xref: /dragonfly/lib/libc/net/nsdispatch.c (revision ed183f8c)
1 /*	$NetBSD: nsdispatch.c,v 1.9 1999/01/25 00:16:17 lukem Exp $	*/
2 
3 /*-
4  * Copyright (c) 1997, 1998, 1999 The NetBSD Foundation, Inc.
5  * All rights reserved.
6  *
7  * This code is derived from software contributed to The NetBSD Foundation
8  * by Luke Mewburn.
9  *
10  * Redistribution and use in source and binary forms, with or without
11  * modification, are permitted provided that the following conditions
12  * are met:
13  * 1. Redistributions of source code must retain the above copyright
14  *    notice, this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in the
17  *    documentation and/or other materials provided with the distribution.
18  * 3. All advertising materials mentioning features or use of this software
19  *    must display the following acknowledgement:
20  *        This product includes software developed by the NetBSD
21  *        Foundation, Inc. and its contributors.
22  * 4. Neither the name of The NetBSD Foundation nor the names of its
23  *    contributors may be used to endorse or promote products derived
24  *    from this software without specific prior written permission.
25  *
26  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
27  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
28  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
29  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
30  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
31  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
32  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
33  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
34  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
35  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
36  * POSSIBILITY OF SUCH DAMAGE.
37  */
38 /*-
39  * Copyright (c) 2003 Networks Associates Technology, Inc.
40  * All rights reserved.
41  *
42  * Portions of this software were developed for the FreeBSD Project by
43  * Jacques A. Vidrine, Safeport Network Services, and Network
44  * Associates Laboratories, the Security Research Division of Network
45  * Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035
46  * ("CBOSS"), as part of the DARPA CHATS research program.
47  *
48  * Redistribution and use in source and binary forms, with or without
49  * modification, are permitted provided that the following conditions
50  * are met:
51  * 1. Redistributions of source code must retain the above copyright
52  *    notice, this list of conditions and the following disclaimer.
53  * 2. Redistributions in binary form must reproduce the above copyright
54  *    notice, this list of conditions and the following disclaimer in the
55  *    documentation and/or other materials provided with the distribution.
56  *
57  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
58  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
59  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
60  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
61  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
62  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
63  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
64  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
65  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
66  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
67  * SUCH DAMAGE.
68  *
69  * $FreeBSD: src/lib/libc/net/nsdispatch.c,v 1.17 2008/05/02 14:51:22 jhb Exp $
70  */
71 
72 #include "namespace.h"
73 #include <sys/param.h>
74 #include <sys/stat.h>
75 
76 #include <dlfcn.h>
77 #include <errno.h>
78 #include <fcntl.h>
79 #define _NS_PRIVATE
80 #include <nsswitch.h>
81 #include <pthread.h>
82 #include <stdio.h>
83 #include <stdlib.h>
84 #include <string.h>
85 #include <syslog.h>
86 #include <unistd.h>
87 #include "un-namespace.h"
88 #include "libc_private.h"
89 #ifdef NS_CACHING
90 #include "nscache.h"
91 #endif
92 
93 enum _nss_constants {
94 	/* Number of elements allocated when we grow a vector */
95 	ELEMSPERCHUNK =	8
96 };
97 
98 /*
99  * Global NSS data structures are mostly read-only, but we update
100  * them when we read or re-read the nsswitch.conf.
101  */
102 static	pthread_rwlock_t	nss_lock = PTHREAD_RWLOCK_INITIALIZER;
103 
104 /*
105  * Runtime determination of whether we are dynamically linked or not.
106  */
107 extern	int		_DYNAMIC __attribute__ ((weak));
108 #define	is_dynamic()	(&_DYNAMIC != NULL)
109 
110 /*
111  * default sourcelist: `files'
112  */
113 const ns_src __nsdefaultsrc[] = {
114 	{ NSSRC_FILES, NS_SUCCESS },
115 	{ 0 },
116 };
117 
118 /* Database, source mappings. */
119 static	unsigned int		 _nsmapsize;
120 static	ns_dbt			*_nsmap = NULL;
121 
122 /* NSS modules. */
123 static	unsigned int		 _nsmodsize;
124 static	ns_mod			*_nsmod;
125 
126 /* Placeholder for builtin modules' dlopen `handle'. */
127 static	int			 __nss_builtin_handle;
128 static	void			*nss_builtin_handle = &__nss_builtin_handle;
129 
130 #ifdef NS_CACHING
131 /*
132  * Cache lookup cycle prevention function - if !NULL then no cache lookups
133  * will be made
134  */
135 static	void			*nss_cache_cycle_prevention_func = NULL;
136 #endif
137 
138 /*
139  * When this is set to 1, nsdispatch won't use nsswitch.conf
140  * but will consult the 'defaults' source list only.
141  * NOTE: nested fallbacks (when nsdispatch calls fallback functions,
142  *     which in turn calls nsdispatch, which should call fallback
143  *     function) are not supported
144  */
145 static	int			fallback_dispatch = 0;
146 
147 /*
148  * Attempt to spew relatively uniform messages to syslog.
149  */
150 #define nss_log(level, fmt, ...) \
151 	syslog((level), "NSSWITCH(%s): " fmt, __func__, __VA_ARGS__)
152 #define nss_log_simple(level, s) \
153 	syslog((level), "NSSWITCH(%s): " s, __func__)
154 
155 /*
156  * Dynamically growable arrays are used for lists of databases, sources,
157  * and modules.  The following `vector' interface is used to isolate the
158  * common operations.
159  */
160 typedef	int	(*vector_comparison)(const void *, const void *);
161 typedef	void	(*vector_free_elem)(void *);
162 static	void	  vector_sort(void *, unsigned int, size_t,
163 		    vector_comparison);
164 static	void	  vector_free(void *, unsigned int *, size_t,
165 		    vector_free_elem);
166 static	void	 *vector_ref(unsigned int, void *, unsigned int, size_t);
167 static	void	 *vector_search(const void *, void *, unsigned int, size_t,
168 		    vector_comparison);
169 static	void	 *vector_append(const void *, void *, unsigned int *, size_t);
170 
171 
172 /*
173  * Internal interfaces.
174  */
175 static	int	 string_compare(const void *, const void *);
176 static	int	 mtab_compare(const void *, const void *);
177 static	int	 nss_configure(void);
178 static	void	 ns_dbt_free(ns_dbt *);
179 static	void	 ns_mod_free(ns_mod *);
180 static	void	 ns_src_free(ns_src **, int);
181 static	void	 nss_load_builtin_modules(void);
182 static	void	 nss_load_module(const char *, nss_module_register_fn);
183 static	void	 nss_atexit(void);
184 /* nsparser */
185 extern	FILE	*_nsyyin;
186 
187 
188 /*
189  * The vector operations
190  */
191 static void
192 vector_sort(void *vec, unsigned int count, size_t esize,
193     vector_comparison comparison)
194 {
195 	qsort(vec, count, esize, comparison);
196 }
197 
198 
199 static void *
200 vector_search(const void *key, void *vec, unsigned int count, size_t esize,
201     vector_comparison comparison)
202 {
203 	return (bsearch(key, vec, count, esize, comparison));
204 }
205 
206 
207 static void *
208 vector_append(const void *elem, void *vec, unsigned int *count, size_t esize)
209 {
210 	void	*p;
211 
212 	if ((*count % ELEMSPERCHUNK) == 0) {
213 		p = realloc(vec, (*count + ELEMSPERCHUNK) * esize);
214 		if (p == NULL) {
215 			nss_log_simple(LOG_ERR, "memory allocation failure");
216 			return (vec);
217 		}
218 		vec = p;
219 	}
220 	memmove((void *)(((uintptr_t)vec) + (*count * esize)), elem, esize);
221 	(*count)++;
222 	return (vec);
223 }
224 
225 
226 static void *
227 vector_ref(unsigned int i, void *vec, unsigned int count, size_t esize)
228 {
229 	if (i < count)
230 		return (void *)((uintptr_t)vec + (i * esize));
231 	else
232 		return (NULL);
233 }
234 
235 
236 #define VECTOR_FREE(v, c, s, f) \
237 	do { vector_free(v, c, s, f); v = NULL; } while (0)
238 static void
239 vector_free(void *vec, unsigned int *count, size_t esize,
240     vector_free_elem free_elem)
241 {
242 	unsigned int	 i;
243 	void		*elem;
244 
245 	for (i = 0; i < *count; i++) {
246 		elem = vector_ref(i, vec, *count, esize);
247 		if (elem != NULL)
248 			free_elem(elem);
249 	}
250 	free(vec);
251 	*count = 0;
252 }
253 
254 /*
255  * Comparison functions for vector_search.
256  */
257 static int
258 string_compare(const void *a, const void *b)
259 {
260       return (strcasecmp(*(const char * const *)a, *(const char * const *)b));
261 }
262 
263 
264 static int
265 mtab_compare(const void *a, const void *b)
266 {
267       int     cmp;
268 
269       cmp = strcmp(((const ns_mtab *)a)->name, ((const ns_mtab *)b)->name);
270       if (cmp != 0)
271 	      return (cmp);
272       else
273 	      return (strcmp(((const ns_mtab *)a)->database,
274 		  ((const ns_mtab *)b)->database));
275 }
276 
277 /*
278  * NSS nsmap management.
279  */
280 void
281 _nsdbtaddsrc(ns_dbt *dbt, const ns_src *src)
282 {
283 	const ns_mod	*modp;
284 
285 	dbt->srclist = vector_append(src, dbt->srclist, &dbt->srclistsize,
286 	    sizeof(*src));
287 	modp = vector_search(&src->name, _nsmod, _nsmodsize, sizeof(*_nsmod),
288 	    string_compare);
289 	if (modp == NULL)
290 		nss_load_module(src->name, NULL);
291 }
292 
293 
294 #ifdef _NSS_DEBUG
295 void
296 _nsdbtdump(const ns_dbt *dbt)
297 {
298 	int i;
299 
300 	printf("%s (%d source%s):", dbt->name, dbt->srclistsize,
301 	    dbt->srclistsize == 1 ? "" : "s");
302 	for (i = 0; i < (int)dbt->srclistsize; i++) {
303 		printf(" %s", dbt->srclist[i].name);
304 		if (!(dbt->srclist[i].flags &
305 		    (NS_UNAVAIL|NS_NOTFOUND|NS_TRYAGAIN)) &&
306 		    (dbt->srclist[i].flags & NS_SUCCESS))
307 			continue;
308 		printf(" [");
309 		if (!(dbt->srclist[i].flags & NS_SUCCESS))
310 			printf(" SUCCESS=continue");
311 		if (dbt->srclist[i].flags & NS_UNAVAIL)
312 			printf(" UNAVAIL=return");
313 		if (dbt->srclist[i].flags & NS_NOTFOUND)
314 			printf(" NOTFOUND=return");
315 		if (dbt->srclist[i].flags & NS_TRYAGAIN)
316 			printf(" TRYAGAIN=return");
317 		printf(" ]");
318 	}
319 	printf("\n");
320 }
321 #endif
322 
323 
324 /*
325  * The first time nsdispatch is called (during a process's lifetime,
326  * or after nsswitch.conf has been updated), nss_configure will
327  * prepare global data needed by NSS.
328  */
329 static int
330 nss_configure(void)
331 {
332 	static pthread_mutex_t conf_lock = PTHREAD_MUTEX_INITIALIZER;
333 	static time_t	 confmod;
334 	struct stat	 statbuf;
335 	int		 result, isthreaded;
336 	const char	*path;
337 #ifdef NS_CACHING
338 	void		*handle;
339 #endif
340 
341 	result = 0;
342 	isthreaded = __isthreaded;
343 #if defined(_NSS_DEBUG) && defined(_NSS_SHOOT_FOOT)
344 	/* NOTE WELL:  THIS IS A SECURITY HOLE. This must only be built
345 	 * for debugging purposes and MUST NEVER be used in production.
346 	 */
347 	path = getenv("NSSWITCH_CONF");
348 	if (path == NULL)
349 #endif
350 	path = _PATH_NS_CONF;
351 	if (stat(path, &statbuf) != 0)
352 		return (0);
353 	if (statbuf.st_mtime <= confmod)
354 		return (0);
355 	if (isthreaded) {
356 	    result = _pthread_mutex_trylock(&conf_lock);
357 	    if (result != 0)
358 		    return (0);
359 	    _pthread_rwlock_unlock(&nss_lock);
360 	    result = _pthread_rwlock_wrlock(&nss_lock);
361 	    if (result != 0)
362 		    goto fin2;
363 	}
364 	_nsyyin = fopen(path, "r");
365 	if (_nsyyin == NULL)
366 		goto fin;
367 	VECTOR_FREE(_nsmap, &_nsmapsize, sizeof(*_nsmap),
368 	    (vector_free_elem)ns_dbt_free);
369 	VECTOR_FREE(_nsmod, &_nsmodsize, sizeof(*_nsmod),
370 	    (vector_free_elem)ns_mod_free);
371 	nss_load_builtin_modules();
372 	_nsyyparse();
373 	fclose(_nsyyin);
374 	vector_sort(_nsmap, _nsmapsize, sizeof(*_nsmap), string_compare);
375 	if (confmod == 0)
376 		atexit(nss_atexit);
377 	confmod = statbuf.st_mtime;
378 
379 #ifdef NS_CACHING
380 	handle = libc_dlopen(NULL, RTLD_LAZY | RTLD_GLOBAL);
381 	if (handle != NULL) {
382 		nss_cache_cycle_prevention_func = dlsym(handle,
383 			"_nss_cache_cycle_prevention_function");
384 		dlclose(handle);
385 	}
386 #endif
387 fin:
388 	if (isthreaded) {
389 	    _pthread_rwlock_unlock(&nss_lock);
390 	    if (result == 0)
391 		    result = _pthread_rwlock_rdlock(&nss_lock);
392 	}
393 fin2:
394 	if (isthreaded)
395 		_pthread_mutex_unlock(&conf_lock);
396 	return (result);
397 }
398 
399 
400 void
401 _nsdbtput(const ns_dbt *dbt)
402 {
403 	unsigned int	 i;
404 	ns_dbt		*p;
405 
406 	for (i = 0; i < _nsmapsize; i++) {
407 		p = vector_ref(i, _nsmap, _nsmapsize, sizeof(*_nsmap));
408 		if (string_compare(&dbt->name, &p->name) == 0) {
409 			/* overwrite existing entry */
410 			if (p->srclist != NULL)
411 				ns_src_free(&p->srclist, p->srclistsize);
412 			memmove(p, dbt, sizeof(*dbt));
413 			return;
414 		}
415 	}
416 	_nsmap = vector_append(dbt, _nsmap, &_nsmapsize, sizeof(*_nsmap));
417 }
418 
419 
420 static void
421 ns_dbt_free(ns_dbt *dbt)
422 {
423 	ns_src_free(&dbt->srclist, dbt->srclistsize);
424 	if (dbt->name)
425 		free((void *)dbt->name);
426 }
427 
428 
429 static void
430 ns_src_free(ns_src **src, int srclistsize)
431 {
432 	int	i;
433 
434 	for (i = 0; i < srclistsize; i++)
435 		if ((*src)[i].name != NULL)
436 			/* This one was allocated by nslexer. You'll just
437 			 * have to trust me.
438 			 */
439 			free((void *)((*src)[i].name));
440 	free(*src);
441 	*src = NULL;
442 }
443 
444 
445 
446 /*
447  * NSS module management.
448  */
449 /* The built-in NSS modules are all loaded at once. */
450 #define NSS_BACKEND(name, reg) \
451 ns_mtab	*reg(unsigned int *, nss_module_unregister_fn *);
452 #include "nss_backends.h"
453 #undef NSS_BACKEND
454 
455 static void
456 nss_load_builtin_modules(void)
457 {
458 #define NSS_BACKEND(name, reg) nss_load_module(#name, reg);
459 #include "nss_backends.h"
460 #undef NSS_BACKEND
461 }
462 
463 
464 /* Load a built-in or dynamically linked module.  If the `reg_fn'
465  * argument is non-NULL, assume a built-in module and use reg_fn to
466  * register it.  Otherwise, search for a dynamic NSS module.
467  */
468 static void
469 nss_load_module(const char *source, nss_module_register_fn reg_fn)
470 {
471 	char		 buf[PATH_MAX];
472 	ns_mod		 mod;
473 	nss_module_register_fn fn;
474 
475 	memset(&mod, 0, sizeof(mod));
476 	mod.name = strdup(source);
477 	if (mod.name == NULL) {
478 		nss_log_simple(LOG_ERR, "memory allocation failure");
479 		return;
480 	}
481 	if (reg_fn != NULL) {
482 		/* The placeholder is required, as a NULL handle
483 		 * represents an invalid module.
484 		 */
485 		mod.handle = nss_builtin_handle;
486 		fn = reg_fn;
487 	} else if (!is_dynamic())
488 		goto fin;
489 	else {
490 		if (snprintf(buf, sizeof(buf), "nss_%s.so.%d", mod.name,
491 		    NSS_MODULE_INTERFACE_VERSION) >= (int)sizeof(buf))
492 			goto fin;
493 		mod.handle = libc_dlopen(buf, RTLD_LOCAL|RTLD_LAZY);
494 		if (mod.handle == NULL) {
495 #ifdef _NSS_DEBUG
496 			/* This gets pretty annoying since the built-in
497 			 * sources aren't modules yet.
498 			 */
499 			nss_log(LOG_DEBUG, "%s, %s", mod.name, dlerror());
500 #endif
501 			goto fin;
502 		}
503 		fn = (nss_module_register_fn)dlfunc(mod.handle,
504 		    "nss_module_register");
505 		if (fn == NULL) {
506 			dlclose(mod.handle);
507 			mod.handle = NULL;
508 			nss_log(LOG_ERR, "%s, %s", mod.name, dlerror());
509 			goto fin;
510 		}
511 	}
512 	mod.mtab = fn(mod.name, &mod.mtabsize, &mod.unregister);
513 	if (mod.mtab == NULL || mod.mtabsize == 0) {
514 		if (mod.handle != nss_builtin_handle)
515 			dlclose(mod.handle);
516 		mod.handle = NULL;
517 		nss_log(LOG_ERR, "%s, registration failed", mod.name);
518 		goto fin;
519 	}
520 	if (mod.mtabsize > 1)
521 		qsort(mod.mtab, mod.mtabsize, sizeof(mod.mtab[0]),
522 		    mtab_compare);
523 fin:
524 	_nsmod = vector_append(&mod, _nsmod, &_nsmodsize, sizeof(*_nsmod));
525 	vector_sort(_nsmod, _nsmodsize, sizeof(*_nsmod), string_compare);
526 }
527 
528 
529 
530 static void
531 ns_mod_free(ns_mod *mod)
532 {
533 
534 	free(mod->name);
535 	if (mod->handle == NULL)
536 		return;
537 	if (mod->unregister != NULL)
538 		mod->unregister(mod->mtab, mod->mtabsize);
539 	if (mod->handle != nss_builtin_handle)
540 		dlclose(mod->handle);
541 }
542 
543 
544 
545 /*
546  * Cleanup
547  */
548 static void
549 nss_atexit(void)
550 {
551 	int isthreaded;
552 
553 	isthreaded = __isthreaded;
554 	if (isthreaded)
555 		_pthread_rwlock_wrlock(&nss_lock);
556 	VECTOR_FREE(_nsmap, &_nsmapsize, sizeof(*_nsmap),
557 	    (vector_free_elem)ns_dbt_free);
558 	VECTOR_FREE(_nsmod, &_nsmodsize, sizeof(*_nsmod),
559 	    (vector_free_elem)ns_mod_free);
560 	if (isthreaded)
561 		_pthread_rwlock_unlock(&nss_lock);
562 }
563 
564 
565 
566 /*
567  * Finally, the actual implementation.
568  */
569 static nss_method
570 nss_method_lookup(const char *source, const char *database,
571     const char *method, const ns_dtab disp_tab[], void **mdata)
572 {
573 	ns_mod	*mod;
574 	ns_mtab	*match, key;
575 	int	 i;
576 
577 	if (disp_tab != NULL)
578 		for (i = 0; disp_tab[i].src != NULL; i++)
579 			if (strcasecmp(source, disp_tab[i].src) == 0) {
580 				*mdata = disp_tab[i].mdata;
581 				return (disp_tab[i].method);
582 			}
583 	mod = vector_search(&source, _nsmod, _nsmodsize, sizeof(*_nsmod),
584 	    string_compare);
585 	if (mod != NULL && mod->handle != NULL) {
586 		key.database = database;
587 		key.name = method;
588 		match = bsearch(&key, mod->mtab, mod->mtabsize,
589 		    sizeof(mod->mtab[0]), mtab_compare);
590 		if (match != NULL) {
591 			*mdata = match->mdata;
592 			return (match->method);
593 		}
594 	}
595 
596 	*mdata = NULL;
597 	return (NULL);
598 }
599 
600 
601 int
602 _nsdispatch(void *retval, const ns_dtab disp_tab[], const char *database,
603 	    const char *method_name, const ns_src defaults[], ...)
604 {
605 	va_list		 ap;
606 	const ns_dbt	*dbt;
607 	const ns_src	*srclist;
608 	nss_method	 method, fb_method;
609 	void		*mdata;
610 	int		 isthreaded, serrno, i, result, srclistsize;
611 
612 #ifdef NS_CACHING
613 	nss_cache_data	 cache_data;
614 	nss_cache_data	*cache_data_p;
615 	int		 cache_flag;
616 #endif
617 
618 	dbt = NULL;
619 	fb_method = NULL;
620 
621 	isthreaded = __isthreaded;
622 	serrno = errno;
623 	if (isthreaded) {
624 		result = _pthread_rwlock_rdlock(&nss_lock);
625 		if (result != 0) {
626 			result = NS_UNAVAIL;
627 			goto fin;
628 		}
629 	}
630 	result = nss_configure();
631 	if (result != 0) {
632 		result = NS_UNAVAIL;
633 		goto fin;
634 	}
635 	if (fallback_dispatch == 0) {
636 		dbt = vector_search(&database, _nsmap, _nsmapsize, sizeof(*_nsmap),
637 		    string_compare);
638 		fb_method = nss_method_lookup(NSSRC_FALLBACK, database,
639 		    method_name, disp_tab, &mdata);
640 	}
641 
642 	if (dbt != NULL) {
643 		srclist = dbt->srclist;
644 		srclistsize = dbt->srclistsize;
645 	} else {
646 		srclist = defaults;
647 		srclistsize = 0;
648 		while (srclist[srclistsize].name != NULL)
649 			srclistsize++;
650 	}
651 
652 #ifdef NS_CACHING
653 	cache_data_p = NULL;
654 	cache_flag = 0;
655 #endif
656 	for (i = 0; i < srclistsize; i++) {
657 		result = NS_NOTFOUND;
658 		method = nss_method_lookup(srclist[i].name, database,
659 		    method_name, disp_tab, &mdata);
660 
661 		if (method != NULL) {
662 #ifdef NS_CACHING
663 			if (strcmp(srclist[i].name, NSSRC_CACHE) == 0 &&
664 			    nss_cache_cycle_prevention_func == NULL) {
665 #ifdef NS_STRICT_LIBC_EID_CHECKING
666 				if (issetugid() != 0)
667 					continue;
668 #endif
669 				cache_flag = 1;
670 
671 				memset(&cache_data, 0, sizeof(nss_cache_data));
672 				cache_data.info = (nss_cache_info const *)mdata;
673 				cache_data_p = &cache_data;
674 
675 				va_start(ap, defaults);
676 				if (cache_data.info->id_func != NULL)
677 					result = __nss_common_cache_read(retval,
678 					    cache_data_p, ap);
679 				else if (cache_data.info->marshal_func != NULL)
680 					result = __nss_mp_cache_read(retval,
681 					    cache_data_p, ap);
682 				else
683 					result = __nss_mp_cache_end(retval,
684 					    cache_data_p, ap);
685 				va_end(ap);
686 			} else {
687 				cache_flag = 0;
688 				va_start(ap, defaults);
689 				result = method(retval, mdata, ap);
690 				va_end(ap);
691 			}
692 #else /* NS_CACHING */
693 			va_start(ap, defaults);
694 			result = method(retval, mdata, ap);
695 			va_end(ap);
696 #endif /* NS_CACHING */
697 
698 			if (result & (srclist[i].flags))
699 				break;
700 		} else {
701 			if (fb_method != NULL) {
702 				fallback_dispatch = 1;
703 				va_start(ap, defaults);
704 				result = fb_method(retval,
705 				    (void *)srclist[i].name, ap);
706 				va_end(ap);
707 				fallback_dispatch = 0;
708 			} else
709 				nss_log(LOG_DEBUG, "%s, %s, %s, not found, "
710 				    "and no fallback provided",
711 				    srclist[i].name, database, method_name);
712 		}
713 	}
714 
715 #ifdef NS_CACHING
716 	if (cache_data_p != NULL &&
717 	    (result & (NS_NOTFOUND | NS_SUCCESS)) && cache_flag == 0) {
718 		va_start(ap, defaults);
719 		if (result == NS_SUCCESS) {
720 			if (cache_data.info->id_func != NULL)
721 				__nss_common_cache_write(retval, cache_data_p,
722 				    ap);
723 			else if (cache_data.info->marshal_func != NULL)
724 				__nss_mp_cache_write(retval, cache_data_p, ap);
725 		} else if (result == NS_NOTFOUND) {
726 			if (cache_data.info->id_func == NULL) {
727 				if (cache_data.info->marshal_func != NULL)
728 					__nss_mp_cache_write_submit(retval,
729 					    cache_data_p, ap);
730 			} else
731 				__nss_common_cache_write_negative(cache_data_p);
732 		}
733 		va_end(ap);
734 	}
735 #endif /* NS_CACHING */
736 
737 	if (isthreaded)
738 		_pthread_rwlock_unlock(&nss_lock);
739 fin:
740 	errno = serrno;
741 	return (result);
742 }
743 
744 __weak_reference(_nsdispatch, nsdispatch);
745