1 | /* Cache handling for host lookup. |
2 | Copyright (C) 2004-2016 Free Software Foundation, Inc. |
3 | This file is part of the GNU C Library. |
4 | Contributed by Ulrich Drepper <drepper@redhat.com>, 2004. |
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 <assert.h> |
20 | #include <errno.h> |
21 | #include <libintl.h> |
22 | #include <netdb.h> |
23 | #include <nss.h> |
24 | #include <string.h> |
25 | #include <time.h> |
26 | #include <unistd.h> |
27 | #include <sys/mman.h> |
28 | #include <resolv/res_hconf.h> |
29 | |
30 | #include "dbg_log.h" |
31 | #include "nscd.h" |
32 | #ifdef HAVE_SENDFILE |
33 | # include <kernel-features.h> |
34 | #endif |
35 | |
36 | |
37 | typedef enum nss_status (*nss_gethostbyname4_r) |
38 | (const char *name, struct gaih_addrtuple **pat, |
39 | char *buffer, size_t buflen, int *errnop, |
40 | int *h_errnop, int32_t *ttlp); |
41 | typedef enum nss_status (*nss_gethostbyname3_r) |
42 | (const char *name, int af, struct hostent *host, |
43 | char *buffer, size_t buflen, int *errnop, |
44 | int *h_errnop, int32_t *, char **); |
45 | typedef enum nss_status (*nss_getcanonname_r) |
46 | (const char *name, char *buffer, size_t buflen, char **result, |
47 | int *errnop, int *h_errnop); |
48 | |
49 | |
50 | static const ai_response_header notfound = |
51 | { |
52 | .version = NSCD_VERSION, |
53 | .found = 0, |
54 | .naddrs = 0, |
55 | .addrslen = 0, |
56 | .canonlen = 0, |
57 | .error = 0 |
58 | }; |
59 | |
60 | |
61 | static time_t |
62 | addhstaiX (struct database_dyn *db, int fd, request_header *req, |
63 | void *key, uid_t uid, struct hashentry *const he, |
64 | struct datahead *dh) |
65 | { |
66 | /* Search for the entry matching the key. Please note that we don't |
67 | look again in the table whether the dataset is now available. We |
68 | simply insert it. It does not matter if it is in there twice. The |
69 | pruning function only will look at the timestamp. */ |
70 | |
71 | /* We allocate all data in one memory block: the iov vector, |
72 | the response header and the dataset itself. */ |
73 | struct dataset |
74 | { |
75 | struct datahead head; |
76 | ai_response_header resp; |
77 | char strdata[0]; |
78 | } *dataset = NULL; |
79 | |
80 | if (__glibc_unlikely (debug_level > 0)) |
81 | { |
82 | if (he == NULL) |
83 | dbg_log (_("Haven't found \"%s\" in hosts cache!" ), (char *) key); |
84 | else |
85 | dbg_log (_("Reloading \"%s\" in hosts cache!" ), (char *) key); |
86 | } |
87 | |
88 | static service_user *hosts_database; |
89 | service_user *nip; |
90 | int no_more; |
91 | int rc6 = 0; |
92 | int rc4 = 0; |
93 | int herrno = 0; |
94 | |
95 | if (hosts_database == NULL) |
96 | no_more = __nss_database_lookup ("hosts" , NULL, |
97 | "dns [!UNAVAIL=return] files" , |
98 | &hosts_database); |
99 | else |
100 | no_more = 0; |
101 | nip = hosts_database; |
102 | |
103 | /* Initialize configurations. */ |
104 | if (__glibc_unlikely (!_res_hconf.initialized)) |
105 | _res_hconf_init (); |
106 | if (__res_maybe_init (&_res, 0) == -1) |
107 | no_more = 1; |
108 | |
109 | /* If we are looking for both IPv4 and IPv6 address we don't want |
110 | the lookup functions to automatically promote IPv4 addresses to |
111 | IPv6 addresses. Currently this is decided by setting the |
112 | RES_USE_INET6 bit in _res.options. */ |
113 | int old_res_options = _res.options; |
114 | _res.options &= ~RES_USE_INET6; |
115 | |
116 | size_t tmpbuf6len = 1024; |
117 | char *tmpbuf6 = alloca (tmpbuf6len); |
118 | size_t tmpbuf4len = 0; |
119 | char *tmpbuf4 = NULL; |
120 | int32_t ttl = INT32_MAX; |
121 | ssize_t total = 0; |
122 | char *key_copy = NULL; |
123 | bool alloca_used = false; |
124 | time_t timeout = MAX_TIMEOUT_VALUE; |
125 | |
126 | while (!no_more) |
127 | { |
128 | void *cp; |
129 | int status[2] = { NSS_STATUS_UNAVAIL, NSS_STATUS_UNAVAIL }; |
130 | int naddrs = 0; |
131 | size_t addrslen = 0; |
132 | char *canon = NULL; |
133 | size_t canonlen; |
134 | |
135 | nss_gethostbyname4_r fct4 = __nss_lookup_function (nip, |
136 | "gethostbyname4_r" ); |
137 | if (fct4 != NULL) |
138 | { |
139 | struct gaih_addrtuple atmem; |
140 | struct gaih_addrtuple *at; |
141 | while (1) |
142 | { |
143 | at = &atmem; |
144 | rc6 = 0; |
145 | herrno = 0; |
146 | status[1] = DL_CALL_FCT (fct4, (key, &at, tmpbuf6, tmpbuf6len, |
147 | &rc6, &herrno, &ttl)); |
148 | if (rc6 != ERANGE || (herrno != NETDB_INTERNAL |
149 | && herrno != TRY_AGAIN)) |
150 | break; |
151 | tmpbuf6 = extend_alloca (tmpbuf6, tmpbuf6len, 2 * tmpbuf6len); |
152 | } |
153 | |
154 | if (rc6 != 0 && herrno == NETDB_INTERNAL) |
155 | goto out; |
156 | |
157 | if (status[1] != NSS_STATUS_SUCCESS) |
158 | goto next_nip; |
159 | |
160 | /* We found the data. Count the addresses and the size. */ |
161 | for (const struct gaih_addrtuple *at2 = at = &atmem; at2 != NULL; |
162 | at2 = at2->next) |
163 | { |
164 | ++naddrs; |
165 | /* We do not handle anything other than IPv4 and IPv6 |
166 | addresses. The getaddrinfo implementation does not |
167 | either so it is not worth trying to do more. */ |
168 | if (at2->family == AF_INET) |
169 | addrslen += INADDRSZ; |
170 | else if (at2->family == AF_INET6) |
171 | addrslen += IN6ADDRSZ; |
172 | } |
173 | canon = at->name; |
174 | canonlen = strlen (canon) + 1; |
175 | |
176 | total = sizeof (*dataset) + naddrs + addrslen + canonlen; |
177 | |
178 | /* Now we can allocate the data structure. If the TTL of the |
179 | entry is reported as zero do not cache the entry at all. */ |
180 | if (ttl != 0 && he == NULL) |
181 | dataset = (struct dataset *) mempool_alloc (db, total |
182 | + req->key_len, 1); |
183 | |
184 | if (dataset == NULL) |
185 | { |
186 | /* We cannot permanently add the result in the moment. But |
187 | we can provide the result as is. Store the data in some |
188 | temporary memory. */ |
189 | dataset = (struct dataset *) alloca (total + req->key_len); |
190 | |
191 | /* We cannot add this record to the permanent database. */ |
192 | alloca_used = true; |
193 | } |
194 | |
195 | /* Fill in the address and address families. */ |
196 | char *addrs = dataset->strdata; |
197 | uint8_t *family = (uint8_t *) (addrs + addrslen); |
198 | |
199 | for (const struct gaih_addrtuple *at2 = at; at2 != NULL; |
200 | at2 = at2->next) |
201 | { |
202 | *family++ = at2->family; |
203 | if (at2->family == AF_INET) |
204 | addrs = mempcpy (addrs, at2->addr, INADDRSZ); |
205 | else if (at2->family == AF_INET6) |
206 | addrs = mempcpy (addrs, at2->addr, IN6ADDRSZ); |
207 | } |
208 | |
209 | cp = family; |
210 | } |
211 | else |
212 | { |
213 | /* Prefer the function which also returns the TTL and |
214 | canonical name. */ |
215 | nss_gethostbyname3_r fct = __nss_lookup_function (nip, |
216 | "gethostbyname3_r" ); |
217 | if (fct == NULL) |
218 | fct = __nss_lookup_function (nip, "gethostbyname2_r" ); |
219 | |
220 | if (fct == NULL) |
221 | goto next_nip; |
222 | |
223 | struct hostent th[2]; |
224 | |
225 | /* Collect IPv6 information first. */ |
226 | while (1) |
227 | { |
228 | rc6 = 0; |
229 | status[0] = DL_CALL_FCT (fct, (key, AF_INET6, &th[0], tmpbuf6, |
230 | tmpbuf6len, &rc6, &herrno, &ttl, |
231 | &canon)); |
232 | if (rc6 != ERANGE || herrno != NETDB_INTERNAL) |
233 | break; |
234 | tmpbuf6 = extend_alloca (tmpbuf6, tmpbuf6len, 2 * tmpbuf6len); |
235 | } |
236 | |
237 | if (rc6 != 0 && herrno == NETDB_INTERNAL) |
238 | goto out; |
239 | |
240 | /* If the IPv6 lookup has been successful do not use the |
241 | buffer used in that lookup, use a new one. */ |
242 | if (status[0] == NSS_STATUS_SUCCESS && rc6 == 0) |
243 | { |
244 | tmpbuf4len = 512; |
245 | tmpbuf4 = alloca (tmpbuf4len); |
246 | } |
247 | else |
248 | { |
249 | tmpbuf4len = tmpbuf6len; |
250 | tmpbuf4 = tmpbuf6; |
251 | } |
252 | |
253 | /* Next collect IPv4 information. */ |
254 | while (1) |
255 | { |
256 | rc4 = 0; |
257 | status[1] = DL_CALL_FCT (fct, (key, AF_INET, &th[1], tmpbuf4, |
258 | tmpbuf4len, &rc4, &herrno, |
259 | ttl == INT32_MAX ? &ttl : NULL, |
260 | canon == NULL ? &canon : NULL)); |
261 | if (rc4 != ERANGE || herrno != NETDB_INTERNAL) |
262 | break; |
263 | tmpbuf4 = extend_alloca (tmpbuf4, tmpbuf4len, 2 * tmpbuf4len); |
264 | } |
265 | |
266 | if (rc4 != 0 && herrno == NETDB_INTERNAL) |
267 | goto out; |
268 | |
269 | if (status[0] != NSS_STATUS_SUCCESS |
270 | && status[1] != NSS_STATUS_SUCCESS) |
271 | goto next_nip; |
272 | |
273 | /* We found the data. Count the addresses and the size. */ |
274 | for (int j = 0; j < 2; ++j) |
275 | if (status[j] == NSS_STATUS_SUCCESS) |
276 | for (int i = 0; th[j].h_addr_list[i] != NULL; ++i) |
277 | { |
278 | ++naddrs; |
279 | addrslen += th[j].h_length; |
280 | } |
281 | |
282 | if (canon == NULL) |
283 | { |
284 | /* Determine the canonical name. */ |
285 | nss_getcanonname_r cfct; |
286 | cfct = __nss_lookup_function (nip, "getcanonname_r" ); |
287 | if (cfct != NULL) |
288 | { |
289 | const size_t max_fqdn_len = 256; |
290 | char *buf = alloca (max_fqdn_len); |
291 | char *s; |
292 | int rc; |
293 | |
294 | if (DL_CALL_FCT (cfct, (key, buf, max_fqdn_len, &s, |
295 | &rc, &herrno)) |
296 | == NSS_STATUS_SUCCESS) |
297 | canon = s; |
298 | else |
299 | /* Set to name now to avoid using gethostbyaddr. */ |
300 | canon = key; |
301 | } |
302 | else |
303 | { |
304 | struct hostent *hstent = NULL; |
305 | int herrno; |
306 | struct hostent hstent_mem; |
307 | void *addr; |
308 | size_t addrlen; |
309 | int addrfamily; |
310 | |
311 | if (status[1] == NSS_STATUS_SUCCESS) |
312 | { |
313 | addr = th[1].h_addr_list[0]; |
314 | addrlen = sizeof (struct in_addr); |
315 | addrfamily = AF_INET; |
316 | } |
317 | else |
318 | { |
319 | addr = th[0].h_addr_list[0]; |
320 | addrlen = sizeof (struct in6_addr); |
321 | addrfamily = AF_INET6; |
322 | } |
323 | |
324 | size_t tmpbuflen = 512; |
325 | char *tmpbuf = alloca (tmpbuflen); |
326 | int rc; |
327 | while (1) |
328 | { |
329 | rc = __gethostbyaddr2_r (addr, addrlen, addrfamily, |
330 | &hstent_mem, tmpbuf, tmpbuflen, |
331 | &hstent, &herrno, NULL); |
332 | if (rc != ERANGE || herrno != NETDB_INTERNAL) |
333 | break; |
334 | tmpbuf = extend_alloca (tmpbuf, tmpbuflen, |
335 | tmpbuflen * 2); |
336 | } |
337 | |
338 | if (rc == 0) |
339 | { |
340 | if (hstent != NULL) |
341 | canon = hstent->h_name; |
342 | else |
343 | canon = key; |
344 | } |
345 | } |
346 | } |
347 | |
348 | canonlen = canon == NULL ? 0 : (strlen (canon) + 1); |
349 | |
350 | total = sizeof (*dataset) + naddrs + addrslen + canonlen; |
351 | |
352 | |
353 | /* Now we can allocate the data structure. If the TTL of the |
354 | entry is reported as zero do not cache the entry at all. */ |
355 | if (ttl != 0 && he == NULL) |
356 | dataset = (struct dataset *) mempool_alloc (db, total |
357 | + req->key_len, 1); |
358 | |
359 | if (dataset == NULL) |
360 | { |
361 | /* We cannot permanently add the result in the moment. But |
362 | we can provide the result as is. Store the data in some |
363 | temporary memory. */ |
364 | dataset = (struct dataset *) alloca (total + req->key_len); |
365 | |
366 | /* We cannot add this record to the permanent database. */ |
367 | alloca_used = true; |
368 | } |
369 | |
370 | /* Fill in the address and address families. */ |
371 | char *addrs = dataset->strdata; |
372 | uint8_t *family = (uint8_t *) (addrs + addrslen); |
373 | |
374 | for (int j = 0; j < 2; ++j) |
375 | if (status[j] == NSS_STATUS_SUCCESS) |
376 | for (int i = 0; th[j].h_addr_list[i] != NULL; ++i) |
377 | { |
378 | addrs = mempcpy (addrs, th[j].h_addr_list[i], |
379 | th[j].h_length); |
380 | *family++ = th[j].h_addrtype; |
381 | } |
382 | |
383 | cp = family; |
384 | } |
385 | |
386 | timeout = datahead_init_pos (&dataset->head, total + req->key_len, |
387 | total - offsetof (struct dataset, resp), |
388 | he == NULL ? 0 : dh->nreloads + 1, |
389 | ttl == INT32_MAX ? db->postimeout : ttl); |
390 | |
391 | /* Fill in the rest of the dataset. */ |
392 | dataset->resp.version = NSCD_VERSION; |
393 | dataset->resp.found = 1; |
394 | dataset->resp.naddrs = naddrs; |
395 | dataset->resp.addrslen = addrslen; |
396 | dataset->resp.canonlen = canonlen; |
397 | dataset->resp.error = NETDB_SUCCESS; |
398 | |
399 | if (canon != NULL) |
400 | cp = mempcpy (cp, canon, canonlen); |
401 | |
402 | key_copy = memcpy (cp, key, req->key_len); |
403 | |
404 | assert (cp == (char *) dataset + total); |
405 | |
406 | /* Now we can determine whether on refill we have to create a |
407 | new record or not. */ |
408 | if (he != NULL) |
409 | { |
410 | assert (fd == -1); |
411 | |
412 | if (total + req->key_len == dh->allocsize |
413 | && total - offsetof (struct dataset, resp) == dh->recsize |
414 | && memcmp (&dataset->resp, dh->data, |
415 | dh->allocsize - offsetof (struct dataset, |
416 | resp)) == 0) |
417 | { |
418 | /* The data has not changed. We will just bump the |
419 | timeout value. Note that the new record has been |
420 | allocated on the stack and need not be freed. */ |
421 | dh->timeout = dataset->head.timeout; |
422 | dh->ttl = dataset->head.ttl; |
423 | ++dh->nreloads; |
424 | } |
425 | else |
426 | { |
427 | /* We have to create a new record. Just allocate |
428 | appropriate memory and copy it. */ |
429 | struct dataset *newp |
430 | = (struct dataset *) mempool_alloc (db, total + req->key_len, |
431 | 1); |
432 | if (__glibc_likely (newp != NULL)) |
433 | { |
434 | /* Adjust pointer into the memory block. */ |
435 | key_copy = (char *) newp + (key_copy - (char *) dataset); |
436 | |
437 | dataset = memcpy (newp, dataset, total + req->key_len); |
438 | alloca_used = false; |
439 | } |
440 | |
441 | /* Mark the old record as obsolete. */ |
442 | dh->usable = false; |
443 | } |
444 | } |
445 | else |
446 | { |
447 | /* We write the dataset before inserting it to the database |
448 | since while inserting this thread might block and so |
449 | would unnecessarily let the receiver wait. */ |
450 | assert (fd != -1); |
451 | |
452 | #ifdef HAVE_SENDFILE |
453 | if (__builtin_expect (db->mmap_used, 1) && !alloca_used) |
454 | { |
455 | assert (db->wr_fd != -1); |
456 | assert ((char *) &dataset->resp > (char *) db->data); |
457 | assert ((char *) dataset - (char *) db->head + total |
458 | <= (sizeof (struct database_pers_head) |
459 | + db->head->module * sizeof (ref_t) |
460 | + db->head->data_size)); |
461 | # ifndef __ASSUME_SENDFILE |
462 | ssize_t written; |
463 | written = |
464 | # endif |
465 | sendfileall (fd, db->wr_fd, (char *) &dataset->resp |
466 | - (char *) db->head, dataset->head.recsize); |
467 | # ifndef __ASSUME_SENDFILE |
468 | if (written == -1 && errno == ENOSYS) |
469 | goto use_write; |
470 | # endif |
471 | } |
472 | else |
473 | # ifndef __ASSUME_SENDFILE |
474 | use_write: |
475 | # endif |
476 | #endif |
477 | writeall (fd, &dataset->resp, dataset->head.recsize); |
478 | } |
479 | |
480 | goto out; |
481 | |
482 | next_nip: |
483 | if (nss_next_action (nip, status[1]) == NSS_ACTION_RETURN) |
484 | break; |
485 | |
486 | if (nip->next == NULL) |
487 | no_more = -1; |
488 | else |
489 | nip = nip->next; |
490 | } |
491 | |
492 | /* No result found. Create a negative result record. */ |
493 | if (he != NULL && rc4 == EAGAIN) |
494 | { |
495 | /* If we have an old record available but cannot find one now |
496 | because the service is not available we keep the old record |
497 | and make sure it does not get removed. */ |
498 | if (reload_count != UINT_MAX && dh->nreloads == reload_count) |
499 | /* Do not reset the value if we never not reload the record. */ |
500 | dh->nreloads = reload_count - 1; |
501 | |
502 | /* Reload with the same time-to-live value. */ |
503 | timeout = dh->timeout = time (NULL) + dh->ttl; |
504 | } |
505 | else |
506 | { |
507 | /* We have no data. This means we send the standard reply for |
508 | this case. */ |
509 | total = sizeof (notfound); |
510 | |
511 | if (fd != -1) |
512 | TEMP_FAILURE_RETRY (send (fd, ¬found, total, MSG_NOSIGNAL)); |
513 | |
514 | /* If we have a transient error or cannot permanently store the |
515 | result, so be it. */ |
516 | if (rc4 == EAGAIN || __builtin_expect (db->negtimeout == 0, 0)) |
517 | { |
518 | /* Mark the old entry as obsolete. */ |
519 | if (dh != NULL) |
520 | dh->usable = false; |
521 | dataset = NULL; |
522 | } |
523 | else if ((dataset = mempool_alloc (db, (sizeof (struct dataset) |
524 | + req->key_len), 1)) != NULL) |
525 | { |
526 | timeout = datahead_init_neg (&dataset->head, |
527 | sizeof (struct dataset) + req->key_len, |
528 | total, db->negtimeout); |
529 | |
530 | /* This is the reply. */ |
531 | memcpy (&dataset->resp, ¬found, total); |
532 | |
533 | /* Copy the key data. */ |
534 | key_copy = memcpy (dataset->strdata, key, req->key_len); |
535 | } |
536 | } |
537 | |
538 | out: |
539 | _res.options |= old_res_options & RES_USE_INET6; |
540 | |
541 | if (dataset != NULL && !alloca_used) |
542 | { |
543 | /* If necessary, we also propagate the data to disk. */ |
544 | if (db->persistent) |
545 | { |
546 | // XXX async OK? |
547 | uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1; |
548 | msync ((void *) pval, |
549 | ((uintptr_t) dataset & pagesize_m1) + total + req->key_len, |
550 | MS_ASYNC); |
551 | } |
552 | |
553 | (void) cache_add (req->type, key_copy, req->key_len, &dataset->head, |
554 | true, db, uid, he == NULL); |
555 | |
556 | pthread_rwlock_unlock (&db->lock); |
557 | |
558 | /* Mark the old entry as obsolete. */ |
559 | if (dh != NULL) |
560 | dh->usable = false; |
561 | } |
562 | |
563 | return timeout; |
564 | } |
565 | |
566 | |
567 | void |
568 | addhstai (struct database_dyn *db, int fd, request_header *req, void *key, |
569 | uid_t uid) |
570 | { |
571 | addhstaiX (db, fd, req, key, uid, NULL, NULL); |
572 | } |
573 | |
574 | |
575 | time_t |
576 | readdhstai (struct database_dyn *db, struct hashentry *he, struct datahead *dh) |
577 | { |
578 | request_header req = |
579 | { |
580 | .type = GETAI, |
581 | .key_len = he->len |
582 | }; |
583 | |
584 | return addhstaiX (db, -1, &req, db->data + he->key, he->owner, he, dh); |
585 | } |
586 | |