aboutsummaryrefslogtreecommitdiffstats
path: root/src/cowboy_websocket.erl
blob: 95770867bb8d82be08a029aadbc25623afb6721d (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
%% Copyright (c) 2011-2014, Loïc Hoguin <[email protected]>
%%
%% Permission to use, copy, modify, and/or distribute this software for any
%% purpose with or without fee is hereby granted, provided that the above
%% copyright notice and this permission notice appear in all copies.
%%
%% THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
%% WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
%% MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
%% ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
%% WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
%% ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
%% OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.

%% Cowboy supports versions 7 through 17 of the Websocket drafts.
%% It also supports RFC6455, the proposed standard for Websocket.
-module(cowboy_websocket).
-behaviour(cowboy_sub_protocol).

-export([upgrade/4]).
-export([handler_loop/4]).

-type close_code() :: 1000..4999.
-export_type([close_code/0]).

-type frame() :: close | ping | pong
	| {text | binary | close | ping | pong, iodata()}
	| {close, close_code(), iodata()}.
-export_type([frame/0]).

-type opcode() :: 0 | 1 | 2 | 8 | 9 | 10.
-type mask_key() :: 0..16#ffffffff.
-type frag_state() :: undefined
	| {nofin, opcode(), binary()} | {fin, opcode(), binary()}.
-type rsv() :: << _:3 >>.
-type terminate_reason() :: {normal | error | remote, atom()}
	| {remote, close_code(), binary()}.

-record(state, {
	env :: cowboy_middleware:env(),
	socket = undefined :: inet:socket(),
	transport = undefined :: module(),
	handler :: module(),
	key = undefined :: undefined | binary(),
	timeout = infinity :: timeout(),
	timeout_ref = undefined :: undefined | reference(),
	messages = undefined :: undefined | {atom(), atom(), atom()},
	hibernate = false :: boolean(),
	frag_state = undefined :: frag_state(),
	utf8_state = <<>> :: binary(),
	deflate_frame = false :: boolean(),
	inflate_state :: undefined | port(),
	deflate_state :: undefined | port()
}).

-spec upgrade(Req, Env, module(), any())
	-> {ok, Req, Env}
	| {suspend, module(), atom(), [any()]}
	when Req::cowboy_req:req(), Env::cowboy_middleware:env().
upgrade(Req, Env, Handler, HandlerOpts) ->
	{_, Ref} = lists:keyfind(listener, 1, Env),
	ranch:remove_connection(Ref),
	[Socket, Transport] = cowboy_req:get([socket, transport], Req),
	State = #state{env=Env, socket=Socket, transport=Transport,
		handler=Handler},
	try websocket_upgrade(State, Req) of
		{ok, State2, Req2} ->
			handler_init(State2, Req2, HandlerOpts)
	catch _:_ ->
		receive
			{cowboy_req, resp_sent} -> ok
		after 0 ->
			_ = cowboy_req:reply(400, Req),
			exit(normal)
		end
	end.

-spec websocket_upgrade(#state{}, Req)
	-> {ok, #state{}, Req} when Req::cowboy_req:req().
websocket_upgrade(State, Req) ->
	{ok, ConnTokens, Req2}
		= cowboy_req:parse_header(<<"connection">>, Req),
	true = lists:member(<<"upgrade">>, ConnTokens),
	%% @todo Should probably send a 426 if the Upgrade header is missing.
	{ok, [<<"websocket">>], Req3}
		= cowboy_req:parse_header(<<"upgrade">>, Req2),
	{Version, Req4} = cowboy_req:header(<<"sec-websocket-version">>, Req3),
	IntVersion = list_to_integer(binary_to_list(Version)),
	true = (IntVersion =:= 7) orelse (IntVersion =:= 8)
		orelse (IntVersion =:= 13),
	{Key, Req5} = cowboy_req:header(<<"sec-websocket-key">>, Req4),
	false = Key =:= undefined,
	websocket_extensions(State#state{key=Key},
		cowboy_req:set_meta(websocket_version, IntVersion, Req5)).

-spec websocket_extensions(#state{}, Req)
	-> {ok, #state{}, Req} when Req::cowboy_req:req().
websocket_extensions(State, Req) ->
	case cowboy_req:parse_header(<<"sec-websocket-extensions">>, Req) of
		{ok, Extensions, Req2} when Extensions =/= undefined ->
			[Compress] = cowboy_req:get([resp_compress], Req),
			case lists:keyfind(<<"x-webkit-deflate-frame">>, 1, Extensions) of
				{<<"x-webkit-deflate-frame">>, []} when Compress =:= true ->
					Inflate = zlib:open(),
					Deflate = zlib:open(),
					% Since we are negotiating an unconstrained deflate-frame
					% then we must be willing to accept frames using the
					% maximum window size which is 2^15. The negative value
					% indicates that zlib headers are not used.
					ok = zlib:inflateInit(Inflate, -15),
					% Initialize the deflater with a window size of 2^15 bits and disable
					% the zlib headers.
					ok = zlib:deflateInit(Deflate, best_compression, deflated, -15, 8, default),
					{ok, State#state{
						deflate_frame = true,
						inflate_state = Inflate,
						deflate_state = Deflate
					}, cowboy_req:set_meta(websocket_compress, true, Req2)};
				_ ->
					{ok, State, cowboy_req:set_meta(websocket_compress, false, Req2)}
			end;
		_ ->
			{ok, State, cowboy_req:set_meta(websocket_compress, false, Req)}
	end.

-spec handler_init(#state{}, Req, any())
	-> {ok, Req, cowboy_middleware:env()} | {suspend, module(), atom(), [any()]}
	when Req::cowboy_req:req().
handler_init(State=#state{env=Env, transport=Transport,
		handler=Handler}, Req, HandlerOpts) ->
	try Handler:websocket_init(Transport:name(), Req, HandlerOpts) of
		{ok, Req2, HandlerState} ->
			websocket_handshake(State, Req2, HandlerState);
		{ok, Req2, HandlerState, hibernate} ->
			websocket_handshake(State#state{hibernate=true},
				Req2, HandlerState);
		{ok, Req2, HandlerState, Timeout} ->
			websocket_handshake(State#state{timeout=Timeout},
				Req2, HandlerState);
		{ok, Req2, HandlerState, Timeout, hibernate} ->
			websocket_handshake(State#state{timeout=Timeout,
				hibernate=true}, Req2, HandlerState);
		{shutdown, Req2} ->
			cowboy_req:ensure_response(Req2, 400),
			{ok, Req2, [{result, closed}|Env]}
	catch Class:Reason ->
		Stacktrace = erlang:get_stacktrace(),
		cowboy_req:maybe_reply(Stacktrace, Req),
		erlang:Class([
			{reason, Reason},
			{mfa, {Handler, websocket_init, 3}},
			{stacktrace, Stacktrace},
			{req, cowboy_req:to_list(Req)},
			{opts, HandlerOpts}
		])
	end.

-spec websocket_handshake(#state{}, Req, any())
	-> {ok, Req, cowboy_middleware:env()}
	| {suspend, module(), atom(), [any()]}
	when Req::cowboy_req:req().
websocket_handshake(State=#state{
			transport=Transport, key=Key, deflate_frame=DeflateFrame},
		Req, HandlerState) ->
	Challenge = base64:encode(crypto:hash(sha,
		<< Key/binary, "258EAFA5-E914-47DA-95CA-C5AB0DC85B11" >>)),
	Extensions = case DeflateFrame of
		false -> [];
		true -> [{<<"sec-websocket-extensions">>, <<"x-webkit-deflate-frame">>}]
	end,
	{ok, Req2} = cowboy_req:upgrade_reply(
		101,
		[{<<"upgrade">>, <<"websocket">>},
		 {<<"sec-websocket-accept">>, Challenge}|
		 Extensions],
		Req),
	%% Flush the resp_sent message before moving on.
	receive {cowboy_req, resp_sent} -> ok after 0 -> ok end,
	State2 = handler_loop_timeout(State),
	handler_before_loop(State2#state{key=undefined,
		messages=Transport:messages()}, Req2, HandlerState, <<>>).

-spec handler_before_loop(#state{}, Req, any(), binary())
	-> {ok, Req, cowboy_middleware:env()}
	| {suspend, module(), atom(), [any()]}
	when Req::cowboy_req:req().
handler_before_loop(State=#state{
			socket=Socket, transport=Transport, hibernate=true},
		Req, HandlerState, SoFar) ->
	Transport:setopts(Socket, [{active, once}]),
	{suspend, ?MODULE, handler_loop,
		[State#state{hibernate=false}, Req, HandlerState, SoFar]};
handler_before_loop(State=#state{socket=Socket, transport=Transport},
		Req, HandlerState, SoFar) ->
	Transport:setopts(Socket, [{active, once}]),
	handler_loop(State, Req, HandlerState, SoFar).

-spec handler_loop_timeout(#state{}) -> #state{}.
handler_loop_timeout(State=#state{timeout=infinity}) ->
	State#state{timeout_ref=undefined};
handler_loop_timeout(State=#state{timeout=Timeout, timeout_ref=PrevRef}) ->
	_ = case PrevRef of undefined -> ignore; PrevRef ->
		erlang:cancel_timer(PrevRef) end,
	TRef = erlang:start_timer(Timeout, self(), ?MODULE),
	State#state{timeout_ref=TRef}.

-spec handler_loop(#state{}, Req, any(), binary())
	-> {ok, Req, cowboy_middleware:env()}
	| {suspend, module(), atom(), [any()]}
	when Req::cowboy_req:req().
handler_loop(State=#state{socket=Socket, messages={OK, Closed, Error},
		timeout_ref=TRef}, Req, HandlerState, SoFar) ->
	receive
		{OK, Socket, Data} ->
			State2 = handler_loop_timeout(State),
			websocket_data(State2, Req, HandlerState,
				<< SoFar/binary, Data/binary >>);
		{Closed, Socket} ->
			handler_terminate(State, Req, HandlerState, {error, closed});
		{Error, Socket, Reason} ->
			handler_terminate(State, Req, HandlerState, {error, Reason});
		{timeout, TRef, ?MODULE} ->
			websocket_close(State, Req, HandlerState, {normal, timeout});
		{timeout, OlderTRef, ?MODULE} when is_reference(OlderTRef) ->
			handler_loop(State, Req, HandlerState, SoFar);
		Message ->
			handler_call(State, Req, HandlerState,
				SoFar, websocket_info, Message, fun handler_before_loop/4)
	end.

%% All frames passing through this function are considered valid,
%% with the only exception of text and close frames with a payload
%% which may still contain errors.
-spec websocket_data(#state{}, Req, any(), binary())
	-> {ok, Req, cowboy_middleware:env()}
	| {suspend, module(), atom(), [any()]}
	when Req::cowboy_req:req().
%% RSV bits MUST be 0 unless an extension is negotiated
%% that defines meanings for non-zero values.
websocket_data(State, Req, HandlerState, << _:1, Rsv:3, _/bits >>)
		when Rsv =/= 0, State#state.deflate_frame =:= false ->
	websocket_close(State, Req, HandlerState, {error, badframe});
%% Invalid opcode. Note that these opcodes may be used by extensions.
websocket_data(State, Req, HandlerState, << _:4, Opcode:4, _/bits >>)
		when Opcode > 2, Opcode =/= 8, Opcode =/= 9, Opcode =/= 10 ->
	websocket_close(State, Req, HandlerState, {error, badframe});
%% Control frames MUST NOT be fragmented.
websocket_data(State, Req, HandlerState, << 0:1, _:3, Opcode:4, _/bits >>)
		when Opcode >= 8 ->
	websocket_close(State, Req, HandlerState, {error, badframe});
%% A frame MUST NOT use the zero opcode unless fragmentation was initiated.
websocket_data(State=#state{frag_state=undefined}, Req, HandlerState,
		<< _:4, 0:4, _/bits >>) ->
	websocket_close(State, Req, HandlerState, {error, badframe});
%% Non-control opcode when expecting control message or next fragment.
websocket_data(State=#state{frag_state={nofin, _, _}}, Req, HandlerState,
		<< _:4, Opcode:4, _/bits >>)
		when Opcode =/= 0, Opcode < 8 ->
	websocket_close(State, Req, HandlerState, {error, badframe});
%% Close control frame length MUST be 0 or >= 2.
websocket_data(State, Req, HandlerState, << _:4, 8:4, _:1, 1:7, _/bits >>) ->
	websocket_close(State, Req, HandlerState, {error, badframe});
%% Close control frame with incomplete close code. Need more data.
websocket_data(State, Req, HandlerState,
		Data = << _:4, 8:4, 1:1, Len:7, _/bits >>)
		when Len > 1, byte_size(Data) < 8 ->
	handler_before_loop(State, Req, HandlerState, Data);
%% 7 bits payload length.
websocket_data(State, Req, HandlerState, << Fin:1, Rsv:3/bits, Opcode:4, 1:1,
		Len:7, MaskKey:32, Rest/bits >>)
		when Len < 126 ->
	websocket_data(State, Req, HandlerState,
		Opcode, Len, MaskKey, Rest, Rsv, Fin);
%% 16 bits payload length.
websocket_data(State, Req, HandlerState, << Fin:1, Rsv:3/bits, Opcode:4, 1:1,
		126:7, Len:16, MaskKey:32, Rest/bits >>)
		when Len > 125, Opcode < 8 ->
	websocket_data(State, Req, HandlerState,
		Opcode, Len, MaskKey, Rest, Rsv, Fin);
%% 63 bits payload length.
websocket_data(State, Req, HandlerState, << Fin:1, Rsv:3/bits, Opcode:4, 1:1,
		127:7, 0:1, Len:63, MaskKey:32, Rest/bits >>)
		when Len > 16#ffff, Opcode < 8 ->
	websocket_data(State, Req, HandlerState,
		Opcode, Len, MaskKey, Rest, Rsv, Fin);
%% When payload length is over 63 bits, the most significant bit MUST be 0.
websocket_data(State, Req, HandlerState, << _:8, 1:1, 127:7, 1:1, _:7, _/binary >>) ->
	websocket_close(State, Req, HandlerState, {error, badframe});
%% All frames sent from the client to the server are masked.
websocket_data(State, Req, HandlerState, << _:8, 0:1, _/bits >>) ->
	websocket_close(State, Req, HandlerState, {error, badframe});
%% For the next two clauses, it can be one of the following:
%%
%%  *  The minimal number of bytes MUST be used to encode the length
%%  *  All control frames MUST have a payload length of 125 bytes or less
websocket_data(State, Req, HandlerState, << _:9, 126:7, _:48, _/bits >>) ->
	websocket_close(State, Req, HandlerState, {error, badframe});
websocket_data(State, Req, HandlerState, << _:9, 127:7, _:96, _/bits >>) ->
	websocket_close(State, Req, HandlerState, {error, badframe});
%% Need more data.
websocket_data(State, Req, HandlerState, Data) ->
	handler_before_loop(State, Req, HandlerState, Data).

%% Initialize or update fragmentation state.
-spec websocket_data(#state{}, Req, any(),
	opcode(), non_neg_integer(), mask_key(), binary(), rsv(), 0 | 1)
	-> {ok, Req, cowboy_middleware:env()}
	| {suspend, module(), atom(), [any()]}
	when Req::cowboy_req:req().
%% The opcode is only included in the first frame fragment.
websocket_data(State=#state{frag_state=undefined}, Req, HandlerState,
		Opcode, Len, MaskKey, Data, Rsv, 0) ->
	websocket_payload(State#state{frag_state={nofin, Opcode, <<>>}},
		Req, HandlerState, 0, Len, MaskKey, <<>>, 0, Data, Rsv);
%% Subsequent frame fragments.
websocket_data(State=#state{frag_state={nofin, _, _}}, Req, HandlerState,
		0, Len, MaskKey, Data, Rsv, 0) ->
	websocket_payload(State, Req, HandlerState,
		0, Len, MaskKey, <<>>, 0, Data, Rsv);
%% Final frame fragment.
websocket_data(State=#state{frag_state={nofin, Opcode, SoFar}},
		Req, HandlerState, 0, Len, MaskKey, Data, Rsv, 1) ->
	websocket_payload(State#state{frag_state={fin, Opcode, SoFar}},
		Req, HandlerState, 0, Len, MaskKey, <<>>, 0, Data, Rsv);
%% Unfragmented frame.
websocket_data(State, Req, HandlerState, Opcode, Len, MaskKey, Data, Rsv, 1) ->
	websocket_payload(State, Req, HandlerState,
		Opcode, Len, MaskKey, <<>>, 0, Data, Rsv).

-spec websocket_payload(#state{}, Req, any(),
	opcode(), non_neg_integer(), mask_key(), binary(), non_neg_integer(),
	binary(), rsv())
	-> {ok, Req, cowboy_middleware:env()}
	| {suspend, module(), atom(), [any()]}
	when Req::cowboy_req:req().
%% Close control frames with a payload MUST contain a valid close code.
websocket_payload(State, Req, HandlerState,
		Opcode=8, Len, MaskKey, <<>>, 0,
		<< MaskedCode:2/binary, Rest/bits >>, Rsv) ->
	Unmasked = << Code:16 >> = websocket_unmask(MaskedCode, MaskKey, <<>>),
	if	Code < 1000; Code =:= 1004; Code =:= 1005; Code =:= 1006;
				(Code > 1011) and (Code < 3000); Code > 4999 ->
			websocket_close(State, Req, HandlerState, {error, badframe});
		true ->
			websocket_payload(State, Req, HandlerState,
				Opcode, Len - 2, MaskKey, Unmasked, byte_size(MaskedCode),
				Rest, Rsv)
	end;
%% Text frames and close control frames MUST have a payload that is valid UTF-8.
websocket_payload(State=#state{utf8_state=Incomplete},
		Req, HandlerState, Opcode, Len, MaskKey, Unmasked, UnmaskedLen,
		Data, Rsv)
		when (byte_size(Data) < Len) andalso ((Opcode =:= 1) orelse
			((Opcode =:= 8) andalso (Unmasked =/= <<>>))) ->
	Unmasked2 = websocket_unmask(Data,
		rotate_mask_key(MaskKey, UnmaskedLen), <<>>),
	{Unmasked3, State2} = websocket_inflate_frame(Unmasked2, Rsv, false, State),
	case is_utf8(<< Incomplete/binary, Unmasked3/binary >>) of
		false ->
			websocket_close(State2, Req, HandlerState, {error, badencoding});
		Utf8State ->
			websocket_payload_loop(State2#state{utf8_state=Utf8State},
				Req, HandlerState, Opcode, Len - byte_size(Data), MaskKey,
				<< Unmasked/binary, Unmasked3/binary >>,
				UnmaskedLen + byte_size(Data), Rsv)
	end;
websocket_payload(State=#state{utf8_state=Incomplete},
		Req, HandlerState, Opcode, Len, MaskKey, Unmasked, UnmaskedLen,
		Data, Rsv)
		when Opcode =:= 1; (Opcode =:= 8) and (Unmasked =/= <<>>) ->
	<< End:Len/binary, Rest/bits >> = Data,
	Unmasked2 = websocket_unmask(End,
		rotate_mask_key(MaskKey, UnmaskedLen), <<>>),
	{Unmasked3, State2} = websocket_inflate_frame(Unmasked2, Rsv, true, State),
	case is_utf8(<< Incomplete/binary, Unmasked3/binary >>) of
		<<>> ->
			websocket_dispatch(State2#state{utf8_state= <<>>},
				Req, HandlerState, Rest, Opcode,
				<< Unmasked/binary, Unmasked3/binary >>);
		_ ->
			websocket_close(State2, Req, HandlerState, {error, badencoding})
	end;
%% Fragmented text frames may cut payload in the middle of UTF-8 codepoints.
websocket_payload(State=#state{frag_state={_, 1, _}, utf8_state=Incomplete},
		Req, HandlerState, Opcode=0, Len, MaskKey, Unmasked, UnmaskedLen,
		Data, Rsv)
		when byte_size(Data) < Len ->
	Unmasked2 = websocket_unmask(Data,
		rotate_mask_key(MaskKey, UnmaskedLen), <<>>),
	{Unmasked3, State2} = websocket_inflate_frame(Unmasked2, Rsv, false, State),
	case is_utf8(<< Incomplete/binary, Unmasked3/binary >>) of
		false ->
			websocket_close(State2, Req, HandlerState, {error, badencoding});
		Utf8State ->
			websocket_payload_loop(State2#state{utf8_state=Utf8State},
				Req, HandlerState, Opcode, Len - byte_size(Data), MaskKey,
				<< Unmasked/binary, Unmasked3/binary >>,
				UnmaskedLen + byte_size(Data), Rsv)
	end;
websocket_payload(State=#state{frag_state={Fin, 1, _}, utf8_state=Incomplete},
		Req, HandlerState, Opcode=0, Len, MaskKey, Unmasked, UnmaskedLen,
		Data, Rsv) ->
	<< End:Len/binary, Rest/bits >> = Data,
	Unmasked2 = websocket_unmask(End,
		rotate_mask_key(MaskKey, UnmaskedLen), <<>>),
	{Unmasked3, State2} = websocket_inflate_frame(Unmasked2, Rsv, Fin =:= fin, State),
	case is_utf8(<< Incomplete/binary, Unmasked3/binary >>) of
		<<>> ->
			websocket_dispatch(State2#state{utf8_state= <<>>},
				Req, HandlerState, Rest, Opcode,
				<< Unmasked/binary, Unmasked3/binary >>);
		Utf8State when is_binary(Utf8State), Fin =:= nofin ->
			websocket_dispatch(State2#state{utf8_state=Utf8State},
				Req, HandlerState, Rest, Opcode,
				<< Unmasked/binary, Unmasked3/binary >>);
		_ ->
			websocket_close(State, Req, HandlerState, {error, badencoding})
	end;
%% Other frames have a binary payload.
websocket_payload(State, Req, HandlerState,
		Opcode, Len, MaskKey, Unmasked, UnmaskedLen, Data, Rsv)
		when byte_size(Data) < Len ->
	Unmasked2 = websocket_unmask(Data,
		rotate_mask_key(MaskKey, UnmaskedLen), <<>>),
	{Unmasked3, State2} = websocket_inflate_frame(Unmasked2, Rsv, false, State),
	websocket_payload_loop(State2, Req, HandlerState,
		Opcode, Len - byte_size(Data), MaskKey,
		<< Unmasked/binary, Unmasked3/binary >>, UnmaskedLen + byte_size(Data),
		Rsv);
websocket_payload(State, Req, HandlerState,
		Opcode, Len, MaskKey, Unmasked, UnmaskedLen, Data, Rsv) ->
	<< End:Len/binary, Rest/bits >> = Data,
	Unmasked2 = websocket_unmask(End,
		rotate_mask_key(MaskKey, UnmaskedLen), <<>>),
	{Unmasked3, State2} = websocket_inflate_frame(Unmasked2, Rsv, true, State),
	websocket_dispatch(State2, Req, HandlerState, Rest, Opcode,
		<< Unmasked/binary, Unmasked3/binary >>).

-spec websocket_inflate_frame(binary(), rsv(), boolean(), #state{}) ->
		{binary(), #state{}}.
websocket_inflate_frame(Data, << Rsv1:1, _:2 >>, _,
		#state{deflate_frame = DeflateFrame} = State)
		when DeflateFrame =:= false orelse Rsv1 =:= 0 ->
	{Data, State};
websocket_inflate_frame(Data, << 1:1, _:2 >>, false, State) ->
	Result = zlib:inflate(State#state.inflate_state, Data),
	{iolist_to_binary(Result), State};
websocket_inflate_frame(Data, << 1:1, _:2 >>, true, State) ->
	Result = zlib:inflate(State#state.inflate_state,
		<< Data/binary, 0:8, 0:8, 255:8, 255:8 >>),
	{iolist_to_binary(Result), State}.

-spec websocket_unmask(B, mask_key(), B) -> B when B::binary().
websocket_unmask(<<>>, _, Unmasked) ->
	Unmasked;
websocket_unmask(<< O:32, Rest/bits >>, MaskKey, Acc) ->
	T = O bxor MaskKey,
	websocket_unmask(Rest, MaskKey, << Acc/binary, T:32 >>);
websocket_unmask(<< O:24 >>, MaskKey, Acc) ->
	<< MaskKey2:24, _:8 >> = << MaskKey:32 >>,
	T = O bxor MaskKey2,
	<< Acc/binary, T:24 >>;
websocket_unmask(<< O:16 >>, MaskKey, Acc) ->
	<< MaskKey2:16, _:16 >> = << MaskKey:32 >>,
	T = O bxor MaskKey2,
	<< Acc/binary, T:16 >>;
websocket_unmask(<< O:8 >>, MaskKey, Acc) ->
	<< MaskKey2:8, _:24 >> = << MaskKey:32 >>,
	T = O bxor MaskKey2,
	<< Acc/binary, T:8 >>.

%% Because we unmask on the fly we need to continue from the right mask byte.
-spec rotate_mask_key(mask_key(), non_neg_integer()) -> mask_key().
rotate_mask_key(MaskKey, UnmaskedLen) ->
	Left = UnmaskedLen rem 4,
	Right = 4 - Left,
	(MaskKey bsl (Left * 8)) + (MaskKey bsr (Right * 8)).

%% Returns <<>> if the argument is valid UTF-8, false if not,
%% or the incomplete part of the argument if we need more data.
-spec is_utf8(binary()) -> false | binary().
is_utf8(Valid = <<>>) ->
	Valid;
is_utf8(<< _/utf8, Rest/binary >>) ->
	is_utf8(Rest);
%% 2 bytes. Codepages C0 and C1 are invalid; fail early.
is_utf8(<< 2#1100000:7, _/bits >>) ->
	false;
is_utf8(Incomplete = << 2#110:3, _:5 >>) ->
	Incomplete;
%% 3 bytes.
is_utf8(Incomplete = << 2#1110:4, _:4 >>) ->
	Incomplete;
is_utf8(Incomplete = << 2#1110:4, _:4, 2#10:2, _:6 >>) ->
	Incomplete;
%% 4 bytes. Codepage F4 may have invalid values greater than 0x10FFFF.
is_utf8(<< 2#11110100:8, 2#10:2, High:6, _/bits >>) when High >= 2#10000 ->
	false;
is_utf8(Incomplete = << 2#11110:5, _:3 >>) ->
	Incomplete;
is_utf8(Incomplete = << 2#11110:5, _:3, 2#10:2, _:6 >>) ->
	Incomplete;
is_utf8(Incomplete = << 2#11110:5, _:3, 2#10:2, _:6, 2#10:2, _:6 >>) ->
	Incomplete;
%% Invalid.
is_utf8(_) ->
	false.

-spec websocket_payload_loop(#state{}, Req, any(),
		opcode(), non_neg_integer(), mask_key(), binary(),
		non_neg_integer(), rsv())
	-> {ok, Req, cowboy_middleware:env()}
	| {suspend, module(), atom(), [any()]}
	when Req::cowboy_req:req().
websocket_payload_loop(State=#state{socket=Socket, transport=Transport,
		messages={OK, Closed, Error}, timeout_ref=TRef},
		Req, HandlerState, Opcode, Len, MaskKey, Unmasked, UnmaskedLen, Rsv) ->
	Transport:setopts(Socket, [{active, once}]),
	receive
		{OK, Socket, Data} ->
			State2 = handler_loop_timeout(State),
			websocket_payload(State2, Req, HandlerState,
				Opcode, Len, MaskKey, Unmasked, UnmaskedLen, Data, Rsv);
		{Closed, Socket} ->
			handler_terminate(State, Req, HandlerState, {error, closed});
		{Error, Socket, Reason} ->
			handler_terminate(State, Req, HandlerState, {error, Reason});
		{timeout, TRef, ?MODULE} ->
			websocket_close(State, Req, HandlerState, {normal, timeout});
		{timeout, OlderTRef, ?MODULE} when is_reference(OlderTRef) ->
			websocket_payload_loop(State, Req, HandlerState,
				Opcode, Len, MaskKey, Unmasked, UnmaskedLen, Rsv);
		Message ->
			handler_call(State, Req, HandlerState,
				<<>>, websocket_info, Message,
				fun (State2, Req2, HandlerState2, _) ->
					websocket_payload_loop(State2, Req2, HandlerState2,
						Opcode, Len, MaskKey, Unmasked, UnmaskedLen, Rsv)
				end)
	end.

-spec websocket_dispatch(#state{}, Req, any(), binary(), opcode(), binary())
	-> {ok, Req, cowboy_middleware:env()}
	| {suspend, module(), atom(), [any()]}
	when Req::cowboy_req:req().
%% Continuation frame.
websocket_dispatch(State=#state{frag_state={nofin, Opcode, SoFar}},
		Req, HandlerState, RemainingData, 0, Payload) ->
	websocket_data(State#state{frag_state={nofin, Opcode,
		<< SoFar/binary, Payload/binary >>}}, Req, HandlerState, RemainingData);
%% Last continuation frame.
websocket_dispatch(State=#state{frag_state={fin, Opcode, SoFar}},
		Req, HandlerState, RemainingData, 0, Payload) ->
	websocket_dispatch(State#state{frag_state=undefined}, Req, HandlerState,
		RemainingData, Opcode, << SoFar/binary, Payload/binary >>);
%% Text frame.
websocket_dispatch(State, Req, HandlerState, RemainingData, 1, Payload) ->
	handler_call(State, Req, HandlerState, RemainingData,
		websocket_handle, {text, Payload}, fun websocket_data/4);
%% Binary frame.
websocket_dispatch(State, Req, HandlerState, RemainingData, 2, Payload) ->
	handler_call(State, Req, HandlerState, RemainingData,
		websocket_handle, {binary, Payload}, fun websocket_data/4);
%% Close control frame.
websocket_dispatch(State, Req, HandlerState, _RemainingData, 8, <<>>) ->
	websocket_close(State, Req, HandlerState, {remote, closed});
websocket_dispatch(State, Req, HandlerState, _RemainingData, 8,
		<< Code:16, Payload/bits >>) ->
	websocket_close(State, Req, HandlerState, {remote, Code, Payload});
%% Ping control frame. Send a pong back and forward the ping to the handler.
websocket_dispatch(State=#state{socket=Socket, transport=Transport},
		Req, HandlerState, RemainingData, 9, Payload) ->
	Len = payload_length_to_binary(iolist_size(Payload)),
	Transport:send(Socket, << 1:1, 0:3, 10:4, 0:1, Len/bits, Payload/binary >>),
	handler_call(State, Req, HandlerState, RemainingData,
		websocket_handle, {ping, Payload}, fun websocket_data/4);
%% Pong control frame.
websocket_dispatch(State, Req, HandlerState, RemainingData, 10, Payload) ->
	handler_call(State, Req, HandlerState, RemainingData,
		websocket_handle, {pong, Payload}, fun websocket_data/4).

-spec handler_call(#state{}, Req, any(), binary(), atom(), any(), fun())
	-> {ok, Req, cowboy_middleware:env()}
	| {suspend, module(), atom(), [any()]}
	when Req::cowboy_req:req().
handler_call(State=#state{handler=Handler}, Req, HandlerState,
		RemainingData, Callback, Message, NextState) ->
	try Handler:Callback(Message, Req, HandlerState) of
		{ok, Req2, HandlerState2} ->
			NextState(State, Req2, HandlerState2, RemainingData);
		{ok, Req2, HandlerState2, hibernate} ->
			NextState(State#state{hibernate=true},
				Req2, HandlerState2, RemainingData);
		{reply, Payload, Req2, HandlerState2}
				when is_list(Payload) ->
			case websocket_send_many(Payload, State) of
				{ok, State2} ->
					NextState(State2, Req2, HandlerState2, RemainingData);
				{shutdown, State2} ->
					handler_terminate(State2, Req2, HandlerState2,
						{normal, shutdown});
				{{error, _} = Error, State2} ->
					handler_terminate(State2, Req2, HandlerState2, Error)
			end;
		{reply, Payload, Req2, HandlerState2, hibernate}
				when is_list(Payload) ->
			case websocket_send_many(Payload, State) of
				{ok, State2} ->
					NextState(State2#state{hibernate=true},
						Req2, HandlerState2, RemainingData);
				{shutdown, State2} ->
					handler_terminate(State2, Req2, HandlerState2,
						{normal, shutdown});
				{{error, _} = Error, State2} ->
					handler_terminate(State2, Req2, HandlerState2, Error)
			end;
		{reply, Payload, Req2, HandlerState2} ->
			case websocket_send(Payload, State) of
				{ok, State2} ->
					NextState(State2, Req2, HandlerState2, RemainingData);
				{shutdown, State2} ->
					handler_terminate(State2, Req2, HandlerState2,
						{normal, shutdown});
				{{error, _} = Error, State2} ->
					handler_terminate(State2, Req2, HandlerState2, Error)
			end;
		{reply, Payload, Req2, HandlerState2, hibernate} ->
			case websocket_send(Payload, State) of
				{ok, State2} ->
					NextState(State2#state{hibernate=true},
						Req2, HandlerState2, RemainingData);
				{shutdown, State2} ->
					handler_terminate(State2, Req2, HandlerState2,
						{normal, shutdown});
				{{error, _} = Error, State2} ->
					handler_terminate(State2, Req2, HandlerState2, Error)
			end;
		{shutdown, Req2, HandlerState2} ->
			websocket_close(State, Req2, HandlerState2, {normal, shutdown})
	catch Class:Reason ->
		_ = websocket_close(State, Req, HandlerState, {error, handler}),
		erlang:Class([
			{reason, Reason},
			{mfa, {Handler, Callback, 3}},
			{stacktrace, erlang:get_stacktrace()},
			{msg, Message},
			{req, cowboy_req:to_list(Req)},
			{state, HandlerState}
		])
	end.

websocket_opcode(text) -> 1;
websocket_opcode(binary) -> 2;
websocket_opcode(close) -> 8;
websocket_opcode(ping) -> 9;
websocket_opcode(pong) -> 10.

-spec websocket_deflate_frame(opcode(), binary(), #state{}) ->
	{binary(), rsv(), #state{}}.
websocket_deflate_frame(Opcode, Payload,
		State=#state{deflate_frame = DeflateFrame})
		when DeflateFrame =:= false orelse Opcode >= 8 ->
	{Payload, << 0:3 >>, State};
websocket_deflate_frame(_, Payload, State=#state{deflate_state = Deflate}) ->
	Deflated = iolist_to_binary(zlib:deflate(Deflate, Payload, sync)),
	DeflatedBodyLength = erlang:size(Deflated) - 4,
	Deflated1 = case Deflated of
		<< Body:DeflatedBodyLength/binary, 0:8, 0:8, 255:8, 255:8 >> -> Body;
		_ -> Deflated
	end,
	{Deflated1, << 1:1, 0:2 >>, State}.

-spec websocket_send(frame(), #state{})
-> {ok, #state{}} | {shutdown, #state{}} | {{error, atom()}, #state{}}.
websocket_send(Type, State=#state{socket=Socket, transport=Transport})
		when Type =:= close ->
	Opcode = websocket_opcode(Type),
	case Transport:send(Socket, << 1:1, 0:3, Opcode:4, 0:8 >>) of
		ok -> {shutdown, State};
		Error -> {Error, State}
	end;
websocket_send(Type, State=#state{socket=Socket, transport=Transport})
		when Type =:= ping; Type =:= pong ->
	Opcode = websocket_opcode(Type),
	{Transport:send(Socket, << 1:1, 0:3, Opcode:4, 0:8 >>), State};
websocket_send({close, Payload}, State) ->
	websocket_send({close, 1000, Payload}, State);
websocket_send({Type = close, StatusCode, Payload}, State=#state{
		socket=Socket, transport=Transport}) ->
	Opcode = websocket_opcode(Type),
	Len = 2 + iolist_size(Payload),
	%% Control packets must not be > 125 in length.
	true = Len =< 125,
	BinLen = payload_length_to_binary(Len),
	Transport:send(Socket,
		[<< 1:1, 0:3, Opcode:4, 0:1, BinLen/bits, StatusCode:16 >>, Payload]),
	{shutdown, State};
websocket_send({Type, Payload0}, State=#state{socket=Socket, transport=Transport}) ->
	Opcode = websocket_opcode(Type),
	{Payload, Rsv, State2} = websocket_deflate_frame(Opcode, iolist_to_binary(Payload0), State),
	Len = iolist_size(Payload),
	%% Control packets must not be > 125 in length.
	true = if Type =:= ping; Type =:= pong ->
			Len =< 125;
		true ->
			true
	end,
	BinLen = payload_length_to_binary(Len),
	{Transport:send(Socket,
		[<< 1:1, Rsv/bits, Opcode:4, 0:1, BinLen/bits >>, Payload]), State2}.

-spec websocket_send_many([frame()], #state{})
	-> {ok, #state{}} | {shutdown, #state{}} | {{error, atom()}, #state{}}.
websocket_send_many([], State) ->
	{ok, State};
websocket_send_many([Frame|Tail], State) ->
	case websocket_send(Frame, State) of
		{ok, State2} -> websocket_send_many(Tail, State2);
		{shutdown, State2} -> {shutdown, State2};
		{Error, State2} -> {Error, State2}
	end.

-spec websocket_close(#state{}, Req, any(), terminate_reason())
	-> {ok, Req, cowboy_middleware:env()}
	when Req::cowboy_req:req().
websocket_close(State=#state{socket=Socket, transport=Transport},
		Req, HandlerState, Reason) ->
	case Reason of
		{normal, _} ->
			Transport:send(Socket, << 1:1, 0:3, 8:4, 0:1, 2:7, 1000:16 >>);
		{error, badframe} ->
			Transport:send(Socket, << 1:1, 0:3, 8:4, 0:1, 2:7, 1002:16 >>);
		{error, badencoding} ->
			Transport:send(Socket, << 1:1, 0:3, 8:4, 0:1, 2:7, 1007:16 >>);
		{error, handler} ->
			Transport:send(Socket, << 1:1, 0:3, 8:4, 0:1, 2:7, 1011:16 >>);
		{remote, closed} ->
			Transport:send(Socket, << 1:1, 0:3, 8:4, 0:8 >>);
		{remote, Code, _} ->
			Transport:send(Socket, << 1:1, 0:3, 8:4, 0:1, 2:7, Code:16 >>)
	end,
	handler_terminate(State, Req, HandlerState, Reason).

-spec handler_terminate(#state{}, Req, any(), terminate_reason())
	-> {ok, Req, cowboy_middleware:env()}
	when Req::cowboy_req:req().
handler_terminate(#state{env=Env, handler=Handler},
		Req, HandlerState, TerminateReason) ->
	try
		Handler:websocket_terminate(TerminateReason, Req, HandlerState)
	catch Class:Reason ->
		erlang:Class([
			{reason, Reason},
			{mfa, {Handler, websocket_terminate, 3}},
			{stacktrace, erlang:get_stacktrace()},
			{req, cowboy_req:to_list(Req)},
			{state, HandlerState},
			{terminate_reason, TerminateReason}
		])
	end,
	{ok, Req, [{result, closed}|Env]}.

-spec payload_length_to_binary(0..16#7fffffffffffffff)
	-> << _:7 >> | << _:23 >> | << _:71 >>.
payload_length_to_binary(N) ->
	case N of
		N when N =< 125 -> << N:7 >>;
		N when N =< 16#ffff -> << 126:7, N:16 >>;
		N when N =< 16#7fffffffffffffff -> << 127:7, N:64 >>
	end.