summaryrefslogtreecommitdiff
path: root/src/util/client.c
blob: 72c83e29bf1e2c2b272d08426cc6ce474f2cae37 (plain)
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
771
772
773
774
775
776
777
778
779
780
781
782
783
784
785
786
787
788
789
790
791
792
793
794
795
796
797
798
799
800
801
802
803
804
805
806
807
808
809
810
811
812
813
814
815
816
817
818
819
820
821
822
823
824
825
826
827
828
829
830
831
832
833
834
835
836
837
838
839
840
841
842
843
844
845
846
847
848
849
850
851
852
853
854
855
856
857
858
859
860
861
862
863
864
865
866
867
868
869
870
871
872
873
874
875
876
877
878
879
880
881
882
883
884
885
886
887
888
889
890
891
892
893
894
895
896
897
898
899
900
901
902
903
904
905
906
907
908
909
910
911
912
913
914
915
916
917
918
919
920
921
922
923
924
925
926
927
928
929
930
931
932
933
934
935
936
937
938
939
940
941
942
943
944
945
946
947
948
949
950
951
952
953
954
955
956
957
958
959
960
961
962
963
964
965
966
967
968
969
970
971
972
973
974
975
976
977
978
979
980
981
982
983
984
985
986
987
988
989
990
991
992
993
994
995
996
997
998
999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
/*
     This file is part of GNUnet.
     (C) 2001, 2002, 2006, 2008, 2009 Christian Grothoff (and other contributing authors)

     GNUnet is free software; you can redistribute it and/or modify
     it under the terms of the GNU General Public License as published
     by the Free Software Foundation; either version 2, or (at your
     option) any later version.

     GNUnet is distributed in the hope that it will be useful, but
     WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     General Public License for more details.

     You should have received a copy of the GNU General Public License
     along with GNUnet; see the file COPYING.  If not, write to the
     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
     Boston, MA 02111-1307, USA.
*/

/**
 * @file util/client.c
 * @brief code for access to services
 * @author Christian Grothoff
 *
 * Generic TCP code for reliable, record-oriented TCP
 * connections between clients and service providers.
 */

#include "platform.h"
#include "gnunet_common.h"
#include "gnunet_client_lib.h"
#include "gnunet_protocols.h"
#include "gnunet_server_lib.h"
#include "gnunet_scheduler_lib.h"


/**
 * How often do we re-try tranmsitting requests before giving up?
 * Note that if we succeeded transmitting a request but failed to read
 * a response, we do NOT re-try.
 */
#define MAX_ATTEMPTS 50

#define LOG(kind,...) GNUNET_log_from (kind, "util",__VA_ARGS__)

/**
 * Handle for a transmission request.
 */
struct GNUNET_CLIENT_TransmitHandle
{
  /**
   * Connection state.
   */
  struct GNUNET_CLIENT_Connection *sock;

  /**
   * Function to call to get the data for transmission.
   */
  GNUNET_CONNECTION_TransmitReadyNotify notify;

  /**
   * Closure for notify.
   */
  void *notify_cls;

  /**
   * Handle to the transmission with the underlying
   * connection.
   */
  struct GNUNET_CONNECTION_TransmitHandle *th;

  /**
   * If we are re-trying and are delaying to do so,
   * handle to the scheduled task managing the delay.
   */
  GNUNET_SCHEDULER_TaskIdentifier reconnect_task;

  /**
   * Timeout for the operation overall.
   */
  struct GNUNET_TIME_Absolute timeout;

  /**
   * Number of bytes requested.
   */
  size_t size;

  /**
   * Are we allowed to re-try to connect without telling
   * the user (of this API) about the connection troubles?
   */
  int auto_retry;

  /**
   * Number of attempts left for transmitting the request.  We may
   * fail the first time (say because the service is not yet up), in
   * which case (if auto_retry is set) we wait a bit and re-try
   * (timeout permitting).
   */
  unsigned int attempts_left;

};


/**
 * Context for processing
 * "GNUNET_CLIENT_transmit_and_get_response" requests.
 */
struct TransmitGetResponseContext
{
  /**
   * Client handle.
   */
  struct GNUNET_CLIENT_Connection *sock;

  /**
   * Message to transmit; do not free, allocated
   * right after this struct.
   */
  const struct GNUNET_MessageHeader *hdr;

  /**
   * Timeout to use.
   */
  struct GNUNET_TIME_Absolute timeout;

  /**
   * Function to call when done.
   */
  GNUNET_CLIENT_MessageHandler rn;

  /**
   * Closure for "rn".
   */
  void *rn_cls;
};

/**
 * Struct to refer to a GNUnet TCP connection.
 * This is more than just a socket because if the server
 * drops the connection, the client automatically tries
 * to reconnect (and for that needs connection information).
 */
struct GNUNET_CLIENT_Connection
{

  /**
   * the socket handle, NULL if not live
   */
  struct GNUNET_CONNECTION_Handle *sock;

  /**
   * Our configuration.
   */
  const struct GNUNET_CONFIGURATION_Handle *cfg;

  /**
   * Name of the service we interact with.
   */
  char *service_name;

  /**
   * Context of a transmit_and_get_response operation, NULL
   * if no such operation is pending.
   */
  struct TransmitGetResponseContext *tag;

  /**
   * Handler for current receiver task.
   */
  GNUNET_CLIENT_MessageHandler receiver_handler;

  /**
   * Closure for receiver_handler.
   */
  void *receiver_handler_cls;

  /**
   * Handle for a pending transmission request, NULL if there is
   * none pending.
   */
  struct GNUNET_CLIENT_TransmitHandle *th;

  /**
   * Handler for service test completion (NULL unless in service_test)
   */
  GNUNET_SCHEDULER_Task test_cb;

  /**
   * Deadline for calling 'test_cb'.
   */
  struct GNUNET_TIME_Absolute test_deadline;

  /**
   * If we are re-trying and are delaying to do so,
   * handle to the scheduled task managing the delay.
   */
  GNUNET_SCHEDULER_TaskIdentifier receive_task;

  /**
   * Closure for test_cb (NULL unless in service_test)
   */
  void *test_cb_cls;

  /**
   * Buffer for received message.
   */
  char *received_buf;

  /**
   * Timeout for receiving a response (absolute time).
   */
  struct GNUNET_TIME_Absolute receive_timeout;

  /**
   * Current value for our incremental back-off (for
   * connect re-tries).
   */
  struct GNUNET_TIME_Relative back_off;

  /**
   * Number of bytes in received_buf that are valid.
   */
  size_t received_pos;

  /**
   * Size of received_buf.
   */
  unsigned int received_size;

  /**
   * Do we have a complete response in received_buf?
   */
  int msg_complete;

  /**
   * Are we currently busy doing receive-processing?
   * GNUNET_YES if so, GNUNET_NO if not.
   */
  int in_receive;

  /**
   * How often have we tried to connect?
   */
  unsigned int attempts;

};


/**
 * Try to connect to the service.
 *
 * @param service_name name of service to connect to
 * @param cfg configuration to use
 * @param attempt counter used to alternate between IP and UNIX domain sockets
 * @return NULL on error
 */
static struct GNUNET_CONNECTION_Handle *
do_connect (const char *service_name,
            const struct GNUNET_CONFIGURATION_Handle *cfg, unsigned int attempt)
{
  struct GNUNET_CONNECTION_Handle *sock;
  char *hostname;
  char *unixpath;
  unsigned long long port;

  sock = NULL;
#if AF_UNIX
  if (0 == (attempt % 2))
  {
    /* on even rounds, try UNIX */
    unixpath = NULL;
    if ((GNUNET_OK == GNUNET_CONFIGURATION_get_value_string (cfg, service_name, "UNIXPATH", &unixpath)) && (0 < strlen (unixpath)))     /* We have a non-NULL unixpath, does that mean it's valid? */
    {
      sock = GNUNET_CONNECTION_create_from_connect_to_unixpath (cfg, unixpath);
      if (sock != NULL)
      {
        LOG (GNUNET_ERROR_TYPE_DEBUG, "Connected to unixpath `%s'!\n",
             unixpath);
        GNUNET_free (unixpath);
        return sock;
      }
    }
    GNUNET_free_non_null (unixpath);
  }
#endif

  if (GNUNET_YES ==
      GNUNET_CONFIGURATION_have_value (cfg, service_name, "PORT"))
  {
    if ((GNUNET_OK !=
	 GNUNET_CONFIGURATION_get_value_number (cfg, service_name, "PORT", &port))
	|| (port > 65535) ||
	(GNUNET_OK !=
	 GNUNET_CONFIGURATION_get_value_string (cfg, service_name, "HOSTNAME",
						&hostname)))
    {
      LOG (GNUNET_ERROR_TYPE_WARNING,
	   _
	   ("Could not determine valid hostname and port for service `%s' from configuration.\n"),
	   service_name);
      return NULL;
    }
    if (0 == strlen (hostname))
    {
      GNUNET_free (hostname);
      LOG (GNUNET_ERROR_TYPE_WARNING,
	   _("Need a non-empty hostname for service `%s'.\n"), service_name);
      return NULL;
    }
  }
  else
  {
    /* unspecified means 0 (disabled) */
    port = 0;
    hostname = NULL;
  }
  if (port == 0)
  {
#if AF_UNIX
    if (0 != (attempt % 2))
    {
      /* try UNIX */
      unixpath = NULL;
      if ((GNUNET_OK ==
           GNUNET_CONFIGURATION_get_value_string (cfg, service_name, "UNIXPATH",
                                                  &unixpath)) &&
          (0 < strlen (unixpath)))
      {
        sock =
            GNUNET_CONNECTION_create_from_connect_to_unixpath (cfg, unixpath);
        if (sock != NULL)
        {
          GNUNET_free (unixpath);
          GNUNET_free_non_null (hostname);
          return sock;
        }
      }
      GNUNET_free_non_null (unixpath);
    }
#endif
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Port is 0 for service `%s', UNIXPATH did not work, returning NULL!\n",
         service_name);
    GNUNET_free_non_null (hostname);
    return NULL;
  }

  sock = GNUNET_CONNECTION_create_from_connect (cfg, hostname, port);
  GNUNET_free (hostname);
  return sock;
}


/**
 * Get a connection with a service.
 *
 * @param service_name name of the service
 * @param cfg configuration to use
 * @return NULL on error (service unknown to configuration)
 */
struct GNUNET_CLIENT_Connection *
GNUNET_CLIENT_connect (const char *service_name,
                       const struct GNUNET_CONFIGURATION_Handle *cfg)
{
  struct GNUNET_CLIENT_Connection *ret;
  struct GNUNET_CONNECTION_Handle *sock;

  sock = do_connect (service_name, cfg, 0);
  ret = GNUNET_malloc (sizeof (struct GNUNET_CLIENT_Connection));
  ret->attempts = 1;
  ret->sock = sock;
  ret->service_name = GNUNET_strdup (service_name);
  ret->cfg = cfg;
  ret->back_off = GNUNET_TIME_UNIT_MILLISECONDS;
  return ret;
}


/**
 * Destroy connection with the service.  This will automatically
 * cancel any pending "receive" request (however, the handler will
 * *NOT* be called, not even with a NULL message).  Any pending
 * transmission request will also be cancelled UNLESS the callback for
 * the transmission request has already been called, in which case the
 * transmission 'finish_pending_write' argument determines whether or
 * not the write is guaranteed to complete before the socket is fully
 * destroyed (unless, of course, there is an error with the server in
 * which case the message may still be lost).
 *
 * @param sock handle to the service connection
 */
void
GNUNET_CLIENT_disconnect (struct GNUNET_CLIENT_Connection *sock)
{
  if (sock->in_receive == GNUNET_YES)
  {
    GNUNET_CONNECTION_receive_cancel (sock->sock);
    sock->in_receive = GNUNET_NO;
  }
  if (sock->th != NULL)
  {
    GNUNET_CLIENT_notify_transmit_ready_cancel (sock->th);
    sock->th = NULL;
  }
  if (NULL != sock->sock)
  {
    GNUNET_CONNECTION_destroy (sock->sock, GNUNET_NO);
    sock->sock = NULL;
  }
  if (sock->receive_task != GNUNET_SCHEDULER_NO_TASK)
  {
    GNUNET_SCHEDULER_cancel (sock->receive_task);
    sock->receive_task = GNUNET_SCHEDULER_NO_TASK;
  }
  if (sock->tag != NULL)
  {
    GNUNET_free (sock->tag);
    sock->tag = NULL;
  }
  sock->receiver_handler = NULL;
  GNUNET_array_grow (sock->received_buf, sock->received_size, 0);
  GNUNET_free (sock->service_name);
  GNUNET_free (sock);
}


/**
 * Check if message is complete
 */
static void
check_complete (struct GNUNET_CLIENT_Connection *conn)
{
  if ((conn->received_pos >= sizeof (struct GNUNET_MessageHeader)) &&
      (conn->received_pos >=
       ntohs (((const struct GNUNET_MessageHeader *) conn->received_buf)->
              size)))
    conn->msg_complete = GNUNET_YES;
}


/**
 * Callback function for data received from the network.  Note that
 * both "available" and "errCode" would be 0 if the read simply timed out.
 *
 * @param cls closure
 * @param buf pointer to received data
 * @param available number of bytes availabe in "buf",
 *        possibly 0 (on errors)
 * @param addr address of the sender
 * @param addrlen size of addr
 * @param errCode value of errno (on errors receiving)
 */
static void
receive_helper (void *cls, const void *buf, size_t available,
                const struct sockaddr *addr, socklen_t addrlen, int errCode)
{
  struct GNUNET_CLIENT_Connection *conn = cls;
  struct GNUNET_TIME_Relative remaining;
  GNUNET_CLIENT_MessageHandler receive_handler;
  void *receive_handler_cls;

  GNUNET_assert (conn->msg_complete == GNUNET_NO);
  conn->in_receive = GNUNET_NO;
  if ((available == 0) || (conn->sock == NULL) || (errCode != 0))
  {
    /* signal timeout! */
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Timeout in receive_helper, available %u, conn->sock %s, errCode `%s'\n",
         (unsigned int) available, conn->sock == NULL ? "NULL" : "non-NULL",
         STRERROR (errCode));
    if (NULL != (receive_handler = conn->receiver_handler))
    {
      receive_handler_cls = conn->receiver_handler_cls;
      conn->receiver_handler = NULL;
      receive_handler (receive_handler_cls, NULL);
    }
    return;
  }

  /* FIXME: optimize for common fast case where buf contains the
   * entire message and we need no copying... */


  /* slow path: append to array */
  if (conn->received_size < conn->received_pos + available)
    GNUNET_array_grow (conn->received_buf, conn->received_size,
                       conn->received_pos + available);
  memcpy (&conn->received_buf[conn->received_pos], buf, available);
  conn->received_pos += available;
  check_complete (conn);
  /* check for timeout */
  remaining = GNUNET_TIME_absolute_get_remaining (conn->receive_timeout);
  if (remaining.rel_value == 0)
  {
    /* signal timeout! */
    if (NULL != conn->receiver_handler)
      conn->receiver_handler (conn->receiver_handler_cls, NULL);
    return;
  }
  /* back to receive -- either for more data or to call callback! */
  GNUNET_CLIENT_receive (conn, conn->receiver_handler,
                         conn->receiver_handler_cls, remaining);
}


/**
 * Continuation to call the receive callback.
 *
 * @param cls  our handle to the client connection
 * @param tc scheduler context
 */
static void
receive_task (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
{
  struct GNUNET_CLIENT_Connection *sock = cls;
  GNUNET_CLIENT_MessageHandler handler = sock->receiver_handler;
  const struct GNUNET_MessageHeader *cmsg =
      (const struct GNUNET_MessageHeader *) sock->received_buf;
  void *handler_cls = sock->receiver_handler_cls;
  uint16_t msize = ntohs (cmsg->size);
  char mbuf[msize];
  struct GNUNET_MessageHeader *msg = (struct GNUNET_MessageHeader *) mbuf;

  LOG (GNUNET_ERROR_TYPE_DEBUG, "Received message of type %u and size %u\n",
       ntohs (cmsg->type), msize);
  sock->receive_task = GNUNET_SCHEDULER_NO_TASK;
  GNUNET_assert (GNUNET_YES == sock->msg_complete);
  GNUNET_assert (sock->received_pos >= msize);
  memcpy (msg, cmsg, msize);
  memmove (sock->received_buf, &sock->received_buf[msize],
           sock->received_pos - msize);
  sock->received_pos -= msize;
  sock->msg_complete = GNUNET_NO;
  sock->receiver_handler = NULL;
  check_complete (sock);
  if (handler != NULL)
    handler (handler_cls, msg);
}


/**
 * Read from the service.
 *
 * @param sock the service
 * @param handler function to call with the message
 * @param handler_cls closure for handler
 * @param timeout how long to wait until timing out
 */
void
GNUNET_CLIENT_receive (struct GNUNET_CLIENT_Connection *sock,
                       GNUNET_CLIENT_MessageHandler handler, void *handler_cls,
                       struct GNUNET_TIME_Relative timeout)
{
  if (sock->sock == NULL)
  {
    /* already disconnected, fail instantly! */
    GNUNET_break (0);           /* this should not happen in well-written code! */
    if (NULL != handler)
      handler (handler_cls, NULL);
    return;
  }
  sock->receiver_handler = handler;
  sock->receiver_handler_cls = handler_cls;
  sock->receive_timeout = GNUNET_TIME_relative_to_absolute (timeout);
  if (GNUNET_YES == sock->msg_complete)
  {
    GNUNET_assert (GNUNET_SCHEDULER_NO_TASK == sock->receive_task);
    sock->receive_task = GNUNET_SCHEDULER_add_now (&receive_task, sock);
  }
  else
  {
    GNUNET_assert (sock->in_receive == GNUNET_NO);
    sock->in_receive = GNUNET_YES;
    LOG (GNUNET_ERROR_TYPE_DEBUG, "calling GNUNET_CONNECTION_receive\n");
    GNUNET_CONNECTION_receive (sock->sock, GNUNET_SERVER_MAX_MESSAGE_SIZE - 1,
                               timeout, &receive_helper, sock);
  }
}


/**
 * Report service unavailable.
 */
static void
service_test_error (GNUNET_SCHEDULER_Task task, void *task_cls)
{
  GNUNET_SCHEDULER_add_continuation (task, task_cls,
                                     GNUNET_SCHEDULER_REASON_TIMEOUT);
}


/**
 * Receive confirmation from test, service is up.
 *
 * @param cls closure
 * @param msg message received, NULL on timeout or fatal error
 */
static void
confirm_handler (void *cls, const struct GNUNET_MessageHeader *msg)
{
  struct GNUNET_CLIENT_Connection *conn = cls;

  /* We may want to consider looking at the reply in more
   * detail in the future, for example, is this the
   * correct service? FIXME! */
  if (msg != NULL)
  {
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Received confirmation that service is running.\n");
    GNUNET_SCHEDULER_add_continuation (conn->test_cb, conn->test_cb_cls,
                                       GNUNET_SCHEDULER_REASON_PREREQ_DONE);
  }
  else
  {
    service_test_error (conn->test_cb, conn->test_cb_cls);
  }
  GNUNET_CLIENT_disconnect (conn);
}


/**
 * Send the 'TEST' message to the service.  If successful, prepare to
 * receive the reply.
 *
 * @param cls the 'struct GNUNET_CLIENT_Connection' of the connection to test
 * @param size number of bytes available in buf
 * @param buf where to write the message
 * @return number of bytes written to buf
 */
static size_t
write_test (void *cls, size_t size, void *buf)
{
  struct GNUNET_CLIENT_Connection *conn = cls;
  struct GNUNET_MessageHeader *msg;

  if (size < sizeof (struct GNUNET_MessageHeader))
  {
    LOG (GNUNET_ERROR_TYPE_DEBUG, _("Failure to transmit TEST request.\n"));
    service_test_error (conn->test_cb, conn->test_cb_cls);
    GNUNET_CLIENT_disconnect (conn);
    return 0;                   /* client disconnected */
  }
  LOG (GNUNET_ERROR_TYPE_DEBUG, "Transmitting `%s' request.\n", "TEST");
  msg = (struct GNUNET_MessageHeader *) buf;
  msg->type = htons (GNUNET_MESSAGE_TYPE_TEST);
  msg->size = htons (sizeof (struct GNUNET_MessageHeader));
  GNUNET_CLIENT_receive (conn, &confirm_handler, conn,
                         GNUNET_TIME_absolute_get_remaining
                         (conn->test_deadline));
  return sizeof (struct GNUNET_MessageHeader);
}


/**
 * Test if the service is running.  If we are given a UNIXPATH or a local address,
 * we do this NOT by trying to connect to the service, but by trying to BIND to
 * the same port.  If the BIND fails, we know the service is running.
 *
 * @param service name of the service to wait for
 * @param cfg configuration to use
 * @param timeout how long to wait at most
 * @param task task to run if service is running
 *        (reason will be "PREREQ_DONE" (service running)
 *         or "TIMEOUT" (service not known to be running))
 * @param task_cls closure for task
 */
void
GNUNET_CLIENT_service_test (const char *service,
                            const struct GNUNET_CONFIGURATION_Handle *cfg,
                            struct GNUNET_TIME_Relative timeout,
                            GNUNET_SCHEDULER_Task task, void *task_cls)
{
  char *hostname;
  unsigned long long port;
  struct GNUNET_NETWORK_Handle *sock;
  struct GNUNET_CLIENT_Connection *conn;

  LOG (GNUNET_ERROR_TYPE_DEBUG, "Testing if service `%s' is running.\n",
       service);
#ifdef AF_UNIX
  {
    /* probe UNIX support */
    struct sockaddr_un s_un;
    size_t slen;
    char *unixpath;

    unixpath = NULL;
    if ((GNUNET_OK == GNUNET_CONFIGURATION_get_value_string (cfg, service, "UNIXPATH", &unixpath)) && (0 < strlen (unixpath)))  /* We have a non-NULL unixpath, does that mean it's valid? */
    {
      if (strlen (unixpath) >= sizeof (s_un.sun_path))
      {
        LOG (GNUNET_ERROR_TYPE_WARNING,
             _("UNIXPATH `%s' too long, maximum length is %llu\n"), unixpath,
             sizeof (s_un.sun_path));
      }
      else
      {
        sock = GNUNET_NETWORK_socket_create (PF_UNIX, SOCK_STREAM, 0);
        if (sock != NULL)
        {
          memset (&s_un, 0, sizeof (s_un));
          s_un.sun_family = AF_UNIX;
          slen = strlen (unixpath) + 1;
          if (slen >= sizeof (s_un.sun_path))
            slen = sizeof (s_un.sun_path) - 1;
          memcpy (s_un.sun_path, unixpath, slen);
          s_un.sun_path[slen] = '\0';
          slen = sizeof (struct sockaddr_un);
#if LINUX
          s_un.sun_path[0] = '\0';
#endif
#if HAVE_SOCKADDR_IN_SIN_LEN
          s_un.sun_len = (u_char) slen;
#endif
          if (GNUNET_OK !=
              GNUNET_NETWORK_socket_bind (sock, (const struct sockaddr *) &s_un,
                                          slen))
          {
            /* failed to bind => service must be running */
            GNUNET_free (unixpath);
            (void) GNUNET_NETWORK_socket_close (sock);
            GNUNET_SCHEDULER_add_continuation (task, task_cls,
                                               GNUNET_SCHEDULER_REASON_PREREQ_DONE);
            return;
          }
          (void) GNUNET_NETWORK_socket_close (sock);
        }
        /* let's try IP */
      }
    }
    GNUNET_free_non_null (unixpath);
  }
#endif

  hostname = NULL;
  if ((GNUNET_OK !=
       GNUNET_CONFIGURATION_get_value_number (cfg, service, "PORT", &port)) ||
      (port > 65535) ||
      (GNUNET_OK !=
       GNUNET_CONFIGURATION_get_value_string (cfg, service, "HOSTNAME",
                                              &hostname)))
  {
    /* UNIXPATH failed (if possible) AND IP failed => error */
    service_test_error (task, task_cls);
    return;
  }

  if (0 == strcmp ("localhost", hostname)
#if !LINUX
      && 0
#endif
      )
  {
    /* can test using 'bind' */
    struct sockaddr_in s_in;

    memset (&s_in, 0, sizeof (s_in));
#if HAVE_SOCKADDR_IN_SIN_LEN
    s_in.sin_len = sizeof (struct sockaddr_in);
#endif
    s_in.sin_family = AF_INET;
    s_in.sin_port = htons (port);

    sock = GNUNET_NETWORK_socket_create (AF_INET, SOCK_STREAM, 0);
    if (sock != NULL)
    {
      if (GNUNET_OK !=
          GNUNET_NETWORK_socket_bind (sock, (const struct sockaddr *) &s_in,
                                      sizeof (s_in)))
      {
        /* failed to bind => service must be running */
        GNUNET_free (hostname);
        (void) GNUNET_NETWORK_socket_close (sock);
        GNUNET_SCHEDULER_add_continuation (task, task_cls,
                                           GNUNET_SCHEDULER_REASON_PREREQ_DONE);
        return;
      }
      (void) GNUNET_NETWORK_socket_close (sock);
    }
  }

  if (0 == strcmp ("ip6-localhost", hostname)
#if !LINUX
      && 0
#endif
      )
  {
    /* can test using 'bind' */
    struct sockaddr_in6 s_in6;

    memset (&s_in6, 0, sizeof (s_in6));
#if HAVE_SOCKADDR_IN_SIN_LEN
    s_in6.sin6_len = sizeof (struct sockaddr_in6);
#endif
    s_in6.sin6_family = AF_INET6;
    s_in6.sin6_port = htons (port);

    sock = GNUNET_NETWORK_socket_create (AF_INET6, SOCK_STREAM, 0);
    if (sock != NULL)
    {
      if (GNUNET_OK !=
          GNUNET_NETWORK_socket_bind (sock, (const struct sockaddr *) &s_in6,
                                      sizeof (s_in6)))
      {
        /* failed to bind => service must be running */
        GNUNET_free (hostname);
        (void) GNUNET_NETWORK_socket_close (sock);
        GNUNET_SCHEDULER_add_continuation (task, task_cls,
                                           GNUNET_SCHEDULER_REASON_PREREQ_DONE);
        return;
      }
      (void) GNUNET_NETWORK_socket_close (sock);
    }
  }

  if (((0 == strcmp ("localhost", hostname)) ||
       (0 == strcmp ("ip6-localhost", hostname)))
#if !LINUX
      && 0
#endif
      )
  {
    /* all binds succeeded => claim service not running right now */
    GNUNET_free_non_null (hostname);
    service_test_error (task, task_cls);
    return;
  }
  GNUNET_free_non_null (hostname);

  /* non-localhost, try 'connect' method */
  conn = GNUNET_CLIENT_connect (service, cfg);
  if (conn == NULL)
  {
    LOG (GNUNET_ERROR_TYPE_INFO,
         _("Could not connect to service `%s', must not be running.\n"),
         service);
    service_test_error (task, task_cls);
    return;
  }
  conn->test_cb = task;
  conn->test_cb_cls = task_cls;
  conn->test_deadline = GNUNET_TIME_relative_to_absolute (timeout);

  if (NULL ==
      GNUNET_CLIENT_notify_transmit_ready (conn,
                                           sizeof (struct GNUNET_MessageHeader),
                                           timeout, GNUNET_YES, &write_test,
                                           conn))
  {
    LOG (GNUNET_ERROR_TYPE_WARNING,
         _("Failure to transmit request to service `%s'\n"), service);
    service_test_error (task, task_cls);
    GNUNET_CLIENT_disconnect (conn);
    return;
  }
}


/**
 * Connection notifies us about failure or success of
 * a transmission request.  Either pass it on to our
 * user or, if possible, retry.
 *
 * @param cls our "struct GNUNET_CLIENT_TransmissionHandle"
 * @param size number of bytes available for transmission
 * @param buf where to write them
 * @return number of bytes written to buf
 */
static size_t
client_notify (void *cls, size_t size, void *buf);


/**
 * This task is run if we should re-try connection to the
 * service after a while.
 *
 * @param cls our "struct GNUNET_CLIENT_TransmitHandle" of the request
 * @param tc unused
 */
static void
client_delayed_retry (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
{
  struct GNUNET_CLIENT_TransmitHandle *th = cls;
  struct GNUNET_TIME_Relative delay;

  th->reconnect_task = GNUNET_SCHEDULER_NO_TASK;
  if (0 != (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN))
  {
    LOG (GNUNET_ERROR_TYPE_DEBUG, "Transmission failed due to shutdown.\n");
    th->sock->th = NULL;
    th->notify (th->notify_cls, 0, NULL);
    GNUNET_free (th);
    return;
  }
  th->sock->sock =
      do_connect (th->sock->service_name, th->sock->cfg, th->sock->attempts++);
  if (NULL == th->sock->sock)
  {
    /* could happen if we're out of sockets */
    delay =
        GNUNET_TIME_relative_min (GNUNET_TIME_absolute_get_remaining
                                  (th->timeout), th->sock->back_off);
    th->sock->back_off =
        GNUNET_TIME_relative_min (GNUNET_TIME_relative_multiply
                                  (th->sock->back_off, 2),
                                  GNUNET_TIME_UNIT_SECONDS);
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Transmission failed %u times, trying again in %llums.\n",
         MAX_ATTEMPTS - th->attempts_left,
         (unsigned long long) delay.rel_value);
    th->reconnect_task =
        GNUNET_SCHEDULER_add_delayed (delay, &client_delayed_retry, th);
    return;
  }
  th->th =
      GNUNET_CONNECTION_notify_transmit_ready (th->sock->sock, th->size,
                                               GNUNET_TIME_absolute_get_remaining
                                               (th->timeout), &client_notify,
                                               th);
  if (th->th == NULL)
  {
    GNUNET_break (0);
    th->sock->th = NULL;
    th->notify (th->notify_cls, 0, NULL);
    GNUNET_free (th);
    return;
  }
}


/**
 * Connection notifies us about failure or success of a transmission
 * request.  Either pass it on to our user or, if possible, retry.
 *
 * @param cls our "struct GNUNET_CLIENT_TransmissionHandle"
 * @param size number of bytes available for transmission
 * @param buf where to write them
 * @return number of bytes written to buf
 */
static size_t
client_notify (void *cls, size_t size, void *buf)
{
  struct GNUNET_CLIENT_TransmitHandle *th = cls;
  size_t ret;
  struct GNUNET_TIME_Relative delay;

  th->th = NULL;
  th->sock->th = NULL;
  if (buf == NULL)
  {
    delay = GNUNET_TIME_absolute_get_remaining (th->timeout);
    delay.rel_value /= 2;
    if ((0 !=
         (GNUNET_SCHEDULER_REASON_SHUTDOWN & GNUNET_SCHEDULER_get_reason ())) ||
        (GNUNET_YES != th->auto_retry) || (0 == --th->attempts_left) ||
        (delay.rel_value < 1))
    {
      LOG (GNUNET_ERROR_TYPE_DEBUG,
           "Transmission failed %u times, giving up.\n",
           MAX_ATTEMPTS - th->attempts_left);
      GNUNET_break (0 == th->notify (th->notify_cls, 0, NULL));
      GNUNET_free (th);
      return 0;
    }
    /* auto-retry */
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Failed to connect to `%s', automatically trying again.\n",
         th->sock->service_name);
    GNUNET_CONNECTION_destroy (th->sock->sock, GNUNET_NO);
    th->sock->sock = NULL;
    delay = GNUNET_TIME_relative_min (delay, th->sock->back_off);
    th->sock->back_off =
        GNUNET_TIME_relative_min (GNUNET_TIME_relative_multiply
                                  (th->sock->back_off, 2),
                                  GNUNET_TIME_UNIT_SECONDS);
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         "Transmission failed %u times, trying again in %llums.\n",
         MAX_ATTEMPTS - th->attempts_left,
         (unsigned long long) delay.rel_value);
    th->sock->th = th;
    th->reconnect_task =
        GNUNET_SCHEDULER_add_delayed (delay, &client_delayed_retry, th);
    return 0;
  }
  GNUNET_assert (size >= th->size);
  ret = th->notify (th->notify_cls, size, buf);
  GNUNET_free (th);
  return ret;
}


/**
 * Ask the client to call us once the specified number of bytes
 * are free in the transmission buffer.  May call the notify
 * method immediately if enough space is available.
 *
 * @param sock connection to the service
 * @param size number of bytes to send
 * @param timeout after how long should we give up (and call
 *        notify with buf NULL and size 0)?
 * @param auto_retry if the connection to the service dies, should we
 *        automatically re-connect and retry (within the timeout period)
 *        or should we immediately fail in this case?  Pass GNUNET_YES
 *        if the caller does not care about temporary connection errors,
 *        for example because the protocol is stateless
 * @param notify function to call
 * @param notify_cls closure for notify
 * @return NULL if our buffer will never hold size bytes,
 *         a handle if the notify callback was queued (can be used to cancel)
 */
struct GNUNET_CLIENT_TransmitHandle *
GNUNET_CLIENT_notify_transmit_ready (struct GNUNET_CLIENT_Connection *sock,
                                     size_t size,
                                     struct GNUNET_TIME_Relative timeout,
                                     int auto_retry,
                                     GNUNET_CONNECTION_TransmitReadyNotify
                                     notify, void *notify_cls)
{
  struct GNUNET_CLIENT_TransmitHandle *th;

  if (NULL != sock->th)
  {
    /* If this breaks, you most likley called this function twice without waiting
     * for completion or canceling the request */
    GNUNET_break (0);
    return NULL;
  }
  th = GNUNET_malloc (sizeof (struct GNUNET_CLIENT_TransmitHandle));
  th->sock = sock;
  th->size = size;
  th->timeout = GNUNET_TIME_relative_to_absolute (timeout);
  th->auto_retry = auto_retry;
  th->notify = notify;
  th->notify_cls = notify_cls;
  th->attempts_left = MAX_ATTEMPTS;
  sock->th = th;
  if (sock->sock == NULL)
  {
    th->reconnect_task =
        GNUNET_SCHEDULER_add_delayed (sock->back_off, &client_delayed_retry,
                                      th);

  }
  else
  {
    th->th =
        GNUNET_CONNECTION_notify_transmit_ready (sock->sock, size, timeout,
                                                 &client_notify, th);
    if (NULL == th->th)
    {
      GNUNET_break (0);
      GNUNET_free (th);
      sock->th = NULL;
      return NULL;
    }
  }
  return th;
}


/**
 * Cancel a request for notification.
 *
 * @param th handle from the original request.
 */
void
GNUNET_CLIENT_notify_transmit_ready_cancel (struct GNUNET_CLIENT_TransmitHandle
                                            *th)
{
  if (th->reconnect_task != GNUNET_SCHEDULER_NO_TASK)
  {
    GNUNET_assert (NULL == th->th);
    GNUNET_SCHEDULER_cancel (th->reconnect_task);
    th->reconnect_task = GNUNET_SCHEDULER_NO_TASK;
  }
  else
  {
    GNUNET_assert (NULL != th->th);
    GNUNET_CONNECTION_notify_transmit_ready_cancel (th->th);
  }
  th->sock->th = NULL;
  GNUNET_free (th);
}


/**
 * Function called to notify a client about the socket
 * begin ready to queue the message.  "buf" will be
 * NULL and "size" zero if the socket was closed for
 * writing in the meantime.
 *
 * @param cls closure of type "struct TransmitGetResponseContext*"
 * @param size number of bytes available in buf
 * @param buf where the callee should write the message
 * @return number of bytes written to buf
 */
static size_t
transmit_for_response (void *cls, size_t size, void *buf)
{
  struct TransmitGetResponseContext *tc = cls;
  uint16_t msize;

  tc->sock->tag = NULL;
  msize = ntohs (tc->hdr->size);
  if (NULL == buf)
  {
    LOG (GNUNET_ERROR_TYPE_DEBUG,
         _("Could not submit request, not expecting to receive a response.\n"));
    if (NULL != tc->rn)
      tc->rn (tc->rn_cls, NULL);
    GNUNET_free (tc);
    return 0;
  }
  GNUNET_assert (size >= msize);
  memcpy (buf, tc->hdr, msize);
  GNUNET_CLIENT_receive (tc->sock, tc->rn, tc->rn_cls,
                         GNUNET_TIME_absolute_get_remaining (tc->timeout));
  GNUNET_free (tc);
  return msize;
}


/**
 * Convenience API that combines sending a request
 * to the service and waiting for a response.
 * If either operation times out, the callback
 * will be called with a "NULL" response (in which
 * case the connection should probably be destroyed).
 *
 * @param sock connection to use
 * @param hdr message to transmit
 * @param timeout when to give up (for both transmission
 *         and for waiting for a response)
 * @param auto_retry if the connection to the service dies, should we
 *        automatically re-connect and retry (within the timeout period)
 *        or should we immediately fail in this case?  Pass GNUNET_YES
 *        if the caller does not care about temporary connection errors,
 *        for example because the protocol is stateless
 * @param rn function to call with the response
 * @param rn_cls closure for rn
 * @return GNUNET_OK on success, GNUNET_SYSERR if a request
 *         is already pending
 */
int
GNUNET_CLIENT_transmit_and_get_response (struct GNUNET_CLIENT_Connection *sock,
                                         const struct GNUNET_MessageHeader *hdr,
                                         struct GNUNET_TIME_Relative timeout,
                                         int auto_retry,
                                         GNUNET_CLIENT_MessageHandler rn,
                                         void *rn_cls)
{
  struct TransmitGetResponseContext *tc;
  uint16_t msize;

  if (NULL != sock->th)
    return GNUNET_SYSERR;
  GNUNET_assert (sock->tag == NULL);
  msize = ntohs (hdr->size);
  tc = GNUNET_malloc (sizeof (struct TransmitGetResponseContext) + msize);
  tc->sock = sock;
  tc->hdr = (const struct GNUNET_MessageHeader *) &tc[1];
  memcpy (&tc[1], hdr, msize);
  tc->timeout = GNUNET_TIME_relative_to_absolute (timeout);
  tc->rn = rn;
  tc->rn_cls = rn_cls;
  if (NULL ==
      GNUNET_CLIENT_notify_transmit_ready (sock, msize, timeout, auto_retry,
                                           &transmit_for_response, tc))
  {
    GNUNET_break (0);
    GNUNET_free (tc);
    return GNUNET_SYSERR;
  }
  sock->tag = tc;
  return GNUNET_OK;
}



/*  end of client.c */