3 files changed, 59 insertions, 13 deletions

diff --git a/lib/diameter/include/diameter_gen.hrl b/lib/diameter/include/diameter_gen.hrl
index 97cf0c7e29..233eb8dd15 100644
--- a/lib/diameter/include/diameter_gen.hrl
+++ b/lib/diameter/include/diameter_gen.hrl
@@ -311,7 +311,9 @@ d(Name, Avp, Acc) ->
 
     Failed = relax(Name),  %% Not AvpName or else a failed Failed-AVP
                            %% decode is packed into 'AVP'.
-    try avp(decode, Data, AvpName) of
+    Mod = dict(Failed),    %% Dictionary to decode in.
+
+    try Mod:avp(decode, Data, AvpName) of
         V ->
             {Avps, T} = Acc,
             {H, A} = ungroup(V, Avp),
@@ -324,6 +326,25 @@ d(Name, Avp, Acc) ->
         reset(?FAILED_KEY, Failed)
     end.
 
+%% dict/1
+%%
+%% Retrieve the dictionary for the best-effort decode of Failed-AVP,
+%% as put by diameter_codec:decode/2. See that function for the
+%% explanation.
+
+dict(true) ->
+    case get({diameter_codec, dictionary}) of
+        undefined ->
+            ?MODULE;
+        Mod ->
+            Mod
+    end;
+
+dict(_) ->
+    ?MODULE.
+
+%% d/5
+
 %% Ignore a decode error within Failed-AVP ...
 d(true, _, Name, Avp, Acc) ->
     decode_AVP(Name, Avp, Acc);
@@ -341,6 +362,8 @@ d(false, Reason, Name, Avp, {Avps, Acc}) ->
     {Rec, Failed} = Acc,
     {[Avp|Avps], {Rec, [rc(Reason, Avp) | Failed]}}.
 
+%% relax/2
+
 %% Set false in the process dictionary as soon as we see a Grouped AVP
 %% that doesn't set the M-bit, so that is_strict() can say whether or
 %% not to ignore the M-bit on an encapsulated AVP.
@@ -357,22 +380,23 @@ relax(_, _) ->
 is_strict() ->
     false /= getr(?STRICT_KEY).
 
+%% relax/1
+%%
 %% Set true in the process dictionary as soon as we see Failed-AVP.
 %% Matching on 'Failed-AVP' assumes that this is the RFC AVP.
 %% Strictly, this doesn't need to be the case.
+
 relax('Failed-AVP') ->
-    case getr(?FAILED_KEY) of
-        undefined ->
-            putr(?FAILED_KEY, true);
-        true = Yes ->
-            Yes
-    end;
+    is_failed() orelse putr(?FAILED_KEY, true);
+
 relax(_) ->
     is_failed().
     
 is_failed() ->
     true == getr(?FAILED_KEY).
 
+%% reset/2
+
 reset(Key, undefined) ->
     eraser(Key);
 reset(_, _) ->
diff --git a/lib/diameter/src/base/diameter_codec.erl b/lib/diameter/src/base/diameter_codec.erl
index 06a4f5de64..a2b04bfd63 100644
--- a/lib/diameter/src/base/diameter_codec.erl
+++ b/lib/diameter/src/base/diameter_codec.erl
@@ -237,15 +237,35 @@ rec2msg(Mod, Rec) ->
 
 %% Unsuccessfully decoded AVPs will be placed in #diameter_packet.errors.
 
--spec decode(module(), #diameter_packet{} | binary())
+-spec decode(module() | {module(), module()}, #diameter_packet{} | binary())
    -> #diameter_packet{}.
 
+%% An Answer setting the E-bit. The application dictionary is needed
+%% for the best-effort decode of Failed-AVP, and the best way to make
+%% this available to the AVP decode in diameter_gen.hrl, without
+%% having to rewrite the entire codec generation, is to place it in
+%% the process dictionary. It's the code in diameter_gen.hrl (that's
+%% included by every generated codec module) that looks for the entry.
+%% Not ideal, but it solves the problem relatively simply.
+decode({Mod, Mod}, Pkt) ->
+    decode(Mod, Pkt);
+decode({Mod, AppMod}, Pkt) ->
+    Key = {?MODULE, dictionary},
+    put(Key, AppMod),
+    try
+        decode(Mod, Pkt)
+    after
+        erase(Key)
+    end;
+
+%% Or not: a request, or an answer not setting the E-bit.
 decode(Mod, Pkt) ->
     decode(Mod:id(), Mod, Pkt).
 
-%% If we're a relay application then just extract the avp's without
-%% any decoding of their data since we don't know the application in
-%% question.
+%% decode/3
+
+%% Relay application: just extract the avp's without any decoding of
+%% their data since we don't know the application in question.
 decode(?APP_ID_RELAY, _, #diameter_packet{} = Pkt) ->
     case collect_avps(Pkt) of
         {E, As} ->
@@ -274,6 +294,8 @@ decode(Id, Mod, Bin)
   when is_binary(Bin) ->
     decode(Id, Mod, #diameter_packet{header = decode_header(Bin), bin = Bin}).
 
+%% decode_avps/4
+
 decode_avps(MsgName, Mod, Pkt, {E, Avps}) ->
     ?LOG(invalid_avp_length, Pkt#diameter_packet.header),
     #diameter_packet{errors = Failed}
diff --git a/lib/diameter/src/base/diameter_traffic.erl b/lib/diameter/src/base/diameter_traffic.erl
index c4875c5975..280d09d7e8 100644
--- a/lib/diameter/src/base/diameter_traffic.erl
+++ b/lib/diameter/src/base/diameter_traffic.erl
@@ -476,7 +476,7 @@ send_A({Caps, Pkt}, TPid, Dict0, _RecvData) ->  %% unsupported application
     #diameter_packet{errors = [RC|_]} = Pkt,
     send_A(answer_message(RC, Caps, Dict0, Pkt),
            TPid,
-           Dict0,
+           {Dict0, Dict0},
            Pkt,
            [],
            []);
@@ -1457,7 +1457,7 @@ handle_answer(SvcName,
               = App,
               {answer, Req, Dict0, Pkt}) ->
     Dict = dict(AppDict, Dict0, Pkt),
-    handle_A(errors(Id, diameter_codec:decode(Dict, Pkt)),
+    handle_A(errors(Id, diameter_codec:decode({Dict, AppDict}, Pkt)),
              SvcName,
              Dict,
              Dict0,