summaryrefslogtreecommitdiff
path: root/src/consensus/gnunet-service-consensus.c
blob: e30b92febc02ace93f2969a6827f844da6b1b957 (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
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
1273
1274
1275
1276
1277
1278
1279
1280
1281
1282
1283
1284
1285
1286
1287
1288
1289
1290
1291
1292
1293
1294
1295
1296
1297
1298
1299
1300
1301
1302
1303
1304
1305
1306
1307
1308
1309
1310
1311
1312
1313
1314
1315
1316
1317
1318
1319
1320
1321
1322
1323
1324
1325
1326
1327
1328
1329
1330
1331
1332
1333
1334
1335
1336
1337
1338
1339
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
1381
1382
1383
1384
1385
1386
1387
1388
1389
1390
1391
1392
1393
1394
1395
1396
1397
1398
1399
1400
1401
1402
1403
1404
1405
1406
1407
1408
/*
      This file is part of GNUnet
      Copyright (C) 2012, 2013 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 3, 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 consensus/gnunet-service-consensus.c
 * @brief multi-peer set reconciliation
 * @author Florian Dold
 */

#include "platform.h"
#include "gnunet_util_lib.h"
#include "gnunet_protocols.h"
#include "gnunet_applications.h"
#include "gnunet_set_service.h"
#include "gnunet_consensus_service.h"
#include "consensus_protocol.h"
#include "consensus.h"


/**
 * Log macro that prefixes the local peer and the peer we are in contact with.
 *
 * @param kind log level
 * @param cpi ConsensusPeerInformation of the partner peer
 * @param m log message
 */
#define LOG_PP(kind, cpi, m,...) GNUNET_log (kind, "P%d for P%d: " m, \
   cpi->session->local_peer_idx, (int) (cpi - cpi->session->info),##__VA_ARGS__)


/**
 * Number of exponential rounds, used in the exp and completion round.
 */
#define NUM_EXP_REPETITIONS 4


/* forward declarations */

/* mutual recursion with struct ConsensusSession */
struct ConsensusPeerInformation;

/* mutual recursion with round_over */
static void
subround_over (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc);


/**
 * Describes the current round a consensus session is in.
 */
enum ConsensusRound
{
  /**
   * Not started the protocol yet.
   */
  CONSENSUS_ROUND_BEGIN=0,
  /**
   * Distribution of elements with the exponential scheme.
   */
  CONSENSUS_ROUND_EXCHANGE,
  /**
   * Collect and distribute missing values.
   */
  CONSENSUS_ROUND_COMPLETION,
  /**
   * Consensus concluded. After timeout and finished communication with client,
   * consensus session will be destroyed.
   */
  CONSENSUS_ROUND_FINISH
};


/**
 * Information about the current round.
 */
struct RoundInfo
{
  /**
   * The current main round.
   */
  enum ConsensusRound round;
  /**
   * The current exp round repetition, valid if
   * the main round is an exp round.
   */
  uint32_t exp_repetition;
  /**
   * The current exp subround, valid if
   * the main round is an exp round.
   */
  uint32_t exp_subround;
};


/**
 * A consensus session consists of one local client and the remote authorities.
 */
struct ConsensusSession
{
  /**
   * Consensus sessions are kept in a DLL.
   */
  struct ConsensusSession *next;

  /**
   * Consensus sessions are kept in a DLL.
   */
  struct ConsensusSession *prev;

  /**
  * Global consensus identification, computed
  * from the session id and participating authorities.
  */
  struct GNUNET_HashCode global_id;

  /**
   * Client that inhabits the session
   */
  struct GNUNET_SERVER_Client *client;

  /**
   * Queued messages to the client.
   */
  struct GNUNET_MQ_Handle *client_mq;

  /**
   * Time when the conclusion of the consensus should begin.
   */
  struct GNUNET_TIME_Absolute conclude_start;

  /**
   * Timeout for all rounds together, single rounds will schedule a timeout task
   * with a fraction of the conclude timeout.
   * Only valid once the current round is not CONSENSUS_ROUND_BEGIN.
   */
  struct GNUNET_TIME_Absolute conclude_deadline;

  /**
   * Timeout task identifier for the current round or subround.
   */
  struct GNUNET_SCHEDULER_Task * round_timeout_tid;

  /**
   * Number of other peers in the consensus.
   */
  unsigned int num_peers;

  /**
   * Information about the other peers,
   * their state, etc.
   */
  struct ConsensusPeerInformation *info;

  /**
   * Index of the local peer in the peers array
   */
  unsigned int local_peer_idx;

  /**
   * Current round
   */
  enum ConsensusRound current_round;

  /**
   * Permutation of peers for the current round,
   */
  uint32_t *shuffle;

  /**
   * Inverse permutation of peers for the current round,
   */
  uint32_t *shuffle_inv;

  /**
   * Current round of the exponential scheme.
   */
  uint32_t exp_repetition;

  /**
   * Current sub-round of the exponential scheme.
   */
  uint32_t exp_subround;

  /**
   * The partner for the current exp-round.
   * The local peer will initiate the set reconciliation with the
   * outgoing peer.
   */
  struct ConsensusPeerInformation *partner_outgoing;

  /**
   * The partner for the current exp-round
   * The incoming peer will initiate the set reconciliation with
   * the incoming peer.
   */
  struct ConsensusPeerInformation *partner_incoming;

  /**
   * The consensus set of this session.
   */
  struct GNUNET_SET_Handle *element_set;

  /**
   * Listener for requests from other peers.
   * Uses the session's global id as app id.
   */
  struct GNUNET_SET_ListenHandle *set_listener;
};


/**
 * Information about a peer that is in a consensus session.
 */
struct ConsensusPeerInformation
{
  /**
   * Peer identitty of the peer in the consensus session
   */
  struct GNUNET_PeerIdentity peer_id;

  /**
   * Back-reference to the consensus session,
   * to that ConsensusPeerInformation can be used as a closure
   */
  struct ConsensusSession *session;

  /**
   * Have we finished the set operation for this (sub-)round?
   */
  int set_op_finished;

  /**
   * Set operation we are currently executing with this peer.
   */
  struct GNUNET_SET_OperationHandle *set_op;

  /**
   * Set operation we are planning on executing with this peer.
   */
  struct GNUNET_SET_OperationHandle *delayed_set_op;

  /**
   * Info about the round of the delayed set operation.
   */
  struct RoundInfo delayed_round_info;
};


/**
 * Linked list of sessions this peer participates in.
 */
static struct ConsensusSession *sessions_head;

/**
 * Linked list of sessions this peer participates in.
 */
static struct ConsensusSession *sessions_tail;

/**
 * Configuration of the consensus service.
 */
static const struct GNUNET_CONFIGURATION_Handle *cfg;

/**
 * Handle to the server for this service.
 */
static struct GNUNET_SERVER_Handle *srv;

/**
 * Peer that runs this service.
 */
static struct GNUNET_PeerIdentity my_peer;


/**
 * Check if the current subround has finished.
 * Must only be called when an exp-round is the current round.
 *
 * @param session session to check for exp-round completion
 * @return GNUNET_YES if the subround has finished,
 *         GNUNET_NO if not
 */
static int
have_exp_subround_finished (const struct ConsensusSession *session)
{
  int not_finished;

  GNUNET_assert (CONSENSUS_ROUND_EXCHANGE == session->current_round);

  not_finished = 0;
  if ( (NULL != session->partner_outgoing) &&
       (GNUNET_NO == session->partner_outgoing->set_op_finished) )
    not_finished++;
  if ( (NULL != session->partner_incoming) &&
       (GNUNET_NO == session->partner_incoming->set_op_finished) )
    not_finished++;
  if (0 == not_finished)
    return GNUNET_YES;
  return GNUNET_NO;
}


/**
 * Destroy a session, free all resources associated with it.
 *
 * @param session the session to destroy
 */
static void
destroy_session (struct ConsensusSession *session)
{
  int i;

  GNUNET_CONTAINER_DLL_remove (sessions_head, sessions_tail, session);
  if (NULL != session->element_set)
  {
    GNUNET_SET_destroy (session->element_set);
    session->element_set = NULL;
  }
  if (NULL != session->set_listener)
  {
    GNUNET_SET_listen_cancel (session->set_listener);
    session->set_listener = NULL;
  }
  if (NULL != session->client_mq)
  {
    GNUNET_MQ_destroy (session->client_mq);
    session->client_mq = NULL;
  }
  if (NULL != session->client)
  {
    GNUNET_SERVER_client_disconnect (session->client);
    session->client = NULL;
  }
  if (NULL != session->shuffle)
  {
    GNUNET_free (session->shuffle);
    session->shuffle = NULL;
  }
  if (NULL != session->shuffle_inv)
  {
    GNUNET_free (session->shuffle_inv);
    session->shuffle_inv = NULL;
  }
  if (NULL != session->info)
  {
    for (i = 0; i < session->num_peers; i++)
    {
      struct ConsensusPeerInformation *cpi;
      cpi = &session->info[i];
      if (NULL != cpi->set_op)
      {
        GNUNET_SET_operation_cancel (cpi->set_op);
        cpi->set_op = NULL;
      }
    }
    GNUNET_free (session->info);
    session->info = NULL;
  }
  GNUNET_free (session);
}


/**
 * Iterator for set elements. [FIXME: bad comment]
 *
 * @param cls closure
 * @param element the current element, NULL if all elements have been
 *        iterated over
 * @return #GNUNET_YES to continue iterating, #GNUNET_NO to stop.
 */
static int
send_to_client_iter (void *cls,
                     const struct GNUNET_SET_Element *element)
{
  struct ConsensusSession *session = cls;
  struct GNUNET_MQ_Envelope *ev;

  if (NULL != element)
  {
    struct GNUNET_CONSENSUS_ElementMessage *m;

    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "P%d: got element for client\n",
                session->local_peer_idx);

    ev = GNUNET_MQ_msg_extra (m, element->size,
                              GNUNET_MESSAGE_TYPE_CONSENSUS_CLIENT_RECEIVED_ELEMENT);
    m->element_type = htons (element->element_type);
    memcpy (&m[1], element->data, element->size);
    GNUNET_MQ_send (session->client_mq, ev);
  }
  else
  {
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
                "P%d: finished iterating elements for client\n",
                session->local_peer_idx);
    ev = GNUNET_MQ_msg_header (GNUNET_MESSAGE_TYPE_CONSENSUS_CLIENT_CONCLUDE_DONE);
    GNUNET_MQ_send (session->client_mq, ev);
  }
  return GNUNET_YES;
}


/**
 * Start the next round.
 * This function can be invoked as a timeout task, or called manually (tc will be NULL then).
 *
 * @param cls the session
 * @param tc task context, for when this task is invoked by the scheduler,
 *           NULL if invoked for another reason
 */
static void
round_over (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
{
  struct ConsensusSession *session;
  unsigned int i;
  int res;

  /* don't kick off next round if we're shutting down */
  if ((NULL != tc) && (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN))
    return;

  session = cls;
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%d: round over\n", session->local_peer_idx);

  if (tc != NULL)
    session->round_timeout_tid = NULL;

  if (session->round_timeout_tid != NULL)
  {
    GNUNET_SCHEDULER_cancel (session->round_timeout_tid);
    session->round_timeout_tid = NULL;
  }

  for (i = 0; i < session->num_peers; i++)
  {
    if (NULL != session->info[i].set_op)
    {
      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%d: canceling stray op with P%d\n",
                  session->local_peer_idx, i);
      GNUNET_SET_operation_cancel (session->info[i].set_op);
      session->info[i].set_op = NULL;
    }
    /* we're in the new round, nothing finished yet */
    session->info[i].set_op_finished = GNUNET_NO;
  }

  switch (session->current_round)
  {
    case CONSENSUS_ROUND_BEGIN:
      session->current_round = CONSENSUS_ROUND_EXCHANGE;
      session->exp_repetition = 0;
      subround_over (session, NULL);
      break;
    case CONSENSUS_ROUND_EXCHANGE:
      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%d: finished, sending elements to client\n",
                  session->local_peer_idx);
      session->current_round = CONSENSUS_ROUND_FINISH;
      res = GNUNET_SET_iterate (session->element_set, send_to_client_iter, session);
      if (GNUNET_SYSERR == res)
      {
        GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "can't iterate set: set invalid\n");
      }
      else if (GNUNET_NO == res)
      {
        GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "can't iterate set: iterator already active\n");
      }
      break;
    default:
      GNUNET_assert (0);
  }
}


/**
 * Create a new permutation for the session's peers in session->shuffle.
 * Uses a Fisher-Yates shuffle with pseudo-randomness coming from
 * both the global session id and the current round index.
 *
 * @param session the session to create the new permutation for
 */
static void
shuffle (struct ConsensusSession *session)
{
  uint32_t i;
  uint32_t randomness[session->num_peers-1];

  if (NULL == session->shuffle)
    session->shuffle = GNUNET_malloc (session->num_peers * sizeof (*session->shuffle));
  if (NULL == session->shuffle_inv)
    session->shuffle_inv = GNUNET_malloc (session->num_peers * sizeof (*session->shuffle_inv));

  GNUNET_CRYPTO_kdf (randomness, sizeof (randomness),
		     &session->exp_repetition, sizeof (uint32_t),
                     &session->global_id, sizeof (struct GNUNET_HashCode),
		     NULL);

  for (i = 0; i < session->num_peers; i++)
    session->shuffle[i] = i;

  for (i = session->num_peers - 1; i > 0; i--)
  {
    uint32_t x;
    uint32_t tmp;
    x = randomness[i-1] % session->num_peers;
    tmp = session->shuffle[x];
    session->shuffle[x] = session->shuffle[i];
    session->shuffle[i] = tmp;
  }

  /* create the inverse */
  for (i = 0; i < session->num_peers; i++)
    session->shuffle_inv[session->shuffle[i]] = i;
}


/**
 * Find and set the partner_incoming and partner_outgoing of our peer,
 * one of them may not exist (and thus set to NULL) if the number of peers
 * in the session is not a power of two.
 *
 * @param session the consensus session
 */
static void
find_partners (struct ConsensusSession *session)
{
  unsigned int arc;
  unsigned int num_ghosts;
  unsigned int largest_arc;
  int partner_idx;

  /* shuffled local index */
  int my_idx = session->shuffle[session->local_peer_idx];

  /* distance to neighboring peer in current subround */
  arc = 1 << session->exp_subround;
  largest_arc = 1;
  while (largest_arc < session->num_peers)
    largest_arc <<= 1;
  num_ghosts = largest_arc - session->num_peers;
  // GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "largest arc: %u\n", largest_arc);
  // GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "arc: %u\n", arc);
  // GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "num ghosts: %u\n", num_ghosts);

  if (0 == (my_idx & arc))
  {
    /* we are outgoing */
    partner_idx = (my_idx + arc) % session->num_peers;
    session->partner_outgoing = &session->info[session->shuffle_inv[partner_idx]];
    GNUNET_assert (GNUNET_NO == session->partner_outgoing->set_op_finished);
    /* are we a 'ghost' of a peer that would exist if
     * the number of peers was a power of two, and thus have to partner
     * with an additional peer?
     */
    if (my_idx < num_ghosts)
    {
      int ghost_partner_idx;
      // GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "my index %d, arc %d, peers %u\n", my_idx, arc, session->num_peers);
      ghost_partner_idx = (my_idx - (int) arc) % (int) session->num_peers;
      /* platform dependent; modulo sometimes returns negative values */
      if (ghost_partner_idx < 0)
        ghost_partner_idx += session->num_peers;
      /* we only need to have a ghost partner if the partner is outgoing */
      if (0 == (ghost_partner_idx & arc))
      {
        // GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "ghost partner is %d\n", ghost_partner_idx);
        session->partner_incoming = &session->info[session->shuffle_inv[ghost_partner_idx]];
        GNUNET_assert (GNUNET_NO == session->partner_incoming->set_op_finished);
        return;
      }
    }
    session->partner_incoming = NULL;
    return;
  }
  /* we only have an incoming connection */
  partner_idx = (my_idx - (int) arc) % (int) session->num_peers;
  if (partner_idx < 0)
    partner_idx += session->num_peers;
  session->partner_outgoing = NULL;
  session->partner_incoming = &session->info[session->shuffle_inv[partner_idx]];
  GNUNET_assert (GNUNET_NO == session->partner_incoming->set_op_finished);
}


/**
 * Callback for set operation results. Called for each element
 * in the result set.
 *
 * @param cls closure
 * @param element a result element, only valid if status is GNUNET_SET_STATUS_OK
 * @param status see enum GNUNET_SET_Status
 */
static void
set_result_cb (void *cls,
               const struct GNUNET_SET_Element *element,
               enum GNUNET_SET_Status status)
{
  struct ConsensusPeerInformation *cpi = cls;
  unsigned int remote_idx = cpi - cpi->session->info;
  unsigned int local_idx = cpi->session->local_peer_idx;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: set result from P%u with status %u\n",
              local_idx, remote_idx, (unsigned int) status);

  GNUNET_assert ((cpi == cpi->session->partner_outgoing) ||
                 (cpi == cpi->session->partner_incoming));

  switch (status)
  {
    case GNUNET_SET_STATUS_OK:
      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: set result from P%u: element\n",
                  local_idx, remote_idx);
      break;
    case GNUNET_SET_STATUS_FAILURE:
      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: set result from P%u: failure\n",
                  local_idx, remote_idx);
      cpi->set_op = NULL;
      return;
    case GNUNET_SET_STATUS_HALF_DONE:
    case GNUNET_SET_STATUS_DONE:
      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: set result from P%u: done\n",
                  local_idx, remote_idx);
      cpi->set_op_finished = GNUNET_YES;
      cpi->set_op = NULL;
      if (have_exp_subround_finished (cpi->session) == GNUNET_YES)
      {
        GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: all reconciliations of subround done\n",
                    local_idx);
        subround_over (cpi->session, NULL);
      }
      else
      {
        GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: waiting for further set results\n",
                    local_idx);
      }
      return;
    default:
      GNUNET_break (0);
      return;
  }

  switch (cpi->session->current_round)
  {
    case CONSENSUS_ROUND_COMPLETION:
    case CONSENSUS_ROUND_EXCHANGE:
      GNUNET_SET_add_element (cpi->session->element_set, element, NULL, NULL);
      break;
    default:
      GNUNET_break (0);
      return;
  }
}


/**
 * Compare the round the session is in with the round of the given context message.
 *
 * @param session a consensus session
 * @param ri a round context message
 * @return 0 if it's the same round, -1 if the session is in an earlier round,
 *         1 if the session is in a later round
 */
static int
rounds_compare (struct ConsensusSession *session,
                struct RoundInfo* ri)
{
  if (session->current_round < ri->round)
    return -1;
  if (session->current_round > ri->round)
    return 1;
  if (session->current_round == CONSENSUS_ROUND_EXCHANGE)
  {
    if (session->exp_repetition < ri->exp_repetition)
      return -1;
    if (session->exp_repetition > ri->exp_repetition)
      return 1;
    if (session->exp_subround < ri->exp_subround)
      return -1;
    if (session->exp_subround > ri->exp_subround)
      return 1;
    return 0;
  }
  /* other rounds have no subrounds / repetitions to compare */
  return 0;
}


/**
 * Do the next subround in the exp-scheme.
 * This function can be invoked as a timeout task, or called manually (tc will be NULL then).
 *
 * @param cls the session
 * @param tc task context, for when this task is invoked by the scheduler,
 *           NULL if invoked for another reason
 */
static void
subround_over (void *cls, const struct GNUNET_SCHEDULER_TaskContext *tc)
{
  struct ConsensusSession *session;
  struct GNUNET_TIME_Relative subround_timeout;
  int i;

  /* don't kick off next subround if we're shutting down */
  if ((NULL != tc) && (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN))
    return;

  session = cls;

  GNUNET_assert (CONSENSUS_ROUND_EXCHANGE == session->current_round);

  if (tc != NULL)
  {
    session->round_timeout_tid = NULL;
    GNUNET_log (GNUNET_ERROR_TYPE_WARNING, "P%u: consensus subround timed out\n",
                session->local_peer_idx);
  }

  /* cancel timeout */
  if (session->round_timeout_tid != NULL)
  {
    GNUNET_SCHEDULER_cancel (session->round_timeout_tid);
    session->round_timeout_tid = NULL;
  }

  for (i = 0; i < session->num_peers; i++)
  {
    if (NULL != session->info[i].set_op)
    {
      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%d: canceling stray op with P%d\n",
                  session->local_peer_idx, i);
      GNUNET_SET_operation_cancel (session->info[i].set_op);
      session->info[i].set_op = NULL;
    }
    /* we're in the new round, nothing finished yet */
    session->info[i].set_op_finished = GNUNET_NO;
  }

  if (session->exp_repetition >= NUM_EXP_REPETITIONS)
  {
    round_over (session, NULL);
    return;
  }

  if (session->exp_repetition == 0)
  {
    /* initialize everything for the log-rounds */
    session->exp_repetition = 1;
    session->exp_subround = 0;
    if (NULL == session->shuffle)
      session->shuffle = GNUNET_malloc ((sizeof (int)) * session->num_peers);
    if (NULL == session->shuffle_inv)
      session->shuffle_inv = GNUNET_malloc ((sizeof (int)) * session->num_peers);
    for (i = 0; i < session->num_peers; i++)
      session->shuffle[i] = session->shuffle_inv[i] = i;
  }
  else if (session->exp_subround + 1 >= (int) ceil (log2 (session->num_peers)))
  {
    /* subrounds done, start new log-round */
    session->exp_repetition++;
    session->exp_subround = 0;
    shuffle (session);
  }
  else
  {
    session->exp_subround++;
  }

  subround_timeout =
      GNUNET_TIME_relative_divide (GNUNET_TIME_absolute_get_difference (session->conclude_start, session->conclude_deadline),
                                   2 * NUM_EXP_REPETITIONS * ((int) ceil (log2 (session->num_peers))));

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "subround timeout: %u ms\n", subround_timeout.rel_value_us / 1000);

  session->round_timeout_tid = GNUNET_SCHEDULER_add_delayed (subround_timeout, subround_over, session);

  /* determine the incoming and outgoing partner */
  find_partners (session);

  GNUNET_assert (session->partner_outgoing != &session->info[session->local_peer_idx]);
  GNUNET_assert (session->partner_incoming != &session->info[session->local_peer_idx]);

  /* initiate set operation with the outgoing partner */
  if (NULL != session->partner_outgoing)
  {
    struct GNUNET_CONSENSUS_RoundContextMessage *msg;
    msg = GNUNET_new (struct GNUNET_CONSENSUS_RoundContextMessage);
    msg->header.type = htons (GNUNET_MESSAGE_TYPE_CONSENSUS_P2P_ROUND_CONTEXT);
    msg->header.size = htons (sizeof *msg);
    msg->round = htonl (session->current_round);
    msg->exp_repetition = htonl (session->exp_repetition);
    msg->exp_subround = htonl (session->exp_subround);

    if (NULL != session->partner_outgoing->set_op)
    {
      GNUNET_break (0);
      GNUNET_SET_operation_cancel (session->partner_outgoing->set_op);
    }
    session->partner_outgoing->set_op =
        GNUNET_SET_prepare (&session->partner_outgoing->peer_id,
                            &session->global_id,
                            (struct GNUNET_MessageHeader *) msg,
                            GNUNET_SET_RESULT_ADDED,
                            set_result_cb, session->partner_outgoing);
    GNUNET_free (msg);
    if (GNUNET_OK != GNUNET_SET_commit (session->partner_outgoing->set_op, session->element_set))
    {
      GNUNET_break (0);
      session->partner_outgoing->set_op = NULL;
      session->partner_outgoing->set_op_finished = GNUNET_YES;
    }
  }

  /* commit to the delayed set operation */
  if ((NULL != session->partner_incoming) && (NULL != session->partner_incoming->delayed_set_op))
  {
    int cmp = rounds_compare (session, &session->partner_incoming->delayed_round_info);

    if (NULL != session->partner_incoming->set_op)
    {
      GNUNET_break (0);
      GNUNET_SET_operation_cancel (session->partner_incoming->set_op);
      session->partner_incoming->set_op = NULL;
    }
    if (cmp == 0)
    {
      if (GNUNET_OK != GNUNET_SET_commit (session->partner_incoming->delayed_set_op, session->element_set))
      {
        GNUNET_break (0);
      }
      session->partner_incoming->set_op = session->partner_incoming->delayed_set_op;
      session->partner_incoming->delayed_set_op = NULL;
      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%d resumed delayed round with P%d\n",
                  session->local_peer_idx, (int) (session->partner_incoming - session->info));
    }
    else
    {
      /* this should not happen -- a round has been skipped! */
      GNUNET_break_op (0);
    }
  }

#ifdef GNUNET_EXTRA_LOGGING
  {
    int in;
    int out;
    if (session->partner_outgoing == NULL)
      out = -1;
    else
      out = (int) (session->partner_outgoing - session->info);
    if (session->partner_incoming == NULL)
      in = -1;
    else
      in = (int) (session->partner_incoming - session->info);
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: doing exp-round, r=%d, sub=%d, in: %d, out: %d\n", session->local_peer_idx,
                session->exp_repetition, session->exp_subround, in, out);
  }
#endif /* GNUNET_EXTRA_LOGGING */

}


/**
 * Search peer in the list of peers in session.
 *
 * @param peer peer to find
 * @param session session with peer
 * @return index of peer, -1 if peer is not in session
 */
static int
get_peer_idx (const struct GNUNET_PeerIdentity *peer, const struct ConsensusSession *session)
{
  int i;
  for (i = 0; i < session->num_peers; i++)
    if (0 == memcmp (peer, &session->info[i].peer_id, sizeof *peer))
      return i;
  return -1;
}


/**
 * Compute a global, (hopefully) unique consensus session id,
 * from the local id of the consensus session, and the identities of all participants.
 * Thus, if the local id of two consensus sessions coincide, but are not comprised of
 * exactly the same peers, the global id will be different.
 *
 * @param session session to generate the global id for
 * @param session_id local id of the consensus session
 */
static void
compute_global_id (struct ConsensusSession *session,
		   const struct GNUNET_HashCode *session_id)
{
  int i;
  struct GNUNET_HashCode tmp;
  struct GNUNET_HashCode phash;

  /* FIXME: use kdf? */

  session->global_id = *session_id;
  for (i = 0; i < session->num_peers; ++i)
  {
    GNUNET_CRYPTO_hash (&session->info[i].peer_id, sizeof (struct GNUNET_PeerIdentity), &phash);
    GNUNET_CRYPTO_hash_xor (&session->global_id, &phash, &tmp);
    session->global_id = tmp;
    GNUNET_CRYPTO_hash (&session->global_id, sizeof (struct GNUNET_PeerIdentity), &tmp);
    session->global_id = tmp;
  }
}


/**
 * Compare two peer identities.
 *
 * @param h1 some peer identity
 * @param h2 some peer identity
 * @return 1 if h1 > h2, -1 if h1 < h2 and 0 if h1 == h2.
 */
static int
peer_id_cmp (const void *h1, const void *h2)
{
  return memcmp (h1, h2, sizeof (struct GNUNET_PeerIdentity));
}


/**
 * Create the sorted list of peers for the session,
 * add the local peer if not in the join message.
 */
static void
initialize_session_peer_list (struct ConsensusSession *session,
                              struct GNUNET_CONSENSUS_JoinMessage *join_msg)
{
  unsigned int local_peer_in_list;
  uint32_t listed_peers;
  const struct GNUNET_PeerIdentity *msg_peers;
  struct GNUNET_PeerIdentity *peers;
  unsigned int i;

  GNUNET_assert (NULL != join_msg);

  /* peers in the join message, may or may not include the local peer */
  listed_peers = ntohl (join_msg->num_peers);

  session->num_peers = listed_peers;

  msg_peers = (struct GNUNET_PeerIdentity *) &join_msg[1];

  local_peer_in_list = GNUNET_NO;
  for (i = 0; i < listed_peers; i++)
  {
    if (0 == memcmp (&msg_peers[i], &my_peer, sizeof (struct GNUNET_PeerIdentity)))
    {
      local_peer_in_list = GNUNET_YES;
      break;
    }
  }

  if (GNUNET_NO == local_peer_in_list)
    session->num_peers++;

  peers = GNUNET_malloc (session->num_peers * sizeof (struct GNUNET_PeerIdentity));

  if (GNUNET_NO == local_peer_in_list)
    peers[session->num_peers - 1] = my_peer;

  memcpy (peers, msg_peers, listed_peers * sizeof (struct GNUNET_PeerIdentity));
  qsort (peers, session->num_peers, sizeof (struct GNUNET_PeerIdentity), &peer_id_cmp);

  session->info = GNUNET_malloc (session->num_peers * sizeof (struct ConsensusPeerInformation));

  for (i = 0; i < session->num_peers; ++i)
  {
    /* initialize back-references, so consensus peer information can
     * be used as closure */
    session->info[i].session = session;
    session->info[i].peer_id = peers[i];
  }

  GNUNET_free (peers);
}


/**
 * Called when another peer wants to do a set operation with the
 * local peer.
 *
 * @param cls closure
 * @param other_peer the other peer
 * @param context_msg message with application specific information from
 *        the other peer
 * @param request request from the other peer, use GNUNET_SET_accept
 *        to accept it, otherwise the request will be refused
 *        Note that we don't use a return value here, as it is also
 *        necessary to specify the set we want to do the operation with,
 *        whith sometimes can be derived from the context message.
 *        Also necessary to specify the timeout.
 */
static void
set_listen_cb (void *cls,
               const struct GNUNET_PeerIdentity *other_peer,
               const struct GNUNET_MessageHeader *context_msg,
               struct GNUNET_SET_Request *request)
{
  struct ConsensusSession *session = cls;
  struct GNUNET_CONSENSUS_RoundContextMessage *msg = (struct GNUNET_CONSENSUS_RoundContextMessage *) context_msg;
  struct ConsensusPeerInformation *cpi;
  struct GNUNET_SET_OperationHandle *set_op;
  struct RoundInfo round_info;
  int index;
  int cmp;

  if (NULL == context_msg)
  {
    GNUNET_break_op (0);
    return;
  }

  index = get_peer_idx (other_peer, session);

  if (index < 0)
  {
    GNUNET_break_op (0);
    return;
  }

  round_info.round = ntohl (msg->round);
  round_info.exp_repetition = ntohl (msg->exp_repetition);
  round_info.exp_subround = ntohl (msg->exp_subround);

  cpi = &session->info[index];

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%d got set request from P%d\n", session->local_peer_idx, index);

  switch (session->current_round)
  {
    case CONSENSUS_ROUND_BEGIN:
      /* we're in the begin round, so requests for the exchange round may
       * come in, they will be delayed for now! */
    case CONSENSUS_ROUND_EXCHANGE:
      cmp = rounds_compare (session, &round_info);
      if (cmp > 0)
      {
        /* the other peer is too late */
        LOG_PP (GNUNET_ERROR_TYPE_DEBUG, cpi, "too late for the current round\n");
        return;
      }
      /* kill old request, if any. this is legal,
       * as the other peer would not make a new request if it would want to
       * complete the old one! */
      if (NULL != cpi->set_op)
      {
        LOG_PP (GNUNET_ERROR_TYPE_INFO, cpi, "got new request from same peer, canceling old one\n");
        GNUNET_SET_operation_cancel (cpi->set_op);
        cpi->set_op = NULL;
      }
      set_op = GNUNET_SET_accept (request, GNUNET_SET_RESULT_ADDED,
                                  set_result_cb, &session->info[index]);
      if (cmp == 0)
      {
        /* we're in exactly the right round for the incoming request */
        if (cpi != cpi->session->partner_incoming)
        {
          GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "P%u: got request from %u (with matching round), "
                      "but incoming partner is %d\n", cpi->session->local_peer_idx, cpi - cpi->session->info,
                      ((NULL == cpi->session->partner_incoming) ? -1 : (cpi->session->partner_incoming - cpi->session->info)));
          GNUNET_SET_operation_cancel (set_op);
          return;
        }
        cpi->set_op = set_op;
        if (GNUNET_OK != GNUNET_SET_commit (set_op, session->element_set))
        {
          GNUNET_break (0);
        }
        GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%d commited to set request from P%d\n", session->local_peer_idx, index);
      }
      else
      {
        /* we still have wait until we have finished the current round,
         * as the other peer's round is larger */
        cpi->delayed_set_op = set_op;
        cpi->delayed_round_info = round_info;
        /* The current setop is finished, as we canceled the current setop above. */
        cpi->set_op_finished = GNUNET_YES;
        GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%d delaying set request from P%d\n", session->local_peer_idx, index);
      }
      break;
    default:
      GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "P%d got unexpected set request in round %d from P%d\n",
                  session->local_peer_idx, session->current_round, index);
      GNUNET_break_op (0);
      return;
  }
}


/**
 * Initialize the session, continue receiving messages from the owning client
 *
 * @param session the session to initialize
 * @param join_msg the join message from the client
 */
static void
initialize_session (struct ConsensusSession *session,
                    struct GNUNET_CONSENSUS_JoinMessage *join_msg)
{
  struct ConsensusSession *other_session;

  initialize_session_peer_list (session, join_msg);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "session with %u peers\n", session->num_peers);
  compute_global_id (session, &join_msg->session_id);

  /* check if some local client already owns the session.
   * it is only legal to have a session with an existing global id
   * if all other sessions with this global id are finished.*/
  other_session = sessions_head;
  while (NULL != other_session)
  {
    if ((other_session != session) &&
        (0 == GNUNET_CRYPTO_hash_cmp (&session->global_id, &other_session->global_id)))
    {
      if (CONSENSUS_ROUND_FINISH != other_session->current_round)
      {
        GNUNET_break (0);
        destroy_session (session);
        return;
      }
      break;
    }
    other_session = other_session->next;
  }

  session->conclude_deadline = GNUNET_TIME_absolute_ntoh (join_msg->deadline);
  session->conclude_start = GNUNET_TIME_absolute_ntoh (join_msg->start);

  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "consensus with timeout %ums created\n",
              (GNUNET_TIME_absolute_get_difference (session->conclude_start, session->conclude_deadline)).rel_value_us / 1000);

  session->local_peer_idx = get_peer_idx (&my_peer, session);
  GNUNET_assert (-1 != session->local_peer_idx);
  session->element_set = GNUNET_SET_create (cfg, GNUNET_SET_OPERATION_UNION);
  GNUNET_assert (NULL != session->element_set);
  session->set_listener = GNUNET_SET_listen (cfg, GNUNET_SET_OPERATION_UNION,
                                             &session->global_id,
                                             set_listen_cb, session);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "%d is the local peer\n", session->local_peer_idx);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "session %s initialized\n", GNUNET_h2s (&session->global_id));
}


static struct ConsensusSession *
get_session_by_client (struct GNUNET_SERVER_Client *client)
{
  struct ConsensusSession *session;

  session = sessions_head;
  while (NULL != session)
  {
    if (session->client == client)
      return session;
    session = session->next;
  }
  return NULL;
}


/**
 * Called when a client wants to join a consensus session.
 *
 * @param cls unused
 * @param client client that sent the message
 * @param m message sent by the client
 */
static void
client_join (void *cls,
             struct GNUNET_SERVER_Client *client,
             const struct GNUNET_MessageHeader *m)
{
  struct ConsensusSession *session;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "join message sent by client\n");

  session = get_session_by_client (client);
  if (NULL != session)
  {
    GNUNET_break (0);
    GNUNET_SERVER_receive_done (client, GNUNET_SYSERR);
    return;
  }
  session = GNUNET_new (struct ConsensusSession);
  session->client = client;
  session->client_mq = GNUNET_MQ_queue_for_server_client (client);
  GNUNET_CONTAINER_DLL_insert (sessions_head, sessions_tail, session);
  initialize_session (session, (struct GNUNET_CONSENSUS_JoinMessage *) m);
  GNUNET_SERVER_receive_done (client, GNUNET_OK);

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "join done\n");
}


/**
 * Called when a client performs an insert operation.
 *
 * @param cls (unused)
 * @param client client handle
 * @param m message sent by the client
 */
void
client_insert (void *cls,
               struct GNUNET_SERVER_Client *client,
               const struct GNUNET_MessageHeader *m)
{
  struct ConsensusSession *session;
  struct GNUNET_CONSENSUS_ElementMessage *msg;
  struct GNUNET_SET_Element *element;
  ssize_t element_size;

  session = get_session_by_client (client);

  if (NULL == session)
  {
    GNUNET_break (0);
    GNUNET_SERVER_client_disconnect (client);
    return;
  }

  if (CONSENSUS_ROUND_BEGIN != session->current_round)
  {
    GNUNET_break (0);
    GNUNET_SERVER_client_disconnect (client);
    return;
  }

  msg = (struct GNUNET_CONSENSUS_ElementMessage *) m;
  element_size = ntohs (msg->header.size) - sizeof (struct GNUNET_CONSENSUS_ElementMessage);
  if (element_size < 0)
  {
    GNUNET_break (0);
    return;
  }

  element = GNUNET_malloc (sizeof (struct GNUNET_SET_Element) + element_size);
  element->element_type = msg->element_type;
  element->size = element_size;
  memcpy (&element[1], &msg[1], element_size);
  element->data = &element[1];
  GNUNET_SET_add_element (session->element_set, element, NULL, NULL);
  GNUNET_free (element);
  GNUNET_SERVER_receive_done (client, GNUNET_OK);

  // GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "P%u: element added\n", session->local_peer_idx);
}


/**
 * Called when a client performs the conclude operation.
 *
 * @param cls (unused)
 * @param client client handle
 * @param message message sent by the client
 */
static void
client_conclude (void *cls,
                 struct GNUNET_SERVER_Client *client,
                 const struct GNUNET_MessageHeader *message)
{
  struct ConsensusSession *session;

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "conclude requested\n");
  session = get_session_by_client (client);
  if (NULL == session)
  {
    /* client not found */
    GNUNET_break (0);
    GNUNET_SERVER_client_disconnect (client);
    return;
  }
  if (CONSENSUS_ROUND_BEGIN != session->current_round)
  {
    /* client requested conclude twice */
    GNUNET_break (0);
    return;
  }
  if (session->num_peers <= 1)
  {
    session->current_round = CONSENSUS_ROUND_FINISH;
    GNUNET_SET_iterate (session->element_set, send_to_client_iter, session);
  }
  else
  {
    /* the 'begin' round is over, start with the next, actual round */
    round_over (session, NULL);
  }

  GNUNET_assert (CONSENSUS_ROUND_BEGIN != session->current_round);
  GNUNET_SERVER_receive_done (client, GNUNET_OK);
}


/**
 * Called to clean up, after a shutdown has been requested.
 *
 * @param cls closure
 * @param tc context information (why was this task triggered now)
 */
static void
shutdown_task (void *cls,
               const struct GNUNET_SCHEDULER_TaskContext *tc)
{
  while (NULL != sessions_head)
    destroy_session (sessions_head);

  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "handled shutdown request\n");
}


/**
 * Clean up after a client after it is
 * disconnected (either by us or by itself)
 *
 * @param cls closure, unused
 * @param client the client to clean up after
 */
void
handle_client_disconnect (void *cls, struct GNUNET_SERVER_Client *client)
{
  struct ConsensusSession *session;

  session = get_session_by_client (client);
  if (NULL == session)
    return;
  if ((CONSENSUS_ROUND_BEGIN == session->current_round) ||
      (CONSENSUS_ROUND_FINISH == session->current_round))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "client disconnected, destroying session\n");
    destroy_session (session);
  }
  else
    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "client disconnected, but waiting for consensus to finish\n");
}


/**
 * Start processing consensus requests.
 *
 * @param cls closure
 * @param server the initialized server
 * @param c configuration to use
 */
static void
run (void *cls, struct GNUNET_SERVER_Handle *server,
     const struct GNUNET_CONFIGURATION_Handle *c)
{
  static const struct GNUNET_SERVER_MessageHandler server_handlers[] = {
    {&client_conclude, NULL, GNUNET_MESSAGE_TYPE_CONSENSUS_CLIENT_CONCLUDE,
        sizeof (struct GNUNET_MessageHeader)},
    {&client_insert, NULL, GNUNET_MESSAGE_TYPE_CONSENSUS_CLIENT_INSERT, 0},
    {&client_join, NULL, GNUNET_MESSAGE_TYPE_CONSENSUS_CLIENT_JOIN, 0},
    {NULL, NULL, 0, 0}
  };

  cfg = c;
  srv = server;
  if (GNUNET_OK != GNUNET_CRYPTO_get_peer_identity (cfg, &my_peer))
  {
    GNUNET_log (GNUNET_ERROR_TYPE_ERROR, "could not retrieve host identity\n");
    GNUNET_break (0);
    GNUNET_SCHEDULER_shutdown ();
    return;
  }
  GNUNET_SERVER_add_handlers (server, server_handlers);
  GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_FOREVER_REL, &shutdown_task, NULL);
  GNUNET_SERVER_disconnect_notify (server, handle_client_disconnect, NULL);
  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "consensus running\n");
}


/**
 * The main function for the consensus service.
 *
 * @param argc number of arguments from the command line
 * @param argv command line arguments
 * @return 0 ok, 1 on error
 */
int
main (int argc, char *const *argv)
{
  int ret;
  ret = GNUNET_SERVICE_run (argc, argv, "consensus", GNUNET_SERVICE_OPTION_NONE, &run, NULL);
  GNUNET_log (GNUNET_ERROR_TYPE_INFO, "exit (%d)\n", GNUNET_OK != ret);
  return (GNUNET_OK == ret) ? 0 : 1;
}