summaryrefslogtreecommitdiff
path: root/src/vpn/gnunet-daemon-vpn.c
blob: 72f52eccc767c677abe31ff48aacd8ad23451036 (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
/*
     This file is part of GNUnet.
     (C) 2010 Christian Grothoff

     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 vpn/gnunet-daemon-vpn.c
 * @brief
 * @author Philipp Toelke
 */
#include "platform.h"
#include "gnunet_getopt_lib.h"
#include "gnunet_program_lib.h"
#include "gnunet-vpn-packet.h"
#include "gnunet_common.h"
#include "gnunet_protocols.h"
#include <gnunet_mesh_service.h>
#include "gnunet_client_lib.h"
#include "gnunet_container_lib.h"
#include "gnunet_constants.h"
#include <block_dns.h>
#include "gnunet-daemon-vpn-helper.h"
#include "gnunet-daemon-vpn-dns.h"
#include "gnunet-daemon-vpn.h"
#include "gnunet-vpn-checksum.h"

const struct GNUNET_CONFIGURATION_Handle *cfg;
struct GNUNET_MESH_Handle *mesh_handle;
struct GNUNET_CONTAINER_MultiHashMap* hashmap;
static struct GNUNET_CONTAINER_Heap *heap;

/**
 * If there are at least this many address-mappings, old ones will be removed
 */
static long long unsigned int max_mappings = 200;

/**
 * Final status code.
 */
static int ret;

/**
 * This hashmap contains the mapping from peer, service-descriptor,
 * source-port and destination-port to a socket
 */
static struct GNUNET_CONTAINER_MultiHashMap *udp_connections;

/**
 * Function scheduled as very last function, cleans up after us
 *{{{
 */
static void
cleanup(void* cls, const struct GNUNET_SCHEDULER_TaskContext* tskctx) {
    GNUNET_assert (0 != (tskctx->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN));

    /* stop the helper */
    cleanup_helper(helper_handle);

    /* close the connection to the service-dns */
    if (dns_connection != NULL)
      {
	GNUNET_CLIENT_disconnect (dns_connection, GNUNET_NO);
	dns_connection = NULL;
      }

    if (mesh_handle != NULL)
      {
	GNUNET_MESH_disconnect(mesh_handle);
	mesh_handle = NULL;
      }
}
/*}}}*/

/**
 * @return the hash of the IP-Address if a mapping exists, NULL otherwise
 */
GNUNET_HashCode*
address_mapping_exists(unsigned char addr[]) {
    GNUNET_HashCode* key = GNUNET_malloc(sizeof(GNUNET_HashCode));
    unsigned char* k = (unsigned char*)key;
    memset(key, 0, sizeof(GNUNET_HashCode));
    unsigned int i;
    for (i = 0; i < 16; i++)
	k[15-i] = addr[i];

    if (GNUNET_YES == GNUNET_CONTAINER_multihashmap_contains(hashmap, key))
      return key;
    else
      {
	GNUNET_free(key);
	return NULL;
      }
}

static void
collect_mappings(void* cls, const struct GNUNET_SCHEDULER_TaskContext* tc) {
    if ( (tc->reason & GNUNET_SCHEDULER_REASON_SHUTDOWN) != 0)
      return;

    struct map_entry* me = GNUNET_CONTAINER_heap_remove_root(heap);

    /* This is free()ed memory! */
    me->heap_node = NULL;

    /* FIXME! GNUNET_MESH_close_tunnel(state->tunnel); */

    GNUNET_CONTAINER_multihashmap_remove(hashmap, &me->hash, me);

    GNUNET_free(me);
}

void
send_icmp_response(void* cls, const struct GNUNET_SCHEDULER_TaskContext *tc) {
    struct ip6_icmp* request = cls;

    struct ip6_icmp* response = alloca(ntohs(request->shdr.size));
    GNUNET_assert(response != NULL);
    memset(response, 0, ntohs(request->shdr.size));

    response->shdr.size = request->shdr.size;
    response->shdr.type = htons(GNUNET_MESSAGE_TYPE_VPN_HELPER);

    response->tun.flags = 0;
    response->tun.type = htons(0x86dd);

    response->ip6_hdr.hoplmt = 255;
    response->ip6_hdr.paylgth = request->ip6_hdr.paylgth;
    response->ip6_hdr.nxthdr = 0x3a;
    response->ip6_hdr.version = 6;
    memcpy(&response->ip6_hdr.sadr, &request->ip6_hdr.dadr, 16);
    memcpy(&response->ip6_hdr.dadr, &request->ip6_hdr.sadr, 16);

    response->icmp_hdr.code = 0;
    response->icmp_hdr.type = 0x81;

    /* Magic, more Magic! */
    response->icmp_hdr.chks = request->icmp_hdr.chks - 0x1;

    /* Copy the rest of the packet */
    memcpy(response+1, request+1, ntohs(request->shdr.size) - sizeof(struct ip6_icmp));

    write_to_helper(response, ntohs(response->shdr.size));

    GNUNET_free(request);
}

/**
 * cls is the pointer to a GNUNET_MessageHeader that is
 * followed by the service-descriptor and the packet that should be sent;
 */
static size_t
send_pkt_to_peer_notify_callback (void *cls, size_t size, void *buf)
{
  struct GNUNET_MESH_Tunnel **tunnel = cls;
  struct GNUNET_MessageHeader *hdr =
    (struct GNUNET_MessageHeader *) (tunnel + 1);
  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "send_pkt_to_peer_notify_callback: buf = %x; size = %u;\n", buf, size);
  GNUNET_assert (size >= ntohs (hdr->size));
  memcpy (buf, hdr, ntohs (hdr->size));
  size = ntohs(hdr->size);
  GNUNET_free (cls);
  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Sent!\n");
  return size;
}

unsigned int
port_in_ports (uint64_t ports, uint16_t port)
{
  uint16_t *ps = (uint16_t *) & ports;
  return ps[0] == port || ps[1] == port || ps[2] == port || ps[3] == port;
}

void
send_pkt_to_peer (void *cls, 
		  const struct GNUNET_PeerIdentity *peer,
		  const struct GNUNET_TRANSPORT_ATS_Information *atsi)
{
  if (peer == NULL) return;
  struct GNUNET_MESH_Tunnel **tunnel = cls;
  struct GNUNET_MessageHeader *hdr =
    (struct GNUNET_MessageHeader *) (tunnel + 1);

  GNUNET_assert(NULL != tunnel);
  GNUNET_assert(NULL != *tunnel);

  GNUNET_MESH_notify_transmit_ready (*tunnel,
				     GNUNET_NO,
				     42,
				     GNUNET_TIME_relative_divide(GNUNET_CONSTANTS_MAX_CORK_DELAY, 2),
                                     (const struct GNUNET_PeerIdentity *)NULL,
                                     ntohs(hdr->size),
				     send_pkt_to_peer_notify_callback,
				     cls);
}

/**
 * Create a new Address from an answer-packet
 */
void
new_ip6addr(unsigned char* buf, const GNUNET_HashCode *peer, const GNUNET_HashCode *service_desc) { /* {{{ */
    char* ipv6addr;
    unsigned long long ipv6prefix;
    GNUNET_assert(GNUNET_OK == GNUNET_CONFIGURATION_get_value_string(cfg, "vpn", "IPV6ADDR", &ipv6addr));
    GNUNET_assert(GNUNET_OK == GNUNET_CONFIGURATION_get_value_number(cfg, "vpn", "IPV6PREFIX", &ipv6prefix));
    GNUNET_assert(ipv6prefix < 127);
    ipv6prefix = (ipv6prefix + 7)/8;

    inet_pton (AF_INET6, ipv6addr, buf);
    GNUNET_free(ipv6addr);

    int peer_length = 16 - ipv6prefix - 6;
    if (peer_length <= 0)
      peer_length = 0;

    int service_length = 16 - ipv6prefix - peer_length;
    if (service_length <= 0)
      service_length = 0;

    memcpy(buf+ipv6prefix, service_desc, service_length);
    memcpy(buf+ipv6prefix+service_length, peer, peer_length);
}
/*}}}*/

char
max (char a, char b)
{
  return a > b ? a : b;
}

/**
 * Create a new Address from an answer-packet
 */
void
new_ip6addr_remote (unsigned char *buf, unsigned char *addr, char addrlen)
{                               /* {{{ */
  char *ipv6addr;
  unsigned long long ipv6prefix;
  GNUNET_assert (GNUNET_OK ==
                 GNUNET_CONFIGURATION_get_value_string (cfg, "vpn",
                                                        "IPV6ADDR",
                                                        &ipv6addr));
  GNUNET_assert (GNUNET_OK ==
                 GNUNET_CONFIGURATION_get_value_number (cfg, "vpn",
                                                        "IPV6PREFIX",
                                                        &ipv6prefix));
  GNUNET_assert (ipv6prefix < 127);
  ipv6prefix = (ipv6prefix + 7) / 8;

  inet_pton (AF_INET6, ipv6addr, buf);
  GNUNET_free (ipv6addr);

  int local_length = 16 - ipv6prefix;

  memcpy (buf + ipv6prefix, addr, max (addrlen, local_length));
}
/*}}}*/

/**
 * This gets scheduled with cls pointing to an answer_packet and does everything
 * needed in order to send it to the helper.
 *
 * At the moment this means "inventing" and IPv6-Address for .gnunet-services and
 * doing nothing for "real" services.
 */
void
process_answer(void* cls, const struct GNUNET_SCHEDULER_TaskContext* tc) {
    struct answer_packet* pkt = cls;
    struct answer_packet_list* list;

    /* This answer is about a .gnunet-service
     *
     * It contains an almost complete DNS-Response, we have to fill in the ip
     * at the offset pkt->addroffset
     */
    if (pkt->subtype == GNUNET_DNS_ANSWER_TYPE_SERVICE)
      {
	pkt->subtype = GNUNET_DNS_ANSWER_TYPE_IP;

	GNUNET_HashCode key;
	memset(&key, 0, sizeof(GNUNET_HashCode));

	unsigned char* c = ((unsigned char*)pkt)+ntohs(pkt->addroffset);
	unsigned char* k = (unsigned char*)&key;
	new_ip6addr(c, &pkt->service_descr.peer, &pkt->service_descr.service_descriptor);
	/*
	 * Copy the newly generated ip-address to the key backwarts (as only the first part is hashed)
	 */
	unsigned int i;
	for (i = 0; i < 16; i++)
	    k[15-i] = c[i];

	uint16_t namelen = strlen((char*)pkt->data+12)+1;

	struct map_entry* value = GNUNET_malloc(sizeof(struct map_entry) + namelen);
	char* name = (char*)(value +1);

	value->namelen = namelen;
	memcpy(name, pkt->data+12, namelen);

	memcpy(&value->desc, &pkt->service_descr, sizeof(struct GNUNET_vpn_service_descriptor));

        memset(value->additional_ports, 0, 8192);

        memcpy(&value->hash, &key, sizeof(GNUNET_HashCode));

        if (GNUNET_NO ==
            GNUNET_CONTAINER_multihashmap_contains (hashmap, &key))
          {
            GNUNET_CONTAINER_multihashmap_put (hashmap, &key, value,
                                               GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY);

            value->heap_node = GNUNET_CONTAINER_heap_insert (heap, value,
                                                             GNUNET_TIME_absolute_get ().abs_value);
            if (GNUNET_CONTAINER_heap_get_size(heap) > max_mappings)
              GNUNET_SCHEDULER_add_now(collect_mappings, NULL);
          }
        else
          GNUNET_free(value);


	list = GNUNET_malloc(htons(pkt->hdr.size) + 2*sizeof(struct answer_packet_list*));

	memcpy(&list->pkt, pkt, htons(pkt->hdr.size));

      }
    else if (pkt->subtype == GNUNET_DNS_ANSWER_TYPE_REV)
      {
	GNUNET_HashCode key;
	memset(&key, 0, sizeof key);
	unsigned char* k = (unsigned char*)&key;
	unsigned char* s = pkt->data+12;
	int i = 0;
	/* Whoever designed the reverse IPv6-lookup is batshit insane */
	for (i = 0; i < 16; i++)
	  {
	    unsigned char c1 = s[(4*i)+1];
	    unsigned char c2 = s[(4*i)+3];
	    if (c1 <= '9')
	      k[i] = c1 - '0';
	    else
	      k[i] = c1 - 87; /* 87 is the difference between 'a' and 10 */
	    if (c2 <= '9')
	      k[i] += 16*(c2 - '0');
	    else
	      k[i] += 16*(c2 - 87);
	  }

	struct map_entry* map_entry = GNUNET_CONTAINER_multihashmap_get(hashmap, &key);
        GNUNET_CONTAINER_heap_update_cost (heap, map_entry->heap_node,
                                           GNUNET_TIME_absolute_get ().abs_value);

	uint16_t offset = ntohs(pkt->addroffset);

	if (map_entry == NULL)
	  {
	    GNUNET_free(pkt);
	    return;
	  }

        unsigned short namelen = htons(map_entry->namelen);
	char* name = (char*)(map_entry + 1);

	list = GNUNET_malloc(2*sizeof(struct answer_packet_list*) + offset + 2 + ntohs(namelen));

	struct answer_packet* rpkt = &list->pkt;

	/* The offset points to the first byte belonging to the address */
	memcpy(rpkt, pkt, offset - 1);

	rpkt->subtype = GNUNET_DNS_ANSWER_TYPE_IP;
	rpkt->hdr.size = ntohs(offset + 2 + ntohs(namelen));

	memcpy(((char*)rpkt)+offset, &namelen, 2);
	memcpy(((char*)rpkt)+offset+2, name, ntohs(namelen));

      }
    else if (pkt->subtype == GNUNET_DNS_ANSWER_TYPE_IP)
      {
	list = GNUNET_malloc(htons(pkt->hdr.size) + 2*sizeof(struct answer_packet_list*));
	memcpy(&list->pkt, pkt, htons(pkt->hdr.size));
      }
    else if (pkt->subtype == GNUNET_DNS_ANSWER_TYPE_REMOTE)
      {
	pkt->subtype = GNUNET_DNS_ANSWER_TYPE_IP;

	GNUNET_HashCode key;
	memset(&key, 0, sizeof(GNUNET_HashCode));

	unsigned char* c = ((unsigned char*)pkt)+ntohs(pkt->addroffset);
        new_ip6addr_remote(c, pkt->addr, pkt->addrsize);
	unsigned char* k = (unsigned char*)&key;
	/*
	 * Copy the newly generated ip-address to the key backwards (as only the first part is used in the hash-table)
	 */
	unsigned int i;
	for (i = 0; i < 16; i++)
	    k[15-i] = c[i];

	uint16_t namelen = strlen((char*)pkt->data+12)+1;

	struct map_entry* value = GNUNET_malloc(sizeof(struct map_entry) + namelen);
	char* name = (char*)(value +1);

	value->namelen = namelen;
	memcpy(name, pkt->data+12, namelen);

        value->addrlen = pkt->addrsize;
        memcpy(&value->addr, &pkt->addr, pkt->addrsize);
        memset(value->additional_ports, 0, 8192);

        memcpy(&value->hash, &key, sizeof(GNUNET_HashCode));

        if (GNUNET_NO ==
            GNUNET_CONTAINER_multihashmap_contains (hashmap, &key))
          {
            GNUNET_CONTAINER_multihashmap_put (hashmap, &key, value,
                                               GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_ONLY);
            value->heap_node = GNUNET_CONTAINER_heap_insert (heap, value,
                                                             GNUNET_TIME_absolute_get ().abs_value);
            if (GNUNET_CONTAINER_heap_get_size(heap) > max_mappings)
              GNUNET_SCHEDULER_add_now(collect_mappings, NULL);
          }
        else
          GNUNET_free(value);

	list = GNUNET_malloc(htons(pkt->hdr.size) + 2*sizeof(struct answer_packet_list*));

	memcpy(&list->pkt, pkt, htons(pkt->hdr.size));
      }
    else
      {
	GNUNET_break(0);
	GNUNET_free(pkt);
	return;
      }

    GNUNET_free(pkt);

    GNUNET_CONTAINER_DLL_insert_after(answer_proc_head, answer_proc_tail, answer_proc_tail, list);

    schedule_helper_write(GNUNET_TIME_UNIT_FOREVER_REL, NULL);

    return;
}

/**
 * Sets a bit active in a bitArray.
 *
 * @param bitArray memory area to set the bit in
 * @param bitIdx which bit to set
 */
void
setBit (char *bitArray, unsigned int bitIdx)
{
  size_t arraySlot;
  unsigned int targetBit;

  arraySlot = bitIdx / 8;
  targetBit = (1L << (bitIdx % 8));
  bitArray[arraySlot] |= targetBit;
}

/**
 * Clears a bit from bitArray.
 *
 * @param bitArray memory area to set the bit in
 * @param bitIdx which bit to unset
 */
void
clearBit (char *bitArray, unsigned int bitIdx)
{
  size_t slot;
  unsigned int targetBit;

  slot = bitIdx / 8;
  targetBit = (1L << (bitIdx % 8));
  bitArray[slot] = bitArray[slot] & (~targetBit);
}

/**
 * Checks if a bit is active in the bitArray
 *
 * @param bitArray memory area to set the bit in
 * @param bitIdx which bit to test
 * @return GNUNET_YES if the bit is set, GNUNET_NO if not.
 */
int
testBit (char *bitArray, unsigned int bitIdx)
{
  size_t slot;
  unsigned int targetBit;

  slot = bitIdx / 8;
  targetBit = (1L << (bitIdx % 8));
  if (bitArray[slot] & targetBit)
    return GNUNET_YES;
  else
    return GNUNET_NO;
}

/**
 * @brief Add the port to the list of additional ports in the map_entry
 *
 * @param me the map_entry
 * @param port the port in host-byte-order
 */
static void
add_additional_port (struct map_entry *me, uint16_t port)
{
  setBit(me->additional_ports, port);
}

static int
receive_udp_back (void *cls, struct GNUNET_MESH_Tunnel* tunnel,
		  void **tunnel_ctx,
		  const struct GNUNET_PeerIdentity *sender,
		  const struct GNUNET_MessageHeader *message,
		  const struct GNUNET_TRANSPORT_ATS_Information *atsi)
{
  GNUNET_HashCode *desc = (GNUNET_HashCode *) (message + 1);
  struct udp_pkt *pkt = (struct udp_pkt *) (desc + 1);
  const struct GNUNET_PeerIdentity* other = GNUNET_MESH_get_peer(tunnel);

  size_t size = sizeof(struct ip6_udp) + ntohs(pkt->len) - 1 - sizeof(struct udp_pkt);

  struct ip6_udp* pkt6 = alloca(size);

  GNUNET_assert(pkt6 != NULL);

  new_ip6addr(pkt6->ip6_hdr.sadr, &other->hashPubKey, desc);

  GNUNET_log(GNUNET_ERROR_TYPE_DEBUG, "Relaying calc:%d gnu:%d udp:%d bytes!\n", size, ntohs(message->size), ntohs(pkt->len));

  pkt6->shdr.type = htons(GNUNET_MESSAGE_TYPE_VPN_HELPER);
  pkt6->shdr.size = htons(size);

  pkt6->tun.flags = 0;
  pkt6->tun.type = htons(0x86dd);

  pkt6->ip6_hdr.version = 6;
  pkt6->ip6_hdr.tclass_h = 0;
  pkt6->ip6_hdr.tclass_l = 0;
  pkt6->ip6_hdr.flowlbl = 0;
  pkt6->ip6_hdr.paylgth = pkt->len;
  pkt6->ip6_hdr.nxthdr = 0x11;
  pkt6->ip6_hdr.hoplmt = 0xff;

  {
    char* ipv6addr;
    GNUNET_assert(GNUNET_OK == GNUNET_CONFIGURATION_get_value_string(cfg, "vpn", "IPV6ADDR", &ipv6addr));
    inet_pton (AF_INET6, ipv6addr, pkt6->ip6_hdr.dadr);
    GNUNET_free(ipv6addr);
  }
  memcpy(&pkt6->udp_hdr, pkt, ntohs(pkt->len));

  GNUNET_HashCode* key = address_mapping_exists(pkt6->ip6_hdr.sadr);
  GNUNET_assert (key != NULL);

  struct map_entry *me = GNUNET_CONTAINER_multihashmap_get(hashmap, key);
  GNUNET_CONTAINER_heap_update_cost (heap, me->heap_node,
                                     GNUNET_TIME_absolute_get ().abs_value);

  GNUNET_free(key);

  GNUNET_assert (me != NULL);
  GNUNET_assert (me->desc.service_type & htonl(GNUNET_DNS_SERVICE_TYPE_UDP));
  if (!port_in_ports(me->desc.ports, pkt6->udp_hdr.spt) &&
      !testBit(me->additional_ports, ntohs(pkt6->udp_hdr.spt))) {
      add_additional_port(me, ntohs(pkt6->udp_hdr.spt));
  }

  pkt6->udp_hdr.crc = 0;
  uint32_t sum = 0;
  sum = calculate_checksum_update(sum, (uint16_t*)&pkt6->ip6_hdr.sadr, 16);
  sum = calculate_checksum_update(sum, (uint16_t*)&pkt6->ip6_hdr.dadr, 16);
  uint32_t tmp = (pkt6->udp_hdr.len & 0xffff);
  sum = calculate_checksum_update(sum, (uint16_t*)&tmp, 4);
  tmp = htons(((pkt6->ip6_hdr.nxthdr & 0x00ff)));
  sum = calculate_checksum_update(sum, (uint16_t*)&tmp, 4);

  sum = calculate_checksum_update(sum, (uint16_t*)&pkt6->udp_hdr, ntohs(pkt->len));
  pkt6->udp_hdr.crc = calculate_checksum_end(sum);

  write_to_helper(pkt6, size);

  return GNUNET_OK;
}

static int
receive_tcp_back (void *cls, struct GNUNET_MESH_Tunnel* tunnel,
		  void **tunnel_ctx,
		  const struct GNUNET_PeerIdentity *sender,
		  const struct GNUNET_MessageHeader *message,
		  const struct GNUNET_TRANSPORT_ATS_Information *atsi)
{
  GNUNET_HashCode *desc = (GNUNET_HashCode *) (message + 1);
  struct tcp_pkt *pkt = (struct tcp_pkt *) (desc + 1);
  const struct GNUNET_PeerIdentity* other = GNUNET_MESH_get_peer(tunnel);

  size_t pktlen = ntohs(message->size) - sizeof(struct GNUNET_MessageHeader) - sizeof(GNUNET_HashCode);
  size_t size = pktlen + sizeof(struct ip6_tcp) - 1;

  struct ip6_tcp* pkt6 = alloca(size);

  GNUNET_assert(pkt6 != NULL);

  new_ip6addr(pkt6->ip6_hdr.sadr, &other->hashPubKey, desc);

  pkt6->shdr.type = htons(GNUNET_MESSAGE_TYPE_VPN_HELPER);
  pkt6->shdr.size = htons(size);

  pkt6->tun.flags = 0;
  pkt6->tun.type = htons(0x86dd);

  pkt6->ip6_hdr.version = 6;
  pkt6->ip6_hdr.tclass_h = 0;
  pkt6->ip6_hdr.tclass_l = 0;
  pkt6->ip6_hdr.flowlbl = 0;
  pkt6->ip6_hdr.paylgth = htons(pktlen);
  pkt6->ip6_hdr.nxthdr = 0x06;
  pkt6->ip6_hdr.hoplmt = 0xff;

  {
    char* ipv6addr;
    GNUNET_assert(GNUNET_OK == GNUNET_CONFIGURATION_get_value_string(cfg, "vpn", "IPV6ADDR", &ipv6addr));
    inet_pton (AF_INET6, ipv6addr, pkt6->ip6_hdr.dadr);
    GNUNET_free(ipv6addr);
  }
  memcpy(&pkt6->tcp_hdr, pkt, pktlen);

  GNUNET_HashCode* key = address_mapping_exists(pkt6->ip6_hdr.sadr);
  GNUNET_assert (key != NULL);

  struct map_entry *me = GNUNET_CONTAINER_multihashmap_get(hashmap, key);
  GNUNET_CONTAINER_heap_update_cost (heap, me->heap_node,
                                     GNUNET_TIME_absolute_get ().abs_value);

  GNUNET_free(key);

  GNUNET_assert (me != NULL);
  GNUNET_assert (me->desc.service_type & htonl(GNUNET_DNS_SERVICE_TYPE_TCP));

  pkt6->tcp_hdr.crc = 0;
  uint32_t sum = 0;
  uint32_t tmp;
  sum =
    calculate_checksum_update (sum, (uint16_t *) & pkt6->ip6_hdr.sadr, 16);
  sum =
    calculate_checksum_update (sum, (uint16_t *) & pkt6->ip6_hdr.dadr, 16);
  tmp = htonl(pktlen);
  sum = calculate_checksum_update (sum, (uint16_t *) & tmp, 4);
  tmp = htonl (((pkt6->ip6_hdr.nxthdr & 0x000000ff)));
  sum = calculate_checksum_update (sum, (uint16_t *) & tmp, 4);

  sum =
    calculate_checksum_update (sum, (uint16_t *) & pkt6->tcp_hdr,
                               ntohs (pkt6->ip6_hdr.paylgth));
  pkt6->tcp_hdr.crc = calculate_checksum_end (sum);

  write_to_helper(pkt6, size);

  return GNUNET_OK;
}

/**
 * Main function that will be run by the scheduler.
 *
 * @param cls closure
 * @param args remaining command-line arguments
 * @param cfgfile name of the configuration file used (for saving, can be NULL!)
 * @param cfg_ configuration
 */
static void
run (void *cls,
     char *const *args,
     const char *cfgfile,
     const struct GNUNET_CONFIGURATION_Handle *cfg_)
{
    const static struct GNUNET_MESH_MessageHandler handlers[] = {
	  {receive_udp_back, GNUNET_MESSAGE_TYPE_SERVICE_UDP_BACK, 0},
	  {receive_tcp_back, GNUNET_MESSAGE_TYPE_SERVICE_TCP_BACK, 0},
	  {NULL, 0, 0}
    };
    mesh_handle = GNUNET_MESH_connect(cfg_,
				      NULL,
				      NULL,
                                      handlers,
                                      NULL);
    cfg = cfg_;
    restart_hijack = 0;
    hashmap = GNUNET_CONTAINER_multihashmap_create(65536);
    heap = GNUNET_CONTAINER_heap_create (GNUNET_CONTAINER_HEAP_ORDER_MIN);
    GNUNET_CONFIGURATION_get_value_number (cfg, "vpn", "MAX_MAPPINGg",
                                           &max_mappings);
    udp_connections = GNUNET_CONTAINER_multihashmap_create(65536);
    GNUNET_SCHEDULER_TaskIdentifier conn_task = GNUNET_SCHEDULER_add_now (connect_to_service_dns, NULL);
    GNUNET_SCHEDULER_add_after (conn_task, start_helper_and_schedule, NULL);
    GNUNET_SCHEDULER_add_delayed(GNUNET_TIME_UNIT_FOREVER_REL, &cleanup, cls);
}

/**
 * The main function to obtain template from gnunetd.
 *
 * @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) {
    static const struct GNUNET_GETOPT_CommandLineOption options[] = {
	GNUNET_GETOPT_OPTION_END
    };

    return (GNUNET_OK ==
	    GNUNET_PROGRAM_run (argc,
				argv,
				"gnunet-daemon-vpn",
				gettext_noop ("help text"),
				options, &run, NULL)) ? ret : 1;
}

/* end of gnunet-daemon-vpn.c */