1 /* Cache handling for services lookup.
2 Copyright (C) 2007-2023 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 <unistd.h>
23 #include <stdint.h>
24 #include <sys/mman.h>
25 #include <kernel-features.h>
26 #include <scratch_buffer.h>
27
28 #include "nscd.h"
29 #include "dbg_log.h"
30
31
32 /* This is the standard reply in case the service is disabled. */
33 static const serv_response_header disabled =
34 {
35 .version = NSCD_VERSION,
36 .found = -1,
37 .s_name_len = 0,
38 .s_proto_len = 0,
39 .s_aliases_cnt = 0,
40 .s_port = -1
41 };
42
43 /* This is the struct describing how to write this record. */
44 const struct iovec serv_iov_disabled =
45 {
46 .iov_base = (void *) &disabled,
47 .iov_len = sizeof (disabled)
48 };
49
50
51 /* This is the standard reply in case we haven't found the dataset. */
52 static const serv_response_header notfound =
53 {
54 .version = NSCD_VERSION,
55 .found = 0,
56 .s_name_len = 0,
57 .s_proto_len = 0,
58 .s_aliases_cnt = 0,
59 .s_port = -1
60 };
61
62
63 static time_t
64 cache_addserv (struct database_dyn *db, int fd, request_header *req,
65 const void *key, struct servent *serv, uid_t owner,
66 struct hashentry *const he, struct datahead *dh, int errval)
67 {
68 bool all_written = true;
69 ssize_t total;
70 time_t t = time (NULL);
71
72 /* We allocate all data in one memory block: the iov vector,
73 the response header and the dataset itself. */
74 struct dataset
75 {
76 struct datahead head;
77 serv_response_header resp;
78 char strdata[0];
79 } *dataset;
80
81 assert (offsetof (struct dataset, resp) == offsetof (struct datahead, data));
82
83 time_t timeout = MAX_TIMEOUT_VALUE;
84 if (serv == NULL)
85 {
86 if (he != NULL && errval == EAGAIN)
87 {
88 /* If we have an old record available but cannot find one
89 now because the service is not available we keep the old
90 record and make sure it does not get removed. */
91 if (reload_count != UINT_MAX)
92 /* Do not reset the value if we never not reload the record. */
93 dh->nreloads = reload_count - 1;
94
95 /* Reload with the same time-to-live value. */
96 timeout = dh->timeout = t + db->postimeout;
97
98 total = 0;
99 }
100 else
101 {
102 /* We have no data. This means we send the standard reply for this
103 case. */
104 total = sizeof (notfound);
105
106 if (fd != -1
107 && TEMP_FAILURE_RETRY (send (fd, ¬found, total,
108 MSG_NOSIGNAL)) != total)
109 all_written = false;
110
111 /* If we have a transient error or cannot permanently store
112 the result, so be it. */
113 if (errval == EAGAIN || __builtin_expect (db->negtimeout == 0, 0))
114 {
115 /* Mark the old entry as obsolete. */
116 if (dh != NULL)
117 dh->usable = false;
118 }
119 else if ((dataset = mempool_alloc (db, (sizeof (struct dataset)
120 + req->key_len), 1)) != NULL)
121 {
122 timeout = datahead_init_neg (&dataset->head,
123 (sizeof (struct dataset)
124 + req->key_len), total,
125 db->negtimeout);
126
127 /* This is the reply. */
128 memcpy (&dataset->resp, ¬found, total);
129
130 /* Copy the key data. */
131 memcpy (dataset->strdata, key, req->key_len);
132
133 /* If necessary, we also propagate the data to disk. */
134 if (db->persistent)
135 {
136 // XXX async OK?
137 uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1;
138 msync ((void *) pval,
139 ((uintptr_t) dataset & pagesize_m1)
140 + sizeof (struct dataset) + req->key_len, MS_ASYNC);
141 }
142
143 (void) cache_add (req->type, &dataset->strdata, req->key_len,
144 &dataset->head, true, db, owner, he == NULL);
145
146 pthread_rwlock_unlock (&db->lock);
147
148 /* Mark the old entry as obsolete. */
149 if (dh != NULL)
150 dh->usable = false;
151 }
152 }
153 }
154 else
155 {
156 /* Determine the I/O structure. */
157 size_t s_name_len = strlen (serv->s_name) + 1;
158 size_t s_proto_len = strlen (serv->s_proto) + 1;
159 uint32_t *s_aliases_len;
160 size_t s_aliases_cnt;
161 char *aliases;
162 char *cp;
163 size_t cnt;
164
165 /* Determine the number of aliases. */
166 s_aliases_cnt = 0;
167 for (cnt = 0; serv->s_aliases[cnt] != NULL; ++cnt)
168 ++s_aliases_cnt;
169 /* Determine the length of all aliases. */
170 s_aliases_len = (uint32_t *) alloca (s_aliases_cnt * sizeof (uint32_t));
171 total = 0;
172 for (cnt = 0; cnt < s_aliases_cnt; ++cnt)
173 {
174 s_aliases_len[cnt] = strlen (serv->s_aliases[cnt]) + 1;
175 total += s_aliases_len[cnt];
176 }
177
178 total += (offsetof (struct dataset, strdata)
179 + s_name_len
180 + s_proto_len
181 + s_aliases_cnt * sizeof (uint32_t));
182
183 /* If we refill the cache, first assume the reconrd did not
184 change. Allocate memory on the cache since it is likely
185 discarded anyway. If it turns out to be necessary to have a
186 new record we can still allocate real memory. */
187 bool alloca_used = false;
188 dataset = NULL;
189
190 if (he == NULL)
191 dataset = (struct dataset *) mempool_alloc (db, total + req->key_len,
192 1);
193
194 if (dataset == NULL)
195 {
196 /* We cannot permanently add the result in the moment. But
197 we can provide the result as is. Store the data in some
198 temporary memory. */
199 dataset = (struct dataset *) alloca (total + req->key_len);
200
201 /* We cannot add this record to the permanent database. */
202 alloca_used = true;
203 }
204
205 timeout = datahead_init_pos (&dataset->head, total + req->key_len,
206 total - offsetof (struct dataset, resp),
207 he == NULL ? 0 : dh->nreloads + 1,
208 db->postimeout);
209
210 dataset->resp.version = NSCD_VERSION;
211 dataset->resp.found = 1;
212 dataset->resp.s_name_len = s_name_len;
213 dataset->resp.s_proto_len = s_proto_len;
214 dataset->resp.s_port = serv->s_port;
215 dataset->resp.s_aliases_cnt = s_aliases_cnt;
216
217 cp = dataset->strdata;
218
219 cp = mempcpy (cp, serv->s_name, s_name_len);
220 cp = mempcpy (cp, serv->s_proto, s_proto_len);
221 cp = mempcpy (cp, s_aliases_len, s_aliases_cnt * sizeof (uint32_t));
222
223 /* Then the aliases. */
224 aliases = cp;
225 for (cnt = 0; cnt < s_aliases_cnt; ++cnt)
226 cp = mempcpy (cp, serv->s_aliases[cnt], s_aliases_len[cnt]);
227
228 assert (cp
229 == dataset->strdata + total - offsetof (struct dataset,
230 strdata));
231
232 char *key_copy = memcpy (cp, key, req->key_len);
233
234 /* Now we can determine whether on refill we have to create a new
235 record or not. */
236 if (he != NULL)
237 {
238 assert (fd == -1);
239
240 if (total + req->key_len == dh->allocsize
241 && total - offsetof (struct dataset, resp) == dh->recsize
242 && memcmp (&dataset->resp, dh->data,
243 dh->allocsize - offsetof (struct dataset, resp)) == 0)
244 {
245 /* The data has not changed. We will just bump the
246 timeout value. Note that the new record has been
247 allocated on the stack and need not be freed. */
248 dh->timeout = dataset->head.timeout;
249 ++dh->nreloads;
250 }
251 else
252 {
253 /* We have to create a new record. Just allocate
254 appropriate memory and copy it. */
255 struct dataset *newp
256 = (struct dataset *) mempool_alloc (db, total + req->key_len,
257 1);
258 if (newp != NULL)
259 {
260 /* Adjust pointers into the memory block. */
261 aliases = (char *) newp + (aliases - (char *) dataset);
262 assert (key_copy != NULL);
263 key_copy = (char *) newp + (key_copy - (char *) dataset);
264
265 dataset = memcpy (newp, dataset, total + req->key_len);
266 alloca_used = false;
267 }
268
269 /* Mark the old record as obsolete. */
270 dh->usable = false;
271 }
272 }
273 else
274 {
275 /* We write the dataset before inserting it to the database
276 since while inserting this thread might block and so would
277 unnecessarily keep the receiver waiting. */
278 assert (fd != -1);
279
280 if (writeall (fd, &dataset->resp, dataset->head.recsize)
281 != dataset->head.recsize)
282 all_written = false;
283 }
284
285 /* Add the record to the database. But only if it has not been
286 stored on the stack. */
287 if (! alloca_used)
288 {
289 /* If necessary, we also propagate the data to disk. */
290 if (db->persistent)
291 {
292 // XXX async OK?
293 uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1;
294 msync ((void *) pval,
295 ((uintptr_t) dataset & pagesize_m1)
296 + total + req->key_len, MS_ASYNC);
297 }
298
299 (void) cache_add (req->type, key_copy, req->key_len,
300 &dataset->head, true, db, owner, he == NULL);
301
302 pthread_rwlock_unlock (&db->lock);
303 }
304 }
305
306 if (__builtin_expect (!all_written, 0) && debug_level > 0)
307 {
308 char buf[256];
309 dbg_log (_("short write in %s: %s"), __FUNCTION__,
310 strerror_r (errno, buf, sizeof (buf)));
311 }
312
313 return timeout;
314 }
315
316
317 static int
318 lookup (int type, char *key, struct servent *resultbufp, char *buffer,
319 size_t buflen, struct servent **serv)
320 {
321 char *proto = strrchr (key, '/');
322 if (proto != NULL && proto != key)
323 {
324 key = strndupa (key, proto - key);
325 if (proto[1] == '\0')
326 proto = NULL;
327 else
328 ++proto;
329 }
330
331 if (type == GETSERVBYNAME)
332 return __getservbyname_r (key, proto, resultbufp, buffer, buflen, serv);
333
334 assert (type == GETSERVBYPORT);
335 return __getservbyport_r (atol (key), proto, resultbufp, buffer, buflen,
336 serv);
337 }
338
339
340 static time_t
341 addservbyX (struct database_dyn *db, int fd, request_header *req,
342 char *key, uid_t uid, struct hashentry *he, struct datahead *dh)
343 {
344 /* Search for the entry matching the key. Please note that we don't
345 look again in the table whether the dataset is now available. We
346 simply insert it. It does not matter if it is in there twice. The
347 pruning function only will look at the timestamp. */
348 struct servent resultbuf;
349 struct servent *serv;
350 int errval = 0;
351 struct scratch_buffer tmpbuf;
352 scratch_buffer_init (&tmpbuf);
353
354 if (__glibc_unlikely (debug_level > 0))
355 {
356 if (he == NULL)
357 dbg_log (_("Haven't found \"%s\" in services cache!"), key);
358 else
359 dbg_log (_("Reloading \"%s\" in services cache!"), key);
360 }
361
362 while (lookup (req->type, key, &resultbuf,
363 tmpbuf.data, tmpbuf.length, &serv) != 0
364 && (errval = errno) == ERANGE)
365 if (!scratch_buffer_grow (&tmpbuf))
366 {
367 /* We ran out of memory. We cannot do anything but sending a
368 negative response. In reality this should never
369 happen. */
370 serv = NULL;
371 /* We set the error to indicate this is (possibly) a temporary
372 error and that it does not mean the entry is not available
373 at all. */
374 errval = EAGAIN;
375 break;
376 }
377
378 time_t timeout = cache_addserv (db, fd, req, key, serv, uid, he, dh, errval);
379 scratch_buffer_free (&tmpbuf);
380 return timeout;
381 }
382
383
384 void
385 addservbyname (struct database_dyn *db, int fd, request_header *req,
386 void *key, uid_t uid)
387 {
388 addservbyX (db, fd, req, key, uid, NULL, NULL);
389 }
390
391
392 time_t
393 readdservbyname (struct database_dyn *db, struct hashentry *he,
394 struct datahead *dh)
395 {
396 request_header req =
397 {
398 .type = GETSERVBYNAME,
399 .key_len = he->len
400 };
401
402 return addservbyX (db, -1, &req, db->data + he->key, he->owner, he, dh);
403 }
404
405
406 void
407 addservbyport (struct database_dyn *db, int fd, request_header *req,
408 void *key, uid_t uid)
409 {
410 addservbyX (db, fd, req, key, uid, NULL, NULL);
411 }
412
413
414 time_t
415 readdservbyport (struct database_dyn *db, struct hashentry *he,
416 struct datahead *dh)
417 {
418 request_header req =
419 {
420 .type = GETSERVBYPORT,
421 .key_len = he->len
422 };
423
424 return addservbyX (db, -1, &req, db->data + he->key, he->owner, he, dh);
425 }