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1/*
2 This file is part of GNUnet.
3 Copyright (C) 2010, 2012, 2017 Christian Grothoff
4
5 GNUnet is free software: you can redistribute it and/or modify it
6 under the terms of the GNU Affero General Public License as published
7 by the Free Software Foundation, either version 3 of the License,
8 or (at your option) any later version.
9
10 GNUnet is distributed in the hope that it will be useful, but
11 WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Affero General Public License for more details.
14
15 You should have received a copy of the GNU Affero General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>.
17
18 SPDX-License-Identifier: AGPL3.0-or-later
19 */
20/**
21 * @file pt/gnunet-daemon-pt.c
22 * @brief tool to manipulate DNS and VPN services to perform protocol translation (IPvX over GNUnet)
23 * @author Christian Grothoff
24 */
25#include "platform.h"
26#include "gnunet_util_lib.h"
27#include "gnunet_dns_service.h"
28#include "gnunet_dnsparser_lib.h"
29#include "gnunet_cadet_service.h"
30#include "gnunet_tun_lib.h"
31#include "gnunet_dht_service.h"
32#include "gnunet_vpn_service.h"
33#include "gnunet_statistics_service.h"
34#include "gnunet_applications.h"
35#include "block_dns.h"
36
37
38/**
39 * After how long do we time out if we could not get an IP from VPN or CADET?
40 */
41#define TIMEOUT GNUNET_TIME_UNIT_MINUTES
42
43/**
44 * How many bytes of payload do we allow at most for a DNS reply?
45 * Given that this is pretty much limited to loopback, we can be
46 * pretty high (Linux loopback defaults to 16k, most local UDP packets
47 * should survive up to 9k (NFS), so 8k should be pretty safe in
48 * general).
49 */
50#define MAX_DNS_SIZE (8 * 1024)
51
52/**
53 * How many channels do we open at most at the same time?
54 */
55#define MAX_OPEN_TUNNELS 4
56
57
58/**
59 * Which group of DNS records are we currently processing?
60 */
61enum RequestGroup
62{
63 /**
64 * DNS answers
65 */
66 ANSWERS = 0,
67
68 /**
69 * DNS authority records
70 */
71 AUTHORITY_RECORDS = 1,
72
73 /**
74 * DNS additional records
75 */
76 ADDITIONAL_RECORDS = 2,
77
78 /**
79 * We're done processing.
80 */
81 END = 3
82};
83
84
85/**
86 * Information tracked per DNS reply that we are processing.
87 */
88struct ReplyContext
89{
90 /**
91 * Handle to submit the final result.
92 */
93 struct GNUNET_DNS_RequestHandle *rh;
94
95 /**
96 * DNS packet that is being modified.
97 */
98 struct GNUNET_DNSPARSER_Packet *dns;
99
100 /**
101 * Active redirection request with the VPN.
102 */
103 struct GNUNET_VPN_RedirectionRequest *rr;
104
105 /**
106 * Record for which we have an active redirection request.
107 */
108 struct GNUNET_DNSPARSER_Record *rec;
109
110 /**
111 * Offset in the current record group that is being modified.
112 */
113 unsigned int offset;
114
115 /**
116 * Group that is being modified
117 */
118 enum RequestGroup group;
119};
120
121
122/**
123 * Handle to a peer that advertised that it is willing to serve
124 * as a DNS exit. We try to keep a few channels open and a few
125 * peers in reserve.
126 */
127struct CadetExit
128{
129 /**
130 * Kept in a DLL.
131 */
132 struct CadetExit *next;
133
134 /**
135 * Kept in a DLL.
136 */
137 struct CadetExit *prev;
138
139 /**
140 * Channel we use for DNS requests over CADET, NULL if we did
141 * not initialize a channel to this peer yet.
142 */
143 struct GNUNET_CADET_Channel *cadet_channel;
144
145 /**
146 * At what time did the peer's advertisement expire?
147 */
148 struct GNUNET_TIME_Absolute expiration;
149
150 /**
151 * Head of DLL of requests waiting for a response.
152 */
153 struct RequestContext *receive_queue_head;
154
155 /**
156 * Tail of DLL of requests waiting for a response.
157 */
158 struct RequestContext *receive_queue_tail;
159
160 /**
161 * Identity of the peer that is providing the exit for us.
162 */
163 struct GNUNET_PeerIdentity peer;
164
165 /**
166 * How many DNS requests did we transmit via this channel?
167 */
168 unsigned int num_transmitted;
169
170 /**
171 * How many DNS requests were answered via this channel?
172 */
173 unsigned int num_answered;
174
175 /**
176 * Size of the window, 0 if we are busy.
177 */
178 /* unsigned */ int idle;
179};
180
181
182/**
183 * State we keep for a request that is going out via CADET.
184 */
185struct RequestContext
186{
187 /**
188 * We keep these in a DLL.
189 */
190 struct RequestContext *next;
191
192 /**
193 * We keep these in a DLL.
194 */
195 struct RequestContext *prev;
196
197 /**
198 * Exit that was chosen for this request.
199 */
200 struct CadetExit *exit;
201
202 /**
203 * Handle for interaction with DNS service.
204 */
205 struct GNUNET_DNS_RequestHandle *rh;
206
207 /**
208 * Envelope with the request we are transmitting.
209 */
210 struct GNUNET_MQ_Envelope *env;
211
212 /**
213 * Task used to abort this operation with timeout.
214 */
215 struct GNUNET_SCHEDULER_Task *timeout_task;
216
217 /**
218 * Length of the request message that follows this struct.
219 */
220 uint16_t mlen;
221
222 /**
223 * ID of the original DNS request (used to match the reply).
224 */
225 uint16_t dns_id;
226};
227
228
229/**
230 * Head of DLL of cadet exits. Cadet exits with an open channel are
231 * always at the beginning (so we do not have to traverse the entire
232 * list to find them).
233 */
234static struct CadetExit *exit_head;
235
236/**
237 * Tail of DLL of cadet exits.
238 */
239static struct CadetExit *exit_tail;
240
241/**
242 * The handle to the configuration used throughout the process
243 */
244static const struct GNUNET_CONFIGURATION_Handle *cfg;
245
246/**
247 * The handle to the VPN
248 */
249static struct GNUNET_VPN_Handle *vpn_handle;
250
251/**
252 * The handle to the CADET service
253 */
254static struct GNUNET_CADET_Handle *cadet_handle;
255
256/**
257 * Statistics.
258 */
259static struct GNUNET_STATISTICS_Handle *stats;
260
261/**
262 * The handle to DNS post-resolution modifications.
263 */
264static struct GNUNET_DNS_Handle *dns_post_handle;
265
266/**
267 * The handle to DNS pre-resolution modifications.
268 */
269static struct GNUNET_DNS_Handle *dns_pre_handle;
270
271/**
272 * Handle to access the DHT.
273 */
274static struct GNUNET_DHT_Handle *dht;
275
276/**
277 * Our DHT GET operation to find DNS exits.
278 */
279static struct GNUNET_DHT_GetHandle *dht_get;
280
281/**
282 * Are we doing IPv4-pt?
283 */
284static int ipv4_pt;
285
286/**
287 * Are we doing IPv6-pt?
288 */
289static int ipv6_pt;
290
291/**
292 * Are we channeling DNS queries?
293 */
294static int dns_channel;
295
296/**
297 * Number of DNS exit peers we currently have in the cadet channel.
298 * Used to see if using the cadet channel makes any sense right now,
299 * as well as to decide if we should open new channels.
300 */
301static unsigned int dns_exit_available;
302
303
304/**
305 * We are short on cadet exits, try to open another one.
306 */
307static void
308try_open_exit (void);
309
310
311/**
312 * Compute the weight of the given exit. The higher the weight,
313 * the more likely it will be that the channel will be chosen.
314 * A weigt of zero means that we should close the channel as it
315 * is so bad, that we should not use it.
316 *
317 * @param exit exit to calculate the weight for
318 * @return weight of the channel
319 */
320static uint32_t
321get_channel_weight (struct CadetExit *exit)
322{
323 uint32_t dropped;
324 uint32_t drop_percent;
325 uint32_t good_percent;
326
327 GNUNET_assert (exit->num_transmitted >= exit->num_answered);
328 dropped = exit->num_transmitted - exit->num_answered;
329 if (exit->num_transmitted > 0)
330 drop_percent = (uint32_t) ((100LL * dropped) / exit->num_transmitted);
331 else
332 drop_percent = 50; /* no data */
333 if ((exit->num_transmitted > 20) &&
334 (drop_percent > 25))
335 return 0; /* statistically significant, and > 25% loss, die */
336 good_percent = 100 - drop_percent;
337 GNUNET_assert (0 != good_percent);
338 if (UINT32_MAX / good_percent / good_percent < exit->num_transmitted)
339 return UINT32_MAX; /* formula below would overflow */
340 return 1 + good_percent * good_percent * exit->num_transmitted;
341}
342
343
344/**
345 * Choose a cadet exit for a DNS request. We try to use a channel
346 * that is reliable and currently available. All existing
347 * channels are given a base weight of 1, plus a score relating
348 * to the total number of queries answered in relation to the
349 * total number of queries we sent to that channel. That
350 * score is doubled if the channel is currently idle.
351 *
352 * @return NULL if no exit is known, otherwise the
353 * exit that we should use to queue a message with
354 */
355static struct CadetExit *
356choose_exit ()
357{
358 struct CadetExit *pos;
359 uint64_t total_transmitted;
360 uint64_t selected_offset;
361 uint32_t channel_weight;
362
363 total_transmitted = 0;
364 for (pos = exit_head; NULL != pos; pos = pos->next)
365 {
366 if (NULL == pos->cadet_channel)
367 break;
368 channel_weight = get_channel_weight (pos);
369 total_transmitted += channel_weight;
370 /* double weight for idle channels */
371 if (0 != pos->idle)
372 total_transmitted += channel_weight;
373 }
374 if (0 == total_transmitted)
375 {
376 /* no channels available, or only a very bad one... */
377 return exit_head;
378 }
379 selected_offset = GNUNET_CRYPTO_random_u64 (GNUNET_CRYPTO_QUALITY_WEAK,
380 total_transmitted);
381 total_transmitted = 0;
382 for (pos = exit_head; NULL != pos; pos = pos->next)
383 {
384 if (NULL == pos->cadet_channel)
385 break;
386 channel_weight = get_channel_weight (pos);
387 total_transmitted += channel_weight;
388 /* double weight for idle channels */
389 if (0 != pos->idle)
390 total_transmitted += channel_weight;
391 if (total_transmitted > selected_offset)
392 return pos;
393 }
394 GNUNET_break (0);
395 return NULL;
396}
397
398
399/**
400 * We're done modifying all records in the response. Submit the reply
401 * and free the resources of the rc.
402 *
403 * @param rc context to process
404 */
405static void
406finish_request (struct ReplyContext *rc)
407{
408 char *buf;
409 size_t buf_len;
410
411 if (GNUNET_SYSERR ==
412 GNUNET_DNSPARSER_pack (rc->dns,
413 MAX_DNS_SIZE,
414 &buf,
415 &buf_len))
416 {
417 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
418 _ ("Failed to pack DNS request. Dropping.\n"));
419 GNUNET_DNS_request_drop (rc->rh);
420 }
421 else
422 {
423 GNUNET_STATISTICS_update (stats,
424 gettext_noop ("# DNS requests mapped to VPN"),
425 1, GNUNET_NO);
426 GNUNET_DNS_request_answer (rc->rh,
427 buf_len,
428 buf);
429 GNUNET_free (buf);
430 }
431 GNUNET_DNSPARSER_free_packet (rc->dns);
432 GNUNET_free (rc);
433}
434
435
436/**
437 * Process the next record of the given request context.
438 * When done, submit the reply and free the resources of
439 * the rc.
440 *
441 * @param rc context to process
442 */
443static void
444submit_request (struct ReplyContext *rc);
445
446
447/**
448 * Callback invoked from the VPN service once a redirection is
449 * available. Provides the IP address that can now be used to
450 * reach the requested destination. We substitute the active
451 * record and then continue with 'submit_request' to look at
452 * the other records.
453 *
454 * @param cls our `struct ReplyContext`
455 * @param af address family, AF_INET or AF_INET6; AF_UNSPEC on error;
456 * will match 'result_af' from the request
457 * @param address IP address (struct in_addr or struct in_addr6, depending on 'af')
458 * that the VPN allocated for the redirection;
459 * traffic to this IP will now be redirected to the
460 * specified target peer; NULL on error
461 */
462static void
463vpn_allocation_callback (void *cls,
464 int af,
465 const void *address)
466{
467 struct ReplyContext *rc = cls;
468
469 rc->rr = NULL;
470 if (af == AF_UNSPEC)
471 {
472 GNUNET_DNS_request_drop (rc->rh);
473 GNUNET_DNSPARSER_free_packet (rc->dns);
474 GNUNET_free (rc);
475 return;
476 }
477 GNUNET_STATISTICS_update (stats,
478 gettext_noop ("# DNS records modified"),
479 1,
480 GNUNET_NO);
481 switch (rc->rec->type)
482 {
483 case GNUNET_DNSPARSER_TYPE_A:
484 GNUNET_assert (AF_INET == af);
485 GNUNET_memcpy (rc->rec->data.raw.data,
486 address,
487 sizeof(struct in_addr));
488 break;
489
490 case GNUNET_DNSPARSER_TYPE_AAAA:
491 GNUNET_assert (AF_INET6 == af);
492 GNUNET_memcpy (rc->rec->data.raw.data,
493 address,
494 sizeof(struct in6_addr));
495 break;
496
497 default:
498 GNUNET_assert (0);
499 return;
500 }
501 rc->rec = NULL;
502 submit_request (rc);
503}
504
505
506/**
507 * Modify the given DNS record by asking VPN to create a channel
508 * to the given address. When done, continue with submitting
509 * other records from the request context ('submit_request' is
510 * our continuation).
511 *
512 * @param rc context to process
513 * @param rec record to modify
514 */
515static void
516modify_address (struct ReplyContext *rc,
517 struct GNUNET_DNSPARSER_Record *rec)
518{
519 int af;
520
521 switch (rec->type)
522 {
523 case GNUNET_DNSPARSER_TYPE_A:
524 af = AF_INET;
525 GNUNET_assert (rec->data.raw.data_len == sizeof(struct in_addr));
526 break;
527
528 case GNUNET_DNSPARSER_TYPE_AAAA:
529 af = AF_INET6;
530 GNUNET_assert (rec->data.raw.data_len == sizeof(struct in6_addr));
531 break;
532
533 default:
534 GNUNET_assert (0);
535 return;
536 }
537 rc->rec = rec;
538 rc->rr = GNUNET_VPN_redirect_to_ip (vpn_handle,
539 af,
540 af,
541 rec->data.raw.data,
542 GNUNET_TIME_relative_to_absolute (
543 TIMEOUT),
544 &vpn_allocation_callback,
545 rc);
546}
547
548
549/**
550 * Process the next record of the given request context.
551 * When done, submit the reply and free the resources of
552 * the rc.
553 *
554 * @param rc context to process
555 */
556static void
557submit_request (struct ReplyContext *rc)
558{
559 struct GNUNET_DNSPARSER_Record *ra;
560 unsigned int ra_len;
561 unsigned int i;
562
563 while (1)
564 {
565 switch (rc->group)
566 {
567 case ANSWERS:
568 ra = rc->dns->answers;
569 ra_len = rc->dns->num_answers;
570 break;
571
572 case AUTHORITY_RECORDS:
573 ra = rc->dns->authority_records;
574 ra_len = rc->dns->num_authority_records;
575 break;
576
577 case ADDITIONAL_RECORDS:
578 ra = rc->dns->additional_records;
579 ra_len = rc->dns->num_additional_records;
580 break;
581
582 case END:
583 finish_request (rc);
584 return;
585
586 default:
587 GNUNET_assert (0);
588 }
589 for (i = rc->offset; i < ra_len; i++)
590 {
591 switch (ra[i].type)
592 {
593 case GNUNET_DNSPARSER_TYPE_A:
594 if (ipv4_pt)
595 {
596 rc->offset = i + 1;
597 modify_address (rc,
598 &ra[i]);
599 return;
600 }
601 break;
602
603 case GNUNET_DNSPARSER_TYPE_AAAA:
604 if (ipv6_pt)
605 {
606 rc->offset = i + 1;
607 modify_address (rc,
608 &ra[i]);
609 return;
610 }
611 break;
612 }
613 }
614 rc->group++;
615 }
616}
617
618
619/**
620 * Test if any of the given records need protocol-translation work.
621 *
622 * @param ra array of records
623 * @param ra_len number of entries in @a ra
624 * @return #GNUNET_YES if any of the given records require protocol-translation
625 */
626static int
627work_test (const struct GNUNET_DNSPARSER_Record *ra,
628 unsigned int ra_len)
629{
630 unsigned int i;
631
632 for (i = 0; i < ra_len; i++)
633 {
634 switch (ra[i].type)
635 {
636 case GNUNET_DNSPARSER_TYPE_A:
637 if (ipv4_pt)
638 return GNUNET_YES;
639 break;
640
641 case GNUNET_DNSPARSER_TYPE_AAAA:
642 if (ipv6_pt)
643 return GNUNET_YES;
644 break;
645 }
646 }
647 return GNUNET_NO;
648}
649
650
651/**
652 * This function is called AFTER we got an IP address for a
653 * DNS request. Now, the PT daemon has the chance to substitute
654 * the IP address with one from the VPN range to channel requests
655 * destined for this IP address via VPN and CADET.
656 *
657 * @param cls closure
658 * @param rh request handle to user for reply
659 * @param request_length number of bytes in request
660 * @param request udp payload of the DNS request
661 */
662static void
663dns_post_request_handler (void *cls,
664 struct GNUNET_DNS_RequestHandle *rh,
665 size_t request_length,
666 const char *request)
667{
668 struct GNUNET_DNSPARSER_Packet *dns;
669 struct ReplyContext *rc;
670 int work;
671
672 GNUNET_STATISTICS_update (stats,
673 gettext_noop ("# DNS replies intercepted"),
674 1, GNUNET_NO);
675 dns = GNUNET_DNSPARSER_parse (request,
676 request_length);
677 if (NULL == dns)
678 {
679 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
680 _ ("Failed to parse DNS request. Dropping.\n"));
681 GNUNET_DNS_request_drop (rh);
682 return;
683 }
684 work = GNUNET_NO;
685 work |= work_test (dns->answers,
686 dns->num_answers);
687 work |= work_test (dns->authority_records,
688 dns->num_authority_records);
689 work |= work_test (dns->additional_records,
690 dns->num_additional_records);
691 if (! work)
692 {
693 GNUNET_DNS_request_forward (rh);
694 GNUNET_DNSPARSER_free_packet (dns);
695 return;
696 }
697 rc = GNUNET_new (struct ReplyContext);
698 rc->rh = rh;
699 rc->dns = dns;
700 rc->offset = 0;
701 rc->group = ANSWERS;
702 submit_request (rc);
703}
704
705
706/**
707 * Task run if the time to answer a DNS request via CADET is over.
708 *
709 * @param cls the `struct RequestContext` to abort
710 */
711static void
712timeout_request (void *cls)
713{
714 struct RequestContext *rc = cls;
715 struct CadetExit *exit = rc->exit;
716
717 GNUNET_STATISTICS_update (stats,
718 gettext_noop ("# DNS requests dropped (timeout)"),
719 1,
720 GNUNET_NO);
721 GNUNET_DNS_request_drop (rc->rh);
722 GNUNET_free (rc);
723 if ((0 == get_channel_weight (exit)) &&
724 (NULL == exit->receive_queue_head))
725 {
726 /* this straw broke the camel's back: this channel now has
727 such a low score that it will not be used; close it! */
728 GNUNET_CADET_channel_destroy (exit->cadet_channel);
729 exit->cadet_channel = NULL;
730 GNUNET_CONTAINER_DLL_remove (exit_head,
731 exit_tail,
732 exit);
733 GNUNET_CONTAINER_DLL_insert_tail (exit_head,
734 exit_tail,
735 exit);
736 /* go back to semi-innocent: mark as not great, but
737 avoid a prohibitively negative score (see
738 #get_channel_weight(), which checks for a certain
739 minimum number of transmissions before making
740 up an opinion) */exit->num_transmitted = 5;
741 exit->num_answered = 0;
742 dns_exit_available--;
743 /* now try to open an alternative exit */
744 try_open_exit ();
745 }
746}
747
748
749/**
750 * This function is called *before* the DNS request has been
751 * given to a "local" DNS resolver. Channeling for DNS requests
752 * was enabled, so we now need to send the request via some CADET
753 * channel to a DNS EXIT for resolution.
754 *
755 * @param cls closure
756 * @param rh request handle to user for reply
757 * @param request_length number of bytes in request
758 * @param request udp payload of the DNS request
759 */
760static void
761dns_pre_request_handler (void *cls,
762 struct GNUNET_DNS_RequestHandle *rh,
763 size_t request_length,
764 const char *request)
765{
766 struct RequestContext *rc;
767 struct GNUNET_MQ_Envelope *env;
768 struct GNUNET_MessageHeader *hdr;
769 struct GNUNET_TUN_DnsHeader dns;
770 struct CadetExit *exit;
771
772 GNUNET_STATISTICS_update (stats,
773 gettext_noop ("# DNS requests intercepted"),
774 1, GNUNET_NO);
775 if (0 == dns_exit_available)
776 {
777 GNUNET_STATISTICS_update (stats,
778 gettext_noop (
779 "# DNS requests dropped (DNS cadet channel down)"),
780 1, GNUNET_NO);
781 GNUNET_DNS_request_drop (rh);
782 return;
783 }
784 if (request_length < sizeof(dns))
785 {
786 GNUNET_STATISTICS_update (stats,
787 gettext_noop (
788 "# DNS requests dropped (malformed)"),
789 1, GNUNET_NO);
790 GNUNET_DNS_request_drop (rh);
791 return;
792 }
793 exit = choose_exit ();
794 GNUNET_assert (NULL != exit);
795 GNUNET_assert (NULL != exit->cadet_channel);
796
797 env = GNUNET_MQ_msg_extra (hdr,
798 request_length,
799 GNUNET_MESSAGE_TYPE_VPN_DNS_TO_INTERNET);
800 GNUNET_memcpy (&hdr[1],
801 request,
802 request_length);
803 rc = GNUNET_new (struct RequestContext);
804 rc->exit = exit;
805 rc->rh = rh;
806 rc->timeout_task = GNUNET_SCHEDULER_add_delayed (TIMEOUT,
807 &timeout_request,
808 rc);
809 GNUNET_memcpy (&dns,
810 request,
811 sizeof(dns));
812 rc->dns_id = dns.id;
813 rc->env = env;
814 GNUNET_CONTAINER_DLL_remove (exit->receive_queue_head,
815 exit->receive_queue_tail,
816 rc);
817 if (0 < exit->idle)
818 exit->idle--;
819 exit->num_transmitted++;
820 GNUNET_MQ_send (GNUNET_CADET_get_mq (exit->cadet_channel),
821 GNUNET_MQ_env_copy (env));
822}
823
824
825GNUNET_NETWORK_STRUCT_BEGIN
826
827/**
828 * Message with a DNS response.
829 */
830struct DnsResponseMessage
831{
832 /**
833 * GNUnet header, of type #GNUNET_MESSAGE_TYPE_VPN_DNS_FROM_INTERNET
834 */
835 struct GNUNET_MessageHeader header;
836
837 /**
838 * DNS header.
839 */
840 struct GNUNET_TUN_DnsHeader dns;
841
842 /* Followed by more DNS payload */
843};
844
845GNUNET_NETWORK_STRUCT_END
846
847/**
848 * Process a request via cadet to perform a DNS query.
849 *
850 * @param cls the `struct CadetExit` which got the message
851 * @param msg the actual message
852 * @return #GNUNET_OK to keep the connection open,
853 * #GNUNET_SYSERR to close it (signal serious error)
854 */
855static int
856check_dns_response (void *cls,
857 const struct DnsResponseMessage *msg)
858{
859 return GNUNET_OK; /* all OK */
860}
861
862
863/**
864 * Process a request via cadet to perform a DNS query.
865 *
866 * @param cls the `struct CadetExit` which got the message
867 * @param msg the actual message
868 */
869static void
870handle_dns_response (void *cls,
871 const struct DnsResponseMessage *msg)
872{
873 struct CadetExit *exit = cls;
874 size_t mlen;
875 struct RequestContext *rc;
876
877 mlen = ntohs (msg->header.size) - sizeof(*msg);
878 for (rc = exit->receive_queue_head; NULL != rc; rc = rc->next)
879 {
880 if (msg->dns.id == rc->dns_id)
881 {
882 GNUNET_STATISTICS_update (stats,
883 gettext_noop ("# DNS replies received"),
884 1,
885 GNUNET_NO);
886 GNUNET_DNS_request_answer (rc->rh,
887 mlen + sizeof(struct GNUNET_TUN_DnsHeader),
888 (const void *) &msg->dns);
889 GNUNET_CONTAINER_DLL_remove (exit->receive_queue_head,
890 exit->receive_queue_tail,
891 rc);
892 GNUNET_SCHEDULER_cancel (rc->timeout_task);
893 GNUNET_MQ_discard (rc->env);
894 GNUNET_free (rc);
895 exit->num_answered++;
896 return;
897 }
898 }
899 GNUNET_STATISTICS_update (stats,
900 gettext_noop ("# DNS replies dropped (too late?)"),
901 1, GNUNET_NO);
902}
903
904
905/**
906 * Abort all pending DNS requests with the given cadet exit.
907 *
908 * @param exit cadet exit to abort requests for
909 */
910static void
911abort_all_requests (struct CadetExit *exit)
912{
913 struct RequestContext *rc;
914
915 while (NULL != (rc = exit->receive_queue_head))
916 {
917 GNUNET_CONTAINER_DLL_remove (exit->receive_queue_head,
918 exit->receive_queue_tail,
919 rc);
920 GNUNET_DNS_request_drop (rc->rh);
921 GNUNET_SCHEDULER_cancel (rc->timeout_task);
922 GNUNET_MQ_discard (rc->env);
923 GNUNET_free (rc);
924 }
925}
926
927
928/**
929 * Function scheduled as very last function, cleans up after us
930 *
931 * @param cls closure, NULL
932 */
933static void
934cleanup (void *cls)
935{
936 struct CadetExit *exit;
937
938 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
939 "Protocol translation daemon is shutting down now\n");
940 if (NULL != vpn_handle)
941 {
942 GNUNET_VPN_disconnect (vpn_handle);
943 vpn_handle = NULL;
944 }
945 while (NULL != (exit = exit_head))
946 {
947 GNUNET_CONTAINER_DLL_remove (exit_head,
948 exit_tail,
949 exit);
950 if (NULL != exit->cadet_channel)
951 {
952 GNUNET_CADET_channel_destroy (exit->cadet_channel);
953 exit->cadet_channel = NULL;
954 }
955 abort_all_requests (exit);
956 GNUNET_free (exit);
957 }
958 if (NULL != cadet_handle)
959 {
960 GNUNET_CADET_disconnect (cadet_handle);
961 cadet_handle = NULL;
962 }
963 if (NULL != dns_post_handle)
964 {
965 GNUNET_DNS_disconnect (dns_post_handle);
966 dns_post_handle = NULL;
967 }
968 if (NULL != dns_pre_handle)
969 {
970 GNUNET_DNS_disconnect (dns_pre_handle);
971 dns_pre_handle = NULL;
972 }
973 if (NULL != stats)
974 {
975 GNUNET_STATISTICS_destroy (stats, GNUNET_YES);
976 stats = NULL;
977 }
978 if (NULL != dht_get)
979 {
980 GNUNET_DHT_get_stop (dht_get);
981 dht_get = NULL;
982 }
983 if (NULL != dht)
984 {
985 GNUNET_DHT_disconnect (dht);
986 dht = NULL;
987 }
988}
989
990
991/**
992 * Function called whenever a channel is destroyed. Should clean up
993 * the associated state and attempt to build a new one.
994 *
995 * It must NOT call #GNUNET_CADET_channel_destroy on the channel.
996 *
997 * @param cls closure (the `struct CadetExit` set from #GNUNET_CADET_connect)
998 * @param channel connection to the other end (henceforth invalid)
999 * @param channel_ctx place where local state associated
1000 * with the channel is stored
1001 */
1002static void
1003cadet_channel_end_cb (void *cls,
1004 const struct GNUNET_CADET_Channel *channel)
1005{
1006 struct CadetExit *exit = cls;
1007 struct CadetExit *alt;
1008 struct RequestContext *rc;
1009
1010 exit->cadet_channel = NULL;
1011 dns_exit_available--;
1012 /* open alternative channels */
1013 /* our channel is now closed, move our requests to an alternative
1014 channel */
1015 alt = choose_exit ();
1016 while (NULL != (rc = exit->receive_queue_head))
1017 {
1018 GNUNET_CONTAINER_DLL_remove (exit->receive_queue_head,
1019 exit->receive_queue_tail,
1020 rc);
1021 rc->exit = alt;
1022 GNUNET_CONTAINER_DLL_insert (alt->receive_queue_head,
1023 alt->receive_queue_tail,
1024 rc);
1025 GNUNET_MQ_send (GNUNET_CADET_get_mq (alt->cadet_channel),
1026 GNUNET_MQ_env_copy (rc->env));
1027 }
1028 try_open_exit ();
1029}
1030
1031
1032/**
1033 * Function called whenever a channel has excess capacity.
1034 *
1035 * @param cls the `struct CadetExit`
1036 * @param channel connection to the other end
1037 * @param window_size how much capacity do we have
1038 */
1039static void
1040channel_idle_notify_cb (void *cls,
1041 const struct GNUNET_CADET_Channel *channel,
1042 int window_size)
1043{
1044 struct CadetExit *pos = cls;
1045
1046 pos->idle = window_size;
1047}
1048
1049
1050/**
1051 * We are short on cadet exits, try to open another one.
1052 */
1053static void
1054try_open_exit ()
1055{
1056 struct CadetExit *pos;
1057 uint32_t candidate_count;
1058 uint32_t candidate_selected;
1059 struct GNUNET_HashCode port;
1060
1061 GNUNET_CRYPTO_hash (GNUNET_APPLICATION_PORT_INTERNET_RESOLVER,
1062 strlen (GNUNET_APPLICATION_PORT_INTERNET_RESOLVER),
1063 &port);
1064 candidate_count = 0;
1065 for (pos = exit_head; NULL != pos; pos = pos->next)
1066 if (NULL == pos->cadet_channel)
1067 candidate_count++;
1068 if (0 == candidate_count)
1069 {
1070 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
1071 "No DNS exits available yet.\n");
1072 return;
1073 }
1074 candidate_selected = GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_WEAK,
1075 candidate_count);
1076 candidate_count = 0;
1077 for (pos = exit_head; NULL != pos; pos = pos->next)
1078 if (NULL == pos->cadet_channel)
1079 {
1080 candidate_count++;
1081 if (candidate_selected < candidate_count)
1082 {
1083 struct GNUNET_MQ_MessageHandler cadet_handlers[] = {
1084 GNUNET_MQ_hd_var_size (dns_response,
1085 GNUNET_MESSAGE_TYPE_VPN_DNS_FROM_INTERNET,
1086 struct DnsResponseMessage,
1087 pos),
1088 GNUNET_MQ_handler_end ()
1089 };
1090
1091
1092 /* move to the head of the DLL */
1093 pos->cadet_channel
1094 = GNUNET_CADET_channel_create (cadet_handle,
1095 pos,
1096 &pos->peer,
1097 &port,
1098 &channel_idle_notify_cb,
1099 &cadet_channel_end_cb,
1100 cadet_handlers);
1101 if (NULL == pos->cadet_channel)
1102 {
1103 GNUNET_break (0);
1104 continue;
1105 }
1106 GNUNET_CONTAINER_DLL_remove (exit_head,
1107 exit_tail,
1108 pos);
1109 GNUNET_CONTAINER_DLL_insert (exit_head,
1110 exit_tail,
1111 pos);
1112 dns_exit_available++;
1113 return;
1114 }
1115 }
1116 GNUNET_assert (NULL == exit_head);
1117}
1118
1119
1120/**
1121 * Function called whenever we find an advertisement for a
1122 * DNS exit in the DHT. If we don't have a cadet channel,
1123 * we should build one; otherwise, we should save the
1124 * advertisement for later use.
1125 *
1126 * @param cls closure
1127 * @param exp when will this value expire
1128 * @param key key of the result
1129 * @param get_path peers on reply path (or NULL if not recorded)
1130 * [0] = datastore's first neighbor, [length - 1] = local peer
1131 * @param get_path_length number of entries in @a get_path
1132 * @param put_path peers on the PUT path (or NULL if not recorded)
1133 * [0] = origin, [length - 1] = datastore
1134 * @param put_path_length number of entries in @a put_path
1135 * @param type type of the result
1136 * @param size number of bytes in @a data
1137 * @param data pointer to the result data
1138 */
1139static void
1140handle_dht_result (void *cls,
1141 struct GNUNET_TIME_Absolute exp,
1142 const struct GNUNET_HashCode *key,
1143 const struct GNUNET_PeerIdentity *get_path,
1144 unsigned int get_path_length,
1145 const struct GNUNET_PeerIdentity *put_path,
1146 unsigned int put_path_length,
1147 enum GNUNET_BLOCK_Type type,
1148 size_t size, const void *data)
1149{
1150 const struct GNUNET_DNS_Advertisement *ad;
1151 struct CadetExit *exit;
1152
1153 if (sizeof(struct GNUNET_DNS_Advertisement) != size)
1154 {
1155 GNUNET_break (0);
1156 return;
1157 }
1158 ad = data;
1159 for (exit = exit_head; NULL != exit; exit = exit->next)
1160 if (0 == GNUNET_memcmp (&ad->peer,
1161 &exit->peer))
1162 break;
1163 if (NULL == exit)
1164 {
1165 exit = GNUNET_new (struct CadetExit);
1166 exit->peer = ad->peer;
1167 /* channel is closed, so insert at the end */
1168 GNUNET_CONTAINER_DLL_insert_tail (exit_head,
1169 exit_tail,
1170 exit);
1171 }
1172 exit->expiration = GNUNET_TIME_absolute_max (exit->expiration,
1173 GNUNET_TIME_absolute_ntoh (
1174 ad->expiration_time));
1175 if (dns_exit_available < MAX_OPEN_TUNNELS)
1176 try_open_exit ();
1177}
1178
1179
1180/**
1181 * @brief Main function that will be run by the scheduler.
1182 *
1183 * @param cls closure
1184 * @param args remaining command-line arguments
1185 * @param cfgfile name of the configuration file used (for saving, can be NULL!)
1186 * @param cfg_ configuration
1187 */
1188static void
1189run (void *cls, char *const *args GNUNET_UNUSED,
1190 const char *cfgfile GNUNET_UNUSED,
1191 const struct GNUNET_CONFIGURATION_Handle *cfg_)
1192{
1193 struct GNUNET_HashCode dns_key;
1194
1195 cfg = cfg_;
1196 stats = GNUNET_STATISTICS_create ("pt",
1197 cfg);
1198 ipv4_pt = GNUNET_CONFIGURATION_get_value_yesno (cfg,
1199 "pt",
1200 "TUNNEL_IPV4");
1201 ipv6_pt = GNUNET_CONFIGURATION_get_value_yesno (cfg,
1202 "pt",
1203 "TUNNEL_IPV6");
1204 dns_channel = GNUNET_CONFIGURATION_get_value_yesno (cfg,
1205 "pt",
1206 "TUNNEL_DNS");
1207 if (! (ipv4_pt || ipv6_pt || dns_channel))
1208 {
1209 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
1210 _ ("No useful service enabled. Exiting.\n"));
1211 GNUNET_SCHEDULER_shutdown ();
1212 return;
1213 }
1214 GNUNET_SCHEDULER_add_shutdown (&cleanup, cls);
1215 if (ipv4_pt || ipv6_pt)
1216 {
1217 dns_post_handle
1218 = GNUNET_DNS_connect (cfg,
1219 GNUNET_DNS_FLAG_POST_RESOLUTION,
1220 &dns_post_request_handler,
1221 NULL);
1222 if (NULL == dns_post_handle)
1223 {
1224 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
1225 _ ("Failed to connect to %s service. Exiting.\n"),
1226 "DNS");
1227 GNUNET_SCHEDULER_shutdown ();
1228 return;
1229 }
1230 vpn_handle = GNUNET_VPN_connect (cfg);
1231 if (NULL == vpn_handle)
1232 {
1233 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
1234 _ ("Failed to connect to %s service. Exiting.\n"),
1235 "VPN");
1236 GNUNET_SCHEDULER_shutdown ();
1237 return;
1238 }
1239 }
1240 if (dns_channel)
1241 {
1242 dns_pre_handle
1243 = GNUNET_DNS_connect (cfg,
1244 GNUNET_DNS_FLAG_PRE_RESOLUTION,
1245 &dns_pre_request_handler,
1246 NULL);
1247 if (NULL == dns_pre_handle)
1248 {
1249 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
1250 _ ("Failed to connect to %s service. Exiting.\n"),
1251 "DNS");
1252 GNUNET_SCHEDULER_shutdown ();
1253 return;
1254 }
1255 cadet_handle = GNUNET_CADET_connect (cfg);
1256 if (NULL == cadet_handle)
1257 {
1258 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
1259 _ ("Failed to connect to %s service. Exiting.\n"),
1260 "CADET");
1261 GNUNET_SCHEDULER_shutdown ();
1262 return;
1263 }
1264 dht = GNUNET_DHT_connect (cfg, 1);
1265 if (NULL == dht)
1266 {
1267 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
1268 _ ("Failed to connect to %s service. Exiting.\n"),
1269 "DHT");
1270 GNUNET_SCHEDULER_shutdown ();
1271 return;
1272 }
1273 GNUNET_CRYPTO_hash ("dns",
1274 strlen ("dns"),
1275 &dns_key);
1276 dht_get = GNUNET_DHT_get_start (dht,
1277 GNUNET_BLOCK_TYPE_DNS,
1278 &dns_key,
1279 1,
1280 GNUNET_DHT_RO_DEMULTIPLEX_EVERYWHERE,
1281 NULL, 0,
1282 &handle_dht_result,
1283 NULL);
1284 }
1285}
1286
1287
1288/**
1289 * The main function
1290 *
1291 * @param argc number of arguments from the command line
1292 * @param argv command line arguments
1293 * @return 0 ok, 1 on error
1294 */
1295int
1296main (int argc,
1297 char *const *argv)
1298{
1299 static const struct GNUNET_GETOPT_CommandLineOption options[] = {
1300 GNUNET_GETOPT_OPTION_END
1301 };
1302 int ret;
1303
1304 if (GNUNET_OK != GNUNET_STRINGS_get_utf8_args (argc,
1305 argv,
1306 &argc,
1307 &argv))
1308 return 2;
1309 ret = (GNUNET_OK ==
1310 GNUNET_PROGRAM_run (argc,
1311 argv,
1312 "gnunet-daemon-pt",
1313 gettext_noop (
1314 "Daemon to run to perform IP protocol translation to GNUnet"),
1315 options,
1316 &run,
1317 NULL))
1318 ? 0
1319 : 1;
1320 GNUNET_free_nz ((void *) argv);
1321 return ret;
1322}
1323
1324
1325/* end of gnunet-daemon-pt.c */