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diff --git a/src/service/util/gnunet-service-resolver.c b/src/service/util/gnunet-service-resolver.c
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1/*
2 This file is part of GNUnet.
3 Copyright (C) 2007-2016 GNUnet e.V.
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/**
22 * @file util/gnunet-service-resolver.c
23 * @brief code to do DNS resolution
24 * @author Christian Grothoff
25 */
26
27#include "platform.h"
28#include "gnunet_util_lib.h"
29#include "gnunet_protocols.h"
30#include "gnunet_statistics_service.h"
31#include "../../lib/util/resolver.h"
32
33
34/**
35 * How long do we wait for DNS answers?
36 */
37#define DNS_TIMEOUT GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS, 30)
38
39/**
40 * Maximum number of hostnames we cache results for.
41 */
42#define MAX_CACHE 1024
43
44/**
45 * Entry in list of cached DNS records for a hostname.
46 */
47struct RecordListEntry
48{
49 /**
50 * This is a doubly linked list.
51 */
52 struct RecordListEntry *next;
53
54 /**
55 * This is a doubly linked list.
56 */
57 struct RecordListEntry *prev;
58
59 /**
60 * Cached data.
61 */
62 struct GNUNET_DNSPARSER_Record *record;
63};
64
65
66/**
67 * A cached DNS lookup result.
68 */
69struct ResolveCache
70{
71 /**
72 * This is a doubly linked list.
73 */
74 struct ResolveCache *next;
75
76 /**
77 * This is a doubly linked list.
78 */
79 struct ResolveCache *prev;
80
81 /**
82 * Which hostname is this cache for?
83 */
84 char *hostname;
85
86 /**
87 * head of a double linked list containing the lookup results
88 */
89 struct RecordListEntry *records_head;
90
91 /**
92 * tail of a double linked list containing the lookup results
93 */
94 struct RecordListEntry *records_tail;
95};
96
97
98/**
99 * Information about pending lookups.
100 */
101struct ActiveLookup
102{
103 /**
104 * Stored in a DLL.
105 */
106 struct ActiveLookup *next;
107
108 /**
109 * Stored in a DLL.
110 */
111 struct ActiveLookup *prev;
112
113 /**
114 * The client that queried the records contained in this cache entry.
115 */
116 struct GNUNET_SERVICE_Client *client;
117
118 /**
119 * handle for cancelling a request
120 */
121 struct GNUNET_DNSSTUB_RequestSocket *resolve_handle;
122
123 /**
124 * handle for the resolution timeout task
125 */
126 struct GNUNET_SCHEDULER_Task *timeout_task;
127
128 /**
129 * Which hostname are we resolving?
130 */
131 char *hostname;
132
133 /**
134 * If @a record_type is #GNUNET_DNSPARSER_TYPE_ALL, did we go again
135 * for the AAAA records yet?
136 */
137 int did_aaaa;
138
139 /**
140 * type of queried DNS record
141 */
142 uint16_t record_type;
143
144 /**
145 * Unique request ID of a client if a query for this hostname/record_type
146 * is currently pending, undefined otherwise.
147 */
148 uint32_t client_request_id;
149
150 /**
151 * Unique DNS request ID of a client if a query for this hostname/record_type
152 * is currently pending, undefined otherwise.
153 */
154 uint16_t dns_id;
155};
156
157
158/**
159 * Start of the linked list of cached DNS lookup results.
160 */
161static struct ResolveCache *cache_head;
162
163/**
164 * Tail of the linked list of cached DNS lookup results.
165 */
166static struct ResolveCache *cache_tail;
167
168/**
169 * Head of the linked list of DNS lookup results from /etc/hosts.
170 */
171static struct ResolveCache *hosts_head;
172
173/**
174 * Tail of the linked list of DNS lookup results from /etc/hosts.
175 */
176static struct ResolveCache *hosts_tail;
177
178/**
179 * Start of the linked list of active DNS lookups.
180 */
181static struct ActiveLookup *lookup_head;
182
183/**
184 * Tail of the linked list of active DNS lookups.
185 */
186static struct ActiveLookup *lookup_tail;
187
188/**
189 * context of dnsstub library
190 */
191static struct GNUNET_DNSSTUB_Context *dnsstub_ctx;
192
193/**
194 * My domain, to be appended to the hostname to get a FQDN.
195 */
196static char *my_domain;
197
198/**
199 * How many entries do we have in #cache_head DLL?
200 */
201static unsigned int cache_size;
202
203
204/**
205 * Remove @a entry from cache.
206 *
207 * @param rc entry to free
208 */
209static void
210free_cache_entry (struct ResolveCache *rc)
211{
212 struct RecordListEntry *pos;
213
214 while (NULL != (pos = rc->records_head))
215 {
216 GNUNET_CONTAINER_DLL_remove (rc->records_head, rc->records_tail, pos);
217 GNUNET_DNSPARSER_free_record (pos->record);
218 GNUNET_free (pos->record);
219 GNUNET_free (pos);
220 }
221 GNUNET_free (rc->hostname);
222 GNUNET_CONTAINER_DLL_remove (cache_head, cache_tail, rc);
223 cache_size--;
224 GNUNET_free (rc);
225}
226
227
228/**
229 * Remove @a entry from cache.
230 *
231 * @param rc entry to free
232 */
233static void
234free_hosts_entry (struct ResolveCache *rc)
235{
236 struct RecordListEntry *pos;
237
238 while (NULL != (pos = rc->records_head))
239 {
240 GNUNET_CONTAINER_DLL_remove (rc->records_head, rc->records_tail, pos);
241 GNUNET_DNSPARSER_free_record (pos->record);
242 GNUNET_free (pos->record);
243 GNUNET_free (pos);
244 }
245 GNUNET_free (rc->hostname);
246 GNUNET_CONTAINER_DLL_remove (hosts_head, hosts_tail, rc);
247 cache_size--;
248 GNUNET_free (rc);
249}
250
251
252/**
253 * Release resources associated with @a al
254 *
255 * @param al an active lookup
256 */
257static void
258free_active_lookup (struct ActiveLookup *al)
259{
260 GNUNET_CONTAINER_DLL_remove (lookup_head, lookup_tail, al);
261 if (NULL != al->resolve_handle)
262 {
263 GNUNET_DNSSTUB_resolve_cancel (al->resolve_handle);
264 al->resolve_handle = NULL;
265 }
266 if (NULL != al->timeout_task)
267 {
268 GNUNET_SCHEDULER_cancel (al->timeout_task);
269 al->timeout_task = NULL;
270 }
271 GNUNET_free (al->hostname);
272 GNUNET_free (al);
273}
274
275
276/**
277 * Find out if the configuration file line contains a string
278 * starting with "nameserver ", and if so, return a copy of
279 * the nameserver's IP.
280 *
281 * @param line line to parse
282 * @param line_len number of characters in @a line
283 * @return NULL if no nameserver is configured in this @a line
284 */
285static char *
286extract_dns_server (const char *line, size_t line_len)
287{
288 if (0 == strncmp (line, "nameserver ", strlen ("nameserver ")))
289 return GNUNET_strndup (line + strlen ("nameserver "),
290 line_len - strlen ("nameserver "));
291 return NULL;
292}
293
294
295/**
296 * Find out if the configuration file line contains a string
297 * starting with "search ", and if so, return a copy of
298 * the machine's search domain.
299 *
300 * @param line line to parse
301 * @param line_len number of characters in @a line
302 * @return NULL if no nameserver is configured in this @a line
303 */
304static char *
305extract_search_domain (const char *line, size_t line_len)
306{
307 if (0 == strncmp (line, "search ", strlen ("search ")))
308 return GNUNET_strndup (line + strlen ("search "),
309 line_len - strlen ("search "));
310 return NULL;
311}
312
313
314/**
315 * Reads the list of nameservers from /etc/resolve.conf
316 *
317 * @param[out] server_addrs a list of null-terminated server address strings
318 * @return the number of server addresses in @a server_addrs, -1 on error
319 */
320static int
321lookup_dns_servers (char ***server_addrs)
322{
323 struct GNUNET_DISK_FileHandle *fh;
324 struct GNUNET_DISK_MapHandle *mh;
325 off_t bytes_read;
326 const char *buf;
327 size_t read_offset;
328 unsigned int num_dns_servers;
329
330 fh = GNUNET_DISK_file_open ("/etc/resolv.conf",
331 GNUNET_DISK_OPEN_READ,
332 GNUNET_DISK_PERM_NONE);
333 if (NULL == fh)
334 {
335 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
336 "Could not open /etc/resolv.conf. "
337 "DNS resolution will not be possible.\n");
338 return -1;
339 }
340 if (GNUNET_OK != GNUNET_DISK_file_handle_size (fh, &bytes_read))
341 {
342 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
343 "Could not determine size of /etc/resolv.conf. "
344 "DNS resolution will not be possible.\n");
345 GNUNET_DISK_file_close (fh);
346 return -1;
347 }
348 if (((unsigned long long) bytes_read) > (unsigned long long) SIZE_MAX)
349 {
350 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
351 "/etc/resolv.conf file too large to mmap. "
352 "DNS resolution will not be possible.\n");
353 GNUNET_DISK_file_close (fh);
354 return -1;
355 }
356 buf = GNUNET_DISK_file_map (fh,
357 &mh,
358 GNUNET_DISK_MAP_TYPE_READ,
359 (size_t) bytes_read);
360 *server_addrs = NULL;
361 read_offset = 0;
362 num_dns_servers = 0;
363 while (read_offset < (size_t) bytes_read)
364 {
365 const char *newline;
366 size_t line_len;
367 char *dns_server;
368
369 newline = strchr (buf + read_offset, '\n');
370 if (NULL == newline)
371 break;
372 line_len = newline - buf - read_offset;
373 dns_server = extract_dns_server (buf + read_offset, line_len);
374 if (NULL != dns_server)
375 {
376 GNUNET_array_append (*server_addrs, num_dns_servers, dns_server);
377 }
378 else if (NULL == my_domain)
379 {
380 my_domain = extract_search_domain (buf + read_offset, line_len);
381 }
382 read_offset += line_len + 1;
383 }
384 GNUNET_DISK_file_unmap (mh);
385 GNUNET_DISK_file_close (fh);
386 return (int) num_dns_servers;
387}
388
389
390/**
391 * Compute name to use for DNS reverse lookups from @a ip.
392 *
393 * @param ip IP address to resolve, in binary format, network byte order
394 * @param af address family of @a ip, AF_INET or AF_INET6
395 */
396static char *
397make_reverse_hostname (const void *ip, int af)
398{
399 char *buf = GNUNET_new_array (80, char);
400 int pos = 0;
401
402 if (AF_INET == af)
403 {
404 struct in_addr *addr = (struct in_addr *) ip;
405 uint32_t ip_int = addr->s_addr;
406
407 for (int i = 3; i >= 0; i--)
408 {
409 int n =
410 GNUNET_snprintf (buf + pos, 80 - pos, "%u.", ((uint8_t *) &ip_int)[i]);
411 if (n < 0)
412 {
413 GNUNET_free (buf);
414 return NULL;
415 }
416 pos += n;
417 }
418 pos += GNUNET_snprintf (buf + pos, 80 - pos, "in-addr.arpa");
419 }
420 else if (AF_INET6 == af)
421 {
422 struct in6_addr *addr = (struct in6_addr *) ip;
423 for (int i = 15; i >= 0; i--)
424 {
425 int n =
426 GNUNET_snprintf (buf + pos, 80 - pos, "%x.", addr->s6_addr[i] & 0xf);
427 if (n < 0)
428 {
429 GNUNET_free (buf);
430 return NULL;
431 }
432 pos += n;
433 n = GNUNET_snprintf (buf + pos, 80 - pos, "%x.", addr->s6_addr[i] >> 4);
434 if (n < 0)
435 {
436 GNUNET_free (buf);
437 return NULL;
438 }
439 pos += n;
440 }
441 pos += GNUNET_snprintf (buf + pos, 80 - pos, "ip6.arpa");
442 }
443 buf[pos] = '\0';
444 return buf;
445}
446
447
448/**
449 * Send DNS @a record back to our @a client.
450 *
451 * @param record information to transmit
452 * @param record_type requested record type from client
453 * @param client_request_id to which request are we responding
454 * @param client where to send @a record
455 * @return #GNUNET_YES if we sent a reply,
456 * #GNUNET_NO if the record type is not understood or
457 * does not match @a record_type
458 */
459static int
460send_reply (struct GNUNET_DNSPARSER_Record *record,
461 uint16_t record_type,
462 uint32_t client_request_id,
463 struct GNUNET_SERVICE_Client *client)
464{
465 struct GNUNET_RESOLVER_ResponseMessage *msg;
466 struct GNUNET_MQ_Envelope *env;
467 const void *payload;
468 size_t payload_len;
469
470 switch (record->type)
471 {
472 case GNUNET_DNSPARSER_TYPE_CNAME:
473 if (GNUNET_DNSPARSER_TYPE_CNAME != record_type)
474 return GNUNET_NO;
475 payload = record->data.hostname;
476 payload_len = strlen (record->data.hostname) + 1;
477 break;
478
479 case GNUNET_DNSPARSER_TYPE_PTR:
480 if (GNUNET_DNSPARSER_TYPE_PTR != record_type)
481 return GNUNET_NO;
482 payload = record->data.hostname;
483 payload_len = strlen (record->data.hostname) + 1;
484 break;
485
486 case GNUNET_DNSPARSER_TYPE_A:
487 if ((GNUNET_DNSPARSER_TYPE_A != record_type) &&
488 (GNUNET_DNSPARSER_TYPE_ALL != record_type))
489 return GNUNET_NO;
490 payload = record->data.raw.data;
491 payload_len = record->data.raw.data_len;
492 break;
493
494 case GNUNET_DNSPARSER_TYPE_AAAA:
495 if ((GNUNET_DNSPARSER_TYPE_AAAA != record_type) &&
496 (GNUNET_DNSPARSER_TYPE_ALL != record_type))
497 return GNUNET_NO;
498 payload = record->data.raw.data;
499 payload_len = record->data.raw.data_len;
500 break;
501
502 default:
503 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
504 "Cannot handle DNS response type %u: not supported here\n",
505 record->type);
506 return GNUNET_NO;
507 }
508 env = GNUNET_MQ_msg_extra (msg,
509 payload_len,
510 GNUNET_MESSAGE_TYPE_RESOLVER_RESPONSE);
511 msg->client_id = client_request_id;
512 GNUNET_memcpy (&msg[1], payload, payload_len);
513 GNUNET_MQ_send (GNUNET_SERVICE_client_get_mq (client), env);
514 return GNUNET_YES;
515}
516
517
518/**
519 * Send message to @a client that we transmitted all
520 * responses for @a client_request_id
521 *
522 * @param client_request_id to which request are we responding
523 * @param client where to send @a record
524 */
525static void
526send_end_msg (uint32_t client_request_id, struct GNUNET_SERVICE_Client *client)
527{
528 struct GNUNET_RESOLVER_ResponseMessage *msg;
529 struct GNUNET_MQ_Envelope *env;
530
531 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Sending END message\n");
532 env = GNUNET_MQ_msg (msg, GNUNET_MESSAGE_TYPE_RESOLVER_RESPONSE);
533 msg->client_id = client_request_id;
534 GNUNET_MQ_send (GNUNET_SERVICE_client_get_mq (client), env);
535}
536
537
538/**
539 * Remove expired entries from @a rc
540 *
541 * @param rc entry in resolver cache
542 * @return #GNUNET_YES if @a rc was completely expired
543 * #GNUNET_NO if some entries are left
544 */
545static int
546remove_expired (struct ResolveCache *rc)
547{
548 struct GNUNET_TIME_Absolute now = GNUNET_TIME_absolute_get ();
549 struct RecordListEntry *n;
550
551 for (struct RecordListEntry *pos = rc->records_head; NULL != pos; pos = n)
552 {
553 n = pos->next;
554 if (now.abs_value_us > pos->record->expiration_time.abs_value_us)
555 {
556 GNUNET_CONTAINER_DLL_remove (rc->records_head, rc->records_tail, pos);
557 GNUNET_DNSPARSER_free_record (pos->record);
558 GNUNET_free (pos->record);
559 GNUNET_free (pos);
560 }
561 }
562 if (NULL == rc->records_head)
563 {
564 free_cache_entry (rc);
565 return GNUNET_YES;
566 }
567 return GNUNET_NO;
568}
569
570
571/**
572 * Process DNS request for @a hostname with request ID @a request_id
573 * from @a client demanding records of type @a record_type.
574 *
575 * @param hostname DNS name to resolve
576 * @param record_type desired record type
577 * @param client_request_id client's request ID
578 * @param client who should get the result?
579 */
580static void
581process_get (const char *hostname,
582 uint16_t record_type,
583 uint32_t client_request_id,
584 struct GNUNET_SERVICE_Client *client);
585
586
587/**
588 * Get an IP address as a string (works for both IPv4 and IPv6). Note
589 * that the resolution happens asynchronously and that the first call
590 * may not immediately result in the FQN (but instead in a
591 * human-readable IP address).
592 *
593 * @param hostname what hostname was to be resolved
594 * @param record_type what type of record was requested
595 * @param client_request_id unique identification of the client's request
596 * @param client handle to the client making the request (for sending the reply)
597 */
598static int
599try_cache (const char *hostname,
600 uint16_t record_type,
601 uint32_t client_request_id,
602 struct GNUNET_SERVICE_Client *client)
603{
604 struct ResolveCache *pos;
605 struct ResolveCache *next;
606 int found;
607 int in_hosts;
608
609 in_hosts = GNUNET_NO;
610 for (pos = hosts_head; NULL != pos; pos = pos->next)
611 if (0 == strcmp (pos->hostname, hostname))
612 {
613 in_hosts = GNUNET_YES;
614 break;
615 }
616 if (NULL == pos)
617 {
618 next = cache_head;
619 for (pos = next; NULL != pos; pos = next)
620 {
621 next = pos->next;
622 if (GNUNET_YES == remove_expired (pos))
623 continue;
624 if (0 == strcmp (pos->hostname, hostname))
625 break;
626 }
627 }
628 if (NULL == pos)
629 {
630 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "No cache entry for '%s'\n", hostname);
631 return GNUNET_NO;
632 }
633 if ((GNUNET_NO == in_hosts) && (cache_head != pos))
634 {
635 /* move result to head to achieve LRU for cache eviction */
636 GNUNET_CONTAINER_DLL_remove (cache_head, cache_tail, pos);
637 GNUNET_CONTAINER_DLL_insert (cache_head, cache_tail, pos);
638 }
639 found = GNUNET_NO;
640 for (struct RecordListEntry *rle = pos->records_head; NULL != rle;
641 rle = rle->next)
642 {
643 const struct GNUNET_DNSPARSER_Record *record = rle->record;
644
645 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
646 "Checking cache entry for '%s', record is for '%s'\n",
647 hostname,
648 record->name);
649 if ((GNUNET_DNSPARSER_TYPE_CNAME == record->type) &&
650 (GNUNET_DNSPARSER_TYPE_CNAME != record_type) && (GNUNET_NO == found))
651 {
652 const char *hostname = record->data.hostname;
653
654 process_get (hostname, record_type, client_request_id, client);
655 return GNUNET_YES; /* counts as a cache "hit" */
656 }
657 if (0 == strcmp (record->name, hostname))
658 found |= send_reply (rle->record, record_type, client_request_id, client);
659 }
660 if (GNUNET_NO == found)
661 return GNUNET_NO; /* had records, but none matched! */
662 send_end_msg (client_request_id, client);
663 return GNUNET_YES;
664}
665
666
667/**
668 * Create DNS query for @a hostname of type @a type
669 * with DNS request ID @a dns_id.
670 *
671 * @param hostname DNS name to query
672 * @param type requested DNS record type
673 * @param dns_id what should be the DNS request ID
674 * @param[out] packet_buf where to write the request packet
675 * @param[out] packet_size set to size of @a packet_buf on success
676 * @return #GNUNET_OK on success
677 */
678static int
679pack (const char *hostname,
680 uint16_t type,
681 uint16_t dns_id,
682 char **packet_buf,
683 size_t *packet_size)
684{
685 struct GNUNET_DNSPARSER_Query query;
686 struct GNUNET_DNSPARSER_Packet packet;
687
688 query.name = (char *) hostname;
689 query.type = type;
690 query.dns_traffic_class = GNUNET_TUN_DNS_CLASS_INTERNET;
691 memset (&packet, 0, sizeof(packet));
692 packet.num_queries = 1;
693 packet.queries = &query;
694 packet.id = htons (dns_id);
695 packet.flags.recursion_desired = 1;
696 if (GNUNET_OK !=
697 GNUNET_DNSPARSER_pack (&packet, UINT16_MAX, packet_buf, packet_size))
698 {
699 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
700 "Failed to pack query for hostname `%s'\n",
701 hostname);
702 packet_buf = NULL;
703 return GNUNET_SYSERR;
704 }
705 return GNUNET_OK;
706}
707
708
709static void
710cache_answers (const char *name,
711 struct GNUNET_DNSPARSER_Record *records,
712 unsigned int num_records)
713{
714 struct ResolveCache *rc;
715 struct GNUNET_DNSPARSER_Record *record;
716 struct RecordListEntry *rle;
717
718 for (unsigned int i = 0; i != num_records; i++)
719 {
720 record = &records[i];
721
722 for (rc = cache_head; NULL != rc; rc = rc->next)
723 if (0 == strcasecmp (rc->hostname, name))
724 break;
725 if (NULL == rc)
726 {
727 rc = GNUNET_new (struct ResolveCache);
728 rc->hostname = GNUNET_strdup (name);
729 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
730 "Caching record for name %s under %s\n",
731 record->name, name);
732 GNUNET_CONTAINER_DLL_insert (cache_head, cache_tail, rc);
733 cache_size++;
734 }
735 /* TODO: ought to check first if we have this exact record
736 already in the cache! */
737 rle = GNUNET_new (struct RecordListEntry);
738 rle->record = GNUNET_DNSPARSER_duplicate_record (record);
739 GNUNET_CONTAINER_DLL_insert (rc->records_head, rc->records_tail, rle);
740 }
741}
742
743
744/**
745 * We got a result from DNS. Add it to the cache and
746 * see if we can make our client happy...
747 *
748 * @param cls the `struct ActiveLookup`
749 * @param dns the DNS response
750 * @param dns_len number of bytes in @a dns
751 */
752static void
753handle_resolve_result (void *cls,
754 const struct GNUNET_TUN_DnsHeader *dns,
755 size_t dns_len)
756{
757 struct ActiveLookup *al = cls;
758 struct GNUNET_DNSPARSER_Packet *parsed;
759
760 parsed = GNUNET_DNSPARSER_parse ((const char *) dns, dns_len);
761 if (NULL == parsed)
762 {
763 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
764 "Failed to parse DNS reply (hostname %s, request ID %u)\n",
765 al->hostname,
766 al->dns_id);
767 return;
768 }
769 if (al->dns_id != ntohs (parsed->id))
770 {
771 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
772 "Request ID in DNS reply does not match\n");
773 GNUNET_DNSPARSER_free_packet (parsed);
774 return;
775 }
776 if (0 == parsed->num_answers + parsed->num_authority_records
777 + parsed->num_additional_records)
778 {
779 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
780 "DNS reply (hostname %s, request ID %u) contains no answers\n",
781 al->hostname,
782 (unsigned int) al->client_request_id);
783 /* resume by trying again from cache */
784 if (GNUNET_NO == try_cache (al->hostname,
785 al->record_type,
786 al->client_request_id,
787 al->client))
788 /* cache failed, tell client we could not get an answer */
789 {
790 send_end_msg (al->client_request_id, al->client);
791 }
792 GNUNET_DNSPARSER_free_packet (parsed);
793 free_active_lookup (al);
794 return;
795 }
796 /* LRU-based cache eviction: we remove from tail */
797 while (cache_size > MAX_CACHE)
798 free_cache_entry (cache_tail);
799
800 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
801 "Got reply for hostname %s and request ID %u\n",
802 al->hostname,
803 (unsigned int) al->client_request_id);
804 /* add to cache */
805 cache_answers (al->hostname, parsed->answers, parsed->num_answers);
806 cache_answers (al->hostname,
807 parsed->authority_records,
808 parsed->num_authority_records);
809 cache_answers (al->hostname,
810 parsed->additional_records,
811 parsed->num_additional_records);
812
813 /* see if we need to do the 2nd request for AAAA records */
814 if ((GNUNET_DNSPARSER_TYPE_ALL == al->record_type) &&
815 (GNUNET_NO == al->did_aaaa))
816 {
817 char *packet_buf;
818 size_t packet_size;
819 uint16_t dns_id;
820
821 dns_id = (uint16_t) GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_NONCE,
822 UINT16_MAX);
823 if (GNUNET_OK == pack (al->hostname,
824 GNUNET_DNSPARSER_TYPE_AAAA,
825 dns_id,
826 &packet_buf,
827 &packet_size))
828 {
829 al->did_aaaa = GNUNET_YES;
830 al->dns_id = dns_id;
831 GNUNET_DNSSTUB_resolve_cancel (al->resolve_handle);
832 al->resolve_handle = GNUNET_DNSSTUB_resolve (dnsstub_ctx,
833 packet_buf,
834 packet_size,
835 &handle_resolve_result,
836 al);
837 GNUNET_free (packet_buf);
838 GNUNET_DNSPARSER_free_packet (parsed);
839 return;
840 }
841 }
842
843 /* resume by trying again from cache */
844 if (GNUNET_NO == try_cache (al->hostname,
845 al->record_type,
846 al->client_request_id,
847 al->client))
848 /* cache failed, tell client we could not get an answer */
849 {
850 send_end_msg (al->client_request_id, al->client);
851 }
852 free_active_lookup (al);
853 GNUNET_DNSPARSER_free_packet (parsed);
854}
855
856
857/**
858 * We encountered a timeout trying to perform a
859 * DNS lookup.
860 *
861 * @param cls a `struct ActiveLookup`
862 */
863static void
864handle_resolve_timeout (void *cls)
865{
866 struct ActiveLookup *al = cls;
867
868 al->timeout_task = NULL;
869 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "DNS lookup timeout!\n");
870 send_end_msg (al->client_request_id, al->client);
871 free_active_lookup (al);
872}
873
874
875/**
876 * Initiate an active lookup, then cache the result and
877 * try to then complete the resolution.
878 *
879 * @param hostname DNS name to resolve
880 * @param record_type record type to locate
881 * @param client_request_id client request ID
882 * @param client handle to the client
883 * @return #GNUNET_OK if the DNS query is now pending
884 */
885static int
886resolve_and_cache (const char *hostname,
887 uint16_t record_type,
888 uint32_t client_request_id,
889 struct GNUNET_SERVICE_Client *client)
890{
891 char *packet_buf;
892 size_t packet_size;
893 struct ActiveLookup *al;
894 uint16_t dns_id;
895 uint16_t type;
896
897 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "resolve_and_cache `%s'\n", hostname);
898 dns_id = (uint16_t) GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_NONCE,
899 UINT16_MAX);
900
901 if (GNUNET_DNSPARSER_TYPE_ALL == record_type)
902 type = GNUNET_DNSPARSER_TYPE_A;
903 else
904 type = record_type;
905 if (GNUNET_OK != pack (hostname, type, dns_id, &packet_buf, &packet_size))
906 {
907 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
908 "Failed to pack query for hostname `%s'\n",
909 hostname);
910 return GNUNET_SYSERR;
911 }
912
913 al = GNUNET_new (struct ActiveLookup);
914 al->hostname = GNUNET_strdup (hostname);
915 al->record_type = record_type;
916 al->client_request_id = client_request_id;
917 al->dns_id = dns_id;
918 al->client = client;
919 al->timeout_task =
920 GNUNET_SCHEDULER_add_delayed (DNS_TIMEOUT, &handle_resolve_timeout, al);
921 al->resolve_handle = GNUNET_DNSSTUB_resolve (dnsstub_ctx,
922 packet_buf,
923 packet_size,
924 &handle_resolve_result,
925 al);
926 GNUNET_free (packet_buf);
927 GNUNET_CONTAINER_DLL_insert (lookup_head, lookup_tail, al);
928 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
929 "Resolving %s, client_request_id = %u, dns_id = %u\n",
930 hostname,
931 (unsigned int) client_request_id,
932 (unsigned int) dns_id);
933 return GNUNET_OK;
934}
935
936
937/**
938 * Process DNS request for @a hostname with request ID @a client_request_id
939 * from @a client demanding records of type @a record_type.
940 *
941 * @param hostname DNS name to resolve
942 * @param record_type desired record type
943 * @param client_request_id client's request ID
944 * @param client who should get the result?
945 */
946static void
947process_get (const char *hostname,
948 uint16_t record_type,
949 uint32_t client_request_id,
950 struct GNUNET_SERVICE_Client *client)
951{
952 char fqdn[255];
953
954 if (GNUNET_NO != try_cache (hostname, record_type, client_request_id, client))
955 return;
956 if ((NULL != my_domain) && (NULL == strchr (hostname, (unsigned char) '.')) &&
957 (strlen (hostname) + strlen (my_domain) <= 253))
958 {
959 GNUNET_snprintf (fqdn, sizeof(fqdn), "%s.%s", hostname, my_domain);
960 }
961 else if (strlen (hostname) < 255)
962 {
963 GNUNET_snprintf (fqdn, sizeof(fqdn), "%s", hostname);
964 }
965 else
966 {
967 GNUNET_break (0);
968 GNUNET_SERVICE_client_drop (client);
969 return;
970 }
971 if (GNUNET_NO == try_cache (fqdn, record_type, client_request_id, client))
972 {
973 if (GNUNET_OK !=
974 resolve_and_cache (fqdn, record_type, client_request_id, client))
975 {
976 send_end_msg (client_request_id, client);
977 }
978 }
979}
980
981
982/**
983 * Verify well-formedness of GET-message.
984 *
985 * @param cls closure, unused
986 * @param get the actual message
987 * @return #GNUNET_OK if @a get is well-formed
988 */
989static int
990check_get (void *cls, const struct GNUNET_RESOLVER_GetMessage *get)
991{
992 uint16_t size;
993 int direction;
994 int af;
995
996 (void) cls;
997 size = ntohs (get->header.size) - sizeof(*get);
998 direction = ntohl (get->direction);
999 if (GNUNET_NO == direction)
1000 {
1001 GNUNET_MQ_check_zero_termination (get);
1002 return GNUNET_OK;
1003 }
1004 af = ntohl (get->af);
1005 switch (af)
1006 {
1007 case AF_INET:
1008 if (size != sizeof(struct in_addr))
1009 {
1010 GNUNET_break (0);
1011 return GNUNET_SYSERR;
1012 }
1013 break;
1014
1015 case AF_INET6:
1016 if (size != sizeof(struct in6_addr))
1017 {
1018 GNUNET_break (0);
1019 return GNUNET_SYSERR;
1020 }
1021 break;
1022
1023 default:
1024 GNUNET_break (0);
1025 return GNUNET_SYSERR;
1026 }
1027 return GNUNET_OK;
1028}
1029
1030
1031/**
1032 * Handle GET-message.
1033 *
1034 * @param cls identification of the client
1035 * @param msg the actual message
1036 */
1037static void
1038handle_get (void *cls, const struct GNUNET_RESOLVER_GetMessage *msg)
1039{
1040 struct GNUNET_SERVICE_Client *client = cls;
1041 int direction;
1042 int af;
1043 uint32_t client_request_id;
1044 char *hostname;
1045
1046 direction = ntohl (msg->direction);
1047 af = ntohl (msg->af);
1048 client_request_id = msg->client_id;
1049 GNUNET_SERVICE_client_continue (client);
1050 if (GNUNET_NO == direction)
1051 {
1052 /* IP from hostname */
1053 hostname = GNUNET_strdup ((const char *) &msg[1]);
1054 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
1055 "Client asks to resolve `%s'\n",
1056 hostname);
1057 switch (af)
1058 {
1059 case AF_UNSPEC: {
1060 process_get (hostname,
1061 GNUNET_DNSPARSER_TYPE_ALL,
1062 client_request_id,
1063 client);
1064 break;
1065 }
1066
1067 case AF_INET: {
1068 process_get (hostname,
1069 GNUNET_DNSPARSER_TYPE_A,
1070 client_request_id,
1071 client);
1072 break;
1073 }
1074
1075 case AF_INET6: {
1076 process_get (hostname,
1077 GNUNET_DNSPARSER_TYPE_AAAA,
1078 client_request_id,
1079 client);
1080 break;
1081 }
1082
1083 default: {
1084 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "got invalid af: %d\n", af);
1085 GNUNET_assert (0);
1086 }
1087 }
1088 }
1089 else
1090 {
1091 /* hostname from IP */
1092 hostname = make_reverse_hostname (&msg[1], af);
1093 process_get (hostname,
1094 GNUNET_DNSPARSER_TYPE_PTR,
1095 client_request_id,
1096 client);
1097 }
1098 GNUNET_free (hostname);
1099}
1100
1101
1102/**
1103 * Service is shutting down, clean up.
1104 *
1105 * @param cls NULL, unused
1106 */
1107static void
1108shutdown_task (void *cls)
1109{
1110 (void) cls;
1111
1112 while (NULL != lookup_head)
1113 free_active_lookup (lookup_head);
1114 while (NULL != cache_head)
1115 free_cache_entry (cache_head);
1116 while (NULL != hosts_head)
1117 free_hosts_entry (hosts_head);
1118 GNUNET_DNSSTUB_stop (dnsstub_ctx);
1119 GNUNET_free (my_domain);
1120}
1121
1122
1123/**
1124 * Add information about a host from /etc/hosts
1125 * to our cache.
1126 *
1127 * @param hostname the name of the host
1128 * @param rec_type DNS record type to use
1129 * @param data payload
1130 * @param data_size number of bytes in @a data
1131 */
1132static void
1133add_host (const char *hostname,
1134 uint16_t rec_type,
1135 const void *data,
1136 size_t data_size)
1137{
1138 struct ResolveCache *rc;
1139 struct RecordListEntry *rle;
1140 struct GNUNET_DNSPARSER_Record *rec;
1141
1142 rec = GNUNET_malloc (sizeof(struct GNUNET_DNSPARSER_Record));
1143 rec->expiration_time = GNUNET_TIME_UNIT_FOREVER_ABS;
1144 rec->type = rec_type;
1145 rec->dns_traffic_class = GNUNET_TUN_DNS_CLASS_INTERNET;
1146 rec->name = GNUNET_strdup (hostname);
1147 rec->data.raw.data = GNUNET_memdup (data, data_size);
1148 rec->data.raw.data_len = data_size;
1149 rle = GNUNET_new (struct RecordListEntry);
1150 rle->record = rec;
1151 rc = GNUNET_new (struct ResolveCache);
1152 rc->hostname = GNUNET_strdup (hostname);
1153 GNUNET_CONTAINER_DLL_insert (rc->records_head, rc->records_tail, rle);
1154 GNUNET_CONTAINER_DLL_insert (hosts_head, hosts_tail, rc);
1155}
1156
1157
1158/**
1159 * Extract host information from a line in /etc/hosts
1160 *
1161 * @param line the line to parse
1162 * @param line_len number of bytes in @a line
1163 */
1164static void
1165extract_hosts (const char *line, size_t line_len)
1166{
1167 const char *c;
1168 struct in_addr v4;
1169 struct in6_addr v6;
1170 char *tbuf;
1171 char *tok;
1172
1173 /* ignore everything after '#' */
1174 c = memrchr (line, (unsigned char) '#', line_len);
1175 if (NULL != c)
1176 line_len = c - line;
1177 /* ignore leading whitespace */
1178 while ((0 < line_len) && isspace ((unsigned char) *line))
1179 {
1180 line++;
1181 line_len--;
1182 }
1183 tbuf = GNUNET_strndup (line, line_len);
1184 tok = strtok (tbuf, " \t");
1185 if (NULL == tok)
1186 {
1187 GNUNET_free (tbuf);
1188 return;
1189 }
1190 if (1 == inet_pton (AF_INET, tok, &v4))
1191 {
1192 while (NULL != (tok = strtok (NULL, " \t")))
1193 add_host (tok, GNUNET_DNSPARSER_TYPE_A, &v4, sizeof(struct in_addr));
1194 }
1195 else if (1 == inet_pton (AF_INET6, tok, &v6))
1196 {
1197 while (NULL != (tok = strtok (NULL, " \t")))
1198 add_host (tok, GNUNET_DNSPARSER_TYPE_AAAA, &v6, sizeof(struct in6_addr));
1199 }
1200 GNUNET_free (tbuf);
1201}
1202
1203
1204/**
1205 * Reads the list of hosts from /etc/hosts.
1206 */
1207static void
1208load_etc_hosts (void)
1209{
1210 struct GNUNET_DISK_FileHandle *fh;
1211 struct GNUNET_DISK_MapHandle *mh;
1212 off_t bytes_read;
1213 const char *buf;
1214 size_t read_offset;
1215
1216 fh = GNUNET_DISK_file_open ("/etc/hosts",
1217 GNUNET_DISK_OPEN_READ,
1218 GNUNET_DISK_PERM_NONE);
1219 if (NULL == fh)
1220 {
1221 GNUNET_log (GNUNET_ERROR_TYPE_INFO, "Failed to open /etc/hosts");
1222 return;
1223 }
1224 if (GNUNET_OK != GNUNET_DISK_file_handle_size (fh, &bytes_read))
1225 {
1226 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
1227 "Could not determine size of /etc/hosts. "
1228 "DNS resolution will not be possible.\n");
1229 GNUNET_DISK_file_close (fh);
1230 return;
1231 }
1232 if (((unsigned long long) bytes_read) > (unsigned long long) SIZE_MAX)
1233 {
1234 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
1235 "/etc/hosts file too large to mmap. "
1236 "DNS resolution will not be possible.\n");
1237 GNUNET_DISK_file_close (fh);
1238 return;
1239 }
1240 buf = GNUNET_DISK_file_map (fh,
1241 &mh,
1242 GNUNET_DISK_MAP_TYPE_READ,
1243 (size_t) bytes_read);
1244 read_offset = 0;
1245 while (read_offset < (size_t) bytes_read)
1246 {
1247 const char *newline;
1248 size_t line_len;
1249
1250 newline = strchr (buf + read_offset, '\n');
1251 if (NULL == newline)
1252 break;
1253 line_len = newline - buf - read_offset;
1254 extract_hosts (buf + read_offset, line_len);
1255 read_offset += line_len + 1;
1256 }
1257 GNUNET_DISK_file_unmap (mh);
1258 GNUNET_DISK_file_close (fh);
1259}
1260
1261
1262/**
1263 * Service is starting, initialize everything.
1264 *
1265 * @param cls NULL, unused
1266 * @param cfg our configuration
1267 * @param sh service handle
1268 */
1269static void
1270init_cb (void *cls,
1271 const struct GNUNET_CONFIGURATION_Handle *cfg,
1272 struct GNUNET_SERVICE_Handle *sh)
1273{
1274 char **dns_servers;
1275 int num_dns_servers;
1276
1277 (void) cfg;
1278 (void) sh;
1279 load_etc_hosts ();
1280 GNUNET_SCHEDULER_add_shutdown (&shutdown_task, cls);
1281 dnsstub_ctx = GNUNET_DNSSTUB_start (128);
1282 dns_servers = NULL;
1283 num_dns_servers = lookup_dns_servers (&dns_servers);
1284 if (0 >= num_dns_servers)
1285 {
1286 GNUNET_log (
1287 GNUNET_ERROR_TYPE_ERROR,
1288 _ ("No DNS server available. DNS resolution will not be possible.\n"));
1289 return;
1290 }
1291 for (int i = 0; i < num_dns_servers; i++)
1292 {
1293 int result = GNUNET_DNSSTUB_add_dns_ip (dnsstub_ctx, dns_servers[i]);
1294 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
1295 "Adding DNS server '%s': %s\n",
1296 dns_servers[i],
1297 GNUNET_OK == result ? "success" : "failure");
1298 GNUNET_free (dns_servers[i]);
1299 }
1300 GNUNET_free (dns_servers);
1301}
1302
1303
1304/**
1305 * Callback called when a client connects to the service.
1306 *
1307 * @param cls closure for the service, unused
1308 * @param c the new client that connected to the service
1309 * @param mq the message queue used to send messages to the client
1310 * @return @a c
1311 */
1312static void *
1313connect_cb (void *cls,
1314 struct GNUNET_SERVICE_Client *c,
1315 struct GNUNET_MQ_Handle *mq)
1316{
1317 (void) cls;
1318 (void) mq;
1319
1320 return c;
1321}
1322
1323
1324/**
1325 * Callback called when a client disconnected from the service
1326 *
1327 * @param cls closure for the service
1328 * @param c the client that disconnected
1329 * @param internal_cls should be equal to @a c
1330 */
1331static void
1332disconnect_cb (void *cls, struct GNUNET_SERVICE_Client *c, void *internal_cls)
1333{
1334 struct ActiveLookup *n;
1335
1336 (void) cls;
1337
1338 GNUNET_assert (c == internal_cls);
1339 n = lookup_head;
1340 for (struct ActiveLookup *al = n; NULL != al; al = n)
1341 {
1342 n = al->next;
1343 if (al->client == c)
1344 free_active_lookup (al);
1345 }
1346}
1347
1348
1349/**
1350 * Define "main" method using service macro.
1351 */
1352GNUNET_SERVICE_MAIN (
1353 "resolver",
1354 GNUNET_SERVICE_OPTION_NONE,
1355 &init_cb,
1356 &connect_cb,
1357 &disconnect_cb,
1358 NULL,
1359 GNUNET_MQ_hd_var_size (get,
1360 GNUNET_MESSAGE_TYPE_RESOLVER_REQUEST,
1361 struct GNUNET_RESOLVER_GetMessage,
1362 NULL),
1363 GNUNET_MQ_handler_end ());
1364
1365
1366#if defined(__linux__) && defined(__GLIBC__)
1367#include <malloc.h>
1368
1369/**
1370 * MINIMIZE heap size (way below 128k) since this process doesn't need much.
1371 */
1372void __attribute__ ((constructor))
1373GNUNET_RESOLVER_memory_init ()
1374{
1375 mallopt (M_TRIM_THRESHOLD, 4 * 1024);
1376 mallopt (M_TOP_PAD, 1 * 1024);
1377 malloc_trim (0);
1378}
1379
1380
1381#endif
1382
1383
1384/* end of gnunet-service-resolver.c */
generated by cgit v1.2.3 (git 2.39.1) at 2024-05-07 04:11:55 +0000