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, 3 insertions, 14 deletions

diff --git a/lib/ssl/src/dtls_handshake.erl b/lib/ssl/src/dtls_handshake.erl
index 4f48704cac..dbb03096ab 100644
--- a/lib/ssl/src/dtls_handshake.erl
+++ b/lib/ssl/src/dtls_handshake.erl
@@ -136,9 +136,9 @@ hello(#client_hello{client_version = ClientVersion}, _Options, {_,_,_,_,Connecti
 encode_handshake(Handshake, Version, MsgSeq) ->
     {MsgType, Bin} = enc_handshake(Handshake, Version),
     Len = byte_size(Bin),
-    EncHandshake = [MsgType, ?uint24(Len), ?uint16(MsgSeq), ?uint24(0), ?uint24(Len), Bin],
-    FragmentedHandshake = dtls_fragment(erlang:iolist_size(EncHandshake), MsgType, Len, MsgSeq, Bin, 0, []),
-    {EncHandshake, FragmentedHandshake}.
+    Enc = [MsgType, ?uint24(Len), ?uint16(MsgSeq), ?uint24(0), ?uint24(Len), Bin],
+    Frag = {MsgType, MsgSeq, Bin},
+    {Enc, Frag}.
 
 %%--------------------------------------------------------------------
 -spec get_dtls_handshake(#ssl_tls{}, #dtls_hs_state{} | binary()) ->
@@ -189,17 +189,6 @@ handle_server_hello_extensions(Version, SessionId, Random, CipherSuite,
 	    {Version, SessionId, ConnectionStates, ProtoExt, Protocol}
     end.
 
-dtls_fragment(Mss, MsgType, Len, MsgSeq, Bin, Offset, Acc)
-  when byte_size(Bin) + 12 < Mss ->
-    FragmentLen = byte_size(Bin),
-    BinMsg = [MsgType, ?uint24(Len), ?uint16(MsgSeq), ?uint24(Offset), ?uint24(FragmentLen), Bin],
-    lists:reverse([BinMsg|Acc]);
-dtls_fragment(Mss, MsgType, Len, MsgSeq, Bin, Offset, Acc) ->
-    FragmentLen = Mss - 12,
-    <<Fragment:FragmentLen/bytes, Rest/binary>> = Bin,
-    BinMsg = [MsgType, ?uint24(Len), ?uint16(MsgSeq), ?uint24(Offset), ?uint24(FragmentLen), Fragment],
-    dtls_fragment(Mss, MsgType, Len, MsgSeq, Rest, Offset + FragmentLen, [BinMsg|Acc]).
-
 get_dtls_handshake_aux(#ssl_tls{version = Version,
  				sequence_number = SeqNo,
  				fragment = Data}, HsState) ->