1 | /* Cache handling for host lookup. |
2 | Copyright (C) 2004-2024 Free Software Foundation, Inc. |
3 | This file is part of the GNU C Library. |
4 | |
5 | This program is free software; you can redistribute it and/or modify |
6 | it under the terms of the GNU General Public License as published |
7 | by the Free Software Foundation; version 2 of the License, or |
8 | (at your option) any later version. |
9 | |
10 | This program is distributed in the hope that it will be useful, |
11 | but WITHOUT ANY WARRANTY; without even the implied warranty of |
12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
13 | GNU General Public License for more details. |
14 | |
15 | You should have received a copy of the GNU General Public License |
16 | along with this program; if not, see <https://www.gnu.org/licenses/>. */ |
17 | |
18 | #include <assert.h> |
19 | #include <errno.h> |
20 | #include <libintl.h> |
21 | #include <netdb.h> |
22 | #include <nss.h> |
23 | #include <string.h> |
24 | #include <time.h> |
25 | #include <unistd.h> |
26 | #include <sys/mman.h> |
27 | #include <resolv/resolv-internal.h> |
28 | #include <resolv/resolv_context.h> |
29 | #include <scratch_buffer.h> |
30 | |
31 | #include "dbg_log.h" |
32 | #include "nscd.h" |
33 | |
34 | |
35 | static const ai_response_header notfound = |
36 | { |
37 | .version = NSCD_VERSION, |
38 | .found = 0, |
39 | .naddrs = 0, |
40 | .addrslen = 0, |
41 | .canonlen = 0, |
42 | .error = 0 |
43 | }; |
44 | |
45 | |
46 | static time_t |
47 | addhstaiX (struct database_dyn *db, int fd, request_header *req, |
48 | void *key, uid_t uid, struct hashentry *const he, |
49 | struct datahead *dh) |
50 | { |
51 | /* Search for the entry matching the key. Please note that we don't |
52 | look again in the table whether the dataset is now available. We |
53 | simply insert it. It does not matter if it is in there twice. The |
54 | pruning function only will look at the timestamp. */ |
55 | |
56 | /* We allocate all data in one memory block: the iov vector, |
57 | the response header and the dataset itself. */ |
58 | struct dataset |
59 | { |
60 | struct datahead head; |
61 | ai_response_header resp; |
62 | char strdata[0]; |
63 | } *dataset = NULL; |
64 | |
65 | if (__glibc_unlikely (debug_level > 0)) |
66 | { |
67 | if (he == NULL) |
68 | dbg_log (_("Haven't found \"%s\" in hosts cache!" ), (char *) key); |
69 | else |
70 | dbg_log (_("Reloading \"%s\" in hosts cache!" ), (char *) key); |
71 | } |
72 | |
73 | nss_action_list nip; |
74 | int no_more; |
75 | int rc6 = 0; |
76 | int rc4 = 0; |
77 | int herrno = 0; |
78 | |
79 | no_more = !__nss_database_get (db: nss_database_hosts, actions: &nip); |
80 | |
81 | /* Initialize configurations. */ |
82 | struct resolv_context *ctx = __resolv_context_get (); |
83 | if (ctx == NULL) |
84 | no_more = 1; |
85 | |
86 | struct scratch_buffer tmpbuf6; |
87 | scratch_buffer_init (buffer: &tmpbuf6); |
88 | struct scratch_buffer tmpbuf4; |
89 | scratch_buffer_init (buffer: &tmpbuf4); |
90 | struct scratch_buffer canonbuf; |
91 | scratch_buffer_init (buffer: &canonbuf); |
92 | |
93 | int32_t ttl = INT32_MAX; |
94 | ssize_t total = 0; |
95 | char *key_copy = NULL; |
96 | bool alloca_used = false; |
97 | time_t timeout = MAX_TIMEOUT_VALUE; |
98 | |
99 | while (!no_more) |
100 | { |
101 | void *cp; |
102 | int status[2] = { NSS_STATUS_UNAVAIL, NSS_STATUS_UNAVAIL }; |
103 | int naddrs = 0; |
104 | size_t addrslen = 0; |
105 | |
106 | char *canon = NULL; |
107 | size_t canonlen; |
108 | |
109 | nss_gethostbyname4_r *fct4 = __nss_lookup_function (ni: nip, |
110 | fct_name: "gethostbyname4_r" ); |
111 | if (fct4 != NULL) |
112 | { |
113 | struct gaih_addrtuple *at; |
114 | while (1) |
115 | { |
116 | at = NULL; |
117 | rc6 = 0; |
118 | herrno = 0; |
119 | status[1] = DL_CALL_FCT (fct4, (key, &at, |
120 | tmpbuf6.data, tmpbuf6.length, |
121 | &rc6, &herrno, &ttl)); |
122 | if (rc6 != ERANGE || (herrno != NETDB_INTERNAL |
123 | && herrno != TRY_AGAIN)) |
124 | break; |
125 | if (!scratch_buffer_grow (buffer: &tmpbuf6)) |
126 | { |
127 | rc6 = ENOMEM; |
128 | break; |
129 | } |
130 | } |
131 | |
132 | if (rc6 != 0 && herrno == NETDB_INTERNAL) |
133 | goto out; |
134 | |
135 | if (status[1] != NSS_STATUS_SUCCESS) |
136 | goto next_nip; |
137 | |
138 | /* We found the data. Count the addresses and the size. */ |
139 | for (const struct gaih_addrtuple *at2 = at; at2 != NULL; |
140 | at2 = at2->next) |
141 | { |
142 | ++naddrs; |
143 | /* We do not handle anything other than IPv4 and IPv6 |
144 | addresses. The getaddrinfo implementation does not |
145 | either so it is not worth trying to do more. */ |
146 | if (at2->family == AF_INET) |
147 | addrslen += INADDRSZ; |
148 | else if (at2->family == AF_INET6) |
149 | addrslen += IN6ADDRSZ; |
150 | } |
151 | canon = at->name; |
152 | canonlen = strlen (s: canon) + 1; |
153 | |
154 | total = sizeof (*dataset) + naddrs + addrslen + canonlen; |
155 | |
156 | /* Now we can allocate the data structure. If the TTL of the |
157 | entry is reported as zero do not cache the entry at all. */ |
158 | if (ttl != 0 && he == NULL) |
159 | dataset = (struct dataset *) mempool_alloc (db, len: total |
160 | + req->key_len, data_alloc: 1); |
161 | |
162 | if (dataset == NULL) |
163 | { |
164 | /* We cannot permanently add the result in the moment. But |
165 | we can provide the result as is. Store the data in some |
166 | temporary memory. */ |
167 | dataset = (struct dataset *) alloca (total + req->key_len); |
168 | |
169 | /* We cannot add this record to the permanent database. */ |
170 | alloca_used = true; |
171 | } |
172 | |
173 | /* Fill in the address and address families. */ |
174 | char *addrs = dataset->strdata; |
175 | uint8_t *family = (uint8_t *) (addrs + addrslen); |
176 | |
177 | for (const struct gaih_addrtuple *at2 = at; at2 != NULL; |
178 | at2 = at2->next) |
179 | { |
180 | *family++ = at2->family; |
181 | if (at2->family == AF_INET) |
182 | addrs = mempcpy (addrs, at2->addr, INADDRSZ); |
183 | else if (at2->family == AF_INET6) |
184 | addrs = mempcpy (addrs, at2->addr, IN6ADDRSZ); |
185 | } |
186 | |
187 | cp = family; |
188 | } |
189 | else |
190 | { |
191 | /* Prefer the function which also returns the TTL and |
192 | canonical name. */ |
193 | nss_gethostbyname3_r *fct |
194 | = __nss_lookup_function (ni: nip, fct_name: "gethostbyname3_r" ); |
195 | if (fct == NULL) |
196 | fct = __nss_lookup_function (ni: nip, fct_name: "gethostbyname2_r" ); |
197 | |
198 | if (fct == NULL) |
199 | goto next_nip; |
200 | |
201 | struct hostent th[2]; |
202 | |
203 | /* Collect IPv6 information first. */ |
204 | while (1) |
205 | { |
206 | rc6 = 0; |
207 | status[0] = DL_CALL_FCT (fct, (key, AF_INET6, &th[0], |
208 | tmpbuf6.data, tmpbuf6.length, |
209 | &rc6, &herrno, &ttl, |
210 | &canon)); |
211 | if (rc6 != ERANGE || herrno != NETDB_INTERNAL) |
212 | break; |
213 | if (!scratch_buffer_grow (buffer: &tmpbuf6)) |
214 | { |
215 | rc6 = ENOMEM; |
216 | break; |
217 | } |
218 | } |
219 | |
220 | if (rc6 != 0 && herrno == NETDB_INTERNAL) |
221 | goto out; |
222 | |
223 | /* Next collect IPv4 information. */ |
224 | while (1) |
225 | { |
226 | rc4 = 0; |
227 | status[1] = DL_CALL_FCT (fct, (key, AF_INET, &th[1], |
228 | tmpbuf4.data, tmpbuf4.length, |
229 | &rc4, &herrno, |
230 | ttl == INT32_MAX ? &ttl : NULL, |
231 | canon == NULL ? &canon : NULL)); |
232 | if (rc4 != ERANGE || herrno != NETDB_INTERNAL) |
233 | break; |
234 | if (!scratch_buffer_grow (buffer: &tmpbuf4)) |
235 | { |
236 | rc4 = ENOMEM; |
237 | break; |
238 | } |
239 | } |
240 | |
241 | if (rc4 != 0 && herrno == NETDB_INTERNAL) |
242 | goto out; |
243 | |
244 | if (status[0] != NSS_STATUS_SUCCESS |
245 | && status[1] != NSS_STATUS_SUCCESS) |
246 | goto next_nip; |
247 | |
248 | /* We found the data. Count the addresses and the size. */ |
249 | for (int j = 0; j < 2; ++j) |
250 | if (status[j] == NSS_STATUS_SUCCESS) |
251 | for (int i = 0; th[j].h_addr_list[i] != NULL; ++i) |
252 | { |
253 | ++naddrs; |
254 | addrslen += th[j].h_length; |
255 | } |
256 | |
257 | if (canon == NULL) |
258 | { |
259 | /* Determine the canonical name. */ |
260 | nss_getcanonname_r *cfct; |
261 | cfct = __nss_lookup_function (ni: nip, fct_name: "getcanonname_r" ); |
262 | if (cfct != NULL) |
263 | { |
264 | char *s; |
265 | int rc; |
266 | |
267 | if (DL_CALL_FCT (cfct, (key, canonbuf.data, canonbuf.length, |
268 | &s, &rc, &herrno)) |
269 | == NSS_STATUS_SUCCESS) |
270 | canon = s; |
271 | else |
272 | /* Set to name now to avoid using gethostbyaddr. */ |
273 | canon = key; |
274 | } |
275 | else |
276 | { |
277 | struct hostent *hstent = NULL; |
278 | int herrno; |
279 | struct hostent hstent_mem; |
280 | void *addr; |
281 | size_t addrlen; |
282 | int addrfamily; |
283 | |
284 | if (status[1] == NSS_STATUS_SUCCESS) |
285 | { |
286 | addr = th[1].h_addr_list[0]; |
287 | addrlen = sizeof (struct in_addr); |
288 | addrfamily = AF_INET; |
289 | } |
290 | else |
291 | { |
292 | addr = th[0].h_addr_list[0]; |
293 | addrlen = sizeof (struct in6_addr); |
294 | addrfamily = AF_INET6; |
295 | } |
296 | |
297 | int rc; |
298 | while (1) |
299 | { |
300 | rc = __gethostbyaddr2_r (addr: addr, len: addrlen, type: addrfamily, |
301 | result_buf: &hstent_mem, |
302 | buf: canonbuf.data, buflen: canonbuf.length, |
303 | result: &hstent, h_errnop: &herrno, NULL); |
304 | if (rc != ERANGE || herrno != NETDB_INTERNAL) |
305 | break; |
306 | if (!scratch_buffer_grow (buffer: &canonbuf)) |
307 | { |
308 | rc = ENOMEM; |
309 | break; |
310 | } |
311 | } |
312 | |
313 | if (rc == 0) |
314 | { |
315 | if (hstent != NULL) |
316 | canon = hstent->h_name; |
317 | else |
318 | canon = key; |
319 | } |
320 | } |
321 | } |
322 | |
323 | canonlen = canon == NULL ? 0 : (strlen (s: canon) + 1); |
324 | |
325 | total = sizeof (*dataset) + naddrs + addrslen + canonlen; |
326 | |
327 | |
328 | /* Now we can allocate the data structure. If the TTL of the |
329 | entry is reported as zero do not cache the entry at all. */ |
330 | if (ttl != 0 && he == NULL) |
331 | dataset = (struct dataset *) mempool_alloc (db, len: total |
332 | + req->key_len, data_alloc: 1); |
333 | |
334 | if (dataset == NULL) |
335 | { |
336 | /* We cannot permanently add the result in the moment. But |
337 | we can provide the result as is. Store the data in some |
338 | temporary memory. */ |
339 | dataset = (struct dataset *) alloca (total + req->key_len); |
340 | |
341 | /* We cannot add this record to the permanent database. */ |
342 | alloca_used = true; |
343 | } |
344 | |
345 | /* Fill in the address and address families. */ |
346 | char *addrs = dataset->strdata; |
347 | uint8_t *family = (uint8_t *) (addrs + addrslen); |
348 | |
349 | for (int j = 0; j < 2; ++j) |
350 | if (status[j] == NSS_STATUS_SUCCESS) |
351 | for (int i = 0; th[j].h_addr_list[i] != NULL; ++i) |
352 | { |
353 | addrs = mempcpy (addrs, th[j].h_addr_list[i], |
354 | th[j].h_length); |
355 | *family++ = th[j].h_addrtype; |
356 | } |
357 | |
358 | cp = family; |
359 | } |
360 | |
361 | timeout = datahead_init_pos (head: &dataset->head, allocsize: total + req->key_len, |
362 | recsize: total - offsetof (struct dataset, resp), |
363 | nreloads: he == NULL ? 0 : dh->nreloads + 1, |
364 | ttl: ttl == INT32_MAX ? db->postimeout : ttl); |
365 | |
366 | /* Fill in the rest of the dataset. */ |
367 | dataset->resp.version = NSCD_VERSION; |
368 | dataset->resp.found = 1; |
369 | dataset->resp.naddrs = naddrs; |
370 | dataset->resp.addrslen = addrslen; |
371 | dataset->resp.canonlen = canonlen; |
372 | dataset->resp.error = NETDB_SUCCESS; |
373 | |
374 | if (canon != NULL) |
375 | cp = mempcpy (cp, canon, canonlen); |
376 | |
377 | key_copy = memcpy (dest: cp, src: key, n: req->key_len); |
378 | |
379 | assert (cp == (char *) dataset + total); |
380 | |
381 | /* Now we can determine whether on refill we have to create a |
382 | new record or not. */ |
383 | if (he != NULL) |
384 | { |
385 | assert (fd == -1); |
386 | |
387 | if (total + req->key_len == dh->allocsize |
388 | && total - offsetof (struct dataset, resp) == dh->recsize |
389 | && memcmp (s1: &dataset->resp, s2: dh->data, |
390 | n: dh->allocsize - offsetof (struct dataset, |
391 | resp)) == 0) |
392 | { |
393 | /* The data has not changed. We will just bump the |
394 | timeout value. Note that the new record has been |
395 | allocated on the stack and need not be freed. */ |
396 | dh->timeout = dataset->head.timeout; |
397 | dh->ttl = dataset->head.ttl; |
398 | ++dh->nreloads; |
399 | } |
400 | else |
401 | { |
402 | /* We have to create a new record. Just allocate |
403 | appropriate memory and copy it. */ |
404 | struct dataset *newp |
405 | = (struct dataset *) mempool_alloc (db, len: total + req->key_len, |
406 | data_alloc: 1); |
407 | if (__glibc_likely (newp != NULL)) |
408 | { |
409 | /* Adjust pointer into the memory block. */ |
410 | key_copy = (char *) newp + (key_copy - (char *) dataset); |
411 | |
412 | dataset = memcpy (dest: newp, src: dataset, n: total + req->key_len); |
413 | alloca_used = false; |
414 | } |
415 | |
416 | /* Mark the old record as obsolete. */ |
417 | dh->usable = false; |
418 | } |
419 | } |
420 | else |
421 | { |
422 | /* We write the dataset before inserting it to the database |
423 | since while inserting this thread might block and so |
424 | would unnecessarily let the receiver wait. */ |
425 | assert (fd != -1); |
426 | |
427 | writeall (fd, buf: &dataset->resp, len: dataset->head.recsize); |
428 | } |
429 | |
430 | goto out; |
431 | |
432 | next_nip: |
433 | if (nss_next_action (nip, status[1]) == NSS_ACTION_RETURN) |
434 | break; |
435 | |
436 | if (nip[1].module == NULL) |
437 | no_more = -1; |
438 | else |
439 | ++nip; |
440 | } |
441 | |
442 | /* No result found. Create a negative result record. */ |
443 | if (he != NULL && rc4 == EAGAIN) |
444 | { |
445 | /* If we have an old record available but cannot find one now |
446 | because the service is not available we keep the old record |
447 | and make sure it does not get removed. */ |
448 | if (reload_count != UINT_MAX && dh->nreloads == reload_count) |
449 | /* Do not reset the value if we never not reload the record. */ |
450 | dh->nreloads = reload_count - 1; |
451 | |
452 | /* Reload with the same time-to-live value. */ |
453 | timeout = dh->timeout = time (NULL) + dh->ttl; |
454 | } |
455 | else |
456 | { |
457 | /* We have no data. This means we send the standard reply for |
458 | this case. */ |
459 | total = sizeof (notfound); |
460 | |
461 | if (fd != -1) |
462 | TEMP_FAILURE_RETRY (send (fd, ¬found, total, MSG_NOSIGNAL)); |
463 | |
464 | /* If we have a transient error or cannot permanently store the |
465 | result, so be it. */ |
466 | if (rc4 == EAGAIN || __builtin_expect (db->negtimeout == 0, 0)) |
467 | { |
468 | /* Mark the old entry as obsolete. */ |
469 | if (dh != NULL) |
470 | dh->usable = false; |
471 | dataset = NULL; |
472 | } |
473 | else if ((dataset = mempool_alloc (db, len: (sizeof (struct dataset) |
474 | + req->key_len), data_alloc: 1)) != NULL) |
475 | { |
476 | timeout = datahead_init_neg (head: &dataset->head, |
477 | allocsize: sizeof (struct dataset) + req->key_len, |
478 | recsize: total, ttl: db->negtimeout); |
479 | |
480 | /* This is the reply. */ |
481 | memcpy (dest: &dataset->resp, src: ¬found, n: total); |
482 | |
483 | /* Copy the key data. */ |
484 | key_copy = memcpy (dest: dataset->strdata, src: key, n: req->key_len); |
485 | } |
486 | } |
487 | |
488 | out: |
489 | __resolv_context_put (ctx); |
490 | |
491 | if (dataset != NULL && !alloca_used) |
492 | { |
493 | /* If necessary, we also propagate the data to disk. */ |
494 | if (db->persistent) |
495 | { |
496 | // XXX async OK? |
497 | uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1; |
498 | msync (addr: (void *) pval, |
499 | len: ((uintptr_t) dataset & pagesize_m1) + total + req->key_len, |
500 | MS_ASYNC); |
501 | } |
502 | |
503 | (void) cache_add (type: req->type, key: key_copy, len: req->key_len, packet: &dataset->head, |
504 | true, table: db, owner: uid, prune_wakeup: he == NULL); |
505 | |
506 | pthread_rwlock_unlock (rwlock: &db->lock); |
507 | |
508 | /* Mark the old entry as obsolete. */ |
509 | if (dh != NULL) |
510 | dh->usable = false; |
511 | } |
512 | |
513 | scratch_buffer_free (buffer: &tmpbuf6); |
514 | scratch_buffer_free (buffer: &tmpbuf4); |
515 | scratch_buffer_free (buffer: &canonbuf); |
516 | |
517 | return timeout; |
518 | } |
519 | |
520 | |
521 | void |
522 | addhstai (struct database_dyn *db, int fd, request_header *req, void *key, |
523 | uid_t uid) |
524 | { |
525 | addhstaiX (db, fd, req, key, uid, NULL, NULL); |
526 | } |
527 | |
528 | |
529 | time_t |
530 | readdhstai (struct database_dyn *db, struct hashentry *he, struct datahead *dh) |
531 | { |
532 | request_header req = |
533 | { |
534 | .type = GETAI, |
535 | .key_len = he->len |
536 | }; |
537 | |
538 | return addhstaiX (db, fd: -1, req: &req, key: db->data + he->key, uid: he->owner, he, dh); |
539 | } |
540 | |