Merge branch 'master' of super:otp into bmk/inets/inets58_integration

21 files changed, 562 insertions, 476 deletions

diff --git a/lib/diameter/src/app/Makefile b/lib/diameter/src/app/Makefile
index 31344fa80b..96b7736a90 100644
--- a/lib/diameter/src/app/Makefile
+++ b/lib/diameter/src/app/Makefile
@@ -66,12 +66,20 @@ SPEC_ERL_FILES = \
 SPEC_HRL_FILES = \
 	$(SPEC_FILES:%.dia=%.hrl)
 
+MODULES = \
+	$(RUNTIME_MODULES) \
+	$(HELP_MODULES)
+
 APP_MODULES = \
-	$(MODULES) \
+	$(RUNTIME_MODULES) \
 	$(SPEC_MODULES)
 
+TARGET_MODULES = \
+	$(APP_MODULES) \
+	$(HELP_MODULES)
+
 TARGET_FILES = \
-	$(APP_MODULES:%=$(EBIN)/%.$(EMULATOR)) \
+	$(TARGET_MODULES:%=$(EBIN)/%.$(EMULATOR)) \
 	$(APP_TARGET) \
 	$(APPUP_TARGET)
 
@@ -133,17 +141,15 @@ info:
 # ----------------------------------------------------
 
 # Generate the app file and then modules into in. This shouldn't know
-# about ../{compiler,transport} but good enough for now.
+# about ../transport but good enough for now.
 $(APP_TARGET): $(APP_SRC) \
                ../../vsn.mk \
                modules.mk \
-               ../compiler/modules.mk \
                ../transport/modules.mk
 	sed -e 's;%VSN%;$(VSN);' $< > $@
 	M=`echo $(APP_MODULES) | sed -e 's/^ *//' -e 's/ *$$//' -e 'y/ /,/'`; \
 	echo "/%APP_MODULES%/s//$$M/;w;q" | tr ';' '\n' \
 	| ed -s $@
-	$(MAKE) -C ../compiler  $(APP_TARGET) APP_TARGET=$(APP_TARGET)
 	$(MAKE) -C ../transport $(APP_TARGET) APP_TARGET=$(APP_TARGET)
 
 $(APPUP_TARGET): $(APPUP_SRC) ../../vsn.mk
@@ -190,6 +196,10 @@ release_docs_spec:
 # Dependencies
 # ----------------------------------------------------
 
+$(SPEC_FILES:%.dia=$(EBIN)/%.$(EMULATOR)): \
+	$(DIAMETER_TOP)/include/diameter.hrl \
+	$(DIAMETER_TOP)/include/diameter_gen.hrl
+
 depend: depend.mk
 
 # Generate dependencies makefile. It's assumed that the compile target
diff --git a/lib/diameter/src/app/diameter.app.src b/lib/diameter/src/app/diameter.app.src
index 119997953e..a806b5c78a 100644
--- a/lib/diameter/src/app/diameter.app.src
+++ b/lib/diameter/src/app/diameter.app.src
@@ -20,7 +20,7 @@
 {application, diameter,
  [{description, "Diameter protocol"},
   {vsn, "%VSN%"},
-  {modules, [%APP_MODULES%,%COMPILER_MODULES%,%TRANSPORT_MODULES%]},
+  {modules, [%APP_MODULES%,%TRANSPORT_MODULES%]},
   {registered, []},
   {applications, [stdlib, kernel]},
   {env, []},
diff --git a/lib/diameter/src/app/diameter.appup.src b/lib/diameter/src/app/diameter.appup.src
index 2b96153575..6d8ceadb92 100644
--- a/lib/diameter/src/app/diameter.appup.src
+++ b/lib/diameter/src/app/diameter.appup.src
@@ -20,8 +20,28 @@
 
 {"%VSN%",
  [
+  {"0.9",
+   [
+    {load_module, diameter,           soft_purge, soft_purge, []},
+    {load_module, diameter_capx,      soft_purge, soft_purge, []},
+    {load_module, diameter_codec,     soft_purge, soft_purge, [diameter_lib]},
+    {load_module, diameter_lib,       soft_purge, soft_purge, []},
+    {load_module, diameter_types,     soft_purge, soft_purge, []},
+    {load_module, diameter_gen_base_accounting, soft_purge, soft_purge, []},
+    {load_module, diameter_gen_base_rfc3588,    soft_purge, soft_purge, []},
+    {load_module, diameter_gen_relay, soft_purge, soft_purge, []},
+    {update, diameter_service,  soft, soft_purge, soft_purge, [diameter_lib]},
+    {update, diameter_config,   soft, soft_purge, soft_purge, []},
+    {update, diameter_peer,     soft, soft_purge, soft_purge, []},
+    {update, diameter_peer_fsm, soft, soft_purge, soft_purge, [diameter_lib]},
+    {update, diameter_reg,      soft, soft_purge, soft_purge, []},
+    {update, diameter_sctp,     soft, soft_purge, soft_purge, []},
+    {update, diameter_stats,    soft, soft_purge, soft_purge, []},
+    {update, diameter_sync,     soft, soft_purge, soft_purge, []},
+    {update, diameter_watchdog, soft, soft_purge, soft_purge, [diameter_lib]}
+   ]
+  }
  ],
  [
  ]
 }.
-
diff --git a/lib/diameter/src/app/diameter_callback.erl b/lib/diameter/src/app/diameter_callback.erl
index fcf9a8fc1e..6d5c8cdca1 100644
--- a/lib/diameter/src/app/diameter_callback.erl
+++ b/lib/diameter/src/app/diameter_callback.erl
@@ -60,28 +60,28 @@ pick_peer([Peer|_], _, _SvcName, _State) ->
 %%% ----------------------------------------------------------
 
 prepare_request(Pkt, _SvcName, _Peer) ->
-    Pkt.
+    {send, Pkt}.
 
 %%% ----------------------------------------------------------
 %%% # prepare_retransmit/3
 %%% ----------------------------------------------------------
 
 prepare_retransmit(Pkt, _SvcName, _Peer) ->
-    Pkt.
+    {send, Pkt}.
 
 %%% ----------------------------------------------------------
 %%% # handle_request/3
 %%% ----------------------------------------------------------
 
 handle_request(_Pkt, _SvcName, _Peer) ->
-    discard.
+    {protocol_error, 3001}.  %% DIAMETER_COMMAND_UNSUPPORTED
 
 %%% ----------------------------------------------------------
 %%% # handle_answer/4
 %%% ----------------------------------------------------------
 
 handle_answer(#diameter_packet{msg = Ans}, _Req, _SvcName, _Peer) ->
-    {ok, Ans}.
+    Ans.
 
 %%% ---------------------------------------------------------------------------
 %%% # handle_error/4
diff --git a/lib/diameter/src/app/diameter_capx.erl b/lib/diameter/src/app/diameter_capx.erl
index aa5318e79d..138e76411e 100644
--- a/lib/diameter/src/app/diameter_capx.erl
+++ b/lib/diameter/src/app/diameter_capx.erl
@@ -62,6 +62,7 @@
 -define(NOSECURITY, ?'DIAMETER_BASE_RESULT-CODE_DIAMETER_NO_COMMON_SECURITY').
 
 -define(NO_INBAND_SECURITY, 0).
+-define(TLS, 1).
 
 %% ===========================================================================
 
@@ -80,7 +81,7 @@ recv_CER(CER, Svc) ->
     try_it([fun rCER/2, CER, Svc]).
 
 -spec recv_CEA(#diameter_base_CEA{}, #diameter_service{})
-   -> tried({['Unsigned32'()], #diameter_caps{}}).
+   -> tried({['Unsigned32'()], ['Unsigned32'()], #diameter_caps{}}).
 
 recv_CEA(CEA, Svc) ->
     try_it([fun rCEA/2, CEA, Svc]).
@@ -126,10 +127,11 @@ mk_caps(Caps0, Opts) ->
 set_cap({Key, _}, _) ->
     ?THROW({duplicate, Key}).
 
-cap(K, V) when K == 'Origin-Host';
-               K == 'Origin-Realm';
-               K == 'Vendor-Id';
-               K == 'Product-Name' ->
+cap(K, V)
+  when K == 'Origin-Host';
+       K == 'Origin-Realm';
+       K == 'Vendor-Id';
+       K == 'Product-Name' ->
     V;
 
 cap('Host-IP-Address', Vs)
@@ -139,11 +141,8 @@ cap('Host-IP-Address', Vs)
 cap('Firmware-Revision', V) ->
     [V];
 
-%% Not documented but accept it as long as it's what we support.
-cap('Inband-Security-Id', [0] = Vs) ->  %% NO_INBAND_SECURITY
-    Vs;
-
-cap(K, Vs) when K /= 'Inband-Security-Id', is_list(Vs) ->
+cap(_, Vs)
+  when is_list(Vs) ->
     Vs;
 
 cap(K, V) ->
@@ -161,28 +160,10 @@ ipaddr(A) ->
 %%
 %% Build a CER record to send to a remote peer.
 
-bCER(#diameter_caps{origin_host = Host,
-                    origin_realm = Realm,
-                    host_ip_address = Addrs,
-                    vendor_id = Vid,
-                    product_name = Name,
-                    origin_state_id = OSI,
-                    supported_vendor_id = SVid,
-                    auth_application_id = AuId,
-                    acct_application_id = AcId,
-                    vendor_specific_application_id = VSA,
-                    firmware_revision = Rev}) ->
-    #diameter_base_CER{'Origin-Host' = Host,
-                       'Origin-Realm' = Realm,
-                       'Host-IP-Address' = Addrs,
-                       'Vendor-Id' = Vid,
-                       'Product-Name' = Name,
-                       'Origin-State-Id' = OSI,
-                       'Supported-Vendor-Id' = SVid,
-                       'Auth-Application-Id' = AuId,
-                       'Acct-Application-Id' = AcId,
-                       'Vendor-Specific-Application-Id' = VSA,
-                       'Firmware-Revision' = Rev}.
+%% Use the fact that diameter_caps has the same field names as CER.
+bCER(#diameter_caps{} = Rec) ->
+    #diameter_base_CER{}
+        = list_to_tuple([diameter_base_CER | tl(tuple_to_list(Rec))]).
 
 %% rCER/2
 %%
@@ -219,19 +200,16 @@ bCER(#diameter_caps{origin_host = Host,
 %% That is, each side sends all of its capabilities and is responsible for
 %% not sending commands that the peer doesn't support.
 
-%% TODO: Make it an option to send only common applications in CEA to
-%%       allow backwards compatibility, and also because there are likely
-%%       servers that expect this. Or maybe a callback.
-
 %% 6.10.  Inband-Security-Id AVP
 %%
 %%   NO_INBAND_SECURITY                0
 %%      This peer does not support TLS.  This is the default value, if the
 %%      AVP is omitted.
+%%
+%%   TLS                               1
+%%      This node supports TLS security, as defined by [TLS].
 
 rCER(CER, #diameter_service{capabilities = LCaps} = Svc) ->
-    #diameter_base_CER{'Inband-Security-Id' = RIS}
-        = CER,
     #diameter_base_CEA{}
         = CEA
         = cea_from_cer(bCER(LCaps)),
@@ -241,56 +219,95 @@ rCER(CER, #diameter_service{capabilities = LCaps} = Svc) ->
 
     {SApps,
      RCaps,
-     build_CEA([] == SApps,
-               RIS,
-               lists:member(?NO_INBAND_SECURITY, RIS),
-               CEA#diameter_base_CEA{'Result-Code' = ?SUCCESS,
-                                     'Inband-Security-Id' = []})}.
+     build_CEA(SApps,
+               LCaps,
+               RCaps,
+               CEA#diameter_base_CEA{'Result-Code' = ?SUCCESS})}.
 
-%% TODO: 5.3 of RFC3588 says we MUST return DIAMETER_NO_COMMON_APPLICATION
+%% TODO: 5.3 of RFC 3588 says we MUST return DIAMETER_NO_COMMON_APPLICATION
 %%       in the CEA and SHOULD disconnect the transport. However, we have
 %%       no way to guarantee the send before disconnecting.
 
-build_CEA(true, _, _, CEA) ->
+build_CEA([], _, _, CEA) ->
     CEA#diameter_base_CEA{'Result-Code' = ?NOAPP};
-build_CEA(false, [_|_], false, CEA) ->
-    CEA#diameter_base_CEA{'Result-Code' = ?NOSECURITY};
-build_CEA(false, [_|_], true, CEA) ->
-    CEA#diameter_base_CEA{'Inband-Security-Id' = [?NO_INBAND_SECURITY]};
-build_CEA(false, [], false, CEA) ->
-    CEA.
+
+build_CEA(_, LCaps, RCaps, CEA) ->
+    case common_security(LCaps, RCaps) of
+        [] ->
+            CEA#diameter_base_CEA{'Result-Code' = ?NOSECURITY};
+        [_] = IS ->
+            CEA#diameter_base_CEA{'Inband-Security-Id' = IS}
+    end.
+
+%% common_security/2
+
+common_security(#diameter_caps{inband_security_id = LS},
+                #diameter_caps{inband_security_id = RS}) ->
+    cs(LS, RS).
+
+%% Unspecified is equivalent to NO_INBAND_SECURITY.
+cs([], RS) ->
+    cs([?NO_INBAND_SECURITY], RS);
+cs(LS, []) ->
+    cs(LS, [?NO_INBAND_SECURITY]);
+
+%% Agree on TLS if both parties support it. When sending CEA, this is
+%% to ensure the peer is clear that we will be expecting a TLS
+%% handshake since there is no ssl:maybe_accept that would allow the
+%% peer to choose between TLS or not upon reception of our CEA. When
+%% receiving CEA it deals with a server that isn't explicit about its choice.
+%% TODO: Make the choice configurable.
+cs(LS, RS) ->
+    Is = ordsets:to_list(ordsets:intersection(ordsets:from_list(LS),
+                                              ordsets:from_list(RS))),
+    case lists:member(?TLS, Is) of
+        true ->
+            [?TLS];
+        false when [] == Is ->
+            Is;
+        false ->
+            [hd(Is)]  %% probably NO_INBAND_SECURITY
+    end.
+%% The only two values defined by RFC 3588 are NO_INBAND_SECURITY and
+%% TLS but don't enforce this. In theory this allows some other
+%% security mechanism we don't have to know about, although in
+%% practice something there may be a need for more synchronization
+%% than notification by way of an event subscription offers.
 
 %% cea_from_cer/1
 
+%% CER is a subset of CEA, the latter adding Result-Code and a few
+%% more AVP's.
 cea_from_cer(#diameter_base_CER{} = CER) ->
     lists:foldl(fun(F,A) -> to_cea(CER, F, A) end,
                 #diameter_base_CEA{},
                 record_info(fields, diameter_base_CER)).
 
 to_cea(CER, Field, CEA) ->
-    try ?BASE:'#info-'(diameter_base_CEA, {index, Field}) of
-        N ->
-            setelement(N, CEA, ?BASE:'#get-'(Field, CER))
+    try ?BASE:'#get-'(Field, CER) of
+        V -> ?BASE:'#set-'({Field, V}, CEA)
     catch
-        error: _ ->
-            CEA
+        error: _ -> CEA
     end.
-
+        
 %% rCEA/2
 
-rCEA(CEA, #diameter_service{capabilities = LCaps} = Svc)
-  when is_record(CEA, diameter_base_CEA) ->
-    #diameter_base_CEA{'Result-Code' = RC}
-        = CEA,
-
+rCEA(#diameter_base_CEA{'Result-Code' = RC}
+     = CEA,
+     #diameter_service{capabilities = LCaps}
+     = Svc) ->
     RC == ?SUCCESS orelse ?THROW({'Result-Code', RC}),
 
     RCaps = capx_to_caps(CEA),
     SApps = common_applications(LCaps, RCaps, Svc),
 
-    [] == SApps andalso ?THROW({no_common_apps, LCaps, RCaps}),
+    [] == SApps andalso ?THROW(no_common_applications),
+
+    IS = common_security(LCaps, RCaps),
+
+    [] == IS andalso ?THROW(no_common_security),
 
-    {SApps, RCaps};
+    {SApps, IS, RCaps};
 
 rCEA(CEA, _Svc) ->
     ?THROW({invalid, CEA}).
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_config.erl b/lib/diameter/src/app/diameter_config.erl
index 42c70890b3..a6b48fe65b 100644
--- a/lib/diameter/src/app/diameter_config.erl
+++ b/lib/diameter/src/app/diameter_config.erl
@@ -267,7 +267,7 @@ handle_call(uptime, _, #state{id = Time} = State) ->
     {reply, diameter_lib:now_diff(Time), State};
 
 handle_call(Req, From, State) ->
-    warning_msg("received unexpected request from ~p:~n~w", [From, Req]),
+    ?UNEXPECTED([Req, From]),
     Reply = {error, {bad_request, Req}},
     {reply, Reply, State}.
 
@@ -276,7 +276,7 @@ handle_call(Req, From, State) ->
 %%% ----------------------------------------------------------
 
 handle_cast(Msg, State) ->
-    warning_msg("received unexpected message:~n~w", [Msg]),
+    ?UNEXPECTED([Msg]),
     {noreply, State}.
 
 %%% ----------------------------------------------------------
@@ -309,7 +309,7 @@ handle_info(restart, State) ->
     {noreply, State};
 
 handle_info(Info, State) ->
-    warning_msg("received unknown info:~n~w", [Info]),
+    ?UNEXPECTED([Info]),
     {noreply, State}.
 
 %%--------------------------------------------------------------------
@@ -674,8 +674,3 @@ cb(M,F) ->
 
 call(Request) ->
     gen_server:call(?SERVER, Request, infinity).
-
-%% warning_msg/2
-
-warning_msg(F, A) ->
-    ?diameter_warning("~p: " ++ F, [?MODULE | A]).
diff --git a/lib/diameter/src/app/diameter_dbg.erl b/lib/diameter/src/app/diameter_dbg.erl
index b18f34e13d..5b0ac3a3b6 100644
--- a/lib/diameter/src/app/diameter_dbg.erl
+++ b/lib/diameter/src/app/diameter_dbg.erl
@@ -68,12 +68,6 @@
 
 -define(VALUES(Rec), tl(tuple_to_list(Rec))).
 
-%%% ----------------------------------------------------------
-%%% # log/4
-%%%
-%%% Called to have something to trace on for happenings of interest.
-%%% ----------------------------------------------------------
-
 log(_Slogan, _Mod, _Line, _Details) ->
     ok.
 
@@ -82,9 +76,6 @@ log(_Slogan, _Mod, _Line, _Details) ->
 %%% ----------------------------------------------------------
 
 help() ->
-    ?INFO:usage(usage()).
-
-usage() ->
     not_yet_implemented.
 
 %%% ----------------------------------------------------------
@@ -99,30 +90,23 @@ table(T)
   when (T == diameter_peer) orelse (T == diameter_reg) ->
     ?INFO:format(collect(T), fields(T), fun ?INFO:split/2);
 
-table(diameter_service = T) ->
-    Fs = [name, started] ++ fields(T) ++ [peerT,
-                                          connT,
-                                          share_peers,
-                                          use_shared_peers,
-                                          shared_peers,
-                                          local_peers,
-                                          monitor],
-    ?INFO:format(T,
-                 fun(R) ->
-                         [I,N,S|Vs] = ?VALUES(R),
-                         {Fs, [N,I] ++ ?VALUES(S) ++ Vs}
-                 end,
-                 fun ?INFO:split/2);
-
 table(Table)
   when is_atom(Table) ->
     case fields(Table) of
         undefined = No ->
             No;
         Fields ->
-            ?INFO:format(Table, Fields, fun ?INFO:split/2)
+            ?INFO:format(Table, Fields, fun split/2)
     end.
 
+split([started, name | Fs], [S, N | Vs]) ->
+    {name, [started | Fs], N, [S | Vs]};
+split([[F|FT]|Fs], [Rec|Vs]) ->
+    [_, V | VT] = tuple_to_list(Rec),
+    {F, FT ++ Fs, V, VT ++ Vs};
+split([F|Fs], [V|Vs]) ->
+    {F, Fs, V, Vs}.
+
 %%% ----------------------------------------------------------
 %%% # TableName()
 %%% ----------------------------------------------------------
@@ -146,14 +130,14 @@ table(Table)
 %%% ----------------------------------------------------------
 
 tables() ->
-    format_all(fun ?INFO:split/3).
-
-format_all(SplitFun) ->
-    ?INFO:format(field(?LOCAL), SplitFun, fun collect/1).
+    ?INFO:format(field(?LOCAL), fun split/3, fun collect/1).
 
 field(Tables) ->
     lists:map(fun(T) -> {T, fields(T)} end, lists:sort(Tables)).
 
+split(_, Fs, Vs) ->
+    split(Fs, Vs).
+
 %%% ----------------------------------------------------------
 %%% # modules()
 %%% ----------------------------------------------------------
@@ -396,76 +380,24 @@ stop() ->
 %% tp/1
 
 tpl(T) ->
-    dbg(tpl, dbg(T)).
+    dbg(tpl, T).
 
 tp(T) ->
-    dbg(tp, dbg(T)).
-
-%% dbg/1
-
-dbg(x) ->
-    [{M, x, []} || M <- [diameter_tcp,
-                         diameter_etcp,
-                         diameter_sctp,
-                         diameter_peer_fsm,
-                         diameter_watchdog]];
-
-dbg(log) ->
-    {?MODULE, log, 4};
-
-dbg({log = F, Mods})
-  when is_list(Mods) ->
-    {?MODULE, F, [{['_','$1','_','_'],
-                   [?ORCOND([{'==', '$1', M} || M <- Mods])],
-                   []}]};
-
-dbg({log = F, Mod}) ->
-    dbg({F, [Mod]});
-
-dbg(send) ->
-    {diameter_peer, send, 2};
-
-dbg(recv) ->
-    {diameter_peer, recv, 2};
-
-dbg(sendrecv) ->
-    [{diameter_peer, send, 2},
-     {diameter_peer, recv, 2}];
-
-dbg(decode) ->
-    [{diameter_codec,decode,2}];
-
-dbg(encode) ->
-    [{diameter_codec,encode,2,[]},
-     {diameter_codec,encode,3,[]},
-     {diameter_codec,encode,4}];
-
-dbg(transition = T) ->
-    [{?MODULE, log, [{[T,M,'_','_'],[],[]}]}
-     || M <- [diameter_watchdog, diameter_peer_fsm]];
-
-dbg(T) ->
-    T.
+    dbg(tp, T).
 
 %% dbg/2
 
-dbg(TF, L)
+dbg(F, L)
   when is_list(L) ->
-    {ok, lists:foldl(fun(T,A) -> {ok, X} = dbg(TF, T), [X|A] end, [], L)};
+    [dbg(F, X) || X <- L];
 
 dbg(F, M)
   when is_atom(M) ->
-    dbg(F, {M});
+    apply(dbg, F, [M, x]);
 
 dbg(F, T)
   when is_tuple(T) ->
-    [_|_] = A = tuple_to_list(T),
-    {ok,_} = apply(dbg, F, case is_list(lists:last(A)) of
-                               false ->
-                                   A ++ [[{'_',[],[{exception_trace}]}]];
-                               true ->
-                                   A
-                           end).
+    apply(dbg, F, tuple_to_list(T)).
 
 %% ===========================================================================
 %% ===========================================================================
@@ -493,15 +425,19 @@ peers(Name) ->
 
 peers(_, undefined) ->
     [];
-peers(Name, {Cs,As}) ->
-    mk_peer(Name, connector, Cs) ++ mk_peer(Name, acceptor, As).
-
-mk_peer(Name, T, Ts) ->
-    [[Name | mk_peer(T,Vs)] || Vs <- Ts].
-
-mk_peer(Type, Vs) ->
-    [Ref, State, Opts, WPid, TPid, SApps, Caps]
-        = get_values(Vs, [ref, state, options, watchdog, peer, apps, caps]),
+peers(Name, Ts) ->
+    lists:flatmap(fun(T) -> mk_peers(Name, T) end, Ts).
+
+mk_peers(Name, [_, {type, connect} | _] = Ts) ->
+    [[Name | mk_peer(Ts)]];
+mk_peers(Name, [R, {type, listen}, O, {accept = A, As}]) ->
+    [[Name | mk_peer([R, {type, A}, O | Ts])] || Ts <- As].
+%% This is a bit lame: service_info works to build this list and out
+%% of something like what we want here and then we take it apart.
+
+mk_peer(Vs) ->
+    [Type, Ref, State, Opts, WPid, TPid, SApps, Caps]
+        = get_values(Vs, [type,ref,state,options,watchdog,peer,apps,caps]),
     [Ref, State, [{type, Type} | Opts], s(WPid), s(TPid), SApps, Caps].
 
 get_values(Vs, Ks) ->
@@ -509,9 +445,13 @@ get_values(Vs, Ks) ->
 
 s(undefined = T) ->
     T;
+s({Pid, _Started, _State}) ->
+    state(Pid);
+s({Pid, _Started}) ->
+    state(Pid).
 
 %% Collect states from watchdog/transport pids.
-s(Pid) ->
+state(Pid) ->
     MRef = erlang:monitor(process, Pid),
     Pid ! {state, self()},
     receive
@@ -541,7 +481,18 @@ fields(diameter_stats) ->
             []
     end;
 
-?FIELDS(diameter_service);
+fields(diameter_service) ->
+    [started,
+     name,
+     record_info(fields, diameter_service),
+     peerT,
+     connT,
+     share_peers,
+     use_shared_peers,
+     shared_peers,
+     local_peers,
+     monitor];
+
 ?FIELDS(diameter_event);
 ?FIELDS(diameter_uri);
 ?FIELDS(diameter_avp);
diff --git a/lib/diameter/src/app/diameter_internal.hrl b/lib/diameter/src/app/diameter_internal.hrl
index 9de3914830..63b35550a8 100644
--- a/lib/diameter/src/app/diameter_internal.hrl
+++ b/lib/diameter/src/app/diameter_internal.hrl
@@ -37,13 +37,14 @@
 %% Failure reports always get a stack trace.
 -define(STACK, erlang:get_stacktrace()).
 
-%% Info report for anything unexpected.
--define(REPORT(Reason, Func, Args),
-        diameter_lib:report(Reason, {?MODULE, Func, Args})).
+%% Warning report for unexpected messages in various processes.
+-define(UNEXPECTED(F,A),
+        diameter_lib:warning_report(unexpected, {?MODULE, F, A})).
+-define(UNEXPECTED(A), ?UNEXPECTED(?FUNC, A)).
 
 %% Something to trace on.
 -define(LOG(Slogan, Details),
-	diameter_dbg:log(Slogan, ?MODULE, ?LINE, Details)).
+	diameter_lib:log(Slogan, ?MODULE, ?LINE, Details)).
 -define(LOGC(Bool, Slogan, Details), ((Bool) andalso ?LOG(Slogan, Details))).
 
 %% Compensate for no builtin ?FUNC for use in log reports.
@@ -77,19 +78,3 @@
          server_id,
          is_dynamic,
          expiration}).
-
-%%%----------------------------------------------------------------------
-%%% Error/warning/info message macro(s)
-%%%----------------------------------------------------------------------
-
--define(diameter_info(F, A),
-        (catch error_logger:info_msg("[ ~w : ~w : ~p ] ~n" ++ F ++ "~n",
-                                     [?APPLICATION, ?MODULE, self()|A]))).
-
--define(diameter_warning(F, A),
-        (catch error_logger:warning_msg("[ ~w : ~w : ~p ] ~n" ++ F ++ "~n",
-                                        [?APPLICATION, ?MODULE, self()|A]))).
-
--define(diameter_error(F, A),
-        (catch error_logger:error_msg("[ ~w : ~w : ~p ] ~n" ++ F ++ "~n",
-                                      [?APPLICATION, ?MODULE, self()|A]))).
diff --git a/lib/diameter/src/app/diameter_lib.erl b/lib/diameter/src/app/diameter_lib.erl
index b5c0e1bf6a..362d593b24 100644
--- a/lib/diameter/src/app/diameter_lib.erl
+++ b/lib/diameter/src/app/diameter_lib.erl
@@ -30,7 +30,8 @@
          ipaddr/1,
          spawn_opts/2,
          wait/1,
-         fold_tuple/3]).
+         fold_tuple/3,
+         log/4]).
 
 -include("diameter_internal.hrl").
 
@@ -46,14 +47,9 @@
 report(Reason, MFA) ->
     info_report(Reason, MFA).
 
-info_report(Reason, {M,F,A}) ->
-    error_logger:info_report("   Reason: ~p~n"
-			     "      Pid: ~p~n"
-			     "     Node: ~p~n"
-			     "   Module: ~p~n"
-			     " Function: ~p~n"
-			     "Arguments: ~p~n",
-			     [Reason, self(), node(), M, F, A]).
+info_report(Reason, MFA) ->
+    report(fun error_logger:info_report/1, Reason, MFA),
+    true.
 
 %%% ---------------------------------------------------------------------------
 %%% # error_report(Reason, MFA)
@@ -69,7 +65,7 @@ warning_report(Reason, MFA) ->
     report(fun error_logger:warning_report/1, Reason, MFA).
 
 report(Fun, Reason, MFA) ->
-    Fun([{reason, Reason}, {who, self()}, {where, node()}, {what, MFA}]),
+    Fun([{why, Reason}, {who, self()}, {what, MFA}]),
     false.
 
 %%% ---------------------------------------------------------------------------
@@ -255,12 +251,22 @@ w(L) ->
 fold_tuple(_, T, undefined) ->
     T;
 
-fold_tuple(N, T0, T) ->
-    element(2, lists:foldl(fun(X, {M,_} = A) -> {M+1, ft(X, A)} end,
-                           {N, T0},
-                           lists:nthtail(N-1, tuple_to_list(T)))).
+fold_tuple(N, T0, T1) ->
+    {_, T} = lists:foldl(fun(V, {I,_} = IT) -> {I+1, ft(V, IT)} end,
+                         {N, T0},
+                         lists:nthtail(N-1, tuple_to_list(T1))),
+    T.
 
-ft(undefined, T) ->
+ft(undefined, {_, T}) ->
     T;
-ft(X, {N, T}) ->
-    setelement(N, T, X).
+ft(Value, {Idx, T}) ->
+    setelement(Idx, T, Value).
+
+%%% ----------------------------------------------------------
+%%% # log(Slogan, Mod, Line, Details)
+%%%
+%%% Called to have something to trace on for happenings of interest.
+%%% ----------------------------------------------------------
+
+log(_, _, _, _) ->
+    ok.
diff --git a/lib/diameter/src/app/diameter_peer.erl b/lib/diameter/src/app/diameter_peer.erl
index 6b8971b8ea..3e78c4caef 100644
--- a/lib/diameter/src/app/diameter_peer.erl
+++ b/lib/diameter/src/app/diameter_peer.erl
@@ -148,7 +148,7 @@ handle_call(uptime, _, #state{id = Time} = State) ->
     {reply, diameter_lib:now_diff(Time), State};
 
 handle_call(Req, From, State) ->
-    warning_msg("received unexpected request from ~p:~n~w", [From, Req]),
+    ?UNEXPECTED([Req, From]),
     {reply, nok, State}.
 
 %%% ----------------------------------------------------------
@@ -156,7 +156,7 @@ handle_call(Req, From, State) ->
 %%% ----------------------------------------------------------
 
 handle_cast(Msg, State) ->
-    warning_msg("received unexpected message:~n~w", [Msg]),
+    ?UNEXPECTED([Msg]),
     {noreply, State}.
 
 %%% ----------------------------------------------------------
@@ -169,7 +169,7 @@ handle_info({notify, SvcName, T}, S) ->
     {noreply, S};
 
 handle_info(Info, State) ->
-    warning_msg("received unexpected info:~n~w", [Info]),
+    ?UNEXPECTED([Info]),
     {noreply, State}.
 
 %% ----------------------------------------------------------
@@ -223,8 +223,3 @@ value([], V) ->
 
 call(Request) ->
     gen_server:call(?SERVER, Request, infinity).
-
-%% warning_msg/2
-
-warning_msg(F, A) ->
-    ?diameter_warning("~p: " ++ F, [?MODULE | A]).
diff --git a/lib/diameter/src/app/diameter_peer_fsm.erl b/lib/diameter/src/app/diameter_peer_fsm.erl
index 0252fb3809..282fa2742f 100644
--- a/lib/diameter/src/app/diameter_peer_fsm.erl
+++ b/lib/diameter/src/app/diameter_peer_fsm.erl
@@ -52,6 +52,9 @@
 -define(GOAWAY, ?'DIAMETER_BASE_DISCONNECT-CAUSE_DO_NOT_WANT_TO_TALK_TO_YOU').
 -define(REBOOT, ?'DIAMETER_BASE_DISCONNECT-CAUSE_REBOOTING').
 
+-define(NO_INBAND_SECURITY, 0).
+-define(TLS, 1).
+
 -define(LOOP_TIMEOUT, 2000).
 
 %% RFC 3588:
@@ -195,10 +198,8 @@ handle_info(T, #state{} = State) ->
             ?LOG(stop, T),
             x(T, State)
     catch
-        throw: {?MODULE, close = C, Reason} ->
-            ?LOG(C, {Reason, T}),
-            x(Reason, State);
-        throw: {?MODULE, abort, Reason}  ->
+        throw: {?MODULE, Tag, Reason}  ->
+            ?LOG(Tag, {Reason, T}),
             {stop, {shutdown, Reason}, State}
     end.
 
@@ -281,10 +282,9 @@ transition(shutdown, _) ->  %% DPR already send: ensure expected timeout
 
 %% Request to close the transport connection.
 transition({close = T, Pid}, #state{parent = Pid,
-                                    transport = TPid}
-                             = S) ->
+                                    transport = TPid}) ->
     diameter_peer:close(TPid),
-    close(T,S);
+    {stop, T};
 
 %% DPA reception has timed out.
 transition(dpa_timeout, _) ->
@@ -418,11 +418,11 @@ rcv('CER' = N, Pkt, #state{state = recv_CER} = 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} = S)
+rcv(Name, _, #state{state = PS})
   when PS /= 'Open';
        Name == 'CER';
        Name == 'CEA' ->
-    close({Name, PS}, S);
+    {stop, {Name, PS}};
 
 rcv(N, Pkt, S)
   when N == 'DWR';
@@ -497,15 +497,20 @@ build_answer('CER',
     #diameter_service{capabilities = #diameter_caps{origin_host = OH}}
         = Svc,
 
-    {SupportedApps, #diameter_caps{origin_host = DH} = RCaps, CEA}
+    {SupportedApps,
+     #diameter_caps{origin_host = DH} = RCaps,
+     #diameter_base_CEA{'Result-Code' = RC}
+     = CEA}
         = recv_CER(CER, S),
 
     try
-        [] == SupportedApps
-            andalso ?THROW({no_common_application, 5010}),
+        2001 == RC  %% DIAMETER_SUCCESS
+            orelse ?THROW({sent_CEA, RC}),
         register_everywhere({?MODULE, connection, OH, DH})
             orelse ?THROW({election_lost, 4003}),
-        {CEA, [fun open/4, Pkt, SupportedApps, RCaps]}
+        #diameter_base_CEA{'Inband-Security-Id' = [IS]}
+            = CEA,
+        {CEA, [fun open/5, Pkt, SupportedApps, RCaps, {accept, IS}]}
     catch
         ?FAILURE({Reason, RC}) ->
             {answer('CER', S) ++ [{'Result-Code', RC}],
@@ -613,7 +618,7 @@ recv_CER(CER, #state{service = Svc}) ->
 handle_CEA(#diameter_packet{header = #diameter_header{version = V},
                             bin = Bin}
            = Pkt,
-           #state{service = Svc}
+           #state{service = #diameter_service{capabilities = LCaps}}
            = S)
   when is_binary(Bin) ->
     ?LOG(recv, 'CEA'),
@@ -626,7 +631,11 @@ handle_CEA(#diameter_packet{header = #diameter_header{version = V},
 
     [] == Errors orelse close({errors, Errors}, S),
 
-    {SApps, #diameter_caps{origin_host = DH} = RCaps} = recv_CEA(CEA, S),
+    {SApps, [IS], #diameter_caps{origin_host = DH} = RCaps}
+        = recv_CEA(CEA, S),
+
+    #diameter_caps{origin_host = OH}
+        = LCaps,
 
     %% Ensure that we don't already have a connection to the peer in
     %% question. This isn't the peer election of 3588 except in the
@@ -634,40 +643,62 @@ handle_CEA(#diameter_packet{header = #diameter_header{version = V},
     %% receive a CER/CEA, the first that arrives wins the right to a
     %% connection with the peer.
 
-    #diameter_service{capabilities = #diameter_caps{origin_host = OH}}
-        = Svc,
-
     register_everywhere({?MODULE, connection, OH, DH})
-        orelse
-        close({'CEA', DH}, S),
+        orelse close({'CEA', DH}, S),
 
-    open(DPkt, SApps, RCaps, S).
+    open(DPkt, SApps, RCaps, {connect, IS}, S).
 
 %% recv_CEA/2
 
 recv_CEA(CEA, #state{service = Svc} = S) ->
     case diameter_capx:recv_CEA(CEA, Svc) of
-        {ok, {[], _}} ->
+        {ok, {_,_}} -> %% return from old code
+            close({'CEA', update}, S);
+        {ok, {[], _, _}} ->
             close({'CEA', no_common_application}, S);
-        {ok, T} ->
+        {ok, {_, [], _}} ->
+            close({'CEA', no_common_security}, S);
+        {ok, {_,_,_} = T} ->
             T;
         {error, Reason} ->
             close({'CEA', Reason}, S)
     end.
 
-%% open/4
+%% open/5
 
-open(Pkt, SupportedApps, RCaps, #state{parent = Pid,
-                                       service = Svc}
-                                = S) ->
-    #diameter_service{capabilities = #diameter_caps{origin_host = OH}
+open(Pkt, SupportedApps, RCaps, {Type, IS}, #state{parent = Pid,
+                                                   service = Svc}
+                                            = S) ->
+    #diameter_service{capabilities = #diameter_caps{origin_host = OH,
+                                                    inband_security_id = LS}
                                    = LCaps}
         = Svc,
     #diameter_caps{origin_host = DH}
         = RCaps,
+
+    tls_ack(lists:member(?TLS, LS), Type, IS, S),
     Pid ! {open, self(), {OH,DH}, {capz(LCaps, RCaps), SupportedApps, Pkt}},
+
     S#state{state = 'Open'}.
 
+%% We've advertised TLS support: tell the transport the result
+%% and expect a reply when the handshake is complete.
+tls_ack(true, Type, IS, #state{transport = TPid} = S) ->
+    Ref = make_ref(),
+    MRef = erlang:monitor(process, TPid),
+    TPid ! {diameter, {tls, Ref, Type, IS == ?TLS}},
+    receive
+        {diameter, {tls, Ref}} ->
+            erlang:demonitor(MRef, [flush]);
+        {'DOWN', MRef, process, _, _} = T ->
+            close({tls_ack, T}, S)
+    end;
+
+%% Or not. Don't send anything to the transport so that transports
+%% not supporting TLS work as before without modification.
+tls_ack(false, _, _, _) ->
+    ok.
+
 capz(#diameter_caps{} = L, #diameter_caps{} = R) ->
     #diameter_caps{}
         = list_to_tuple([diameter_caps | lists:zip(tl(tuple_to_list(L)),
diff --git a/lib/diameter/src/app/diameter_reg.erl b/lib/diameter/src/app/diameter_reg.erl
index 8e5f34c2c3..882b9da238 100644
--- a/lib/diameter/src/app/diameter_reg.erl
+++ b/lib/diameter/src/app/diameter_reg.erl
@@ -243,7 +243,8 @@ handle_call(state, _, State) ->
 handle_call(uptime, _, #state{id = Time} = State) ->
     {reply, diameter_lib:now_diff(Time), State};
 
-handle_call(_Req, _From, State) ->
+handle_call(Req, From, State) ->
+    ?UNEXPECTED([Req, From]),
     {reply, nok, State}.
 
 %%% ----------------------------------------------------------
@@ -251,7 +252,7 @@ handle_call(_Req, _From, State) ->
 %%% ----------------------------------------------------------
 
 handle_cast(Msg, State)->
-    warning_msg("received unexpected message:~n~w", [Msg]),
+    ?UNEXPECTED([Msg]),
     {noreply, State}.
 
 %%% ----------------------------------------------------------
@@ -264,7 +265,7 @@ handle_info({'DOWN', MRef, process, Pid, _}, State) ->
     {noreply, State};
 
 handle_info(Info, State) ->
-    warning_msg("received unknown info:~n~w", [Info]),
+    ?UNEXPECTED([Info]),
     {noreply, State}.
 
 %%% ----------------------------------------------------------
@@ -324,8 +325,3 @@ repl([], _, _) ->
 
 call(Request) ->
     gen_server:call(?SERVER, Request, infinity).
-
-%% warning_msg/2
-
-warning_msg(F, A) ->
-    ?diameter_warning("~p: " ++ F, [?MODULE | A]).
diff --git a/lib/diameter/src/app/diameter_service.erl b/lib/diameter/src/app/diameter_service.erl
index 63b0649dc4..421e36ccf5 100644
--- a/lib/diameter/src/app/diameter_service.erl
+++ b/lib/diameter/src/app/diameter_service.erl
@@ -463,7 +463,7 @@ handle_call(stop, _From, S) ->
 %% stating a monitor that waits for DOWN before returning.
 
 handle_call(Req, From, S) ->
-    ?REPORT(unknown_request, ?FUNC, [Req, From]),
+    unexpected(handle_call, [Req, From], S),
     {reply, nok, S}.
 
 %%% ---------------------------------------------------------------------------
@@ -471,7 +471,7 @@ handle_call(Req, From, S) ->
 %%% ---------------------------------------------------------------------------
 
 handle_cast(Req, S) ->
-    ?REPORT(unknown_request, ?FUNC, [Req]),
+    unexpected(handle_cast, [Req], S),
     {noreply, S}.
 
 %%% ---------------------------------------------------------------------------
@@ -553,8 +553,8 @@ transition({failover, TRef, Seqs}, S) ->
     failover(TRef, Seqs, S),
     ok;
 
-transition(Req, _) ->
-    ?REPORT(unknown_request, ?FUNC, [Req]),
+transition(Req, S) ->
+    unexpected(handle_info, [Req], S),
     ok.
 
 %%% ---------------------------------------------------------------------------
@@ -591,6 +591,9 @@ code_change(FromVsn, SvcName, Extra, #diameter_app{alias = Alias} = A) ->
 %% ===========================================================================
 %% ===========================================================================
 
+unexpected(F, A, #state{service_name = Name}) ->
+    ?UNEXPECTED(F, A ++ [Name]).
+
 cb([_|_] = M, F, A) ->
     eval(M, F, A);
 cb(Rec, F, A) ->
@@ -1398,15 +1401,15 @@ recv_answer(Timeout,
     %% is, from the last peer to which we've transmitted.
 
     receive
-        {answer = A, Ref, Rq, Pkt} ->     %% Answer from peer.
+        {answer = A, Ref, Rq, Pkt} ->     %% Answer from peer
             {A, Rq, Pkt};
-        {timeout = Reason, TRef, _} ->       %% No timely reply
+        {timeout = Reason, TRef, _} ->    %% No timely reply
             {error, Req, Reason};
-        {failover = Reason, TRef, false} ->  %% No alternative peer.
+        {failover = Reason, TRef, false} ->  %% No alternate peer
             {error, Req, Reason};
-        {failover, TRef, Transport} ->       %% Resend to alternate peer.
+        {failover, TRef, Transport} ->    %% Resend to alternate peer
             try_retransmit(Timeout, SvcName, Req, Transport);
-        {failover, TRef} ->  %% May have missed failover notification.
+        {failover, TRef} ->  %% May have missed failover notification
             Seqs = diameter_codec:sequence_numbers(RPkt),
             Pid  = whois(SvcName),
             is_pid(Pid) andalso (Pid ! {failover, TRef, Seqs}),
@@ -1685,9 +1688,9 @@ recv_request({Id, Alias}, T, TPid, Apps, Caps, Pkt) ->
 %%   DIAMETER_APPLICATION_UNSUPPORTED   3007
 %%      A request was sent for an application that is not supported.
 
-recv_request(false, {_, OH, OR}, TPid, _, _, Pkt) ->
-    ?LOG({error, application}, Pkt),
-    reply(answer_message({OH, OR, 3007}, collect_avps(Pkt)), ?BASE, TPid, Pkt).
+recv_request(false, T, TPid, _, _, Pkt) ->
+    As = collect_avps(Pkt),
+    protocol_error(3007, T, TPid, Pkt#diameter_packet{avps = As}).
 
 collect_avps(Pkt) ->
     case diameter_codec:collect_avps(Pkt) of
@@ -1706,13 +1709,9 @@ collect_avps(Pkt) ->
 %%      set to an unrecognized value, or that is inconsistent with the
 %%      AVP's definition.
 %%
-recv_request({_, OH, OR}, {TPid, _}, _, #diameter_packet{errors = [Bs | _],
-                                                         bin = Bin,
-                                                         avps = Avps}
-                                        = Pkt)
+recv_request(T, {TPid, _}, _, #diameter_packet{errors = [Bs | _]} = Pkt)
   when is_bitstring(Bs) ->
-    ?LOG({error, invalid_avp_bits}, Bin),
-    reply(answer_message({OH, OR, 3009}, Avps), ?BASE, TPid, Pkt);
+    protocol_error(3009, T, TPid, Pkt);
 
 %% Either we support this application but don't recognize the command
 %% or we're a relay and the command isn't proxiable.
@@ -1722,18 +1721,15 @@ recv_request({_, OH, OR}, {TPid, _}, _, #diameter_packet{errors = [Bs | _],
 %%      recognize or support.  This MUST be used when a Diameter node
 %%      receives an experimental command that it does not understand.
 %%
-recv_request({_, OH, OR},
+recv_request(T,
              {TPid, _},
              #diameter_app{id = Id},
              #diameter_packet{header = #diameter_header{is_proxiable = P},
-                              msg = M,
-                              avps = Avps,
-                              bin = Bin}
+                              msg = M}
              = Pkt)
   when ?APP_ID_RELAY /= Id, undefined == M;
        ?APP_ID_RELAY == Id, not P ->
-    ?LOG({error, command_unsupported}, Bin),
-    reply(answer_message({OH, OR, 3001}, Avps), ?BASE, TPid, Pkt);
+    protocol_error(3001, T, TPid, Pkt);
 
 %% Error bit was set on a request.
 %%
@@ -1742,15 +1738,12 @@ recv_request({_, OH, OR},
 %%      either set to an invalid combination, or to a value that is
 %%      inconsistent with the command code's definition.
 %%
-recv_request({_, OH, OR},
+recv_request(T,
              {TPid, _},
              _,
-             #diameter_packet{header = #diameter_header{is_error = true},
-                              avps = Avps,
-                              bin = Bin}
+             #diameter_packet{header = #diameter_header{is_error = true}}
              = Pkt) ->
-    ?LOG({error, error_bit}, Bin),
-    reply(answer_message({OH, OR, 3008}, Avps), ?BASE, TPid, Pkt);
+    protocol_error(3008, T, TPid, Pkt);
 
 %% A message in a locally supported application or a proxiable message
 %% in the relay application. Don't distinguish between the two since
@@ -1878,7 +1871,7 @@ resend(true, _, _, T, {TPid, _}, Pkt) ->  %% Route-Record loop
 resend(false,
        Opts,
        App,
-       {SvcName, _, _},
+       {SvcName, _, _} = T,
        {TPid, #diameter_caps{origin_host = {_, OH}}},
        #diameter_packet{header = Hdr0,
                         avps = Avps}
@@ -1887,46 +1880,41 @@ resend(false,
     Seq = diameter_session:sequence(),
     Hdr = Hdr0#diameter_header{hop_by_hop_id = Seq},
     Msg = [Hdr, Route | Avps],
-    %% Filter sender as ineligible receiver.
-    reply(call(SvcName, App, Msg, [{filter, {neg, {host, OH}}} | Opts]),
-          TPid,
-          Pkt).
+    resend(call(SvcName, App, Msg, Opts), T, TPid, Pkt).
 %% The incoming request is relayed with the addition of a
-%% Route-Record. Note the requirement on the return from call/4.
-%% This places a requirement on the values returned by the
-%% handle_answer and handle_error callbacks of the application module
-%% in question.
+%% Route-Record. Note the requirement on the return from call/4 below,
+%% which places a requirement on the value returned by the
+%% handle_answer callback of the application module in question.
+%%
+%% Note that there's nothing stopping the request from being relayed
+%% back to the sender. A pick_peer callback may want to avoid this but
+%% a smart peer might recognize the potential loop and choose another
+%% route. A less smart one will probably just relay the request back
+%% again and force us to detect the loop. A pick_peer that wants to
+%% avoid this can specify filter to avoid the possibility.
+%% Eg. {neg, {host, OH} where #diameter_caps{origin_host = {OH, _}}.
 %%
 %% RFC 6.3 says that a relay agent does not modify Origin-Host but
 %% says nothing about a proxy. Assume it should behave the same way.
 
-%% reply/3
+%% resend/4
 %%
 %% Relay a reply to a relayed request.
 
 %% Answer from the peer: reset the hop by hop identifier and send.
-reply(#diameter_packet{bin = B}
-      = Pkt,
-      TPid,
-      #diameter_packet{header = #diameter_header{hop_by_hop_id = Id},
-                       transport_data = TD}) ->
+resend(#diameter_packet{bin = B}
+       = Pkt,
+       _,
+       TPid,
+       #diameter_packet{header = #diameter_header{hop_by_hop_id = Id},
+                        transport_data = TD}) ->
     send(TPid, Pkt#diameter_packet{bin = diameter_codec:hop_by_hop_id(Id, B),
                                    transport_data = TD});
 %% TODO: counters
 
-%% Not. Ignoring the error feels harsh but there is no appropriate
-%% Result-Code for a protocol error (which this isn't really anyway)
-%% and the RFC doesn't provide any guidance how to act. A weakness
-%% here is that we don't deal well with a decode error: the request
-%% will simply timeout on the peer's end. Better would be to just send
-%% the answer (with modified hop by hop identifier) on regardless, at
-%% least in the relay case in which there's no examination of the
-%% answer. In the proxy case it's not clear that the callback won't
-%% examine the answer. Just be quiet here since a decode error causes
-%% the request process to crash (or not depending on the error and
-%% config and/or handle_answer callback).
-reply(_, _, _) ->
-    ok.
+%% Or not: DIAMETER_UNABLE_TO_DELIVER.
+resend(_, T, TPid, Pkt) ->
+    protocol_error(3002, T, TPid, Pkt).
 
 %% is_loop/4
 %%
@@ -1971,24 +1959,20 @@ 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 +2110,6 @@ 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
@@ -2482,6 +2456,7 @@ rpd(Pid, Alias, PDict) ->
 %%%
 %%% Output: {TransportPid, #diameter_caps{}, #diameter_app{}}
 %%%         | false
+%%%         | {error, Reason}
 %%% ---------------------------------------------------------------------------
 
 %% Initial call, from an arbitrary process.
@@ -2540,28 +2515,18 @@ get_destination(Msg, Dict) ->
     [str(get_avp_value(Dict, 'Destination-Realm', Msg)),
      str(get_avp_value(Dict, 'Destination-Host', Msg))].
 
-%% TODO:
-%%
-%% Should add some way of specifying destination directly so that the
-%% only requirement is that the prepare_request callback returns
-%% something specific. (eg. {host, DH}; that is, let the caller specify.)
-%%
-%% Also, there is no longer any need to call get_destination at all in
-%% the default case.
-
-str(T)
-  when T == undefined;
-       T == [] ->
+%% 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.
+str([]) ->
     undefined;
-str([X])
-  when is_list(X) ->
-    X;
 str(T) ->
     T.
 
 %% get_avp_value/3
 %%
-%% Support outgoing messages in one of three forms:
+%% Find an AVP in a message of one of three forms:
 %%
 %% - a message record (as generated from a .dia spec) or
 %% - a list of an atom message name followed by 2-tuple, avp name/value pairs.
@@ -2593,8 +2558,9 @@ get_avp_value(_, Name, [_MsgName | Avps]) ->
             undefined
     end;
 
-get_avp_value(Dict, Name, Rec)
-  when is_tuple(Rec) ->
+%% Message is typically a record but not necessarily: diameter:call/4
+%% can be passed an arbitrary term.
+get_avp_value(Dict, Name, Rec) ->
     try
         Dict:'#get-'(Name, Rec)
     catch
@@ -2690,7 +2656,8 @@ peers(Alias, RH, Filter, Peers) ->
     end.
 
 %% Place a peer whose Destination-Host/Realm matches those of the
-%% request at the front of the result list.
+%% request at the front of the result list. Could add some sort of
+%% 'sort' option to allow more control.
 
 ps([], _, _, {Ys, Ns}) ->
     lists:reverse(Ys, Ns);
@@ -2700,11 +2667,11 @@ ps([{_TPid, #diameter_caps{} = Caps} = TC | Rest], RH, Filter, Acc) ->
                               TC,
                               Acc)).
 
-pacc(true, true, TC, {Ts, Fs}) ->
-    {[TC|Ts], Fs};
-pacc(true, false, TC, {Ts, Fs}) ->
-    {Ts, [TC|Fs]};
-pacc(false, _, _, Acc) ->
+pacc(true, true, Peer, {Ts, Fs}) ->
+    {[Peer|Ts], Fs};
+pacc(true, false, Peer, {Ts, Fs}) ->
+    {Ts, [Peer|Fs]};
+pacc(_, _, _, Acc) ->
     Acc.
 
 %% caps_filter/3
@@ -2712,17 +2679,19 @@ pacc(false, _, _, Acc) ->
 caps_filter(C, RH, {neg, F}) ->
     not caps_filter(C, RH, F);
 
-caps_filter(C, RH, {all, L}) ->
+caps_filter(C, RH, {all, L})
+  when is_list(L) ->
     lists:all(fun(F) -> caps_filter(C, RH, F) end, L);
 
-caps_filter(C, RH, {any, L}) ->
+caps_filter(C, RH, {any, L})
+  when is_list(L) ->
     lists:any(fun(F) -> caps_filter(C, RH, F) end, L);
 
-caps_filter(#diameter_caps{origin_host = {_,H}}, [_,DH], host) ->
-    eq(undefined, DH, H);
+caps_filter(#diameter_caps{origin_host = {_,OH}}, [_,DH], host) ->
+    eq(undefined, DH, OH);
 
-caps_filter(#diameter_caps{origin_realm = {_,R}}, [DR,_], realm) ->
-    eq(undefined, DR, R);
+caps_filter(#diameter_caps{origin_realm = {_,OR}}, [DR,_], realm) ->
+    eq(undefined, DR, OR);
 
 caps_filter(C, _, Filter) ->
     caps_filter(C, Filter).
@@ -2738,6 +2707,9 @@ caps_filter(#diameter_caps{origin_host = {_,OH}}, {host, H}) ->
 caps_filter(#diameter_caps{origin_realm = {_,OR}}, {realm, R}) ->
     eq(any, R, OR);
 
+%% Anything else is expected to be an eval filter. Filter failure is
+%% documented as being equivalent to a non-matching filter.
+
 caps_filter(C, T) ->
     try
         {eval, F} = T,
@@ -2746,8 +2718,14 @@ caps_filter(C, T) ->
         _:_ -> false
     end.
 
-eq(X, A, B) ->
-    X == A orelse A == B.
+eq(Any, Id, PeerId) ->
+    Any == Id orelse try
+                         iolist_to_binary(Id) == iolist_to_binary(PeerId)
+                     catch
+                         _:_ -> false
+                     end.
+%% OctetString() can be specified as an iolist() so test for string
+%% rather then term equality.
 
 %% transports/1
 
diff --git a/lib/diameter/src/app/diameter_stats.erl b/lib/diameter/src/app/diameter_stats.erl
index b52d4cdcfb..71479afa95 100644
--- a/lib/diameter/src/app/diameter_stats.erl
+++ b/lib/diameter/src/app/diameter_stats.erl
@@ -207,7 +207,7 @@ handle_call({flush, Contrib}, _From, State) ->
     {reply, fetch(Contrib), State};
 
 handle_call(Req, From, State) ->
-    warning_msg("received unexpected request from ~p:~n~w", [From, Req]),
+    ?UNEXPECTED([Req, From]),
     {reply, nok, State}.
 
 %% ----------------------------------------------------------
@@ -219,7 +219,7 @@ handle_cast({incr, Rec}, State) ->
     {noreply, State};
 
 handle_cast(Msg, State) ->
-    warning_msg("received unexpected message:~n~w", [Msg]),
+    ?UNEXPECTED([Msg]),
     {noreply, State}.
 
 %% ----------------------------------------------------------
@@ -231,7 +231,7 @@ handle_info({'DOWN', _MRef, process, Pid, _}, State) ->
     {noreply, State};
 
 handle_info(Info, State) ->
-    warning_msg("received unknown info:~n~w", [Info]),
+    ?UNEXPECTED([Info]),
     {noreply, State}.
 
 %% ----------------------------------------------------------
@@ -340,8 +340,3 @@ cast(Msg) ->
 
 call(Request) ->
     gen_server:call(?SERVER, Request, infinity).
-
-%% warning_msg/2
-
-warning_msg(F, A) ->
-    ?diameter_warning("~p: " ++ F, [?MODULE | A]).
diff --git a/lib/diameter/src/app/diameter_sync.erl b/lib/diameter/src/app/diameter_sync.erl
index f7777ae809..ce2db4b3a2 100644
--- a/lib/diameter/src/app/diameter_sync.erl
+++ b/lib/diameter/src/app/diameter_sync.erl
@@ -204,37 +204,37 @@ handle_call(?REQUEST(Type, Name, Req, Max, Timeout),
     T = find(Name, QD),
     nq(queued(T) =< Max, T, {Type, From}, Name, Req, Timeout, State);
 
-handle_call(Request, _From, State) ->
-    {reply, call(Request, State), State}.
+handle_call(Request, From, State) ->
+    {reply, call(Request, From, State), State}.
 
-%% call/2
+%% call/3
 
-call(?CARP(Name), #state{queue = QD}) ->
+call(?CARP(Name), _, #state{queue = QD}) ->
     pcar(find(Name, QD));
 
-call(state, State) ->
+call(state, _, State) ->
     State;
 
-call(uptime, #state{time = T}) ->
+call(uptime, _, #state{time = T}) ->
     diameter_lib:now_diff(T);
 
-call({flush, Name}, #state{queue = QD}) ->
+call({flush, Name}, _, #state{queue = QD}) ->
     cancel(find(Name, QD));
 
-call(pending, #state{pending = N}) ->
+call(pending, _, #state{pending = N}) ->
     N;
 
-call({pending, Name}, #state{queue = QD}) ->
+call({pending, Name}, _, #state{queue = QD}) ->
     queued(find(Name, QD));
 
-call(queues, #state{queue = QD}) ->
+call(queues, _, #state{queue = QD}) ->
     fetch_keys(QD);
 
-call({pids, Name}, #state{queue = QD}) ->
+call({pids, Name}, _, #state{queue = QD}) ->
     plist(find(Name, QD));
 
-call(Req, _State) ->  %% ignore
-    warning_msg("received unexpected request:~n~w", [Req]),
+call(Req, From, _State) ->  %% ignore
+    ?UNEXPECTED(handle_call, [Req, From]),
     nok.
 
 %%% ----------------------------------------------------------
@@ -242,7 +242,7 @@ call(Req, _State) ->  %% ignore
 %%% ----------------------------------------------------------
 
 handle_cast(Msg, State) ->
-    warning_msg("received unexpected message:~n~w", [Msg]),
+    ?UNEXPECTED([Msg]),
     {noreply, State}.
 
 %%% ----------------------------------------------------------
@@ -267,7 +267,7 @@ info({'DOWN', MRef, process, Pid, Info},
                 queue = dq(fetch(Name, QD), Pid, Info, Name, QD)};
 
 info(Info, State) ->
-    warning_msg("received unknown info:~n~w", [Info]),
+    ?UNEXPECTED(handle_info, [Info]),
     State.
 
 reply({call, From}, T) ->
@@ -548,8 +548,3 @@ gen_call(Server, Req, Timeout) ->
         exit: _ ->
             timeout
     end.
-
-%% warning_msg/2
-
-warning_msg(F, A) ->
-    ?diameter_warning("~p: " ++ F, [?MODULE | A]).
diff --git a/lib/diameter/src/app/modules.mk b/lib/diameter/src/app/modules.mk
index a7a78b1a9d..c133e6f64e 100644
--- a/lib/diameter/src/app/modules.mk
+++ b/lib/diameter/src/app/modules.mk
@@ -22,17 +22,13 @@ SPEC_FILES = \
 	diameter_gen_base_accounting.dia \
 	diameter_gen_relay.dia
 
-MODULES = \
+RUNTIME_MODULES = \
 	diameter \
 	diameter_app \
-	diameter_callback \
 	diameter_capx \
 	diameter_config \
-	diameter_dbg \
 	diameter_codec \
 	diameter_dict \
-	diameter_exprecs \
-	diameter_info \
 	diameter_lib \
 	diameter_misc_sup \
 	diameter_peer \
@@ -49,6 +45,12 @@ MODULES = \
 	diameter_watchdog \
 	diameter_watchdog_sup
 
+HELP_MODULES = \
+	diameter_callback \
+	diameter_exprecs \
+	diameter_dbg \
+	diameter_info
+
 INTERNAL_HRL_FILES = \
 	diameter_internal.hrl \
 	diameter_types.hrl
diff --git a/lib/diameter/src/compiler/Makefile b/lib/diameter/src/compiler/Makefile
index 3ab76064ac..779013bfbc 100644
--- a/lib/diameter/src/compiler/Makefile
+++ b/lib/diameter/src/compiler/Makefile
@@ -94,16 +94,6 @@ info:
 	@echo ""
 
 # ----------------------------------------------------
-# Special Build Targets
-# ----------------------------------------------------
-
-# Invoked from ../app to add modules to the app file.
-$(APP_TARGET): force
-	M=`echo $(MODULES) | sed -e 's/^ *//' -e 's/ *$$//' -e 'y/ /,/'`; \
-	echo "/%COMPILER_MODULES%/s//$$M/;w;q" | tr ';' '\n' \
-	| ed -s $@
-
-# ----------------------------------------------------
 # Release Target
 # ----------------------------------------------------
 ifneq ($(ERL_TOP),)
diff --git a/lib/diameter/src/compiler/diameter_codegen.erl b/lib/diameter/src/compiler/diameter_codegen.erl
index 30caebc544..a33b07a3d3 100644
--- a/lib/diameter/src/compiler/diameter_codegen.erl
+++ b/lib/diameter/src/compiler/diameter_codegen.erl
@@ -37,7 +37,6 @@
          file/2,
          file/3]).
 
--include_lib("diameter/src/app/diameter_internal.hrl").
 -include("diameter_forms.hrl").
 
 %% Generated functions that could have no generated clauses will have
diff --git a/lib/diameter/src/transport/diameter_sctp.erl b/lib/diameter/src/transport/diameter_sctp.erl
index 46473e7bf1..cb024c77b1 100644
--- a/lib/diameter/src/transport/diameter_sctp.erl
+++ b/lib/diameter/src/transport/diameter_sctp.erl
@@ -411,6 +411,14 @@ transition({diameter, {send, Msg}}, S) ->
 transition({diameter, {close, Pid}}, #transport{parent = Pid}) ->
     stop;
 
+%% TLS over SCTP is described in RFC 3436 but has limitations as
+%% described in RFC 6083. The latter describes DTLS over SCTP, which
+%% addresses these limitations, DTLS itself being described in RFC
+%% 4347. TLS is primarily used over TCP, which the current RFC 3588
+%% draft acknowledges by equating TLS with TLS/TCP and DTLS/SCTP.
+transition({diameter, {tls, _Ref, _Type, _Bool}}, _) ->
+    stop;
+
 %% Listener process has died.
 transition({'DOWN', _, process, Pid, _}, #transport{mode = {accept, Pid}}) ->
     stop;
diff --git a/lib/diameter/src/transport/diameter_tcp.erl b/lib/diameter/src/transport/diameter_tcp.erl
index 653c114471..33b9daf0d9 100644
--- a/lib/diameter/src/transport/diameter_tcp.erl
+++ b/lib/diameter/src/transport/diameter_tcp.erl
@@ -45,6 +45,9 @@
 -define(LISTENER_TIMEOUT, 30000).
 -define(FRAGMENT_TIMEOUT, 1000).
 
+%% cb_info passed to ssl.
+-define(TCP_CB(Mod), {Mod, tcp, tcp_closed, tcp_error}).
+
 %% The same gen_server implementation supports three different kinds
 %% of processes: an actual transport process, one that will club it to
 %% death should the parent die before a connection is established, and
@@ -71,8 +74,8 @@
         {socket  :: inet:socket(),  %% accept or connect socket
          parent  :: pid(),          %% of process that started us
          module  :: module(),       %% gen_tcp-like module
-         frag = <<>> :: binary() | {tref(), frag()}}). %% message fragment
-
+         frag = <<>> :: binary() | {tref(), frag()},  %% message fragment
+         ssl     :: boolean() | [term()]}). %% ssl options
 %% The usual transport using gen_tcp can be replaced by anything
 %% sufficiently gen_tcp-like by passing a 'module' option as the first
 %% (for simplicity) transport option. The transport_module diameter_etcp
@@ -122,12 +125,15 @@ i({T, Ref, Mod, Pid, Opts, Addrs})
     %% that does nothing but kill us with the parent until call
     %% returns.
     {ok, MPid} = diameter_tcp_sup:start_child(#monitor{parent = Pid}),
-    Sock = i(T, Ref, Mod, Pid, Opts, Addrs),
+    {SslOpts, Rest} = ssl(Opts),
+    Sock = i(T, Ref, Mod, Pid, SslOpts, Rest, Addrs),
     MPid ! {stop, self()},  %% tell the monitor to die
-    setopts(Mod, Sock),
+    M = if SslOpts -> ssl; true -> Mod end,
+    setopts(M, Sock),
     #transport{parent = Pid,
-               module = Mod,
-               socket = Sock};
+               module = M,
+               socket = Sock,
+               ssl = SslOpts};
 
 %% A monitor process to kill the transport if the parent dies.
 i(#monitor{parent = Pid, transport = TPid} = S) ->
@@ -151,7 +157,29 @@ i({listen, LRef, APid, {Mod, Opts, Addrs}}) ->
     true = diameter_reg:add_new({?MODULE, listener, {LRef, {LAddr, LSock}}}),
     start_timer(#listener{socket = LSock}).
 
-%% i/6
+ssl(Opts) ->
+    {[SslOpts], Rest} = proplists:split(Opts, [ssl_options]),
+    {ssl_opts(SslOpts), Rest}.
+
+ssl_opts([]) ->
+    false;
+ssl_opts([{ssl_options, true}]) ->
+    true;
+ssl_opts([{ssl_options, Opts}])
+  when is_list(Opts) ->
+    Opts;
+ssl_opts(L) ->
+    ?ERROR({ssl_options, L}).
+
+%% i/7
+
+%% Establish a TLS connection before capabilities exchange ...
+i(Type, Ref, Mod, Pid, true, Opts, Addrs) ->
+    i(Type, Ref, ssl, Pid, [{cb_info, ?TCP_CB(Mod)} | Opts], Addrs);
+
+%% ... or not.
+i(Type, Ref, Mod, Pid, _, Opts, Addrs) ->
+    i(Type, Ref, Mod, Pid, Opts, Addrs).
 
 i(accept, Ref, Mod, Pid, Opts, Addrs) ->
     {LAddr, LSock} = listener(Ref, {Mod, Opts, Addrs}),
@@ -258,6 +286,8 @@ 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}.
 
@@ -332,17 +362,56 @@ t(T,S) ->
 
 %% transition/2
 
+%% Initial incoming message when we might need to upgrade to TLS:
+%% don't request another message until we know.
+transition({tcp, Sock, Bin}, #transport{socket = Sock,
+                                        parent = Pid,
+                                        frag = Head,
+                                        module = M,
+                                        ssl = Opts}
+                             = S)
+  when is_list(Opts) ->
+    case recv1(Head, Bin) of
+        {Msg, B} when is_binary(Msg) ->
+            diameter_peer:recv(Pid, Msg),
+            S#transport{frag = B};
+        Frag ->
+            setopts(M, Sock),
+            S#transport{frag = Frag}
+    end;
+
 %% Incoming message.
-transition({tcp, Sock, Data}, #transport{socket = Sock,
-                                         module = M}
-                              = S) ->
+transition({P, Sock, Bin}, #transport{socket = Sock,
+                                      module = M,
+                                      ssl = B}
+                           = S)
+  when P == tcp, not B;
+       P == ssl, B ->
     setopts(M, Sock),
-    recv(Data, S);
+    recv(Bin, S);
+
+%% Capabilties exchange has decided on whether or not to run over TLS.
+transition({diameter, {tls, Ref, Type, B}}, #transport{parent = Pid}
+                                            = S) ->
+    #transport{socket = Sock,
+               module = M}
+        = NS
+        = tls_handshake(Type, B, S),
+    Pid ! {diameter, {tls, Ref}},
+    setopts(M, Sock),
+    NS#transport{ssl = B};
 
-transition({tcp_closed, Sock}, #transport{socket = Sock}) ->
+transition({C, Sock}, #transport{socket = Sock,
+                                 ssl = B})
+  when C == tcp_closed, not B;
+       C == ssl_closed, B ->
     stop;
 
-transition({tcp_error, Sock, _Reason} = T, #transport{socket = Sock} = S) ->
+transition({E, Sock, _Reason} = T, #transport{socket = Sock,
+                                              ssl = B}
+                                   = S)
+  when E == tcp_error, not B;
+       E == ssl_error, B ->
     ?ERROR({T,S});
 
 %% Outgoing message.
@@ -379,80 +448,118 @@ transition({'DOWN', _, process, Pid, _}, #transport{parent = Pid}) ->
 
 %% Crash on anything unexpected.
 
+%% tls_handshake/3
+%%
+%% In the case that no tls message is received (eg. the service hasn't
+%% been configured to advertise TLS support) we will simply never ask
+%% for another TCP message, which will force the watchdog to
+%% eventually take us down.
+
+%% TLS has already been established with the connection.
+tls_handshake(_, _, #transport{ssl = true} = S) ->
+    S;
+
+%% Capabilities exchange negotiated TLS but transport was not
+%% configured with an options list.
+tls_handshake(_, true, #transport{ssl = false}) ->
+    ?ERROR(no_ssl_options);
+
+%% Capabilities exchange negotiated TLS: upgrade the connection.
+tls_handshake(Type, true, #transport{socket = Sock,
+                                     module = M,
+                                     ssl = Opts}
+                          = S) ->
+    {ok, SSock} = tls(Type, Sock, [{cb_info, ?TCP_CB(M)} | Opts]),
+    S#transport{socket = SSock,
+                module = ssl};
+
+%% Capabilities exchange has not negotiated TLS.
+tls_handshake(_, false, S) ->
+    S.
+
+tls(connect, Sock, Opts) ->
+    ssl:connect(Sock, Opts);
+tls(accept, Sock, Opts) ->
+    ssl:ssl_accept(Sock, Opts).
+
 %% recv/2
 %%
 %% Reassemble fragmented messages and extract multple message sent
 %% using Nagle.
 
 recv(Bin, #transport{parent = Pid, frag = Head} = S) ->
-    S#transport{frag = recv(Pid, Head, Bin)}.
+    case recv1(Head, Bin) of
+        {Msg, B} when is_binary(Msg) ->
+            diameter_peer:recv(Pid, Msg),
+            recv(B, S#transport{frag = <<>>});
+        Frag ->
+            S#transport{frag = Frag}
+    end.
 
-%% recv/3
+%% recv1/2
 
 %% No previous fragment.
-recv(Pid, <<>>, Bin) ->
-    rcv(Pid, Bin);
+recv1(<<>>, Bin) ->
+    rcv(Bin);
 
-recv(Pid, {TRef, Head}, Bin) ->
+recv1({TRef, Head}, Bin) ->
     erlang:cancel_timer(TRef),
-    rcv(Pid, Head, Bin).
+    rcv(Head, Bin).
 
-%% rcv/3
+%% rcv/2
 
 %% Not even the first four bytes of the header.
-rcv(Pid, Head, Bin)
+rcv(Head, Bin)
   when is_binary(Head) ->
-    rcv(Pid, <<Head/binary, Bin/binary>>);
+    rcv(<<Head/binary, Bin/binary>>);
 
 %% Or enough to know how many bytes to extract.
-rcv(Pid, {Len, N, Head, Acc}, Bin) ->
-    rcv(Pid, Len, N + size(Bin), Head, [Bin | Acc]).
+rcv({Len, N, Head, Acc}, Bin) ->
+    rcv(Len, N + size(Bin), Head, [Bin | Acc]).
 
-%% rcv/5
+%% rcv/4
 
 %% Extract a message for which we have all bytes.
-rcv(Pid, Len, N, Head, Acc)
+rcv(Len, N, Head, Acc)
   when Len =< N ->
-    rcv(Pid, rcv1(Pid, Len, bin(Head, Acc)));
+    rcv1(Len, bin(Head, Acc));
 
 %% Wait for more packets.
-rcv(_, Len, N, Head, Acc) ->
+rcv(Len, N, Head, Acc) ->
     {start_timer(), {Len, N, Head, Acc}}.
 
 %% rcv/2
 
 %% Nothing left.
-rcv(_, <<>> = Bin) ->
+rcv(<<>> = Bin) ->
     Bin;
 
 %% Well, this isn't good. Chances are things will go south from here
 %% but if we're lucky then the bytes we have extend to an intended
 %% message boundary and we can recover by simply discarding them,
 %% which is the result of receiving them.
-rcv(Pid, <<_:1/binary, Len:24, _/binary>> = Bin)
+rcv(<<_:1/binary, Len:24, _/binary>> = Bin)
   when Len < 20 ->
-    diameter_peer:recv(Pid, Bin),
-    <<>>;
+    {Bin, <<>>};
 
 %% Enough bytes to extract a message.
-rcv(Pid, <<_:1/binary, Len:24, _/binary>> = Bin)
+rcv(<<_:1/binary, Len:24, _/binary>> = Bin)
   when Len =< size(Bin) ->
-    rcv(Pid, rcv1(Pid, Len, Bin));
+    rcv1(Len, Bin);
 
 %% Or not: wait for more packets.
-rcv(_, <<_:1/binary, Len:24, _/binary>> = Head) ->
+rcv(<<_:1/binary, Len:24, _/binary>> = Head) ->
     {start_timer(), {Len, size(Head), Head, []}};
 
 %% Not even 4 bytes yet.
-rcv(_, Head) ->
+rcv(Head) ->
     {start_timer(), Head}.
 
-%% rcv1/3
+%% rcv1/2
 
-rcv1(Pid, Len, Bin) ->
+rcv1(Len, Bin) ->
     <<Msg:Len/binary, Rest/binary>> = Bin,
-    diameter_peer:recv(Pid, Msg),
-    Rest.
+    {Msg, Rest}.
 
 %% bin/[12]
 
@@ -489,15 +596,18 @@ flush(_, S) ->
 
 %% accept/2
 
-accept(gen_tcp, LSock) ->
-    gen_tcp:accept(LSock);
+accept(ssl, LSock) ->
+    case ssl:transport_accept(LSock) of
+        {ok, Sock} ->
+            {ssl:ssl_accept(Sock), Sock};
+        {error, _} = No ->
+            No
+    end;
 accept(Mod, LSock) ->
     Mod:accept(LSock).
 
 %% connect/4
 
-connect(gen_tcp, Host, Port, Opts) ->
-    gen_tcp:connect(Host, Port, Opts);
 connect(Mod, Host, Port, Opts) ->
     Mod:connect(Host, Port, Opts).
 
@@ -505,6 +615,8 @@ connect(Mod, Host, Port, Opts) ->
 
 send(gen_tcp, Sock, Bin) ->
     gen_tcp:send(Sock, Bin);
+send(ssl, Sock, Bin) ->
+    ssl:send(Sock, Bin);
 send(M, Sock, Bin) ->
     M:send(Sock, Bin).
 
@@ -512,6 +624,8 @@ send(M, Sock, Bin) ->
 
 setopts(gen_tcp, Sock, Opts) ->
     inet:setopts(Sock, Opts);
+setopts(ssl, Sock, Opts) ->
+    ssl:setopts(Sock, Opts);
 setopts(M, Sock, Opts) ->
     M:setopts(Sock, Opts).
 
@@ -527,5 +641,12 @@ setopts(M, Sock) ->
 
 lport(gen_tcp, Sock) ->
     inet:port(Sock);
+lport(ssl, Sock) ->
+    case ssl:sockname(Sock) of
+        {ok, {_Addr, PortNr}} ->
+            {ok, PortNr};
+        {error, _} = No ->
+            No
+    end;
 lport(M, Sock) ->
     M:port(Sock).