xref: /freebsd/lib/libc/net/nsdispatch.c (revision f4b37ed0f8b307b1f3f0f630ca725d68f1dff30d)
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  *
19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29  * POSSIBILITY OF SUCH DAMAGE.
30  */
31 /*-
32  * Copyright (c) 2003 Networks Associates Technology, Inc.
33  * All rights reserved.
34  *
35  * Portions of this software were developed for the FreeBSD Project by
36  * Jacques A. Vidrine, Safeport Network Services, and Network
37  * Associates Laboratories, the Security Research Division of Network
38  * Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035
39  * ("CBOSS"), as part of the DARPA CHATS research program.
40  *
41  * Redistribution and use in source and binary forms, with or without
42  * modification, are permitted provided that the following conditions
43  * are met:
44  * 1. Redistributions of source code must retain the above copyright
45  *    notice, this list of conditions and the following disclaimer.
46  * 2. Redistributions in binary form must reproduce the above copyright
47  *    notice, this list of conditions and the following disclaimer in the
48  *    documentation and/or other materials provided with the distribution.
49  *
50  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
51  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
52  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
53  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
54  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
55  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
56  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
57  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
58  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
59  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
60  * SUCH DAMAGE.
61  *
62  */
63 #include <sys/cdefs.h>
64 __FBSDID("$FreeBSD$");
65 
66 #include "namespace.h"
67 #include <sys/param.h>
68 #include <sys/stat.h>
69 
70 #include <dlfcn.h>
71 #include <errno.h>
72 #include <fcntl.h>
73 #define _NS_PRIVATE
74 #include <nsswitch.h>
75 #include <pthread.h>
76 #include <pthread_np.h>
77 #include <stdio.h>
78 #include <stdlib.h>
79 #include <string.h>
80 #include <syslog.h>
81 #include <unistd.h>
82 #include "un-namespace.h"
83 #include "nss_tls.h"
84 #include "libc_private.h"
85 #ifdef NS_CACHING
86 #include "nscache.h"
87 #endif
88 
89 enum _nss_constants {
90 	/* Number of elements allocated when we grow a vector */
91 	ELEMSPERCHUNK =	8
92 };
93 
94 /*
95  * Global NSS data structures are mostly read-only, but we update
96  * them when we read or re-read the nsswitch.conf.
97  */
98 static	pthread_rwlock_t	nss_lock = PTHREAD_RWLOCK_INITIALIZER;
99 
100 /*
101  * Runtime determination of whether we are dynamically linked or not.
102  */
103 extern	int		_DYNAMIC __attribute__ ((weak));
104 #define	is_dynamic()	(&_DYNAMIC != NULL)
105 
106 /*
107  * default sourcelist: `files'
108  */
109 const ns_src __nsdefaultsrc[] = {
110 	{ NSSRC_FILES, NS_SUCCESS },
111 	{ 0 },
112 };
113 
114 /* Database, source mappings. */
115 static	unsigned int		 _nsmapsize;
116 static	ns_dbt			*_nsmap = NULL;
117 
118 /* NSS modules. */
119 static	unsigned int		 _nsmodsize;
120 static	ns_mod			*_nsmod;
121 
122 /* Placeholder for builtin modules' dlopen `handle'. */
123 static	int			 __nss_builtin_handle;
124 static	void			*nss_builtin_handle = &__nss_builtin_handle;
125 
126 #ifdef NS_CACHING
127 /*
128  * Cache lookup cycle prevention function - if !NULL then no cache lookups
129  * will be made
130  */
131 static	void			*nss_cache_cycle_prevention_func = NULL;
132 #endif
133 
134 /*
135  * We keep track of nsdispatch() nesting depth in dispatch_depth.  When a
136  * fallback method is invoked from nsdispatch(), we temporarily set
137  * fallback_depth to the current dispatch depth plus one.  Subsequent
138  * calls at that exact depth will run in fallback mode (restricted to the
139  * same source as the call that was handled by the fallback method), while
140  * calls below that depth will be handled normally, allowing fallback
141  * methods to perform arbitrary lookups.
142  */
143 struct fb_state {
144 	int	dispatch_depth;
145 	int	fallback_depth;
146 };
147 static	void	fb_endstate(void *);
148 NSS_TLS_HANDLING(fb);
149 
150 /*
151  * Attempt to spew relatively uniform messages to syslog.
152  */
153 #define nss_log(level, fmt, ...) \
154 	syslog((level), "NSSWITCH(%s): " fmt, __func__, __VA_ARGS__)
155 #define nss_log_simple(level, s) \
156 	syslog((level), "NSSWITCH(%s): " s, __func__)
157 
158 /*
159  * Dynamically growable arrays are used for lists of databases, sources,
160  * and modules.  The following `vector' interface is used to isolate the
161  * common operations.
162  */
163 typedef	int	(*vector_comparison)(const void *, const void *);
164 typedef	void	(*vector_free_elem)(void *);
165 static	void	  vector_sort(void *, unsigned int, size_t,
166 		    vector_comparison);
167 static	void	  vector_free(void *, unsigned int *, size_t,
168 		    vector_free_elem);
169 static	void	 *vector_ref(unsigned int, void *, unsigned int, size_t);
170 static	void	 *vector_search(const void *, void *, unsigned int, size_t,
171 		    vector_comparison);
172 static	void	 *vector_append(const void *, void *, unsigned int *, size_t);
173 
174 
175 /*
176  * Internal interfaces.
177  */
178 static	int	 string_compare(const void *, const void *);
179 static	int	 mtab_compare(const void *, const void *);
180 static	int	 nss_configure(void);
181 static	void	 ns_dbt_free(ns_dbt *);
182 static	void	 ns_mod_free(ns_mod *);
183 static	void	 ns_src_free(ns_src **, int);
184 static	void	 nss_load_builtin_modules(void);
185 static	void	 nss_load_module(const char *, nss_module_register_fn);
186 static	void	 nss_atexit(void);
187 /* nsparser */
188 extern	FILE	*_nsyyin;
189 
190 
191 /*
192  * The vector operations
193  */
194 static void
195 vector_sort(void *vec, unsigned int count, size_t esize,
196     vector_comparison comparison)
197 {
198 	qsort(vec, count, esize, comparison);
199 }
200 
201 
202 static void *
203 vector_search(const void *key, void *vec, unsigned int count, size_t esize,
204     vector_comparison comparison)
205 {
206 	return (bsearch(key, vec, count, esize, comparison));
207 }
208 
209 
210 static void *
211 vector_append(const void *elem, void *vec, unsigned int *count, size_t esize)
212 {
213 	void	*p;
214 
215 	if ((*count % ELEMSPERCHUNK) == 0) {
216 		p = realloc(vec, (*count + ELEMSPERCHUNK) * esize);
217 		if (p == NULL) {
218 			nss_log_simple(LOG_ERR, "memory allocation failure");
219 			return (vec);
220 		}
221 		vec = p;
222 	}
223 	memmove((void *)(((uintptr_t)vec) + (*count * esize)), elem, esize);
224 	(*count)++;
225 	return (vec);
226 }
227 
228 
229 static void *
230 vector_ref(unsigned int i, void *vec, unsigned int count, size_t esize)
231 {
232 	if (i < count)
233 		return (void *)((uintptr_t)vec + (i * esize));
234 	else
235 		return (NULL);
236 }
237 
238 
239 #define VECTOR_FREE(v, c, s, f) \
240 	do { vector_free(v, c, s, f); v = NULL; } while (0)
241 static void
242 vector_free(void *vec, unsigned int *count, size_t esize,
243     vector_free_elem free_elem)
244 {
245 	unsigned int	 i;
246 	void		*elem;
247 
248 	for (i = 0; i < *count; i++) {
249 		elem = vector_ref(i, vec, *count, esize);
250 		if (elem != NULL)
251 			free_elem(elem);
252 	}
253 	free(vec);
254 	*count = 0;
255 }
256 
257 /*
258  * Comparison functions for vector_search.
259  */
260 static int
261 string_compare(const void *a, const void *b)
262 {
263       return (strcasecmp(*(const char * const *)a, *(const char * const *)b));
264 }
265 
266 
267 static int
268 mtab_compare(const void *a, const void *b)
269 {
270       int     cmp;
271 
272       cmp = strcmp(((const ns_mtab *)a)->name, ((const ns_mtab *)b)->name);
273       if (cmp != 0)
274 	      return (cmp);
275       else
276 	      return (strcmp(((const ns_mtab *)a)->database,
277 		  ((const ns_mtab *)b)->database));
278 }
279 
280 /*
281  * NSS nsmap management.
282  */
283 void
284 _nsdbtaddsrc(ns_dbt *dbt, const ns_src *src)
285 {
286 	const ns_mod	*modp;
287 
288 	dbt->srclist = vector_append(src, dbt->srclist, &dbt->srclistsize,
289 	    sizeof(*src));
290 	modp = vector_search(&src->name, _nsmod, _nsmodsize, sizeof(*_nsmod),
291 	    string_compare);
292 	if (modp == NULL)
293 		nss_load_module(src->name, NULL);
294 }
295 
296 
297 #ifdef _NSS_DEBUG
298 void
299 _nsdbtdump(const ns_dbt *dbt)
300 {
301 	int i;
302 
303 	printf("%s (%d source%s):", dbt->name, dbt->srclistsize,
304 	    dbt->srclistsize == 1 ? "" : "s");
305 	for (i = 0; i < (int)dbt->srclistsize; i++) {
306 		printf(" %s", dbt->srclist[i].name);
307 		if (!(dbt->srclist[i].flags &
308 		    (NS_UNAVAIL|NS_NOTFOUND|NS_TRYAGAIN)) &&
309 		    (dbt->srclist[i].flags & NS_SUCCESS))
310 			continue;
311 		printf(" [");
312 		if (!(dbt->srclist[i].flags & NS_SUCCESS))
313 			printf(" SUCCESS=continue");
314 		if (dbt->srclist[i].flags & NS_UNAVAIL)
315 			printf(" UNAVAIL=return");
316 		if (dbt->srclist[i].flags & NS_NOTFOUND)
317 			printf(" NOTFOUND=return");
318 		if (dbt->srclist[i].flags & NS_TRYAGAIN)
319 			printf(" TRYAGAIN=return");
320 		printf(" ]");
321 	}
322 	printf("\n");
323 }
324 #endif
325 
326 
327 /*
328  * The first time nsdispatch is called (during a process's lifetime,
329  * or after nsswitch.conf has been updated), nss_configure will
330  * prepare global data needed by NSS.
331  */
332 static int
333 nss_configure(void)
334 {
335 	static time_t	 confmod;
336 	struct stat	 statbuf;
337 	int		 result, isthreaded;
338 	const char	*path;
339 #ifdef NS_CACHING
340 	void		*handle;
341 #endif
342 
343 	result = 0;
344 	isthreaded = __isthreaded;
345 #if defined(_NSS_DEBUG) && defined(_NSS_SHOOT_FOOT)
346 	/* NOTE WELL:  THIS IS A SECURITY HOLE. This must only be built
347 	 * for debugging purposes and MUST NEVER be used in production.
348 	 */
349 	path = getenv("NSSWITCH_CONF");
350 	if (path == NULL)
351 #endif
352 	path = _PATH_NS_CONF;
353 	if (stat(path, &statbuf) != 0)
354 		return (0);
355 	if (statbuf.st_mtime <= confmod)
356 		return (0);
357 	if (isthreaded) {
358 	    (void)_pthread_rwlock_unlock(&nss_lock);
359 	    result = _pthread_rwlock_wrlock(&nss_lock);
360 	    if (result != 0)
361 		    return (result);
362 	    if (stat(path, &statbuf) != 0)
363 		    goto fin;
364 	    if (statbuf.st_mtime <= confmod)
365 		    goto fin;
366 	}
367 	_nsyyin = fopen(path, "re");
368 	if (_nsyyin == NULL)
369 		goto fin;
370 	VECTOR_FREE(_nsmap, &_nsmapsize, sizeof(*_nsmap),
371 	    (vector_free_elem)ns_dbt_free);
372 	VECTOR_FREE(_nsmod, &_nsmodsize, sizeof(*_nsmod),
373 	    (vector_free_elem)ns_mod_free);
374 	nss_load_builtin_modules();
375 	_nsyyparse();
376 	(void)fclose(_nsyyin);
377 	vector_sort(_nsmap, _nsmapsize, sizeof(*_nsmap), string_compare);
378 	if (confmod == 0)
379 		(void)atexit(nss_atexit);
380 	confmod = statbuf.st_mtime;
381 
382 #ifdef NS_CACHING
383 	handle = libc_dlopen(NULL, RTLD_LAZY | RTLD_GLOBAL);
384 	if (handle != NULL) {
385 		nss_cache_cycle_prevention_func = dlsym(handle,
386 			"_nss_cache_cycle_prevention_function");
387 		dlclose(handle);
388 	}
389 #endif
390 fin:
391 	if (isthreaded) {
392 	    (void)_pthread_rwlock_unlock(&nss_lock);
393 	    if (result == 0)
394 		    result = _pthread_rwlock_rdlock(&nss_lock);
395 	}
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 			(void)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 			(void)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 		(void)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 		(void)_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 		(void)_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 static void
601 fb_endstate(void *p)
602 {
603 	free(p);
604 }
605 
606 __weak_reference(_nsdispatch, nsdispatch);
607 
608 int
609 _nsdispatch(void *retval, const ns_dtab disp_tab[], const char *database,
610 	    const char *method_name, const ns_src defaults[], ...)
611 {
612 	va_list		 ap;
613 	const ns_dbt	*dbt;
614 	const ns_src	*srclist;
615 	nss_method	 method, fb_method;
616 	void		*mdata;
617 	int		 isthreaded, serrno, i, result, srclistsize;
618 	struct fb_state	*st;
619 	int		 saved_depth;
620 
621 #ifdef NS_CACHING
622 	nss_cache_data	 cache_data;
623 	nss_cache_data	*cache_data_p;
624 	int		 cache_flag;
625 #endif
626 
627 	dbt = NULL;
628 	fb_method = NULL;
629 
630 	isthreaded = __isthreaded;
631 	serrno = errno;
632 	if (isthreaded) {
633 		result = _pthread_rwlock_rdlock(&nss_lock);
634 		if (result != 0) {
635 			result = NS_UNAVAIL;
636 			goto fin;
637 		}
638 	}
639 
640 	result = fb_getstate(&st);
641 	if (result != 0) {
642 		result = NS_UNAVAIL;
643 		goto fin;
644 	}
645 
646 	result = nss_configure();
647 	if (result != 0) {
648 		result = NS_UNAVAIL;
649 		goto fin;
650 	}
651 	++st->dispatch_depth;
652 	if (st->dispatch_depth > st->fallback_depth) {
653 		dbt = vector_search(&database, _nsmap, _nsmapsize, sizeof(*_nsmap),
654 		    string_compare);
655 		fb_method = nss_method_lookup(NSSRC_FALLBACK, database,
656 		    method_name, disp_tab, &mdata);
657 	}
658 
659 	if (dbt != NULL) {
660 		srclist = dbt->srclist;
661 		srclistsize = dbt->srclistsize;
662 	} else {
663 		srclist = defaults;
664 		srclistsize = 0;
665 		while (srclist[srclistsize].name != NULL)
666 			srclistsize++;
667 	}
668 
669 #ifdef NS_CACHING
670 	cache_data_p = NULL;
671 	cache_flag = 0;
672 #endif
673 	for (i = 0; i < srclistsize; i++) {
674 		result = NS_NOTFOUND;
675 		method = nss_method_lookup(srclist[i].name, database,
676 		    method_name, disp_tab, &mdata);
677 
678 		if (method != NULL) {
679 #ifdef NS_CACHING
680 			if (strcmp(srclist[i].name, NSSRC_CACHE) == 0 &&
681 			    nss_cache_cycle_prevention_func == NULL) {
682 #ifdef NS_STRICT_LIBC_EID_CHECKING
683 				if (issetugid() != 0)
684 					continue;
685 #endif
686 				cache_flag = 1;
687 
688 				memset(&cache_data, 0, sizeof(nss_cache_data));
689 				cache_data.info = (nss_cache_info const *)mdata;
690 				cache_data_p = &cache_data;
691 
692 				va_start(ap, defaults);
693 				if (cache_data.info->id_func != NULL)
694 					result = __nss_common_cache_read(retval,
695 					    cache_data_p, ap);
696 				else if (cache_data.info->marshal_func != NULL)
697 					result = __nss_mp_cache_read(retval,
698 					    cache_data_p, ap);
699 				else
700 					result = __nss_mp_cache_end(retval,
701 					    cache_data_p, ap);
702 				va_end(ap);
703 			} else {
704 				cache_flag = 0;
705 				errno = 0;
706 				va_start(ap, defaults);
707 				result = method(retval, mdata, ap);
708 				va_end(ap);
709 			}
710 #else /* NS_CACHING */
711 			errno = 0;
712 			va_start(ap, defaults);
713 			result = method(retval, mdata, ap);
714 			va_end(ap);
715 #endif /* NS_CACHING */
716 
717 			if (result & (srclist[i].flags))
718 				break;
719 		} else {
720 			if (fb_method != NULL) {
721 				saved_depth = st->fallback_depth;
722 				st->fallback_depth = st->dispatch_depth + 1;
723 				va_start(ap, defaults);
724 				result = fb_method(retval,
725 				    (void *)srclist[i].name, ap);
726 				va_end(ap);
727 				st->fallback_depth = saved_depth;
728 			} else
729 				nss_log(LOG_DEBUG, "%s, %s, %s, not found, "
730 				    "and no fallback provided",
731 				    srclist[i].name, database, method_name);
732 		}
733 	}
734 
735 #ifdef NS_CACHING
736 	if (cache_data_p != NULL &&
737 	    (result & (NS_NOTFOUND | NS_SUCCESS)) && cache_flag == 0) {
738 		va_start(ap, defaults);
739 		if (result == NS_SUCCESS) {
740 			if (cache_data.info->id_func != NULL)
741 				__nss_common_cache_write(retval, cache_data_p,
742 				    ap);
743 			else if (cache_data.info->marshal_func != NULL)
744 				__nss_mp_cache_write(retval, cache_data_p, ap);
745 		} else if (result == NS_NOTFOUND) {
746 			if (cache_data.info->id_func == NULL) {
747 				if (cache_data.info->marshal_func != NULL)
748 					__nss_mp_cache_write_submit(retval,
749 					    cache_data_p, ap);
750 			} else
751 				__nss_common_cache_write_negative(cache_data_p);
752 		}
753 		va_end(ap);
754 	}
755 #endif /* NS_CACHING */
756 
757 	if (isthreaded)
758 		(void)_pthread_rwlock_unlock(&nss_lock);
759 	--st->dispatch_depth;
760 fin:
761 	errno = serrno;
762 	return (result);
763 }
764