1 | /* Cache handling for host lookup. |
2 | Copyright (C) 1998-2017 Free Software Foundation, Inc. |
3 | This file is part of the GNU C Library. |
4 | Contributed by Ulrich Drepper <drepper@cygnus.com>, 1998. |
5 | |
6 | This program is free software; you can redistribute it and/or modify |
7 | it under the terms of the GNU General Public License as published |
8 | by the Free Software Foundation; version 2 of the License, or |
9 | (at your option) any later version. |
10 | |
11 | This program is distributed in the hope that it will be useful, |
12 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
14 | GNU General Public License for more details. |
15 | |
16 | You should have received a copy of the GNU General Public License |
17 | along with this program; if not, see <http://www.gnu.org/licenses/>. */ |
18 | |
19 | #include <alloca.h> |
20 | #include <assert.h> |
21 | #include <errno.h> |
22 | #include <error.h> |
23 | #include <libintl.h> |
24 | #include <netdb.h> |
25 | #include <stdbool.h> |
26 | #include <stddef.h> |
27 | #include <stdio.h> |
28 | #include <stdlib.h> |
29 | #include <string.h> |
30 | #include <time.h> |
31 | #include <unistd.h> |
32 | #include <stdint.h> |
33 | #include <arpa/inet.h> |
34 | #include <arpa/nameser.h> |
35 | #include <sys/mman.h> |
36 | #include <stackinfo.h> |
37 | |
38 | #include "nscd.h" |
39 | #include "dbg_log.h" |
40 | #ifdef HAVE_SENDFILE |
41 | # include <kernel-features.h> |
42 | #endif |
43 | |
44 | |
45 | /* This is the standard reply in case the service is disabled. */ |
46 | static const hst_response_header disabled = |
47 | { |
48 | .version = NSCD_VERSION, |
49 | .found = -1, |
50 | .h_name_len = 0, |
51 | .h_aliases_cnt = 0, |
52 | .h_addrtype = -1, |
53 | .h_length = -1, |
54 | .h_addr_list_cnt = 0, |
55 | .error = NETDB_INTERNAL |
56 | }; |
57 | |
58 | /* This is the struct describing how to write this record. */ |
59 | const struct iovec hst_iov_disabled = |
60 | { |
61 | .iov_base = (void *) &disabled, |
62 | .iov_len = sizeof (disabled) |
63 | }; |
64 | |
65 | |
66 | /* This is the standard reply in case we haven't found the dataset. */ |
67 | static const hst_response_header notfound = |
68 | { |
69 | .version = NSCD_VERSION, |
70 | .found = 0, |
71 | .h_name_len = 0, |
72 | .h_aliases_cnt = 0, |
73 | .h_addrtype = -1, |
74 | .h_length = -1, |
75 | .h_addr_list_cnt = 0, |
76 | .error = HOST_NOT_FOUND |
77 | }; |
78 | |
79 | |
80 | /* This is the standard reply in case there are temporary problems. */ |
81 | static const hst_response_header tryagain = |
82 | { |
83 | .version = NSCD_VERSION, |
84 | .found = 0, |
85 | .h_name_len = 0, |
86 | .h_aliases_cnt = 0, |
87 | .h_addrtype = -1, |
88 | .h_length = -1, |
89 | .h_addr_list_cnt = 0, |
90 | .error = TRY_AGAIN |
91 | }; |
92 | |
93 | |
94 | static time_t |
95 | cache_addhst (struct database_dyn *db, int fd, request_header *req, |
96 | const void *key, struct hostent *hst, uid_t owner, |
97 | struct hashentry *const he, struct datahead *dh, int errval, |
98 | int32_t ttl) |
99 | { |
100 | bool all_written = true; |
101 | time_t t = time (NULL); |
102 | |
103 | /* We allocate all data in one memory block: the iov vector, |
104 | the response header and the dataset itself. */ |
105 | struct dataset |
106 | { |
107 | struct datahead head; |
108 | hst_response_header resp; |
109 | char strdata[0]; |
110 | } *dataset; |
111 | |
112 | assert (offsetof (struct dataset, resp) == offsetof (struct datahead, data)); |
113 | |
114 | time_t timeout = MAX_TIMEOUT_VALUE; |
115 | if (hst == NULL) |
116 | { |
117 | if (he != NULL && errval == EAGAIN) |
118 | { |
119 | /* If we have an old record available but cannot find one |
120 | now because the service is not available we keep the old |
121 | record and make sure it does not get removed. */ |
122 | if (reload_count != UINT_MAX) |
123 | /* Do not reset the value if we never not reload the record. */ |
124 | dh->nreloads = reload_count - 1; |
125 | |
126 | /* Reload with the same time-to-live value. */ |
127 | timeout = dh->timeout = t + dh->ttl; |
128 | } |
129 | else |
130 | { |
131 | /* We have no data. This means we send the standard reply for this |
132 | case. Possibly this is only temporary. */ |
133 | ssize_t total = sizeof (notfound); |
134 | assert (sizeof (notfound) == sizeof (tryagain)); |
135 | |
136 | const hst_response_header *resp = (errval == EAGAIN |
137 | ? &tryagain : ¬found); |
138 | |
139 | if (fd != -1 && |
140 | TEMP_FAILURE_RETRY (send (fd, resp, total, |
141 | MSG_NOSIGNAL)) != total) |
142 | all_written = false; |
143 | |
144 | /* If we have a transient error or cannot permanently store |
145 | the result, so be it. */ |
146 | if (errval == EAGAIN || __builtin_expect (db->negtimeout == 0, 0)) |
147 | { |
148 | /* Mark the old entry as obsolete. */ |
149 | if (dh != NULL) |
150 | dh->usable = false; |
151 | } |
152 | else if ((dataset = mempool_alloc (db, (sizeof (struct dataset) |
153 | + req->key_len), 1)) != NULL) |
154 | { |
155 | timeout = datahead_init_neg (&dataset->head, |
156 | (sizeof (struct dataset) |
157 | + req->key_len), total, |
158 | (ttl == INT32_MAX |
159 | ? db->negtimeout : ttl)); |
160 | |
161 | /* This is the reply. */ |
162 | memcpy (&dataset->resp, resp, total); |
163 | |
164 | /* Copy the key data. */ |
165 | memcpy (dataset->strdata, key, req->key_len); |
166 | |
167 | /* If necessary, we also propagate the data to disk. */ |
168 | if (db->persistent) |
169 | { |
170 | // XXX async OK? |
171 | uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1; |
172 | msync ((void *) pval, |
173 | ((uintptr_t) dataset & pagesize_m1) |
174 | + sizeof (struct dataset) + req->key_len, MS_ASYNC); |
175 | } |
176 | |
177 | (void) cache_add (req->type, &dataset->strdata, req->key_len, |
178 | &dataset->head, true, db, owner, he == NULL); |
179 | |
180 | pthread_rwlock_unlock (&db->lock); |
181 | |
182 | /* Mark the old entry as obsolete. */ |
183 | if (dh != NULL) |
184 | dh->usable = false; |
185 | } |
186 | } |
187 | } |
188 | else |
189 | { |
190 | /* Determine the I/O structure. */ |
191 | size_t h_name_len = strlen (hst->h_name) + 1; |
192 | size_t h_aliases_cnt; |
193 | uint32_t *h_aliases_len; |
194 | size_t h_addr_list_cnt; |
195 | char *addresses; |
196 | char *aliases; |
197 | char *key_copy = NULL; |
198 | char *cp; |
199 | size_t cnt; |
200 | ssize_t total; |
201 | |
202 | /* Determine the number of aliases. */ |
203 | h_aliases_cnt = 0; |
204 | for (cnt = 0; hst->h_aliases[cnt] != NULL; ++cnt) |
205 | ++h_aliases_cnt; |
206 | /* Determine the length of all aliases. */ |
207 | h_aliases_len = (uint32_t *) alloca (h_aliases_cnt * sizeof (uint32_t)); |
208 | total = 0; |
209 | for (cnt = 0; cnt < h_aliases_cnt; ++cnt) |
210 | { |
211 | h_aliases_len[cnt] = strlen (hst->h_aliases[cnt]) + 1; |
212 | total += h_aliases_len[cnt]; |
213 | } |
214 | |
215 | /* Determine the number of addresses. */ |
216 | h_addr_list_cnt = 0; |
217 | while (hst->h_addr_list[h_addr_list_cnt] != NULL) |
218 | ++h_addr_list_cnt; |
219 | |
220 | if (h_addr_list_cnt == 0) |
221 | /* Invalid entry. */ |
222 | return MAX_TIMEOUT_VALUE; |
223 | |
224 | total += (sizeof (struct dataset) |
225 | + h_name_len |
226 | + h_aliases_cnt * sizeof (uint32_t) |
227 | + h_addr_list_cnt * hst->h_length); |
228 | |
229 | /* If we refill the cache, first assume the reconrd did not |
230 | change. Allocate memory on the cache since it is likely |
231 | discarded anyway. If it turns out to be necessary to have a |
232 | new record we can still allocate real memory. */ |
233 | bool alloca_used = false; |
234 | dataset = NULL; |
235 | |
236 | /* If the record contains more than one IP address (used for |
237 | load balancing etc) don't cache the entry. This is something |
238 | the current cache handling cannot handle and it is more than |
239 | questionable whether it is worthwhile complicating the cache |
240 | handling just for handling such a special case. */ |
241 | if (he == NULL && h_addr_list_cnt == 1) |
242 | dataset = (struct dataset *) mempool_alloc (db, total + req->key_len, |
243 | 1); |
244 | |
245 | if (dataset == NULL) |
246 | { |
247 | /* We cannot permanently add the result in the moment. But |
248 | we can provide the result as is. Store the data in some |
249 | temporary memory. */ |
250 | dataset = (struct dataset *) alloca (total + req->key_len); |
251 | |
252 | /* We cannot add this record to the permanent database. */ |
253 | alloca_used = true; |
254 | } |
255 | |
256 | timeout = datahead_init_pos (&dataset->head, total + req->key_len, |
257 | total - offsetof (struct dataset, resp), |
258 | he == NULL ? 0 : dh->nreloads + 1, |
259 | ttl == INT32_MAX ? db->postimeout : ttl); |
260 | |
261 | dataset->resp.version = NSCD_VERSION; |
262 | dataset->resp.found = 1; |
263 | dataset->resp.h_name_len = h_name_len; |
264 | dataset->resp.h_aliases_cnt = h_aliases_cnt; |
265 | dataset->resp.h_addrtype = hst->h_addrtype; |
266 | dataset->resp.h_length = hst->h_length; |
267 | dataset->resp.h_addr_list_cnt = h_addr_list_cnt; |
268 | dataset->resp.error = NETDB_SUCCESS; |
269 | |
270 | /* Make sure there is no gap. */ |
271 | assert ((char *) (&dataset->resp.error + 1) == dataset->strdata); |
272 | |
273 | cp = dataset->strdata; |
274 | |
275 | cp = mempcpy (cp, hst->h_name, h_name_len); |
276 | cp = mempcpy (cp, h_aliases_len, h_aliases_cnt * sizeof (uint32_t)); |
277 | |
278 | /* The normal addresses first. */ |
279 | addresses = cp; |
280 | for (cnt = 0; cnt < h_addr_list_cnt; ++cnt) |
281 | cp = mempcpy (cp, hst->h_addr_list[cnt], hst->h_length); |
282 | |
283 | /* Then the aliases. */ |
284 | aliases = cp; |
285 | for (cnt = 0; cnt < h_aliases_cnt; ++cnt) |
286 | cp = mempcpy (cp, hst->h_aliases[cnt], h_aliases_len[cnt]); |
287 | |
288 | assert (cp |
289 | == dataset->strdata + total - offsetof (struct dataset, |
290 | strdata)); |
291 | |
292 | /* If we are adding a GETHOSTBYNAME{,v6} entry we must be prepared |
293 | that the answer we get from the NSS does not contain the key |
294 | itself. This is the case if the resolver is used and the name |
295 | is extended by the domainnames from /etc/resolv.conf. Therefore |
296 | we explicitly add the name here. */ |
297 | key_copy = memcpy (cp, key, req->key_len); |
298 | |
299 | assert ((char *) &dataset->resp + dataset->head.recsize == cp); |
300 | |
301 | /* Now we can determine whether on refill we have to create a new |
302 | record or not. */ |
303 | if (he != NULL) |
304 | { |
305 | assert (fd == -1); |
306 | |
307 | if (total + req->key_len == dh->allocsize |
308 | && total - offsetof (struct dataset, resp) == dh->recsize |
309 | && memcmp (&dataset->resp, dh->data, |
310 | dh->allocsize - offsetof (struct dataset, resp)) == 0) |
311 | { |
312 | /* The data has not changed. We will just bump the |
313 | timeout value. Note that the new record has been |
314 | allocated on the stack and need not be freed. */ |
315 | assert (h_addr_list_cnt == 1); |
316 | dh->ttl = dataset->head.ttl; |
317 | dh->timeout = dataset->head.timeout; |
318 | ++dh->nreloads; |
319 | } |
320 | else |
321 | { |
322 | if (h_addr_list_cnt == 1) |
323 | { |
324 | /* We have to create a new record. Just allocate |
325 | appropriate memory and copy it. */ |
326 | struct dataset *newp |
327 | = (struct dataset *) mempool_alloc (db, |
328 | total + req->key_len, |
329 | 1); |
330 | if (newp != NULL) |
331 | { |
332 | /* Adjust pointers into the memory block. */ |
333 | addresses = (char *) newp + (addresses |
334 | - (char *) dataset); |
335 | aliases = (char *) newp + (aliases - (char *) dataset); |
336 | assert (key_copy != NULL); |
337 | key_copy = (char *) newp + (key_copy - (char *) dataset); |
338 | |
339 | dataset = memcpy (newp, dataset, total + req->key_len); |
340 | alloca_used = false; |
341 | } |
342 | } |
343 | |
344 | /* Mark the old record as obsolete. */ |
345 | dh->usable = false; |
346 | } |
347 | } |
348 | else |
349 | { |
350 | /* We write the dataset before inserting it to the database |
351 | since while inserting this thread might block and so would |
352 | unnecessarily keep the receiver waiting. */ |
353 | assert (fd != -1); |
354 | |
355 | #ifdef HAVE_SENDFILE |
356 | if (__builtin_expect (db->mmap_used, 1) && !alloca_used) |
357 | { |
358 | assert (db->wr_fd != -1); |
359 | assert ((char *) &dataset->resp > (char *) db->data); |
360 | assert ((char *) dataset - (char *) db->head |
361 | + total |
362 | <= (sizeof (struct database_pers_head) |
363 | + db->head->module * sizeof (ref_t) |
364 | + db->head->data_size)); |
365 | ssize_t written = sendfileall (fd, db->wr_fd, |
366 | (char *) &dataset->resp |
367 | - (char *) db->head, |
368 | dataset->head.recsize); |
369 | if (written != dataset->head.recsize) |
370 | { |
371 | # ifndef __ASSUME_SENDFILE |
372 | if (written == -1 && errno == ENOSYS) |
373 | goto use_write; |
374 | # endif |
375 | all_written = false; |
376 | } |
377 | } |
378 | else |
379 | # ifndef __ASSUME_SENDFILE |
380 | use_write: |
381 | # endif |
382 | #endif |
383 | if (writeall (fd, &dataset->resp, dataset->head.recsize) |
384 | != dataset->head.recsize) |
385 | all_written = false; |
386 | } |
387 | |
388 | /* Add the record to the database. But only if it has not been |
389 | stored on the stack. |
390 | |
391 | If the record contains more than one IP address (used for |
392 | load balancing etc) don't cache the entry. This is something |
393 | the current cache handling cannot handle and it is more than |
394 | questionable whether it is worthwhile complicating the cache |
395 | handling just for handling such a special case. */ |
396 | if (! alloca_used) |
397 | { |
398 | /* If necessary, we also propagate the data to disk. */ |
399 | if (db->persistent) |
400 | { |
401 | // XXX async OK? |
402 | uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1; |
403 | msync ((void *) pval, |
404 | ((uintptr_t) dataset & pagesize_m1) |
405 | + total + req->key_len, MS_ASYNC); |
406 | } |
407 | |
408 | /* NB: the following code is really complicated. It has |
409 | seemlingly duplicated code paths which do the same. The |
410 | problem is that we always must add the hash table entry |
411 | with the FIRST flag set first. Otherwise we get dangling |
412 | pointers in case memory allocation fails. */ |
413 | assert (hst->h_addr_list[1] == NULL); |
414 | |
415 | /* Avoid adding names if more than one address is available. See |
416 | above for more info. */ |
417 | assert (req->type == GETHOSTBYNAME |
418 | || req->type == GETHOSTBYNAMEv6 |
419 | || req->type == GETHOSTBYADDR |
420 | || req->type == GETHOSTBYADDRv6); |
421 | |
422 | (void) cache_add (req->type, key_copy, req->key_len, |
423 | &dataset->head, true, db, owner, he == NULL); |
424 | |
425 | pthread_rwlock_unlock (&db->lock); |
426 | } |
427 | } |
428 | |
429 | if (__builtin_expect (!all_written, 0) && debug_level > 0) |
430 | { |
431 | char buf[256]; |
432 | dbg_log (_("short write in %s: %s" ), __FUNCTION__, |
433 | strerror_r (errno, buf, sizeof (buf))); |
434 | } |
435 | |
436 | return timeout; |
437 | } |
438 | |
439 | |
440 | static int |
441 | lookup (int type, void *key, struct hostent *resultbufp, char *buffer, |
442 | size_t buflen, struct hostent **hst, int32_t *ttlp) |
443 | { |
444 | if (type == GETHOSTBYNAME) |
445 | return __gethostbyname3_r (key, AF_INET, resultbufp, buffer, buflen, hst, |
446 | &h_errno, ttlp, NULL); |
447 | if (type == GETHOSTBYNAMEv6) |
448 | return __gethostbyname3_r (key, AF_INET6, resultbufp, buffer, buflen, hst, |
449 | &h_errno, ttlp, NULL); |
450 | if (type == GETHOSTBYADDR) |
451 | return __gethostbyaddr2_r (key, NS_INADDRSZ, AF_INET, resultbufp, buffer, |
452 | buflen, hst, &h_errno, ttlp); |
453 | return __gethostbyaddr2_r (key, NS_IN6ADDRSZ, AF_INET6, resultbufp, buffer, |
454 | buflen, hst, &h_errno, ttlp); |
455 | } |
456 | |
457 | |
458 | static time_t |
459 | addhstbyX (struct database_dyn *db, int fd, request_header *req, |
460 | void *key, uid_t uid, struct hashentry *he, struct datahead *dh) |
461 | { |
462 | /* Search for the entry matching the key. Please note that we don't |
463 | look again in the table whether the dataset is now available. We |
464 | simply insert it. It does not matter if it is in there twice. The |
465 | pruning function only will look at the timestamp. */ |
466 | int buflen = 1024; |
467 | char *buffer = (char *) alloca (buflen); |
468 | struct hostent resultbuf; |
469 | struct hostent *hst; |
470 | bool use_malloc = false; |
471 | int errval = 0; |
472 | int32_t ttl = INT32_MAX; |
473 | |
474 | if (__glibc_unlikely (debug_level > 0)) |
475 | { |
476 | const char *str; |
477 | char buf[INET6_ADDRSTRLEN + 1]; |
478 | if (req->type == GETHOSTBYNAME || req->type == GETHOSTBYNAMEv6) |
479 | str = key; |
480 | else |
481 | str = inet_ntop (req->type == GETHOSTBYADDR ? AF_INET : AF_INET6, |
482 | key, buf, sizeof (buf)); |
483 | |
484 | if (he == NULL) |
485 | dbg_log (_("Haven't found \"%s\" in hosts cache!" ), (char *) str); |
486 | else |
487 | dbg_log (_("Reloading \"%s\" in hosts cache!" ), (char *) str); |
488 | } |
489 | |
490 | while (lookup (req->type, key, &resultbuf, buffer, buflen, &hst, &ttl) != 0 |
491 | && h_errno == NETDB_INTERNAL |
492 | && (errval = errno) == ERANGE) |
493 | { |
494 | errno = 0; |
495 | |
496 | if (__glibc_unlikely (buflen > 32768)) |
497 | { |
498 | char *old_buffer = buffer; |
499 | buflen *= 2; |
500 | buffer = (char *) realloc (use_malloc ? buffer : NULL, buflen); |
501 | if (buffer == NULL) |
502 | { |
503 | /* We ran out of memory. We cannot do anything but |
504 | sending a negative response. In reality this should |
505 | never happen. */ |
506 | hst = NULL; |
507 | buffer = old_buffer; |
508 | |
509 | /* We set the error to indicate this is (possibly) a |
510 | temporary error and that it does not mean the entry |
511 | is not available at all. */ |
512 | h_errno = TRY_AGAIN; |
513 | errval = EAGAIN; |
514 | break; |
515 | } |
516 | use_malloc = true; |
517 | } |
518 | else |
519 | /* Allocate a new buffer on the stack. If possible combine it |
520 | with the previously allocated buffer. */ |
521 | buffer = (char *) extend_alloca (buffer, buflen, 2 * buflen); |
522 | } |
523 | |
524 | time_t timeout = cache_addhst (db, fd, req, key, hst, uid, he, dh, |
525 | h_errno == TRY_AGAIN ? errval : 0, ttl); |
526 | |
527 | if (use_malloc) |
528 | free (buffer); |
529 | |
530 | return timeout; |
531 | } |
532 | |
533 | |
534 | void |
535 | addhstbyname (struct database_dyn *db, int fd, request_header *req, |
536 | void *key, uid_t uid) |
537 | { |
538 | addhstbyX (db, fd, req, key, uid, NULL, NULL); |
539 | } |
540 | |
541 | |
542 | time_t |
543 | readdhstbyname (struct database_dyn *db, struct hashentry *he, |
544 | struct datahead *dh) |
545 | { |
546 | request_header req = |
547 | { |
548 | .type = GETHOSTBYNAME, |
549 | .key_len = he->len |
550 | }; |
551 | |
552 | return addhstbyX (db, -1, &req, db->data + he->key, he->owner, he, dh); |
553 | } |
554 | |
555 | |
556 | void |
557 | addhstbyaddr (struct database_dyn *db, int fd, request_header *req, |
558 | void *key, uid_t uid) |
559 | { |
560 | addhstbyX (db, fd, req, key, uid, NULL, NULL); |
561 | } |
562 | |
563 | |
564 | time_t |
565 | readdhstbyaddr (struct database_dyn *db, struct hashentry *he, |
566 | struct datahead *dh) |
567 | { |
568 | request_header req = |
569 | { |
570 | .type = GETHOSTBYADDR, |
571 | .key_len = he->len |
572 | }; |
573 | |
574 | return addhstbyX (db, -1, &req, db->data + he->key, he->owner, he, dh); |
575 | } |
576 | |
577 | |
578 | void |
579 | addhstbynamev6 (struct database_dyn *db, int fd, request_header *req, |
580 | void *key, uid_t uid) |
581 | { |
582 | addhstbyX (db, fd, req, key, uid, NULL, NULL); |
583 | } |
584 | |
585 | |
586 | time_t |
587 | readdhstbynamev6 (struct database_dyn *db, struct hashentry *he, |
588 | struct datahead *dh) |
589 | { |
590 | request_header req = |
591 | { |
592 | .type = GETHOSTBYNAMEv6, |
593 | .key_len = he->len |
594 | }; |
595 | |
596 | return addhstbyX (db, -1, &req, db->data + he->key, he->owner, he, dh); |
597 | } |
598 | |
599 | |
600 | void |
601 | addhstbyaddrv6 (struct database_dyn *db, int fd, request_header *req, |
602 | void *key, uid_t uid) |
603 | { |
604 | addhstbyX (db, fd, req, key, uid, NULL, NULL); |
605 | } |
606 | |
607 | |
608 | time_t |
609 | readdhstbyaddrv6 (struct database_dyn *db, struct hashentry *he, |
610 | struct datahead *dh) |
611 | { |
612 | request_header req = |
613 | { |
614 | .type = GETHOSTBYADDRv6, |
615 | .key_len = he->len |
616 | }; |
617 | |
618 | return addhstbyX (db, -1, &req, db->data + he->key, he->owner, he, dh); |
619 | } |
620 | |