Merge branch 'anders/diameter/performance/OTP-14521' into maint

* anders/diameter/performance/OTP-14521:
  Work around unexpected common_test behaviour
  Randomly skip groups in traffic suite
  Randomly disable traffic counters in traffic suite
  Add service_opt() traffic_counters
  Fix type spec
  Split AVPs at decode
  Avoid unnecessary copying of binaries in diameter_tcp
  Don't update diameter_tcp state unnecessarily
  Don't update diameter_tcp state unnecessarily
  Simplify extraction of incoming Diameter messages in diameter_tcp
  Restructure/simplify message reception in diameter_peer_fsm
  Sleep randomly at the start of (parallel) traffic testcases
  Fix ct return value in traffic suite
  Fix type spec
  Optimize sub-binaries
  Optimize sub-binaries
  Count AVPs in #diameter_avp.index
  Don't extract options unnecessarily at encode
  Redo message decode as a single pass

8 files changed, 675 insertions, 738 deletions

diff --git a/lib/diameter/src/base/diameter.erl b/lib/diameter/src/base/diameter.erl
index c919ff4c93..2e18a1d903 100644
--- a/lib/diameter/src/base/diameter.erl
+++ b/lib/diameter/src/base/diameter.erl
@@ -353,6 +353,7 @@ call(SvcName, App, Message) ->
     | {sequence, sequence() | evaluable()}
     | {share_peers, remotes()}
     | {decode_format, decode_format()}
+    | {traffic_counters, boolean()}
     | {string_decode, boolean()}
     | {strict_arities, true | strict_arities()}
     | {strict_mbit, boolean()}
diff --git a/lib/diameter/src/base/diameter_codec.erl b/lib/diameter/src/base/diameter_codec.erl
index 9b21bf4141..63e39b12d1 100644
--- a/lib/diameter/src/base/diameter_codec.erl
+++ b/lib/diameter/src/base/diameter_codec.erl
@@ -110,7 +110,7 @@ encode(Mod, Opts, Msg) ->
 
 enc(_, Opts, #diameter_packet{msg = [#diameter_header{} = Hdr | As]}
              = Pkt) ->
-    try encode_avps(reorder(As), Opts) of
+    try encode_avps(As, Opts) of
         Avps ->
             Bin = list_to_binary(Avps),
             Len = 20 + size(Bin),
@@ -206,51 +206,12 @@ values(Avps) ->
 
 %% Message as a list of #diameter_avp{} ...
 encode_avps(_, _, [#diameter_avp{} | _] = Avps, Opts) ->
-    encode_avps(reorder(Avps), Opts);
+    encode_avps(Avps, Opts);
 
 %% ... or as a tuple list or record.
 encode_avps(Mod, MsgName, Values, Opts) ->
     Mod:encode_avps(MsgName, Values, Opts).
 
-%% reorder/1
-%%
-%% Reorder AVPs for the relay case using the index field of
-%% diameter_avp records. Decode populates this field in collect_avps
-%% and presents AVPs in reverse order. A relay then sends the reversed
-%% list with a Route-Record AVP prepended. The goal here is just to do
-%% lists:reverse/1 in Grouped AVPs and the outer list, but only in the
-%% case there are indexed AVPs at all, so as not to reverse lists that
-%% have been explicilty sent (unindexed, in the desired order) as a
-%% diameter_avp list. The effect is the same as lists:keysort/2, but
-%% only on the cases we expect, not a general sort.
-
-reorder(Avps) ->
-    case reorder(Avps, []) of
-        false ->
-            Avps;
-        Sorted ->
-            Sorted
-    end.
-
-%% reorder/3
-
-%% In case someone has reversed the list already. (Not likely.)
-reorder([#diameter_avp{index = 0} | _] = Avps, Acc) ->
-    Avps ++ Acc;
-
-%% Assume indexed AVPs are in reverse order.
-reorder([#diameter_avp{index = N} = A | Avps], Acc)
-  when is_integer(N) ->
-    lists:reverse(Avps, [A | Acc]);
-
-%% An unindexed AVP.
-reorder([H | T], Acc) ->
-    reorder(T, [H | Acc]);
-
-%% No indexed members.
-reorder([], _) ->
-    false.
-
 %% encode_avps/2
 
 encode_avps(Avps, Opts) ->
@@ -327,13 +288,7 @@ decode(Mod, AppMod, Opts, Pkt) ->
 %% 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} ->
-            Pkt#diameter_packet{avps = As,
-                                errors = [E]};
-        As ->
-            Pkt#diameter_packet{avps = As}
-    end;
+    collect_avps(Pkt);
 
 %% Otherwise decode using the dictionary.
 decode(_, Mod, AppMod, Opts, #diameter_packet{header = Hdr} = Pkt) ->
@@ -342,35 +297,31 @@ decode(_, Mod, AppMod, Opts, #diameter_packet{header = Hdr} = Pkt) ->
                      is_error = IsError}
         = Hdr,
 
-    MsgName = if IsError andalso not IsRequest ->
+    MsgName = if IsError, not IsRequest ->
                       'answer-message';
                  true ->
                       Mod:msg_name(CmdCode, IsRequest)
               end,
 
-    decode_avps(MsgName, Mod, AppMod, Opts, Pkt, collect_avps(Pkt));
+    decode_avps(MsgName, Mod, AppMod, Opts, Pkt);
 
 decode(Id, Mod, AppMod, Opts, Bin)
   when is_binary(Bin) ->
     decode(Id, Mod, AppMod, Opts, #diameter_packet{header = decode_header(Bin),
                                                    bin = Bin}).
 
-%% decode_avps/6
+%% decode_avps/5
 
-decode_avps(MsgName, Mod, AppMod, Opts, Pkt, {E, Avps}) ->
-    ?LOG(invalid_avp_length, Pkt#diameter_packet.header),
-    #diameter_packet{errors = Failed}
-        = P
-        = decode_avps(MsgName, Mod, AppMod, Opts, Pkt, Avps),
-    P#diameter_packet{errors = [E | Failed]};
-
-decode_avps('', _, _, _, Pkt, Avps) ->  %% unknown message ...
-    ?LOG(unknown_message, Pkt#diameter_packet.header),
-    Pkt#diameter_packet{avps = lists:reverse(Avps),
-                        errors = [3001]};   %% DIAMETER_COMMAND_UNSUPPORTED
+decode_avps('', _, _, _, #diameter_packet{header = H,  %% unknown message
+                                          bin = Bin}
+                         = Pkt) ->
+    ?LOG(unknown_message, H),
+    Pkt#diameter_packet{avps = collect_avps(Bin),
+                        errors = [3001]}; %% DIAMETER_COMMAND_UNSUPPORTED
 %% msg = undefined identifies this case.
 
-decode_avps(MsgName, Mod, AppMod, Opts, Pkt, Avps) ->  %% ... or not
+decode_avps(MsgName, Mod, AppMod, Opts, #diameter_packet{bin = Bin} = Pkt) ->
+    {_, Avps} = split_binary(Bin, 20),
     {Rec, As, Errors} = Mod:decode_avps(MsgName,
                                         Avps,
                                         Opts#{dictionary => AppMod,
@@ -380,6 +331,8 @@ decode_avps(MsgName, Mod, AppMod, Opts, Pkt, Avps) ->  %% ... or not
                         errors = Errors,
                         avps = As}.
 
+%% reformat/3
+
 reformat(MsgName, Avps, #{decode_format := T})
   when T == map;
        T == list ->
@@ -524,24 +477,21 @@ msg_id(<<_:32, Rbit:1, _:7, CmdCode:24, ApplId:32, _/binary>>) ->
 %%% # collect_avps/1
 %%% ---------------------------------------------------------------------------
 
-%% Note that the returned list of AVP's is reversed relative to their
-%% order in the binary. Note also that grouped avp's aren't unraveled,
-%% only those at the top level.
+%% This is only used for the relay decode. Note that grouped avp's
+%% aren't unraveled, only those at the top level.
 
--spec collect_avps(#diameter_packet{} | binary())
-   -> [Avp]
-    | {Error, [Avp]}
- when Avp   :: #diameter_avp{},
-      Error :: {5014, #diameter_avp{}}.
+-spec collect_avps(#diameter_packet{})
+   -> #diameter_packet{};
+                  (binary())
+   -> [#diameter_avp{}].
 
-collect_avps(#diameter_packet{bin = <<_:20/binary, Avps/binary>>}) ->
-    collect_avps(Avps, 0, []);
+collect_avps(#diameter_packet{bin = Bin} = Pkt) ->
+    Pkt#diameter_packet{avps = collect_avps(Bin)};
 
-collect_avps(Bin)
-  when is_binary(Bin) ->
-    collect_avps(Bin, 0, []).
+collect_avps(<<_:20/binary, Avps/binary>>) ->
+    collect(Avps).
 
-%% collect_avps/3
+%% collect/1
 
 %%     0                   1                   2                   3
 %%     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
@@ -555,66 +505,48 @@ collect_avps(Bin)
 %%    |    Data ...
 %%    +-+-+-+-+-+-+-+-+
 
-collect_avps(<<Code:32, V:1, M:1, P:1, _:5, Len:24, I:V/unit:32, Rest/binary>>,
-             N,
-             Acc) ->
-    collect_avps(Code,
-                 if 1 == V -> I; 0 == V -> undefined end,
-                 1 == M,
-                 1 == P,
-                 Len - 8 - V*4,  %% Might be negative, which ensures
-                 ?PAD(Len),      %%   failure of the Data match below.
-                 Rest,
-                 N,
-                 Acc);
-
-collect_avps(<<>>, _, Acc) ->
-    Acc;
+collect(<<Code:32, V:1, M:1, P:1, _:5, Len:24, I:V/unit:32, Rest/binary>>) ->
+    collect(Rest,
+            Code,
+            if 1 == V -> I; 0 == V -> undefined end,
+            Len - 8 - V*4,  %% Might be negative, which ensures
+            ?PAD(Len),      %%   failure of the match below.
+            1 == M,
+            1 == P);
+
+collect(<<>>) ->
+    [];
 
 %% Header is truncated. pack_avp/1 will pad this at encode if sent in
 %% a Failed-AVP.
-collect_avps(Bin, _, Acc) ->
-    {{5014, #diameter_avp{data = Bin}}, Acc}.
-
-%% collect_avps/9
+collect(Bin) ->
+    [#diameter_avp{data = {5014, Bin}}].
 
-%% Duplicate the diameter_avp creation in each branch below to avoid
-%% modifying the record, which profiling has shown to be a relatively
-%% costly part of building the list.
+%% collect/7
 
-collect_avps(Code, VendorId, M, P, Len, Pad, Rest, N, Acc) ->
-    case Rest of
-        <<Data:Len/binary, _:Pad/binary, T/binary>> ->
+collect(Bin, Code, Vid, DataLen, Pad, M, P) ->
+    case Bin of
+        <<Data:DataLen/binary, _:Pad/binary, Rest/binary>> ->
             Avp = #diameter_avp{code = Code,
-                                vendor_id = VendorId,
+                                vendor_id = Vid,
                                 is_mandatory = M,
                                 need_encryption = P,
-                                data = Data,
-                                index = N},
-            collect_avps(T, N+1, [Avp | Acc]);
+                                data = Data},
+            [Avp | collect(Rest)];
         _ ->
             %% Length in header points past the end of the message, or
-            %% doesn't span the header. As stated in the 6733 text
-            %% above, it's sufficient to return a zero-filled minimal
-            %% payload if this is a request. Do this (in cases that we
-            %% know the type) by inducing a decode failure and letting
-            %% the dictionary's decode (in diameter_gen) deal with it.
-            %%
-            %% Note that the extra bit can only occur in the trailing
-            %% AVP of a message or Grouped AVP, since a faulty AVP
-            %% Length is otherwise indistinguishable from a correct
-            %% one here, as we don't know the types of the AVPs being
-            %% extracted.
-            Avp = #diameter_avp{code = Code,
-                                vendor_id = VendorId,
-                                is_mandatory = M,
-                                need_encryption = P,
-                                data = {5014, Rest},
-                                index = N},
-            [Avp | Acc]
+            %% doesn't span the header. Note that an length error can
+            %% only occur in the trailing AVP of a message or Grouped
+            %% AVP, since a faulty AVP Length is otherwise
+            %% indistinguishable from a correct one here, as we don't
+            %% know the types of the AVPs being extracted.
+            [#diameter_avp{code = Code,
+                           vendor_id = Vid,
+                           is_mandatory = M,
+                           need_encryption = P,
+                           data = {5014, Bin}}]
     end.
 
-
 %% 3588:
 %%
 %%   DIAMETER_INVALID_AVP_LENGTH        5014
diff --git a/lib/diameter/src/base/diameter_config.erl b/lib/diameter/src/base/diameter_config.erl
index 2b069f40cc..f1b6e56782 100644
--- a/lib/diameter/src/base/diameter_config.erl
+++ b/lib/diameter/src/base/diameter_config.erl
@@ -715,6 +715,7 @@ make_config(SvcName, Opts) ->
                          {true, strict_arities},
                          {true, strict_mbit},
                          {record, decode_format},
+                         {true, traffic_counters},
                          {true, string_decode},
                          {[], spawn_opt}]),
 
@@ -760,6 +761,7 @@ opt(K, false = B)
        K == strict_arities;
        K == strict_mbit;
        K == decode_format;
+       K == traffic_counters;
        K == string_decode ->
     B;
 
@@ -768,6 +770,7 @@ opt(K, true = B)
        K == use_shared_peers;
        K == strict_arities;
        K == strict_mbit;
+       K == traffic_counters;
        K == string_decode ->
     B;
 
diff --git a/lib/diameter/src/base/diameter_gen.erl b/lib/diameter/src/base/diameter_gen.erl
index 3d0612c294..7a1a46ec52 100644
--- a/lib/diameter/src/base/diameter_gen.erl
+++ b/lib/diameter/src/base/diameter_gen.erl
@@ -26,6 +26,14 @@
 
 -module(diameter_gen).
 
+-compile({inline, [incr/8,
+                   incr/4,
+                   field/1,
+                   setopts/4,
+                   avp_arity/5,
+                   set_failed/2,
+                   set_strict/3]}).
+
 -export([encode_avps/3,
          decode_avps/3,
          grouped_avp/4,
@@ -60,8 +68,9 @@
     | no_return().
 
 encode_avps(Name, Vals, #{module := Mod} = Opts) ->
+    Strict = mget(strict_arities, Opts, encode),
     try
-        encode(Name, Vals, Opts, Mod)
+        encode(Name, Vals, Opts, Strict, Mod)
     catch
         throw: {?MODULE, Reason} ->
             diameter_lib:log({encode, error},
@@ -78,87 +87,88 @@ encode_avps(Name, Vals, #{module := Mod} = Opts) ->
             erlang:error({encode_failure, Reason, Name, Stack})
     end.
 
-%% encode/4
-
-encode(Name, Vals, #{ordered_encode := false} = Opts, Mod)
-  when is_list(Vals) ->
-    lists:map(fun({F,V}) -> encode(Name, F, V, Opts, Mod) end, Vals);
+%% encode/5
 
-encode(Name, Vals, Opts, Mod)
+encode(Name, Vals, Opts, Strict, Mod)
   when is_list(Vals) ->
-    encode(Name, Mod:'#set-'(Vals, newrec(Mod, Name)), Opts, Mod);
+    case Opts of
+        #{ordered_encode := false} ->
+            lists:map(fun({F,V}) -> encode(Name, F, V, Opts, Strict, Mod) end,
+                      Vals);
+        _ ->
+            Rec = Mod:'#set-'(Vals, newrec(Mod, Name)),
+            encode(Name, Rec, Opts, Strict, Mod)
+    end;
 
-encode(Name, Map, Opts, Mod)
+encode(Name, Map, Opts, Strict, Mod)
   when is_map(Map) ->
-    [enc(Name, F, A, V, Opts, Mod) || {F,A} <- Mod:avp_arity(Name),
-                                      V <- [maps:get(F, Map, undefined)]];
+    [enc(Name, F, A, V, Opts, Strict, Mod) || {F,A} <- Mod:avp_arity(Name),
+                                              V <- [mget(F, Map, undefined)]];
 
-encode(Name, Rec, Opts, Mod) ->
-    [encode(Name, F, V, Opts, Mod) || {F,V} <- Mod:'#get-'(Rec)].
+encode(Name, Rec, Opts, Strict, Mod) ->
+    [encode(Name, F, V, Opts, Strict, Mod) || {F,V} <- Mod:'#get-'(Rec)].
 
-%% encode/5
+%% encode/6
 
-encode(Name, AvpName, Values, #{strict_arities := T} = Opts, Mod)
-  when T /= encode ->
-    enc(Name, AvpName, ?ANY, Values, Opts, Mod);
+encode(Name, AvpName, Values, Opts, Strict, Mod)
+  when Strict /= encode ->
+    enc(Name, AvpName, ?ANY, Values, Opts, Strict, Mod);
 
-encode(Name, AvpName, Values, Opts, Mod) ->
-    enc(Name, AvpName, Mod:avp_arity(Name, AvpName), Values, Opts, Mod).
+encode(Name, AvpName, Values, Opts, Strict, Mod) ->
+    Arity = Mod:avp_arity(Name, AvpName),
+    enc(Name, AvpName, Arity, Values, Opts, Strict, Mod).
 
-%% enc/6
+%% enc/7
 
-enc(Name, AvpName, Arity, Values, #{strict_arities := T} = Opts, Mod)
-  when T /= encode, Arity /= ?ANY ->
-    enc(Name, AvpName, ?ANY, Values, Opts, Mod);
+enc(Name, AvpName, Arity, Values, Opts, Strict, Mod)
+  when Strict /= encode, Arity /= ?ANY ->
+    enc(Name, AvpName, ?ANY, Values, Opts, Strict, Mod);
 
-enc(_, AvpName, 1, undefined, _, _) ->
+enc(_, AvpName, 1, undefined, _, _, _) ->
     ?THROW([mandatory_avp_missing, AvpName]);
 
-enc(Name, AvpName, 1, Value, Opts, Mod) ->
+enc(Name, AvpName, 1, Value, Opts, _, Mod) ->
     H = avp_header(AvpName, Mod),
     enc1(Name, AvpName, H, Value, Opts, Mod);
 
-enc(_, _, {0,_}, [], _, _) ->
+enc(_, _, {0,_}, [], _, _, _) ->
     [];
 
-enc(_, _, _, undefined, _, _) ->
+enc(_, _, _, undefined, _, _, _) ->
     [];
 
 %% Be forgiving when a list of values is expected. If the value itself
 %% is a list then the user has to wrap it to avoid each member from
 %% being interpreted as an individual AVP value.
-enc(Name, AvpName, Arity, V, Opts, Mod)
+enc(Name, AvpName, Arity, V, Opts, Strict, Mod)
   when not is_list(V) ->
-    enc(Name, AvpName, Arity, [V], Opts, Mod);
+    enc(Name, AvpName, Arity, [V], Opts, Strict, Mod);
 
-enc(Name, AvpName, {Min, Max}, Values, Opts, Mod) ->
+enc(Name, AvpName, {Min, Max}, Values, Opts, Strict, Mod) ->
     H = avp_header(AvpName, Mod),
-    enc(Name, AvpName, H, Min, 0, Max, Values, Opts, Mod).
-
-%% enc/9
+    enc(Name, AvpName, H, Min, 0, Max, Values, Opts, Strict, Mod).
 
-enc(Name, AvpName, H, Min, N, '*', Vs, Opts, Mod)
-  when Min =< N ->
-    [enc1(Name, AvpName, H, V, Opts, Mod) || V <- Vs];
+%% enc/10
 
-enc(Name, AvpName, H, _, _, _, Vs, #{strict_arities := T} = Opts, Mod)
-  when T /= encode ->
+enc(Name, AvpName, H, Min, N, Max, Vs, Opts, Strict, Mod)
+  when Strict /= encode;
+       Max == '*', Min =< N ->
     [enc1(Name, AvpName, H, V, Opts, Mod) || V <- Vs];
 
-enc(_, AvpName, _, Min, N, _, [], _, _)
+enc(_, AvpName, _, Min, N, _, [], _, _, _)
   when N < Min ->
     ?THROW([repeated_avp_insufficient_arity, AvpName, Min, N]);
 
-enc(_, _, _, _, _, _, [], _, _) ->
+enc(_, _, _, _, _, _, [], _, _, _) ->
     [];
 
-enc(_, AvpName, _, _, N, Max, _, _, _)
+enc(_, AvpName, _, _, N, Max, _, _, _, _)
   when Max =< N ->
     ?THROW([repeated_avp_excessive_arity, AvpName, Max]);
 
-enc(Name, AvpName, H, Min, N, Max, [V|Vs], Opts, Mod) ->
+enc(Name, AvpName, H, Min, N, Max, [V|Vs], Opts, Strict, Mod) ->
     [enc1(Name, AvpName, H, V, Opts, Mod)
-     | enc(Name, AvpName, H, Min, N+1, Max, Vs, Opts, Mod)].
+     | enc(Name, AvpName, H, Min, N+1, Max, Vs, Opts, Strict, Mod)].
 
 %% avp_header/2
 
@@ -221,115 +231,186 @@ enc(AvpName, Value, Opts, Mod) ->
 %% # decode_avps/3
 %% ---------------------------------------------------------------------------
 
--spec decode_avps(parent_name(), [#diameter_avp{}], map())
+-spec decode_avps(parent_name(), binary(), map())
    -> {parent_record(), [avp()], Failed}
  when Failed :: [{5000..5999, #diameter_avp{}}].
 
-decode_avps(Name, Recs, #{module := Mod, decode_format := Fmt} = Opts) ->
-    {Avps, {Rec, AM, Failed}}
-        = mapfoldl(fun(T,A) -> decode(Name, Opts, Mod, T, A) end,
-                   {newrec(Fmt, Mod, Name, Opts), #{}, []},
-                   Recs),
-    %% AM counts the number of top-level AVPs, which arities/5 then
-    %% uses when adding 500[59] errors.
-    Arities = Mod:avp_arity(Name),
-    {reformat(Name, Rec, Arities, Mod, Opts, Fmt),
+decode_avps(Name, Bin, #{module := Mod, decode_format := Fmt} = Opts) ->
+    Strict = mget(strict_arities, Opts, decode),
+    [AM, Avps, Failed | Rec]
+        = decode(Bin, Name, Mod, Fmt, Strict, Opts, #{}),
+    %% AM counts the number of top-level AVPs, which missing/5 then
+    %% uses when appending 5005 errors.
+    {reformat(Name, Rec, Strict, Mod, Fmt),
      Avps,
-     Failed ++ arities(Arities, Opts, Mod, AM, Avps)}.
+     Failed ++ missing(Name, Strict, Mod, Opts, AM)}.
 
 %% Append arity errors so that errors are reported in the order
 %% encountered. Failed-AVP should typically contain the first
 %% error encountered.
 
-%% mapfoldl/3
-%%
-%% Like lists:mapfoldl/3, but don't reverse the list.
+%% decode/7
 
-mapfoldl(F, Acc, List) ->
-    mapfoldl(F, Acc, List, []).
+decode(<<Code:32, V:1, M:1, P:1, _:5, Len:24, I:V/unit:32, Rest/binary>>,
+       Name,
+       Mod,
+       Fmt,
+       Strict,
+       Opts,
+       AM) ->
+    decode(Rest,
+           Code,
+           if 1 == V -> I; true -> undefined end,
+           Len - 8 - 4*V, %% possibly negative, causing case match to fail
+           (4 - (Len rem 4)) rem 4,
+           1 == M,
+           1 == P,
+           Name,
+           Mod,
+           Fmt,
+           Strict,
+           Opts,
+           AM);
+
+decode(<<>>, Name, Mod, Fmt, Strict, _, AM) ->
+    [AM, [], [] | newrec(Fmt, Mod, Name, Strict)];
+
+decode(Bin, Name, Mod, Fmt, Strict, _, AM) ->
+    Avp = #diameter_avp{data = Bin},
+    [AM, [Avp], [{5014, Avp}] | newrec(Fmt, Mod, Name, Strict)].
+
+%% decode/13
+
+decode(Bin, Code, Vid, DataLen, Pad, M, P, Name, Mod, Fmt, Strict, Opts0, AM0) ->
+    case Bin of
+        <<Data:DataLen/binary, _:Pad/binary, T/binary>> ->
+            {NameT, AvpName, Arity, {Idx, AM}}
+                = incr(Name, Code, Vid, M, Mod, Strict, Opts0, AM0),
+
+            Opts = setopts(NameT, Name, M, Opts0),
+            %% Not AvpName or else a failed Failed-AVP
+            %% decode is packed into 'AVP'.
+
+            Avp = #diameter_avp{code = Code,
+                                vendor_id = Vid,
+                                is_mandatory = M,
+                                need_encryption = P,
+                                data = Data,
+                                name = name(NameT),
+                                type = type(NameT),
+                                index = Idx},
+
+            Dec = decode(Data, Name, NameT, Mod, Opts, Avp),    %% decode
+            Acc = decode(T, Name, Mod, Fmt, Strict, Opts, AM),  %% recurse
+            acc(Acc, Dec, Name, AvpName, Arity, Strict, Mod, Opts);
+        _ ->
+            {NameT, _AvpName, _Arity, {Idx, AM}}
+                = incr(Name, Code, Vid, M, Mod, Strict, Opts0, AM0),
+
+            Avp = #diameter_avp{code = Code,
+                                vendor_id = Vid,
+                                is_mandatory = M,
+                                need_encryption = P,
+                                data = Bin,
+                                name = name(NameT),
+                                type = type(NameT),
+                                index = Idx},
+
+            [AM, [Avp], [{5014, Avp}] | newrec(Fmt, Mod, Name, Strict)]
+    end.
 
-mapfoldl(F, Acc0, [T|Rest], List) ->
-    {B, Acc} = F(T, Acc0),
-    mapfoldl(F, Acc, Rest, [B|List]);
-mapfoldl(_, Acc, [], List) ->
-    {List, Acc}.
+%% incr/8
 
-%% 3588/6733:
-%%
-%%   DIAMETER_MISSING_AVP               5005
-%%      The request did not contain an AVP that is required by the Command
-%%      Code definition.  If this value is sent in the Result-Code AVP, a
-%%      Failed-AVP AVP SHOULD be included in the message.  The Failed-AVP
-%%      AVP MUST contain an example of the missing AVP complete with the
-%%      Vendor-Id if applicable.  The value field of the missing AVP
-%%      should be of correct minimum length and contain zeros.
+incr(Name, Code, Vid, M, Mod, Strict, Opts, AM0) ->
+    NameT = Mod:avp_name(Code, Vid), %% {AvpName, Type} | 'AVP'
+    AvpName = field(NameT),
+    Arity = avp_arity(Name, AvpName, Mod, Opts, M),
+    {NameT, AvpName, Arity, incr(AvpName, Arity, Strict, AM0)}.
+
+%% Data is a truncated header if command_code = undefined, otherwise
+%% payload bytes. The former is padded to the length of a header if
+%% the AVP reaches an outgoing encode.
 %%
-%%   DIAMETER_AVP_OCCURS_TOO_MANY_TIMES 5009
-%%      A message was received that included an AVP that appeared more
-%%      often than permitted in the message definition.  The Failed-AVP
-%%      AVP MUST be included and contain a copy of the first instance of
-%%      the offending AVP that exceeded the maximum number of occurrences
+%% RFC 6733 says that an AVP returned with 5014 can contain a minimal
+%% payload for the AVP's type, but don't always know the type.
 
-%% arities/5
+setopts('AVP', _, _, Opts) ->
+    Opts;
 
-arities(_, #{strict_arities := T}, _, _, _)
-  when T /= decode ->
-    [];
+setopts({_, Type}, Name, M, Opts) ->
+    set_failed(Name, set_strict(Type, M, Opts)).
 
-arities(Arities, Opts, Mod, AM, Avps) ->
-    [Count, Map | More]
-        = lists:foldl(fun({N,T}, A) -> more(N, T, Opts, Mod, AM, A) end,
-                      [0, #{}],
-                      Arities),
-    less(Count, Map, Avps) ++ lists:reverse(More).
+%% incr/4
 
-%% more/6
+incr(F, A, SA, AM)
+  when F == 'AVP';
+       A == ?ANY;
+       A == 0;
+       SA /= decode ->
+    {undefined, AM};
 
-more(_Name, ?ANY, _Opts, _Mod, _AM, Acc) ->
-    Acc;
+incr(AvpName, _, _, AM) ->
+    case AM of
+        #{AvpName := N} ->
+            {N, AM#{AvpName => N+1}};
+        _ ->
+            {0, AM#{AvpName => 1}}
+    end.
 
-more(Name, {Mn, Mx}, Opts, Mod, AM, Acc) ->
-    more(Name, Mn, Mx, Opts, Mod, AM, Acc);
+%% mget/3
+%%
+%% Measurably faster than maps:get/3.
 
-more(Name, 1, Opts, Mod, AM, Acc) ->
-    more(Name, 1, 1, Opts, Mod, AM, Acc).
+mget(Key, Map, Def) ->
+    case Map of
+        #{Key := V} ->
+            V;
+        _ ->
+            Def
+    end.
 
-%% more/7
+%% name/1
 
-more(Name, Mn, Mx, Opts, Mod, AM, Acc) ->
-    macc(Name, Mn, maps:get(Name, AM, 0), Mx, Opts, Mod, Acc).
+name({Name, _}) ->
+    Name;
+name(_) ->
+    undefined.
 
-%% macc/7
+%% type/1
 
-macc(Name, Mn, N, _, Opts, Mod, [M, Map | T])
-  when N < Mn ->
-    [M, Map, {5005, empty_avp(Name, Opts, Mod)} | T];
+type({_, Type}) ->
+    Type;
+type(_) ->
+    undefined.
 
-macc(Name, _, N, Mx, _Opts, _Mod, [M, Map | T])
-  when Mx < N ->
-    K = N - Mx,
-    [M + K, maps:put(Name, K, Map) | T];
+%% missing/5
 
-macc(_Name, _, _, _, _Opts, _Mod, Acc) ->
-    Acc.
+missing(Name, decode, Mod, Opts, AM) ->
+    [{5005, empty_avp(N, Opts, Mod)} || {N,A} <- Mod:avp_arity(Name),
+                                        N /= 'AVP',
+                                        Mn <- [min_arity(A)],
+                                        0 < Mn,
+                                        mget(N, AM, 0) < Mn];
 
-%% less/3
+missing(_, _, _, _, _) ->
+    [].
 
-less(0, _, _) ->
-    [];
+%% 3588/6733:
+%%
+%%   DIAMETER_MISSING_AVP               5005
+%%      The request did not contain an AVP that is required by the Command
+%%      Code definition.  If this value is sent in the Result-Code AVP, a
+%%      Failed-AVP AVP SHOULD be included in the message.  The Failed-AVP
+%%      AVP MUST contain an example of the missing AVP complete with the
+%%      Vendor-Id if applicable.  The value field of the missing AVP
+%%      should be of correct minimum length and contain zeros.
 
-less(N, Map, [#diameter_avp{name = undefined} | Avps]) ->
-    less(N, Map, Avps);
+%% min_arity/1
 
-less(N, Map, [#diameter_avp{name = Name} = Avp | Avps]) ->
-    case Map of
-        #{Name := 0} ->
-            [{5009, Avp} | less(N-1, Map, Avps)];
-        #{Name := M} ->
-            less(N, maps:put(Name, M-1, Map), Avps);
-        _ ->
-            less(N, Map, Avps)
-    end.
+min_arity(1) ->
+    1;
+min_arity({Mn,_}) ->
+    Mn.
 
 %% empty_avp/3
 
@@ -356,55 +437,18 @@ empty_avp(Name, Opts, Mod) ->
 %%   specific errors that can be described by this AVP are described in
 %%   the following section.
 
-%% decode/5
-
-decode(Name, Opts, Mod, Avp, Acc) ->
-    #diameter_avp{code = Code, vendor_id = Vid}
-        = Avp,
-    N = Mod:avp_name(Code, Vid),
-    case Opts of
-        #{strict_arities := T} when T /= decode ->
-            decode(Name, Opts, Mod, N, ?ANY, Avp, Acc);
-        _ ->
-            {Rec, AM, Failed} = Acc,
-            F = field(N),
-            A = Mod:avp_arity(Name, F),
-            decode(Name, Opts, Mod, N, A, Avp, {Rec,
-                                                incr(field(F, A), AM),
-                                                Failed})
-    end.
-
 %% field/1
 
 field({AvpName, _}) ->
     AvpName;
-
 field(_) ->
     'AVP'.
 
-%% field/2
-
-field(_, 0) ->
-    'AVP';
-
-field(F, _) ->
-    F.
-
-%% incr/2
-
-incr(Key, Map) ->
-    maps:update_with(Key, fun incr/1, 1, Map).
-
-%% incr/1
-
-incr(N) ->
-    N + 1.
-
-%% decode/7
+%% decode/6
 
 %% AVP not in dictionary.
-decode(Name, Opts, Mod, 'AVP', Arity, Avp, Acc) ->
-    decode_AVP(Name, Arity, Avp, Opts, Mod, Acc);
+decode(_Data, _Name, 'AVP', _Mod, _Opts, Avp) ->
+    Avp;
 
 %% 6733, 4.4:
 %%
@@ -453,20 +497,9 @@ decode(Name, Opts, Mod, 'AVP', Arity, Avp, Acc) ->
 %% defined the RFC's "unrecognized", which is slightly stronger than
 %% "not defined".)
 
-decode(Name, Opts0, Mod, {AvpName, Type}, Arity, Avp, Acc) ->
-    #diameter_avp{data = Data, is_mandatory = M}
-        = Avp,
-
-    %% Whether or not to ignore an M-bit on an encapsulated AVP, or on
-    %% all AVPs with the service_opt() strict_mbit.
-    Opts1 = set_strict(Type, M, Opts0),
-
-    %% Whether or not we're decoding within Failed-AVP and should
-    %% ignore decode errors.
+decode(Data, Name, {AvpName, Type}, Mod, Opts, Avp) ->
     #{dictionary := AppMod, failed_avp := Failed}
-        = Opts
-        = set_failed(Name, Opts1), %% Not AvpName or else a failed Failed-AVP
-                                   %% decode is packed into 'AVP'.
+        = Opts,
 
     %% Reset the dictionary for best-effort decode of Failed-AVP.
     DecMod = if Failed -> AppMod;
@@ -479,103 +512,55 @@ decode(Name, Opts0, Mod, {AvpName, Type}, Arity, Avp, Acc) ->
 
     try avp_decode(Data, AvpName, Opts, DecMod, Mod) of
         {Rec, As} when Type == 'Grouped' ->
-            A = Avp#diameter_avp{name = AvpName,
-                                 value = Rec,
-                                 type = Type},
-            {[A|As], pack_avp(Name, Arity, A, Opts, Mod, Acc)};
-
+            A = Avp#diameter_avp{value = Rec},
+            [A | As];
         V when Type /= 'Grouped' ->
-            A = Avp#diameter_avp{name = AvpName,
-                                 value = V,
-                                 type = Type},
-            {A, pack_avp(Name, Arity, A, Opts, Mod, Acc)}
+            Avp#diameter_avp{value = V}
     catch
-        throw: {?MODULE, {grouped, Error, ComponentAvps}} ->
-            decode_error(Name,
-                         Error,
-                         ComponentAvps,
-                         Opts,
-                         Mod,
-                         Avp#diameter_avp{name = AvpName,
-                                          data = trim(Avp#diameter_avp.data),
-                                          type = Type},
-                         Acc);
-
+        throw: {?MODULE, T} ->
+            decode_error(Failed, T, Avp);
         error: Reason ->
-            decode_error(Name,
-                         Reason,
-                         Opts,
-                         Mod,
-                         Avp#diameter_avp{name = AvpName,
-                                          data = trim(Avp#diameter_avp.data),
-                                          type = Type},
-                         Acc)
+            decode_error(Failed, Reason, Name, Mod, Opts, Avp)
     end.
 
-%% avp_decode/5
-
-avp_decode(Data, AvpName, Opts, Mod, Mod) ->
-    Mod:avp(decode, Data, AvpName, Opts);
-
-avp_decode(Data, AvpName, Opts, Mod, _) ->
-    Mod:avp(decode, Data, AvpName, Opts, Mod).
-
-%% trim/1
+%% decode_error/3
 %%
-%% Remove any extra bit that was added in diameter_codec to induce a
-%% 5014 error.
-
-trim(#diameter_avp{data = Data} = Avp) ->
-    Avp#diameter_avp{data = trim(Data)};
-
-trim({5014, Bin}) ->
-    Bin;
-
-trim(Avps)
-  when is_list(Avps) ->
-    lists:map(fun trim/1, Avps);
+%% Error when decoding a grouped AVP.
 
-trim(Avp) ->
-    Avp.
+decode_error(true, {Rec, _, _}, Avp) ->
+    Avp#diameter_avp{value = Rec};
 
-%% decode_error/7
-
-decode_error(Name, [_|Rec], _, #{failed_avp := true} = Opts, Mod, Avp, Acc) ->
-    decode_AVP(Name, Avp#diameter_avp{value = Rec}, Opts, Mod, Acc);
-
-decode_error(Name, _, _, #{failed_avp := true} = Opts, Mod, Avp, Acc) ->
-    decode_AVP(Name, Avp, Opts, Mod, Acc);
-
-decode_error(_, [Error | _], ComponentAvps, _, _, Avp, Acc) ->
-    decode_error(Error, Avp, Acc, ComponentAvps);
-
-decode_error(_, Error, ComponentAvps, _, _, Avp, Acc) ->
-    decode_error(Error, Avp, Acc, ComponentAvps).
+decode_error(false, {_, ComponentAvps, [{RC,A} | _]}, Avp) ->
+    {RC, [Avp | ComponentAvps], Avp#diameter_avp{data = [A]}}.
 
 %% decode_error/6
+%%
+%% Error when decoding a non-grouped AVP.
 
-decode_error(Name, _Reason, #{failed_avp := true} = Opts, Mod, Avp, Acc) ->
-    decode_AVP(Name, Avp, Opts, Mod, Acc);
+decode_error(true, _, _, _, _, Avp) ->
+    Avp;
 
-decode_error(Name, Reason, Opts, Mod, Avp, {Rec, AM, Failed}) ->
+decode_error(false, Reason, Name, Mod, Opts, Avp) ->
     Stack = diameter_lib:get_stacktrace(),
-    AvpName = Avp#diameter_avp.name,
     diameter_lib:log(decode_error,
                      ?MODULE,
                      ?LINE,
-                     {Reason, Name, AvpName, Mod, Stack}),
-    {Avp, {Rec, AM, [rc(Reason, Avp, Opts, Mod) | Failed]}}.
+                     {Reason, Name, Avp#diameter_avp.name, Mod, Stack}),
+    rc(Reason, Avp, Opts, Mod).
 
-%% decode_error/4
+%% avp_decode/5
 
-decode_error({RC, ErrorData}, Avp, {Rec, AM, Failed}, ComponentAvps) ->
-    E = Avp#diameter_avp{data = [ErrorData]},
-    {[Avp | trim(ComponentAvps)], {Rec, AM, [{RC, E} | Failed]}}.
+avp_decode(Data, AvpName, Opts, Mod, Mod) ->
+    Mod:avp(decode, Data, AvpName, Opts);
 
-%% set_strict/3
+avp_decode(Data, AvpName, Opts, Mod, _) ->
+    Mod:avp(decode, Data, AvpName, Opts, Mod).
 
+%% set_strict/3
+%%
 %% Set false as soon as we see a Grouped AVP that doesn't set the
 %% M-bit, to ignore the M-bit on an encapsulated AVP.
+
 set_strict('Grouped', false = M, #{strict_mbit := true} = Opts) ->
     Opts#{strict_mbit := M};
 set_strict(_, _, Opts) ->
@@ -592,86 +577,82 @@ set_failed('Failed-AVP', #{failed_avp := false} = Opts) ->
 set_failed(_, Opts) ->
     Opts.
 
-%% decode_AVP/5
-%%
-%% Don't know this AVP: see if it can be packed in an 'AVP' field
-%% undecoded. Note that the type field is 'undefined' in this case.
-
-decode_AVP(Name, Avp, #{strict_arities := T} = Opts, Mod, Acc)
-  when T /= decode ->
-    decode_AVP(Name, ?ANY, Avp, Opts, Mod, Acc);
-
-decode_AVP(Name, Avp, Opts, Mod, Acc) ->
-    decode_AVP(Name, Mod:avp_arity(Name, 'AVP'), Avp, Opts, Mod, Acc).
-
-%% decode_AVP/6
-
-decode_AVP(Name, Arity, Avp, Opts, Mod, Acc) ->
-    {trim(Avp), pack_AVP(Name, Arity, Avp, Opts, Mod, Acc)}.
-
-%% rc/2
-
-%% diameter_types will raise an error of this form to communicate
-%% DIAMETER_INVALID_AVP_LENGTH (5014). A module specified to a
-%% @custom_types tag in a dictionary file can also raise an error of
-%% this form.
-rc({'DIAMETER', 5014 = RC, _}, #diameter_avp{name = AvpName} = A, Opts, Mod) ->
-    {RC, A#diameter_avp{data = Mod:empty_value(AvpName, Opts)}};
+%% acc/8
+
+acc([AM | Acc], As, Name, AvpName, Arity, Strict, Mod, Opts) ->
+    [AM | acc1(Acc, As, Name, AvpName, Arity, Strict, Mod, Opts)].
+
+%% acc1/8
+
+%% Faulty AVP, not grouped.
+acc1(Acc, {_RC, Avp} = E, _, _, _, _, _, _) ->
+    [Avps, Failed | Rec] = Acc,
+    [[Avp | Avps], [E | Failed] | Rec];
+
+%% Faulty component in grouped AVP.
+acc1(Acc, {RC, As, Avp}, _, _, _, _, _, _) ->
+    [Avps, Failed | Rec] = Acc,
+    [[As | Avps], [{RC, Avp} | Failed] | Rec];
+
+%% Grouped AVP ...
+acc1([Avps | Acc], [Avp|_] = As, Name, AvpName, Arity, Strict, Mod, Opts) ->
+    [[As|Avps] | acc2(Acc, Avp, Name, AvpName, Arity, Strict, Mod, Opts)];
+
+%% ... or not.
+acc1([Avps | Acc], Avp, Name, AvpName, Arity, Strict, Mod, Opts) ->
+    [[Avp|Avps] | acc2(Acc, Avp, Name, AvpName, Arity, Strict, Mod, Opts)].
+
+%% acc2/8
+
+%% No errors, but nowhere to pack.
+acc2(Acc, Avp, _, 'AVP', 0, _, _, _) ->
+    [Failed | Rec] = Acc,
+    [[{rc(Avp), Avp} | Failed] | Rec];
+
+%% No AVP of this name: try to pack as 'AVP'.
+acc2(Acc, Avp, Name, AvpName, 0, Strict, Mod, Opts) ->
+    M = Avp#diameter_avp.is_mandatory,
+    Arity = pack_arity(Name, AvpName, Opts, Mod, M),
+    acc2(Acc, Avp, Name, 'AVP', Arity, Strict, Mod, Opts);
+
+%% Relaxed arities.
+acc2(Acc, Avp, _, AvpName, Arity, Strict, Mod, _)
+  when Strict /= decode ->
+    pack(Arity, AvpName, Avp, Mod, Acc);
+
+%% No maximum arity.
+acc2(Acc, Avp, _, AvpName, {_,'*'} = Arity, _, Mod, _) ->
+    pack(Arity, AvpName, Avp, Mod, Acc);
+
+%% Or check.
+acc2(Acc, Avp, _, AvpName, Arity, _, Mod, _) ->
+    Mx = max_arity(Arity),
+    if Mx =< Avp#diameter_avp.index ->
+            [Failed | Rec] = Acc,
+            [[{5009, Avp} | Failed] | Rec];
+       true ->
+            pack(Arity, AvpName, Avp, Mod, Acc)
+    end.
 
-%% 3588:
+%% 3588/6733:
 %%
-%%   DIAMETER_INVALID_AVP_VALUE         5004
-%%      The request contained an AVP with an invalid value in its data
-%%      portion.  A Diameter message indicating this error MUST include
-%%      the offending AVPs within a Failed-AVP AVP.
-rc(_, Avp, _, _) ->
-    {5004, Avp}.
-
-%% pack_avp/6
-
-pack_avp(Name, 0, Avp, Opts, Mod, Acc) ->
-    pack_AVP(Name, Avp, Opts, Mod, Acc);
-
-pack_avp(_, Arity, #diameter_avp{name = AvpName} = Avp, _Opts, Mod, Acc) ->
-    pack(Arity, AvpName, Avp, Mod, Acc).
-
-%% pack_AVP/5
+%%   DIAMETER_AVP_OCCURS_TOO_MANY_TIMES 5009
+%%      A message was received that included an AVP that appeared more
+%%      often than permitted in the message definition.  The Failed-AVP
+%%      AVP MUST be included and contain a copy of the first instance of
+%%      the offending AVP that exceeded the maximum number of occurrences
 
-pack_AVP(Name, Avp, #{strict_arities := T} = Opts, Mod, Acc)
-  when T /= decode ->
-    pack_AVP(Name, ?ANY, Avp, Opts, Mod, Acc);
+%% max_arity/1
 
-pack_AVP(Name, Avp, Opts, Mod, Acc) ->
-    pack_AVP(Name, Mod:avp_arity(Name, 'AVP'), Avp, Opts, Mod, Acc).
+max_arity(1) ->
+    1;
+max_arity({_,Mx}) ->
+    Mx.
 
-%% pack_AVP/6
+%% rc/1
 
-%% Length failure was induced because of a header/payload length
-%% mismatch. The AVP Length is reset to match the received data if
-%% this AVP is encoded in an answer message, since the length is
-%% computed.
-%%
-%% Data is a truncated header if command_code = undefined, otherwise
-%% payload bytes. The former is padded to the length of a header if
-%% the AVP reaches an outgoing encode in diameter_codec.
-%%
-%% RFC 6733 says that an AVP returned with 5014 can contain a minimal
-%% payload for the AVP's type, but in this case we don't know the
-%% type.
-
-pack_AVP(_, _, #diameter_avp{data = {5014 = RC, Data}} = Avp, _, _, Acc) ->
-    {Rec, AM, Failed} = Acc,
-    {Rec, AM, [{RC, Avp#diameter_avp{data = Data}} | Failed]};
-
-pack_AVP(Name, Arity, Avp, Opts, Mod, Acc) ->
-    case pack_AVP(Name, Opts, Arity, Avp) of
-        false ->
-            M = Avp#diameter_avp.is_mandatory,
-            {Rec, AM, Failed} = Acc,
-            {Rec, AM, [{if M -> 5001; true -> 5008 end, Avp} | Failed]};
-        true ->
-            pack(Arity, 'AVP', Avp, Mod, Acc)
-    end.
+rc(#diameter_avp{is_mandatory = M}) ->
+    if M -> 5001; true -> 5008 end.
 
 %% 3588:
 %%
@@ -686,42 +667,59 @@ pack_AVP(Name, Arity, Avp, Opts, Mod, Acc) ->
 %%      Failed-AVP AVP MUST be included and contain a copy of the
 %%      offending AVP.
 
-%% pack_AVP/4
+%% pack_arity/5
 
 %% Give Failed-AVP special treatment since (1) it'll contain any
 %% unrecognized mandatory AVP's and (2) the RFC 3588 grammar failed to
 %% allow for Failed-AVP in an answer-message.
 
-pack_AVP(_, #{strict_arities := T}, _, _)
-  when T /= decode ->
-    true;
+pack_arity(Name, AvpName, _, Mod, M)
+  when Name == 'Failed-AVP';
+       Name == 'answer-message', AvpName == 'Failed-AVP';
+       not M ->
+    Mod:avp_arity(Name, 'AVP');
+%% Not testing just Name /= 'Failed-AVP' means we're changing the
+%% packing of AVPs nested within Failed-AVP, but the point of
+%% ignoring errors within Failed-AVP is to decode as much as
+%% possible, and failing because a mandatory AVP couldn't be
+%% packed into a dedicated field defeats that point.
 
-pack_AVP(_, _, 0, _) ->
-    false;
+pack_arity(Name, _, #{strict_mbit := Strict, failed_avp := Failed}, Mod, _)
+  when not Strict;
+       Failed ->
+    Mod:avp_arity(Name, 'AVP');
 
-pack_AVP(Name,
-         #{strict_mbit := Strict,
-           failed_avp := Failed},
-         _,
-         #diameter_avp{is_mandatory = M,
-                       name = AvpName}) ->
-
-    %% Not testing just Name /= 'Failed-AVP' means we're changing the
-    %% packing of AVPs nested within Failed-AVP, but the point of
-    %% ignoring errors within Failed-AVP is to decode as much as
-    %% possible, and failing because a mandatory AVP couldn't be
-    %% packed into a dedicated field defeats that point.
-
-    Failed == true
-        orelse Name == 'Failed-AVP'
-        orelse (Name == 'answer-message' andalso AvpName == 'Failed-AVP')
-        orelse not M
-        orelse not Strict.
+pack_arity(_, _, _, _, _) ->
+    0.
+
+%% avp_arity/5
+
+avp_arity(Name, 'AVP' = AvpName, Mod, Opts, M) ->
+    pack_arity(Name, AvpName, Opts, Mod, M);
+
+avp_arity(Name, AvpName, Mod, _, _) ->
+    Mod:avp_arity(Name, AvpName).
+
+%% rc/4
+
+%% Length error communicated from diameter_types or a
+%% @custom_types/@codecs module.
+rc({'DIAMETER', 5014 = RC, _}, #diameter_avp{name = AvpName} = A, Opts, Mod) ->
+    {RC, A#diameter_avp{data = Mod:empty_value(AvpName, Opts)}};
+
+%% 3588:
+%%
+%%   DIAMETER_INVALID_AVP_VALUE         5004
+%%      The request contained an AVP with an invalid value in its data
+%%      portion.  A Diameter message indicating this error MUST include
+%%      the offending AVPs within a Failed-AVP AVP.
+rc(_, Avp, _, _) ->
+    {5004, Avp}.
 
 %% pack/5
 
-pack(Arity, F, Avp, Mod, {Rec, AM, Failed}) ->
-    {set(Arity, F, value(F, Avp), Mod, Rec), AM, Failed}.
+pack(Arity, F, Avp, Mod, [Failed | Rec]) ->
+    [Failed | set(Arity, F, value(F, Avp), Mod, Rec)].
 
 %% set/5
 
@@ -730,7 +728,7 @@ set(_, _, _, _, false = No) ->
 
 set(1, F, Value, _, Map)
   when is_map(Map) ->
-    maps:put(F, Value, Map);
+    Map#{F => Value};
 
 set(_, F, V, _, Map)
   when is_map(Map) ->
@@ -755,36 +753,28 @@ value(_, #diameter_avp{value = V}) ->
 %% # grouped_avp/3
 %% ---------------------------------------------------------------------------
 
--spec grouped_avp(decode, avp_name(), binary() | {5014, binary()}, term())
+%% Note that Grouped is the only AVP type that doesn't just return a
+%% decoded value, also returning the list of component diameter_avp
+%% records.
+
+-spec grouped_avp(decode, avp_name(), binary(), term())
    -> {avp_record(), [avp()]};
                  (encode, avp_name(), avp_record() | avp_values(), term())
    -> iolist()
     | no_return().
 
-%% Length error induced by diameter_codec:collect_avps/1: the AVP
-%% length in the header was too short (insufficient for the extracted
-%% header) or too long (past the end of the message). An empty payload
-%% is sufficient according to the RFC text for 5014.
-grouped_avp(decode, _Name, {5014 = RC, _Bin}, _) ->
-    ?THROW({grouped, {RC, []}, []});
-
-grouped_avp(decode, Name, Data, Opts) ->
-    grouped_decode(Name, diameter_codec:collect_avps(Data), Opts);
+%% An error in decoding a component AVP throws the first faulty
+%% component, which a catch wraps in the Grouped AVP in question. A
+%% partially decoded record is only used when ignoring errors in
+%% Failed-AVP.
+grouped_avp(decode, Name, Bin, Opts) ->
+    {Rec, Avps, Es} = T = decode_avps(Name, Bin, Opts),
+    [] == Es orelse ?THROW(T),
+    {Rec, Avps};
 
 grouped_avp(encode, Name, Data, Opts) ->
     encode_avps(Name, Data, Opts).
 
-%% grouped_decode/2
-%%
-%% Note that Grouped is the only AVP type that doesn't just return a
-%% decoded value, also returning the list of component diameter_avp
-%% records.
-
-%% Length error in trailing component AVP.
-grouped_decode(_Name, {Error, Acc}, _) ->
-    {5014, Avp} = Error,
-    ?THROW({grouped, Error, [Avp | Acc]});
-
 %% 7.5.  Failed-AVP AVP
 
 %%    In the case where the offending AVP is embedded within a Grouped AVP,
@@ -795,15 +785,6 @@ grouped_decode(_Name, {Error, Acc}, _) ->
 %%    to the single offending AVP.  This enables the recipient to detect
 %%    the location of the offending AVP when embedded in a group.
 
-%% An error in decoding a component AVP throws the first faulty
-%% component, which the catch in d/3 wraps in the Grouped AVP in
-%% question. A partially decoded record is only used when ignoring
-%% errors in Failed-AVP.
-grouped_decode(Name, ComponentAvps, Opts) ->
-    {Rec, Avps, Es} = decode_avps(Name, ComponentAvps, Opts),
-    [] == Es orelse ?THROW({grouped, [{_,_} = hd(Es) | Rec], Avps}),
-    {Rec, Avps}.
-
 %% ---------------------------------------------------------------------------
 %% # empty_group/2
 %% ---------------------------------------------------------------------------
@@ -840,7 +821,7 @@ empty(Name, #{module := Mod} = Opts) ->
 newrec(false = No, _, _, _) ->
     No;
 
-newrec(record, Mod, Name, #{strict_arities := T})
+newrec(record, Mod, Name, T)
   when T /= decode ->
     RecName = Mod:name2rec(Name),
     Sz = Mod:'#info-'(RecName, size),
@@ -859,16 +840,15 @@ newrec(Mod, Name) ->
 
 %% reformat/5
 
-reformat(_, Map, Arities, _Mod, _Opts, list) ->
-    [{F,V} || {F,_} <- Arities, #{F := V} <- [Map]];
+reformat(Name, Map, _Strict, Mod, list) ->
+    [{F,V} || {F,_} <- Mod:avp_arity(Name), #{F := V} <- [Map]];
 
-reformat(Name, Map, Arities, Mod, Opts, record_from_map) ->
-    SA = maps:get(strict_arities, Opts, decode),
+reformat(Name, Map, Strict, Mod, record_from_map) ->
     RecName = Mod:name2rec(Name),
-    list_to_tuple([RecName | [maps:get(F, Map, def(A, SA))
-                              || {F,A} <- Arities]]);
+    list_to_tuple([RecName | [mget(F, Map, def(A, Strict))
+                              || {F,A} <- Mod:avp_arity(Name)]]);
 
-reformat(_, Rec, _, _, _, _) ->
+reformat(_, Rec, _, _, _) ->
     Rec.
 
 %% def/2
diff --git a/lib/diameter/src/base/diameter_peer_fsm.erl b/lib/diameter/src/base/diameter_peer_fsm.erl
index c340c8b21a..9115630eb5 100644
--- a/lib/diameter/src/base/diameter_peer_fsm.erl
+++ b/lib/diameter/src/base/diameter_peer_fsm.erl
@@ -659,10 +659,6 @@ encode(Rec, Opts, Dict) ->
 
 %% incoming/2
 
-incoming({recv = T, Name, Pkt}, #state{parent = Pid, ack = Ack} = S) ->
-    Pid ! {T, self(), get_route(Ack, Name, Pkt), Name, Pkt},
-    rcv(Name, Pkt, S);
-
 incoming(#diameter_header{is_request = R}, #state{transport = TPid,
                                                   ack = Ack}) ->
     R andalso Ack andalso send(TPid, false),
@@ -680,98 +676,97 @@ incoming(T, _) ->
 
 %% recv/2
 
-recv(#diameter_packet{header = #diameter_header{} = Hdr}
-     = Pkt,
-     #state{dictionary = Dict0}
-     = S) ->
-    recv1(diameter_codec:msg_name(Dict0, Hdr), Pkt, S);
-
-recv(#diameter_packet{header = undefined,
-                      bin = Bin}
-     = Pkt,
-     S) ->
-    recv(diameter_codec:decode_header(Bin), Pkt, S);
+recv(#diameter_packet{bin = Bin} = Pkt, S) ->
+    recv(Bin, Pkt, S);
 
 recv(Bin, S) ->
-    recv(#diameter_packet{bin = Bin}, S).
+    recv(Bin, Bin, S).
+
+%% recv/3
+
+recv(Bin, Msg, S) ->
+    recv(diameter_codec:decode_header(Bin), Bin, Msg, S).
+
+%% recv/4
 
-%% recv1/3
+recv(false, Bin, _, #state{length_errors = E}) ->
+    invalid(E, truncated_header, Bin),
+    Bin;
+
+recv(#diameter_header{length = Len} = H, Bin, Msg, #state{length_errors = E,
+                                                          incoming_maxlen = M,
+                                                          dictionary = Dict0}
+                                                   = S)
+  when E == handle;
+       0 == Len rem 4, bit_size(Bin) == 8*Len, size(Bin) =< M ->
+    recv1(diameter_codec:msg_name(Dict0, H), H, Msg, S);
 
-recv1(_,
-      #diameter_packet{header = H, bin = Bin},
-      #state{incoming_maxlen = M})
+recv(H, Bin, _, #state{incoming_maxlen = M})
   when M < size(Bin) ->
     invalid(false, incoming_maxlen_exceeded, {size(Bin), H}),
     H;
 
+recv(H, Bin, _, #state{length_errors = E}) ->
+    T = {size(Bin), bit_size(Bin) rem 8, H},
+    invalid(E, message_length_mismatch, T),
+    H.
+
+%% recv1/4
+
 %% Ignore anything but an expected CER/CEA if so configured. This is
 %% non-standard behaviour.
-recv1(Name, #diameter_packet{header = H}, #state{state = {'Wait-CEA', _, _},
-                                                 strict = false})
+recv1(Name, H, _, #state{state = {'Wait-CEA', _, _},
+                         strict = false})
   when Name /= 'CEA' ->
     H;
-recv1(Name, #diameter_packet{header = H}, #state{state = recv_CER,
-                                                 strict = false})
+recv1(Name, H, _, #state{state = recv_CER,
+                         strict = false})
   when Name /= 'CER' ->
     H;
 
 %% Incoming request after outgoing DPR: discard. Don't discard DPR, so
 %% both ends don't do so when sending simultaneously.
-recv1(Name,
-      #diameter_packet{header = #diameter_header{is_request = true} = H},
-      #state{dpr = {_,_,_}})
+recv1(Name, #diameter_header{is_request = true} = H, _, #state{dpr = {_,_,_}})
   when Name /= 'DPR' ->
     invalid(false, recv_after_outgoing_dpr, H),
     H;
 
 %% Incoming request after incoming DPR: discard.
-recv1(_,
-      #diameter_packet{header = #diameter_header{is_request = true} = H},
-      #state{dpr = true}) ->
+recv1(_, #diameter_header{is_request = true} = H, _, #state{dpr = true}) ->
     invalid(false, recv_after_incoming_dpr, H),
     H;
 
 %% DPA with identifier mismatch, or in response to a DPR initiated by
 %% the service.
-recv1('DPA' = N,
-      #diameter_packet{header = #diameter_header{hop_by_hop_id = Hid,
-                                                 end_to_end_id = Eid}}
-      = Pkt,
-      #state{dpr = {X,H,E}}
+recv1('DPA' = Name,
+      #diameter_header{hop_by_hop_id = Hid, end_to_end_id = Eid}
+      = H,
+      Msg,
+      #state{dpr = {X,HI,EI}}
       = S)
-  when H /= Hid;
-       E /= Eid;
+  when HI /= Hid;
+       EI /= Eid;
        not X ->
-    rcv(N, Pkt, S);
+    Pkt = pkt(H, Msg),
+    handle(Name, Pkt, S);
 
-%% Any other message with a header and no length errors: send to the
-%% parent.
-recv1(Name, Pkt, #state{}) ->
-    {recv, Name, Pkt}.
+%% Any other message with a header and no length errors.
+recv1(Name, H, Msg, #state{parent = Pid, ack = Ack} = S) ->
+    Pkt = pkt(H, Msg),
+    Pid ! {recv, self(), get_route(Ack, Name, Pkt), Name, Pkt},
+    handle(Name, Pkt, S).
 
-%% recv/3
+%% pkt/2
 
-recv(#diameter_header{length = Len}
-     = H,
-     #diameter_packet{bin = Bin}
-     = Pkt,
-     #state{length_errors = E}
-     = S)
-  when E == handle;
-       0 == Len rem 4, bit_size(Bin) == 8*Len ->
-    recv(Pkt#diameter_packet{header = H}, S);
+pkt(H, Bin)
+  when is_binary(Bin) ->
+    #diameter_packet{header = H,
+                     bin = Bin};
 
-recv(#diameter_header{}
-     = H,
-     #diameter_packet{bin = Bin},
-     #state{length_errors = E}) ->
-    T = {size(Bin), bit_size(Bin) rem 8, H},
-    invalid(E, message_length_mismatch, T),
-    Bin;
+pkt(H, Pkt) ->
+    Pkt#diameter_packet{header = H}.
 
-recv(false, #diameter_packet{bin = Bin}, #state{length_errors = E}) ->
-    invalid(E, truncated_header, Bin),
-    Bin.
+%% invalid/3
 
 %% Note that counters here only count discarded messages.
 invalid(E, Reason, T) ->
@@ -780,39 +775,39 @@ invalid(E, Reason, T) ->
     ?LOG(Reason, T),
     ok.
 
-%% rcv/3
+%% handle/3
 
 %% Incoming CEA.
-rcv('CEA' = N,
-    #diameter_packet{header = #diameter_header{end_to_end_id = Eid,
-                                               hop_by_hop_id = Hid}}
-    = Pkt,
-    #state{state = {'Wait-CEA', Hid, Eid}}
-    = S) ->
+handle('CEA' = N,
+       #diameter_packet{header = #diameter_header{end_to_end_id = Eid,
+                                                  hop_by_hop_id = Hid}}
+       = Pkt,
+       #state{state = {'Wait-CEA', Hid, Eid}}
+       = S) ->
     ?LOG(recv, N),
     handle_CEA(Pkt, S);
 
 %% Incoming CER
-rcv('CER' = N, Pkt, #state{state = recv_CER} = S) ->
+handle('CER' = N, Pkt, #state{state = recv_CER} = S) ->
     handle_request(N, Pkt, S);
 
 %% Anything but CER/CEA in a non-Open state is an error, as is
 %% CER/CEA in anything but recv_CER/Wait-CEA.
-rcv(Name, _, #state{state = PS})
+handle(Name, _, #state{state = PS})
   when PS /= 'Open';
        Name == 'CER';
        Name == 'CEA' ->
     {stop, {Name, PS}};
 
-rcv('DPR' = N, Pkt, S) ->
+handle('DPR' = N, Pkt, S) ->
     handle_request(N, Pkt, S);
 
 %% DPA in response to DPR, with the expected identifiers.
-rcv('DPA' = N,
-    #diameter_packet{header = #diameter_header{end_to_end_id = Eid,
-                                               hop_by_hop_id = Hid}
-                            = H}
-    = Pkt,
+handle('DPA' = N,
+       #diameter_packet{header = #diameter_header{end_to_end_id = Eid,
+                                                  hop_by_hop_id = Hid}
+                               = H}
+       = Pkt,
     #state{dictionary = Dict0,
            transport = TPid,
            dpr = {X, Hid, Eid},
@@ -831,13 +826,13 @@ rcv('DPA' = N,
 %% Ignore an unsolicited DPA in particular. Note that dpa_timeout
 %% deals with the case in which the peer sends the wrong identifiers
 %% in DPA.
-rcv('DPA' = N, #diameter_packet{header = H}, _) ->
+handle('DPA' = N, #diameter_packet{header = H}, _) ->
     ?LOG(ignored, N),
     %% Note that these aren't counted in the normal recv counter.
     diameter_stats:incr({diameter_codec:msg_id(H), recv, ignored}),
     ok;
 
-rcv(_, _, _) ->
+handle(_, _, _) ->
     ok.
 
 %% incr/3
diff --git a/lib/diameter/src/base/diameter_service.erl b/lib/diameter/src/base/diameter_service.erl
index 3d3b25c8ad..208e2e8cb8 100644
--- a/lib/diameter/src/base/diameter_service.erl
+++ b/lib/diameter/src/base/diameter_service.erl
@@ -115,6 +115,7 @@
                       strict_arities => diameter:strict_arities(),
                       strict_mbit := boolean(),
                       decode_format := diameter:decode_format(),
+                      traffic_counters := boolean(),
                       string_decode := boolean(),
                       spawn_opt := list() | {module(), atom(), list()}}}).
 
diff --git a/lib/diameter/src/base/diameter_traffic.erl b/lib/diameter/src/base/diameter_traffic.erl
index 3463a93568..27a41d6eb0 100644
--- a/lib/diameter/src/base/diameter_traffic.erl
+++ b/lib/diameter/src/base/diameter_traffic.erl
@@ -70,12 +70,13 @@
          timeout = 5000 :: 0..16#FFFFFFFF,  %% for outgoing requests
          detach = false :: boolean()}).
 
-%% Term passed back to receive_message/6 with every incoming message.
+%% Term passed back to receive_message/5 with every incoming message.
 -record(recvdata,
         {peerT        :: ets:tid(),
          service_name :: diameter:service_name(),
          apps         :: [#diameter_app{}],
          sequence     :: diameter:sequence(),
+         counters     :: boolean(),
          codec        :: #{decode_format := diameter:decode_format(),
                            string_decode := boolean(),
                            strict_arities => diameter:strict_arities(),
@@ -98,12 +99,13 @@
 %% ---------------------------------------------------------------------------
 
 make_recvdata([SvcName, PeerT, Apps, SvcOpts | _]) ->
-    #{sequence := {_,_} = Mask, spawn_opt := Opts}
+    #{sequence := {_,_} = Mask, spawn_opt := Opts, traffic_counters := B}
         = SvcOpts,
     {Opts, #recvdata{service_name = SvcName,
                      peerT = PeerT,
                      apps = Apps,
                      sequence = Mask,
+                     counters = B,
                      codec = maps:with([decode_format,
                                         string_decode,
                                         strict_arities,
@@ -186,7 +188,7 @@ incr_error(Dir, Id, TPid) ->
 %% ---------------------------------------------------------------------------
 
 -spec incr_rc(send|recv, Pkt, TPid, DictT)
-   -> {Counter, non_neg_integer()}
+   -> Counter
     | Reason
  when Pkt :: #diameter_packet{},
       TPid :: pid(),
@@ -197,18 +199,26 @@ incr_error(Dir, Id, TPid) ->
                | {'Experimental-Result', integer(), integer()},
       Reason :: atom().
 
-incr_rc(Dir, Pkt, TPid, {_, AppDict, _} = DictT) ->
-    try
-        incr_result(Dir, Pkt, TPid, DictT)
+incr_rc(Dir, Pkt, TPid, {MsgDict, AppDict, Dict0}) ->
+    incr_rc(Dir, Pkt, TPid, MsgDict, AppDict, Dict0);
+
+incr_rc(Dir, Pkt, TPid, Dict0) ->
+    incr_rc(Dir, Pkt, TPid, Dict0, Dict0, Dict0).
+
+%% incr_rc/6
+
+incr_rc(Dir, Pkt, TPid, MsgDict, AppDict, Dict0) ->
+    try get_result(Dir, MsgDict, Dict0, Pkt) of
+        false ->
+            unknown;
+        Avp ->
+            incr_result(Dir, Avp, Pkt, TPid, AppDict)
     catch
         exit: {E,_} when E == no_result_code;
                          E == invalid_error_bit ->
             incr(TPid, {msg_id(Pkt#diameter_packet.header, AppDict), Dir, E}),
             E
-    end;
-
-incr_rc(Dir, Pkt, TPid, Dict0) ->
-    incr_rc(Dir, Pkt, TPid, {Dict0, Dict0, Dict0}).
+    end.
 
 %% ---------------------------------------------------------------------------
 %% receive_message/5
@@ -220,13 +230,13 @@ incr_rc(Dir, Pkt, TPid, Dict0) ->
    -> pid()     %% request handler
     | boolean() %% answer, known request or not
     | discard   %% request discarded by MFA
- when Route :: {Handler, RequestRef, Seqs}
+ when Route :: {Handler, RequestRef, TPid}
              | Ack,
       RecvData :: {[SpawnOpt], #recvdata{}},
       SpawnOpt :: term(),
       Handler :: pid(),
       RequestRef :: reference(),
-      Seqs :: {0..16#FFFFFFFF, 0..16#FFFFFFFF},
+      TPid :: pid(),
       Ack :: boolean().
 
 receive_message(TPid, Route, Pkt, Dict0, RecvData) ->
@@ -307,14 +317,15 @@ recv_request(Ack,
              = Pkt,
              Dict0,
              #recvdata{peerT = PeerT,
-                       apps = Apps}
+                       apps = Apps,
+                       counters = Count}
              = RecvData) ->
     Ack andalso (TPid ! {handler, self()}),
     case diameter_service:find_incoming_app(PeerT, TPid, Id, Apps) of
         {#diameter_app{id = Aid, dictionary = AppDict} = App, Caps} ->
-            incr(recv, Pkt, TPid, AppDict),
+            Count andalso incr(recv, Pkt, TPid, AppDict),
             DecPkt = decode(Aid, AppDict, RecvData, Pkt),
-            incr_error(recv, DecPkt, TPid, AppDict),
+            Count andalso incr_error(recv, DecPkt, TPid, AppDict),
             send_A(recv_R(App, TPid, Dict0, Caps, RecvData, DecPkt),
                    TPid,
                    App,
@@ -327,9 +338,7 @@ recv_request(Ack,
             %%      A request was sent for an application that is not
             %%      supported.
             RC = 3007,
-            Es = Pkt#diameter_packet.errors,
-            DecPkt = Pkt#diameter_packet{avps = collect_avps(Pkt),
-                                         errors = [RC | Es]},
+            DecPkt = diameter_codec:collect_avps(Pkt),
             send_answer(answer_message(RC, Dict0, Caps, DecPkt),
                         TPid,
                         Dict0,
@@ -345,14 +354,6 @@ recv_request(Ack,
 decode(Id, Dict, #recvdata{codec = Opts}, Pkt) ->
     errors(Id, diameter_codec:decode(Id, Dict, Opts, Pkt)).
 
-collect_avps(Pkt) ->
-    case diameter_codec:collect_avps(Pkt) of
-        {_Error, Avps} ->
-            Avps;
-        Avps ->
-            Avps
-    end.
-
 %% send_A/7
 
 send_A([T | Fs], TPid, App, Dict0, RecvData, DecPkt, Caps) ->
@@ -545,6 +546,7 @@ send_A({call, Opts}, TPid, App, Dict0, RecvData, Pkt, Caps, Fs) ->
                         MsgDict,
                         AppDict,
                         Dict0,
+                        RecvData#recvdata.counters,
                         Fs);
         RC ->
             send_answer(answer_message(RC, Dict0, Caps, Pkt),
@@ -588,14 +590,22 @@ send_answer(Ans, TPid, MsgDict, AppDict, Dict0, RecvData, DecPkt, Fs) ->
                  TPid,
                  RecvData#recvdata.codec,
                  make_answer_packet(Ans, DecPkt, MsgDict, Dict0)),
-    send_answer(Pkt, TPid, MsgDict, AppDict, Dict0, Fs).
+    send_answer(Pkt,
+                TPid,
+                MsgDict,
+                AppDict,
+                Dict0,
+                RecvData#recvdata.counters,
+                Fs).
 
-%% send_answer/6
+%% send_answer/7
 
-send_answer(Pkt, TPid, MsgDict, AppDict, Dict0, [EvalPktFs | EvalFs]) ->
+send_answer(Pkt, TPid, MsgDict, AppDict, Dict0, Count, [EvalPktFs | EvalFs]) ->
     eval_packet(Pkt, EvalPktFs),
-    incr(send, Pkt, TPid, AppDict),
-    incr_rc(send, Pkt, TPid, {MsgDict, AppDict, Dict0}),  %% count outgoing
+    Count andalso begin
+                      incr(send, Pkt, TPid, AppDict),
+                      incr_rc(send, Pkt, TPid, MsgDict, AppDict, Dict0)
+                  end,
     send(TPid, z(Pkt), _Route = self()),
     lists:foreach(fun diameter_lib:eval/1, EvalFs).
 
@@ -1120,48 +1130,31 @@ find_avp(Code, VId, [_ | Avps]) ->
 
 %% Message sent as a header/avps list.
 incr_result(send = Dir,
-            #diameter_packet{msg = [#diameter_header{} = H | _]}
-            = Pkt,
+            Avp,
+            #diameter_packet{msg = [#diameter_header{} = H | _]},
             TPid,
-            DictT) ->
-    incr_res(Dir, Pkt#diameter_packet{header = H}, TPid, DictT);
-
-%% Outgoing message as binary: don't count. (Sending binaries is only
-%% partially supported.)
-incr_result(send, #diameter_packet{header = undefined = No}, _, _) ->
-    No;
+            AppDict) ->
+    incr_result(Dir, Avp, H, [], TPid, AppDict);
 
 %% Incoming or outgoing. Outgoing with encode errors never gets here
 %% since encode fails.
-incr_result(Dir, Pkt, TPid, DictT) ->
-    incr_res(Dir, Pkt, TPid, DictT).
-
-incr_res(Dir,
-         #diameter_packet{header = #diameter_header{is_error = E}
-                          = Hdr,
-                          errors = Es}
-         = Pkt,
-         TPid,
-         DictT) ->
-    {MsgDict, AppDict, Dict0} = DictT,
+incr_result(Dir, Avp, Pkt, TPid, AppDict) ->
+    #diameter_packet{header = H, errors = Es}
+        = Pkt,
+    incr_result(Dir, Avp, H, Es, TPid, AppDict).
+
+%% incr_result/6
 
+incr_result(Dir, Avp, Hdr, Es, TPid, AppDict) ->
     Id = msg_id(Hdr, AppDict),
     %% Could be {relay, 0}, in which case the R-bit is redundant since
     %% only answers are being counted. Let it be however, so that the
     %% same tuple is in both send/recv and result code counters.
 
     %% Count incoming decode errors.
-    recv /= Dir orelse [] == Es orelse incr_error(Dir, Id, TPid, AppDict),
-
-    %% Exit on a missing result code.
-    T = rc_counter(MsgDict, Dir, Pkt),
-    T == false andalso ?LOGX(no_result_code, {MsgDict, Dir, Hdr}),
-    {Ctr, RC, Avp} = T,
-
-    %% Or on an inappropriate value.
-    is_result(RC, E, Dict0)
-        orelse ?LOGX(invalid_error_bit, {MsgDict, Dir, Hdr, Avp}),
+    send == Dir orelse [] == Es orelse incr_error(Dir, Id, TPid, AppDict),
 
+    Ctr = rcc(Avp),
     incr(TPid, {Id, Dir, Ctr}),
     Ctr.
 
@@ -1206,7 +1199,50 @@ is_result(RC, true, _) ->
 incr(TPid, Counter) ->
     diameter_stats:incr(Counter, TPid, 1).
 
-%% rc_counter/3
+%% rcc/1
+
+rcc(#diameter_avp{name = 'Result-Code' = Name, value = V}) ->
+    {Name, head(V)};
+
+rcc(#diameter_avp{name = 'Experimental-Result', value = V}) ->
+    head(V).
+
+%% head/1
+
+head([V|_]) ->
+    V;
+head(V) ->
+    V.
+
+%% rcv/1
+
+rcv(#diameter_avp{name = N, value = V}) ->
+    rcv(N, head(V)).
+
+%% rcv/2
+
+rcv('Experimental-Result', {_,_,N}) ->
+    N;
+
+rcv('Result-Code', N) ->
+    N.
+
+%% get_result/4
+
+%% Message sent as binary: no checks or counting.
+get_result(_, _, _, #diameter_packet{header = undefined}) ->
+    false;
+
+get_result(Dir, MsgDict, Dict0, Pkt) ->
+    Avp = get_result(MsgDict, msg(Dir, Pkt)),
+    Hdr = Pkt#diameter_packet.header,
+    %% Exit on a missing result code or inappropriate value.
+    Avp == false
+        andalso ?LOGX(no_result_code, {MsgDict, Dir, Hdr}),
+    E = Hdr#diameter_header.is_error,
+    is_result(rcv(Avp), E, Dict0)
+        orelse ?LOGX(invalid_error_bit, {MsgDict, Dir, Hdr, Avp}),
+    Avp.
 
 %% RFC 3588, 7.6:
 %%
@@ -1214,46 +1250,29 @@ incr(TPid, Counter) ->
 %%   applications MUST include either one Result-Code AVP or one
 %%   Experimental-Result AVP.
 
-rc_counter(Dict, Dir, #diameter_packet{header = H,
-                                       avps = As,
-                                       msg = Msg})
+%% msg/2
+
+msg(Dir, #diameter_packet{header = H,
+                          avps = As,
+                          msg = Msg})
   when Dir == recv;         %% decoded incoming
        Msg == undefined ->  %% relayed outgoing
-    rc_counter(Dict, [H|As]);
-
-rc_counter(Dict, _, #diameter_packet{msg = Msg}) ->
-    rc_counter(Dict, Msg).
-
-rc_counter(Dict, Msg) ->
-    rcc(get_result(Dict, Msg)).
-
-rcc(#diameter_avp{name = 'Result-Code' = Name, value = N} = A)
-  when is_integer(N) ->
-    {{Name, N}, N, A};
+    [H|As];
 
-rcc(#diameter_avp{name = 'Result-Code' = Name, value = [N|_]} = A)
-  when is_integer(N) ->
-    {{Name, N}, N, A};
-
-rcc(#diameter_avp{name = 'Experimental-Result', value = {_,_,N} = T} = A)
-  when is_integer(N) ->
-    {T, N, A};
-
-rcc(#diameter_avp{name = 'Experimental-Result', value = [{_,_,N} = T|_]} = A)
-  when is_integer(N) ->
-    {T, N, A};
-
-rcc(_) ->
-    false.
+msg(_, #diameter_packet{msg = Msg}) ->
+    Msg.
 
 %% get_result/2
 
 get_result(Dict, Msg) ->
     try
         [throw(A) || N <- ['Result-Code', 'Experimental-Result'],
-                     #diameter_avp{} = A <- [get_avp(Dict, N, Msg)]]
+                     #diameter_avp{} = A <- [get_avp(Dict, N, Msg)],
+                     is_integer(catch rcv(A))],
+        false
     catch
-        #diameter_avp{} = A -> A
+        #diameter_avp{} = A ->
+            A
     end.
 
 x(T) ->
@@ -1377,7 +1396,7 @@ make_opts([T | _], _, _, _, _, _) ->
 
 send_request({{TPid, _Caps} = TC, App}
              = Transport,
-             #{sequence := Mask}
+             #{sequence := Mask, traffic_counters := Count}
              = SvcOpts,
              Msg0,
              CallOpts,
@@ -1393,9 +1412,15 @@ send_request({{TPid, _Caps} = TC, App}
                             SvcOpts,
                             ReqPkt),
             eval_packet(EncPkt, Fs),
-            T = send_R(ReqPkt, EncPkt, Transport, CallOpts, Caller, SvcName),
+            T = send_R(ReqPkt,
+                       EncPkt,
+                       Transport,
+                       CallOpts,
+                       Caller,
+                       Count,
+                       SvcName),
             Ans = recv_answer(SvcName, App, CallOpts, T),
-            handle_answer(SvcName, SvcOpts, App, Ans);
+            handle_answer(SvcName, Count, SvcOpts, App, Ans);
         {discard, Reason} ->
             {error, Reason};
         discard ->
@@ -1538,6 +1563,7 @@ send_R(ReqPkt,
        {{TPid, _Caps} = TC, #diameter_app{dictionary = AppDict}},
        #options{timeout = Timeout},
        {Pid, Ref},
+       Count,
        SvcName) ->
     Req = #request{ref = Ref,
                    caller = Pid,
@@ -1545,7 +1571,7 @@ send_R(ReqPkt,
                    peer = TC,
                    packet = ReqPkt},
 
-    incr(send, EncPkt, TPid, AppDict),
+    Count andalso incr(send, EncPkt, TPid, AppDict),
     {TRef, MRef} = zend_requezt(TPid, EncPkt, Req, SvcName, Timeout),
     Pid ! Ref,  %% tell caller a send has been attempted
     {TRef, MRef, Req}.
@@ -1577,15 +1603,16 @@ failover(SvcName, App, Req, CallOpts) ->
                    CallOpts,
                    SvcName).
 
-%% handle_answer/4
+%% handle_answer/5
 
-handle_answer(SvcName, _, App, {error, Req, Reason}) ->
+handle_answer(SvcName, _, _, App, {error, Req, Reason}) ->
     #request{packet = Pkt,
              peer = {_TPid, _Caps} = TC}
         = Req,
     cb(App, handle_error, [Reason, msg(Pkt), SvcName, TC]);
 
 handle_answer(SvcName,
+              Count,
               SvcOpts,
               #diameter_app{id = Id,
                             dictionary = AppDict,
@@ -1599,43 +1626,50 @@ handle_answer(SvcName,
     #request{peer = {TPid, _}}
         = Req,
 
-    incr(recv, DecPkt, TPid, AppDict),
-
-    AnsPkt = try
-                 incr_result(recv, DecPkt, TPid, {MsgDict, AppDict, Dict0})
-             of
-                 _ -> DecPkt
-             catch
-                 exit: {no_result_code, _} ->
-                     %% RFC 6733 requires one of Result-Code or
-                     %% Experimental-Result, but the decode will have
-                     %% detected a missing AVP. If both are optional in
-                     %% the dictionary then this isn't a decode error:
-                     %% just continue on.
-                     DecPkt;
-                 exit: {invalid_error_bit, {_, _, _, Avp}} ->
-                     #diameter_packet{errors = Es}
-                         = DecPkt,
-                     E = {5004, Avp},
-                     DecPkt#diameter_packet{errors = [E|Es]}
-             end,
-
-    handle_answer(AnsPkt, SvcName, App, AE, Req).
+    answer(answer(DecPkt, TPid, MsgDict, AppDict, Dict0, Count),
+           SvcName,
+           App,
+           AE,
+           Req).
+
+%% answer/6
+
+answer(DecPkt, TPid, MsgDict, AppDict, Dict0, Count) ->
+    Count andalso incr(recv, DecPkt, TPid, AppDict),
+    try get_result(recv, MsgDict, Dict0, DecPkt) of
+        Avp ->
+            Count andalso false /= Avp
+                  andalso incr_result(recv, Avp, DecPkt, TPid, AppDict),
+            DecPkt
+    catch
+        exit: {no_result_code, _} ->
+            %% RFC 6733 requires one of Result-Code or
+            %% Experimental-Result, but the decode will have
+            %% detected a missing AVP. If both are optional in
+            %% the dictionary then this isn't a decode error:
+            %% just continue on.
+            DecPkt;
+        exit: {invalid_error_bit, {_, _, _, Avp}} ->
+            #diameter_packet{errors = Es}
+                = DecPkt,
+            E = {5004, Avp},
+            DecPkt#diameter_packet{errors = [E|Es]}
+    end.
 
-%% handle_answer/5
+%% answer/5
 
-handle_answer(#diameter_packet{errors = Es}
-              = Pkt,
-              SvcName,
-              App,
-              AE,
-              #request{peer = {_TPid, _Caps} = TC,
-                       packet = P})
+answer(#diameter_packet{errors = Es}
+       = Pkt,
+       SvcName,
+       App,
+       AE,
+       #request{peer = {_TPid, _Caps} = TC,
+                packet = P})
   when callback == AE;
        [] == Es ->
     cb(App, handle_answer, [Pkt, msg(P), SvcName, TC]);
 
-handle_answer(#diameter_packet{header = H}, SvcName, _, AE, _) ->
+answer(#diameter_packet{header = H}, SvcName, _, AE, _) ->
     handle_error(H, SvcName, AE).
 
 %% handle_error/3
@@ -1848,10 +1882,8 @@ get_destination(Dict, Msg) ->
     [str(get_avp_value(Dict, D, Msg)) || D <- ['Destination-Realm',
                                                'Destination-Host']].
 
-%% This is not entirely correct. The avp could have an arity 1, in
-%% which case an empty list is a DiameterIdentity of length 0 rather
-%% than the list of no values we treat it as by mapping to undefined.
-%% This behaviour is documented.
+%% A DiameterIdentity has length at least one, so an empty list is not
+%% a Realm/Host.
 str([]) ->
     undefined;
 str(T) ->
@@ -1881,10 +1913,8 @@ get_avp(?RELAY, Name, Msg) ->
 get_avp(Dict, Name, [#diameter_header{} | Avps]) ->
     try
         {Code, _, VId} = Dict:avp_header(Name),
-        find_avp(Code, VId, Avps)
-    of
-        A ->
-            (avp_decode(Dict, Name, ungroup(A)))#diameter_avp{name = Name}
+        A = find_avp(Code, VId, Avps),
+        (avp_decode(Dict, Name, ungroup(A)))#diameter_avp{name = Name}
     catch
         error: _ ->
             undefined
@@ -1941,13 +1971,8 @@ avp_decode(Dict, Name, #diameter_avp{value = undefined,
                                      data = Bin}
                        = Avp)
   when is_binary(Bin) ->
-    try Dict:avp(decode, Bin, Name, decode_opts(Dict)) of
-        V ->
-            Avp#diameter_avp{value = V}
-    catch
-        error:_ ->
-            Avp
-    end;
+    V = Dict:avp(decode, Bin, Name, decode_opts(Dict)),
+    Avp#diameter_avp{value = V};
 avp_decode(_, _, #diameter_avp{} = Avp) ->
     Avp.
 
diff --git a/lib/diameter/src/base/diameter_watchdog.erl b/lib/diameter/src/base/diameter_watchdog.erl
index 294325751e..b2172356ee 100644
--- a/lib/diameter/src/base/diameter_watchdog.erl
+++ b/lib/diameter/src/base/diameter_watchdog.erl
@@ -154,7 +154,7 @@ i({Ack, T, Pid, {Opts,
               receive_data = RecvData,
               dictionary = Dict0,
               config =
-                  maps:without(CodecKeys,
+                  maps:without([traffic_counters | CodecKeys],
                                config(SvcOpts#{restrict => restrict(Nodes),
                                                suspect => 1,
                                                okay => 3},