summaryrefslogtreecommitdiff
path: root/proxy.c
blob: cdbdec5f2f2994803eec011de6f3741136053d8e (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
/* This software was written by Dirk Engling <erdgeist@erdgeist.org>
   It is considered beerware. Prost. Skol. Cheers or whatever.

   $Id$ */

/* System */
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <unistd.h>
#include <errno.h>
#include <signal.h>
#include <stdio.h>
#include <pwd.h>
#include <ctype.h>
#include <pthread.h>

/* Libowfat */
#include "socket.h"
#include "io.h"
#include "iob.h"
#include "byte.h"
#include "scan.h"
#include "ip6.h"
#include "ndelay.h"

/* Opentracker */
#include "trackerlogic.h"
#include "ot_vector.h"
#include "ot_mutex.h"
#include "ot_stats.h"

#define WANT_SYNC_LIVE
#include "ot_livesync.h"

ot_ip6   g_serverip; 
uint16_t g_serverport = 9009;
uint32_t g_tracker_id;
char     groupip_1[4] = { 224,0,23,5 };
int      g_self_pipe[2];

/* If you have more than 10 peers, don't use this proxy
   Use 20 slots for 10 peers to have room for 10 incoming connection slots
 */
#define MAX_PEERS 20

#define LIVESYNC_INCOMING_BUFFSIZE          (256*256)
#define STREAMSYNC_OUTGOING_BUFFSIZE        (256*256)

#define LIVESYNC_OUTGOING_BUFFSIZE_PEERS     1480
#define LIVESYNC_OUTGOING_WATERMARK_PEERS   (sizeof(ot_peer)+sizeof(ot_hash))
#define LIVESYNC_MAXDELAY                    15      /* seconds */

/* The amount of time a complete sync cycle should take */
#define OT_SYNC_INTERVAL_MINUTES             2

/* So after each bucket wait 1 / OT_BUCKET_COUNT intervals */
#define OT_SYNC_SLEEP ( ( ( OT_SYNC_INTERVAL_MINUTES ) * 60 * 1000000 ) / ( OT_BUCKET_COUNT ) )

enum { OT_SYNC_PEER };
enum { FLAG_SERVERSOCKET = 1 };

/* For incoming packets */
static int64    g_socket_in = -1;
static uint8_t  g_inbuffer[LIVESYNC_INCOMING_BUFFSIZE];

/* For outgoing packets */
static int64    g_socket_out = -1;
static uint8_t  g_peerbuffer_start[LIVESYNC_OUTGOING_BUFFSIZE_PEERS];
static uint8_t *g_peerbuffer_pos;
static uint8_t *g_peerbuffer_highwater = g_peerbuffer_start + LIVESYNC_OUTGOING_BUFFSIZE_PEERS - LIVESYNC_OUTGOING_WATERMARK_PEERS;
static ot_time  g_next_packet_time;

static void * livesync_worker( void * args );
static void * streamsync_worker( void * args );
static void   livesync_proxytell( uint8_t prefix, uint8_t *info_hash, uint8_t *peer );

void exerr( char * message ) {
  fprintf( stderr, "%s\n", message );
  exit( 111 );
}

void stats_issue_event( ot_status_event event, PROTO_FLAG proto, uintptr_t event_data ) {
  (void) event;
  (void) proto;
  (void) event_data;
}

void livesync_bind_mcast( ot_ip6 ip, uint16_t port) {
  char tmpip[4] = {0,0,0,0};
  char *v4ip;

  if( !ip6_isv4mapped(ip))
    exerr("v6 mcast support not yet available.");
  v4ip = ip+12;

  if( g_socket_in != -1 )
    exerr("Error: Livesync listen ip specified twice.");

  if( ( g_socket_in = socket_udp4( )) < 0)
    exerr("Error: Cant create live sync incoming socket." );
  ndelay_off(g_socket_in);

  if( socket_bind4_reuse( g_socket_in, tmpip, port ) == -1 )
    exerr("Error: Cant bind live sync incoming socket." );

  if( socket_mcjoin4( g_socket_in, groupip_1, v4ip ) )
    exerr("Error: Cant make live sync incoming socket join mcast group.");

  if( ( g_socket_out = socket_udp4()) < 0)
    exerr("Error: Cant create live sync outgoing socket." );
  if( socket_bind4_reuse( g_socket_out, v4ip, port ) == -1 )
    exerr("Error: Cant bind live sync outgoing socket." );

  socket_mcttl4(g_socket_out, 1);
  socket_mcloop4(g_socket_out, 1);
}

size_t add_peer_to_torrent_proxy( ot_hash hash, ot_peer *peer ) {
  int         exactmatch;
  ot_torrent *torrent;
  ot_peer    *peer_dest;
  ot_vector  *torrents_list = mutex_bucket_lock_by_hash( hash );

  torrent = vector_find_or_insert( torrents_list, (void*)hash, sizeof( ot_torrent ), OT_HASH_COMPARE_SIZE, &exactmatch );
  if( !torrent )
    return -1;

  if( !exactmatch ) {
    /* Create a new torrent entry, then */
    memcpy( torrent->hash, hash, sizeof(ot_hash) );

    if( !( torrent->peer_list = malloc( sizeof (ot_peerlist) ) ) ) {
      vector_remove_torrent( torrents_list, torrent );
      mutex_bucket_unlock_by_hash( hash, 0 );
      return -1;
    }

    byte_zero( torrent->peer_list, sizeof( ot_peerlist ) );
  }

  /* Check for peer in torrent */
  peer_dest = vector_find_or_insert_peer( &(torrent->peer_list->peers), peer, &exactmatch );
  if( !peer_dest ) {
    mutex_bucket_unlock_by_hash( hash, 0 );
    return -1;
  }
  /* Tell peer that it's fresh */
  OT_PEERTIME( peer ) = 0;

  /* If we hadn't had a match create peer there */
  if( !exactmatch ) {
    torrent->peer_list->peer_count++;
    if( OT_PEERFLAG(peer) & PEER_FLAG_SEEDING )
      torrent->peer_list->seed_count++;
  }
  memcpy( peer_dest, peer, sizeof(ot_peer) );
  mutex_bucket_unlock_by_hash( hash, 0 );
  return 0;
}

size_t remove_peer_from_torrent_proxy( ot_hash hash, ot_peer *peer ) {
  int          exactmatch;
  ot_vector   *torrents_list = mutex_bucket_lock_by_hash( hash );
  ot_torrent  *torrent = binary_search( hash, torrents_list->data, torrents_list->size, sizeof( ot_torrent ), OT_HASH_COMPARE_SIZE, &exactmatch );

  if( exactmatch ) {
    ot_peerlist *peer_list = torrent->peer_list;
    switch( vector_remove_peer( &peer_list->peers, peer ) ) {
      case 2:  peer_list->seed_count--; /* Fall throughs intended */
      case 1:  peer_list->peer_count--; /* Fall throughs intended */
      default: break;
    }
  }

  mutex_bucket_unlock_by_hash( hash, 0 );
  return 0;
}

void free_peerlist( ot_peerlist *peer_list ) {
  if( peer_list->peers.data ) {
    if( OT_PEERLIST_HASBUCKETS( peer_list ) ) {
      ot_vector *bucket_list = (ot_vector*)(peer_list->peers.data);

      while( peer_list->peers.size-- )
        free( bucket_list++->data );
    }
    free( peer_list->peers.data );
  }
  free( peer_list );
}

static void livesync_handle_peersync( ssize_t datalen ) {
  int off = sizeof( g_tracker_id ) + sizeof( uint32_t );

  /* Now basic sanity checks have been done on the live sync packet
     We might add more testing and logging. */
  while( off + (ssize_t)sizeof( ot_hash ) + (ssize_t)sizeof( ot_peer ) <= datalen ) {
    ot_peer *peer = (ot_peer*)(g_inbuffer + off + sizeof(ot_hash));
    ot_hash *hash = (ot_hash*)(g_inbuffer + off);

    if( OT_PEERFLAG(peer) & PEER_FLAG_STOPPED )
      remove_peer_from_torrent_proxy( *hash, peer );
    else
      add_peer_to_torrent_proxy( *hash, peer );

    off += sizeof( ot_hash ) + sizeof( ot_peer );
  }
}

int usage( char *self ) {
  fprintf( stderr, "Usage: %s -i ip -p port\n", self );
  return 0;
}

enum {
  FLAG_OUTGOING      = 0x80,

  FLAG_DISCONNECTED  = 0x00,
  FLAG_CONNECTING    = 0x01,
  FLAG_WAITTRACKERID = 0x02,
  FLAG_CONNECTED     = 0x03,

  FLAG_MASK          = 0x07
};

#define PROXYPEER_NEEDSCONNECT(flag)      ((flag)==FLAG_OUTGOING)
#define PROXYPEER_SETDISCONNECTED(flag)   (flag)=(((flag)&FLAG_OUTGOING)|FLAG_DISCONNECTED)
#define PROXYPEER_SETCONNECTING(flag)     (flag)=(((flag)&FLAG_OUTGOING)|FLAG_CONNECTING)
#define PROXYPEER_SETWAITTRACKERID(flag)  (flag)=(((flag)&FLAG_OUTGOING)|FLAG_WAITTRACKERID)
#define PROXYPEER_SETCONNECTED(flag)      (flag)=(((flag)&FLAG_OUTGOING)|FLAG_CONNECTED)

typedef struct {
  int      state;           /* Whether we want to connect, how far our handshake is, etc. */
  ot_ip6   ip;              /* The peer to connect to */
  uint16_t port;            /* The peers port */
  uint8_t  indata[8192*16]; /* Any data not processed yet */
  size_t   indata_length;   /* Length of unprocessed data */
  uint32_t tracker_id;      /* How the other end greeted */
  int64    fd;              /* A file handle, if connected, <= 0 is disconnected (0 initially, -1 else) */
  io_batch outdata;         /* The iobatch containing our sync data */

  int      packet_tcount;   /* Number of unprocessed torrents in packet we currently receive */
  char     packet_tprefix;  /* Prefix byte for all torrents in current packet */
  char     packet_type;     /* Type of current packet */
  uint32_t packet_tid;      /* Tracker id for current packet */

} proxy_peer;
static void process_indata( proxy_peer * peer );

void reset_info_block( proxy_peer * peer ) {
  peer->indata_length = 0;
  peer->tracker_id    = 0;
  peer->fd            = -1;
  peer->packet_tcount = 0;
  iob_reset( &peer->outdata );
  PROXYPEER_SETDISCONNECTED( peer->state );
}

/* Number of connections to peers
   * If a peer's IP is set, we try to reconnect, when the connection drops
   * If we already have a connected tracker_id in our records for an _incoming_ connection, drop it
   * Multiple connections to/from the same ip are okay, if tracker_id doesn't match
   * Reconnect attempts occur only twice a minute
*/
static int        g_connection_count;
static ot_time    g_connection_reconn;
static proxy_peer g_connections[MAX_PEERS];

static void handle_reconnects( void ) {
  int i;
  for( i=0; i<g_connection_count; ++i )
    if( PROXYPEER_NEEDSCONNECT( g_connections[i].state ) ) {
      int64 newfd = socket_tcp6( );
      if( newfd < 0 ) continue; /* No socket for you */
      io_fd(newfd);
      if( socket_bind6_reuse(newfd,g_serverip,g_serverport,0) ) {
        io_close( newfd );
        continue;
      }
      if( socket_connect6(newfd,g_connections[i].ip,g_connections[i].port,0) == -1 &&
          errno != EINPROGRESS && errno != EWOULDBLOCK ) {
        close(newfd);
        continue;
      }
      io_wantwrite(newfd); /* So we will be informed when it is connected */
      io_setcookie(newfd,g_connections+i);

      /* Prepare connection info block */
      reset_info_block( g_connections+i );
      g_connections[i].fd            = newfd;
      PROXYPEER_SETCONNECTING( g_connections[i].state );
    }
  g_connection_reconn = time(NULL) + 30;
}

/* Handle incoming connection requests, check against whitelist */
static void handle_accept( int64 serversocket ) {
  int64 newfd;
  ot_ip6 ip;
  uint16 port;

  while( ( newfd = socket_accept6( serversocket, ip, &port, NULL ) ) != -1 ) {

    /* XXX some access control */

    /* Put fd into a non-blocking mode */
    io_nonblock( newfd );

    if( !io_fd( newfd ) )
      io_close( newfd );
    else {
      /* Find a new home for our incoming connection */
      int i;
      for( i=0; i<MAX_PEERS; ++i )
        if( g_connections[i].state == FLAG_DISCONNECTED )
          break;
      if( i == MAX_PEERS ) {
        fprintf( stderr, "No room for incoming connection." );
        close( newfd );
        continue;
      }

      /* Prepare connection info block */
      reset_info_block( g_connections+i );
      PROXYPEER_SETCONNECTING( g_connections[i].state );
      g_connections[i].port = port;
      g_connections[i].fd   = newfd;

      io_setcookie( newfd, g_connections + i );

      /* We expect the connecting side to begin with its tracker_id */
      io_wantread( newfd );
    }
  }

  return;
}

/* New sync data on the stream */
static void handle_read( int64 peersocket ) {
  int i;
  int64 datalen;
  uint32_t tracker_id;
  proxy_peer *peer = io_getcookie( peersocket );

  if( !peer ) {
    /* Can't happen ;) */
    io_close( peersocket );
    return;
  }
  switch( peer->state & FLAG_MASK ) {
  case FLAG_DISCONNECTED:
    io_close( peersocket );
    break; /* Shouldnt happen */
  case FLAG_CONNECTING:
  case FLAG_WAITTRACKERID:
    /* We want at least the first four bytes to come at once, to avoid keeping extra states (for now)
       This also catches 0 bytes reads == EOF and negative values, denoting connection errors */
    if( io_tryread( peersocket, (void*)&tracker_id, sizeof( tracker_id ) ) != sizeof( tracker_id ) )
      goto close_socket;

    /* See, if we already have a connection to that peer */
    for( i=0; i<MAX_PEERS; ++i )
      if( ( g_connections[i].state & FLAG_MASK ) == FLAG_CONNECTED && 
            g_connections[i].tracker_id == tracker_id )
        goto close_socket;

    /* Also no need for soliloquy */
    if( tracker_id == g_tracker_id )
      goto close_socket;

    /* The new connection is good, send our tracker_id on incoming connections */
    if( peer->state == FLAG_CONNECTING )
      io_trywrite( peersocket, (void*)&g_tracker_id, sizeof( g_tracker_id ) );

    peer->tracker_id = tracker_id;
    PROXYPEER_SETCONNECTED( peer->state );

    break;
close_socket:
    io_close( peersocket );
    reset_info_block( peer ); 
    break;
  case FLAG_CONNECTED:
    /* Here we acutally expect data from peer
       indata_length should be less than 20+256*7 bytes, for incomplete torrent entries */
    datalen = io_tryread( peersocket, (void*)(peer->indata + peer->indata_length), sizeof( peer->indata ) - peer->indata_length ); 
    if( !datalen || datalen < -1 ) {
      io_close( peersocket );
      reset_info_block( peer );
    } else if( datalen > 0 ) {
      peer->indata_length += datalen;
      process_indata( peer );
    }
    break;
  }
}

/* Can write new sync data to the stream */
static void handle_write( int64 peersocket ) {
  proxy_peer *peer = io_getcookie( peersocket );
  if( !peer ) { 
    /* Can't happen ;) */
    io_close( peersocket );
    return;
  }

  switch( peer->state & FLAG_MASK ) {
  case FLAG_DISCONNECTED:
  default: /* Should not happen */
    io_close( peersocket );
    break;
  case FLAG_CONNECTING:
    /* Ensure that the connection is established and handle connection error */
    if( peer->state & FLAG_OUTGOING && !socket_connected( peersocket ) ) {
        io_close( peersocket );
        break;
    }

    io_trywrite( peersocket, (void*)&g_tracker_id, sizeof( g_tracker_id ) );
    PROXYPEER_SETWAITTRACKERID( peer->state );
    io_dontwantwrite( peersocket );
    io_wantread( peersocket );
    break;
  case FLAG_CONNECTED:
    switch( iob_send( peersocket, &peer->outdata ) ) {
    case 0: /* all data sent */
      io_dontwantwrite( peersocket );
      break;
    case -3: /* an error occured */
      io_close( peersocket );
      reset_info_block( peer );
      break;
    default: /* Normal operation or eagain */
      break;
    }
    break;
  }

  return;
}

static void server_mainloop() {
  int64 sock;
  tai6464 now;

  /* inlined livesync_init() */
  memset( g_peerbuffer_start, 0, sizeof( g_peerbuffer_start ) ); 
  g_peerbuffer_pos = g_peerbuffer_start;
  memcpy( g_peerbuffer_pos, &g_tracker_id, sizeof( g_tracker_id ) );
  uint32_pack_big( (char*)g_peerbuffer_pos + sizeof( g_tracker_id ), OT_SYNC_PEER);
  g_peerbuffer_pos += sizeof( g_tracker_id ) + sizeof( uint32_t);
  g_next_packet_time = time(NULL) + LIVESYNC_MAXDELAY;

  while(1) {
    /* See, if we need to connect to anyone */
    if( time(NULL) > g_connection_reconn )
      handle_reconnects( );

    /* Wait for io events until next approx reconn check time */
    taia_now( &now );
    taia_addsec( &now, &now, 30 );
    io_waituntil( now );

    /* Loop over readable sockets */
    while( ( sock = io_canread( ) ) != -1 ) {
      const void *cookie = io_getcookie( sock );
      if( (uintptr_t)cookie == FLAG_SERVERSOCKET )
        handle_accept( sock );
      else
        handle_read( sock );
    }

    /* Loop over writable sockets */
    while( ( sock = io_canwrite( ) ) != -1 )
      handle_write( sock );

    livesync_ticker( );
  }
}

int main( int argc, char **argv ) {
  static pthread_t sync_in_thread_id;
  static pthread_t sync_out_thread_id;
  ot_ip6 serverip;
  uint16_t tmpport;
  int scanon = 1, bound = 0;

  srandom( time(NULL) );
  g_tracker_id = random();

  while( scanon ) {
    switch( getopt( argc, argv, ":i:p:vh" ) ) {
    case -1: scanon = 0; break;
    case 'S': 
      if( !scan_ip6( optarg, serverip )) { usage( argv[0] ); exit( 1 ); }
      break;
    case 'p':
      if( !scan_ushort( optarg, &tmpport)) { usage( argv[0] ); exit( 1 ); }
      livesync_bind_mcast( serverip, tmpport); bound++; break;
    default:
    case '?': usage( argv[0] ); exit( 1 );
    }
  }

  if( !bound ) exerr( "No port bound." );
  pthread_create( &sync_in_thread_id, NULL, livesync_worker, NULL );
  pthread_create( &sync_out_thread_id, NULL, streamsync_worker, NULL );

  server_mainloop();
  return 0;
}

static void * streamsync_worker( void * args ) {
  (void)args;
  while( 1 ) {
    int bucket;
    /* For each bucket... */
    for( bucket=0; bucket<OT_BUCKET_COUNT; ++bucket ) {
      /* Get exclusive access to that bucket */
      ot_vector *torrents_list = mutex_bucket_lock( bucket );
      size_t tor_offset, count_def = 0, count_one = 0, count_two = 0, count_peers = 0;
      size_t mem, mem_a = 0, mem_b = 0;
      uint8_t *ptr, *ptr_a, *ptr_b, *ptr_c;

      /* For each torrent in this bucket.. */
      for( tor_offset=0; tor_offset<torrents_list->size; ++tor_offset ) {
        /* Address torrents members */
        ot_peerlist *peer_list = ( ((ot_torrent*)(torrents_list->data))[tor_offset] ).peer_list;
        switch( peer_list->peer_count ) {
          case 2: count_two++; break;
          case 1: count_one++; break;
          case 0: break;
          default:
            count_peers += peer_list->peer_count;
            count_def   += 1 + ( peer_list->peer_count >> 8 );
        }
      }

      /* Maximal memory requirement: max 3 blocks, max torrents * 20 + max peers * 7 */
      mem = 3 * ( 4 + 1 + 1 + 2 ) + ( count_one + count_two ) * 19 + count_def * 20 +
            ( count_one + 2 * count_two + count_peers ) * 7;

      ptr = ptr_a = ptr_b = ptr_c = malloc( mem );
      if( !ptr ) goto unlock_continue;

      if( count_one > 8 ) {
        mem_a = 4 + 1 + 1 + 2 + count_one * ( 19 + 7 );
        ptr_b += mem_a; ptr_c += mem_a;
        memcpy( ptr_a, &g_tracker_id, sizeof(g_tracker_id)); /* Offset 0: the tracker ID */
        ptr_a[4] = 1;                                       /* Offset 4: packet type 1 */
        ptr_a[5] = (bucket << 8) >> OT_BUCKET_COUNT_BITS;   /* Offset 5: the shared prefix */
        ptr_a[6] = count_one >> 8;
        ptr_a[7] = count_one & 255;
        ptr_a += 8;
      } else {
        count_def   += count_one;
        count_peers += count_one;
      }

      if( count_two > 8 ) {
        mem_b = 4 + 1 + 1 + 2 + count_two * ( 19 + 14 );
        ptr_c += mem_b;
        memcpy( ptr_b, &g_tracker_id, sizeof(g_tracker_id)); /* Offset 0: the tracker ID */
        ptr_b[4] = 2;                                       /* Offset 4: packet type 2 */
        ptr_b[5] = (bucket << 8) >> OT_BUCKET_COUNT_BITS;   /* Offset 5: the shared prefix */
        ptr_b[6] = count_two >> 8;
        ptr_b[7] = count_two & 255;
        ptr_b += 8;
      } else {
        count_def   += count_two;
        count_peers += 2 * count_two;
      }

      if( count_def ) {
        memcpy( ptr_c, &g_tracker_id, sizeof(g_tracker_id)); /* Offset 0: the tracker ID */
        ptr_c[4] = 0;                                       /* Offset 4: packet type 0 */
        ptr_c[5] = (bucket << 8) >> OT_BUCKET_COUNT_BITS;   /* Offset 5: the shared prefix */
        ptr_c[6] = count_def >> 8;
        ptr_c[7] = count_def & 255;
        ptr_c += 8;
      }

      /* For each torrent in this bucket.. */
      for( tor_offset=0; tor_offset<torrents_list->size; ++tor_offset ) {
        /* Address torrents members */
        ot_torrent *torrent = ((ot_torrent*)(torrents_list->data)) + tor_offset;
        ot_peerlist *peer_list = torrent->peer_list;
        ot_peer *peers = (ot_peer*)(peer_list->peers.data);
        uint8_t **dst;
        int multi = 0;
        switch( peer_list->peer_count ) {
          case 0:  continue;
          case 1:  dst = mem_a ? &ptr_a : &ptr_c; break;
          case 2:  dst = mem_b ? &ptr_b : &ptr_c; break;
          default: dst = &ptr_c; multi = 1; break;
        }

        do {
          size_t i, pc = peer_list->peer_count;
          if( pc > 255 ) pc = 255;
          memcpy( *dst, torrent->hash + 1, sizeof( ot_hash ) - 1);
          *dst += sizeof( ot_hash ) - 1;
          if( multi ) *(*dst)++ = pc;
          for( i=0; i < pc; ++i ) {
            memcpy( *dst, peers++, OT_IP_SIZE + 3 );
            *dst += OT_IP_SIZE + 3;
          }
          peer_list->peer_count -= pc; 
        } while( peer_list->peer_count );
        free_peerlist(peer_list);
      }

      free( torrents_list->data );
      memset( torrents_list, 0, sizeof(*torrents_list ) );
unlock_continue:
      mutex_bucket_unlock( bucket, 0 );

      if( ptr ) {
        int i;

        if( ptr_b > ptr_c ) ptr_c = ptr_b;
        if( ptr_a > ptr_c ) ptr_c = ptr_a;
        mem = ptr_c - ptr;

        for( i=0; i<g_connection_count; ++i ) {
          if( g_connections[i].fd != -1 ) {
            void *tmp = malloc( mem );
            if( tmp )
              if( !iob_addbuf_free( &g_connections[i].outdata, tmp, mem ) )
                free( tmp );
          }
        }

        free( ptr );
      }
      usleep( OT_SYNC_SLEEP );
    }
  }
  return 0;
}

static void livesync_issue_peersync( ) {
  socket_send4(g_socket_out, (char*)g_peerbuffer_start, g_peerbuffer_pos - g_peerbuffer_start,
               groupip_1, LIVESYNC_PORT);
  g_peerbuffer_pos   = g_peerbuffer_start + sizeof( g_tracker_id ) + sizeof( uint32_t );
  g_next_packet_time = time(NULL) + LIVESYNC_MAXDELAY;
}

void livesync_ticker( ) {
  /* livesync_issue_peersync sets g_next_packet_time */
  if( time(NULL) > g_next_packet_time &&
     g_peerbuffer_pos > g_peerbuffer_start + sizeof( g_tracker_id ) )
    livesync_issue_peersync();
}

static void livesync_proxytell( uint8_t prefix, uint8_t *info_hash, uint8_t *peer ) {
  *g_peerbuffer_pos = prefix;
  memcpy( g_peerbuffer_pos + 1, info_hash, sizeof(ot_hash) - 1 );
  memcpy( g_peerbuffer_pos + sizeof(ot_hash), peer, sizeof(ot_peer) - 1 );

  g_peerbuffer_pos += sizeof(ot_hash) + sizeof(ot_peer);

  if( g_peerbuffer_pos >= g_peerbuffer_highwater )
    livesync_issue_peersync();
}

static void process_indata( proxy_peer * peer ) {
  int ensuremem, consumed, peers;
  uint8_t *data    = peer->indata, *hash;
  uint8_t *dataend = data + peer->indata_length;

  while( 1 ) {
    /* If we're not inside of a packet, make a new one */
    if( !peer->packet_tcount ) {
      /* Ensure the header is complete or postpone processing */
      if( data + 8 > dataend ) break;
      memcpy( &peer->packet_tid, data, sizeof(peer->packet_tid) );
      peer->packet_type    = data[4];
      peer->packet_tprefix = data[5];
      peer->packet_tcount  = data[6] * 256 + data[7];
      data += 8;
    }

    /* ensure size for the complete torrent block */
    if( data + 26 > dataend ) break;
    peers = peer->packet_type ? peer->packet_type : data[19];
    ensuremem = 19 + ( peer->packet_type == 0 ) + 7 * peers;
    if( data + ensuremem > dataend ) break;

    hash = data;
    data += 19 + ( peer->packet_type == 0 );

    while( peers-- ) {
      livesync_proxytell( peer->packet_tprefix, hash, data );
      data += 7;
    }
  }

  consumed = data - peer->indata;
  memmove( peer->indata, data, peer->indata_length - consumed );
  peer->indata_length -= consumed;
}

static void * livesync_worker( void * args ) {
  (void)args;
  while( 1 ) {
    ot_ip6 in_ip; uint16_t in_port;
    size_t datalen = socket_recv4(g_socket_in, (char*)g_inbuffer, LIVESYNC_INCOMING_BUFFSIZE, 12+(char*)in_ip, &in_port);

    /* Expect at least tracker id and packet type */
    if( datalen <= (ssize_t)(sizeof( g_tracker_id ) + sizeof( uint32_t )) )
      continue;
    if( !memcmp( g_inbuffer, &g_tracker_id, sizeof( g_tracker_id ) ) ) {
      /* drop packet coming from ourselves */
      continue;
    }
    switch( uint32_read_big( sizeof( g_tracker_id ) + (char*)g_inbuffer ) ) {
    case OT_SYNC_PEER:
      livesync_handle_peersync( datalen );
      break;
    default:
      fprintf( stderr, "Received an unknown live sync packet type %u.\n", uint32_read_big( sizeof( g_tracker_id ) + (char*)g_inbuffer ) );
      break;
    }
  }
  return 0;
}