%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2013-2015. All Rights Reserved.
%%
%% Licensed under the Apache License, Version 2.0 (the "License");
%% you may not use this file except in compliance with the License.
%% You may obtain a copy of the License at
%%
%% http://www.apache.org/licenses/LICENSE-2.0
%%
%% Unless required by applicable law or agreed to in writing, software
%% distributed under the License is distributed on an "AS IS" BASIS,
%% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
%% See the License for the specific language governing permissions and
%% limitations under the License.
%%
%% %CopyrightEnd%
%%
-module(dtls_connection).
%% Internal application API
-behaviour(gen_statem).
-include("dtls_connection.hrl").
-include("dtls_handshake.hrl").
-include("ssl_alert.hrl").
-include("dtls_record.hrl").
-include("ssl_cipher.hrl").
-include("ssl_api.hrl").
-include("ssl_internal.hrl").
-include("ssl_srp.hrl").
-include_lib("public_key/include/public_key.hrl").
%% Internal application API
%% Setup
-export([start_fsm/8, start_link/7, init/1]).
%% State transition handling
-export([next_record/1, next_event/3]).
%% Handshake handling
-export([%%renegotiate/2,
reinit_handshake_data/1,
send_handshake/2, queue_handshake/2, queue_change_cipher/2]).
%% Alert and close handling
-export([%%send_alert/2, handle_own_alert/4, handle_close_alert/3,
handle_normal_shutdown/3 %%, close/5
%%alert_user/6, alert_user/9
]).
%% Data handling
-export([%%write_application_data/3,
read_application_data/2,
passive_receive/2, next_record_if_active/1%,
%%handle_common_event/4,
%handle_packet/3
]).
%% gen_statem state functions
-export([init/3, error/3, downgrade/3, %% Initiation and take down states
hello/3, certify/3, cipher/3, abbreviated/3, %% Handshake states
connection/3]).
%% gen_statem callbacks
-export([callback_mode/0, terminate/3, code_change/4, format_status/2]).
%%====================================================================
%% Internal application API
%%====================================================================
start_fsm(Role, Host, Port, Socket, {#ssl_options{erl_dist = false},_, Tracker} = Opts,
User, {CbModule, _,_, _} = CbInfo,
Timeout) ->
try
{ok, Pid} = dtls_connection_sup:start_child([Role, Host, Port, Socket,
Opts, User, CbInfo]),
{ok, SslSocket} = ssl_connection:socket_control(?MODULE, Socket, Pid, CbModule, Tracker),
ok = ssl_connection:handshake(SslSocket, Timeout),
{ok, SslSocket}
catch
error:{badmatch, {error, _} = Error} ->
Error
end;
start_fsm(Role, Host, Port, Socket, {#ssl_options{erl_dist = true},_, Tracker} = Opts,
User, {CbModule, _,_, _} = CbInfo,
Timeout) ->
try
{ok, Pid} = dtls_connection_sup:start_child_dist([Role, Host, Port, Socket,
Opts, User, CbInfo]),
{ok, SslSocket} = ssl_connection:socket_control(?MODULE, Socket, Pid, CbModule, Tracker),
ok = ssl_connection:handshake(SslSocket, Timeout),
{ok, SslSocket}
catch
error:{badmatch, {error, _} = Error} ->
Error
end.
send_handshake(Handshake, State) ->
send_handshake_flight(queue_handshake(Handshake, State)).
queue_flight_buffer(Msg, #state{negotiated_version = Version,
connection_states = #connection_states{
current_write =
#connection_state{epoch = Epoch}},
flight_buffer = Flight} = State) ->
State#state{flight_buffer = Flight ++ [{Version, Epoch, Msg}]}.
queue_handshake(Handshake, #state{negotiated_version = Version,
tls_handshake_history = Hist0,
connection_states = ConnectionStates0} = State0) ->
{Frag, ConnectionStates, Hist} =
encode_handshake(Handshake, Version, ConnectionStates0, Hist0),
queue_flight_buffer(Frag, State0#state{connection_states = ConnectionStates,
tls_handshake_history = Hist}).
send_handshake_flight(#state{socket = Socket,
transport_cb = Transport,
flight_buffer = Flight,
connection_states = ConnectionStates0} = State0) ->
{Encoded, ConnectionStates} =
encode_handshake_flight(Flight, ConnectionStates0),
Transport:send(Socket, Encoded),
State0#state{flight_buffer = [], connection_states = ConnectionStates}.
queue_change_cipher(Msg, State) ->
queue_flight_buffer(Msg, State).
send_alert(Alert, #state{negotiated_version = Version,
socket = Socket,
transport_cb = Transport,
connection_states = ConnectionStates0} = State0) ->
{BinMsg, ConnectionStates} =
ssl_alert:encode(Alert, Version, ConnectionStates0),
Transport:send(Socket, BinMsg),
State0#state{connection_states = ConnectionStates}.
reinit_handshake_data(#state{protocol_buffers = Buffers} = State) ->
State#state{premaster_secret = undefined,
public_key_info = undefined,
tls_handshake_history = ssl_handshake:init_handshake_history(),
protocol_buffers =
Buffers#protocol_buffers{dtls_fragment_state =
dtls_handshake:dtls_handshake_new_flight(0)}}.
%%====================================================================
%% tls_connection_sup API
%%====================================================================
%%--------------------------------------------------------------------
-spec start_link(atom(), host(), inet:port_number(), port(), list(), pid(), tuple()) ->
{ok, pid()} | ignore | {error, reason()}.
%%
%% Description: Creates a gen_fsm process which calls Module:init/1 to
%% initialize. To ensure a synchronized start-up procedure, this function
%% does not return until Module:init/1 has returned.
%%--------------------------------------------------------------------
start_link(Role, Host, Port, Socket, Options, User, CbInfo) ->
{ok, proc_lib:spawn_link(?MODULE, init, [[Role, Host, Port, Socket, Options, User, CbInfo]])}.
init([Role, Host, Port, Socket, Options, User, CbInfo]) ->
process_flag(trap_exit, true),
State0 = initial_state(Role, Host, Port, Socket, Options, User, CbInfo),
try
State = ssl_connection:ssl_config(State0#state.ssl_options, Role, State0),
gen_statem:enter_loop(?MODULE, [], init, State)
catch
throw:Error ->
gen_statem:enter_loop(?MODULE, [], error, {Error,State0})
end.
callback_mode() ->
state_functions.
%%--------------------------------------------------------------------
%% State functionsconnection/2
%%--------------------------------------------------------------------
init({call, From}, {start, Timeout},
#state{host = Host, port = Port, role = client,
ssl_options = SslOpts,
session = #session{own_certificate = Cert} = Session0,
transport_cb = Transport, socket = Socket,
connection_states = ConnectionStates0,
renegotiation = {Renegotiation, _},
session_cache = Cache,
session_cache_cb = CacheCb
} = State0) ->
Timer = ssl_connection:start_or_recv_cancel_timer(Timeout, From),
Hello = dtls_handshake:client_hello(Host, Port, ConnectionStates0, SslOpts,
Cache, CacheCb, Renegotiation, Cert),
Version = Hello#client_hello.client_version,
HelloVersion = dtls_record:lowest_protocol_version(SslOpts#ssl_options.versions),
Handshake0 = ssl_handshake:init_handshake_history(),
{BinMsg, ConnectionStates, Handshake} =
encode_handshake(Hello, HelloVersion, ConnectionStates0, Handshake0),
Transport:send(Socket, BinMsg),
State1 = State0#state{connection_states = ConnectionStates,
negotiated_version = Version, %% Requested version
session =
Session0#session{session_id = Hello#client_hello.session_id},
tls_handshake_history = Handshake,
start_or_recv_from = From,
timer = Timer},
{Record, State} = next_record(State1),
next_event(hello, Record, State);
init(Type, Event, State) ->
ssl_connection:init(Type, Event, State, ?MODULE).
error({call, From}, {start, _Timeout}, {Error, State}) ->
{stop_and_reply, normal, {reply, From, {error, Error}}, State};
error({call, From}, Msg, State) ->
handle_call(Msg, From, error, State);
error(_, _, _) ->
{keep_state_and_data, [postpone]}.
%%--------------------------------------------------------------------
-spec hello(gen_statem:event_type(),
#hello_request{} | #client_hello{} | #server_hello{} | term(),
#state{}) ->
gen_statem:state_function_result().
%%--------------------------------------------------------------------
hello(internal, #client_hello{client_version = ClientVersion,
extensions = #hello_extensions{ec_point_formats = EcPointFormats,
elliptic_curves = EllipticCurves}} = Hello,
State = #state{connection_states = ConnectionStates0,
port = Port, session = #session{own_certificate = Cert} = Session0,
renegotiation = {Renegotiation, _},
session_cache = Cache,
session_cache_cb = CacheCb,
negotiated_protocol = CurrentProtocol,
key_algorithm = KeyExAlg,
ssl_options = SslOpts}) ->
case dtls_handshake:hello(Hello, SslOpts, {Port, Session0, Cache, CacheCb,
ConnectionStates0, Cert, KeyExAlg}, Renegotiation) of
#alert{} = Alert ->
handle_own_alert(Alert, ClientVersion, hello, State);
{Version, {Type, Session},
ConnectionStates, Protocol0, ServerHelloExt, HashSign} ->
Protocol = case Protocol0 of
undefined -> CurrentProtocol;
_ -> Protocol0
end,
ssl_connection:hello(internal, {common_client_hello, Type, ServerHelloExt},
State#state{connection_states = ConnectionStates,
negotiated_version = Version,
hashsign_algorithm = HashSign,
session = Session,
client_ecc = {EllipticCurves, EcPointFormats},
negotiated_protocol = Protocol}, ?MODULE)
end;
hello(internal, #server_hello{} = Hello,
#state{connection_states = ConnectionStates0,
negotiated_version = ReqVersion,
role = client,
renegotiation = {Renegotiation, _},
ssl_options = SslOptions} = State) ->
case dtls_handshake:hello(Hello, SslOptions, ConnectionStates0, Renegotiation) of
#alert{} = Alert ->
handle_own_alert(Alert, ReqVersion, hello, State);
{Version, NewId, ConnectionStates, ProtoExt, Protocol} ->
ssl_connection:handle_session(Hello,
Version, NewId, ConnectionStates, ProtoExt, Protocol, State)
end;
hello(info, Event, State) ->
handle_info(Event, hello, State);
hello(Type, Event, State) ->
ssl_connection:hello(Type, Event, State, ?MODULE).
abbreviated(info, Event, State) ->
handle_info(Event, abbreviated, State);
abbreviated(Type, Event, State) ->
ssl_connection:abbreviated(Type, Event, State, ?MODULE).
certify(info, Event, State) ->
handle_info(Event, certify, State);
certify(Type, Event, State) ->
ssl_connection:certify(Type, Event, State, ?MODULE).
cipher(info, Event, State) ->
handle_info(Event, cipher, State);
cipher(Type, Event, State) ->
ssl_connection:cipher(Type, Event, State, ?MODULE).
connection(info, Event, State) ->
handle_info(Event, connection, State);
connection(internal, #hello_request{}, #state{host = Host, port = Port,
session = #session{own_certificate = Cert} = Session0,
session_cache = Cache, session_cache_cb = CacheCb,
ssl_options = SslOpts,
connection_states = ConnectionStates0,
renegotiation = {Renegotiation, _}} = State0) ->
Hello = dtls_handshake:client_hello(Host, Port, ConnectionStates0, SslOpts,
Cache, CacheCb, Renegotiation, Cert),
State1 = send_handshake(Hello, State0),
{Record, State} =
next_record(
State1#state{session = Session0#session{session_id
= Hello#client_hello.session_id}}),
next_event(hello, Record, State);
connection(internal, #client_hello{} = Hello, #state{role = server, allow_renegotiate = true} = State) ->
%% Mitigate Computational DoS attack
%% http://www.educatedguesswork.org/2011/10/ssltls_and_computational_dos.html
%% http://www.thc.org/thc-ssl-dos/ Rather than disabling client
%% initiated renegotiation we will disallow many client initiated
%% renegotiations immediately after each other.
erlang:send_after(?WAIT_TO_ALLOW_RENEGOTIATION, self(), allow_renegotiate),
{next_state, hello, State#state{allow_renegotiate = false}, [{next_event, internal, Hello}]};
connection(internal, #client_hello{}, #state{role = server, allow_renegotiate = false} = State0) ->
Alert = ?ALERT_REC(?WARNING, ?NO_RENEGOTIATION),
State1 = send_alert(Alert, State0),
{Record, State} = ssl_connection:prepare_connection(State1, ?MODULE),
next_event(connection, Record, State);
connection(Type, Event, State) ->
ssl_connection:connection(Type, Event, State, ?MODULE).
downgrade(Type, Event, State) ->
ssl_connection:downgrade(Type, Event, State, ?MODULE).
%%--------------------------------------------------------------------
%% Description: This function is called by a gen_fsm when it receives any
%% other message than a synchronous or asynchronous event
%% (or a system message).
%%--------------------------------------------------------------------
%% raw data from socket, unpack records
handle_info({Protocol, _, Data}, StateName,
#state{data_tag = Protocol} = State0) ->
case next_tls_record(Data, State0) of
{Record, State} ->
next_event(StateName, Record, State);
#alert{} = Alert ->
handle_normal_shutdown(Alert, StateName, State0),
{stop, {shutdown, own_alert}}
end;
handle_info({CloseTag, Socket}, StateName,
#state{socket = Socket, close_tag = CloseTag,
negotiated_version = Version} = State) ->
%% Note that as of DTLS 1.2 (TLS 1.1),
%% failure to properly close a connection no longer requires that a
%% session not be resumed. This is a change from DTLS 1.0 to conform
%% with widespread implementation practice.
case Version of
{254, N} when N =< 253 ->
ok;
_ ->
%% As invalidate_sessions here causes performance issues,
%% we will conform to the widespread implementation
%% practice and go aginst the spec
%%invalidate_session(Role, Host, Port, Session)
ok
end,
handle_normal_shutdown(?ALERT_REC(?FATAL, ?CLOSE_NOTIFY), StateName, State),
{stop, {shutdown, transport_closed}};
handle_info(Msg, StateName, State) ->
ssl_connection:handle_info(Msg, StateName, State).
handle_call(Event, From, StateName, State) ->
ssl_connection:handle_call(Event, From, StateName, State, ?MODULE).
%%--------------------------------------------------------------------
%% Description:This function is called by a gen_fsm when it is about
%% to terminate. It should be the opposite of Module:init/1 and do any
%% necessary cleaning up. When it returns, the gen_fsm terminates with
%% Reason. The return value is ignored.
%%--------------------------------------------------------------------
terminate(Reason, StateName, State) ->
ssl_connection:terminate(Reason, StateName, State).
%%--------------------------------------------------------------------
%% code_change(OldVsn, StateName, State, Extra) -> {ok, StateName, NewState}
%% Description: Convert process state when code is changed
%%--------------------------------------------------------------------
code_change(_OldVsn, StateName, State, _Extra) ->
{ok, StateName, State}.
format_status(Type, Data) ->
ssl_connection:format_status(Type, Data).
%%--------------------------------------------------------------------
%%% Internal functions
%%--------------------------------------------------------------------
encode_handshake(Handshake, Version, ConnectionStates0, Hist0) ->
{Seq, ConnectionStates} = sequence(ConnectionStates0),
{EncHandshake, Frag} = dtls_handshake:encode_handshake(Handshake, Version, Seq),
Hist = ssl_handshake:update_handshake_history(Hist0, EncHandshake),
{Frag, ConnectionStates, Hist}.
encode_change_cipher(#change_cipher_spec{}, Version, ConnectionStates) ->
dtls_record:encode_change_cipher_spec(Version, ConnectionStates).
encode_handshake_flight(Flight, ConnectionStates) ->
MSS = 1400,
encode_handshake_records(Flight, ConnectionStates, MSS, init_pack_records()).
encode_handshake_records([], CS, _MSS, Recs) ->
{finish_pack_records(Recs), CS};
encode_handshake_records([{Version, _Epoch, Frag = #change_cipher_spec{}}|Tail], ConnectionStates0, MSS, Recs0) ->
{Encoded, ConnectionStates} =
encode_change_cipher(Frag, Version, ConnectionStates0),
Recs = append_pack_records([Encoded], MSS, Recs0),
encode_handshake_records(Tail, ConnectionStates, MSS, Recs);
encode_handshake_records([{Version, Epoch, {MsgType, MsgSeq, Bin}}|Tail], CS0, MSS, Recs0 = {Buf0, _}) ->
Space = MSS - iolist_size(Buf0),
Len = byte_size(Bin),
{Encoded, CS} =
encode_handshake_record(Version, Epoch, Space, MsgType, MsgSeq, Len, Bin, 0, MSS, [], CS0),
Recs = append_pack_records(Encoded, MSS, Recs0),
encode_handshake_records(Tail, CS, MSS, Recs).
%% TODO: move to dtls_handshake????
encode_handshake_record(_Version, _Epoch, _Space, _MsgType, _MsgSeq, _Len, <<>>, _Offset, _MRS, Encoded, CS)
when length(Encoded) > 0 ->
%% make sure we encode at least one segment (for empty messages like Server Hello Done
{lists:reverse(Encoded), CS};
encode_handshake_record(Version, Epoch, Space, MsgType, MsgSeq, Len, Bin,
Offset, MRS, Encoded0, CS0) ->
MaxFragmentLen = Space - 25,
case Bin of
<<BinFragment:MaxFragmentLen/bytes, Rest/binary>> ->
ok;
_ ->
BinFragment = Bin,
Rest = <<>>
end,
FragLength = byte_size(BinFragment),
Frag = [MsgType, ?uint24(Len), ?uint16(MsgSeq), ?uint24(Offset), ?uint24(FragLength), BinFragment],
%% TODO Real solution, now avoid dialyzer error {Encoded, CS} = ssl_record:encode_handshake({Epoch, Frag}, Version, CS0),
{Encoded, CS} = ssl_record:encode_handshake(Frag, Version, CS0),
encode_handshake_record(Version, Epoch, MRS, MsgType, MsgSeq, Len, Rest, Offset + FragLength, MRS, [Encoded|Encoded0], CS).
init_pack_records() ->
{[], []}.
append_pack_records([], MSS, Recs = {Buf0, Acc0}) ->
Remaining = MSS - iolist_size(Buf0),
if Remaining < 12 ->
{[], [lists:reverse(Buf0)|Acc0]};
true ->
Recs
end;
append_pack_records([Head|Tail], MSS, {Buf0, Acc0}) ->
TotLen = iolist_size(Buf0) + iolist_size(Head),
if TotLen > MSS ->
append_pack_records(Tail, MSS, {[Head], [lists:reverse(Buf0)|Acc0]});
true ->
append_pack_records(Tail, MSS, {[Head|Buf0], Acc0})
end.
finish_pack_records({[], Acc}) ->
lists:reverse(Acc);
finish_pack_records({Buf, Acc}) ->
lists:reverse([lists:reverse(Buf)|Acc]).
%% decode_alerts(Bin) ->
%% ssl_alert:decode(Bin).
initial_state(Role, Host, Port, Socket, {SSLOptions, SocketOptions}, User,
{CbModule, DataTag, CloseTag, ErrorTag}) ->
#ssl_options{beast_mitigation = BeastMitigation} = SSLOptions,
ConnectionStates = ssl_record:init_connection_states(Role, BeastMitigation),
SessionCacheCb = case application:get_env(ssl, session_cb) of
{ok, Cb} when is_atom(Cb) ->
Cb;
_ ->
ssl_session_cache
end,
Monitor = erlang:monitor(process, User),
#state{socket_options = SocketOptions,
%% We do not want to save the password in the state so that
%% could be written in the clear into error logs.
ssl_options = SSLOptions#ssl_options{password = undefined},
session = #session{is_resumable = new},
transport_cb = CbModule,
data_tag = DataTag,
close_tag = CloseTag,
error_tag = ErrorTag,
role = Role,
host = Host,
port = Port,
socket = Socket,
connection_states = ConnectionStates,
protocol_buffers = #protocol_buffers{},
user_application = {Monitor, User},
user_data_buffer = <<>>,
session_cache_cb = SessionCacheCb,
renegotiation = {false, first},
allow_renegotiate = SSLOptions#ssl_options.client_renegotiation,
start_or_recv_from = undefined,
protocol_cb = ?MODULE
}.
next_tls_record(Data, #state{protocol_buffers = #protocol_buffers{
dtls_record_buffer = Buf0,
dtls_cipher_texts = CT0} = Buffers} = State0) ->
case dtls_record:get_dtls_records(Data, Buf0) of
{Records, Buf1} ->
CT1 = CT0 ++ Records,
next_record(State0#state{protocol_buffers =
Buffers#protocol_buffers{dtls_record_buffer = Buf1,
dtls_cipher_texts = CT1}});
#alert{} = Alert ->
Alert
end.
next_record(#state{%%flight = #flight{state = finished},
protocol_buffers =
#protocol_buffers{dtls_packets = [], dtls_cipher_texts = [CT | Rest]}
= Buffers,
connection_states = ConnStates0} = State) ->
case dtls_record:decode_cipher_text(CT, ConnStates0) of
{Plain, ConnStates} ->
{Plain, State#state{protocol_buffers =
Buffers#protocol_buffers{dtls_cipher_texts = Rest},
connection_states = ConnStates}};
#alert{} = Alert ->
{Alert, State}
end;
next_record(#state{socket = Socket,
transport_cb = Transport} = State) -> %% when FlightState =/= finished
ssl_socket:setopts(Transport, Socket, [{active,once}]),
{no_record, State};
next_record(State) ->
{no_record, State}.
next_record_if_active(State =
#state{socket_options =
#socket_options{active = false}}) ->
{no_record ,State};
next_record_if_active(State) ->
next_record(State).
passive_receive(State0 = #state{user_data_buffer = Buffer}, StateName) ->
case Buffer of
<<>> ->
{Record, State} = next_record(State0),
next_event(StateName, Record, State);
_ ->
{Record, State} = read_application_data(<<>>, State0),
next_event(StateName, Record, State)
end.
next_event(StateName, Record, State) ->
next_event(StateName, Record, State, []).
next_event(connection = StateName, no_record, State0, Actions) ->
case next_record_if_active(State0) of
{no_record, State} ->
ssl_connection:hibernate_after(StateName, State, Actions);
{#ssl_tls{} = Record, State} ->
{next_state, StateName, State, [{next_event, internal, {dtls_record, Record}} | Actions]};
{#alert{} = Alert, State} ->
{next_state, StateName, State, [{next_event, internal, Alert} | Actions]}
end;
next_event(StateName, Record, State, Actions) ->
case Record of
no_record ->
{next_state, StateName, State, Actions};
#ssl_tls{} = Record ->
{next_state, StateName, State, [{next_event, internal, {dtls_record, Record}} | Actions]};
#alert{} = Alert ->
{next_state, StateName, State, [{next_event, internal, Alert} | Actions]}
end.
read_application_data(_,State) ->
{#ssl_tls{fragment = <<"place holder">>}, State}.
handle_own_alert(_,_,_, State) -> %% Place holder
{stop, {shutdown, own_alert}, State}.
handle_normal_shutdown(_, _, _State) -> %% Place holder
ok.
%% TODO This generates dialyzer warnings, has to be handled differently.
%% handle_packet(Address, Port, Packet) ->
%% try dtls_record:get_dtls_records(Packet, <<>>) of
%% %% expect client hello
%% {[#ssl_tls{type = ?HANDSHAKE, version = {254, _}} = Record], <<>>} ->
%% handle_dtls_client_hello(Address, Port, Record);
%% _Other ->
%% {error, not_dtls}
%% catch
%% _Class:_Error ->
%% {error, not_dtls}
%% end.
%% handle_dtls_client_hello(Address, Port,
%% #ssl_tls{epoch = Epoch, sequence_number = Seq,
%% version = Version} = Record) ->
%% {[{Hello, _}], _} =
%% dtls_handshake:get_dtls_handshake(Record,
%% dtls_handshake:dtls_handshake_new_flight(undefined)),
%% #client_hello{client_version = {Major, Minor},
%% random = Random,
%% session_id = SessionId,
%% cipher_suites = CipherSuites,
%% compression_methods = CompressionMethods} = Hello,
%% CookieData = [address_to_bin(Address, Port),
%% <<?BYTE(Major), ?BYTE(Minor)>>,
%% Random, SessionId, CipherSuites, CompressionMethods],
%% Cookie = crypto:hmac(sha, <<"secret">>, CookieData),
%% case Hello of
%% #client_hello{cookie = Cookie} ->
%% accept;
%% _ ->
%% %% generate HelloVerifyRequest
%% {RequestFragment, _} = dtls_handshake:encode_handshake(
%% dtls_handshake:hello_verify_request(Cookie),
%% Version, 0),
%% HelloVerifyRequest =
%% dtls_record:encode_tls_cipher_text(?HANDSHAKE, Version, Epoch, Seq, RequestFragment),
%% {reply, HelloVerifyRequest}
%% 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>>.
sequence(#connection_states{dtls_write_msg_seq = Seq} = CS) ->
{Seq, CS#connection_states{dtls_write_msg_seq = Seq + 1}}.
