aboutsummaryrefslogtreecommitdiffstats
path: root/lib/ssl/src/inet_tls_dist.erl
blob: d644cbe66ada0139f77067e6b538403d2ca55963 (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
%%
%% %CopyrightBegin%
%%
%% Copyright Ericsson AB 2011-2017. 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(inet_tls_dist).

-export([childspecs/0]).
-export([listen/1, accept/1, accept_connection/5,
	 setup/5, close/1, select/1, is_node_name/1]).

%% Generalized dist API
-export([gen_listen/2, gen_accept/2, gen_accept_connection/6,
	 gen_setup/6, gen_close/2, gen_select/2]).

-export([split_node/1, nodelay/0]).

-export([dbg/0]). % Debug

-include_lib("kernel/include/net_address.hrl").
-include_lib("kernel/include/dist.hrl").
-include_lib("kernel/include/dist_util.hrl").

-include("ssl_api.hrl").

%% -------------------------------------------------------------------------

childspecs() ->
    {ok, [{ssl_dist_sup,{ssl_dist_sup, start_link, []},
	   permanent, infinity, supervisor, [ssl_dist_sup]}]}.

select(Node) ->
    gen_select(inet_tcp, Node).

gen_select(Driver, Node) ->
    case split_node(Node) of
        false ->
            false;
        Host ->
	    case Driver:getaddr(Host) of
		{ok, _} -> true;
		_ -> false
	    end
    end.

%% -------------------------------------------------------------------------

is_node_name(Node) ->
    case split_node(Node) of
        false ->
            false;
        _Host ->
            true
    end.

%% -------------------------------------------------------------------------

hs_data_common(#sslsocket{pid = DistCtrl} = SslSocket) ->
    #hs_data{
       f_send =
           fun (Ctrl, Packet) when Ctrl == DistCtrl ->
                   f_send(SslSocket, Packet)
           end,
       f_recv =
           fun (Ctrl, Length, Timeout) when Ctrl == DistCtrl ->
                   f_recv(SslSocket, Length, Timeout)
           end,
       f_setopts_pre_nodeup =
           fun (Ctrl) when Ctrl == DistCtrl ->
                   f_setopts_pre_nodeup(SslSocket)
           end,
       f_setopts_post_nodeup =
           fun (Ctrl) when Ctrl == DistCtrl ->
%%%                   sys:trace(Ctrl, true),
                   f_setopts_post_nodeup(SslSocket)
           end,
       f_getll =
           fun (Ctrl) when Ctrl == DistCtrl ->
                   f_getll(DistCtrl)
           end,
       f_address =
           fun (Ctrl, Node) when Ctrl == DistCtrl ->
                   f_address(SslSocket, Node)
           end,
       mf_tick =
           fun (Ctrl) when Ctrl == DistCtrl ->
                   mf_tick(DistCtrl)
           end,
       mf_getstat =
           fun (Ctrl) when Ctrl == DistCtrl ->
                   mf_getstat(SslSocket)
           end,
       mf_setopts =
           fun (Ctrl, Opts) when Ctrl == DistCtrl ->
                   mf_setopts(SslSocket, Opts)
           end,
       mf_getopts =
           fun (Ctrl, Opts) when Ctrl == DistCtrl ->
                   mf_getopts(SslSocket, Opts)
           end,
       f_handshake_complete =
           fun (Ctrl, Node, DHandle) when Ctrl == DistCtrl ->
                   f_handshake_complete(DistCtrl, Node, DHandle)
           end}.

f_send(SslSocket, Packet) ->
    ssl:send(SslSocket, Packet).

f_recv(SslSocket, Length, Timeout) ->
    case ssl:recv(SslSocket, Length, Timeout) of
        {ok, Bin} when is_binary(Bin) ->
            {ok, binary_to_list(Bin)};
        Other ->
            Other
    end.

f_setopts_pre_nodeup(_SslSocket) ->
    ok.

f_setopts_post_nodeup(_SslSocket) ->
    ok.

f_getll(DistCtrl) ->
    {ok, DistCtrl}.

f_address(SslSocket, Node) ->
    case ssl:peername(SslSocket) of
        {ok, Address} ->
            case split_node(Node) of
                false ->
                    {error, no_node};
                Host ->
                    #net_address{
                       address=Address, host=Host,
                       protocol=tls, family=inet}
            end
    end.

mf_tick(DistCtrl) ->
    DistCtrl ! tick,
    ok.

mf_getstat(SslSocket) ->
    case ssl:getstat(
           SslSocket, [recv_cnt, send_cnt, send_pend]) of
        {ok, Stat} ->
            split_stat(Stat,0,0,0);
        Error ->
            Error
    end.

mf_setopts(SslSocket, Opts) ->
    case setopts_filter(Opts) of
        [] ->
            ssl:setopts(SslSocket, Opts);
        Opts1 ->
            {error, {badopts,Opts1}}
    end.

mf_getopts(SslSocket, Opts) ->
    ssl:getopts(SslSocket, Opts).

f_handshake_complete(DistCtrl, Node, DHandle) ->
    ssl_connection:handshake_complete(DistCtrl, Node, DHandle).


setopts_filter(Opts) ->
    [Opt || {K,_} = Opt <- Opts,
            K =:= active orelse K =:= deliver orelse K =:= packet].

split_stat([{recv_cnt, R}|Stat], _, W, P) ->
    split_stat(Stat, R, W, P);
split_stat([{send_cnt, W}|Stat], R, _, P) ->
    split_stat(Stat, R, W, P);
split_stat([{send_pend, P}|Stat], R, W, _) ->
    split_stat(Stat, R, W, P);
split_stat([], R, W, P) ->
    {ok, R, W, P}.

%% -------------------------------------------------------------------------

listen(Name) ->
    gen_listen(inet_tcp, Name).

gen_listen(Driver, Name) ->
    case inet_tcp_dist:gen_listen(Driver, Name) of
        {ok, {Socket, Address, Creation}} ->
            inet:setopts(Socket, [{packet, 4}]),
            {ok, {Socket, Address#net_address{protocol=tls}, Creation}};
        Other ->
            Other
    end.

%% -------------------------------------------------------------------------

accept(Listen) ->
    gen_accept(inet_tcp, Listen).

gen_accept(Driver, Listen) ->
    Kernel = self(),
    monitor_pid(
      spawn_opt(
        fun () ->
                accept_loop(Driver, Listen, Kernel)
        end,
        [link, {priority, max}])).

accept_loop(Driver, Listen, Kernel) ->
    case Driver:accept(Listen) of
        {ok, Socket} ->
            Opts = get_ssl_options(server),
            wait_for_code_server(),
            case ssl:ssl_accept(
                   Socket, [{active, false}, {packet, 4}] ++ Opts,
                   net_kernel:connecttime()) of
                {ok, #sslsocket{pid = DistCtrl} = SslSocket} ->
                    monitor_pid(DistCtrl),
                    trace(
                      Kernel !
                          {accept, self(), DistCtrl,
                           Driver:family(), tls}),
                    receive
                        {Kernel, controller, Pid} ->
                            ok = ssl:controlling_process(SslSocket, Pid),
                            trace(
                              Pid ! {self(), controller});
                        {Kernel, unsupported_protocol} ->
                            exit(trace(unsupported_protocol))
                    end,
                    accept_loop(Driver, Listen, Kernel);
		{error, {options, _}} = Error ->
		    %% Bad options: that's probably our fault.
                    %% Let's log that.
		    error_logger:error_msg(
                      "Cannot accept TLS distribution connection: ~s~n",
                      [ssl:format_error(Error)]),
                    _ = trace(Error),
                    gen_tcp:close(Socket);
		Other ->
                    _ = trace(Other),
                    gen_tcp:close(Socket)
	    end;
	Error ->
	    exit(trace(Error))
    end,
    accept_loop(Driver, Listen, Kernel).

wait_for_code_server() ->
    %% This is an ugly hack.  Upgrading a socket to TLS requires the
    %% crypto module to be loaded.  Loading the crypto module triggers
    %% its on_load function, which calls code:priv_dir/1 to find the
    %% directory where its NIF library is.  However, distribution is
    %% started earlier than the code server, so the code server is not
    %% necessarily started yet, and code:priv_dir/1 might fail because
    %% of that, if we receive an incoming connection on the
    %% distribution port early enough.
    %%
    %% If the on_load function of a module fails, the module is
    %% unloaded, and the function call that triggered loading it fails
    %% with 'undef', which is rather confusing.
    %%
    %% Thus, the accept process will terminate, and be
    %% restarted by ssl_dist_sup.  However, it won't have any memory
    %% of being asked by net_kernel to listen for incoming
    %% connections.  Hence, the node will believe that it's open for
    %% distribution, but it actually isn't.
    %%
    %% So let's avoid that by waiting for the code server to start.
    case whereis(code_server) of
	undefined ->
	    timer:sleep(10),
	    wait_for_code_server();
	Pid when is_pid(Pid) ->
	    ok
    end.

%% -------------------------------------------------------------------------

accept_connection(AcceptPid, DistCtrl, MyNode, Allowed, SetupTime) ->
    gen_accept_connection(
      inet_tcp, AcceptPid, DistCtrl, MyNode, Allowed, SetupTime).

gen_accept_connection(
  Driver, AcceptPid, DistCtrl, MyNode, Allowed, SetupTime) ->
    Kernel = self(),
    monitor_pid(
      spawn_opt(
        fun() ->
                do_accept(
                  Driver, Kernel, AcceptPid, DistCtrl,
                  MyNode, Allowed, SetupTime)
        end,
        [link, {priority, max}])).

do_accept(Driver, Kernel, AcceptPid, DistCtrl, MyNode, Allowed, SetupTime) ->
    SslSocket = ssl_connection:get_sslsocket(DistCtrl),
    receive
	{AcceptPid, controller} ->
	    Timer = dist_util:start_timer(SetupTime),
	    case check_ip(Driver, SslSocket) of
		true ->
                    HSData0 = hs_data_common(SslSocket),
                    HSData =
                        HSData0#hs_data{
                          kernel_pid = Kernel,
                          this_node = MyNode,
                          socket = DistCtrl,
                          timer = Timer,
                          this_flags = 0,
                          allowed = Allowed},
		    dist_util:handshake_other_started(trace(HSData));
		{false,IP} ->
		    error_logger:error_msg(
                      "** Connection attempt from "
                      "disallowed IP ~w ** ~n", [IP]),
		    ?shutdown(trace(no_node))
	    end
    end.



setup(Node, Type, MyNode, LongOrShortNames, SetupTime) ->
    gen_setup(inet_tcp, Node, Type, MyNode, LongOrShortNames, SetupTime).

gen_setup(Driver, Node, Type, MyNode, LongOrShortNames, SetupTime) ->
    Kernel = self(),
    monitor_pid(
      spawn_opt(
        fun() ->
                do_setup(
                  Driver, Kernel, Node, Type,
                  MyNode, LongOrShortNames, SetupTime)
        end,
        [link, {priority, max}])).

do_setup(Driver, Kernel, Node, Type, MyNode, LongOrShortNames, SetupTime) ->
    [Name, Address] = splitnode(Driver, Node, LongOrShortNames),
    case Driver:getaddr(Address) of
	{ok, Ip} ->
            Timer = trace(dist_util:start_timer(SetupTime)),
	    ErlEpmd = net_kernel:epmd_module(),
	    case ErlEpmd:port_please(Name, Ip) of
		{port, TcpPort, Version} ->
                    Opts = trace(connect_options(get_ssl_options(client))),
		    dist_util:reset_timer(Timer),
                    case ssl:connect(
                           Ip, TcpPort,
                           [binary, {active, false}, {packet, 4},
                            Driver:family(), nodelay()] ++ Opts,
                           net_kernel:connecttime()) of
			{ok, #sslsocket{pid = DistCtrl} = SslSocket} ->
                            monitor_pid(DistCtrl),
                            ok = ssl:controlling_process(SslSocket, self()),
                            HSData0 = hs_data_common(SslSocket),
			    HSData =
                                HSData0#hs_data{
                                  kernel_pid = Kernel,
                                  other_node = Node,
                                  this_node = MyNode,
                                  socket = DistCtrl,
                                  timer = Timer,
                                  this_flags = 0,
                                  other_version = Version,
                                  request_type = Type},
			    dist_util:handshake_we_started(trace(HSData));
			Other ->
			    %% Other Node may have closed since 
			    %% port_please !
			    ?shutdown2(
                               Node,
                               trace({shutdown, {connect_failed, Other}}))
		    end;
		Other ->
		    ?shutdown2(
                       Node,
                       trace({shutdown, {port_please_failed, Other}}))
	    end;
	Other ->
	    ?shutdown2(Node, trace({shutdown, {getaddr_failed, Other}}))
    end.

close(Socket) ->
    gen_close(inet, Socket).

gen_close(Driver, Socket) ->
    trace(Driver:close(Socket)).

%% ------------------------------------------------------------
%% Do only accept new connection attempts from nodes at our
%% own LAN, if the check_ip environment parameter is true.
%% ------------------------------------------------------------
check_ip(Driver, SslSocket) ->
    case application:get_env(check_ip) of
	{ok, true} ->
	    case get_ifs(SslSocket) of
		{ok, IFs, IP} ->
		    check_ip(Driver, IFs, IP);
		_ ->
		    ?shutdown(no_node)
	    end;
	_ ->
	    true
    end.

check_ip(Driver, [{OwnIP, _, Netmask}|IFs], PeerIP) ->
    case {Driver:mask(Netmask, PeerIP), Driver:mask(Netmask, OwnIP)} of
	{M, M} -> true;
	_      -> check_ip(IFs, PeerIP)
    end;
check_ip(_Driver, [], PeerIP) ->
    {false, PeerIP}.

get_ifs(#sslsocket{fd = {gen_tcp, Socket, _}}) ->
    case inet:peername(Socket) of
	{ok, {IP, _}} ->
            %% XXX this is seriously broken for IPv6
	    case inet:getif(Socket) of
		{ok, IFs} -> {ok, IFs, IP};
		Error     -> Error
	    end;
	Error ->
	    Error
    end.


%% If Node is illegal terminate the connection setup!!
splitnode(Driver, Node, LongOrShortNames) ->
    case split_node(atom_to_list(Node), $@, []) of
	[Name|Tail] when Tail =/= [] ->
	    Host = lists:append(Tail),
	    check_node(Driver, Name, Node, Host, LongOrShortNames);
	[_] ->
	    error_logger:error_msg(
              "** Nodename ~p illegal, no '@' character **~n",
              [Node]),
	    ?shutdown(Node);
	_ ->
	    error_logger:error_msg(
              "** Nodename ~p illegal **~n", [Node]),
	    ?shutdown(Node)
    end.

check_node(Driver, Name, Node, Host, LongOrShortNames) ->
    case split_node(Host, $., []) of
	[_] when LongOrShortNames == longnames ->
	    case Driver:parse_address(Host) of
		{ok, _} ->
		    [Name, Host];
		_ ->
		    error_logger:error_msg(
                      "** System running to use "
                      "fully qualified hostnames **~n"
                      "** Hostname ~s is illegal **~n",
                      [Host]),
		    ?shutdown(Node)
	    end;
	[_, _ | _] when LongOrShortNames == shortnames ->
	    error_logger:error_msg(
              "** System NOT running to use "
              "fully qualified hostnames **~n"
              "** Hostname ~s is illegal **~n",
              [Host]),
	    ?shutdown(Node);
	_ ->
	    [Name, Host]
    end.

split_node(Node) when is_atom(Node) ->
    case split_node(atom_to_list(Node), $@, []) of
        [_, Host] ->
            Host;
        _ ->
            false
    end;
split_node(_) ->
    false.
%%
split_node([Chr|T], Chr, Ack) -> 
    [lists:reverse(Ack)|split_node(T, Chr, [])];
split_node([H|T], Chr, Ack) -> 
    split_node(T, Chr, [H|Ack]);
split_node([], _, Ack) -> 
    [lists:reverse(Ack)].

%% -------------------------------------------------------------------------

connect_options(Opts) ->
    case application:get_env(kernel, inet_dist_connect_options) of
	{ok,ConnectOpts} ->
	    lists:ukeysort(1, ConnectOpts ++ Opts);
	_ ->
	    Opts
    end.

%% we may not always want the nodelay behaviour
%% for performance reasons
nodelay() ->
    case application:get_env(kernel, dist_nodelay) of
	undefined ->
	    {nodelay, true};
	{ok, true} ->
	    {nodelay, true};
	{ok, false} ->
	    {nodelay, false};
	_ ->
	    {nodelay, true}
    end.


get_ssl_options(Type) ->
    case init:get_argument(ssl_dist_opt) of
	{ok, Args} ->
	    [{erl_dist, true} | ssl_options(Type, lists:append(Args))];
	_ ->
	    [{erl_dist, true}]
    end.

ssl_options(_,[]) ->
    [];
ssl_options(server, ["client_" ++ _, _Value |T]) ->
    ssl_options(server,T);
ssl_options(client, ["server_" ++ _, _Value|T]) ->
    ssl_options(client,T);
ssl_options(server, ["server_certfile", Value|T]) ->
    [{certfile, Value} | ssl_options(server,T)];
ssl_options(client, ["client_certfile", Value | T]) ->
    [{certfile, Value} | ssl_options(client,T)];
ssl_options(server, ["server_cacertfile", Value|T]) ->
    [{cacertfile, Value} | ssl_options(server,T)];
ssl_options(client, ["client_cacertfile", Value|T]) ->
    [{cacertfile, Value} | ssl_options(client,T)];
ssl_options(server, ["server_keyfile", Value|T]) ->
    [{keyfile, Value} | ssl_options(server,T)];
ssl_options(client, ["client_keyfile", Value|T]) ->
    [{keyfile, Value} | ssl_options(client,T)];
ssl_options(server, ["server_password", Value|T]) ->
    [{password, Value} | ssl_options(server,T)];
ssl_options(client, ["client_password", Value|T]) ->
    [{password, Value} | ssl_options(client,T)];
ssl_options(server, ["server_verify", Value|T]) ->
    [{verify, atomize(Value)} | ssl_options(server,T)];
ssl_options(client, ["client_verify", Value|T]) ->
    [{verify, atomize(Value)} | ssl_options(client,T)];
ssl_options(server, ["server_verify_fun", Value|T]) ->
    [{verify_fun, verify_fun(Value)} | ssl_options(server,T)];
ssl_options(client, ["client_verify_fun", Value|T]) ->
    [{verify_fun, verify_fun(Value)} | ssl_options(client,T)];
ssl_options(server, ["server_crl_check", Value|T]) ->
    [{crl_check, atomize(Value)} | ssl_options(server,T)];
ssl_options(client, ["client_crl_check", Value|T]) ->
    [{crl_check, atomize(Value)} | ssl_options(client,T)];
ssl_options(server, ["server_crl_cache", Value|T]) ->
    [{crl_cache, termify(Value)} | ssl_options(server,T)];
ssl_options(client, ["client_crl_cache", Value|T]) ->
    [{crl_cache, termify(Value)} | ssl_options(client,T)];
ssl_options(server, ["server_reuse_sessions", Value|T]) ->
    [{reuse_sessions, atomize(Value)} | ssl_options(server,T)];
ssl_options(client, ["client_reuse_sessions", Value|T]) ->
    [{reuse_sessions, atomize(Value)} | ssl_options(client,T)];
ssl_options(server, ["server_secure_renegotiate", Value|T]) ->
    [{secure_renegotiate, atomize(Value)} | ssl_options(server,T)];
ssl_options(client, ["client_secure_renegotiate", Value|T]) ->
    [{secure_renegotiate, atomize(Value)} | ssl_options(client,T)];
ssl_options(server, ["server_depth", Value|T]) ->
    [{depth, list_to_integer(Value)} | ssl_options(server,T)];
ssl_options(client, ["client_depth", Value|T]) ->
    [{depth, list_to_integer(Value)} | ssl_options(client,T)];
ssl_options(server, ["server_hibernate_after", Value|T]) ->
    [{hibernate_after, list_to_integer(Value)} | ssl_options(server,T)];
ssl_options(client, ["client_hibernate_after", Value|T]) ->
    [{hibernate_after, list_to_integer(Value)} | ssl_options(client,T)];
ssl_options(server, ["server_ciphers", Value|T]) ->
    [{ciphers, Value} | ssl_options(server,T)];
ssl_options(client, ["client_ciphers", Value|T]) ->
    [{ciphers, Value} | ssl_options(client,T)];
ssl_options(server, ["server_dhfile", Value|T]) ->
    [{dhfile, Value} | ssl_options(server,T)];
ssl_options(server, ["server_fail_if_no_peer_cert", Value|T]) ->
    [{fail_if_no_peer_cert, atomize(Value)} | ssl_options(server,T)];
ssl_options(Type, Opts) ->
    error(malformed_ssl_dist_opt, [Type, Opts]).

atomize(List) when is_list(List) ->
    list_to_atom(List);
atomize(Atom) when is_atom(Atom) ->
    Atom.

termify(String) when is_list(String) ->
    {ok, Tokens, _} = erl_scan:string(String ++ "."),
    {ok, Term} = erl_parse:parse_term(Tokens),
    Term.

verify_fun(Value) ->
    case termify(Value) of
	{Mod, Func, State} when is_atom(Mod), is_atom(Func) ->
	    Fun = fun Mod:Func/3,
	    {Fun, State};
	_ ->
	    error(malformed_ssl_dist_opt, [Value])
    end.

%% -------------------------------------------------------------------------

%% Trace point
trace(Term) -> Term.

%% Keep an eye on distribution Pid:s we know of
monitor_pid(Pid) ->
    %%spawn(
    %%  fun () ->
    %%          MRef = erlang:monitor(process, Pid),
    %%          receive
    %%              {'DOWN', MRef, _, _, normal} ->
    %%                  error_logger:error_report(
    %%                    [dist_proc_died,
    %%                     {reason, normal},
    %%                     {pid, Pid}]);
    %%              {'DOWN', MRef, _, _, Reason} ->
    %%                  error_logger:info_report(
    %%                    [dist_proc_died,
    %%                     {reason, Reason},
    %%                     {pid, Pid}])
    %%          end
    %%  end),
    Pid.

dbg() ->
    dbg:stop(),
    dbg:tracer(),
    dbg:p(all, c),
    dbg:tpl(?MODULE, cx),
    dbg:tpl(erlang, dist_ctrl_get_data_notification, cx),
    dbg:tpl(erlang, dist_ctrl_get_data, cx),
    dbg:tpl(erlang, dist_ctrl_put_data, cx),
    ok.