1/* Cache handling for services lookup.
2 Copyright (C) 2007-2021 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4 Contributed by Ulrich Drepper <drepper@drepper.com>, 2007.
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 <https://www.gnu.org/licenses/>. */
18
19#include <assert.h>
20#include <errno.h>
21#include <libintl.h>
22#include <netdb.h>
23#include <unistd.h>
24#include <stdint.h>
25#include <sys/mman.h>
26#include <kernel-features.h>
27#include <scratch_buffer.h>
28
29#include "nscd.h"
30#include "dbg_log.h"
31
32
33/* This is the standard reply in case the service is disabled. */
34static const serv_response_header disabled =
35{
36 .version = NSCD_VERSION,
37 .found = -1,
38 .s_name_len = 0,
39 .s_proto_len = 0,
40 .s_aliases_cnt = 0,
41 .s_port = -1
42};
43
44/* This is the struct describing how to write this record. */
45const struct iovec serv_iov_disabled =
46{
47 .iov_base = (void *) &disabled,
48 .iov_len = sizeof (disabled)
49};
50
51
52/* This is the standard reply in case we haven't found the dataset. */
53static const serv_response_header notfound =
54{
55 .version = NSCD_VERSION,
56 .found = 0,
57 .s_name_len = 0,
58 .s_proto_len = 0,
59 .s_aliases_cnt = 0,
60 .s_port = -1
61};
62
63
64static time_t
65cache_addserv (struct database_dyn *db, int fd, request_header *req,
66 const void *key, struct servent *serv, uid_t owner,
67 struct hashentry *const he, struct datahead *dh, int errval)
68{
69 bool all_written = true;
70 ssize_t total;
71 time_t t = time (NULL);
72
73 /* We allocate all data in one memory block: the iov vector,
74 the response header and the dataset itself. */
75 struct dataset
76 {
77 struct datahead head;
78 serv_response_header resp;
79 char strdata[0];
80 } *dataset;
81
82 assert (offsetof (struct dataset, resp) == offsetof (struct datahead, data));
83
84 time_t timeout = MAX_TIMEOUT_VALUE;
85 if (serv == NULL)
86 {
87 if (he != NULL && errval == EAGAIN)
88 {
89 /* If we have an old record available but cannot find one
90 now because the service is not available we keep the old
91 record and make sure it does not get removed. */
92 if (reload_count != UINT_MAX)
93 /* Do not reset the value if we never not reload the record. */
94 dh->nreloads = reload_count - 1;
95
96 /* Reload with the same time-to-live value. */
97 timeout = dh->timeout = t + db->postimeout;
98
99 total = 0;
100 }
101 else
102 {
103 /* We have no data. This means we send the standard reply for this
104 case. */
105 total = sizeof (notfound);
106
107 if (fd != -1
108 && TEMP_FAILURE_RETRY (send (fd, &notfound, total,
109 MSG_NOSIGNAL)) != total)
110 all_written = false;
111
112 /* If we have a transient error or cannot permanently store
113 the result, so be it. */
114 if (errval == EAGAIN || __builtin_expect (db->negtimeout == 0, 0))
115 {
116 /* Mark the old entry as obsolete. */
117 if (dh != NULL)
118 dh->usable = false;
119 }
120 else if ((dataset = mempool_alloc (db, (sizeof (struct dataset)
121 + req->key_len), 1)) != NULL)
122 {
123 timeout = datahead_init_neg (&dataset->head,
124 (sizeof (struct dataset)
125 + req->key_len), total,
126 db->negtimeout);
127
128 /* This is the reply. */
129 memcpy (&dataset->resp, &notfound, total);
130
131 /* Copy the key data. */
132 memcpy (dataset->strdata, key, req->key_len);
133
134 /* If necessary, we also propagate the data to disk. */
135 if (db->persistent)
136 {
137 // XXX async OK?
138 uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1;
139 msync ((void *) pval,
140 ((uintptr_t) dataset & pagesize_m1)
141 + sizeof (struct dataset) + req->key_len, MS_ASYNC);
142 }
143
144 (void) cache_add (req->type, &dataset->strdata, req->key_len,
145 &dataset->head, true, db, owner, he == NULL);
146
147 pthread_rwlock_unlock (&db->lock);
148
149 /* Mark the old entry as obsolete. */
150 if (dh != NULL)
151 dh->usable = false;
152 }
153 }
154 }
155 else
156 {
157 /* Determine the I/O structure. */
158 size_t s_name_len = strlen (serv->s_name) + 1;
159 size_t s_proto_len = strlen (serv->s_proto) + 1;
160 uint32_t *s_aliases_len;
161 size_t s_aliases_cnt;
162 char *aliases;
163 char *cp;
164 size_t cnt;
165
166 /* Determine the number of aliases. */
167 s_aliases_cnt = 0;
168 for (cnt = 0; serv->s_aliases[cnt] != NULL; ++cnt)
169 ++s_aliases_cnt;
170 /* Determine the length of all aliases. */
171 s_aliases_len = (uint32_t *) alloca (s_aliases_cnt * sizeof (uint32_t));
172 total = 0;
173 for (cnt = 0; cnt < s_aliases_cnt; ++cnt)
174 {
175 s_aliases_len[cnt] = strlen (serv->s_aliases[cnt]) + 1;
176 total += s_aliases_len[cnt];
177 }
178
179 total += (offsetof (struct dataset, strdata)
180 + s_name_len
181 + s_proto_len
182 + s_aliases_cnt * sizeof (uint32_t));
183
184 /* If we refill the cache, first assume the reconrd did not
185 change. Allocate memory on the cache since it is likely
186 discarded anyway. If it turns out to be necessary to have a
187 new record we can still allocate real memory. */
188 bool alloca_used = false;
189 dataset = NULL;
190
191 if (he == NULL)
192 dataset = (struct dataset *) mempool_alloc (db, total + req->key_len,
193 1);
194
195 if (dataset == NULL)
196 {
197 /* We cannot permanently add the result in the moment. But
198 we can provide the result as is. Store the data in some
199 temporary memory. */
200 dataset = (struct dataset *) alloca (total + req->key_len);
201
202 /* We cannot add this record to the permanent database. */
203 alloca_used = true;
204 }
205
206 timeout = datahead_init_pos (&dataset->head, total + req->key_len,
207 total - offsetof (struct dataset, resp),
208 he == NULL ? 0 : dh->nreloads + 1,
209 db->postimeout);
210
211 dataset->resp.version = NSCD_VERSION;
212 dataset->resp.found = 1;
213 dataset->resp.s_name_len = s_name_len;
214 dataset->resp.s_proto_len = s_proto_len;
215 dataset->resp.s_port = serv->s_port;
216 dataset->resp.s_aliases_cnt = s_aliases_cnt;
217
218 cp = dataset->strdata;
219
220 cp = mempcpy (cp, serv->s_name, s_name_len);
221 cp = mempcpy (cp, serv->s_proto, s_proto_len);
222 cp = mempcpy (cp, s_aliases_len, s_aliases_cnt * sizeof (uint32_t));
223
224 /* Then the aliases. */
225 aliases = cp;
226 for (cnt = 0; cnt < s_aliases_cnt; ++cnt)
227 cp = mempcpy (cp, serv->s_aliases[cnt], s_aliases_len[cnt]);
228
229 assert (cp
230 == dataset->strdata + total - offsetof (struct dataset,
231 strdata));
232
233 char *key_copy = memcpy (cp, key, req->key_len);
234
235 /* Now we can determine whether on refill we have to create a new
236 record or not. */
237 if (he != NULL)
238 {
239 assert (fd == -1);
240
241 if (total + req->key_len == dh->allocsize
242 && total - offsetof (struct dataset, resp) == dh->recsize
243 && memcmp (&dataset->resp, dh->data,
244 dh->allocsize - offsetof (struct dataset, resp)) == 0)
245 {
246 /* The data has not changed. We will just bump the
247 timeout value. Note that the new record has been
248 allocated on the stack and need not be freed. */
249 dh->timeout = dataset->head.timeout;
250 ++dh->nreloads;
251 }
252 else
253 {
254 /* We have to create a new record. Just allocate
255 appropriate memory and copy it. */
256 struct dataset *newp
257 = (struct dataset *) mempool_alloc (db, total + req->key_len,
258 1);
259 if (newp != NULL)
260 {
261 /* Adjust pointers into the memory block. */
262 aliases = (char *) newp + (aliases - (char *) dataset);
263 assert (key_copy != NULL);
264 key_copy = (char *) newp + (key_copy - (char *) dataset);
265
266 dataset = memcpy (newp, dataset, total + req->key_len);
267 alloca_used = false;
268 }
269
270 /* Mark the old record as obsolete. */
271 dh->usable = false;
272 }
273 }
274 else
275 {
276 /* We write the dataset before inserting it to the database
277 since while inserting this thread might block and so would
278 unnecessarily keep the receiver waiting. */
279 assert (fd != -1);
280
281 if (writeall (fd, &dataset->resp, dataset->head.recsize)
282 != dataset->head.recsize)
283 all_written = false;
284 }
285
286 /* Add the record to the database. But only if it has not been
287 stored on the stack. */
288 if (! alloca_used)
289 {
290 /* If necessary, we also propagate the data to disk. */
291 if (db->persistent)
292 {
293 // XXX async OK?
294 uintptr_t pval = (uintptr_t) dataset & ~pagesize_m1;
295 msync ((void *) pval,
296 ((uintptr_t) dataset & pagesize_m1)
297 + total + req->key_len, MS_ASYNC);
298 }
299
300 (void) cache_add (req->type, key_copy, req->key_len,
301 &dataset->head, true, db, owner, he == NULL);
302
303 pthread_rwlock_unlock (&db->lock);
304 }
305 }
306
307 if (__builtin_expect (!all_written, 0) && debug_level > 0)
308 {
309 char buf[256];
310 dbg_log (_("short write in %s: %s"), __FUNCTION__,
311 strerror_r (errno, buf, sizeof (buf)));
312 }
313
314 return timeout;
315}
316
317
318static int
319lookup (int type, char *key, struct servent *resultbufp, char *buffer,
320 size_t buflen, struct servent **serv)
321{
322 char *proto = strrchr (key, '/');
323 if (proto != NULL && proto != key)
324 {
325 key = strndupa (key, proto - key);
326 if (proto[1] == '\0')
327 proto = NULL;
328 else
329 ++proto;
330 }
331
332 if (type == GETSERVBYNAME)
333 return __getservbyname_r (key, proto, resultbufp, buffer, buflen, serv);
334
335 assert (type == GETSERVBYPORT);
336 return __getservbyport_r (atol (key), proto, resultbufp, buffer, buflen,
337 serv);
338}
339
340
341static time_t
342addservbyX (struct database_dyn *db, int fd, request_header *req,
343 char *key, uid_t uid, struct hashentry *he, struct datahead *dh)
344{
345 /* Search for the entry matching the key. Please note that we don't
346 look again in the table whether the dataset is now available. We
347 simply insert it. It does not matter if it is in there twice. The
348 pruning function only will look at the timestamp. */
349 struct servent resultbuf;
350 struct servent *serv;
351 int errval = 0;
352 struct scratch_buffer tmpbuf;
353 scratch_buffer_init (&tmpbuf);
354
355 if (__glibc_unlikely (debug_level > 0))
356 {
357 if (he == NULL)
358 dbg_log (_("Haven't found \"%s\" in services cache!"), key);
359 else
360 dbg_log (_("Reloading \"%s\" in services cache!"), key);
361 }
362
363 while (lookup (req->type, key, &resultbuf,
364 tmpbuf.data, tmpbuf.length, &serv) != 0
365 && (errval = errno) == ERANGE)
366 if (!scratch_buffer_grow (&tmpbuf))
367 {
368 /* We ran out of memory. We cannot do anything but sending a
369 negative response. In reality this should never
370 happen. */
371 serv = NULL;
372 /* We set the error to indicate this is (possibly) a temporary
373 error and that it does not mean the entry is not available
374 at all. */
375 errval = EAGAIN;
376 break;
377 }
378
379 time_t timeout = cache_addserv (db, fd, req, key, serv, uid, he, dh, errval);
380 scratch_buffer_free (&tmpbuf);
381 return timeout;
382}
383
384
385void
386addservbyname (struct database_dyn *db, int fd, request_header *req,
387 void *key, uid_t uid)
388{
389 addservbyX (db, fd, req, key, uid, NULL, NULL);
390}
391
392
393time_t
394readdservbyname (struct database_dyn *db, struct hashentry *he,
395 struct datahead *dh)
396{
397 request_header req =
398 {
399 .type = GETSERVBYNAME,
400 .key_len = he->len
401 };
402
403 return addservbyX (db, -1, &req, db->data + he->key, he->owner, he, dh);
404}
405
406
407void
408addservbyport (struct database_dyn *db, int fd, request_header *req,
409 void *key, uid_t uid)
410{
411 addservbyX (db, fd, req, key, uid, NULL, NULL);
412}
413
414
415time_t
416readdservbyport (struct database_dyn *db, struct hashentry *he,
417 struct datahead *dh)
418{
419 request_header req =
420 {
421 .type = GETSERVBYPORT,
422 .key_len = he->len
423 };
424
425 return addservbyX (db, -1, &req, db->data + he->key, he->owner, he, dh);
426}
427