Ensure DWR isn't sent immediately after DWA

Having the peer_fsm process answer DWR meant that watchdog timer expiry
could result in an outgoing DWR despite the fact that an incoming DWR
was just answered. Having the watchdog process answer avoids this.

diameter_peer_fsm must be loaded before diameter_watchdog.  It's
possible for one incoming DWR to go unanswered but a subsequent DWR will
be answered so no harm is done.

2 files changed, 40 insertions, 44 deletions

diff --git a/lib/diameter/src/base/diameter_peer_fsm.erl b/lib/diameter/src/base/diameter_peer_fsm.erl
index 4e55864168..2b99ecc59c 100644
--- a/lib/diameter/src/base/diameter_peer_fsm.erl
+++ b/lib/diameter/src/base/diameter_peer_fsm.erl
@@ -28,7 +28,8 @@
 -behaviour(gen_server).
 
 %% Interface towards diameter_watchdog.
--export([start/3]).
+-export([start/3,
+         result_code/2]).
 
 %% gen_server callbacks
 -export([init/1,
@@ -62,7 +63,6 @@
 %% Keys in process dictionary.
 -define(CB_KEY, cb).         %% capabilities callback
 -define(DPR_KEY, dpr).       %% disconnect callback
--define(DWA_KEY, dwa).       %% outgoing DWA
 -define(REF_KEY, ref).       %% transport_ref()
 -define(Q_KEY, q).           %% transport start queue
 -define(START_KEY, start).   %% start of connected transport
@@ -177,14 +177,9 @@ init(T) ->
     proc_lib:init_ack({ok, self()}),
     gen_server:enter_loop(?MODULE, [], i(T)).
 
-i({Ack, WPid, {M, Ref} = T, Opts, {Mask,
-                                   Nodes,
-                                   Dict0,
-                                   #diameter_service{capabilities = LCaps}
-                                   = Svc}}) ->
+i({Ack, WPid, {M, Ref} = T, Opts, {Mask, Nodes, Dict0, Svc}}) ->
     erlang:monitor(process, WPid),
     wait(Ack, WPid),
-    putr(?DWA_KEY, dwa(LCaps)),
     diameter_stats:reg(Ref),
     {[Cs,Ds], Rest} = proplists:split(Opts, [capabilities_cb, disconnect_cb]),
     putr(?CB_KEY, {Ref, [F || {_,F} <- Cs]}),
@@ -612,9 +607,7 @@ rcv(Name, _, #state{state = PS})
        Name == 'CEA' ->
     {stop, {Name, PS}};
 
-rcv(N, Pkt, S)
-  when N == 'DWR';
-       N == 'DPR' ->
+rcv('DPR' = N, Pkt, S) ->
     handle_request(N, Pkt, S);
 
 %% DPA in response to DPR and with the expected identifiers.
@@ -717,8 +710,8 @@ build_answer(Type,
                               errors = Es}
              = Pkt,
              S) ->
-    RC = rc(H, Es),
-    {answer(Type, RC, Es, S), post(Type, RC, Pkt, S)}.
+    {RC, FailedAVP} = result_code(H, Es),
+    {answer(Type, RC, FailedAVP, S), post(Type, RC, Pkt, S)}.
 
 inband_security([]) ->
     ?NO_INBAND_SECURITY;
@@ -734,7 +727,7 @@ cea(CEA, RC, Dict0) ->
 
 post('CER' = T, RC, Pkt, S) ->
     {T, caps(S), {RC, Pkt}};
-post(_, _, _, _) ->
+post('DPR', _, _, _) ->
     ok.
 
 rejected({capabilities_cb, _F, Reason}, T, S) ->
@@ -743,13 +736,10 @@ rejected({capabilities_cb, _F, Reason}, T, S) ->
 rejected(discard, T, _) ->
     close(T);
 rejected({N, Es}, T, S) ->
-    {answer('CER', N, Es, S), T};
+    {answer('CER', N, failed_avp(N, Es), S), T};
 rejected(N, T, S) ->
     rejected({N, []}, T, S).
 
-answer(Type, RC, Es, S) ->
-    set(answer(Type, RC, S), failed_avp(RC, Es)).
-
 failed_avp(RC, [{RC, Avp} | _]) ->
     [{'Failed-AVP', [{'AVP', [Avp]}]}];
 failed_avp(RC, [_ | Es]) ->
@@ -757,6 +747,9 @@ failed_avp(RC, [_ | Es]) ->
 failed_avp(_, [] = No) ->
     No.
 
+answer(Type, RC, FailedAVP, S) ->
+    set(answer(Type, RC, S), FailedAVP).
+
 answer(Type, RC, S) ->
     answer_message(answer(Type, S), RC).
 
@@ -784,29 +777,29 @@ set(['answer-message' | _] = Ans, FailedAvp) ->
 set([_|_] = Ans, FailedAvp) ->
     Ans ++ FailedAvp.
 
-%% rc/2
+%% result_code/2
 
-rc(#diameter_header{is_error = true}, _) ->
-    3008;  %% DIAMETER_INVALID_HDR_BITS
+result_code(#diameter_header{is_error = true}, _) ->
+    {3008, []};  %% DIAMETER_INVALID_HDR_BITS
 
-rc(_, [Bs|_])
+result_code(_, [Bs|_])
   when is_bitstring(Bs) ->  %% from old code
-    3009;  %% DIAMETER_INVALID_HDR_BITS
+    {3009, []};  %% DIAMETER_INVALID_HDR_BITS
 
-rc(#diameter_header{version = ?DIAMETER_VERSION}, Es) ->
+result_code(#diameter_header{version = ?DIAMETER_VERSION}, Es) ->
     rc(Es);
 
-rc(_, _) ->
-    5011.  %% DIAMETER_UNSUPPORTED_VERSION
+result_code(_, _) ->
+    {5011, []}.  %% DIAMETER_UNSUPPORTED_VERSION
 
 %% rc/1
 
 rc([]) ->
-    2001;  %% DIAMETER_SUCCESS
-rc([{RC,_}|_]) ->
-    RC;
+    {2001, []};  %% DIAMETER_SUCCESS
+rc([{RC, _} | _] = Es) ->
+    {RC, failed_avp(RC, Es)};
 rc([RC|_]) ->
-    RC.
+    {RC, []}.
 
 %%   DIAMETER_INVALID_HDR_BITS          3008
 %%      A request was received whose bits in the Diameter header were
@@ -832,9 +825,6 @@ rc([RC|_]) ->
 
 %% answer/2
 
-answer('DWR', _) ->
-    getr(?DWA_KEY);
-
 answer(Name, #state{service = #diameter_service{capabilities = Caps}}) ->
     a(Name, Caps).
 
@@ -1019,15 +1009,6 @@ report({M, _, _, _, _} = T)
 report(_) ->
     ok.
 
-%% dwa/1
-
-dwa(#diameter_caps{origin_host = OH,
-                   origin_realm = OR,
-                   origin_state_id = OSI}) ->
-    ['DWA', {'Origin-Host', OH},
-            {'Origin-Realm', OR},
-            {'Origin-State-Id', OSI}].
-
 %% dpr/2
 %%
 %% The RFC isn't clear on whether DPR should be send in a non-Open
diff --git a/lib/diameter/src/base/diameter_watchdog.erl b/lib/diameter/src/base/diameter_watchdog.erl
index 88ccf630e2..7e75801718 100644
--- a/lib/diameter/src/base/diameter_watchdog.erl
+++ b/lib/diameter/src/base/diameter_watchdog.erl
@@ -201,7 +201,7 @@ common_dictionary(Apps) ->
             %% means a user won't be able either send of receive
             %% messages in the common dictionary: incoming request
             %% will be answered with 3007 and outgoing requests cannot
-            %% be sent. The dictionary returned here is oly used for
+            %% be sent. The dictionary returned here is only used for
             %% messages diameter sends and receives: CER/CEA, DPR/DPA
             %% and DWR/DWA.
             ?BASE
@@ -545,10 +545,15 @@ recv(Name, Pkt, S) ->
 
 %% rcv/3
 
+rcv('DWR', Pkt, #watchdog{transport = TPid,
+                          dictionary = Dict0,
+                          sequence = Mask}) ->
+    send(TPid, {send, encode(dwa(Pkt), Mask, Dict0)}),
+    ?LOG(send, 'DWA');
+
 rcv(N, _, _)
   when N == 'CER';
        N == 'CEA';
-       N == 'DWR';
        N == 'DWA';
        N == 'DPR';
        N == 'DPA' ->
@@ -642,6 +647,9 @@ rcv('DWA', #watchdog{status = reopen,
 
 %%   REOPEN        Receive non-DWA      Throwaway()          REOPEN
 
+rcv('DWR', #watchdog{status = reopen} = S) ->
+    S;  %% ensure DWA: the RFC isn't explicit about answering
+
 rcv(_, #watchdog{status = reopen} = S) ->
     throwaway(S).
 
@@ -782,6 +790,13 @@ dwr(#diameter_caps{origin_host = OH,
             {'Origin-Realm', OR},
             {'Origin-State-Id', OSI}].
 
+%% dwa/1
+
+dwa(#diameter_packet{header = H, errors = Es}) ->
+    {RC, FailedAVP} = diameter_peer_fsm:result_code(H, Es),
+    ['DWA', {'Result-Code', RC}
+          | tl(getr(dwr)) ++ FailedAVP].
+
 %% restrict_nodes/1
 
 restrict_nodes(false) ->