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13 General Public License for more details.
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22 * @brief DNS stub resolver which sends DNS requests to an actual resolver
23 * @author Christian Grothoff
26 #include "gnunet_util_lib.h"
27 #include "gnunet_tun_lib.h"
28 #include "gnunet_dnsstub_lib.h"
31 * Timeout for an external (Internet-DNS) DNS resolution
33 #define REQUEST_TIMEOUT GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS, 5)
36 * Timeout for retrying DNS queries.
38 #define DNS_RETRANSMIT_DELAY GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_MILLISECONDS, 250)
41 * How many DNS sockets do we open at most at the same time?
42 * (technical socket maximum is this number x2 for IPv4+IPv6)
44 #define DNS_SOCKET_MAX 128
48 * UDP socket we are using for sending DNS requests to the Internet.
50 struct GNUNET_DNSSTUB_RequestSocket
54 * UDP socket we use for this request for IPv4
56 struct GNUNET_NETWORK_Handle *dnsout4;
59 * UDP socket we use for this request for IPv6
61 struct GNUNET_NETWORK_Handle *dnsout6;
64 * Function to call with result.
66 GNUNET_DNSSTUB_ResultCallback rc;
74 * Task for reading from dnsout4 and dnsout6.
76 struct GNUNET_SCHEDULER_Task *read_task;
79 * Task for retrying transmission of the query.
81 struct GNUNET_SCHEDULER_Task *retry_task;
84 * When should this request time out?
86 struct GNUNET_TIME_Absolute timeout;
89 * Address we sent the DNS request to.
91 struct sockaddr_storage addr;
94 * Number of bytes in @e addr.
99 * Query we sent to @e addr.
104 * Number of bytes in @a request.
112 * Handle to the stub resolver.
114 struct GNUNET_DNSSTUB_Context
118 * Array of all open sockets for DNS requests.
120 struct GNUNET_DNSSTUB_RequestSocket sockets[DNS_SOCKET_MAX];
123 * IP address to use for the DNS server if we are a DNS exit service
124 * (for VPN via cadet); otherwise NULL.
131 * We're done with a `struct GNUNET_DNSSTUB_RequestSocket`, close it for now.
133 * @param rs request socket to clean up
136 cleanup_rs (struct GNUNET_DNSSTUB_RequestSocket *rs)
138 if (NULL != rs->dnsout4)
140 GNUNET_NETWORK_socket_close (rs->dnsout4);
143 if (NULL != rs->dnsout6)
145 GNUNET_NETWORK_socket_close (rs->dnsout6);
148 if (NULL != rs->read_task)
150 GNUNET_SCHEDULER_cancel (rs->read_task);
151 rs->read_task = NULL;
153 if (NULL != rs->retry_task)
155 GNUNET_SCHEDULER_cancel (rs->retry_task);
156 rs->retry_task = NULL;
158 if (NULL != rs->request)
160 GNUNET_free (rs->request);
167 * Open source port for sending DNS requests
169 * @param af AF_INET or AF_INET6
170 * @return #GNUNET_OK on success
172 static struct GNUNET_NETWORK_Handle *
175 struct sockaddr_in a4;
176 struct sockaddr_in6 a6;
179 struct GNUNET_NETWORK_Handle *ret;
181 ret = GNUNET_NETWORK_socket_create (af, SOCK_DGRAM, 0);
187 memset (&a4, 0, alen = sizeof (struct sockaddr_in));
188 sa = (struct sockaddr *) &a4;
191 memset (&a6, 0, alen = sizeof (struct sockaddr_in6));
192 sa = (struct sockaddr *) &a6;
196 GNUNET_NETWORK_socket_close (ret);
200 if (GNUNET_OK != GNUNET_NETWORK_socket_bind (ret,
204 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
205 _("Could not bind to any port: %s\n"),
207 GNUNET_NETWORK_socket_close (ret);
215 * Read a DNS response from the (unhindered) UDP-Socket
217 * @param cls socket to read from
220 read_response (void *cls);
224 * Get a socket of the specified address family to send out a
225 * UDP DNS request to the Internet.
227 * @param ctx the DNSSTUB context
228 * @param af desired address family
229 * @return NULL on error (given AF not "supported")
231 static struct GNUNET_DNSSTUB_RequestSocket *
232 get_request_socket (struct GNUNET_DNSSTUB_Context *ctx,
235 struct GNUNET_DNSSTUB_RequestSocket *rs;
236 struct GNUNET_NETWORK_FDSet *rset;
238 for (unsigned int i=0;i<256;i++)
240 rs = &ctx->sockets[GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_NONCE,
247 /* signal "failure" */
254 rs->timeout = GNUNET_TIME_relative_to_absolute (REQUEST_TIMEOUT);
258 if (NULL == rs->dnsout4)
259 rs->dnsout4 = open_socket (AF_INET);
262 if (NULL == rs->dnsout6)
263 rs->dnsout6 = open_socket (AF_INET6);
268 if (NULL != rs->read_task)
270 GNUNET_SCHEDULER_cancel (rs->read_task);
271 rs->read_task = NULL;
273 if (NULL != rs->retry_task)
275 GNUNET_SCHEDULER_cancel (rs->retry_task);
276 rs->retry_task = NULL;
278 if (NULL != rs->request)
280 GNUNET_free (rs->request);
283 if ( (NULL == rs->dnsout4) &&
284 (NULL == rs->dnsout6) )
286 rset = GNUNET_NETWORK_fdset_create ();
287 if (NULL != rs->dnsout4)
288 GNUNET_NETWORK_fdset_set (rset,
290 if (NULL != rs->dnsout6)
291 GNUNET_NETWORK_fdset_set (rset,
293 rs->read_task = GNUNET_SCHEDULER_add_select (GNUNET_SCHEDULER_PRIORITY_DEFAULT,
299 GNUNET_NETWORK_fdset_destroy (rset);
305 * Task to (re)transmit the DNS query, possibly repeatedly until
308 * @param cls our `struct GNUNET_DNSSTUB_RequestSocket *`
311 transmit_query (void *cls)
313 struct GNUNET_DNSSTUB_RequestSocket *rs = cls;
314 struct GNUNET_NETWORK_Handle *ret;
316 rs->retry_task = NULL;
317 ret = (NULL != rs->dnsout4) ? rs->dnsout4 : rs->dnsout6;
318 GNUNET_assert (NULL != ret);
320 GNUNET_NETWORK_socket_sendto (ret,
323 (struct sockaddr *) &rs->addr,
325 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
326 _("Failed to send DNS request to %s\n"),
327 GNUNET_a2s ((struct sockaddr *) &rs->addr,
330 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
331 _("Sent DNS request to %s\n"),
332 GNUNET_a2s ((struct sockaddr *) &rs->addr,
334 rs->retry_task = GNUNET_SCHEDULER_add_delayed (DNS_RETRANSMIT_DELAY,
341 * Perform DNS resolution.
343 * @param ctx stub resolver to use
344 * @param sa the socket address
345 * @param sa_len the length of @a sa
346 * @param request DNS request to transmit
347 * @param request_len number of bytes in @a request
348 * @param rc function to call with result
349 * @param rc_cls closure for @a rc
350 * @return socket used for the request, NULL on error
352 struct GNUNET_DNSSTUB_RequestSocket *
353 GNUNET_DNSSTUB_resolve (struct GNUNET_DNSSTUB_Context *ctx,
354 const struct sockaddr *sa,
358 GNUNET_DNSSTUB_ResultCallback rc,
361 struct GNUNET_DNSSTUB_RequestSocket *rs;
363 if (NULL == (rs = get_request_socket (ctx,
366 GNUNET_assert (NULL == rs->rc);
367 GNUNET_memcpy (&rs->addr,
370 rs->addrlen = sa_len;
373 rs->request = GNUNET_memdup (request,
375 rs->request_len = request_len;
376 rs->retry_task = GNUNET_SCHEDULER_add_now (&transmit_query,
383 * Perform DNS resolution using our default IP from init.
385 * @param ctx stub resolver to use
386 * @param request DNS request to transmit
387 * @param request_len number of bytes in msg
388 * @param rc function to call with result
389 * @param rc_cls closure for 'rc'
390 * @return socket used for the request, NULL on error
392 struct GNUNET_DNSSTUB_RequestSocket *
393 GNUNET_DNSSTUB_resolve2 (struct GNUNET_DNSSTUB_Context *ctx,
396 GNUNET_DNSSTUB_ResultCallback rc,
400 struct sockaddr_in v4;
401 struct sockaddr_in6 v6;
404 struct GNUNET_NETWORK_Handle *dnsout;
405 struct GNUNET_DNSSTUB_RequestSocket *rs;
407 memset (&v4, 0, sizeof (v4));
408 memset (&v6, 0, sizeof (v6));
409 if (1 == inet_pton (AF_INET,
414 v4.sin_family = AF_INET;
415 v4.sin_port = htons (53);
416 #if HAVE_SOCKADDR_IN_SIN_LEN
417 v4.sin_len = (u_char) salen;
419 sa = (struct sockaddr *) &v4;
422 else if (1 == inet_pton (AF_INET6,
427 v6.sin6_family = AF_INET6;
428 v6.sin6_port = htons (53);
429 #if HAVE_SOCKADDR_IN_SIN_LEN
430 v6.sin6_len = (u_char) salen;
432 sa = (struct sockaddr *) &v6;
440 if (NULL == (rs = get_request_socket (ctx,
443 GNUNET_assert (NULL == rs->rc);
444 if (NULL != rs->dnsout4)
445 dnsout = rs->dnsout4;
447 dnsout = rs->dnsout6;
450 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
451 _("Configured DNS exit `%s' is not working / valid.\n"),
455 GNUNET_memcpy (&rs->addr,
462 GNUNET_NETWORK_socket_sendto (dnsout,
467 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
468 _("Failed to send DNS request to %s\n"),
469 GNUNET_a2s (sa, salen));
470 rs->timeout = GNUNET_TIME_relative_to_absolute (REQUEST_TIMEOUT);
476 * Actually do the reading of a DNS packet from our UDP socket and see
477 * if we have a valid, matching, pending request.
479 * @param rs request socket with callback details
480 * @param dnsout socket to read from
481 * @return #GNUNET_OK on success, #GNUNET_NO on drop, #GNUNET_SYSERR on IO-errors (closed socket)
484 do_dns_read (struct GNUNET_DNSSTUB_RequestSocket *rs,
485 struct GNUNET_NETWORK_Handle *dnsout)
487 struct sockaddr_storage addr;
489 struct GNUNET_TUN_DnsHeader *dns;
494 if (0 != ioctl (GNUNET_NETWORK_get_fd (dnsout),
498 /* conservative choice: */
502 /* port the code above? */
505 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
506 "Receiving %d byte DNS reply\n",
509 unsigned char buf[len] GNUNET_ALIGN;
511 addrlen = sizeof (addr);
512 memset (&addr, 0, sizeof (addr));
513 r = GNUNET_NETWORK_socket_recvfrom (dnsout,
516 (struct sockaddr*) &addr,
520 GNUNET_log_strerror (GNUNET_ERROR_TYPE_ERROR,
522 GNUNET_NETWORK_socket_close (dnsout);
523 return GNUNET_SYSERR;
525 if (sizeof (struct GNUNET_TUN_DnsHeader) > r)
527 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
528 _("Received DNS response that is too small (%u bytes)"),
532 dns = (struct GNUNET_TUN_DnsHeader *) buf;
533 if ( (addrlen != rs->addrlen) ||
535 GNUNET_TUN_sockaddr_cmp ((struct sockaddr *) &rs->addr,
536 (struct sockaddr *) &addr,
538 (0 == GNUNET_TIME_absolute_get_remaining (rs->timeout).rel_value_us) )
540 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
541 "Request timeout or invalid sender address; ignoring reply\n");
555 * Read a DNS response from the (unhindered) UDP-Socket
557 * @param cls socket to read from
560 read_response (void *cls)
562 struct GNUNET_DNSSTUB_RequestSocket *rs = cls;
563 struct GNUNET_NETWORK_FDSet *rset;
564 const struct GNUNET_SCHEDULER_TaskContext *tc;
566 rs->read_task = NULL;
567 tc = GNUNET_SCHEDULER_get_task_context ();
568 if (0 == (tc->reason & GNUNET_SCHEDULER_REASON_READ_READY))
570 /* signal "failure" (from timeout) */
583 /* read and process ready sockets */
584 if ((NULL != rs->dnsout4) &&
585 (GNUNET_NETWORK_fdset_isset (tc->read_ready,
587 (GNUNET_SYSERR == do_dns_read (rs,
590 if ((NULL != rs->dnsout6) &&
591 (GNUNET_NETWORK_fdset_isset (tc->read_ready,
593 (GNUNET_SYSERR == do_dns_read (rs,
597 /* re-schedule read task */
598 rset = GNUNET_NETWORK_fdset_create ();
599 if (NULL != rs->dnsout4)
600 GNUNET_NETWORK_fdset_set (rset,
602 if (NULL != rs->dnsout6)
603 GNUNET_NETWORK_fdset_set (rset,
605 rs->read_task = GNUNET_SCHEDULER_add_select (GNUNET_SCHEDULER_PRIORITY_DEFAULT,
606 GNUNET_TIME_absolute_get_remaining (rs->timeout),
611 GNUNET_NETWORK_fdset_destroy (rset);
616 * Cancel DNS resolution.
618 * @param rs resolution to cancel
621 GNUNET_DNSSTUB_resolve_cancel (struct GNUNET_DNSSTUB_RequestSocket *rs)
624 if (NULL != rs->retry_task)
626 GNUNET_SCHEDULER_cancel (rs->retry_task);
627 rs->retry_task = NULL;
633 * Start a DNS stub resolver.
635 * @param dns_ip target IP address to use
636 * @return NULL on error
638 struct GNUNET_DNSSTUB_Context *
639 GNUNET_DNSSTUB_start (const char *dns_ip)
641 struct GNUNET_DNSSTUB_Context *ctx;
643 ctx = GNUNET_new (struct GNUNET_DNSSTUB_Context);
645 ctx->dns_exit = GNUNET_strdup (dns_ip);
651 * Cleanup DNSSTUB resolver.
653 * @param ctx stub resolver to clean up
656 GNUNET_DNSSTUB_stop (struct GNUNET_DNSSTUB_Context *ctx)
660 for (i=0;i<DNS_SOCKET_MAX;i++)
661 cleanup_rs (&ctx->sockets[i]);
662 if (NULL != ctx->dns_exit)
664 GNUNET_free (ctx->dns_exit);
665 ctx->dns_exit = NULL;
671 /* end of dnsstub.c */