Fix bugs in sending of answer-message replies

3001 (DIAMETER_COMMAND_UNSUPPORTED) was not sent since the decode
placed the AVP list in the errors field rather than the avps field
of the diameter_packet, causing the subsequent encode to fail.
Session-Id was also set improperly, causing encode to fail even
in this case.

2 files changed, 14 insertions, 36 deletions

diff --git a/lib/diameter/src/app/diameter_codec.erl b/lib/diameter/src/app/diameter_codec.erl
index f6cbde5446..d88f42fb7c 100644
--- a/lib/diameter/src/app/diameter_codec.erl
+++ b/lib/diameter/src/app/diameter_codec.erl
@@ -140,10 +140,10 @@ make_flags(Flags0, #diameter_header{is_request       = R,
 mf(undefined, F, _) ->
     F;
 mf(B, F, N) ->  %% reset the affected bit
-    (F bxor (F band (1 bsl N))) bor (bit(B) bsl N).
+    (F bxor (F band (1 bsl N))) bor bit(B, N).
 
-bit(true)  -> 1;
-bit(false) -> 0.
+bit(true, N)  -> 1 bsl N;
+bit(false, _) -> 0.
 
 %% values/1
 
@@ -199,25 +199,16 @@ msg_header(Mod, MsgName, Header) ->
 
 p(Flags, #diameter_header{is_request = true,
                           is_proxiable = P}) ->
-    Flags bor choose(P, 2#01000000, 0);
+    Flags band (2#10110000 bor choose(P, 2#01000000, 0));
 p(Flags, _) ->
     Flags.
 
-%% The header below is that of the incoming request being answered,
-%% not of the answer (which hasn't been encoded yet).
-
 h(Mod, 'answer-message' = MsgName, Header) ->
     ?BASE = Mod,
-    #diameter_header{is_request = true,
-                     cmd_code = Code}
-        = Header,
+    #diameter_header{cmd_code = Code} = Header,
     {_, Flags, ApplId} = ?BASE:msg_header(MsgName),
     {Code, Flags, ApplId};
 
-h(Mod, MsgName, #diameter_header{is_request = true,
-                                 cmd_code = Code}) ->
-    {Code, _, _} = Mod:msg_header(MsgName); %% ensure Code
-
 h(Mod, MsgName, _) ->
     Mod:msg_header(MsgName).
 
@@ -290,7 +281,8 @@ decode_avps(MsgName, Mod, Pkt, {Bs, Avps}) ->  %% invalid avp bits ...
 
 decode_avps('', Mod, Pkt, Avps) ->  %% unknown message ...
     ?LOG(unknown, {Mod, Pkt#diameter_packet.header}),
-    Pkt#diameter_packet{errors = lists:reverse(Avps)};
+    Pkt#diameter_packet{avps = lists:reverse(Avps),
+                        errors = [3001]};   %% DIAMETER_COMMAND_UNSUPPORTED
 %% msg = undefined identifies this case.
 
 decode_avps(MsgName, Mod, Pkt, Avps) ->  %% ... or not
diff --git a/lib/diameter/src/app/diameter_service.erl b/lib/diameter/src/app/diameter_service.erl
index 63b0649dc4..01a125fdc7 100644
--- a/lib/diameter/src/app/diameter_service.erl
+++ b/lib/diameter/src/app/diameter_service.erl
@@ -1971,24 +1971,20 @@ reply(Msg, Dict, TPid, #diameter_packet{errors = [H|_] = Es} = Pkt) ->
 
 %% make_reply_packet/2
 
+%% Binaries and header/avp lists are sent as-is.
 make_reply_packet(Bin, _)
   when is_binary(Bin) ->
     #diameter_packet{bin = Bin};
-
 make_reply_packet([#diameter_header{} | _] = Msg, _) ->
     #diameter_packet{msg = Msg};
 
+%% Otherwise a reply message clears the R and T flags and retains the
+%% P flag. The E flag will be set at encode.
 make_reply_packet(Msg, #diameter_packet{header = ReqHdr}) ->
-    #diameter_header{end_to_end_id = EId,
-                     hop_by_hop_id = Hid,
-                     is_proxiable = P}
-        = ReqHdr,
-
-    Hdr = #diameter_header{version = ?DIAMETER_VERSION,
-                           end_to_end_id = EId,
-                           hop_by_hop_id = Hid,
-                           is_proxiable = P,
-                           is_retransmitted = false},
+    Hdr = ReqHdr#diameter_header{version = ?DIAMETER_VERSION,
+                                 is_request = false,
+                                 is_error = undefined,
+                                 is_retransmitted = false},
     #diameter_packet{header = Hdr,
                      msg = Msg}.
 
@@ -2126,16 +2122,6 @@ answer_message({OH, OR, RC}, Avps) ->
 session_id(Code, Vid, Avps)
   when is_list(Avps) ->
     try
-        {value, #diameter_avp{} = Avp} = find_avp(Code, Vid, Avps),
-        Avp
-    catch
-        error: _ ->
-            []
-    end;
-
-session_id(Code, Vid, Avps)
-  when is_list(Avps) ->
-    try
         {value, #diameter_avp{data = D}} = find_avp(Code, Vid, Avps),
         [{'Session-Id', [?BASE:avp(decode, D, 'Session-Id')]}]
     catch