dtls: rework handshake flight encodeing

The MSS might change between sending the a flight and possible
resend. We therefore have to be able to fragment the records
differently for resent.

Encoding and fragmenting of handshake record therefor needs to
be done independently.

With this change the handshake is encoded to it's full length
first, then queued to a flight. The fragmentation is handled
during assembly of the flights datagram.

Conflicts:
	lib/ssl/src/dtls_connection.erl

1 files changed, 13 insertions, 2 deletions

diff --git a/lib/ssl/src/ssl_record.erl b/lib/ssl/src/ssl_record.erl
index 0a086f5eeb..2bd282c664 100644
--- a/lib/ssl/src/ssl_record.erl
+++ b/lib/ssl/src/ssl_record.erl
@@ -320,14 +320,25 @@ encode_handshake(Frag, Version,
 					   beast_mitigation = BeastMitigation,
 					   security_parameters =
 					       #security_parameters{bulk_cipher_algorithm = BCA}}} = 
-		     ConnectionStates) ->
+		     ConnectionStates)
+when is_list(Frag) ->
     case iolist_size(Frag) of
 	N  when N > ?MAX_PLAIN_TEXT_LENGTH ->
 	    Data = split_bin(iolist_to_binary(Frag), ?MAX_PLAIN_TEXT_LENGTH, Version, BCA, BeastMitigation),
 	    encode_iolist(?HANDSHAKE, Data, Version, ConnectionStates);
 	_  ->
 	    encode_plain_text(?HANDSHAKE, Version, Frag, ConnectionStates)
-    end.
+    end;
+%% TODO: this is a workarround for DTLS
+%%
+%% DTLS need to select the connection write state based on Epoch it wants to
+%% send this fragment in. That Epoch does not nessarily has to be the same
+%% as the current_write epoch.
+%% The right solution might be to pass the WriteState instead of the ConnectionStates,
+%% however, this will require substantion API changes.
+encode_handshake(Frag, Version, ConnectionStates) ->
+    encode_plain_text(?HANDSHAKE, Version, Frag, ConnectionStates).
+
 %%--------------------------------------------------------------------
 -spec encode_alert_record(#alert{}, ssl_version(), #connection_states{}) ->
 				 {iolist(), #connection_states{}}.