about summary refs log tree commit diff
path: root/nscd/aicache.c
blob: 6f7b038021746e22e39eb6f96688a27ef5c61b9a (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
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
/* Cache handling for host lookup.
   Copyright (C) 2004-2018 Free Software Foundation, Inc.
   This file is part of the GNU C Library.
   Contributed by Ulrich Drepper <drepper@redhat.com>, 2004.

   This program 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; version 2 of the License, or
   (at your option) any later version.

   This program 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 this program; if not, see <http://www.gnu.org/licenses/>.  */

#include <assert.h>
#include <errno.h>
#include <libintl.h>
#include <netdb.h>
#include <nss.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <sys/mman.h>
#include <resolv/resolv-internal.h>
#include <resolv/resolv_context.h>
#include <resolv/res_use_inet6.h>

#include "dbg_log.h"
#include "nscd.h"
#ifdef HAVE_SENDFILE
# include <kernel-features.h>
#endif


typedef enum nss_status (*nss_gethostbyname4_r)
  (const char *name, struct gaih_addrtuple **pat,
   char *buffer, size_t buflen, int *errnop,
   int *h_errnop, int32_t *ttlp);
typedef enum nss_status (*nss_gethostbyname3_r)
  (const char *name, int af, struct hostent *host,
   char *buffer, size_t buflen, int *errnop,
   int *h_errnop, int32_t *, char **);
typedef enum nss_status (*nss_getcanonname_r)
  (const char *name, char *buffer, size_t buflen, char **result,
   int *errnop, int *h_errnop);


static const ai_response_header notfound =
{
  .version = NSCD_VERSION,
  .found = 0,
  .naddrs = 0,
  .addrslen = 0,
  .canonlen = 0,
  .error = 0
};


static time_t
addhstaiX (struct database_dyn *db, int fd, request_header *req,
	   void *key, uid_t uid, struct hashentry *const he,
	   struct datahead *dh)
{
  /* Search for the entry matching the key.  Please note that we don't
     look again in the table whether the dataset is now available.  We
     simply insert it.  It does not matter if it is in there twice.  The
     pruning function only will look at the timestamp.  */

  /* We allocate all data in one memory block: the iov vector,
     the response header and the dataset itself.  */
  struct dataset
  {
    struct datahead head;
    ai_response_header resp;
    char strdata[0];
  } *dataset = NULL;

  if (__glibc_unlikely (debug_level > 0))
    {
      if (he == NULL)
	dbg_log (_("Haven't found \"%s\" in hosts cache!"), (char *) key);
      else
	dbg_log (_("Reloading \"%s\" in hosts cache!"), (char *) key);
    }

  static service_user *hosts_database;
  service_user *nip;
  int no_more;
  int rc6 = 0;
  int rc4 = 0;
  int herrno = 0;

  if (hosts_database == NULL)
    no_more = __nss_database_lookup ("hosts", NULL,
				     "dns [!UNAVAIL=return] files",
				     &hosts_database);
  else
    no_more = 0;
  nip = hosts_database;

  /* Initialize configurations.  If we are looking for both IPv4 and
     IPv6 address we don't want the lookup functions to automatically
     promote IPv4 addresses to IPv6 addresses.  Therefore, use the
     _no_inet6 variant.  */
  struct resolv_context *ctx = __resolv_context_get ();
  bool enable_inet6 = __resolv_context_disable_inet6 (ctx);
  if (ctx == NULL)
    no_more = 1;

  size_t tmpbuf6len = 1024;
  char *tmpbuf6 = alloca (tmpbuf6len);
  size_t tmpbuf4len = 0;
  char *tmpbuf4 = NULL;
  int32_t ttl = INT32_MAX;
  ssize_t total = 0;
  char *key_copy = NULL;
  bool alloca_used = false;
  time_t timeout = MAX_TIMEOUT_VALUE;

  while (!no_more)
    {
      void *cp;
      int status[2] = { NSS_STATUS_UNAVAIL, NSS_STATUS_UNAVAIL };
      int naddrs = 0;
      size_t addrslen = 0;
      char *canon = NULL;
      size_t canonlen;

      nss_gethostbyname4_r fct4 = __nss_lookup_function (nip,
							 "gethostbyname4_r");
      if (fct4 != NULL)
	{
	  struct gaih_addrtuple atmem;
	  struct gaih_addrtuple *at;
	  while (1)
	    {
	      at = &atmem;
	      rc6 = 0;
	      herrno = 0;
	      status[1] = DL_CALL_FCT (fct4, (key, &at, tmpbuf6, tmpbuf6len,
					      &rc6, &herrno, &ttl));
	      if (rc6 != ERANGE || (herrno != NETDB_INTERNAL
				    && herrno != TRY_AGAIN))
		break;
	      tmpbuf6 = extend_alloca (tmpbuf6, tmpbuf6len, 2 * tmpbuf6len);
	    }

	  if (rc6 != 0 && herrno == NETDB_INTERNAL)
	    goto out;

	  if (status[1] != NSS_STATUS_SUCCESS)
	    goto next_nip;

	  /* We found the data.  Count the addresses and the size.  */
	  for (const struct gaih_addrtuple *at2 = at = &atmem; at2 != NULL;
	       at2 = at2->next)
	    {
	      ++naddrs;
	      /* We do not handle anything other than IPv4 and IPv6
		 addresses.  The getaddrinfo implementation does not
		 either so it is not worth trying to do more.  */
	      if (at2->family == AF_INET)
		addrslen += INADDRSZ;
	      else if (at2->family == AF_INET6)
		addrslen += IN6ADDRSZ;
	    }
	  canon = at->name;
	  canonlen = strlen (canon) + 1;

	  total = sizeof (*dataset) + naddrs + addrslen + canonlen;

	  /* Now we can allocate the data structure.  If the TTL of the
	     entry is reported as zero do not cache the entry at all.  */
	  if (ttl != 0 && he == NULL)
	    dataset = (struct dataset *) mempool_alloc (db, total
							+ req->key_len, 1);

	  if (dataset == NULL)
	    {
	      /* We cannot permanently add the result in the moment.  But
		 we can provide the result as is.  Store the data in some
		 temporary memory.  */
	      dataset = (struct dataset *) alloca (total + req->key_len);

	      /* We cannot add this record to the permanent database.  */
	      alloca_used = true;
	    }

	  /* Fill in the address and address families.  */
	  char *addrs = dataset->strdata;
	  uint8_t *family = (uint8_t *) (addrs + addrslen);

	  for (const struct gaih_addrtuple *at2 = at; at2 != NULL;
	       at2 = at2->next)
	    {
	      *family++ = at2->family;
	      if (at2->family == AF_INET)
		addrs = mempcpy (addrs, at2->addr, INADDRSZ);
	      else if (at2->family == AF_INET6)
		addrs = mempcpy (addrs, at2->addr, IN6ADDRSZ);
	    }

	  cp = family;
	}
      else
	{
	  /* Prefer the function which also returns the TTL and
	     canonical name.  */
	  nss_gethostbyname3_r fct = __nss_lookup_function (nip,
							    "gethostbyname3_r");
	  if (fct == NULL)
	    fct = __nss_lookup_function (nip, "gethostbyname2_r");

	  if (fct == NULL)
	    goto next_nip;

	  struct hostent th[2];

	  /* Collect IPv6 information first.  */
	  while (1)
	    {
	      rc6 = 0;
	      status[0] = DL_CALL_FCT (fct, (key, AF_INET6, &th[0], tmpbuf6,
					     tmpbuf6len, &rc6, &herrno, &ttl,
					     &canon));
	      if (rc6 != ERANGE || herrno != NETDB_INTERNAL)
		break;
	      tmpbuf6 = extend_alloca (tmpbuf6, tmpbuf6len, 2 * tmpbuf6len);
	    }

	  if (rc6 != 0 && herrno == NETDB_INTERNAL)
	    goto out;

	  /* If the IPv6 lookup has been successful do not use the
	     buffer used in that lookup, use a new one.  */
	  if (status[0] == NSS_STATUS_SUCCESS && rc6 == 0)
	    {
	      tmpbuf4len = 512;
	      tmpbuf4 = alloca (tmpbuf4len);
	    }
	  else
	    {
	      tmpbuf4len = tmpbuf6len;
	      tmpbuf4 = tmpbuf6;
	    }

	  /* Next collect IPv4 information.  */
	  while (1)
	    {
	      rc4 = 0;
	      status[1] = DL_CALL_FCT (fct, (key, AF_INET, &th[1], tmpbuf4,
					     tmpbuf4len, &rc4, &herrno,
					     ttl == INT32_MAX ? &ttl : NULL,
					     canon == NULL ? &canon : NULL));
	      if (rc4 != ERANGE || herrno != NETDB_INTERNAL)
		break;
	      tmpbuf4 = extend_alloca (tmpbuf4, tmpbuf4len, 2 * tmpbuf4len);
	    }

	  if (rc4 != 0 && herrno == NETDB_INTERNAL)
	    goto out;

	  if (status[0] != NSS_STATUS_SUCCESS
	      && status[1] != NSS_STATUS_SUCCESS)
	    goto next_nip;

	  /* We found the data.  Count the addresses and the size.  */
	  for (int j = 0; j < 2; ++j)
	    if (status[j] == NSS_STATUS_SUCCESS)
	      for (int i = 0; th[j].h_addr_list[i] != NULL; ++i)
		{
		  ++naddrs;
		  addrslen += th[j].h_length;
		}

	  if (canon == NULL)
	    {
	      /* Determine the canonical name.  */
	      nss_getcanonname_r cfct;
	      cfct = __nss_lookup_function (nip, "getcanonname_r");
	      if (cfct != NULL)
		{
		  const size_t max_fqdn_len = 256;
		  char *buf = alloca (max_fqdn_len);
		  char *s;
		  int rc;

		  if (DL_CALL_FCT (cfct, (key, buf, max_fqdn_len, &s,
					  &rc, &herrno))
		      == NSS_STATUS_SUCCESS)
		    canon = s;
		  else
		    /* Set to name now to avoid using gethostbyaddr.  */
		    canon = key;
		}
	      else
		{
		  struct hostent *hstent = NULL;
		  int herrno;
		  struct hostent hstent_mem;
		  void *addr;
		  size_t addrlen;
		  int addrfamily;

		  if (status[1] == NSS_STATUS_SUCCESS)
		    {
		      addr = th[1].h_addr_list[0];
		      addrlen = sizeof (struct in_addr);
		      addrfamily = AF_INET;
		    }
		  else
		    {
		      addr = th[0].h_addr_list[0];
		      addrlen = sizeof (struct in6_addr);
		      addrfamily = AF_INET6;
		    }

		  size_t tmpbuflen = 512;
		  char *tmpbuf = alloca (tmpbuflen);
		  int rc;
		  while (1)
		    {
		      rc = __gethostbyaddr2_r (addr, addrlen, addrfamily,
					       &hstent_mem, tmpbuf, tmpbuflen,
					       &hstent, &herrno, NULL);
		      if (rc != ERANGE || herrno != NETDB_INTERNAL)
			break;
		      tmpbuf = extend_alloca (tmpbuf, tmpbuflen,
					      tmpbuflen * 2);
		    }

		  if (rc == 0)
		    {
		      if (hstent != NULL)
			canon = hstent->h_name;
		      else
			canon = key;
		    }
		}
	    }

	  canonlen = canon == NULL ? 0 : (strlen (canon) + 1);

	  total = sizeof (*dataset) + naddrs + addrslen + canonlen;


	  /* Now we can allocate the data structure.  If the TTL of the
	     entry is reported as zero do not cache the entry at all.  */
	  if (ttl != 0 && he == NULL)
	    dataset = (struct dataset *) mempool_alloc (db, total
							+ req->key_len, 1);

	  if (dataset == NULL)
	    {
	      /* We cannot permanently add the result in the moment.  But
		 we can provide the result as is.  Store the data in some
		 temporary memory.  */
	      dataset = (struct dataset *) alloca (total + req->key_len);

	      /* We cannot add this record to the permanent database.  */
	      alloca_used = true;
	    }

	  /* Fill in the address and address families.  */
	  char *addrs = dataset->strdata;
	  uint8_t *family = (uint8_t *) (addrs + addrslen);

	  for (int j = 0; j < 2; ++j)
	    if (status[j] == NSS_STATUS_SUCCESS)
	      for (int i = 0; th[j].h_addr_list[i] != NULL; ++i)
		{
		  addrs = mempcpy (addrs, th[j].h_addr_list[i],
				   th[j].h_length);
		  *family++ = th[j].h_addrtype;
		}

	  cp = family;
	}

      timeout = datahead_init_pos (&dataset->head, total + req->key_len,
				   total - offsetof (struct dataset, resp),
				   he == NULL ? 0 : dh->nreloads + 1,
				   ttl == INT32_MAX ? db->postimeout : ttl);

      /* Fill in the rest of the dataset.  */
      dataset->resp.version = NSCD_VERSION;
      dataset->resp.found = 1;
      dataset->resp.naddrs = naddrs;
      dataset->resp.addrslen = addrslen;
      dataset->resp.canonlen = canonlen;
      dataset->resp.error = NETDB_SUCCESS;

      if (canon != NULL)
	cp = mempcpy (cp, canon, canonlen);

      key_copy = memcpy (cp, key, req->key_len);

      assert (cp == (char *) dataset + total);

      /* Now we can determine whether on refill we have to create a
	 new record or not.  */
      if (he != NULL)
	{
	  assert (fd == -1);

	  if (total + req->key_len == dh->allocsize
	      && total - offsetof (struct dataset, resp) == dh->recsize
	      && memcmp (&dataset->resp, dh->data,
			 dh->allocsize - offsetof (struct dataset,
						   resp)) == 0)
	    {
	      /* The data has not changed.  We will just bump the
		 timeout value.  Note that the new record has been
		 allocated on the stack and need not be freed.  */
	      dh->timeout = dataset->head.timeout;
	      dh->ttl = dataset->head.ttl;
	      ++dh->nreloads;
	    }
	  else
	    {
	      /* We have to create a new record.  Just allocate
		 appropriate memory and copy it.  */
	      struct dataset *newp
		= (struct dataset *) mempool_alloc (db, total + req->key_len,
						    1);
	      if (__glibc_likely (newp != NULL))
		{
		  /* Adjust pointer into the memory block.  */
		  key_copy = (char *) newp + (key_copy - (char *) dataset);

		  dataset = memcpy (newp, dataset, total + req->key_len);
		  alloca_used = false;
		}

	      /* Mark the old record as obsolete.  */
	      dh->usable = false;
	    }
	}
      else
	{
	  /* We write the dataset before inserting it to the database
	     since while inserting this thread might block and so
	     would unnecessarily let the receiver wait.  */
	  assert (fd != -1);

#ifdef HAVE_SENDFILE
	  if (__builtin_expect (db->mmap_used, 1) && !alloca_used)
	    {
	      assert (db->wr_fd != -1);
	      assert ((char *) &dataset->resp > (char *) db->data);
	      assert ((char *) dataset - (char *) db->head + total
		      <= (sizeof (struct database_pers_head)
			  + db->head->module * sizeof (ref_t)
			  + db->head->data_size));
# ifndef __ASSUME_SENDFILE
	      ssize_t written;
	      written =
# endif
		sendfileall (fd, db->wr_fd, (char *) &dataset->resp
			     - (char *) db->head, dataset->head.recsize);
# ifndef __ASSUME_SENDFILE
	      if (written == -1 && errno == ENOSYS)
		goto use_write;
# endif
	    }
	  else
# ifndef __ASSUME_SENDFILE
	  use_write:
# endif
#endif
	    writeall (fd, &dataset->resp, dataset->head.recsize);
	}

      goto out;

next_nip:
      if (nss_next_action (nip, status[1]) == NSS_ACTION_RETURN)
	break;

      if (nip->next == NULL)
	no_more = -1;
      else
	nip = nip->next;
    }

  /* No result found.  Create a negative result record.  */
  if (he != NULL && rc4 == EAGAIN)
    {
      /* If we have an old record available but cannot find one now
	 because the service is not available we keep the old record
	 and make sure it does not get removed.  */
      if (reload_count != UINT_MAX && dh->nreloads == reload_count)
	/* Do not reset the value if we never not reload the record.  */
	dh->nreloads = reload_count - 1;

      /* Reload with the same time-to-live value.  */
      timeout = dh->timeout = time (NULL) + dh->ttl;
    }
  else
    {
      /* We have no data.  This means we send the standard reply for
	 this case.  */
      total = sizeof (notfound);

      if (fd != -1)
	TEMP_FAILURE_RETRY (send (fd, &notfound, total, MSG_NOSIGNAL));

      /* If we have a transient error or cannot permanently store the
	 result, so be it.  */
      if (rc4 == EAGAIN || __builtin_expect (db->negtimeout == 0, 0))
	{
	  /* Mark the old entry as obsolete.  */
	  if (dh != NULL)
	    dh->usable = false;
	  dataset = NULL;
	}
      else if ((dataset = mempool_alloc (db, (sizeof (struct dataset)
					      + req->key_len), 1)) != NULL)
	{
	  timeout = datahead_init_neg (&dataset->head,
				       sizeof (struct dataset) + req->key_len,
				       total, db->negtimeout);

	  /* This is the reply.  */
	  memcpy (&dataset->resp, &notfound, total);

	  /* Copy the key data.  */
	  key_copy = memcpy (dataset->strdata, key, req->key_len);
	}
   }

 out:
  __resolv_context_enable_inet6 (ctx, enable_inet6);
  __resolv_context_put (ctx);

  if (dataset != NULL && !alloca_used)
    {
      /* If necessary, we also propagate the data to disk.  */
      if (db->persistent)
	{
	  // XXX async OK?
	  uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1;
	  msync ((void *) pval,
		 ((uintptr_t) dataset & pagesize_m1) + total + req->key_len,
		 MS_ASYNC);
	}

      (void) cache_add (req->type, key_copy, req->key_len, &dataset->head,
			true, db, uid, he == NULL);

      pthread_rwlock_unlock (&db->lock);

      /* Mark the old entry as obsolete.  */
      if (dh != NULL)
	dh->usable = false;
    }

  return timeout;
}


void
addhstai (struct database_dyn *db, int fd, request_header *req, void *key,
	  uid_t uid)
{
  addhstaiX (db, fd, req, key, uid, NULL, NULL);
}


time_t
readdhstai (struct database_dyn *db, struct hashentry *he, struct datahead *dh)
{
  request_header req =
    {
      .type = GETAI,
      .key_len = he->len
    };

  return addhstaiX (db, -1, &req, db->data + he->key, he->owner, he, dh);
}