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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_dnsstub_lib.h"
30 * Timeout for an external (Internet-DNS) DNS resolution
32 #define REQUEST_TIMEOUT GNUNET_TIME_relative_multiply (GNUNET_TIME_UNIT_SECONDS, 5)
35 * How many DNS sockets do we open at most at the same time?
36 * (technical socket maximum is this number x2 for IPv4+IPv6)
38 #define DNS_SOCKET_MAX 128
42 * UDP socket we are using for sending DNS requests to the Internet.
44 struct GNUNET_DNSSTUB_RequestSocket
48 * UDP socket we use for this request for IPv4
50 struct GNUNET_NETWORK_Handle *dnsout4;
53 * UDP socket we use for this request for IPv6
55 struct GNUNET_NETWORK_Handle *dnsout6;
58 * Function to call with result.
60 GNUNET_DNSSTUB_ResultCallback rc;
68 * Task for reading from dnsout4 and dnsout6.
70 struct GNUNET_SCHEDULER_Task * read_task;
73 * When should this request time out?
75 struct GNUNET_TIME_Absolute timeout;
78 * Address we sent the DNS request to.
80 struct sockaddr_storage addr;
83 * Number of bytes in @e addr.
91 * Handle to the stub resolver.
93 struct GNUNET_DNSSTUB_Context
97 * Array of all open sockets for DNS requests.
99 struct GNUNET_DNSSTUB_RequestSocket sockets[DNS_SOCKET_MAX];
102 * IP address to use for the DNS server if we are a DNS exit service
103 * (for VPN via cadet); otherwise NULL.
111 * We're done with a `struct GNUNET_DNSSTUB_RequestSocket`, close it for now.
113 * @param rs request socket to clean up
116 cleanup_rs (struct GNUNET_DNSSTUB_RequestSocket *rs)
118 if (NULL != rs->dnsout4)
120 GNUNET_NETWORK_socket_close (rs->dnsout4);
123 if (NULL != rs->dnsout6)
125 GNUNET_NETWORK_socket_close (rs->dnsout6);
128 if (NULL != rs->read_task)
130 GNUNET_SCHEDULER_cancel (rs->read_task);
131 rs->read_task = NULL;
137 * Open source port for sending DNS requests
139 * @param af AF_INET or AF_INET6
140 * @return #GNUNET_OK on success
142 static struct GNUNET_NETWORK_Handle *
145 struct sockaddr_in a4;
146 struct sockaddr_in6 a6;
149 struct GNUNET_NETWORK_Handle *ret;
151 ret = GNUNET_NETWORK_socket_create (af, SOCK_DGRAM, 0);
157 memset (&a4, 0, alen = sizeof (struct sockaddr_in));
158 sa = (struct sockaddr *) &a4;
161 memset (&a6, 0, alen = sizeof (struct sockaddr_in6));
162 sa = (struct sockaddr *) &a6;
166 GNUNET_NETWORK_socket_close (ret);
170 if (GNUNET_OK != GNUNET_NETWORK_socket_bind (ret,
174 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
175 _("Could not bind to any port: %s\n"),
177 GNUNET_NETWORK_socket_close (ret);
185 * Read a DNS response from the (unhindered) UDP-Socket
187 * @param cls socket to read from
190 read_response (void *cls);
194 * Get a socket of the specified address family to send out a
195 * UDP DNS request to the Internet.
197 * @param ctx the DNSSTUB context
198 * @param af desired address family
199 * @return NULL on error (given AF not "supported")
201 static struct GNUNET_DNSSTUB_RequestSocket *
202 get_request_socket (struct GNUNET_DNSSTUB_Context *ctx,
205 struct GNUNET_DNSSTUB_RequestSocket *rs;
206 struct GNUNET_NETWORK_FDSet *rset;
208 rs = &ctx->sockets[GNUNET_CRYPTO_random_u32 (GNUNET_CRYPTO_QUALITY_NONCE,
210 rs->timeout = GNUNET_TIME_relative_to_absolute (REQUEST_TIMEOUT);
214 if (NULL == rs->dnsout4)
215 rs->dnsout4 = open_socket (AF_INET);
218 if (NULL == rs->dnsout6)
219 rs->dnsout6 = open_socket (AF_INET6);
224 if (NULL != rs->read_task)
226 GNUNET_SCHEDULER_cancel (rs->read_task);
227 rs->read_task = NULL;
229 if ( (NULL == rs->dnsout4) &&
230 (NULL == rs->dnsout6) )
232 rset = GNUNET_NETWORK_fdset_create ();
233 if (NULL != rs->dnsout4)
234 GNUNET_NETWORK_fdset_set (rset, rs->dnsout4);
235 if (NULL != rs->dnsout6)
236 GNUNET_NETWORK_fdset_set (rset, rs->dnsout6);
237 rs->read_task = GNUNET_SCHEDULER_add_select (GNUNET_SCHEDULER_PRIORITY_DEFAULT,
242 GNUNET_NETWORK_fdset_destroy (rset);
248 * Perform DNS resolution.
250 * @param ctx stub resolver to use
251 * @param sa the socket address
252 * @param sa_len the socket length
253 * @param request DNS request to transmit
254 * @param request_len number of bytes in msg
255 * @param rc function to call with result
256 * @param rc_cls closure for 'rc'
257 * @return socket used for the request, NULL on error
259 struct GNUNET_DNSSTUB_RequestSocket *
260 GNUNET_DNSSTUB_resolve (struct GNUNET_DNSSTUB_Context *ctx,
261 const struct sockaddr *sa,
265 GNUNET_DNSSTUB_ResultCallback rc,
268 struct GNUNET_DNSSTUB_RequestSocket *rs;
269 struct GNUNET_NETWORK_Handle *ret;
273 if (NULL == (rs = get_request_socket (ctx, af)))
275 if (NULL != rs->dnsout4)
279 GNUNET_assert (NULL != ret);
283 rs->addrlen = sa_len;
287 GNUNET_NETWORK_socket_sendto (ret,
292 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
293 _("Failed to send DNS request to %s\n"),
294 GNUNET_a2s (sa, sa_len));
296 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
297 _("Sent DNS request to %s\n"),
298 GNUNET_a2s (sa, sa_len));
304 * Perform DNS resolution using our default IP from init.
306 * @param ctx stub resolver to use
307 * @param request DNS request to transmit
308 * @param request_len number of bytes in msg
309 * @param rc function to call with result
310 * @param rc_cls closure for 'rc'
311 * @return socket used for the request, NULL on error
313 struct GNUNET_DNSSTUB_RequestSocket *
314 GNUNET_DNSSTUB_resolve2 (struct GNUNET_DNSSTUB_Context *ctx,
317 GNUNET_DNSSTUB_ResultCallback rc,
321 struct sockaddr_in v4;
322 struct sockaddr_in6 v6;
325 struct GNUNET_NETWORK_Handle *dnsout;
326 struct GNUNET_DNSSTUB_RequestSocket *rs;
328 memset (&v4, 0, sizeof (v4));
329 memset (&v6, 0, sizeof (v6));
330 if (1 == inet_pton (AF_INET, ctx->dns_exit, &v4.sin_addr))
333 v4.sin_family = AF_INET;
334 v4.sin_port = htons (53);
335 #if HAVE_SOCKADDR_IN_SIN_LEN
336 v4.sin_len = (u_char) salen;
338 sa = (struct sockaddr *) &v4;
341 else if (1 == inet_pton (AF_INET6, ctx->dns_exit, &v6.sin6_addr))
344 v6.sin6_family = AF_INET6;
345 v6.sin6_port = htons (53);
346 #if HAVE_SOCKADDR_IN_SIN_LEN
347 v6.sin6_len = (u_char) salen;
349 sa = (struct sockaddr *) &v6;
357 if (NULL == (rs = get_request_socket (ctx, af)))
359 if (NULL != rs->dnsout4)
360 dnsout = rs->dnsout4;
362 dnsout = rs->dnsout6;
365 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
366 _("Configured DNS exit `%s' is not working / valid.\n"),
377 GNUNET_NETWORK_socket_sendto (dnsout,
379 request_len, sa, salen))
380 GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
381 _("Failed to send DNS request to %s\n"),
382 GNUNET_a2s (sa, salen));
383 rs->timeout = GNUNET_TIME_relative_to_absolute (REQUEST_TIMEOUT);
391 * Actually do the reading of a DNS packet from our UDP socket and see
392 * if we have a valid, matching, pending request.
394 * @param rs request socket with callback details
395 * @param dnsout socket to read from
396 * @return #GNUNET_OK on success, #GNUNET_NO on drop, #GNUNET_SYSERR on IO-errors (closed socket)
399 do_dns_read (struct GNUNET_DNSSTUB_RequestSocket *rs,
400 struct GNUNET_NETWORK_Handle *dnsout)
402 struct sockaddr_storage addr;
404 struct GNUNET_TUN_DnsHeader *dns;
409 if (0 != ioctl (GNUNET_NETWORK_get_fd (dnsout), FIONREAD, &len))
411 /* conservative choice: */
415 /* port the code above? */
418 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
419 "Receiving %d byte DNS reply\n",
422 unsigned char buf[len] GNUNET_ALIGN;
424 addrlen = sizeof (addr);
425 memset (&addr, 0, sizeof (addr));
426 r = GNUNET_NETWORK_socket_recvfrom (dnsout,
428 (struct sockaddr*) &addr, &addrlen);
431 GNUNET_log_strerror (GNUNET_ERROR_TYPE_ERROR, "recvfrom");
432 GNUNET_NETWORK_socket_close (dnsout);
433 return GNUNET_SYSERR;
435 if (sizeof (struct GNUNET_TUN_DnsHeader) > r)
437 GNUNET_log (GNUNET_ERROR_TYPE_ERROR,
438 _("Received DNS response that is too small (%u bytes)"),
442 dns = (struct GNUNET_TUN_DnsHeader *) buf;
443 if ( (addrlen != rs->addrlen) ||
444 (0 != memcmp (&rs->addr,
447 (0 == GNUNET_TIME_absolute_get_remaining (rs->timeout).rel_value_us) )
449 GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
450 "Request timeout or invalid sender address; ignoring reply\n");
464 * Read a DNS response from the (unhindered) UDP-Socket
466 * @param cls socket to read from
469 read_response (void *cls)
471 struct GNUNET_DNSSTUB_RequestSocket *rs = cls;
472 struct GNUNET_NETWORK_FDSet *rset;
473 const struct GNUNET_SCHEDULER_TaskContext *tc;
475 rs->read_task = NULL;
476 tc = GNUNET_SCHEDULER_get_task_context ();
477 if (0 == (tc->reason & GNUNET_SCHEDULER_REASON_READ_READY))
483 /* read and process ready sockets */
484 if ((NULL != rs->dnsout4) &&
485 (GNUNET_NETWORK_fdset_isset (tc->read_ready, rs->dnsout4)) &&
486 (GNUNET_SYSERR == do_dns_read (rs, rs->dnsout4)))
488 if ((NULL != rs->dnsout6) &&
489 (GNUNET_NETWORK_fdset_isset (tc->read_ready, rs->dnsout6)) &&
490 (GNUNET_SYSERR == do_dns_read (rs, rs->dnsout6)))
493 /* re-schedule read task */
494 rset = GNUNET_NETWORK_fdset_create ();
495 if (NULL != rs->dnsout4)
496 GNUNET_NETWORK_fdset_set (rset, rs->dnsout4);
497 if (NULL != rs->dnsout6)
498 GNUNET_NETWORK_fdset_set (rset, rs->dnsout6);
499 rs->read_task = GNUNET_SCHEDULER_add_select (GNUNET_SCHEDULER_PRIORITY_DEFAULT,
500 GNUNET_TIME_absolute_get_remaining (rs->timeout),
504 GNUNET_NETWORK_fdset_destroy (rset);
509 * Cancel DNS resolution.
511 * @param rs resolution to cancel
514 GNUNET_DNSSTUB_resolve_cancel (struct GNUNET_DNSSTUB_RequestSocket *rs)
521 * Start a DNS stub resolver.
523 * @param dns_ip target IP address to use
524 * @return NULL on error
526 struct GNUNET_DNSSTUB_Context *
527 GNUNET_DNSSTUB_start (const char *dns_ip)
529 struct GNUNET_DNSSTUB_Context *ctx;
531 ctx = GNUNET_new (struct GNUNET_DNSSTUB_Context);
533 ctx->dns_exit = GNUNET_strdup (dns_ip);
539 * Cleanup DNSSTUB resolver.
541 * @param ctx stub resolver to clean up
544 GNUNET_DNSSTUB_stop (struct GNUNET_DNSSTUB_Context *ctx)
548 for (i=0;i<DNS_SOCKET_MAX;i++)
549 cleanup_rs (&ctx->sockets[i]);
550 if (NULL != ctx->dns_exit)
552 GNUNET_free (ctx->dns_exit);
553 ctx->dns_exit = NULL;
559 /* end of dnsstub.c */