Merge branch 'anders/diameter/multiple_transport_modules/OTP-9885' into maint

* anders/diameter/multiple_transport_modules/OTP-9885:
  Maintain service_info callback data in process dictionary
  Maintain pid of started transport process in process dictionary
  Minor spec and backwards compatibility fix
  Update example code
  Update documentation
  Add diameter_transport for transport start indirection
  Allow multiple transport_module and transport_config

10 files changed, 444 insertions, 73 deletions

diff --git a/lib/diameter/doc/src/diameter.xml b/lib/diameter/doc/src/diameter.xml
index 93e2603c10..ec7bd2012e 100644
--- a/lib/diameter/doc/src/diameter.xml
+++ b/lib/diameter/doc/src/diameter.xml
@@ -764,15 +764,45 @@ Defaults to <c>diameter_tcp</c> if unspecified.</p>
 <p>
 The interface required of a transport module is documented in <seealso
 marker="diameter_transport">diameter_transport(3)</seealso>.</p>
+
+<p>
+Multiple <c>transport_module</c> and <c>transport_config</c>
+options are allowed.
+The order of these is significant in this case (and only in this case),
+a <c>transport_module</c> being paired with the first
+<c>transport_config</c> following it in the options list, or the
+default value for trailing modules.
+Transport starts will be attempted with each of the
+modules in order until one establishes a connection within the
+corresponding timeout (see <c>transport_config</c> below) or all fail.</p>
 </item>
 
 <tag><c>{transport_config, term()}</c></tag>
+<tag><c>{transport_config, term(), Unsigned32()}</c></tag>
 <item>
 <p>
 A term passed as the third argument to the <seealso
 marker="diameter_transport#start">start/3</seealso> function of
 the relevant <c>transport_module</c> in order to start a transport process.
 Defaults to the empty list if unspecified.</p>
+
+<p>
+The 3-tuple form additionally specifies an interval, in milliseconds,
+after which a started transport process should be terminated if it has
+not yet established a connection.
+For example, the following options on a connecting transport
+request a connection with one peer over SCTP or another
+(typically the same) over TCP.</p>
+
+<code>
+{transport_module, diameter_sctp}
+{transport_config, SctpOpts, 5000}
+{transport_module, diameter_tcp}
+{transport_config, TcpOpts}
+</code>
+
+<p>
+To listen on both SCTP and TCP, define one transport for each.</p>
 </item>
 
 <tag><c>{applications, [application_alias()]}</c></tag>
diff --git a/lib/diameter/examples/code/peer.erl b/lib/diameter/examples/code/peer.erl
index b07cd32b98..8fdeba57bf 100644
--- a/lib/diameter/examples/code/peer.erl
+++ b/lib/diameter/examples/code/peer.erl
@@ -117,6 +117,11 @@ server(T) ->
 %%
 %% Return config for a connecting transport.
 
+client({all, LA, RA, RP}) ->
+    [[M,{K,C}], T]
+        = [client({P, LA, RA, RP}) || P <- [sctp,tcp]],
+    [M, {K,C,2000} | T];
+
 client({T, LA, RA, RP}) ->
     [{transport_module, tmod(T)},
      {transport_config, [{ip, addr(LA)},
diff --git a/lib/diameter/src/base/diameter.erl b/lib/diameter/src/base/diameter.erl
index 336f0c1f2d..6703841f80 100644
--- a/lib/diameter/src/base/diameter.erl
+++ b/lib/diameter/src/base/diameter.erl
@@ -312,6 +312,7 @@ call(SvcName, App, Message) ->
 -type transport_opt()
    :: {transport_module, atom()}
     | {transport_config, any()}
+    | {transport_timeout, non_neg_integer() | infinity}
     | {applications, [app_alias()]}
     | {capabilities, [capability()]}
     | {capabilities_cb, evaluable()}
diff --git a/lib/diameter/src/base/diameter_peer.erl b/lib/diameter/src/base/diameter_peer.erl
index 3e78c4caef..a2a1c567d8 100644
--- a/lib/diameter/src/base/diameter_peer.erl
+++ b/lib/diameter/src/base/diameter_peer.erl
@@ -27,12 +27,15 @@
          up/2]).
 
 %% ... and the stack.
--export([start/3,
+-export([start/1,
          send/2,
          close/1,
          abort/1,
          notify/2]).
 
+%% Old interface only called from old code.
+-export([start/3]).  %% < diameter-1.2 (R15B02)
+
 %% Server start.
 -export([start_link/0]).
 
@@ -57,6 +60,11 @@
 %% Server state.
 -record(state, {id = now()}).
 
+%% Default transport_module/config.
+-define(DEFAULT_TMOD, diameter_tcp).
+-define(DEFAULT_TCFG, []).
+-define(DEFAULT_TTMO, infinity).
+
 %%% ---------------------------------------------------------------------------
 %%% # notify/2
 %%% ---------------------------------------------------------------------------
@@ -68,9 +76,108 @@ notify(SvcName, T) ->
 %%% # start/3
 %%% ---------------------------------------------------------------------------
 
-start(T, Opts, #diameter_service{} = Svc) ->
-    {Mod, Cfg} = split_transport(Opts),
-    apply(Mod, start, [T, Svc, Cfg]).
+%% From old code: make is restart.
+start(_T, _Opts, #diameter_service{}) ->
+    {error, restart}.
+
+%%% ---------------------------------------------------------------------------
+%%% # start/1
+%%% ---------------------------------------------------------------------------
+
+-spec start({T, [Opt], #diameter_service{}})
+   -> {TPid, [Addr], Tmo, Data}
+    | {error, [term()]}
+ when T    :: {connect|accept, diameter:transport_ref()},
+      Opt  :: diameter:transport_opt(),
+      TPid :: pid(),
+      Addr :: inet:ip_address(),
+      Tmo  :: non_neg_integer(),
+      Data :: {{T, Mod, Cfg}, [Mod], [{T, [Mod], Cfg}], [Err]},
+      Mod  :: module(),
+      Cfg  :: term(),
+      Err  :: term().
+
+%% Initial start.
+start({T, Opts, #diameter_service{} = Svc}) ->
+    start(T, Svc, pair(Opts, [], []), []);
+
+%% Subsequent start.
+start({#diameter_service{} = Svc, Tmo, {{T, _, Cfg}, Ms, Rest, Errs}}) ->
+    start(T, Ms, Cfg, Svc, Tmo, Rest, Errs).
+
+%% pair/3
+%%
+%% Pair transport modules with config.
+
+%% Another transport_module: accumulate it.
+pair([{transport_module, M} | Rest], Mods, Acc) ->
+    pair(Rest, [M|Mods], Acc);
+
+%% Another transport_config: accumulate another tuple.
+pair([{transport_config = T, C} | Rest], Mods, Acc) ->
+    pair([{T, C, ?DEFAULT_TTMO} | Rest], Mods, Acc);
+pair([{transport_config, C, Tmo} | Rest], Mods, Acc) ->
+    pair(Rest, [], acc({Mods, C, Tmo}, Acc));
+
+pair([_ | Rest], Mods, Acc) ->
+    pair(Rest, Mods, Acc);
+
+%% No transport_module or transport_config: defaults.
+pair([], [], []) ->  
+    [{[?DEFAULT_TMOD], ?DEFAULT_TCFG, ?DEFAULT_TTMO}];
+
+%% One transport_module, one transport_config.
+pair([], [M], [{[], Cfg, Tmo}]) ->
+    [{[M], Cfg, Tmo}];
+
+%% Trailing transport_module: default transport_config.
+pair([], [_|_] = Mods, Acc) ->
+    lists:reverse(acc({Mods, ?DEFAULT_TCFG, ?DEFAULT_TTMO}, Acc));
+
+pair([], [], Acc) ->
+    lists:reverse(def(Acc)).
+
+%% acc/2
+
+acc(T, Acc) ->
+    [T | def(Acc)].
+
+%% def/1
+%%
+%% Default module of previous pair if none were specified.
+
+def([{[], Cfg, Tmo} | Acc]) ->
+    [{[?DEFAULT_TMOD], Cfg, Tmo} | Acc];
+def(Acc) ->
+    Acc.
+
+%% start/4
+
+start(T, Svc, [{Ms, Cfg, Tmo} | Rest], Errs) ->
+    start(T, Ms, Cfg, Svc, Tmo, Rest, Errs);
+
+start(_, _, [], Errs) ->
+    {error, Errs}.
+
+%% start/7
+
+start(T, [], _, Svc, _, Rest, Errs) ->
+    start(T, Svc, Rest, Errs);
+
+start(T, [M|Ms], Cfg, Svc, Tmo, Rest, Errs) ->
+    case start(M, [T, Svc, Cfg]) of
+        {ok, TPid} ->
+            {TPid, [], Tmo, {{T, M, Cfg}, Ms, Rest, Errs}};
+        {ok, TPid, [_|_] = Addrs} ->
+            {TPid, Addrs, Tmo, {{T, M, Cfg}, Ms, Rest, Errs}};
+        E ->
+            start(T, Ms, Cfg, Svc, Tmo, Rest, [E|Errs])
+    end.
+
+%% start/2
+
+start(Mod, Args) ->
+    apply(Mod, start, Args).
 
 %%% ---------------------------------------------------------------------------
 %%% # up/[12]
@@ -204,21 +311,6 @@ bang(undefined = No, _) ->
 bang(Pid, T) ->
     Pid ! T.
 
-%% split_transport/1
-%%
-%% Split options into transport module, transport config and
-%% remaining options.
-
-split_transport(Opts) ->
-    {[M,C], _} = proplists:split(Opts, [transport_module,
-                                        transport_config]),
-    {value(M, diameter_tcp), value(C, [])}.
-
-value([{_,V}], _) ->
-    V;
-value([], V) ->
-    V.
-
 %% call/1
 
 call(Request) ->
diff --git a/lib/diameter/src/base/diameter_peer_fsm.erl b/lib/diameter/src/base/diameter_peer_fsm.erl
index 99644814d2..bbda62c32b 100644
--- a/lib/diameter/src/base/diameter_peer_fsm.erl
+++ b/lib/diameter/src/base/diameter_peer_fsm.erl
@@ -54,6 +54,12 @@
 -define(NO_INBAND_SECURITY, 0).
 -define(TLS, 1).
 
+%% Keys in process dictionary.
+-define(CB_KEY, cb).       %% capabilities callback
+-define(DWA_KEY, dwa).     %% outgoing DWA
+-define(Q_KEY, q).         %% transport start queue
+-define(START_KEY, start). %% start of connected transport
+
 %% A 2xxx series Result-Code. Not necessarily 2001.
 -define(IS_SUCCESS(N), 2 == (N) div 1000).
 
@@ -115,6 +121,11 @@
 %%% Output: Pid
 %%% ---------------------------------------------------------------------------
 
+-spec start(T, [Opt], #diameter_service{})
+   -> pid()
+ when T   :: {connect|accept, diameter:transport_ref()},
+      Opt :: diameter:transport_opt().
+
 %% diameter_config requires a non-empty list of applications on the
 %% service but diameter_service then constrains the list to any
 %% specified on the transport in question. Check here that the list is
@@ -143,18 +154,17 @@ init(T) ->
     proc_lib:init_ack({ok, self()}),
     gen_server:enter_loop(?MODULE, [], i(T)).
 
-i({WPid, T, Opts, #diameter_service{capabilities = Caps} = Svc0}) ->
-    putr(dwa, dwa(Caps)),
+i({WPid, T, Opts, #diameter_service{capabilities = Caps} = Svc}) ->
+    putr(?DWA_KEY, dwa(Caps)),
     {M, Ref} = T,
     {[Ts], Rest} = proplists:split(Opts, [capabilities_cb]),
-    putr(capabilities_cb, {Ref, [F || {_,F} <- Ts]}),
-    {ok, TPid, Svc} = start_transport(T, Rest, Svc0),
-    erlang:monitor(process, TPid),
+    putr(?CB_KEY, {Ref, [F || {_,F} <- Ts]}),
     erlang:monitor(process, WPid),
+    {TPid, Addrs} = start_transport(T, Rest, Svc),
     #state{parent = WPid,
            transport = TPid,
            mode = M,
-           service = Svc}.
+           service = svc(Svc, Addrs)}.
 %% The transport returns its local ip addresses so that different
 %% transports on the same service can use different local addresses.
 %% The local addresses are put into Host-IP-Address avps here when
@@ -164,18 +174,56 @@ i({WPid, T, Opts, #diameter_service{capabilities = Caps} = Svc0}) ->
 %% watchdog start (start/2) succeeds regardless so as not to crash the
 %% service.
 
-start_transport(T, Opts, Svc) ->
-    case diameter_peer:start(T, Opts, Svc) of
-        {ok, TPid} ->
-            {ok, TPid, Svc};
-        {ok, TPid, [_|_] = Addrs} ->
-            #diameter_service{capabilities = Caps0} = Svc,
-            Caps = Caps0#diameter_caps{host_ip_address = Addrs},
-            {ok, TPid, Svc#diameter_service{capabilities = Caps}};
+start_transport(T, Opts, #diameter_service{capabilities = Caps} = Svc) ->
+    Addrs0 = Caps#diameter_caps.host_ip_address,
+    start_transport(Addrs0, {T, Opts, Svc}).
+
+start_transport(Addrs0, T) ->
+    case diameter_peer:start(T) of
+        {TPid, Addrs, Tmo, Data} ->
+            erlang:monitor(process, TPid),
+            q_next(TPid, Addrs0, Tmo, Data),
+            {TPid, addrs(Addrs, Addrs0)};
         No ->
             exit({shutdown, No})
     end.
 
+addrs([], Addrs0) ->
+    Addrs0;
+addrs(Addrs, _) ->
+    Addrs.
+
+svc(Svc, []) ->
+    Svc;
+svc(Svc, Addrs) ->
+    readdr(Svc, Addrs).
+
+readdr(#diameter_service{capabilities = Caps0} = Svc, Addrs) ->
+    Caps = Caps0#diameter_caps{host_ip_address = Addrs},
+    Svc#diameter_service{capabilities = Caps}.
+
+%% The 4-tuple Data returned from diameter_peer:start/1 identifies the
+%% transport module/config use to start the transport process in
+%% question as well as any alternates to try if a connection isn't
+%% established within Tmo.
+q_next(TPid, Addrs0, Tmo, {_,_,_,_} = Data) ->
+    send_after(Tmo, {connection_timeout, TPid}),
+    putr(?Q_KEY, {Addrs0, Tmo, Data}).
+
+%% Connection has been established: retain the started
+%% pid/module/config in the process dictionary. This is a part of the
+%% interface defined by this module, so that the transport pid can be
+%% found when constructing service_info (in order to extract further
+%% information from it).
+keep_transport(TPid) ->
+    {_, _, {{_,_,_} = T, _, _, _}} = eraser(?Q_KEY),
+    putr(?START_KEY, {TPid, T}).
+
+send_after(infinity, _) ->
+    ok;
+send_after(Tmo, T) ->
+    erlang:send_after(Tmo, self(), T).
+
 %% handle_call/3
 
 handle_call(_, _, State) ->
@@ -240,25 +288,48 @@ eraser(Key) ->
 
 %% Connection to peer.
 transition({diameter, {TPid, connected, Remote}},
-           #state{state = PS,
+           #state{transport = TPid,
+                  state = PS,
                   mode = M}
            = S) ->
     'Wait-Conn-Ack' = PS,  %% assert
     connect = M,           %%
-    send_CER(S#state{mode = {M, Remote},
-                     transport = TPid});
+    keep_transport(TPid),
+    send_CER(S#state{mode = {M, Remote}});
 
 %% Connection from peer.
 transition({diameter, {TPid, connected}},
-           #state{state = PS,
+           #state{transport = TPid,
+                  state = PS,
                   mode = M,
                   parent = Pid}
            = S) ->
     'Wait-Conn-Ack' = PS,  %% assert
     accept = M,            %%
+    keep_transport(TPid),
     Pid ! {accepted, self()},
-    start_timer(S#state{state = recv_CER,
-                        transport = TPid});
+    start_timer(S#state{state = recv_CER});
+
+%% Connection established after receiving a connection_timeout
+%% message. This may be followed by an incoming message which arrived
+%% before the transport was killed and this can't be distinguished
+%% from one from the transport that's been started to replace it.
+transition({diameter, {_, connected}}, _) ->
+    {stop, connection_timeout};
+transition({diameter, {_, connected, _}}, _) ->
+    {stop, connection_timeout};
+
+%% Connection has timed out: start an alternate.
+transition({connection_timeout = T, TPid},
+           #state{transport = TPid,
+                  state = 'Wait-Conn-Ack'}
+           = S) ->
+    exit(TPid, {shutdown, T}),
+    start_next(S);
+
+%% Connect timeout after connection or alternate start: ignore.
+transition({connection_timeout, _}, _) ->
+    ok;
 
 %% Incoming message from the transport.
 transition({diameter, {recv, Pkt}}, S) ->
@@ -305,14 +376,21 @@ transition({resolve_port, _Pid} = T, #state{transport = TPid}) ->
     TPid ! T,
     ok;
 
-%% Parent or transport has died.
-transition({'DOWN', _, process, P, _},
-           #state{parent = Pid,
-                  transport = TPid})
-  when P == Pid;
-       P == TPid ->
+%% Parent has died.
+transition({'DOWN', _, process, WPid, _},
+           #state{parent = WPid}) ->
     stop;
 
+%% Transport has died before connection timeout.
+transition({'DOWN', _, process, TPid, _},
+           #state{transport = TPid}
+           = S) ->
+    start_next(S);
+
+%% Transport has died after connection timeout.
+transition({'DOWN', _, process, _, _}, _) ->
+    ok;
+
 %% State query.
 transition({state, Pid}, #state{state = S, transport = TPid}) ->
     Pid ! {self(), [S, TPid]},
@@ -320,6 +398,19 @@ transition({state, Pid}, #state{state = S, transport = TPid}) ->
 
 %% Crash on anything unexpected.
 
+%% start_next/1
+
+start_next(#state{service = Svc0} = S) ->
+    case getr(?Q_KEY) of
+        {Addrs0, Tmo, Data} ->
+            Svc = readdr(Svc0, Addrs0),
+            {TPid, Addrs} = start_transport(Addrs0, {Svc, Tmo, Data}),
+            S#state{transport = TPid,
+                    service = svc(Svc, Addrs)};
+        undefined ->
+            stop
+    end.
+
 %% send_CER/1
 
 send_CER(#state{mode = {connect, Remote},
@@ -649,7 +740,7 @@ rc([RC|_]) ->
 %% answer/2
 
 answer('DWR', _) ->
-    getr(dwa);
+    getr(?DWA_KEY);
 
 answer(Name, #state{service = #diameter_service{capabilities = Caps}}) ->
     a(Name, Caps).
@@ -749,15 +840,15 @@ caps(#state{service = Svc}) ->
 %% caps_cb/1
 
 caps_cb(Caps) ->
-    {Ref, Ts} = eraser(capabilities_cb),
-    ccb(Ts, [Ref, Caps]).
+    {Ref, Ts} = eraser(?CB_KEY),
+    caps_cb(Ts, [Ref, Caps]).
 
-ccb([], _) ->
+caps_cb([], _) ->
     ok;
-ccb([F | Rest], T) ->
+caps_cb([F | Rest], T) ->
     case diameter_lib:eval([F|T]) of
         ok ->
-            ccb(Rest, T);
+            caps_cb(Rest, T);
         N when ?IS_SUCCESS(N) ->  %% 2xxx result code: accept immediately
             N;
         Res ->
diff --git a/lib/diameter/src/modules.mk b/lib/diameter/src/modules.mk
index 7a700a6d53..5d3c4157ae 100644
--- a/lib/diameter/src/modules.mk
+++ b/lib/diameter/src/modules.mk
@@ -58,6 +58,7 @@ RT_MODULES = \
 	transport/diameter_tcp_sup \
 	transport/diameter_sctp \
 	transport/diameter_sctp_sup \
+	transport/diameter_transport \
 	transport/diameter_transport_sup
 
 # Handwritten (compile time) modules not included in the app file.
diff --git a/lib/diameter/src/transport/diameter_etcp.erl b/lib/diameter/src/transport/diameter_etcp.erl
index d925d62545..cd62cf34fa 100644
--- a/lib/diameter/src/transport/diameter_etcp.erl
+++ b/lib/diameter/src/transport/diameter_etcp.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 2010-2011. All Rights Reserved.
+%% Copyright Ericsson AB 2010-2012. All Rights Reserved.
 %%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -36,7 +36,9 @@
          send/2,
          close/1,
          setopts/2,
-         port/1]).
+         sockname/1,
+         peername/1,
+         getstat/1]).
 
 %% child start
 -export([start_link/1]).
@@ -113,10 +115,20 @@ close(Pid) ->
 setopts(_, _) ->
     ok.
 
-%% port/1
+%% sockname/1
 
-port(_) ->
-    3868.  %% We have no local port: fake it.
+sockname(_) ->
+    {error, ?MODULE}.
+
+%% peername/1
+
+peername(_) ->
+    {error, ?MODULE}.
+
+%% getstat/1
+
+getstat(_) ->
+    {error, ?MODULE}.
 
 %% start_link/1
 
diff --git a/lib/diameter/src/transport/diameter_sctp.erl b/lib/diameter/src/transport/diameter_sctp.erl
index 68b0342cd5..9a65834647 100644
--- a/lib/diameter/src/transport/diameter_sctp.erl
+++ b/lib/diameter/src/transport/diameter_sctp.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 2010-2011. All Rights Reserved.
+%% Copyright Ericsson AB 2010-2012. All Rights Reserved.
 %%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -37,12 +37,18 @@
          code_change/3,
          terminate/2]).
 
+-export([info/1]).  %% service_info callback
+
 -export([ports/0,
          ports/1]).
 
 -include_lib("kernel/include/inet_sctp.hrl").
 -include_lib("diameter/include/diameter.hrl").
 
+%% Keys into process dictionary.
+-define(INFO_KEY, info).
+-define(REF_KEY,  ref).
+
 -define(ERROR(T), erlang:error({T, ?MODULE, ?LINE})).
 
 %% The default port for a listener.
@@ -134,6 +140,24 @@ start_link(T) ->
                         diameter_lib:spawn_opts(server, [])).
 
 %% ---------------------------------------------------------------------------
+%% # info/1
+%% ---------------------------------------------------------------------------
+
+info({gen_sctp, Sock}) ->
+    lists:flatmap(fun(K) -> info(K, Sock) end,
+                  [{socket, sockname},
+                   {peer, peername},
+                   {statistics, getstat}]).
+
+info({K,F}, Sock) ->
+    case inet:F(Sock) of
+        {ok, V} ->
+            [{K,V}];
+        _ ->
+            []
+    end.
+
+%% ---------------------------------------------------------------------------
 %% # init/1
 %% ---------------------------------------------------------------------------
 
@@ -157,7 +181,7 @@ i({connect, Pid, Opts, Addrs, Ref}) ->
     RAs  = [diameter_lib:ipaddr(A) || {raddr, A} <- As],
     [RP] = [P || {rport, P} <- Ps] ++ [P || P <- [?DEFAULT_PORT], [] == Ps],
     {LAs, Sock} = open(Addrs, Rest, 0),
-    putr(ref, Ref),
+    putr(?REF_KEY, Ref),
     proc_lib:init_ack({ok, self(), LAs}),
     erlang:monitor(process, Pid),
     #transport{parent = Pid,
@@ -169,7 +193,7 @@ i({connect, _, _, _} = T) ->  %% from old code
 %% An accepting transport spawned by diameter.
 i({accept, Pid, LPid, Sock, Ref})
   when is_pid(Pid) ->
-    putr(ref, Ref),
+    putr(?REF_KEY, Ref),
     proc_lib:init_ack({ok, self()}),
     erlang:monitor(process, Pid),
     erlang:monitor(process, LPid),
@@ -181,7 +205,7 @@ i({accept, _, _, _} = T) ->  %% from old code
 
 %% An accepting transport spawned at association establishment.
 i({accept, Ref, LPid, Sock, Id}) ->
-    putr(ref, Ref),
+    putr(?REF_KEY, Ref),
     proc_lib:init_ack({ok, self()}),
     MRef = erlang:monitor(process, LPid),
     %% Wait for a signal that the transport has been started before
@@ -554,10 +578,9 @@ recv({_, #sctp_assoc_change{state = comm_up,
                 mode = {T, _},
                 socket = Sock}
      = S) ->
-    Ref = getr(ref),
+    Ref = getr(?REF_KEY),
     is_reference(Ref)  %% started in new code
-        andalso
-        (true = diameter_reg:add_new({?MODULE, T, {Ref, {Id, Sock}}})),
+        andalso publish(T, Ref, Id, Sock),
     up(S#transport{assoc_id = Id,
                    streams = {IS, OS}});
 
@@ -599,6 +622,10 @@ recv({_, #sctp_paddr_change{}}, _) ->
 recv({_, #sctp_pdapi_event{}}, _) ->
     ok.
 
+publish(T, Ref, Id, Sock) ->
+    true = diameter_reg:add_new({?MODULE, T, {Ref, {Id, Sock}}}),
+    putr(?INFO_KEY, {gen_sctp, Sock}).  %% for info/1
+
 %% up/1
 
 up(#transport{parent = Pid,
diff --git a/lib/diameter/src/transport/diameter_tcp.erl b/lib/diameter/src/transport/diameter_tcp.erl
index 78dbda6888..597f2f14d7 100644
--- a/lib/diameter/src/transport/diameter_tcp.erl
+++ b/lib/diameter/src/transport/diameter_tcp.erl
@@ -1,7 +1,7 @@
 %%
 %% %CopyrightBegin%
 %%
-%% Copyright Ericsson AB 2010-2011. All Rights Reserved.
+%% Copyright Ericsson AB 2010-2012. All Rights Reserved.
 %%
 %% The contents of this file are subject to the Erlang Public License,
 %% Version 1.1, (the "License"); you may not use this file except in
@@ -37,11 +37,17 @@
          code_change/3,
          terminate/2]).
 
+-export([info/1]).  %% service_info callback
+
 -export([ports/0,
          ports/1]).
 
 -include_lib("diameter/include/diameter.hrl").
 
+%% Keys into process dictionary.
+-define(INFO_KEY, info).
+-define(REF_KEY,  ref).
+
 -define(ERROR(T), erlang:error({T, ?MODULE, ?LINE})).
 
 -define(DEFAULT_PORT, 3868).  %% RFC 3588, ch 2.1
@@ -111,6 +117,33 @@ start_link(T) ->
                         diameter_lib:spawn_opts(server, [])).
 
 %% ---------------------------------------------------------------------------
+%% # info/1
+%% ---------------------------------------------------------------------------
+
+info({Mod, Sock}) ->
+    lists:flatmap(fun(K) -> info(Mod, K, Sock) end,
+                  [{socket, fun sockname/2},
+                   {peer, fun peername/2},
+                   {statistics, fun getstat/2}
+                   | ssl_info(Mod, Sock)]).
+
+info(Mod, {K,F}, Sock) ->
+    case F(Mod, Sock) of
+        {ok, V} ->
+            [{K,V}];
+        _ ->
+            []
+    end.
+
+ssl_info(ssl = M, Sock) ->
+    [{M, ssl_info(Sock)}];
+ssl_info(_, _) ->
+    [].
+
+ssl_info(Sock) ->
+    [{peercert, C} || {ok, C} <- [ssl:peercert(Sock)]].
+
+%% ---------------------------------------------------------------------------
 %% # init/1
 %% ---------------------------------------------------------------------------
 
@@ -133,7 +166,7 @@ i({T, Ref, Mod, Pid, Opts, Addrs})
     MPid ! {stop, self()},  %% tell the monitor to die
     M = if SslOpts -> ssl; true -> Mod end,
     setopts(M, Sock),
-    putr(ref, Ref),
+    putr(?REF_KEY, Ref),
     #transport{parent = Pid,
                module = M,
                socket = Sock,
@@ -191,7 +224,7 @@ i(accept = T, Ref, Mod, Pid, Opts, Addrs) ->
     {LAddr, LSock} = listener(Ref, {Mod, Opts, Addrs}),
     proc_lib:init_ack({ok, self(), [LAddr]}),
     Sock = ok(accept(Mod, LSock)),
-    true = diameter_reg:add_new({?MODULE, T, {Ref, Sock}}),
+    publish(Mod, T, Ref, Sock),
     diameter_peer:up(Pid),
     Sock;
 
@@ -202,10 +235,14 @@ i(connect = T, Ref, Mod, Pid, Opts, Addrs) ->
     RPort = get_port(RP),
     proc_lib:init_ack({ok, self(), [LAddr]}),
     Sock = ok(connect(Mod, RAddr, RPort, gen_opts(LAddr, Rest))),
-    true = diameter_reg:add_new({?MODULE, T, {Ref, Sock}}),
+    publish(Mod, T, Ref, Sock),
     diameter_peer:up(Pid, {RAddr, RPort}),
     Sock.
 
+publish(Mod, T, Ref, Sock) ->
+    true = diameter_reg:add_new({?MODULE, T, {Ref, Sock}}),
+    putr(?INFO_KEY, {Mod, Sock}).  %% for info/1
+
 ok({ok, T}) ->
     T;
 ok(No) ->
@@ -521,7 +558,7 @@ tls_handshake(Type, true, #transport{socket = Sock,
                                      ssl = Opts}
                           = S) ->
     {ok, SSock} = tls(Type, Sock, [{cb_info, ?TCP_CB(M)} | Opts]),
-    Ref = getr(ref),
+    Ref = getr(?REF_KEY),
     is_reference(Ref)  %% started in new code
         andalso
         (true = diameter_reg:add_new({?MODULE, Type, {Ref, SSock}})),
@@ -696,12 +733,32 @@ setopts(M, Sock) ->
 
 portnr(gen_tcp, Sock) ->
     inet:port(Sock);
-portnr(ssl, Sock) ->
-    case ssl:sockname(Sock) of
+portnr(M, Sock) ->
+    case M:sockname(Sock) of
         {ok, {_Addr, PortNr}} ->
             {ok, PortNr};
         {error, _} = No ->
             No
-    end;
-portnr(M, Sock) ->
-    M:port(Sock).
+    end.
+
+%% sockname/2
+
+sockname(gen_tcp, Sock) ->
+    inet:sockname(Sock);
+sockname(M, Sock) ->
+    M:sockname(Sock).
+
+%% peername/2
+
+peername(gen_tcp, Sock) ->
+    inet:peername(Sock);
+peername(M, Sock) ->
+    M:peername(Sock).
+
+%% getstat/2
+
+getstat(gen_tcp, Sock) ->
+    inet:getstat(Sock);
+getstat(M, Sock) ->
+    M:getstat(Sock).
+%% Note that ssl:getstat/1 doesn't yet exist in R15B01.
diff --git a/lib/diameter/src/transport/diameter_transport.erl b/lib/diameter/src/transport/diameter_transport.erl
new file mode 100644
index 0000000000..ff4b6bbc6d
--- /dev/null
+++ b/lib/diameter/src/transport/diameter_transport.erl
@@ -0,0 +1,55 @@
+%%
+%% %CopyrightBegin%
+%%
+%% Copyright Ericsson AB 2012. All Rights Reserved.
+%%
+%% The contents of this file are subject to the Erlang Public License,
+%% Version 1.1, (the "License"); you may not use this file except in
+%% compliance with the License. You should have received a copy of the
+%% Erlang Public License along with this software. If not, it can be
+%% retrieved online at http://www.erlang.org/.
+%%
+%% Software distributed under the License is distributed on an "AS IS"
+%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+%% the License for the specific language governing rights and limitations
+%% under the License.
+%%
+%% %CopyrightEnd%
+%%
+
+-module(diameter_transport).
+
+%%
+%% This module implements a transport start function that
+%% evaluates its config argument.
+%%
+
+%% Transport start functions
+-export([start/3,
+         select/3,
+         eval/3]).
+
+%% start/3
+
+%% Call a start function in this module ...
+start(T, Svc, {F,A}) ->
+    start(T, Svc, {?MODULE, F, [A]});
+
+%% ... or some other.
+start(T, Svc, F) ->
+    diameter_lib:eval([F, T, Svc]).
+
+%% select/3
+%%
+%% A start function that whose config argument is expected to return a
+%% new start function.
+
+select(T, Svc, F) ->
+    start(T, Svc, diameter_lib:eval([F, T, Svc])).
+
+%% eval/3
+%%
+%% A start function that simply evaluates its config argument.
+
+eval(_, _, F) ->
+    diameter_lib:eval(F).