aboutsummaryrefslogtreecommitdiff
path: root/src/dns/dns_api.c
blob: a280265da0d588297b83676b17caec384babb5ce (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
/*
      This file is part of GNUnet
      (C) 2012 Christian Grothoff (and other contributing authors)

      GNUnet is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published
      by the Free Software Foundation; either version 2, or (at your
      option) any later version.

      GNUnet is distributed in the hope that it will be useful, but
      WITHOUT ANY WARRANTY; without even the implied warranty of
      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
      General Public License for more details.

      You should have received a copy of the GNU General Public License
      along with GNUnet; see the file COPYING.  If not, write to the
      Free Software Foundation, Inc., 59 Temple Place - Suite 330,
      Boston, MA 02111-1307, USA.
 */

/**
 * @file dns/dns_api.c
 * @brief API to access the DNS service. 
 * @author Christian Grothoff
 */
#include "platform.h"
#include "gnunet_dns_service.h"
#include "dns.h"


/**
 * Reply to send to service.
 */
struct ReplyQueueEntry
{
  /**
   * Kept in DLL.
   */
  struct ReplyQueueEntry *next;

  /**
   * Kept in DLL.
   */
  struct ReplyQueueEntry *prev;

  /**
   * Message to transmit, allocated at the end of this struct.
   */
  const struct GNUNET_MessageHeader *msg;

};


/**
 * Handle to identify an individual DNS request.
 */
struct GNUNET_DNS_RequestHandle
{

  /**
   * Handle to DNS API.
   */
  struct GNUNET_DNS_Handle *dh;

  /**
   * Stored in network byte order (as for us, it is just a random number).
   */
  uint64_t request_id;

  /**
   * Re-connect counter, to make sure we did not reconnect in the meantime.
   */
  uint32_t generation;

};


/**
 * DNS handle
 */
struct GNUNET_DNS_Handle
{

  /**
   * Connection to DNS service, or NULL.
   */
  struct GNUNET_CLIENT_Connection *dns_connection;

  /**
   * Handle to active transmission request, or NULL.
   */
  struct GNUNET_CLIENT_TransmitHandle *dns_transmit_handle;

  /**
   * Configuration to use.
   */
  const struct GNUNET_CONFIGURATION_Handle *cfg;

  /**
   * Function to call to get replies.
   */
  GNUNET_DNS_RequestHandler rh;
  
  /**
   * Closure for 'rh'.
   */
  void *rh_cls;

  /**
   * Head of replies to transmit.
   */
  struct ReplyQueueEntry *rq_head;

  /**
   * Tail of replies to transmit.
   */
  struct ReplyQueueEntry *rq_tail;

  /**
   * Task to reconnect to the service.
   */
  GNUNET_SCHEDULER_TaskIdentifier reconnect_task;

  /**
   * Re-connect counter, to make sure we did not reconnect in the meantime.
   */
  uint32_t generation;
  
  /**
   * Flags for events we care about.
   */
  enum GNUNET_DNS_Flags flags;

  /**
   * Did we start the receive loop yet?
   */
  int in_receive;

  /**
   * Number of GNUNET_DNS_RequestHandles we have outstanding. Must be 0 before
   * we can be disconnected.
   */
  unsigned int pending_requests;
};


/**
 * Add the given reply to our transmission queue and trigger sending if needed.
 *
 * @param dh handle with the connection
 * @param qe reply to queue
 */
static void
queue_reply (struct GNUNET_DNS_Handle *dh,
	     struct ReplyQueueEntry *qe);


/**
 * Reconnect to the DNS service.
 *
 * @param cls handle with the connection to connect
 * @param tc scheduler context (unused)
 */
static void
reconnect (void *cls,
	   const struct GNUNET_SCHEDULER_TaskContext *tc)
{
  struct GNUNET_DNS_Handle *dh = cls;
  struct ReplyQueueEntry *qe;
  struct GNUNET_DNS_Register *msg;

  dh->reconnect_task = GNUNET_SCHEDULER_NO_TASK;
  dh->dns_connection = GNUNET_CLIENT_connect ("dns", dh->cfg);
  if (NULL == dh->dns_connection)
    return;
  dh->generation++;
  qe = GNUNET_malloc (sizeof (struct ReplyQueueEntry) +
		      sizeof (struct GNUNET_DNS_Register));
  msg = (struct GNUNET_DNS_Register*) &qe[1];
  qe->msg = &msg->header;
  msg->header.size = htons (sizeof (struct GNUNET_DNS_Register));
  msg->header.type = htons (GNUNET_MESSAGE_TYPE_DNS_CLIENT_INIT);
  msg->flags = htonl (dh->flags);
  queue_reply (dh, qe);
}


/**
 * Disconnect from the DNS service.
 *
 * @param dh handle with the connection to disconnect
 */
static void
disconnect (struct GNUNET_DNS_Handle *dh)
{
  struct ReplyQueueEntry *qe;

  if (NULL != dh->dns_transmit_handle)
  {
    GNUNET_CLIENT_notify_transmit_ready_cancel (dh->dns_transmit_handle);
    dh->dns_transmit_handle = NULL;
  }
  if (NULL != dh->dns_connection)
  {
    GNUNET_CLIENT_disconnect (dh->dns_connection, GNUNET_NO);
    dh->dns_connection = NULL;
  }
  while (NULL != (qe = dh->rq_head))
  {
    GNUNET_CONTAINER_DLL_remove (dh->rq_head,
				 dh->rq_tail,
				 qe);
    GNUNET_free (qe);
  }
  dh->in_receive = GNUNET_NO;
}


/**
 * This receives packets from the DNS service and calls the application to
 * handle it.
 *
 * @param cls the struct GNUNET_DNS_Handle
 * @param msg message from the service (request)
 */
static void
request_handler (void *cls,
		 const struct GNUNET_MessageHeader *msg)
{
  struct GNUNET_DNS_Handle *dh = cls;
  const struct GNUNET_DNS_Request *req;
  struct GNUNET_DNS_RequestHandle *rh;
  size_t payload_length;

  /* the service disconnected, reconnect after short wait */
  if (msg == NULL)
  {
    disconnect (dh);
    dh->reconnect_task =
        GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_SECONDS,
                                      &reconnect, dh);
    return;
  }
  if ( (ntohs (msg->type) != GNUNET_MESSAGE_TYPE_DNS_CLIENT_REQUEST) ||
       (ntohs (msg->size) < sizeof (struct GNUNET_DNS_Request)) )
  {
    /* the service did something strange, reconnect immediately */
    GNUNET_break (0);
    disconnect (dh);
    dh->reconnect_task = GNUNET_SCHEDULER_add_now (&reconnect, dh);
    return;
  }
  req = (const struct GNUNET_DNS_Request *) msg;
  GNUNET_break (ntohl (req->reserved) == 0);
  payload_length = ntohs (req->header.size) - sizeof (struct GNUNET_DNS_Request);
  GNUNET_CLIENT_receive (dh->dns_connection, 
			 &request_handler, dh,
                         GNUNET_TIME_UNIT_FOREVER_REL);

  /* finally, pass request to callback for answers */
  rh = GNUNET_malloc (sizeof (struct GNUNET_DNS_RequestHandle));
  rh->dh =dh;
  rh->request_id = req->request_id;
  rh->generation = dh->generation;  
  dh->pending_requests++;
  dh->rh (dh->rh_cls,
	  rh,
	  payload_length,
	  (const char*) &req[1]);
}


/**
 * Callback called by notify_transmit_ready; sends DNS replies
 * to the DNS service.
 *
 * @param cls the struct GNUNET_DNS_Handle
 * @param size number of bytes available in buf
 * @param buf where to copy the message for transmission
 * @return number of bytes copied to buf
 */
static size_t
send_response (void *cls, size_t size, void *buf)
{
  struct GNUNET_DNS_Handle *dh = cls;
  struct ReplyQueueEntry *qe;
  size_t len;
 
  dh->dns_transmit_handle = NULL;
  if (NULL == buf)
  {
    disconnect (dh);
    dh->reconnect_task =
      GNUNET_SCHEDULER_add_delayed (GNUNET_TIME_UNIT_SECONDS,
				    &reconnect, dh);
    return 0;
  }
  qe = dh->rq_head;
  if (NULL == qe)
    return 0;
  len = ntohs (qe->msg->size);
  if (len > size)
  {   
    dh->dns_transmit_handle =
      GNUNET_CLIENT_notify_transmit_ready (dh->dns_connection,
					   len,
					   GNUNET_TIME_UNIT_FOREVER_REL,
					   GNUNET_NO, 
					   &send_response, dh);
    return 0;
  }
  memcpy (buf, qe->msg, len);
  GNUNET_CONTAINER_DLL_remove (dh->rq_head,
			       dh->rq_tail,
			       qe);
  GNUNET_free (qe);
  if (GNUNET_NO == dh->in_receive)
  {
    dh->in_receive = GNUNET_YES;
    GNUNET_CLIENT_receive (dh->dns_connection, 
			   &request_handler, dh,
			   GNUNET_TIME_UNIT_FOREVER_REL);
  }
  if (NULL != (qe = dh->rq_head))
  {
    dh->dns_transmit_handle =
      GNUNET_CLIENT_notify_transmit_ready (dh->dns_connection,
					   ntohs (qe->msg->size),
					   GNUNET_TIME_UNIT_FOREVER_REL,
					   GNUNET_NO, 
					   &send_response, dh);
  }
  return len;
} 


/**
 * Add the given reply to our transmission queue and trigger sending if needed.
 *
 * @param dh handle with the connection
 * @param qe reply to queue
 */
static void
queue_reply (struct GNUNET_DNS_Handle *dh,
	     struct ReplyQueueEntry *qe)
{
  if (NULL == dh->dns_connection)        
  {
    GNUNET_free (qe);
    return;
  }
  GNUNET_CONTAINER_DLL_insert_tail (dh->rq_head,
				    dh->rq_tail,
				    qe);
  if (NULL != dh->dns_transmit_handle)
    return;
  /* trigger sending */ 
  dh->dns_transmit_handle =
    GNUNET_CLIENT_notify_transmit_ready (dh->dns_connection,
					 ntohs (dh->rq_head->msg->size),
					 GNUNET_TIME_UNIT_FOREVER_REL,
					 GNUNET_NO, 
					 &send_response, dh);
}


/**
 * If a GNUNET_DNS_RequestHandler calls this function, the request is
 * given to other clients or the global DNS for resolution.  Once a
 * global response has been obtained, the request handler is AGAIN
 * called to give it a chance to observe and modify the response after
 * the "normal" resolution.  It is not legal for the request handler
 * to call this function if a response is already present.
 *
 * @param rh request that should now be forwarded
 */
void
GNUNET_DNS_request_forward (struct GNUNET_DNS_RequestHandle *rh)
{
  struct ReplyQueueEntry *qe;
  struct GNUNET_DNS_Response *resp;

  GNUNET_assert (0 < rh->dh->pending_requests--);
  if (rh->generation != rh->dh->generation)
  {
    GNUNET_free (rh);
    return;
  }
  qe = GNUNET_malloc (sizeof (struct ReplyQueueEntry) +
		      sizeof (struct GNUNET_DNS_Response));
  resp = (struct GNUNET_DNS_Response*) &qe[1];
  qe->msg = &resp->header;
  resp->header.size = htons (sizeof (struct GNUNET_DNS_Response));
  resp->header.type = htons (GNUNET_MESSAGE_TYPE_DNS_CLIENT_RESPONSE);
  resp->drop_flag = htonl (1);
  resp->request_id = rh->request_id;
  queue_reply (rh->dh, qe);
  GNUNET_free (rh);
}


/**
 * If a GNUNET_DNS_RequestHandler calls this function, the request is
 * to be dropped and no response should be generated.
 *
 * @param rh request that should now be dropped
 */
void
GNUNET_DNS_request_drop (struct GNUNET_DNS_RequestHandle *rh)
{
  struct ReplyQueueEntry *qe;
  struct GNUNET_DNS_Response *resp;

  GNUNET_assert (0 < rh->dh->pending_requests--);
  if (rh->generation != rh->dh->generation)
  {
      GNUNET_free (rh);
      return;
  }
  qe = GNUNET_malloc (sizeof (struct ReplyQueueEntry) +
		      sizeof (struct GNUNET_DNS_Response));
  resp = (struct GNUNET_DNS_Response*) &qe[1];
  qe->msg = &resp->header;
  resp->header.size = htons (sizeof (struct GNUNET_DNS_Response));
  resp->header.type = htons (GNUNET_MESSAGE_TYPE_DNS_CLIENT_RESPONSE);
  resp->request_id = rh->request_id;
  resp->drop_flag = htonl (0);
  queue_reply (rh->dh, qe);
  GNUNET_free (rh);
}


/**
 * If a GNUNET_DNS_RequestHandler calls this function, the request is
 * supposed to be answered with the data provided to this call (with
 * the modifications the function might have made).
 *
 * @param rh request that should now be answered
 * @param reply_length size of reply (uint16_t to force sane size)
 * @param reply reply data
 */
void
GNUNET_DNS_request_answer (struct GNUNET_DNS_RequestHandle *rh,	 
			   uint16_t reply_length,
			   const char *reply)
{
  struct ReplyQueueEntry *qe;
  struct GNUNET_DNS_Response *resp;

  GNUNET_assert (0 < rh->dh->pending_requests--);
  if (rh->generation != rh->dh->generation)
  {
      GNUNET_free (rh);
      return;
  }
  if (reply_length + sizeof (struct GNUNET_DNS_Response) >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
  {
    GNUNET_break (0);
    GNUNET_free (rh);
    return;
  }
  qe = GNUNET_malloc (sizeof (struct ReplyQueueEntry) +
		      sizeof (struct GNUNET_DNS_Response) + reply_length);
  resp = (struct GNUNET_DNS_Response*) &qe[1];
  qe->msg = &resp->header;
  resp->header.size = htons (sizeof (struct GNUNET_DNS_Response) + reply_length);
  resp->header.type = htons (GNUNET_MESSAGE_TYPE_DNS_CLIENT_RESPONSE);
  resp->drop_flag = htonl (2);
  resp->request_id = rh->request_id;
  memcpy (&resp[1], reply, reply_length);
  queue_reply (rh->dh, qe);
  GNUNET_free (rh);
}


/**
 * Connect to the service-dns
 *
 * @param cfg configuration to use
 * @param flags when to call rh
 * @param rh function to call with DNS requests
 * @param rh_cls closure to pass to rh
 * @return DNS handle 
 */
struct GNUNET_DNS_Handle *
GNUNET_DNS_connect (const struct GNUNET_CONFIGURATION_Handle *cfg,
		    enum GNUNET_DNS_Flags flags,
		    GNUNET_DNS_RequestHandler rh,
		    void *rh_cls)
{
  struct GNUNET_DNS_Handle *dh;
  
  dh = GNUNET_malloc (sizeof (struct GNUNET_DNS_Handle));
  dh->cfg = cfg;
  dh->flags = flags;
  dh->rh = rh;
  dh->rh_cls = rh_cls;
  dh->reconnect_task = GNUNET_SCHEDULER_add_now (&reconnect, dh);
  return dh;
}


/**
 * Disconnect from the DNS service.
 *
 * @param dh DNS handle
 */
void
GNUNET_DNS_disconnect (struct GNUNET_DNS_Handle *dh)
{
  if (GNUNET_SCHEDULER_NO_TASK != dh->reconnect_task)
  {
    GNUNET_SCHEDULER_cancel (dh->reconnect_task);
    dh->reconnect_task = GNUNET_SCHEDULER_NO_TASK;
  }
  disconnect (dh);
  /* make sure client has no pending requests left over! */
  GNUNET_assert (0 == dh->pending_requests);
  GNUNET_free (dh);
}

/* end of dns_api_new.c */