From 8ee98df1212cf4184c5d990e8f010f52a03cd728 Mon Sep 17 00:00:00 2001
From: Andreas Schultz <aschultz@tpip.net>
Date: Thu, 7 Jan 2016 11:22:47 +0100
Subject: ssl: introduce the notion of flights for dtls and tls

The flight concept was introduced by DTLS (RFC 4347) to optimize
the packing of DTLS records into UDP packets. This change
implments the flight concept in the the generic SSL connection
logic and add the queue logic to the TLS and DTLS stack.

The DTLS required resend handling is not implemented yet.

While the flight handling is only required for DTSL, it turns
out that the same mechanism can be usefull to TCP based TLS as
well.
With the current scheme each TLS record will be mapped into a
separate TCP frame. This causes more TCP frames to be generate
that necessary. On fast network this will have no impact, but
reducing the number of frames and thereby the number of
round trips can result in significant speedups on slow and
unreliable networks.

Conflicts:
	lib/ssl/src/tls_connection.erl
---
 lib/ssl/src/tls_connection.erl | 50 ++++++++++++++++++++++++------------------
 1 file changed, 29 insertions(+), 21 deletions(-)

(limited to 'lib/ssl/src/tls_connection.erl')

diff --git a/lib/ssl/src/tls_connection.erl b/lib/ssl/src/tls_connection.erl
index eaf2dd002d..9880befa94 100644
--- a/lib/ssl/src/tls_connection.erl
+++ b/lib/ssl/src/tls_connection.erl
@@ -49,8 +49,9 @@
 -export([next_record/1, next_event/3]).
 
 %% Handshake handling
--export([renegotiate/2, send_handshake/2, send_change_cipher/2,
-	reinit_handshake_data/1, handle_sni_extension/2]).
+-export([renegotiate/2, send_handshake/2, 
+	 queue_handshake/2, queue_change_cipher/2,
+	 reinit_handshake_data/1,  handle_sni_extension/2]).
 
 %% Alert and close handling
 -export([send_alert/2, handle_own_alert/4, handle_close_alert/3,
@@ -102,17 +103,32 @@ start_fsm(Role, Host, Port, Socket, {#ssl_options{erl_dist = true},_, Tracker} =
 	    Error
     end.
 
-send_handshake(Handshake, #state{negotiated_version = Version,
-				 socket = Socket,
-				 transport_cb = Transport,
-				 tls_handshake_history = Hist0,
-				 connection_states = ConnectionStates0} = State0) ->
+send_handshake(Handshake, State) ->
+    send_handshake_flight(queue_handshake(Handshake, State)).
+
+queue_handshake(Handshake, #state{negotiated_version = Version,
+				  tls_handshake_history = Hist0,
+				  flight_buffer = Flight0,
+				  connection_states = ConnectionStates0} = State0) ->
     {BinHandshake, ConnectionStates, Hist} =
 	encode_handshake(Handshake, Version, ConnectionStates0, Hist0),
-    Transport:send(Socket, BinHandshake),
     State0#state{connection_states = ConnectionStates,
-		tls_handshake_history = Hist
-	       }.
+		 tls_handshake_history = Hist,
+		 flight_buffer = Flight0 ++ [BinHandshake]}.
+
+send_handshake_flight(#state{socket = Socket,
+			     transport_cb = Transport,
+			     flight_buffer = Flight} = State0) ->
+    Transport:send(Socket, Flight),
+    State0#state{flight_buffer = []}.
+
+queue_change_cipher(Msg, #state{negotiated_version = Version,
+				  flight_buffer = Flight0,
+				  connection_states = ConnectionStates0} = State0) ->
+    {BinChangeCipher, ConnectionStates} =
+	encode_change_cipher(Msg, Version, ConnectionStates0),
+    State0#state{connection_states = ConnectionStates,
+		 flight_buffer = Flight0 ++ [BinChangeCipher]}.
 
 send_alert(Alert, #state{negotiated_version = Version,
 			 socket = Socket,
@@ -123,15 +139,6 @@ send_alert(Alert, #state{negotiated_version = Version,
     Transport:send(Socket, BinMsg),
     State0#state{connection_states = ConnectionStates}.
 
-send_change_cipher(Msg, #state{connection_states = ConnectionStates0,
-			       socket = Socket,
-			       negotiated_version = Version,
-			       transport_cb = Transport} = State0) ->
-    {BinChangeCipher, ConnectionStates} =
-	encode_change_cipher(Msg, Version, ConnectionStates0),
-    Transport:send(Socket, BinChangeCipher),
-    State0#state{connection_states = ConnectionStates}.
-
 reinit_handshake_data(State) ->
     %% premaster_secret, public_key_info and tls_handshake_info 
     %% are only needed during the handshake phase. 
@@ -141,7 +148,7 @@ reinit_handshake_data(State) ->
        public_key_info = undefined,
        tls_handshake_history = ssl_handshake:init_handshake_history()
      }.
-			  
+
 %%====================================================================
 %% tls_connection_sup API
 %%====================================================================
@@ -504,7 +511,8 @@ initial_state(Role, Host, Port, Socket, {SSLOptions, SocketOptions, Tracker}, Us
 	   allow_renegotiate = SSLOptions#ssl_options.client_renegotiation,
 	   start_or_recv_from = undefined,
 	   protocol_cb = ?MODULE,
-	   tracker = Tracker
+	   tracker = Tracker,
+	   flight_buffer = []
 	  }.
 
 
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