _Reason},
 %% Transport has accepted a connection.
 transition({accepted = T, TPid}, #watchdog{transport = TPid,
                                            parent = Pid}) ->
-    Pid ! {T, self(), TPid},
+    send(Pid, {T, self(), TPid}),
     ok;
 
-%% Transport is telling us that its impending death isn't failure.
-transition({close, TPid, _Reason}, #watchdog{transport = TPid}) ->
-    stop;
-
 %%   STATE         Event                Actions              New State
 %%   =====         ------               -------              ----------
 %%   INITIAL       Connection up        SetWatchdog()        OKAY
@@ -255,15 +275,13 @@ transition({close, TPid, _Reason}, #watchdog{transport = TPid}) ->
 %% know the identity of the peer (ie. now) that we know that we're in
 %% state down rather than initial.
 
-transition({open, TPid, Hosts, T} = Open,
+transition({open, TPid, Hosts, _} = Open,
            #watchdog{transport = TPid,
                      status = initial,
-                     parent = Pid,
                      restrict = {_, R}}
            = S) ->
     case okay(getr(restart), Hosts, R) of
         okay ->
-            open(Pid, {TPid, T}),
             set_watchdog(S#watchdog{status = okay});
         reopen ->
             transition(Open, S#watchdog{status = down})
@@ -274,17 +292,15 @@ transition({open, TPid, Hosts, T} = Open,
 %%                                      SetWatchdog()
 %%                                      Pending = TRUE       REOPEN
 
-transition({open = P, TPid, _Hosts, T},
+transition({open = Key, TPid, _Hosts, T},
            #watchdog{transport = TPid,
-                     parent = Pid,
                      status = down}
            = S) ->
     %% Store the info we need to notify the parent to reopen the
     %% connection after the requisite DWA's are received, at which
     %% time we eraser(open). The reopen message is a later addition,
     %% to communicate the new capabilities as soon as they're known.
-    putr(P, {TPid, T}),
-    Pid ! {reopen, self(), {TPid, T}},
+    putr(Key, {TPid, T}),
     set_watchdog(send_watchdog(S#watchdog{status = reopen,
                                           num_dwa = 0}));
 
@@ -296,26 +312,18 @@ transition({open = P, TPid, _Hosts, T},
 %%   REOPEN        Connection down      CloseConnection()
 %%                                      SetWatchdog()        DOWN
 
-transition({'DOWN', _, process, TPid, _},
+transition({'DOWN', _, process, TPid, _Reason},
            #watchdog{transport = TPid,
-                     status = S,
-                     shutdown = D})
-  when S == initial;
-       D ->
+                     shutdown = true}) ->
     stop;
 
-transition({'DOWN', _, process, TPid, _},
-           #watchdog{transport = TPid}
+transition({'DOWN', _, process, TPid, _Reason},
+           #watchdog{transport = TPid,
+                     status = T}
            = S) ->
-    failover(S),
-    close(S),
-    set_watchdog(S#watchdog{status = down,
+    set_watchdog(S#watchdog{status = case T of initial -> T; _ -> down end,
                             pending = false,
                             transport = undefined});
-%% Any outstanding pending (or other messages from the transport) will
-%% have arrived before 'DOWN' since the message comes from the same
-%% process. Note that we could also get this message in the initial
-%% state.
 
 %% Incoming message.
 transition({recv, TPid, Name, Pkt}, #watchdog{transport = TPid} = S) ->
@@ -331,15 +339,11 @@ transition({timeout, _, tw}, #watchdog{}) ->
 
 %% State query.
 transition({state, Pid}, #watchdog{status = S}) ->
-    Pid ! {self(), S},
+    send(Pid, {self(), S}),
     ok.
 
 %% ===========================================================================
 
-monitor(Pid) ->
-    erlang:monitor(process, Pid),
-    Pid.
-
 putr(Key, Val) ->
     put({?MODULE, Key}, Val).
 
@@ -386,7 +390,7 @@ okay([{_,P}]) ->
 
 %% ... or it has.
 okay(C) ->
-    [_|_] = [P ! close || {_,P} <- C, self() /= P],
+    [_|_] = [send(P, close) || {_,P} <- C, self() /= P],
     reopen.
 
 %% set_watchdog/1
@@ -408,36 +412,13 @@ tw(T)
 tw({M,F,A}) ->
     apply(M,F,A).
 
-%% open/2
-
-open(Pid, {_,_} = T) ->
-    Pid ! {connection_up, self(), T}.
-
-%% failover/1
-
-failover(#watchdog{status = okay,
-                   parent = Pid}) ->
-    Pid ! {connection_down, self()};
-
-failover(_) ->
-    ok.
-
-%% close/1
-
-close(#watchdog{status = down}) ->
-    ok;
-
-close(#watchdog{parent = Pid}) ->
-    {{T, _}, _, _} = getr(restart),
-    T == accept andalso (Pid ! {close, self()}).
-
 %% send_watchdog/1
 
 send_watchdog(#watchdog{pending = false,
                         transport = TPid,
                         sequence = Mask}
               = S) ->
-    TPid ! {send, encode(getr(dwr), Mask)},
+    send(TPid, {send, encode(getr(dwr), Mask)}),
     ?LOG(send, 'DWR'),
     S#watchdog{pending = true}.
 
@@ -518,12 +499,10 @@ rcv(_, #watchdog{status = okay} = S) ->
 %%                                      SetWatchdog()        OKAY
 
 rcv('DWA', #watchdog{status = suspect} = S) ->
-    failback(S),
     set_watchdog(S#watchdog{status = okay,
                             pending = false});
 
 rcv(_, #watchdog{status = suspect} = S) ->
-    failback(S),
     set_watchdog(S#watchdog{status = okay});
 
 %%   REOPEN        Receive DWA &        Pending = FALSE
@@ -531,10 +510,8 @@ rcv(_, #watchdog{status = suspect} = S) ->
 %%                                      Failback()           OKAY
 
 rcv('DWA', #watchdog{status = reopen,
-                     num_dwa = 2 = N,
-                     parent = Pid}
+                     num_dwa = 2 = N}
            = S) ->
-    open(Pid, eraser(open)),
     S#watchdog{status = okay,
                num_dwa = N+1,
                pending = false};
@@ -553,11 +530,6 @@ rcv('DWA', #watchdog{status = reopen,
 rcv(_, #watchdog{status = reopen} = S) ->
     throwaway(S).
 
-%% failback/1
-
-failback(#watchdog{parent = Pid}) ->
-    Pid ! {connection_up, self()}.
-
 %% timeout/1
 %%
 %% The caller sets the watchdog on the return value.
@@ -582,7 +554,6 @@ timeout(#watchdog{status = T,
 timeout(#watchdog{status = okay,
                   pending = true}
   = S) ->
-    failover(S),
     S#watchdog{status = suspect};
 
 %%   SUSPECT       Timer expires        CloseConnection()
@@ -599,7 +570,6 @@ timeout(#watchdog{status = T,
   when T == suspect;
        T == reopen, P, N < 0 ->
     exit(TPid, {shutdown, watchdog_timeout}),
-    close(S),
     S#watchdog{status = down};
 
 %%   REOPEN        Timer expires &      NumDWA = -1
@@ -633,7 +603,9 @@ timeout(#watchdog{status = reopen,
 %% process has died. We only need to handle state down since we start
 %% the first watchdog when transitioning out of initial.
 
-timeout(#watchdog{status = down} = S) ->
+timeout(#watchdog{status = T} = S)
+  when T == initial;
+       T == down ->
     restart(S).
 
 %% restart/1
@@ -659,11 +631,9 @@ restart({{connect, _} = T, Opts, Svc}, #watchdog{parent = Pid,
                                                  sequence = Mask,
                                                  restrict = {R,_}}
                                        = S) ->
-    Pid ! {reconnect, self()},
+    send(Pid, {reconnect, self()}),
     Nodes = restrict_nodes(R),
-    S#watchdog{transport = monitor(diameter_peer_fsm:start(T,
-                                                         Opts,
-                                                       {Mask, Nodes, Svc})),
+    S#watchdog{transport = start(T, Opts, Mask, Nodes, Svc),
                restrict = {R, lists:member(node(), Nodes)}};
 
 %% No restriction on the number of connections to the same peer: just
diff --git a/lib/diameter/src/transport/diameter_tcp.erl b/lib/diameter/src/transport/diameter_tcp.erl
index 7ec7b1c5e7..596e582ab0 100644
--- a/lib/diameter/src/transport/diameter_tcp.erl
+++ b/lib/diameter/src/transport/diameter_tcp.erl
@@ -368,8 +368,6 @@ handle_info(T, #monitor{} = S) ->
 %% # code_change/3
 %% ---------------------------------------------------------------------------
 
-code_change(_, {transport, _, _, _, _} = S, _) ->
-    {ok, #transport{} = list_to_tuple(tuple_to_list(S) ++ [false])};
 code_change(_, State, _) ->
     {ok, State}.