ssl: Implement DTLS state machine

Beta DTLS, not production ready. Only very basically tested, and
not everything in the SPEC is implemented and some things
are hard coded that should not be, so this implementation can not be consider
secure.

Refactor "TLS connection state" and socket handling, to facilitate
DTLS implementation.

Create dtls "listner" (multiplexor) process that spawns
DTLS connection process handlers.

Handle DTLS fragmentation.

Framework for handling retransmissions.

Replay Detection is not implemented yet.

Alerts currently always handled as in TLS.

1 files changed, 273 insertions, 282 deletions

diff --git a/lib/ssl/src/dtls_handshake.erl b/lib/ssl/src/dtls_handshake.erl
index c6535d5928..af3708ddb7 100644
--- a/lib/ssl/src/dtls_handshake.erl
+++ b/lib/ssl/src/dtls_handshake.erl
@@ -18,15 +18,15 @@
 %% %CopyrightEnd%
 -module(dtls_handshake).
 
+-include("dtls_connection.hrl").
 -include("dtls_handshake.hrl").
 -include("dtls_record.hrl").
 -include("ssl_internal.hrl").
 -include("ssl_alert.hrl").
 
--export([client_hello/8, client_hello/9, hello/4,
-	 hello_verify_request/1, get_dtls_handshake/2,
-	 dtls_handshake_new_flight/1, dtls_handshake_new_epoch/1,
-	 encode_handshake/3]).
+-export([client_hello/8, client_hello/9, cookie/4, hello/4, 
+	 hello_verify_request/2, get_dtls_handshake/3, fragment_handshake/2,
+	 handshake_bin/2, encode_handshake/3]).
 
 -type dtls_handshake() :: #client_hello{} | #hello_verify_request{} | 
 			  ssl_handshake:ssl_handshake().
@@ -62,9 +62,10 @@ client_hello(Host, Port, Cookie, ConnectionStates,
     Version =  dtls_record:highest_protocol_version(Versions),
     Pending = ssl_record:pending_connection_state(ConnectionStates, read),
     SecParams = maps:get(security_parameters, Pending),
-    CipherSuites = ssl_handshake:available_suites(UserSuites, Version),
+    TLSVersion = dtls_v1:corresponding_tls_version(Version),
+    CipherSuites = ssl_handshake:available_suites(UserSuites, TLSVersion),
 
-    Extensions = ssl_handshake:client_hello_extensions(Host, dtls_v1:corresponding_tls_version(Version), CipherSuites,
+    Extensions = ssl_handshake:client_hello_extensions(Host, TLSVersion, CipherSuites,
 						SslOpts, ConnectionStates, Renegotiation),
 
     Id = ssl_session:client_id({Host, Port, SslOpts}, Cache, CacheCb, OwnCert),
@@ -96,72 +97,51 @@ hello(#client_hello{client_version = ClientVersion} = Hello,
       #ssl_options{versions = Versions} = SslOpts,
       Info, Renegotiation) ->
     Version = ssl_handshake:select_version(dtls_record, ClientVersion, Versions),
-    %%
-    %% TODO: handle Cipher Fallback
-    %%
     handle_client_hello(Version, Hello, SslOpts, Info, Renegotiation).
 
--spec hello_verify_request(binary()) -> #hello_verify_request{}.
+cookie(Key, Address, Port, #client_hello{client_version = {Major, Minor},
+					 random = Random,
+					 session_id = SessionId,
+					 cipher_suites = CipherSuites,
+					 compression_methods = CompressionMethods}) ->
+    CookieData = [address_to_bin(Address, Port),
+		  <<?BYTE(Major), ?BYTE(Minor)>>,
+		  Random, SessionId, CipherSuites, CompressionMethods],
+    crypto:hmac(sha, Key, CookieData).
+
+-spec hello_verify_request(binary(),  dtls_record:dtls_version()) -> #hello_verify_request{}.
 %%
 %% Description: Creates a hello verify request message sent by server to
 %% verify client
 %%--------------------------------------------------------------------
-hello_verify_request(Cookie) ->
-    %% TODO: DTLS Versions?????
-    #hello_verify_request{protocol_version = {254, 255}, cookie = Cookie}.
+hello_verify_request(Cookie, Version) ->
+    #hello_verify_request{protocol_version = Version, cookie = Cookie}.
 
 %%--------------------------------------------------------------------
 
-%% %%--------------------------------------------------------------------
-encode_handshake(Handshake, Version, MsgSeq) ->
+encode_handshake(Handshake, Version, Seq) ->
     {MsgType, Bin} = enc_handshake(Handshake, Version),
     Len = byte_size(Bin),
-    Enc = [MsgType, ?uint24(Len), ?uint16(MsgSeq), ?uint24(0), ?uint24(Len), Bin],
-    Frag = {MsgType, MsgSeq, Bin},
-    {Enc, Frag}.
+    [MsgType, ?uint24(Len), ?uint16(Seq), ?uint24(0), ?uint24(Len), Bin].
 
-%%--------------------------------------------------------------------
--spec get_dtls_handshake(#ssl_tls{}, #dtls_hs_state{} | undefined) ->
-				{[dtls_handshake()], #dtls_hs_state{}} | {retransmit, #dtls_hs_state{}}.
-%%
-%% Description: Given a DTLS state and new data from ssl_record, collects
-%% and returns it as a list of handshake messages, also returns a new
-%% DTLS state
-%%--------------------------------------------------------------------
-get_dtls_handshake(Records, undefined) ->
-    HsState = #dtls_hs_state{highest_record_seq = 0,
-			     starting_read_seq = 0,
-			     fragments = gb_trees:empty(),
-			     completed = []},
-    get_dtls_handshake(Records, HsState);
-get_dtls_handshake(Records, HsState0) when is_list(Records) ->
-    HsState1 = lists:foldr(fun get_dtls_handshake_aux/2, HsState0, Records),
-    get_dtls_handshake_completed(HsState1);
-get_dtls_handshake(Record, HsState0) when is_record(Record, ssl_tls) ->
-    HsState1 = get_dtls_handshake_aux(Record, HsState0),
-    get_dtls_handshake_completed(HsState1).
+fragment_handshake(Bin, _) when is_binary(Bin)-> 
+    %% This is the change_cipher_spec not a "real handshake" but part of the flight
+    Bin;
+fragment_handshake([MsgType, Len, Seq, _, Len, Bin], Size) ->
+    Bins = bin_fragments(Bin, Size),
+    handshake_fragments(MsgType, Seq, Len, Bins, []).
 
+handshake_bin([Type, Length, Data], Seq) ->	
+    handshake_bin(Type, Length, Seq, Data).
+    
 %%--------------------------------------------------------------------
--spec dtls_handshake_new_epoch(#dtls_hs_state{}) -> #dtls_hs_state{}.
+-spec get_dtls_handshake(dtls_record:dtls_version(), binary(), #protocol_buffers{}) ->
+     {[{dtls_handshake(), binary()}], #protocol_buffers{}} | {more_data, #protocol_buffers{}}.
 %%
-%% Description: Reset the DTLS decoder state for a new Epoch
+%% Description: ...
 %%--------------------------------------------------------------------
-%% dtls_handshake_new_epoch(<<>>) ->
-%%     dtls_hs_state_init();
-dtls_handshake_new_epoch(HsState) ->
-    HsState#dtls_hs_state{highest_record_seq = 0,
-			  starting_read_seq = HsState#dtls_hs_state.current_read_seq,
-			  fragments = gb_trees:empty(), completed = []}.
-
-%--------------------------------------------------------------------
--spec dtls_handshake_new_flight(integer() | undefined) -> #dtls_hs_state{}.
-%
-% Description: Init the DTLS decoder state for a new Flight
-dtls_handshake_new_flight(ExpectedReadReq) ->
-    #dtls_hs_state{current_read_seq = ExpectedReadReq,
-		   highest_record_seq = 0,
-		   starting_read_seq = 0,
-		   fragments = gb_trees:empty(), completed = []}.
+get_dtls_handshake(Version, Fragment, ProtocolBuffers) ->
+    handle_fragments(Version, Fragment, ProtocolBuffers, []).
 
 %%--------------------------------------------------------------------
 %%% Internal functions
@@ -170,27 +150,29 @@ handle_client_hello(Version, #client_hello{session_id = SugesstedId,
 					   cipher_suites = CipherSuites,
 					   compression_methods = Compressions,
 					   random = Random,
-					   extensions = #hello_extensions{elliptic_curves = Curves,
-									  signature_algs = ClientHashSigns} = HelloExt},
+					   extensions =
+					       #hello_extensions{elliptic_curves = Curves,
+								 signature_algs = ClientHashSigns} = HelloExt},
 		    #ssl_options{versions = Versions,
 				 signature_algs = SupportedHashSigns} = SslOpts,
 		    {Port, Session0, Cache, CacheCb, ConnectionStates0, Cert, _}, Renegotiation) ->
     case dtls_record:is_acceptable_version(Version, Versions) of
 	true ->
+	    TLSVersion = dtls_v1:corresponding_tls_version(Version),
 	    AvailableHashSigns = ssl_handshake:available_signature_algs(
-				   ClientHashSigns, SupportedHashSigns, Cert,
-				   dtls_v1:corresponding_tls_version(Version)),
-	    ECCCurve = ssl_handshake:select_curve(Curves, ssl_handshake:supported_ecc(Version)),
+				   ClientHashSigns, SupportedHashSigns, Cert,TLSVersion),
+	    ECCCurve = ssl_handshake:select_curve(Curves, ssl_handshake:supported_ecc(TLSVersion)),
 	    {Type, #session{cipher_suite = CipherSuite} = Session1}
 		= ssl_handshake:select_session(SugesstedId, CipherSuites, AvailableHashSigns, Compressions,
-					       Port, Session0#session{ecc = ECCCurve}, Version,
+					       Port, Session0#session{ecc = ECCCurve}, TLSVersion,
 					       SslOpts, Cache, CacheCb, Cert),
 	    case CipherSuite of
 		no_suite ->
 		    ?ALERT_REC(?FATAL, ?INSUFFICIENT_SECURITY);
 		_ ->
 		    {KeyExAlg,_,_,_} = ssl_cipher:suite_definition(CipherSuite),
-		    case ssl_handshake:select_hashsign(ClientHashSigns, Cert, KeyExAlg, SupportedHashSigns, Version) of
+		    case ssl_handshake:select_hashsign(ClientHashSigns, Cert, KeyExAlg, 
+						       SupportedHashSigns, TLSVersion) of
 			#alert{} = Alert ->
 			    Alert;
 			HashSign ->
@@ -228,214 +210,15 @@ handle_server_hello_extensions(Version, SessionId, Random, CipherSuite,
 	    {Version, SessionId, ConnectionStates, ProtoExt, Protocol}
     end.
 
-get_dtls_handshake_completed(HsState = #dtls_hs_state{completed = Completed}) ->
-    {lists:reverse(Completed), HsState#dtls_hs_state{completed = []}}.
-
-get_dtls_handshake_aux(#ssl_tls{version = Version,
- 				sequence_number = SeqNo,
- 				fragment = Data}, HsState) ->
-    get_dtls_handshake_aux(Version, SeqNo, Data, HsState).
-
-get_dtls_handshake_aux(Version, SeqNo,
- 		       <<?BYTE(Type), ?UINT24(Length),
- 			 ?UINT16(MessageSeq),
- 			 ?UINT24(FragmentOffset), ?UINT24(FragmentLength),
- 			 Body:FragmentLength/binary, Rest/binary>>,
- 		       HsState0) ->
-    case reassemble_dtls_fragment(SeqNo, Type, Length, MessageSeq,
-				  FragmentOffset, FragmentLength,
-				  Body, HsState0) of
- 	{HsState1, HighestSeqNo, MsgBody} ->
- 	    HsState2 = dec_dtls_fragment(Version, HighestSeqNo, Type, Length, MessageSeq, MsgBody, HsState1),
- 	    HsState3 = process_dtls_fragments(Version, HsState2),
- 	    get_dtls_handshake_aux(Version, SeqNo, Rest, HsState3);
-
- 	HsState2 ->
- 	    HsState3 = process_dtls_fragments(Version, HsState2),
- 	    get_dtls_handshake_aux(Version, SeqNo, Rest, HsState3)
-     end;
-
-get_dtls_handshake_aux(_Version, _SeqNo, <<>>, HsState) ->
-    HsState.
-
-dec_dtls_fragment(Version, SeqNo, Type, Length, MessageSeq, MsgBody,
- 		  HsState = #dtls_hs_state{highest_record_seq = HighestSeqNo, completed = Acc}) ->
-    Raw = <<?BYTE(Type), ?UINT24(Length), ?UINT16(MessageSeq), ?UINT24(0), ?UINT24(Length), MsgBody/binary>>,
-    H = decode_handshake(Version, Type, MsgBody),
-    HsState#dtls_hs_state{completed = [{H,Raw}|Acc], highest_record_seq = erlang:max(HighestSeqNo, SeqNo)}.
-
-process_dtls_fragments(Version,
- 		       HsState0 = #dtls_hs_state{current_read_seq = CurrentReadSeq,
- 						 fragments = Fragments0}) ->
-    case gb_trees:is_empty(Fragments0) of
- 	true ->
- 	    HsState0;
- 	_ ->
- 	    case gb_trees:smallest(Fragments0) of
- 		{CurrentReadSeq, {SeqNo, Type, Length, CurrentReadSeq, {Length, [{0, Length}], MsgBody}}} ->
- 		    HsState1 = dtls_hs_state_process_seq(HsState0),
- 		    HsState2 = dec_dtls_fragment(Version, SeqNo, Type, Length, CurrentReadSeq, MsgBody, HsState1),
- 		    process_dtls_fragments(Version, HsState2);
- 		_ ->
- 		    HsState0
- 	    end
-     end.
-
-dtls_hs_state_process_seq(HsState0 = #dtls_hs_state{current_read_seq = CurrentReadSeq,
- 						    fragments = Fragments0}) ->
-    Fragments1 = gb_trees:delete_any(CurrentReadSeq, Fragments0),
-    HsState0#dtls_hs_state{current_read_seq = CurrentReadSeq + 1,
- 			   fragments = Fragments1}.
-
-dtls_hs_state_add_fragment(MessageSeq, Fragment, HsState0 = #dtls_hs_state{fragments = Fragments0}) ->
-    Fragments1 = gb_trees:enter(MessageSeq, Fragment, Fragments0),
-    HsState0#dtls_hs_state{fragments = Fragments1}.
-
-reassemble_dtls_fragment(SeqNo, Type, Length, MessageSeq, 0, Length,
- 			 Body, HsState0 = #dtls_hs_state{current_read_seq = undefined})
-  when Type == ?CLIENT_HELLO;
-       Type == ?SERVER_HELLO;
-        Type == ?HELLO_VERIFY_REQUEST ->
-    %% First message, should be client hello
-    %% return the current message and set the next expected Sequence
-    %%
-    %% Note: this could (should?) be restricted further, ClientHello and
-    %%       HelloVerifyRequest have to have message_seq = 0, ServerHello
-    %%       can have a message_seq of 0 or 1
-    %%
-    {HsState0#dtls_hs_state{current_read_seq = MessageSeq + 1}, SeqNo, Body};
-
-reassemble_dtls_fragment(_SeqNo, _Type, Length, _MessageSeq, _, Length,
-			 _Body, HsState = #dtls_hs_state{current_read_seq = undefined}) ->
-    %% not what we expected, drop it
-    HsState;
-
-reassemble_dtls_fragment(SeqNo, _Type, Length, MessageSeq, 0, Length,
- 			 Body, HsState0 =
- 			     #dtls_hs_state{starting_read_seq = StartingReadSeq})
-  when MessageSeq < StartingReadSeq ->
-    %% this has to be the start of a new flight, let it through
-    %%
-    %% Note: this could (should?) be restricted further, the first message of a
-    %%       new flight has to have message_seq = 0
-    %%
-    HsState = dtls_hs_state_process_seq(HsState0),
-    {HsState, SeqNo, Body};
-
-reassemble_dtls_fragment(_SeqNo, _Type, Length, MessageSeq, 0, Length,
- 			 _Body, HsState = #dtls_hs_state{current_read_seq = CurrentReadSeq})
-  when MessageSeq < CurrentReadSeq ->
-    HsState;
-
-reassemble_dtls_fragment(SeqNo, _Type, Length, MessageSeq, 0, Length,
- 			 Body, HsState0 = #dtls_hs_state{current_read_seq = MessageSeq}) ->
-    %% Message fully contained and it's the current seq
-    HsState1 = dtls_hs_state_process_seq(HsState0),
-    {HsState1, SeqNo, Body};
-
-reassemble_dtls_fragment(SeqNo, Type, Length, MessageSeq, 0, Length,
- 			 Body, HsState) ->
-    %% Message fully contained and it's the NOT the current seq -> buffer
-    Fragment = {SeqNo, Type, Length, MessageSeq,
- 		dtls_fragment_init(Length, 0, Length, Body)},
-    dtls_hs_state_add_fragment(MessageSeq, Fragment, HsState);
-
-reassemble_dtls_fragment(_SeqNo, _Type, Length, MessageSeq, FragmentOffset, FragmentLength,
- 			 _Body,
- 			 HsState = #dtls_hs_state{current_read_seq = CurrentReadSeq})
-  when FragmentOffset + FragmentLength == Length andalso MessageSeq == (CurrentReadSeq - 1) ->
-    {retransmit, HsState};
-
-reassemble_dtls_fragment(_SeqNo, _Type, _Length, MessageSeq, _FragmentOffset, _FragmentLength,
- 			 _Body,
- 			 HsState = #dtls_hs_state{current_read_seq = CurrentReadSeq})
-  when MessageSeq < CurrentReadSeq ->
-    HsState;
-
-reassemble_dtls_fragment(SeqNo, Type, Length, MessageSeq,
- 			 FragmentOffset, FragmentLength,
- 			 Body,
- 			 HsState = #dtls_hs_state{fragments = Fragments0}) ->
-    case gb_trees:lookup(MessageSeq, Fragments0) of
- 	{value, Fragment} ->
- 	    dtls_fragment_reassemble(SeqNo, Type, Length, MessageSeq,
- 				     FragmentOffset, FragmentLength,
- 				     Body, Fragment, HsState);
- 	none ->
- 	    dtls_fragment_start(SeqNo, Type, Length, MessageSeq,
- 				FragmentOffset, FragmentLength,
- 				Body, HsState)
-    end.
 
-dtls_fragment_start(SeqNo, Type, Length, MessageSeq,
-		    FragmentOffset, FragmentLength,
-		    Body, HsState = #dtls_hs_state{fragments = Fragments0}) ->
-    Fragment = {SeqNo, Type, Length, MessageSeq,
- 		dtls_fragment_init(Length, FragmentOffset, FragmentLength, Body)},
-     Fragments1 = gb_trees:insert(MessageSeq, Fragment, Fragments0),
-    HsState#dtls_hs_state{fragments = Fragments1}.
-
-dtls_fragment_reassemble(SeqNo, Type, Length, MessageSeq,
-			 FragmentOffset, FragmentLength,
- 			 Body,
- 			 {LastSeqNo, Type, Length, MessageSeq, FragBuffer0},
- 			 HsState = #dtls_hs_state{fragments = Fragments0}) ->
-    FragBuffer1 = dtls_fragment_add(FragBuffer0, FragmentOffset, FragmentLength, Body),
-    Fragment = {erlang:max(SeqNo, LastSeqNo), Type, Length, MessageSeq, FragBuffer1},
-    Fragments1 = gb_trees:enter(MessageSeq, Fragment, Fragments0),
-    HsState#dtls_hs_state{fragments = Fragments1};
-
-%% Type, Length or Seq mismatch, drop everything...
-%% Note: the RFC is not clear on how to handle this...
-dtls_fragment_reassemble(_SeqNo, _Type, _Length, MessageSeq,
- 			 _FragmentOffset, _FragmentLength, _Body, _Fragment,
- 			 HsState = #dtls_hs_state{fragments = Fragments0}) ->
-    Fragments1 = gb_trees:delete_any(MessageSeq, Fragments0),
-    HsState#dtls_hs_state{fragments = Fragments1}.
-
-dtls_fragment_add({Length, FragmentList0, Bin0}, FragmentOffset, FragmentLength, Body) ->
-    Bin1 = dtls_fragment_bin_add(FragmentOffset, FragmentLength, Body, Bin0),
-    FragmentList1 = add_fragment(FragmentList0, {FragmentOffset, FragmentLength}),
-    {Length, FragmentList1, Bin1}.
-
-dtls_fragment_init(Length, 0, Length, Body) ->
-    {Length, [{0, Length}], Body};
-dtls_fragment_init(Length, FragmentOffset, FragmentLength, Body) ->
-    Bin = dtls_fragment_bin_add(FragmentOffset, FragmentLength, Body, <<0:(Length*8)>>),
-    {Length, [{FragmentOffset, FragmentOffset + FragmentLength}], Bin}.
-
-dtls_fragment_bin_add(FragmentOffset, FragmentLength, Add, Buffer) ->
-    <<First:FragmentOffset/bytes, _:FragmentLength/bytes, Rest/binary>> = Buffer,
-    <<First/binary, Add/binary, Rest/binary>>.
-
-merge_fragment_list([], Fragment, Acc) ->
-    lists:reverse([Fragment|Acc]);
-
-merge_fragment_list([H = {_, HEnd}|Rest], Frag = {FStart, _}, Acc)
-  when FStart > HEnd ->
-    merge_fragment_list(Rest, Frag, [H|Acc]);
-
-merge_fragment_list(Rest = [{HStart, _HEnd}|_], Frag = {_FStart, FEnd}, Acc)
-  when FEnd < HStart ->
-    lists:reverse(Acc) ++ [Frag|Rest];
-
-merge_fragment_list([{HStart, HEnd}|Rest], _Frag = {FStart, FEnd}, Acc)
-   when
-      FStart =< HEnd orelse FEnd >= HStart ->
-    Start = erlang:min(HStart, FStart),
-    End = erlang:max(HEnd, FEnd),
-    NewFrag = {Start, End},
-    merge_fragment_list(Rest, NewFrag, Acc).
-
-add_fragment(List, {FragmentOffset, FragmentLength}) ->
-    merge_fragment_list(List, {FragmentOffset, FragmentOffset + FragmentLength}, []).
+%%%%%%%  Encodeing   %%%%%%%%%%%%%
 
 enc_handshake(#hello_verify_request{protocol_version = {Major, Minor},
  				       cookie = Cookie}, _Version) ->
-     CookieLength = byte_size(Cookie),
+    CookieLength = byte_size(Cookie),
     {?HELLO_VERIFY_REQUEST, <<?BYTE(Major), ?BYTE(Minor),
  			      ?BYTE(CookieLength),
- 			      Cookie/binary>>};
+ 			      Cookie:CookieLength/binary>>};
 
 enc_handshake(#hello_request{}, _Version) ->
     {?HELLO_REQUEST, <<>>};
@@ -459,38 +242,246 @@ enc_handshake(#client_hello{client_version = {Major, Minor},
 		      ?BYTE(CookieLength), Cookie/binary,
 		      ?UINT16(CsLength), BinCipherSuites/binary,
  		      ?BYTE(CmLength), BinCompMethods/binary, ExtensionsBin/binary>>};
+
+enc_handshake(#server_hello{} = HandshakeMsg, Version) ->
+    {Type, <<?BYTE(Major), ?BYTE(Minor), Rest/binary>>} = 
+	ssl_handshake:encode_handshake(HandshakeMsg, Version),
+    {DTLSMajor, DTLSMinor} = dtls_v1:corresponding_dtls_version({Major, Minor}),
+    {Type,  <<?BYTE(DTLSMajor), ?BYTE(DTLSMinor), Rest/binary>>};
+
 enc_handshake(HandshakeMsg, Version) ->
     ssl_handshake:encode_handshake(HandshakeMsg, Version).
 
-decode_handshake(_Version, ?CLIENT_HELLO, <<?BYTE(Major), ?BYTE(Minor), Random:32/binary,
+bin_fragments(Bin, Size) ->
+     bin_fragments(Bin, size(Bin), Size, 0, []).
+
+bin_fragments(Bin, BinSize,  FragSize, Offset, Fragments) ->
+    case (BinSize - Offset - FragSize)  > 0 of
+	true ->
+	    Frag = binary:part(Bin, {Offset, FragSize}),
+	    bin_fragments(Bin, BinSize, FragSize, Offset + FragSize, [{Frag, Offset} | Fragments]);
+	false ->
+	    Frag = binary:part(Bin, {Offset, BinSize-Offset}),
+	    lists:reverse([{Frag, Offset} | Fragments])
+    end.
+
+handshake_fragments(_, _, _, [], Acc) ->
+    lists:reverse(Acc);
+handshake_fragments(MsgType, Seq, Len, [{Bin, Offset} | Bins], Acc) ->
+    FragLen = size(Bin),
+    handshake_fragments(MsgType, Seq, Len, Bins, 
+      [<<?BYTE(MsgType), Len/binary, Seq/binary, ?UINT24(Offset),
+	 ?UINT24(FragLen), Bin/binary>> | Acc]).
+
+address_to_bin({A,B,C,D}, Port) ->
+    <<0:80,16#ffff:16,A,B,C,D,Port:16>>;
+address_to_bin({A,B,C,D,E,F,G,H}, Port) ->
+    <<A:16,B:16,C:16,D:16,E:16,F:16,G:16,H:16,Port:16>>.
+
+%%%%%%%  Decodeing   %%%%%%%%%%%%%
+
+handle_fragments(Version, FragmentData, Buffers0, Acc) ->
+    Fragments = decode_handshake_fragments(FragmentData),
+    do_handle_fragments(Version, Fragments, Buffers0, Acc).
+
+do_handle_fragments(_, [], Buffers, Acc) ->
+    {lists:reverse(Acc), Buffers};
+do_handle_fragments(Version, [Fragment | Fragments], Buffers0, Acc) ->
+    case reassemble(Version, Fragment, Buffers0) of
+	{more_data, _} = More when Acc == []->
+	    More;
+	{more_data, Buffers} when Fragments == [] ->
+	    {lists:reverse(Acc), Buffers};
+	{more_data, Buffers} ->
+	    do_handle_fragments(Version, Fragments, Buffers, Acc);
+	{HsPacket, Buffers} ->
+	    do_handle_fragments(Version, Fragments, Buffers, [HsPacket | Acc])
+    end.
+
+decode_handshake(Version, <<?BYTE(Type), Bin/binary>>) ->
+    decode_handshake(Version, Type, Bin).
+
+decode_handshake(_, ?HELLO_REQUEST, <<>>) ->
+    #hello_request{};
+decode_handshake(_Version, ?CLIENT_HELLO, <<?UINT24(_), ?UINT16(_),
+					    ?UINT24(_),  ?UINT24(_), 
+					    ?BYTE(Major), ?BYTE(Minor), Random:32/binary,
 					    ?BYTE(SID_length), Session_ID:SID_length/binary,
-					    ?BYTE(Cookie_length), Cookie:Cookie_length/binary,
+					    ?BYTE(CookieLength), Cookie:CookieLength/binary,
 					    ?UINT16(Cs_length), CipherSuites:Cs_length/binary,
 					    ?BYTE(Cm_length), Comp_methods:Cm_length/binary,
 					    Extensions/binary>>) ->
     
-    DecodedExtensions = ssl_handshake:decode_hello_extensions(Extensions),
-    
+    DecodedExtensions = ssl_handshake:decode_hello_extensions({client, Extensions}),
+
     #client_hello{
        client_version = {Major,Minor},
        random = Random,
-        session_id = Session_ID,
        cookie = Cookie,
+       session_id = Session_ID,
        cipher_suites = ssl_handshake:decode_suites('2_bytes', CipherSuites),
        compression_methods = Comp_methods,
        extensions = DecodedExtensions
-       };
+      };
+
+decode_handshake(_Version, ?HELLO_VERIFY_REQUEST, <<?UINT24(_), ?UINT16(_),
+						    ?UINT24(_),  ?UINT24(_),
+						    ?BYTE(Major), ?BYTE(Minor),
+						    ?BYTE(CookieLength),
+						    Cookie:CookieLength/binary>>) ->
+    #hello_verify_request{protocol_version = {Major, Minor},
+			  cookie = Cookie};
+
+decode_handshake(Version, Tag,  <<?UINT24(_), ?UINT16(_),
+				  ?UINT24(_),  ?UINT24(_), Msg/binary>>) -> 
+    %% DTLS specifics stripped
+    decode_tls_thandshake(Version, Tag, Msg).
+
+decode_tls_thandshake(Version, Tag, Msg) ->
+    TLSVersion = dtls_v1:corresponding_tls_version(Version),
+    ssl_handshake:decode_handshake(TLSVersion, Tag, Msg).
+
+decode_handshake_fragments(<<>>) ->
+    [<<>>];
+decode_handshake_fragments(<<?BYTE(Type), ?UINT24(Length),
+			     ?UINT16(MessageSeq),
+			     ?UINT24(FragmentOffset), ?UINT24(FragmentLength),
+			    Fragment:FragmentLength/binary, Rest/binary>>) ->
+    [#handshake_fragment{type = Type, 
+			length = Length,
+			message_seq = MessageSeq,
+			fragment_offset = FragmentOffset,
+			fragment_length = FragmentLength,
+			fragment = Fragment} | decode_handshake_fragments(Rest)].
+
+reassemble(Version,  #handshake_fragment{message_seq = Seq} = Fragment, 
+	   #protocol_buffers{dtls_handshake_next_seq = Seq,
+			     dtls_handshake_next_fragments = Fragments0,
+			     dtls_handshake_later_fragments = LaterFragments0} = 
+	       Buffers0)-> 
+    case reassemble_fragments(Fragment, Fragments0) of
+	{more_data, Fragments} ->
+	    {more_data,  Buffers0#protocol_buffers{dtls_handshake_next_fragments = Fragments}};
+	{raw, RawHandshake} ->
+	    Handshake = decode_handshake(Version, RawHandshake),
+	    {NextFragments, LaterFragments} = next_fragments(LaterFragments0),
+	    {{Handshake, RawHandshake}, Buffers0#protocol_buffers{dtls_handshake_next_seq = Seq + 1,
+						  dtls_handshake_next_fragments = NextFragments,
+						  dtls_handshake_later_fragments = LaterFragments}}
+    end;
+reassemble(_,  #handshake_fragment{message_seq = FragSeq} = Fragment, 
+	   #protocol_buffers{dtls_handshake_next_seq = Seq,
+			     dtls_handshake_later_fragments = LaterFragments} = Buffers0) when FragSeq > Seq-> 
+     {more_data,
+      Buffers0#protocol_buffers{dtls_handshake_later_fragments = [Fragment | LaterFragments]}};
+reassemble(_, _, Buffers) -> 
+    %% Disregard fragments FragSeq < Seq
+    {more_data, Buffers}.
+
+reassemble_fragments(Current, Fragments0) ->
+    [Frag1 | Frags] = lists:keysort(#handshake_fragment.fragment_offset, [Current | Fragments0]),
+    [Fragment | _] = Fragments = merge_fragment(Frag1, Frags),
+    case is_complete_handshake(Fragment) of
+	true ->
+	    {raw, handshake_bin(Fragment)};
+	false ->
+	    {more_data, Fragments}
+    end.
 
-decode_handshake(_Version, ?HELLO_VERIFY_REQUEST, <<?BYTE(Major), ?BYTE(Minor),
-						    ?BYTE(CookieLength), Cookie:CookieLength/binary>>) ->
+merge_fragment(Frag0, []) ->
+    [Frag0];
+merge_fragment(Frag0, [Frag1 | Rest]) ->
+    case merge_fragments(Frag0, Frag1) of
+	[_|_] = Frags ->
+	    Frags ++ Rest;
+	Frag ->
+	    merge_fragment(Frag, Rest)
+    end.
 
-    #hello_verify_request{
-       protocol_version = {Major,Minor},
-       cookie = Cookie};
-decode_handshake(Version, Tag, Msg) ->
-    ssl_handshake:decode_handshake(Version, Tag, Msg).
+is_complete_handshake(#handshake_fragment{length = Length, fragment_length = Length}) ->
+    true;
+is_complete_handshake(_) ->
+    false.
+
+next_fragments(LaterFragments) ->
+    case lists:keysort(#handshake_fragment.message_seq, LaterFragments) of
+	[] ->
+	    {[], []}; 
+	[#handshake_fragment{message_seq = Seq} | _] = Fragments ->
+	    split_frags(Fragments, Seq, [])
+    end.
 
-%% address_to_bin({A,B,C,D}, Port) ->
-%%     <<0:80,16#ffff:16,A,B,C,D,Port:16>>;
-%% address_to_bin({A,B,C,D,E,F,G,H}, Port) ->
-%%     <<A:16,B:16,C:16,D:16,E:16,F:16,G:16,H:16,Port:16>>.
+split_frags([#handshake_fragment{message_seq = Seq} = Frag | Rest], Seq, Acc) ->
+    split_frags(Rest, Seq, [Frag | Acc]);
+split_frags(Frags, _, Acc) ->
+    {lists:reverse(Acc), Frags}.
+
+
+%% Duplicate
+merge_fragments(#handshake_fragment{
+		   fragment_offset = PreviousOffSet, 
+		   fragment_length = PreviousLen,
+		   fragment = PreviousData
+		  } = Previous, 
+		#handshake_fragment{
+		   fragment_offset = PreviousOffSet,
+		   fragment_length = PreviousLen,
+		   fragment = PreviousData}) ->
+    Previous;
+
+%% Lager fragment save new data
+merge_fragments(#handshake_fragment{
+		   fragment_offset = PreviousOffSet, 
+		   fragment_length = PreviousLen,
+		   fragment = PreviousData
+		  } = Previous, 
+		#handshake_fragment{
+		   fragment_offset = PreviousOffSet,
+		   fragment_length = CurrentLen,
+		   fragment = CurrentData}) when CurrentLen > PreviousLen ->
+    NewLength = CurrentLen - PreviousLen,
+    <<_:PreviousLen/binary, NewData/binary>> = CurrentData, 
+    Previous#handshake_fragment{
+      fragment_length = PreviousLen + NewLength,
+      fragment = <<PreviousData/binary, NewData/binary>>
+     };
+
+%% Smaller fragment
+merge_fragments(#handshake_fragment{
+		   fragment_offset = PreviousOffSet, 
+		   fragment_length = PreviousLen
+		  } = Previous, 
+		#handshake_fragment{
+		   fragment_offset = PreviousOffSet,
+		   fragment_length = CurrentLen}) when CurrentLen < PreviousLen ->
+    Previous;
+%% Next fragment
+merge_fragments(#handshake_fragment{
+		   fragment_offset = PreviousOffSet, 
+		   fragment_length = PreviousLen,
+		   fragment = PreviousData
+		  } = Previous, 
+		#handshake_fragment{
+		   fragment_offset = CurrentOffSet,
+		   fragment_length = CurrentLen,
+		   fragment = CurrentData}) when PreviousOffSet + PreviousLen == CurrentOffSet->
+	    Previous#handshake_fragment{
+	      fragment_length =  PreviousLen + CurrentLen,
+	      fragment = <<PreviousData/binary, CurrentData/binary>>};
+%% No merge there is a gap
+merge_fragments(Previous, Current) ->
+    [Previous, Current].
+	    
+handshake_bin(#handshake_fragment{
+		 type = Type,
+		 length = Len, 
+		 message_seq = Seq,
+		 fragment_length = Len,
+		 fragment_offset = 0,
+		 fragment = Fragment}) ->	    
+    handshake_bin(Type, Len, Seq, Fragment).
+
+handshake_bin(Type, Length, Seq, FragmentData) -> 
+    <<?BYTE(Type), ?UINT24(Length),
+      ?UINT16(Seq), ?UINT24(0), ?UINT24(Length),
+      FragmentData:Length/binary>>.