Merge branch 'anders/diameter/transport/OTP-12929' into maint-17

* anders/diameter/transport/OTP-12929:
  Fix start order of alternate transports
  Log discarded answers

2 files changed, 10 insertions, 6 deletions

diff --git a/lib/diameter/src/base/diameter_peer.erl b/lib/diameter/src/base/diameter_peer.erl
index 96b6d404e0..b31aa65ce3 100644
--- a/lib/diameter/src/base/diameter_peer.erl
+++ b/lib/diameter/src/base/diameter_peer.erl
@@ -121,7 +121,7 @@ pair([{transport_module, M} | Rest], Mods, Acc) ->
 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, [], acc({lists:reverse(Mods), C, Tmo}, Acc));
 
 pair([_ | Rest], Mods, Acc) ->
     pair(Rest, Mods, Acc);
@@ -130,13 +130,16 @@ pair([_ | Rest], Mods, Acc) ->
 pair([], [], []) ->
     [{[?DEFAULT_TMOD], ?DEFAULT_TCFG, ?DEFAULT_TTMO}];
 
-%% One transport_module, one transport_config.
-pair([], [M], [{[], Cfg, Tmo}]) ->
-    [{[M], Cfg, Tmo}];
+%% One transport_module, one transport_config: ignore option order.
+%% That is, interpret [{transport_config, _}, {transport_module, _}]
+%% as if the order was reversed, not as config with default module and
+%% module with default config.
+pair([], [_] = Mods, [{[], Cfg, Tmo}]) ->
+    [{Mods, Cfg, Tmo}];
 
 %% Trailing transport_module: default transport_config.
 pair([], [_|_] = Mods, Acc) ->
-    lists:reverse(acc({Mods, ?DEFAULT_TCFG, ?DEFAULT_TTMO}, Acc));
+    pair([{transport_config, ?DEFAULT_TCFG}], Mods, Acc);
 
 pair([], [], Acc) ->
     lists:reverse(def(Acc)).
diff --git a/lib/diameter/src/base/diameter_traffic.erl b/lib/diameter/src/base/diameter_traffic.erl
index eb4bbae931..230a05fa11 100644
--- a/lib/diameter/src/base/diameter_traffic.erl
+++ b/lib/diameter/src/base/diameter_traffic.erl
@@ -261,7 +261,8 @@ recv(false, #request{ref = Ref, handler = Pid} = Req, _, Pkt, Dict0, _) ->
 %% any others are discarded.
 
 %% ... or not.
-recv(false, false, TPid, _, _, _) ->
+recv(false, false, TPid, Pkt, _, _) ->
+    ?LOG(discarded, Pkt#diameter_packet.header),
     incr(TPid, {{unknown, 0}, recv, discarded}),
     ok.