aboutsummaryrefslogtreecommitdiff
path: root/src/testbed/testbed_api_topology.c
blob: 8d8883c96420e7a92ecfa2b75a612f92277408d3 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
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
/*
      This file is part of GNUnet
      (C) 2008--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 testbed/testbed_api_topology.c
 * @brief topology-generation functions
 * @author Christian Grothoff
 */
#include "platform.h"
#include "gnunet_testbed_service.h"
#include "testbed_api.h"
#include "testbed_api_peers.h"
#include "testbed_api_operations.h"
#include "testbed_api_topology.h"

/**
 * Generic loggins shorthand
 */
#define LOG(kind,...)                                           \
  GNUNET_log_from (kind, "testbed-api-topology", __VA_ARGS__)


/**
 * Default number of retires
 */
#define DEFAULT_RETRY_CNT 3


/**
 * Context information for topology operations
 */
struct TopologyContext;


/**
 * Representation of an overlay link
 */
struct OverlayLink
{

  /**
   * An operation corresponding to this link
   */
  struct GNUNET_TESTBED_Operation *op;

  /**
   * The topology context this link is a part of
   */
  struct TopologyContext *tc;

  /**
   * position of peer A's handle in peers array
   */
  uint32_t A;

  /**
   * position of peer B's handle in peers array
   */
  uint32_t B;

};


struct RetryListEntry
{
  /**
   * the next pointer for the DLL
   */
  struct RetryListEntry *next;

  /**
   * the prev pointer for the DLL
   */
  struct RetryListEntry *prev;

  /**
   * The link to be retired
   */
  struct OverlayLink *link;
};


/**
 * Context information for topology operations
 */
struct TopologyContext
{
  /**
   * The array of peers
   */
  struct GNUNET_TESTBED_Peer **peers;

  /**
   * An array of links; this array is of size link_array_size
   */
  struct OverlayLink *link_array;

  /**
   * The operation closure
   */
  void *op_cls;

  /**
   * topology generation completion callback
   */
  GNUNET_TESTBED_TopologyCompletionCallback comp_cb;

  /**
   * The closure for the above callback
   */
  void *comp_cb_cls;

  /**
   * DLL head for retry list
   */
  struct RetryListEntry *rl_head;

  /**
   * DLL tail for retry list
   */
  struct RetryListEntry *rl_tail;

  /**
   * The number of peers
   */
  unsigned int num_peers;

  /**
   * The size of the link array
   */
  unsigned int link_array_size;

  /**
   * How many retries to do before we give up
   */
  unsigned int retry_cnt;

  /**
   * Number of links to try
   */
  unsigned int nlinks;

  /**
   * How many links have been completed
   */
  unsigned int ncompleted;

  /**
   * Total successfully established overlay connections
   */
  unsigned int nsuccess;

  /**
   * Total failed overlay connections
   */
  unsigned int nfailures;
};


/**
 * A array of names representing topologies. Should be in sync with enum
 * GNUNET_TESTBED_TopologyOption
 */
const char *topology_strings[] = {

    /**
     * A clique (everyone connected to everyone else).  No options. If there are N
     * peers this topology results in (N * (N -1)) connections.
     */
  "CLIQUE",

    /**
     * Small-world network (2d torus plus random links).  Followed
     * by the number of random links to add (unsigned int).
     */
  "SMALL_WORLD",

    /**
     * Small-world network (ring plus random links).  Followed
     * by the number of random links to add (unsigned int).
     */
  "SMALL_WORLD_RING",

    /**
     * Ring topology.  No options.
     */
  "RING",

    /**
     * 2-d torus.  No options.
     */
  "2D_TORUS",

    /**
     * Random graph.  Followed by the number of random links to be established
     * (unsigned int)
     */
  "RANDOM",                     // GNUNET_TESTBED_TOPOLOGY_ERDOS_RENYI

    /**
     * Certain percentage of peers are unable to communicate directly
     * replicating NAT conditions.  Followed by the fraction of
     * NAT'ed peers (float).
     */
  "INTERNAT",

    /**
     * Scale free topology. No options.
     */
  "SCALE_FREE",

    /**
     * Straight line topology.  No options.
     */
  "LINE",

    /**
     * Read a topology from a given file.  Followed by the name of the file (const char *).
     */
  "FROM_FILE",

    /**
     * All peers are disconnected.  No options.
     */
  "NONE",

    /**
     * End of strings
     */
  NULL
};


/**
 * Callback to be called when an overlay_link operation complete
 *
 * @param cls element of the link_op array which points to the corresponding operation
 * @param op the operation that has been finished
 * @param emsg error message in case the operation has failed; will be NULL if
 *          operation has executed successfully.
 */
static void
overlay_link_completed (void *cls, struct GNUNET_TESTBED_Operation *op,
                        const char *emsg)
{
  struct OverlayLink *link = cls;
  struct TopologyContext *tc;
  struct RetryListEntry *retry_entry;

  GNUNET_assert (op == link->op);
  GNUNET_TESTBED_operation_done (op);
  link->op = NULL;
  tc = link->tc;
  if (NULL != emsg)
  {
    tc->nfailures++;
    if (0 != tc->retry_cnt)
    {
      LOG (GNUNET_ERROR_TYPE_WARNING,
           "Error while establishing a link: %s -- Retrying\n", emsg);
      retry_entry = GNUNET_malloc (sizeof (struct RetryListEntry));
      retry_entry->link = link;
      GNUNET_CONTAINER_DLL_insert_tail (tc->rl_head, tc->rl_tail, retry_entry);
    }
  }
  else
    tc->nsuccess++;
  tc->ncompleted++;
  if (tc->ncompleted < tc->nlinks)
    return;
  if ((0 != tc->retry_cnt) && (NULL != tc->rl_head))
  {
    tc->retry_cnt--;
    tc->ncompleted = 0;
    tc->nlinks = 0;
    while (NULL != (retry_entry = tc->rl_head))
    {
      link = retry_entry->link;
      link->op =
          GNUNET_TESTBED_overlay_connect (tc->op_cls, &overlay_link_completed,
                                          link, tc->peers[link->A],
                                          tc->peers[link->B]);
      tc->nlinks++;
      GNUNET_CONTAINER_DLL_remove (tc->rl_head, tc->rl_tail, retry_entry);
      GNUNET_free (retry_entry);
    }
    return;
  }
  if (NULL != tc->comp_cb)
  {
    tc->comp_cb (tc->comp_cb_cls, tc->nsuccess, tc->nfailures);
  }
}



/**
 * Function called when a overlay connect operation is ready
 *
 * @param cls the Topology context
 */
static void
opstart_overlay_configure_topology (void *cls)
{
  struct TopologyContext *tc = cls;
  unsigned int p;

  tc->nlinks = tc->link_array_size;
  for (p = 0; p < tc->link_array_size; p++)
  {
    tc->link_array[p].op =
        GNUNET_TESTBED_overlay_connect (tc->op_cls, &overlay_link_completed,
                                        &tc->link_array[p],
                                        tc->peers[tc->link_array[p].A],
                                        tc->peers[tc->link_array[p].B]);
  }
}


/**
 * Callback which will be called when overlay connect operation is released
 *
 * @param cls the Topology context
 */
static void
oprelease_overlay_configure_topology (void *cls)
{
  struct TopologyContext *tc = cls;
  struct RetryListEntry *retry_entry;
  unsigned int p;

  while (NULL != (retry_entry = tc->rl_head))
  {
    GNUNET_CONTAINER_DLL_remove (tc->rl_head, tc->rl_tail, retry_entry);
    GNUNET_free (retry_entry);
  }
  if (NULL != tc->link_array)
  {
    for (p = 0; p < tc->link_array_size; p++)
      if (NULL != tc->link_array[p].op)
        GNUNET_TESTBED_operation_done (tc->link_array[p].op);
    GNUNET_free (tc->link_array);
  }
  GNUNET_free (tc);
}


/**
 * Populates the OverlayLink structure.
 *
 * @param link the OverlayLink
 * @param A the peer A. Should be different from B
 * @param B the peer B. Should be different from A
 * @param tc the TopologyContext
 * @return
 */
static void
make_link (struct OverlayLink *link, uint32_t A, uint32_t B,
           struct TopologyContext *tc)
{
  GNUNET_assert (A != B);
  LOG (GNUNET_ERROR_TYPE_DEBUG, "Connecting peer %u to %u\n", B, A);
  link->A = A;
  link->B = B;
  link->op = NULL;
  link->tc = tc;
}


/**
 * Generates line topology
 *
 * @param tc the topology context
 */
static void
gen_topo_line (struct TopologyContext *tc)
{
  unsigned int cnt;

  tc->link_array_size = tc->num_peers - 1;
  tc->link_array =
      GNUNET_malloc (sizeof (struct OverlayLink) * tc->link_array_size);
  for (cnt = 0; cnt < (tc->num_peers - 1); cnt++)
    make_link (&tc->link_array[cnt], cnt, cnt + 1, tc);
}


/**
 * Generates ring topology
 *
 * @param tc the topology context
 */
static void
gen_topo_ring (struct TopologyContext *tc)
{
  gen_topo_line (tc);
  tc->link_array_size++;
  tc->link_array =
      GNUNET_realloc (tc->link_array,
                      sizeof (struct OverlayLink) * tc->link_array_size);
  make_link (&tc->link_array[tc->link_array_size - 1], tc->num_peers - 1, 0,
             tc);
}


/**
 * Returns the number of links that are required to generate a 2d torus for the
 * given number of peers. Also returns the arrangment (number of rows and the
 * length of each row)
 *
 * @param num_peers number of peers
 * @param rows number of rows in the 2d torus. Can be NULL
 * @param rows_len the length of each row. This array will be allocated
 *          fresh. The caller should free it. Can be NULL
 * @return the number of links that are required to generate a 2d torus for the
 *           given number of peers
 */
unsigned int
GNUNET_TESTBED_2dtorus_calc_links (unsigned int num_peers, unsigned int *rows,
                                   unsigned int **rows_len)
{
  double sq;
  unsigned int sq_floor;
  unsigned int _rows;
  unsigned int *_rows_len;
  unsigned int x;
  unsigned int y;
  unsigned int _num_peers;
  unsigned int cnt;

  sq = sqrt (num_peers);
  sq = floor (sq);
  sq_floor = (unsigned int) sq;
  _rows = (sq_floor + 1);
  _rows_len = GNUNET_malloc (sizeof (unsigned int) * _rows);
  for (y = 0; y < _rows - 1; y++)
    _rows_len[y] = sq_floor;
  _num_peers = sq_floor * sq_floor;
  cnt = (_num_peers < 2) ? _num_peers : 2 * _num_peers;
  x = 0;
  y = 0;
  while (_num_peers < num_peers)
  {
    if (x < y)
      _rows_len[_rows - 1] = ++x;
    else
      _rows_len[y++]++;
    _num_peers++;
  }
  cnt += (x < 2) ? x : 2 * x;
  cnt += (y < 2) ? y : 2 * y;
  if (0 == _rows_len[_rows - 1])
    _rows--;
  if (NULL != rows)
    *rows = _rows;
  if (NULL != rows_len)
    *rows_len = _rows_len;
  else
    GNUNET_free (_rows_len);
  return cnt;
}


/**
 * Generates ring topology
 *
 * @param tc the topology context
 */
static void
gen_topo_2dtorus (struct TopologyContext *tc)
{
  unsigned int rows;
  unsigned int *rows_len;
  unsigned int x;
  unsigned int y;
  unsigned int cnt;
  unsigned int offset;

  tc->link_array_size =
      GNUNET_TESTBED_2dtorus_calc_links (tc->num_peers, &rows, &rows_len);
  tc->link_array =
      GNUNET_malloc (sizeof (struct OverlayLink) * tc->link_array_size);
  cnt = 0;
  offset = 0;
  for (y = 0; y < rows; y++)
  {
    for (x = 0; x < rows_len[y] - 1; x++)
    {
      make_link (&tc->link_array[cnt], offset + x, offset + x + 1, tc);
      cnt++;
    }
    if (0 == x)
      break;
    make_link (&tc->link_array[cnt], offset + x, offset, tc);
    cnt++;
    offset += rows_len[y];
  }
  for (x = 0; x < rows_len[0]; x++)
  {
    offset = 0;
    for (y = 0; y < rows - 1; y++)
    {
      if (x >= rows_len[y + 1])
        break;
      GNUNET_assert (x < rows_len[y + 1]);
      make_link (&tc->link_array[cnt], offset + x, offset + rows_len[y] + x,
                 tc);
      offset += rows_len[y];
      cnt++;
    }
    if (0 == offset)
      break;
    make_link (&tc->link_array[cnt], offset + x, x, tc);
    cnt++;
  }
  GNUNET_assert (cnt == tc->link_array_size);
  GNUNET_free (rows_len);
}


/**
 * Generates ring topology
 *
 * @param tc the topology context
 * @param links the number of random links to establish
 * @param append GNUNET_YES to add links to existing link array; GNUNET_NO to
 *          create a new link array
 */
static void
gen_topo_random (struct TopologyContext *tc, unsigned int links, int append)
{
  unsigned int cnt;
  unsigned int index;
  uint32_t A_rand;
  uint32_t B_rand;

  if (GNUNET_YES == append)
  {
    GNUNET_assert ((0 < tc->link_array_size) && (NULL != tc->link_array));
    index = tc->link_array_size;
    tc->link_array_size += links;
    tc->link_array =
        GNUNET_realloc (tc->link_array,
                        sizeof (struct OverlayLink) * tc->link_array_size);
  }
  else
  {
    GNUNET_assert ((0 == tc->link_array_size) && (NULL == tc->link_array));
    index = 0;
    tc->link_array_size = links;
    tc->link_array =
        GNUNET_malloc (sizeof (struct OverlayLink) * tc->link_array_size);
  }
  for (cnt = 0; cnt < links; cnt++)
  {
    do
    {
      A_rand =
          GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK, tc->num_peers);
      B_rand =
          GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK, tc->num_peers);
    }
    while (A_rand == B_rand);
    make_link (&tc->link_array[index + cnt], A_rand, B_rand, tc);
  }
}


/**
 * Generates scale free network. Its construction is described in:
 *
 * "Emergence of Scaling in Random Networks." Science 286, 509-512, 1999.
 *
 * @param tc the topology context
 * @param cap maximum allowed node degree
 * @param m number of edges to establish for a new node when it is added to the
 *   network
 */
static void
gen_scale_free (struct TopologyContext *tc, uint16_t cap, uint8_t m)
{
  unsigned int *deg;
  unsigned int *etab;
  unsigned int *used;
  unsigned int etaboff;
  unsigned int cnt;
  unsigned int cnt2;
  unsigned int peer;
  unsigned int random_peer;
  unsigned int links;
  unsigned int off;
  unsigned int redo_threshold;

  etaboff = 0;
  tc->link_array_size = tc->num_peers * m;
  tc->link_array = GNUNET_malloc_large (sizeof (struct OverlayLink) *
                                        tc->link_array_size);
  etab = GNUNET_malloc_large (sizeof (unsigned int) * 2 * tc->link_array_size);
  deg = GNUNET_malloc (sizeof (unsigned int) * tc->num_peers);
  used = GNUNET_malloc (sizeof (unsigned int) * m);
  /* start by connecting peer 1 to peer 0 */
  make_link (&tc->link_array[0], 0, 1, tc);
  deg[0]++;
  deg[1]++;
  etab[etaboff++] = 0;
  etab[etaboff++] = 1;
  links = 1;
  for (peer = 2; peer < tc->num_peers; peer++)
  {
    if (cap < deg[peer])
      continue;
    for (cnt = 0; cnt < GNUNET_MIN (peer, m); cnt++)
    {
      redo_threshold = 0;
    redo:
      off = GNUNET_CRYPTO_random_u64 (GNUNET_CRYPTO_QUALITY_WEAK, etaboff);
      random_peer = etab[off];
      if (cap < deg[random_peer])
      {
        if (++redo_threshold > GNUNET_MAX (1, cap / 2))
        {
          redo_threshold = 0;
          off = 0;
          for (cnt2 = 0; cnt2 < etaboff; cnt2++)
          {
            if (random_peer == etab[cnt2])
            {
              off++;
              continue;
            }
            etab[cnt2 - off] = etab[cnt2];
          }
          etaboff -= off;
        }
        goto redo;
      }
      for (cnt2 = 0; cnt2 < cnt; cnt2++)
        if (random_peer == used[cnt2])
          goto redo;
      make_link (&tc->link_array[links + cnt], random_peer, peer, tc);
      deg[random_peer]++;
      deg[peer]++;
      used[cnt] = random_peer;
    }
    for (cnt = 0; cnt < GNUNET_MIN (peer, m); cnt++)
    {
      etab[etaboff++] = used[cnt];
      etab[etaboff++] = peer;
    }
    links += GNUNET_MIN (peer, m);
  }
  GNUNET_free (etab);
  GNUNET_free (used);
  GNUNET_free (deg);
  GNUNET_assert (links <= tc->link_array_size);
  tc->link_array_size = links;
  tc->link_array =
      GNUNET_realloc (tc->link_array,
                      sizeof (struct OverlayLink) * tc->link_array_size);
}


/**
 * Generates topology from the given file
 *
 * @param tc the topology context
 * @param filename the filename of the file containing topology data
 */
static void
gen_topo_from_file (struct TopologyContext *tc, const char *filename)
{
  char *data;
  char *end;
  char *buf;
  uint64_t fs;
  uint64_t offset;
  unsigned long int peer_id;
  unsigned long int other_peer_id;
  enum ParseState
  {

    /**
     * We read the peer index
     */
    PEER_INDEX,

    /**
     * We read the other peer indices
     */
    OTHER_PEER_INDEX,

  } state;
  int status;

  status = GNUNET_SYSERR;
  if (GNUNET_YES != GNUNET_DISK_file_test (filename))
  {
    LOG (GNUNET_ERROR_TYPE_ERROR, _("Topology file %s not found\n"), filename);
    return;
  }
  if (GNUNET_OK !=
      GNUNET_DISK_file_size (filename, &fs, GNUNET_YES, GNUNET_YES))
  {
    LOG (GNUNET_ERROR_TYPE_ERROR, _("Topology file %s has no data\n"),
         filename);
    return;
  }
  data = GNUNET_malloc (fs);
  if (fs != GNUNET_DISK_fn_read (filename, data, fs))
  {
    LOG (GNUNET_ERROR_TYPE_ERROR, _("Topology file %s cannot be read\n"),
         filename);
    goto _exit;
  }

  offset = 0;
  peer_id = 0;
  state = PEER_INDEX;
  while (offset < fs)
  {
    if (0 != isspace (data[offset]))
    {
      offset++;
      continue;
    }
    switch (state)
    {
    case PEER_INDEX:
      buf = strchr (&data[offset], ':');
      if (NULL == buf)
      {
        LOG (GNUNET_ERROR_TYPE_ERROR,
             _("Failed to read peer index from toology file: %s"), filename);
        goto _exit;
      }
      *buf = '\0';
      errno = 0;
      peer_id = (unsigned int) strtoul (&data[offset], &end, 10);
      if (0 != errno)
      {
        LOG (GNUNET_ERROR_TYPE_ERROR,
             _("Value in given topology file: %s out of range\n"), filename);
        goto _exit;
      }
      if (&data[offset] == end)
      {
        LOG (GNUNET_ERROR_TYPE_ERROR,
             _("Failed to read peer index from topology file: %s"), filename);
        goto _exit;
      }
      if (tc->num_peers <= peer_id)
      {
        LOG (GNUNET_ERROR_TYPE_ERROR,
             _("Topology file needs more peers than given ones\n"), filename);
        goto _exit;
      }
      state = OTHER_PEER_INDEX;
      offset += ((unsigned int) (buf - &data[offset])) + 1;
      break;
    case OTHER_PEER_INDEX:
      errno = 0;
      other_peer_id = (unsigned int) strtoul (&data[offset], &end, 10);
      if (0 != errno)
      {
        LOG (GNUNET_ERROR_TYPE_ERROR,
             _("Value in given topology file: %s out of range\n"), filename);
        goto _exit;
      }
      if (&data[offset] == end)
      {
        LOG (GNUNET_ERROR_TYPE_ERROR,
             _("Failed to read peer index from topology file: %s"), filename);
        goto _exit;
      }
      if (tc->num_peers <= other_peer_id)
      {
        LOG (GNUNET_ERROR_TYPE_ERROR,
             _("Topology file needs more peers than given ones\n"), filename);
        goto _exit;
      }
      if (peer_id != other_peer_id)
      {
        tc->link_array_size++;
        tc->link_array =
            GNUNET_realloc (tc->link_array,
                            sizeof (struct OverlayLink) * tc->link_array_size);
        offset += end - &data[offset];
        make_link (&tc->link_array[tc->link_array_size - 1], peer_id,
                   other_peer_id, tc);
      }
      else
        LOG (GNUNET_ERROR_TYPE_WARNING,
             _("Ignoring to connect peer %u to peer %u\n"), peer_id,
             other_peer_id);
      while (('\n' != data[offset]) && ('|' != data[offset]) && (offset < fs))
        offset++;
      if ('\n' == data[offset])
        state = PEER_INDEX;
      else if ('|' == data[offset])
      {
        state = OTHER_PEER_INDEX;
        offset++;
      }
      break;
    }
  }
  status = GNUNET_OK;

_exit:
  GNUNET_free (data);
  if (GNUNET_OK != status)
  {
    LOG (GNUNET_ERROR_TYPE_WARNING, "Removing link data read from the file\n");
    tc->link_array_size = 0;
    GNUNET_free_non_null (tc->link_array);
    tc->link_array = NULL;
  }
}


/**
 * Configure overall network topology to have a particular shape.
 *
 * @param op_cls closure argument to give with the operation event
 * @param num_peers number of peers in 'peers'
 * @param peers array of 'num_peers' with the peers to configure
 * @param topo desired underlay topology to use
 * @param ap topology-specific options
 * @return handle to the operation, NULL if configuring the topology
 *         is not allowed at this time
 */
struct GNUNET_TESTBED_Operation *
GNUNET_TESTBED_underlay_configure_topology_va (void *op_cls,
                                               unsigned int num_peers,
                                               struct GNUNET_TESTBED_Peer
                                               **peers,
                                               enum
                                               GNUNET_TESTBED_TopologyOption
                                               topo, va_list ap)
{
  GNUNET_break (0);
  return NULL;
}


/**
 * Configure overall network topology to have a particular shape.
 *
 * @param op_cls closure argument to give with the operation event
 * @param num_peers number of peers in 'peers'
 * @param peers array of 'num_peers' with the peers to configure
 * @param topo desired underlay topology to use
 * @param ... topology-specific options
 * @return handle to the operation, NULL if configuring the topology
 *         is not allowed at this time
 */
struct GNUNET_TESTBED_Operation *
GNUNET_TESTBED_underlay_configure_topology (void *op_cls,
                                            unsigned int num_peers,
                                            struct GNUNET_TESTBED_Peer **peers,
                                            enum GNUNET_TESTBED_TopologyOption
                                            topo, ...)
{
  GNUNET_break (0);
  return NULL;
}


/**
 * All peers must have been started before calling this function.
 * This function then connects the given peers in the P2P overlay
 * using the given topology.
 *
 * @param op_cls closure argument to give with the peer connect operation events
 *          generated through this function
 * @param num_peers number of peers in 'peers'
 * @param peers array of 'num_peers' with the peers to configure
 * @param max_connections the maximums number of overlay connections that will
 *          be made to achieve the given topology
 * @param comp_cb the completion callback to call when the topology generation
 *          is completed
 * @param comp_cb_cls closure for the above completion callback
 * @param topo desired underlay topology to use
 * @param va topology-specific options
 * @return handle to the operation, NULL if connecting these
 *         peers is fundamentally not possible at this time (peers
 *         not running or underlay disallows) or if num_peers is less than 2
 */
struct GNUNET_TESTBED_Operation *
GNUNET_TESTBED_overlay_configure_topology_va (void *op_cls,
                                              unsigned int num_peers,
                                              struct GNUNET_TESTBED_Peer **peers,
                                              unsigned int *max_connections,
                                              GNUNET_TESTBED_TopologyCompletionCallback
                                              comp_cb,
                                              void *comp_cb_cls,
                                              enum GNUNET_TESTBED_TopologyOption topo,
                                              va_list va)
{
  struct TopologyContext *tc;
  struct GNUNET_TESTBED_Operation *op;
  struct GNUNET_TESTBED_Controller *c;
  enum GNUNET_TESTBED_TopologyOption secondary_option;
  unsigned int cnt;

  if (num_peers < 2)
    return NULL;
  c = peers[0]->controller;
  tc = GNUNET_malloc (sizeof (struct TopologyContext));
  tc->peers = peers;
  tc->num_peers = num_peers;
  tc->op_cls = op_cls;
  tc->retry_cnt = DEFAULT_RETRY_CNT;
  tc->comp_cb = comp_cb;
  tc->comp_cb_cls = comp_cb_cls;
  switch (topo)
  {
  case GNUNET_TESTBED_TOPOLOGY_LINE:
    gen_topo_line (tc);
    break;
  case GNUNET_TESTBED_TOPOLOGY_RING:
    gen_topo_ring (tc);
    break;
  case GNUNET_TESTBED_TOPOLOGY_ERDOS_RENYI:
    gen_topo_random (tc, va_arg (va, unsigned int), GNUNET_NO);
    break;
  case GNUNET_TESTBED_TOPOLOGY_SMALL_WORLD_RING:
    gen_topo_ring (tc);
    gen_topo_random (tc, va_arg (va, unsigned int), GNUNET_YES);
    break;
  case GNUNET_TESTBED_TOPOLOGY_CLIQUE:
    tc->link_array_size = num_peers * (num_peers - 1);
    tc->link_array =
        GNUNET_malloc (sizeof (struct OverlayLink) * tc->link_array_size);
    {
      unsigned int offset;

      offset = 0;
      for (cnt = 0; cnt < num_peers; cnt++)
      {
        unsigned int neighbour;

        for (neighbour = 0; neighbour < num_peers; neighbour++)
        {
          if (neighbour == cnt)
            continue;
          tc->link_array[offset].A = cnt;
          tc->link_array[offset].B = neighbour;
          tc->link_array[offset].tc = tc;
          offset++;
        }
      }
    }
    break;
  case GNUNET_TESTBED_TOPOLOGY_2D_TORUS:
    gen_topo_2dtorus (tc);
    break;
  case GNUNET_TESTBED_TOPOLOGY_SMALL_WORLD:
    gen_topo_2dtorus (tc);
    gen_topo_random (tc, va_arg (va, unsigned int), GNUNET_YES);

    break;
  case GNUNET_TESTBED_TOPOLOGY_SCALE_FREE:
    {
      uint16_t cap;
      uint8_t m;

      cap = (uint16_t) va_arg (va, unsigned int);
      m = (uint8_t) va_arg (va, unsigned int);
      gen_scale_free (tc, cap, m);
    }
    break;
  case GNUNET_TESTBED_TOPOLOGY_FROM_FILE:
  {
    const char *filename;

    filename = va_arg (va, const char *);

    GNUNET_assert (NULL != filename);
    gen_topo_from_file (tc, filename);
  }
    break;
  default:
    GNUNET_break (0);
    GNUNET_free (tc);
    return NULL;
  }
  do
  {
    secondary_option = va_arg (va, enum GNUNET_TESTBED_TopologyOption);

    switch (secondary_option)
    {
    case GNUNET_TESTBED_TOPOLOGY_RETRY_CNT:
      tc->retry_cnt =  va_arg (va, unsigned int);
      break;
    case GNUNET_TESTBED_TOPOLOGY_OPTION_END:
      break;
    default:
      GNUNET_break (0);         /* Should not use any other option apart from
                                 * the ones handled here */
      GNUNET_free_non_null (tc->link_array);
      GNUNET_free (tc);
      return NULL;
    }
  }
  while (GNUNET_TESTBED_TOPOLOGY_OPTION_END != secondary_option);
  op = GNUNET_TESTBED_operation_create_ (tc,
                                         &opstart_overlay_configure_topology,
                                         &oprelease_overlay_configure_topology);
  GNUNET_TESTBED_operation_queue_insert_
      (c->opq_parallel_topology_config_operations, op);
  GNUNET_TESTBED_operation_begin_wait_ (op);
  LOG (GNUNET_ERROR_TYPE_DEBUG, "Generated %u connections\n",
       tc->link_array_size);
  if (NULL != max_connections)
    *max_connections = tc->link_array_size;
  return op;
}


/**
 * All peers must have been started before calling this function.
 * This function then connects the given peers in the P2P overlay
 * using the given topology.
 *
 * @param op_cls closure argument to give with the peer connect operation events
 *          generated through this function
 * @param num_peers number of peers in 'peers'
 * @param peers array of 'num_peers' with the peers to configure
 * @param max_connections the maximums number of overlay connections that will
 *          be made to achieve the given topology
 * @param comp_cb the completion callback to call when the topology generation
 *          is completed
 * @param comp_cb_cls closure for the above completion callback
 * @param topo desired underlay topology to use
 * @param ... topology-specific options
 * @return handle to the operation, NULL if connecting these
 *         peers is fundamentally not possible at this time (peers
 *         not running or underlay disallows) or if num_peers is less than 2
 */
struct GNUNET_TESTBED_Operation *
GNUNET_TESTBED_overlay_configure_topology (void *op_cls,
                                           unsigned int num_peers,
                                           struct GNUNET_TESTBED_Peer **peers,
                                           unsigned int *max_connections,
                                           GNUNET_TESTBED_TopologyCompletionCallback
                                           comp_cb,
                                           void *comp_cb_cls,
                                           enum GNUNET_TESTBED_TopologyOption topo,
                                           ...)
{
  struct GNUNET_TESTBED_Operation *op;
  va_list vargs;

  GNUNET_assert (topo < GNUNET_TESTBED_TOPOLOGY_OPTION_END);
  va_start (vargs, topo);
  op = GNUNET_TESTBED_overlay_configure_topology_va (op_cls, num_peers, peers,
                                                     max_connections,
                                                     comp_cb, comp_cb_cls,
                                                     topo,
                                                     vargs);
  va_end (vargs);
  return op;
}


/**
 * Get a topology from a string input.
 *
 * @param topology where to write the retrieved topology
 * @param topology_string The string to attempt to
 *        get a configuration value from
 * @return GNUNET_YES if topology string matched a
 *         known topology, GNUNET_NO if not
 */
int
GNUNET_TESTBED_topology_get_ (enum GNUNET_TESTBED_TopologyOption *topology,
                              const char *topology_string)
{
  unsigned int cnt;

  for (cnt = 0; NULL != topology_strings[cnt]; cnt++)
  {
    if (0 == strcasecmp (topology_string, topology_strings[cnt]))
    {
      if (NULL != topology)
        *topology = (enum GNUNET_TESTBED_TopologyOption) cnt;
      return GNUNET_YES;
    }
  }
  return GNUNET_NO;
}


/**
 * Returns the string corresponding to the given topology
 *
 * @param topology the topology
 * @return the string (freshly allocated) of given topology; NULL if topology cannot be
 *           expressed as a string
 */
char *
GNUNET_TESTBED_topology_to_str_ (enum GNUNET_TESTBED_TopologyOption topology)
{
  if (GNUNET_TESTBED_TOPOLOGY_OPTION_END <= topology)
    return NULL;
  return GNUNET_strdup (topology_strings[topology]);
}

/* end of testbed_api_topology.c */