From 1fd9b919608b54e4d08340c45fe1cabb6975880c Mon Sep 17 00:00:00 2001
From: Anders Svensson <anders@erlang.org>
Date: Tue, 29 Aug 2017 14:33:47 +0200
Subject: Delay rotation of diameter_sctp outbound streams

For the same reason as unordered delivery is delayed in the grandparent
commit. Delivery is ordered only within a stream, so until a second
message is received from the peer, there's no guarantee that a second
outgoing request won't be received before the initial capablities
exchange message. Rotation begins upon reception of a second message
from the peer, messages being sent on stream 0 until then.
---
 lib/diameter/src/transport/diameter_sctp.erl | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

(limited to 'lib/diameter')

diff --git a/lib/diameter/src/transport/diameter_sctp.erl b/lib/diameter/src/transport/diameter_sctp.erl
index 0d8fb37629..86a98776c5 100644
--- a/lib/diameter/src/transport/diameter_sctp.erl
+++ b/lib/diameter/src/transport/diameter_sctp.erl
@@ -105,7 +105,7 @@
          packet = true :: boolean()        %% legacy transport_data?
                         | raw,
          message_cb = false :: false | diameter:eval(),
-         unordered = false :: boolean() | 0 | 1,   %% send unordered?
+         unordered = 1 :: boolean() | 0 | 1,       %% send unordered?
          send = false :: pid() | boolean()}).      %% sending process
 
 %% Monitor process state.
@@ -678,15 +678,16 @@ send(#diameter_packet{transport_data = {outstream, SId}}
      = S) ->
     send(SId rem OS, Msg, S);
 
-%% ... or not: send unordered on a lone stream ...
-send(Msg, #transport{unordered = true} = S) ->
-    send(0, Msg, S);
-
-%% ... or rotate through all.
-send(Msg, #transport{streams = {_, OS},
+%% ... or not: rotate when sending ordered ...
+send(Msg, #transport{unordered = false,
+                     streams = {_, OS},
                      os = N}
           = S) ->
-    send(N, Msg, S#transport{os = (N + 1) rem OS}).
+    send(N, Msg, S#transport{os = (N + 1) rem OS});
+
+%% ... or send only on the first stream, possibly unordered.
+send(Msg, S) ->
+    send(0, Msg, S).
 
 %% send/3
 
@@ -730,7 +731,6 @@ recv({_, #sctp_assoc_change{state = comm_up,
     %% Deal with different association id after peeloff on Solaris by
     %% taking the id from the first reception.
     up(S#transport{assoc_id = T == accept orelse Id,
-                   unordered = 1 == OS andalso 1,
                    streams = {IS, OS}});
 
 %% ... or not: try the next address.
@@ -785,11 +785,14 @@ recv(#transport{unordered = B} = S)
   when is_boolean(B) ->
     S;
 
-recv(#transport{unordered = 0, socket = Sock} = S) ->
+recv(#transport{unordered = 0, streams = {_, 1}, socket = Sock} = S) ->
     ok = inet:setopts(Sock, [{sctp_default_send_param,
                               #sctp_sndrcvinfo{flags = [unordered]}}]),
     S#transport{unordered = true};
 
+recv(#transport{unordered = 0} = S) ->
+    S#transport{unordered = false};
+
 recv(#transport{unordered = N} = S) ->
     S#transport{unordered = N-1}.
 
-- 
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