aboutsummaryrefslogblamecommitdiffstats
path: root/lib/kernel/test/erl_distribution_wb_SUITE.erl
blob: fcddf0dd16243226c794c3c8c2f59c2b5d34fce4 (plain) (tree)
1
2
3
4
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


                   
                                                        















                                                                         
                                                    

                                        

                                                                    
 
                                                              




















































                                                                                        
                                         
 
         
                                                          



            





                         
                                     
           

                                    
           
 




                                                                      
                                  































































































































































































































































































































































































































































































































































































































                                                                              

                                                      


                                                          
                                                                       
%%
%% %CopyrightBegin%
%% 
%% Copyright Ericsson AB 1999-2011. All Rights Reserved.
%% 
%% The contents of this file are subject to the Erlang Public License,
%% Version 1.1, (the "License"); you may not use this file except in
%% compliance with the License. You should have received a copy of the
%% Erlang Public License along with this software. If not, it can be
%% retrieved online at http://www.erlang.org/.
%% 
%% Software distributed under the License is distributed on an "AS IS"
%% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
%% the License for the specific language governing rights and limitations
%% under the License.
%% 
%% %CopyrightEnd%
%%
-module(erl_distribution_wb_SUITE).

-include_lib("test_server/include/test_server.hrl").
-include_lib("kernel/include/inet.hrl").

-export([all/0, suite/0,groups/0,init_per_suite/1, end_per_suite/1, 
	 init_per_group/2,end_per_group/2]).

-export([init_per_testcase/2, end_per_testcase/2, whitebox/1, 
	 switch_options/1, missing_compulsory_dflags/1]).

%% 1)
%%
%% Connections are now always set up symetrically with respect to
%% publication. If connecting node doesn't send DFLAG_PUBLISHED
%% the other node wont send DFLAG_PUBLISHED. If the connecting
%% node send DFLAG_PUBLISHED but the other node doesn't send
%% DFLAG_PUBLISHED, the connecting node should consider its
%% DFLAG_PUBLISHED as dropped, i.e the connecting node wont be
%% published on the other node.

-define(to_port(Socket, Data),
	case inet_tcp:send(Socket, Data) of
	    {error, closed} ->
		self() ! {tcp_closed, Socket},
	        {error, closed};
	    R ->
	        R
        end).

-define(DFLAG_PUBLISHED,1).
-define(DFLAG_ATOM_CACHE,2).
-define(DFLAG_EXTENDED_REFERENCES,4).
-define(DFLAG_DIST_MONITOR,8).
-define(DFLAG_FUN_TAGS,16#10).
-define(DFLAG_DIST_MONITOR_NAME,16#20).
-define(DFLAG_HIDDEN_ATOM_CACHE,16#40).
-define(DFLAG_NEW_FUN_TAGS,16#80).
-define(DFLAG_EXTENDED_PIDS_PORTS,16#100).

%% From R9 and forward extended references is compulsory
%% From R10 and forward extended pids and ports are compulsory
-define(COMPULSORY_DFLAGS, (?DFLAG_EXTENDED_REFERENCES bor ?DFLAG_EXTENDED_PIDS_PORTS)).


-define(shutdown(X), exit(X)).
-define(int16(X), [((X) bsr 8) band 16#ff, (X) band 16#ff]).

-define(int32(X), 
	[((X) bsr 24) band 16#ff, ((X) bsr 16) band 16#ff,
	 ((X) bsr 8) band 16#ff, (X) band 16#ff]).

-define(i16(X1,X0),
        (?u16(X1,X0) - 
         (if (X1) > 127 -> 16#10000; true -> 0 end))).

-define(u16(X1,X0),
        (((X1) bsl 8) bor (X0))).

-define(u32(X3,X2,X1,X0),
        (((X3) bsl 24) bor ((X2) bsl 16) bor ((X1) bsl 8) bor (X0))).

suite() -> [{ct_hooks,[ts_install_cth]}].

all() -> 
    [whitebox, switch_options, missing_compulsory_dflags].

groups() -> 
    [].

init_per_suite(Config) ->
    Config.

end_per_suite(_Config) ->
    ok.

init_per_group(_GroupName, Config) ->
    Config.

end_per_group(_GroupName, Config) ->
    Config.


init_per_testcase(Func, Config) when is_atom(Func), is_list(Config) ->
    Dog=?t:timetrap(?t:minutes(1)),
    [{watchdog, Dog}|Config].

end_per_testcase(_Func, Config) ->
    Dog=?config(watchdog, Config),
    ?t:timetrap_cancel(Dog).

switch_options(doc) ->
    ["Tests switching of options for the tcp port, as this is done"
     " when the distribution port is to be shortcut into the emulator."
     " Maybe this should be in the inet test suite, but only the distribution"
     " does such horrible things..."];
switch_options(Config) when is_list(Config) ->
    ok = test_switch_active(),
    ok = test_switch_active_partial() ,
    ok = test_switch_active_and_packet(),    
    ok.
    

whitebox(doc) ->
    ["Whitebox testing of distribution handshakes. Tests both BC with R5 and "
     "the md5 version. Note that after R6B, this should be revised to "
     "remove BC code."];
whitebox(Config) when is_list(Config) ->
    ?line {ok, Node} = start_node(?MODULE,""),
    ?line Cookie = erlang:get_cookie(),
    ?line {_,Host} = split(node()),
    ?line ok = pending_up_md5(Node, join(ccc,Host), Cookie),
    ?line ok = simultaneous_md5(Node, join('A',Host), Cookie),
    ?line ok = simultaneous_md5(Node, join(zzzzzzzzzzzzzz,Host), Cookie),
    ?line stop_node(Node),
    ok.
    
%%
%% The actual tests
%%

%%
%% Switch tcp options test
%%

test_switch_active() ->
    ?line {Client, Server} = socket_pair(0, 4),
    ?line ok = write_packets_32(Client, 1, 5),
    receive after 2000 -> ok end,
    ?line ok = read_packets(Server, 1, 1),
    receive after 2000 -> ok end,
    ?line ok = read_packets(Server, 2, 2),
    ?line inet:setopts(Server, [{active, true}]),
    ?line ok = receive_packets(Server, 3, 5),
    close_pair({Client, Server}),
    ok.
    
test_switch_active_partial() ->
    ?line {Client, Server} = socket_pair(0, 4),
    ?line ok = write_packets_32(Client, 1, 2),
    ?line ok = gen_tcp:send(Client,[?int32(4), [0,0,0]]),
    receive after 2000 -> ok end,
    ?line ok = read_packets(Server, 1, 1),
    receive after 2000 -> ok end,
    ?line ok = read_packets(Server, 2, 2),
    ?line inet:setopts(Server, [{active, true}]),
    ?line ok = gen_tcp:send(Client,[3]),
    ?line ok = write_packets_32(Client, 4, 5),
    ?line ok = receive_packets(Server, 3, 5),
    close_pair({Client, Server}),
    ok.
    
do_test_switch_active_and_packet(SendBefore, SendAfter) ->
    ?line {Client, Server} = socket_pair(0, 2),
    ?line ok = write_packets_16(Client, 1, 2),
    ?line ok = gen_tcp:send(Client,SendBefore),
    receive after 2000 -> ok end,
    ?line ok = read_packets(Server, 1, 1),
    receive after 2000 -> ok end,
    ?line ok = read_packets(Server, 2, 2),
    ?line inet:setopts(Server, [{packet,4}, {active, true}]),
    ?line ok = gen_tcp:send(Client,SendAfter),
    ?line ok = write_packets_32(Client, 4, 5),
    ?line ok = receive_packets(Server, 3, 5),
    close_pair({Client, Server}),
    ok.

test_switch_active_and_packet() ->
    ?line ok = do_test_switch_active_and_packet([0],[0,0,4,0,0,0,3]),
    ?line ok = do_test_switch_active_and_packet([0,0],[0,4,0,0,0,3]),
    ?line ok = do_test_switch_active_and_packet([0,0,0],[4,0,0,0,3]),
    ?line ok = do_test_switch_active_and_packet([0,0,0,4],[0,0,0,3]),
    ?line ok = do_test_switch_active_and_packet([0,0,0,4,0],[0,0,3]),
    ?line ok = do_test_switch_active_and_packet([0,0,0,4,0,0],[0,3]),
    ?line ok = do_test_switch_active_and_packet([0,0,0,4,0,0,0],[3]),
    ?line ok = do_test_switch_active_and_packet([0,0,0,4,0,0,0,3],[]),
    ok.


%%
%% Handshake tests
%%
pending_up_md5(Node,OurName,Cookie) ->
    ?line {NA,NB} = split(Node),
    ?line {port,PortNo,_} = erl_epmd:port_please(NA,NB),
    ?line {ok, SocketA} = gen_tcp:connect(atom_to_list(NB),PortNo,
					  [{active,false},
					   {packet,2}]),
    ?line send_name(SocketA,OurName,5),
    ?line ok = recv_status(SocketA),
    ?line {hidden,Node,5,HisChallengeA} = recv_challenge(SocketA), % See 1)
    ?line OurChallengeA = gen_challenge(),
    ?line OurDigestA = gen_digest(HisChallengeA, Cookie),
    ?line send_challenge_reply(SocketA, OurChallengeA, OurDigestA),
    ?line ok = recv_challenge_ack(SocketA, OurChallengeA, Cookie),
    %%%
    %%% OK, one connection is up, now lets be nasty and try another up:
    %%%
    %%% But wait for a while, the other node might not have done setnode 
    %%% just yet...
    ?line receive after 1000 -> ok end,
    ?line {ok, SocketB} = gen_tcp:connect(atom_to_list(NB),PortNo,
					  [{active,false},
					   {packet,2}]),
    ?line send_name(SocketB,OurName,5),
    ?line alive = recv_status(SocketB),
    ?line send_status(SocketB, true),
    ?line gen_tcp:close(SocketA),
    ?line {hidden,Node,5,HisChallengeB} = recv_challenge(SocketB), % See 1)
    ?line OurChallengeB = gen_challenge(),
    ?line OurDigestB = gen_digest(HisChallengeB, Cookie),
    ?line send_challenge_reply(SocketB, OurChallengeB, OurDigestB),
    ?line ok = recv_challenge_ack(SocketB, OurChallengeB, Cookie),
    %%%
    %%% Well, are we happy?
    %%%
    
    ?line inet:setopts(SocketB, [{active, false},
				 {packet, 4}]),    
    ?line gen_tcp:send(SocketB,build_rex_message('',OurName)),
    ?line {Header, Message} = recv_message(SocketB),
    ?line io:format("Received header ~p, data ~p.~n",
	      [Header, Message]),
    ?line gen_tcp:close(SocketB),
    ok.

simultaneous_md5(Node, OurName, Cookie) when OurName < Node ->
    ?line pong = net_adm:ping(Node),
    ?line LSocket = case gen_tcp:listen(0, [{active, false}, {packet,2}]) of
		  {ok, Socket} ->
		      Socket;
		  Else ->
		      exit(Else)
	      end,
    ?line EpmdSocket = register(OurName, LSocket, 1, 5),
    ?line {NA, NB} = split(Node),
    ?line rpc:cast(Node, net_adm, ping, [OurName]),
    ?line receive after 1000 -> ok end,
    ?line {port, PortNo, _} = erl_epmd:port_please(NA,NB),
    ?line {ok, SocketA} = gen_tcp:connect(atom_to_list(NB),PortNo,
					  [{active,false},
					   {packet,2}]),
    ?line send_name(SocketA,OurName,5),
    %% We are still not marked up on the other side, as our first message 
    %% is not sent.
    ?line SocketB = case gen_tcp:accept(LSocket) of
		  {ok, Socket1} ->
		      ?line Socket1;
		  Else2 ->
		      ?line exit(Else2)
	      end,
    ?line nok = recv_status(SocketA),
    % Now we are expected to close A
    ?line gen_tcp:close(SocketA),
    % But still Socket B will continue
    ?line {normal,Node,5} = recv_name(SocketB),  % See 1)
    ?line send_status(SocketB, ok_simultaneous),
    ?line MyChallengeB = gen_challenge(),
    ?line send_challenge(SocketB, OurName, MyChallengeB,5),
    ?line HisChallengeB = recv_challenge_reply(SocketB, MyChallengeB, Cookie),
    ?line DigestB = gen_digest(HisChallengeB,Cookie),
    ?line send_challenge_ack(SocketB, DigestB),
    ?line inet:setopts(SocketB, [{active, false},
			  {packet, 4}]),    
    % This should be the ping message.
    ?line {Header, Message} = recv_message(SocketB),
    ?line io:format("Received header ~p, data ~p.~n",
	      [Header, Message]),
    ?line gen_tcp:close(SocketB),
    ?line gen_tcp:close(LSocket),
    ?line gen_tcp:close(EpmdSocket),
    ok;
    
simultaneous_md5(Node, OurName, Cookie) when OurName > Node ->
    ?line pong = net_adm:ping(Node),
    ?line LSocket = case gen_tcp:listen(0, [{active, false}, {packet,2}]) of
			{ok, Socket} ->
			    ?line Socket;
			Else ->
			    ?line exit(Else)
		    end,
    ?line EpmdSocket = register(OurName, LSocket, 1, 5),
    ?line {NA, NB} = split(Node),
    ?line rpc:cast(Node, net_adm, ping, [OurName]),
    ?line receive after 1000 -> ok end,
    ?line {port, PortNo, _} = erl_epmd:port_please(NA,NB),
    ?line {ok, SocketA} = gen_tcp:connect(atom_to_list(NB),PortNo,
					  [{active,false},
					   {packet,2}]),
    ?line SocketB = case gen_tcp:accept(LSocket) of
		  {ok, Socket1} ->
		      ?line Socket1;
		  Else2 ->
		      ?line exit(Else2)
	      end,
    ?line send_name(SocketA,OurName,5),
    ?line ok_simultaneous = recv_status(SocketA),
    %% Socket B should die during this
    ?line case catch begin
			 ?line {normal,Node,5} = recv_name(SocketB),  % See 1)
			 ?line send_status(SocketB, ok_simultaneous),
			 ?line MyChallengeB = gen_challenge(),
			 ?line send_challenge(SocketB, OurName, MyChallengeB,
					      5),
			 ?line HisChallengeB = recv_challenge_reply(
						 SocketB, 
						 MyChallengeB, 
						 Cookie),
			 ?line DigestB = gen_digest(HisChallengeB,Cookie),
			 ?line send_challenge_ack(SocketB, DigestB),
			 ?line inet:setopts(SocketB, [{active, false},
						      {packet, 4}]),    
			 ?line {HeaderB, MessageB} = recv_message(SocketB),
			 ?line io:format("Received header ~p, data ~p.~n",
					 [HeaderB, MessageB])
		     end of
	      {'EXIT', Exitcode} ->
		  ?line io:format("Expected exitsignal caught: ~p.~n",
				  [Exitcode]);
	      Success ->
		  ?line io:format("Unexpected success: ~p~n",
				  [Success]),
		  ?line exit(unexpected_success)
	  end,
    ?line gen_tcp:close(SocketB),
    %% But still Socket A will continue
    ?line {hidden,Node,5,HisChallengeA} = recv_challenge(SocketA), % See 1)
    ?line OurChallengeA = gen_challenge(),
    ?line OurDigestA = gen_digest(HisChallengeA, Cookie),
    ?line send_challenge_reply(SocketA, OurChallengeA, OurDigestA),
    ?line ok = recv_challenge_ack(SocketA, OurChallengeA, Cookie),
    
    ?line inet:setopts(SocketA, [{active, false},
				 {packet, 4}]),    
    ?line gen_tcp:send(SocketA,build_rex_message('',OurName)),
    ?line {Header, Message} = recv_message(SocketA),
    ?line io:format("Received header ~p, data ~p.~n",
	      [Header, Message]),
    ?line gen_tcp:close(SocketA),
    ?line gen_tcp:close(LSocket),
    ?line gen_tcp:close(EpmdSocket),
    ok.

missing_compulsory_dflags(doc) -> [];
missing_compulsory_dflags(Config) when is_list(Config) ->
    ?line [Name1, Name2] = get_nodenames(2, missing_compulsory_dflags),
    ?line {ok, Node} = start_node(Name1,""),
    ?line {NA,NB} = split(Node),
    ?line {port,PortNo,_} = erl_epmd:port_please(NA,NB),
    ?line {ok, SocketA} = gen_tcp:connect(atom_to_list(NB),PortNo,
					  [{active,false},
					   {packet,2}]),
    ?line BadNode = list_to_atom(atom_to_list(Name2)++"@"++atom_to_list(NB)),
    ?line send_name(SocketA,BadNode,5,0),
    ?line not_allowed = recv_status(SocketA),
    ?line gen_tcp:close(SocketA),
    ?line stop_node(Node),
    ?line ok.

%%
%% Here comes the utilities
%%

%%
%% Switch option utilities
%%
write_packets_32(_, M, N) when M > N ->
    ok;
write_packets_32(Sock, M, N) ->
    ok = gen_tcp:send(Sock,[?int32(4), ?int32(M)]),
    write_packets_32(Sock, M+1, N).

write_packets_16(_, M, N) when M > N ->
    ok;
write_packets_16(Sock, M, N) ->
    ok = gen_tcp:send(Sock,[?int16(4), ?int32(M)]),
    write_packets_16(Sock, M+1, N).

read_packets(_, M, N) when M > N ->
    ok;
read_packets(Sock, M, N) ->
    Expected = ?int32(M),
    case gen_tcp:recv(Sock, 0) of
	{ok, Expected} ->
	    read_packets(Sock, M+1, N);
	{ok, Unexpected} ->
	    exit({unexpected_data_read, Unexpected});
	Error ->
	    exit({error_read, Error})
    end.

receive_packets(Sock, M, N) when M > N ->
    receive
	{tcp, Sock, Data} ->
	    exit({extra_data, Data})
    after 0 ->
	    ok
    end;

receive_packets(Sock, M, N) ->
    Expect = ?int32(M),
    receive
	{tcp, Sock, Expect} ->
	    receive_packets(Sock, M+1, N); 
	{tcp, Sock, Unexpected} ->
	    exit({unexpected_data_received, Unexpected})
    after 500 ->
	    exit({no_data_received_for,M})
    end.

socket_pair(ClientPack, ServerPack) ->
    {ok, Listen} = gen_tcp:listen(0, [{active, false}, 
				      {packet, ServerPack}]),
    {ok, Host} = inet:gethostname(),
    {ok, Port} = inet:port(Listen),
    {ok, Client} = gen_tcp:connect(Host, Port, [{active, false}, 
						{packet, ClientPack}]),
    {ok, Server} = gen_tcp:accept(Listen),
    gen_tcp:close(Listen),
    {Client, Server}.
    
close_pair({Client, Server}) ->
    gen_tcp:close(Client),
    gen_tcp:close(Server),
    ok.


%%
%% Handshake utilities
%%

%%
%% MD5 hashing
%%

%% This is no proper random number, but that is not really important in 
%% this test
gen_challenge() ->
    {_,_,N} = erlang:now(), 
    N.
    
%% Generate a message digest from Challenge number and Cookie	
gen_digest(Challenge, Cookie) when is_integer(Challenge), is_atom(Cookie) ->
    C0 = erlang:md5_init(),
    C1 = erlang:md5_update(C0, atom_to_list(Cookie)),
    C2 = erlang:md5_update(C1, integer_to_list(Challenge)),
    binary_to_list(erlang:md5_final(C2)).


%%
%% The differrent stages of the MD5 handshake
%%

send_status(Socket, Stat) ->
    case gen_tcp:send(Socket, [$s | atom_to_list(Stat)]) of
	{error, _} ->
	    ?shutdown(could_not_send_status);
	_ -> 
	    true
    end.


recv_status(Socket) ->
    case gen_tcp:recv(Socket, 0) of
	{ok, [$s|StrStat]} ->
	    list_to_atom(StrStat);
	Bad ->
	    exit(Bad)
    end.

send_challenge(Socket, Node, Challenge, Version) ->
    send_challenge(Socket, Node, Challenge, Version, ?COMPULSORY_DFLAGS).
send_challenge(Socket, Node, Challenge, Version, Flags) ->
    {ok, {{_Ip1,_Ip2,_Ip3,_Ip4}, _}} = inet:sockname(Socket),
    ?to_port(Socket, [$n,?int16(Version),?int32(Flags),
		      ?int32(Challenge), atom_to_list(Node)]).

recv_challenge(Socket) ->
    case gen_tcp:recv(Socket, 0) of
	{ok,[$n,V1,V0,Fl1,Fl2,Fl3,Fl4,CA3,CA2,CA1,CA0 | Ns]} ->
	    Flags = ?u32(Fl1,Fl2,Fl3,Fl4),
	    Type = case Flags band ?DFLAG_PUBLISHED of
		       0 ->
			   hidden;
		       _ ->
			   normal
		   end,
	    Node =list_to_atom(Ns),
	    Version = ?u16(V1,V0),
	    Challenge = ?u32(CA3,CA2,CA1,CA0),
	    {Type,Node,Version,Challenge};
	_ ->
	    ?shutdown(no_node)	    
    end.

send_challenge_reply(Socket, Challenge, Digest) ->
    ?to_port(Socket, [$r,?int32(Challenge),Digest]).

recv_challenge_reply(Socket, ChallengeA, Cookie) ->
    case gen_tcp:recv(Socket, 0) of
	{ok,[$r,CB3,CB2,CB1,CB0 | SumB]} when length(SumB) == 16 ->
	    SumA = gen_digest(ChallengeA, Cookie),
	    ChallengeB = ?u32(CB3,CB2,CB1,CB0),
	    if SumB == SumA ->
		    ChallengeB;
	       true ->
		    ?shutdown(bad_challenge_reply)
	    end;
	_ ->
	    ?shutdown(no_node)
    end.

send_challenge_ack(Socket, Digest) ->
    ?to_port(Socket, [$a,Digest]).

recv_challenge_ack(Socket, ChallengeB, CookieA) ->
    case gen_tcp:recv(Socket, 0) of
	{ok,[$a | SumB]} when length(SumB) == 16 ->
	    SumA = gen_digest(ChallengeB, CookieA),
	    if SumB == SumA ->
		    ok;
	       true ->
		    ?shutdown(bad_challenge_ack)
	    end;
	_ ->
	    ?shutdown(bad_challenge_ack)
    end.

send_name(Socket, MyNode0, Version) ->
    send_name(Socket, MyNode0, Version, ?COMPULSORY_DFLAGS).
send_name(Socket, MyNode0, Version, Flags) ->
    MyNode = atom_to_list(MyNode0),
    ok = ?to_port(Socket, [<<$n,Version:16,Flags:32>>|MyNode]).

%%
%% recv_name is common for both old and new handshake.
%%
recv_name(Socket) ->
    case gen_tcp:recv(Socket, 0) of
	{ok,Data} ->
	    get_name(Data);
	Res ->
	    ?shutdown({no_node,Res})
    end.

get_name([$m,VersionA,VersionB,_Ip1,_Ip2,_Ip3,_Ip4|OtherNode]) ->
    {normal, list_to_atom(OtherNode), ?u16(VersionA,VersionB)};
get_name([$h,VersionA,VersionB,_Ip1,_Ip2,_Ip3,_Ip4|OtherNode]) ->
    {hidden, list_to_atom(OtherNode), ?u16(VersionA,VersionB)};
get_name([$n,VersionA, VersionB, Flag1, Flag2, Flag3, Flag4 | OtherNode]) ->
    Type = case ?u32(Flag1, Flag2, Flag3, Flag4) band ?DFLAG_PUBLISHED of
	       0 ->
		   hidden;
	       _ -> 
		   normal
	   end,
    {Type, list_to_atom(OtherNode), 
     ?u16(VersionA,VersionB)};
get_name(Data) ->
    ?shutdown(Data).

%%
%% The communication with EPMD follows
%%
get_epmd_port() ->
    case init:get_argument(epmd_port) of
        {ok, [[PortStr|_]|_]} when is_list(PortStr) ->
            list_to_integer(PortStr);
        error ->
            4369 % Default epmd port
    end.

do_register_node(NodeName, TcpPort, VLow, VHigh) ->    
    case gen_tcp:connect({127,0,0,1}, get_epmd_port(), []) of
	{ok, Socket} ->
	    {N0,_} = split(NodeName),
	    Name = atom_to_list(N0),
	    Extra = "",
	    Elen = length(Extra),
	    Len = 1+2+1+1+2+2+2+length(Name)+2+Elen,
	    gen_tcp:send(Socket, [?int16(Len), $x,
				   ?int16(TcpPort),
				   $M,
				   0,
				   ?int16(VHigh),
				   ?int16(VLow),
				   ?int16(length(Name)),
				   Name,
				   ?int16(Elen),
				   Extra]),
	    case wait_for_reg_reply(Socket, []) of
		{error, epmd_close} ->
		    exit(epmd_broken);
		Other ->
		    Other
	    end;
	Error ->
	    Error
    end.

wait_for_reg_reply(Socket, SoFar) ->
    receive
	{tcp, Socket, Data0} ->
	    case SoFar ++ Data0 of
		[$y, Result, A, B] ->
		    case Result of
			0 ->
			    {alive, Socket, ?u16(A, B)};
			_ ->
			    {error, duplicate_name}
		    end;
		Data when length(Data) < 4 ->
		    wait_for_reg_reply(Socket, Data);
		Garbage ->
		    {error, {garbage_from_epmd, Garbage}}
	    end;
	{tcp_closed, Socket} ->
	    {error, epmd_close}
    after 10000 ->
	    gen_tcp:close(Socket),
	    {error, no_reg_reply_from_epmd}
    end.


register(NodeName, ListenSocket, VLow, VHigh) ->
    {ok,{_,TcpPort}} = inet:sockname(ListenSocket),
    case do_register_node(NodeName, TcpPort, VLow, VHigh) of
	{alive, Socket, _Creation} ->
	    Socket;
	Other ->
	    exit(Other)
    end.


%%
%% Utilities
%%

%% Split a nodename
split([$@|T],A) ->
    {lists:reverse(A),T};
split([H|T],A) ->
    split(T,[H|A]).

split(Atom) ->
    {A,B} = split(atom_to_list(Atom),[]),
    {list_to_atom(A),list_to_atom(B)}.

%% Build a distribution message that will make rex answer
build_rex_message(Cookie,OurName) ->
    [$?,term_to_binary({6,self(),Cookie,rex}),
     term_to_binary({'$gen_cast',
		    {cast,
		     rpc,
		     cast,
		     [OurName, hello, world, []],
		     self()} })].

%% Receive a distribution message    
recv_message(Socket) ->
    case gen_tcp:recv(Socket, 0) of
	{ok,Data} ->
	    B0 = list_to_binary(Data),
	    {_,B1} = erlang:split_binary(B0,1),
	    Header = binary_to_term(B1),
	    Siz = byte_size(term_to_binary(Header)),
	    {_,B2} = erlang:split_binary(B1,Siz),
	    Message = case (catch binary_to_term(B2)) of
			  {'EXIT', _} ->
			      could_not_digest_message;
			  Other ->
			      Other
		      end,
	    {Header, Message};
	Res ->
	    exit({no_message,Res})
    end. 

%% Build a nodename
join(Name,Host) ->
    list_to_atom(atom_to_list(Name) ++ "@" ++ atom_to_list(Host)).

%% start/stop slave.
start_node(Name, Param) ->
    ?t:start_node(Name, slave, [{args, Param}]).

stop_node(Node) ->
    ?t:stop_node(Node).


get_nodenames(N, T) ->
    get_nodenames(N, T, []).

get_nodenames(0, _, Acc) ->
    Acc;
get_nodenames(N, T, Acc) ->
    U = erlang:unique_integer([positive]),
    get_nodenames(N-1, T, [list_to_atom(?MODULE_STRING
					++ "-"
					++ atom_to_list(T)
					++ "-"
					++ integer_to_list(U)) | Acc]).