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[openldap] / servers / slapd / backover.c
1 /* backover.c - backend overlay routines */
2 /* $OpenLDAP$ */
3 /* This work is part of OpenLDAP Software <http://www.openldap.org/>.
4  *
5  * Copyright 2003-2014 The OpenLDAP Foundation.
6  * All rights reserved.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted only as authorized by the OpenLDAP
10  * Public License.
11  *
12  * A copy of this license is available in the file LICENSE in the
13  * top-level directory of the distribution or, alternatively, at
14  * <http://www.OpenLDAP.org/license.html>.
15  */
16
17 /* Functions to overlay other modules over a backend. */
18
19 #include "portable.h"
20
21 #include <stdio.h>
22
23 #include <ac/string.h>
24 #include <ac/socket.h>
25
26 #define SLAPD_TOOLS
27 #include "slap.h"
28 #include "config.h"
29
30 static slap_overinst *overlays;
31
32 static int
33 over_db_config(
34         BackendDB *be,
35         const char *fname,
36         int lineno,
37         int argc,
38         char **argv
39 )
40 {
41         slap_overinfo *oi = be->bd_info->bi_private;
42         slap_overinst *on = oi->oi_list;
43         BackendInfo *bi_orig = be->bd_info;
44         struct ConfigOCs *be_cf_ocs = be->be_cf_ocs;
45         ConfigArgs ca = {0};
46         int rc = 0;
47
48         if ( oi->oi_orig->bi_db_config ) {
49                 be->bd_info = oi->oi_orig;
50                 be->be_cf_ocs = oi->oi_orig->bi_cf_ocs;
51                 rc = oi->oi_orig->bi_db_config( be, fname, lineno,
52                         argc, argv );
53
54                 if ( be->bd_info != oi->oi_orig ) {
55                         slap_overinfo   *oi2;
56                         slap_overinst   *on2, **onp;
57                         BackendDB       be2 = *be;
58                         int             i;
59
60                         /* a database added an overlay;
61                          * work it around... */
62                         assert( overlay_is_over( be ) );
63                         
64                         oi2 = ( slap_overinfo * )be->bd_info->bi_private;
65                         on2 = oi2->oi_list;
66
67                         /* need to put a uniqueness check here as well;
68                          * note that in principle there could be more than
69                          * one overlay as a result of multiple calls to
70                          * overlay_config() */
71                         be2.bd_info = (BackendInfo *)oi;
72
73                         for ( i = 0, onp = &on2; *onp; i++, onp = &(*onp)->on_next ) {
74                                 if ( overlay_is_inst( &be2, (*onp)->on_bi.bi_type ) ) {
75                                         Debug( LDAP_DEBUG_ANY, "over_db_config(): "
76                                                         "warning, freshly added "
77                                                         "overlay #%d \"%s\" is already in list\n",
78                                                         i, (*onp)->on_bi.bi_type, 0 );
79
80                                         /* NOTE: if the overlay already exists,
81                                          * there is no way to merge the results
82                                          * of the configuration that may have 
83                                          * occurred during bi_db_config(); we
84                                          * just issue a warning, and the 
85                                          * administrator should deal with this */
86                                 }
87                         }
88                         *onp = oi->oi_list;
89
90                         oi->oi_list = on2;
91
92                         ch_free( be->bd_info );
93                 }
94
95                 be->bd_info = (BackendInfo *)oi;
96                 if ( rc != SLAP_CONF_UNKNOWN ) return rc;
97         }
98
99         ca.argv = argv;
100         ca.argc = argc;
101         ca.fname = fname;
102         ca.lineno = lineno;
103         ca.be = be;
104         snprintf( ca.log, sizeof( ca.log ), "%s: line %d",
105                         ca.fname, ca.lineno );
106         ca.op = SLAP_CONFIG_ADD;
107         ca.valx = -1;
108
109         for (; on; on=on->on_next) {
110                 rc = SLAP_CONF_UNKNOWN;
111                 if (on->on_bi.bi_cf_ocs) {
112                         ConfigTable *ct;
113                         ca.bi = &on->on_bi;
114                         ct = config_find_keyword( on->on_bi.bi_cf_ocs->co_table, &ca );
115                         if ( ct ) {
116                                 ca.table = on->on_bi.bi_cf_ocs->co_type;
117                                 rc = config_add_vals( ct, &ca );
118                                 if ( rc != SLAP_CONF_UNKNOWN )
119                                         break;
120                         }
121                 }
122                 if (on->on_bi.bi_db_config && rc == SLAP_CONF_UNKNOWN) {
123                         be->bd_info = &on->on_bi;
124                         rc = on->on_bi.bi_db_config( be, fname, lineno,
125                                 argc, argv );
126                         if ( rc != SLAP_CONF_UNKNOWN ) break;
127                 }
128         }
129         be->bd_info = bi_orig;
130         be->be_cf_ocs = be_cf_ocs;
131         
132         return rc;
133 }
134
135 static int
136 over_db_open(
137         BackendDB *be,
138         ConfigReply *cr
139 )
140 {
141         slap_overinfo *oi = be->bd_info->bi_private;
142         slap_overinst *on = oi->oi_list;
143         BackendDB db = *be;
144         int rc = 0;
145
146         db.be_flags |= SLAP_DBFLAG_OVERLAY;
147         db.bd_info = oi->oi_orig;
148         if ( db.bd_info->bi_db_open ) {
149                 rc = db.bd_info->bi_db_open( &db, cr );
150         }
151
152         for (; on && rc == 0; on=on->on_next) {
153                 if ( on->on_bi.bi_flags & SLAPO_BFLAG_DISABLED )
154                         continue;
155                 db.bd_info = &on->on_bi;
156                 if ( db.bd_info->bi_db_open ) {
157                         rc = db.bd_info->bi_db_open( &db, cr );
158                 }
159         }
160
161         return rc;
162 }
163
164 static int
165 over_db_close(
166         BackendDB *be,
167         ConfigReply *cr
168 )
169 {
170         slap_overinfo *oi = be->bd_info->bi_private;
171         slap_overinst *on = oi->oi_list;
172         BackendInfo *bi_orig = be->bd_info;
173         int rc = 0;
174
175         for (; on && rc == 0; on=on->on_next) {
176                 if ( on->on_bi.bi_flags & SLAPO_BFLAG_DISABLED )
177                         continue;
178                 be->bd_info = &on->on_bi;
179                 if ( be->bd_info->bi_db_close ) {
180                         rc = be->bd_info->bi_db_close( be, cr );
181                 }
182         }
183
184         if ( oi->oi_orig->bi_db_close ) {
185                 be->bd_info = oi->oi_orig;
186                 rc = be->bd_info->bi_db_close( be, cr );
187         }
188
189         be->bd_info = bi_orig;
190         return rc;
191 }
192
193 static int
194 over_db_destroy(
195         BackendDB *be,
196         ConfigReply *cr
197 )
198 {
199         slap_overinfo *oi = be->bd_info->bi_private;
200         slap_overinst *on = oi->oi_list, *next;
201         BackendInfo *bi_orig = be->bd_info;
202         int rc = 0;
203
204         be->bd_info = oi->oi_orig;
205         if ( be->bd_info->bi_db_destroy ) {
206                 rc = be->bd_info->bi_db_destroy( be, cr );
207         }
208
209         for (; on && rc == 0; on=on->on_next) {
210                 if ( on->on_bi.bi_flags & SLAPO_BFLAG_DISABLED )
211                         continue;
212                 be->bd_info = &on->on_bi;
213                 if ( be->bd_info->bi_db_destroy ) {
214                         rc = be->bd_info->bi_db_destroy( be, cr );
215                 }
216         }
217
218         on = oi->oi_list;
219         if ( on ) {
220                 for (next = on->on_next; on; on=next) {
221                         next = on->on_next;
222                         free( on );
223                 }
224         }
225         be->bd_info = bi_orig;
226         free( oi );
227         return rc;
228 }
229
230 static int
231 over_back_response ( Operation *op, SlapReply *rs )
232 {
233         slap_overinfo *oi = op->o_callback->sc_private;
234         slap_overinst *on = oi->oi_list;
235         int rc = SLAP_CB_CONTINUE;
236         BackendDB *be = op->o_bd, db = *op->o_bd;
237
238         db.be_flags |= SLAP_DBFLAG_OVERLAY;
239         op->o_bd = &db;
240         for (; on; on=on->on_next ) {
241                 if ( on->on_bi.bi_flags & SLAPO_BFLAG_DISABLED )
242                         continue;
243                 if ( on->on_response ) {
244                         db.bd_info = (BackendInfo *)on;
245                         rc = on->on_response( op, rs );
246                         if ( rc != SLAP_CB_CONTINUE ) break;
247                 }
248         }
249         /* Bypass the remaining on_response layers, but allow
250          * normal execution to continue.
251          */
252         if ( rc == SLAP_CB_BYPASS )
253                 rc = SLAP_CB_CONTINUE;
254         op->o_bd = be;
255         return rc;
256 }
257
258 static int
259 over_access_allowed(
260         Operation               *op,
261         Entry                   *e,
262         AttributeDescription    *desc,
263         struct berval           *val,
264         slap_access_t           access,
265         AccessControlState      *state,
266         slap_mask_t             *maskp )
267 {
268         slap_overinfo *oi;
269         slap_overinst *on;
270         BackendInfo *bi;
271         BackendDB *be = op->o_bd, db;
272         int rc = SLAP_CB_CONTINUE;
273
274         /* FIXME: used to happen for instance during abandon
275          * when global overlays are used... */
276         assert( op->o_bd != NULL );
277
278         bi = op->o_bd->bd_info;
279         /* Were we invoked on the frontend? */
280         if ( !bi->bi_access_allowed ) {
281                 oi = frontendDB->bd_info->bi_private;
282         } else {
283                 oi = op->o_bd->bd_info->bi_private;
284         }
285         on = oi->oi_list;
286
287         for ( ; on; on = on->on_next ) {
288                 if ( on->on_bi.bi_flags & SLAPO_BFLAG_DISABLED )
289                         continue;
290                 if ( on->on_bi.bi_access_allowed ) {
291                         /* NOTE: do not copy the structure until required */
292                         if ( !SLAP_ISOVERLAY( op->o_bd ) ) {
293                                 db = *op->o_bd;
294                                 db.be_flags |= SLAP_DBFLAG_OVERLAY;
295                                 op->o_bd = &db;
296                         }
297
298                         op->o_bd->bd_info = (BackendInfo *)on;
299                         rc = on->on_bi.bi_access_allowed( op, e,
300                                 desc, val, access, state, maskp );
301                         if ( rc != SLAP_CB_CONTINUE ) break;
302                 }
303         }
304
305         if ( rc == SLAP_CB_CONTINUE ) {
306                 BI_access_allowed       *bi_access_allowed;
307
308                 /* if the database structure was changed, o_bd points to a
309                  * copy of the structure; put the original bd_info in place */
310                 if ( SLAP_ISOVERLAY( op->o_bd ) ) {
311                         op->o_bd->bd_info = oi->oi_orig;
312                 }
313
314                 if ( oi->oi_orig->bi_access_allowed ) {
315                         bi_access_allowed = oi->oi_orig->bi_access_allowed;
316                 } else {
317                         bi_access_allowed = slap_access_allowed;
318                 }
319
320                 rc = bi_access_allowed( op, e,
321                         desc, val, access, state, maskp );
322         }
323         /* should not fall thru this far without anything happening... */
324         if ( rc == SLAP_CB_CONTINUE ) {
325                 /* access not allowed */
326                 rc = 0;
327         }
328
329         op->o_bd = be;
330         op->o_bd->bd_info = bi;
331
332         return rc;
333 }
334
335 int
336 overlay_entry_get_ov(
337         Operation               *op,
338         struct berval   *dn,
339         ObjectClass             *oc,
340         AttributeDescription    *ad,
341         int     rw,
342         Entry   **e,
343         slap_overinst *on )
344 {
345         slap_overinfo *oi = on->on_info;
346         BackendDB *be = op->o_bd, db;
347         BackendInfo *bi = op->o_bd->bd_info;
348         int rc = SLAP_CB_CONTINUE;
349
350         for ( ; on; on = on->on_next ) {
351                 if ( on->on_bi.bi_flags & SLAPO_BFLAG_DISABLED )
352                         continue;
353                 if ( on->on_bi.bi_entry_get_rw ) {
354                         /* NOTE: do not copy the structure until required */
355                         if ( !SLAP_ISOVERLAY( op->o_bd ) ) {
356                                 db = *op->o_bd;
357                                 db.be_flags |= SLAP_DBFLAG_OVERLAY;
358                                 op->o_bd = &db;
359                         }
360
361                         op->o_bd->bd_info = (BackendInfo *)on;
362                         rc = on->on_bi.bi_entry_get_rw( op, dn,
363                                 oc, ad, rw, e );
364                         if ( rc != SLAP_CB_CONTINUE ) break;
365                 }
366         }
367
368         if ( rc == SLAP_CB_CONTINUE ) {
369                 /* if the database structure was changed, o_bd points to a
370                  * copy of the structure; put the original bd_info in place */
371                 if ( SLAP_ISOVERLAY( op->o_bd ) ) {
372                         op->o_bd->bd_info = oi->oi_orig;
373                 }
374
375                 if ( oi->oi_orig->bi_entry_get_rw ) {
376                         rc = oi->oi_orig->bi_entry_get_rw( op, dn,
377                                 oc, ad, rw, e );
378                 }
379         }
380         /* should not fall thru this far without anything happening... */
381         if ( rc == SLAP_CB_CONTINUE ) {
382                 rc = LDAP_UNWILLING_TO_PERFORM;
383         }
384
385         op->o_bd = be;
386         op->o_bd->bd_info = bi;
387
388         return rc;
389 }
390
391 static int
392 over_entry_get_rw(
393         Operation               *op,
394         struct berval   *dn,
395         ObjectClass             *oc,
396         AttributeDescription    *ad,
397         int     rw,
398         Entry   **e )
399 {
400         slap_overinfo *oi;
401         slap_overinst *on;
402
403         assert( op->o_bd != NULL );
404
405         oi = op->o_bd->bd_info->bi_private;
406         on = oi->oi_list;
407
408         return overlay_entry_get_ov( op, dn, oc, ad, rw, e, on );
409 }
410
411 int
412 overlay_entry_release_ov(
413         Operation       *op,
414         Entry   *e,
415         int rw,
416         slap_overinst *on )
417 {
418         slap_overinfo *oi = on->on_info;
419         BackendDB *be = op->o_bd, db;
420         BackendInfo *bi = op->o_bd->bd_info;
421         int rc = SLAP_CB_CONTINUE;
422
423         for ( ; on; on = on->on_next ) {
424                 if ( on->on_bi.bi_flags & SLAPO_BFLAG_DISABLED )
425                         continue;
426                 if ( on->on_bi.bi_entry_release_rw ) {
427                         /* NOTE: do not copy the structure until required */
428                         if ( !SLAP_ISOVERLAY( op->o_bd ) ) {
429                                 db = *op->o_bd;
430                                 db.be_flags |= SLAP_DBFLAG_OVERLAY;
431                                 op->o_bd = &db;
432                         }
433
434                         op->o_bd->bd_info = (BackendInfo *)on;
435                         rc = on->on_bi.bi_entry_release_rw( op, e, rw );
436                         if ( rc != SLAP_CB_CONTINUE ) break;
437                 }
438         }
439
440         if ( rc == SLAP_CB_CONTINUE ) {
441                 /* if the database structure was changed, o_bd points to a
442                  * copy of the structure; put the original bd_info in place */
443                 if ( SLAP_ISOVERLAY( op->o_bd ) ) {
444                         op->o_bd->bd_info = oi->oi_orig;
445                 }
446
447                 if ( oi->oi_orig->bi_entry_release_rw ) {
448                         rc = oi->oi_orig->bi_entry_release_rw( op, e, rw );
449                 }
450         }
451         /* should not fall thru this far without anything happening... */
452         if ( rc == SLAP_CB_CONTINUE ) {
453                 entry_free( e );
454                 rc = 0;
455         }
456
457         op->o_bd = be;
458         op->o_bd->bd_info = bi;
459
460         return rc;
461 }
462
463 static int
464 over_entry_release_rw(
465         Operation       *op,
466         Entry   *e,
467         int rw )
468 {
469         slap_overinfo *oi;
470         slap_overinst *on;
471
472         assert( op->o_bd != NULL );
473
474         oi = op->o_bd->bd_info->bi_private;
475         on = oi->oi_list;
476
477         return overlay_entry_release_ov( op, e, rw, on );
478 }
479
480 static int
481 over_acl_group(
482         Operation               *op,
483         Entry                   *e,
484         struct berval           *gr_ndn,
485         struct berval           *op_ndn,
486         ObjectClass             *group_oc,
487         AttributeDescription    *group_at )
488 {
489         slap_overinfo *oi;
490         slap_overinst *on;
491         BackendInfo *bi;
492         BackendDB *be = op->o_bd, db;
493         int rc = SLAP_CB_CONTINUE;
494
495         /* FIXME: used to happen for instance during abandon
496          * when global overlays are used... */
497         assert( be != NULL );
498
499         bi = be->bd_info;
500         oi = bi->bi_private;
501         on = oi->oi_list;
502
503         for ( ; on; on = on->on_next ) {
504                 if ( on->on_bi.bi_flags & SLAPO_BFLAG_DISABLED )
505                         continue;
506                 if ( on->on_bi.bi_acl_group ) {
507                         /* NOTE: do not copy the structure until required */
508                         if ( !SLAP_ISOVERLAY( op->o_bd ) ) {
509                                 db = *op->o_bd;
510                                 db.be_flags |= SLAP_DBFLAG_OVERLAY;
511                                 op->o_bd = &db;
512                         }
513
514                         op->o_bd->bd_info = (BackendInfo *)on;
515                         rc = on->on_bi.bi_acl_group( op, e,
516                                 gr_ndn, op_ndn, group_oc, group_at );
517                         if ( rc != SLAP_CB_CONTINUE ) break;
518                 }
519         }
520
521         if ( rc == SLAP_CB_CONTINUE ) {
522                 BI_acl_group            *bi_acl_group;
523
524                 /* if the database structure was changed, o_bd points to a
525                  * copy of the structure; put the original bd_info in place */
526                 if ( SLAP_ISOVERLAY( op->o_bd ) ) {
527                         op->o_bd->bd_info = oi->oi_orig;
528                 }
529
530                 if ( oi->oi_orig->bi_acl_group ) {
531                         bi_acl_group = oi->oi_orig->bi_acl_group;
532                 } else {
533                         bi_acl_group = backend_group;
534                 }
535
536                 rc = bi_acl_group( op, e,
537                         gr_ndn, op_ndn, group_oc, group_at );
538         }
539         /* should not fall thru this far without anything happening... */
540         if ( rc == SLAP_CB_CONTINUE ) {
541                 /* access not allowed */
542                 rc = 0;
543         }
544
545         op->o_bd = be;
546         op->o_bd->bd_info = bi;
547
548         return rc;
549 }
550
551 static int
552 over_acl_attribute(
553         Operation               *op,
554         Entry                   *target,
555         struct berval           *entry_ndn,
556         AttributeDescription    *entry_at,
557         BerVarray               *vals,
558         slap_access_t           access )
559 {
560         slap_overinfo *oi;
561         slap_overinst *on;
562         BackendInfo *bi;
563         BackendDB *be = op->o_bd, db;
564         int rc = SLAP_CB_CONTINUE;
565
566         /* FIXME: used to happen for instance during abandon
567          * when global overlays are used... */
568         assert( be != NULL );
569
570         bi = be->bd_info;
571         oi = bi->bi_private;
572         on = oi->oi_list;
573
574         for ( ; on; on = on->on_next ) {
575                 if ( on->on_bi.bi_flags & SLAPO_BFLAG_DISABLED )
576                         continue;
577                 if ( on->on_bi.bi_acl_attribute ) {
578                         /* NOTE: do not copy the structure until required */
579                         if ( !SLAP_ISOVERLAY( op->o_bd ) ) {
580                                 db = *op->o_bd;
581                                 db.be_flags |= SLAP_DBFLAG_OVERLAY;
582                                 op->o_bd = &db;
583                         }
584
585                         op->o_bd->bd_info = (BackendInfo *)on;
586                         rc = on->on_bi.bi_acl_attribute( op, target,
587                                 entry_ndn, entry_at, vals, access );
588                         if ( rc != SLAP_CB_CONTINUE ) break;
589                 }
590         }
591
592         if ( rc == SLAP_CB_CONTINUE ) {
593                 BI_acl_attribute                *bi_acl_attribute;
594
595                 /* if the database structure was changed, o_bd points to a
596                  * copy of the structure; put the original bd_info in place */
597                 if ( SLAP_ISOVERLAY( op->o_bd ) ) {
598                         op->o_bd->bd_info = oi->oi_orig;
599                 }
600
601                 if ( oi->oi_orig->bi_acl_attribute ) {
602                         bi_acl_attribute = oi->oi_orig->bi_acl_attribute;
603                 } else {
604                         bi_acl_attribute = backend_attribute;
605                 }
606
607                 rc = bi_acl_attribute( op, target,
608                         entry_ndn, entry_at, vals, access );
609         }
610         /* should not fall thru this far without anything happening... */
611         if ( rc == SLAP_CB_CONTINUE ) {
612                 /* access not allowed */
613                 rc = 0;
614         }
615
616         op->o_bd = be;
617         op->o_bd->bd_info = bi;
618
619         return rc;
620 }
621
622 int
623 overlay_callback_after_backover( Operation *op, slap_callback *sc, int append )
624 {
625         slap_callback **scp;
626
627         for ( scp = &op->o_callback; *scp != NULL; scp = &(*scp)->sc_next ) {
628                 if ( (*scp)->sc_response == over_back_response ) {
629                         sc->sc_next = (*scp)->sc_next;
630                         (*scp)->sc_next = sc;
631                         return 0;
632                 }
633         }
634
635         if ( append ) {
636                 *scp = sc;
637                 return 0;
638         }
639
640         return 1;
641 }
642
643 /*
644  * default return code in case of missing backend function
645  * and overlay stack returning SLAP_CB_CONTINUE
646  */
647 static int op_rc[ op_last ] = {
648         LDAP_UNWILLING_TO_PERFORM,      /* bind */
649         LDAP_UNWILLING_TO_PERFORM,      /* unbind */
650         LDAP_UNWILLING_TO_PERFORM,      /* search */
651         SLAP_CB_CONTINUE,               /* compare; pass to frontend */
652         LDAP_UNWILLING_TO_PERFORM,      /* modify */
653         LDAP_UNWILLING_TO_PERFORM,      /* modrdn */
654         LDAP_UNWILLING_TO_PERFORM,      /* add */
655         LDAP_UNWILLING_TO_PERFORM,      /* delete */
656         LDAP_UNWILLING_TO_PERFORM,      /* abandon */
657         LDAP_UNWILLING_TO_PERFORM,      /* cancel */
658         LDAP_UNWILLING_TO_PERFORM,      /* extended */
659         LDAP_SUCCESS,                   /* aux_operational */
660         LDAP_SUCCESS,                   /* aux_chk_referrals */
661         SLAP_CB_CONTINUE                /* aux_chk_controls; pass to frontend */
662 };
663
664 int overlay_op_walk(
665         Operation *op,
666         SlapReply *rs,
667         slap_operation_t which,
668         slap_overinfo *oi,
669         slap_overinst *on
670 )
671 {
672         BackendInfo *bi;
673         int rc = SLAP_CB_CONTINUE;
674
675         for (; on; on=on->on_next ) {
676                 if ( on->on_bi.bi_flags & SLAPO_BFLAG_DISABLED )
677                         continue;
678                 bi = &on->on_bi;
679                 if ( (&bi->bi_op_bind)[ which ] ) {
680                         op->o_bd->bd_info = (BackendInfo *)on;
681                         rc = (&bi->bi_op_bind)[ which ]( op, rs );
682                         if ( rc != SLAP_CB_CONTINUE ) break;
683                 }
684         }
685         if ( rc == SLAP_CB_BYPASS )
686                 rc = SLAP_CB_CONTINUE;
687
688         bi = oi->oi_orig;
689         if ( (&bi->bi_op_bind)[ which ] && rc == SLAP_CB_CONTINUE ) {
690                 op->o_bd->bd_info = bi;
691                 rc = (&bi->bi_op_bind)[ which ]( op, rs );
692         }
693         /* should not fall thru this far without anything happening... */
694         if ( rc == SLAP_CB_CONTINUE ) {
695                 rc = op_rc[ which ];
696         }
697
698         /* The underlying backend didn't handle the request, make sure
699          * overlay cleanup is processed.
700          */
701         if ( rc == LDAP_UNWILLING_TO_PERFORM ) {
702                 slap_callback *sc_next;
703                 for ( ; op->o_callback && op->o_callback->sc_response !=
704                         over_back_response; op->o_callback = sc_next ) {
705                         sc_next = op->o_callback->sc_next;
706                         if ( op->o_callback->sc_cleanup ) {
707                                 op->o_callback->sc_cleanup( op, rs );
708                         }
709                 }
710         }
711         return rc;
712 }
713
714 static int
715 over_op_func(
716         Operation *op,
717         SlapReply *rs,
718         slap_operation_t which
719 )
720 {
721         slap_overinfo *oi;
722         slap_overinst *on;
723         BackendDB *be = op->o_bd, db;
724         slap_callback cb = {NULL, over_back_response, NULL, NULL}, **sc;
725         int rc = SLAP_CB_CONTINUE;
726
727         /* FIXME: used to happen for instance during abandon
728          * when global overlays are used... */
729         assert( op->o_bd != NULL );
730
731         oi = op->o_bd->bd_info->bi_private;
732         on = oi->oi_list;
733
734         if ( !SLAP_ISOVERLAY( op->o_bd )) {
735                 db = *op->o_bd;
736                 db.be_flags |= SLAP_DBFLAG_OVERLAY;
737                 op->o_bd = &db;
738         }
739         cb.sc_next = op->o_callback;
740         cb.sc_private = oi;
741         op->o_callback = &cb;
742
743         rc = overlay_op_walk( op, rs, which, oi, on );
744         for ( sc = &op->o_callback; *sc; sc = &(*sc)->sc_next ) {
745                 if ( *sc == &cb ) {
746                         *sc = cb.sc_next;
747                         break;
748                 }
749         }
750
751         op->o_bd = be;
752         return rc;
753 }
754
755 static int
756 over_op_bind( Operation *op, SlapReply *rs )
757 {
758         return over_op_func( op, rs, op_bind );
759 }
760
761 static int
762 over_op_unbind( Operation *op, SlapReply *rs )
763 {
764         return over_op_func( op, rs, op_unbind );
765 }
766
767 static int
768 over_op_search( Operation *op, SlapReply *rs )
769 {
770         return over_op_func( op, rs, op_search );
771 }
772
773 static int
774 over_op_compare( Operation *op, SlapReply *rs )
775 {
776         return over_op_func( op, rs, op_compare );
777 }
778
779 static int
780 over_op_modify( Operation *op, SlapReply *rs )
781 {
782         return over_op_func( op, rs, op_modify );
783 }
784
785 static int
786 over_op_modrdn( Operation *op, SlapReply *rs )
787 {
788         return over_op_func( op, rs, op_modrdn );
789 }
790
791 static int
792 over_op_add( Operation *op, SlapReply *rs )
793 {
794         return over_op_func( op, rs, op_add );
795 }
796
797 static int
798 over_op_delete( Operation *op, SlapReply *rs )
799 {
800         return over_op_func( op, rs, op_delete );
801 }
802
803 static int
804 over_op_abandon( Operation *op, SlapReply *rs )
805 {
806         return over_op_func( op, rs, op_abandon );
807 }
808
809 static int
810 over_op_cancel( Operation *op, SlapReply *rs )
811 {
812         return over_op_func( op, rs, op_cancel );
813 }
814
815 static int
816 over_op_extended( Operation *op, SlapReply *rs )
817 {
818         return over_op_func( op, rs, op_extended );
819 }
820
821 static int
822 over_aux_operational( Operation *op, SlapReply *rs )
823 {
824         return over_op_func( op, rs, op_aux_operational );
825 }
826
827 static int
828 over_aux_chk_referrals( Operation *op, SlapReply *rs )
829 {
830         return over_op_func( op, rs, op_aux_chk_referrals );
831 }
832
833 static int
834 over_aux_chk_controls( Operation *op, SlapReply *rs )
835 {
836         return over_op_func( op, rs, op_aux_chk_controls );
837 }
838
839 enum conn_which {
840         conn_init = 0,
841         conn_destroy,
842         conn_last
843 };
844
845 static int
846 over_connection_func(
847         BackendDB       *bd,
848         Connection      *conn,
849         enum conn_which which
850 )
851 {
852         slap_overinfo           *oi;
853         slap_overinst           *on;
854         BackendDB               db;
855         int                     rc = SLAP_CB_CONTINUE;
856         BI_connection_init      **func;
857
858         /* FIXME: used to happen for instance during abandon
859          * when global overlays are used... */
860         assert( bd != NULL );
861
862         oi = bd->bd_info->bi_private;
863         on = oi->oi_list;
864
865         if ( !SLAP_ISOVERLAY( bd ) ) {
866                 db = *bd;
867                 db.be_flags |= SLAP_DBFLAG_OVERLAY;
868                 bd = &db;
869         }
870
871         for ( ; on; on = on->on_next ) {
872                 if ( on->on_bi.bi_flags & SLAPO_BFLAG_DISABLED )
873                         continue;
874                 func = &on->on_bi.bi_connection_init;
875                 if ( func[ which ] ) {
876                         bd->bd_info = (BackendInfo *)on;
877                         rc = func[ which ]( bd, conn );
878                         if ( rc != SLAP_CB_CONTINUE ) break;
879                 }
880         }
881
882         func = &oi->oi_orig->bi_connection_init;
883         if ( func[ which ] && rc == SLAP_CB_CONTINUE ) {
884                 bd->bd_info = oi->oi_orig;
885                 rc = func[ which ]( bd, conn );
886         }
887         /* should not fall thru this far without anything happening... */
888         if ( rc == SLAP_CB_CONTINUE ) {
889                 rc = LDAP_UNWILLING_TO_PERFORM;
890         }
891
892         return rc;
893 }
894
895 static int
896 over_connection_init(
897         BackendDB       *bd,
898         Connection      *conn
899 )
900 {
901         return over_connection_func( bd, conn, conn_init );
902 }
903
904 static int
905 over_connection_destroy(
906         BackendDB       *bd,
907         Connection      *conn
908 )
909 {
910         return over_connection_func( bd, conn, conn_destroy );
911 }
912
913 int
914 overlay_register(
915         slap_overinst *on
916 )
917 {
918         slap_overinst   *tmp;
919
920         /* FIXME: check for duplicates? */
921         for ( tmp = overlays; tmp != NULL; tmp = tmp->on_next ) {
922                 if ( strcmp( on->on_bi.bi_type, tmp->on_bi.bi_type ) == 0 ) {
923                         Debug( LDAP_DEBUG_ANY,
924                                 "overlay_register(\"%s\"): "
925                                 "name already in use.\n",
926                                 on->on_bi.bi_type, 0, 0 );
927                         return -1;
928                 }
929
930                 if ( on->on_bi.bi_obsolete_names != NULL ) {
931                         int     i;
932
933                         for ( i = 0; on->on_bi.bi_obsolete_names[ i ] != NULL; i++ ) {
934                                 if ( strcmp( on->on_bi.bi_obsolete_names[ i ], tmp->on_bi.bi_type ) == 0 ) {
935                                         Debug( LDAP_DEBUG_ANY,
936                                                 "overlay_register(\"%s\"): "
937                                                 "obsolete name \"%s\" already in use "
938                                                 "by overlay \"%s\".\n",
939                                                 on->on_bi.bi_type,
940                                                 on->on_bi.bi_obsolete_names[ i ],
941                                                 tmp->on_bi.bi_type );
942                                         return -1;
943                                 }
944                         }
945                 }
946
947                 if ( tmp->on_bi.bi_obsolete_names != NULL ) {
948                         int     i;
949
950                         for ( i = 0; tmp->on_bi.bi_obsolete_names[ i ] != NULL; i++ ) {
951                                 int     j;
952
953                                 if ( strcmp( on->on_bi.bi_type, tmp->on_bi.bi_obsolete_names[ i ] ) == 0 ) {
954                                         Debug( LDAP_DEBUG_ANY,
955                                                 "overlay_register(\"%s\"): "
956                                                 "name already in use "
957                                                 "as obsolete by overlay \"%s\".\n",
958                                                 on->on_bi.bi_type,
959                                                 tmp->on_bi.bi_obsolete_names[ i ], 0 );
960                                         return -1;
961                                 }
962
963                                 if ( on->on_bi.bi_obsolete_names != NULL ) {
964                                         for ( j = 0; on->on_bi.bi_obsolete_names[ j ] != NULL; j++ ) {
965                                                 if ( strcmp( on->on_bi.bi_obsolete_names[ j ], tmp->on_bi.bi_obsolete_names[ i ] ) == 0 ) {
966                                                         Debug( LDAP_DEBUG_ANY,
967                                                                 "overlay_register(\"%s\"): "
968                                                                 "obsolete name \"%s\" already in use "
969                                                                 "as obsolete by overlay \"%s\".\n",
970                                                                 on->on_bi.bi_type,
971                                                                 on->on_bi.bi_obsolete_names[ j ],
972                                                                 tmp->on_bi.bi_type );
973                                                         return -1;
974                                                 }
975                                         }
976                                 }
977                         }
978                 }
979         }
980
981         on->on_next = overlays;
982         overlays = on;
983         return 0;
984 }
985
986 /*
987  * iterator on registered overlays; overlay_next( NULL ) returns the first
988  * overlay; subsequent calls with the previously returned value allow to 
989  * iterate over the entire list; returns NULL when no more overlays are 
990  * registered.
991  */
992
993 slap_overinst *
994 overlay_next(
995         slap_overinst *on
996 )
997 {
998         if ( on == NULL ) {
999                 return overlays;
1000         }
1001
1002         return on->on_next;
1003 }
1004
1005 /*
1006  * returns a specific registered overlay based on the type; NULL if not
1007  * registered.
1008  */
1009
1010 slap_overinst *
1011 overlay_find( const char *over_type )
1012 {
1013         slap_overinst *on = overlays;
1014
1015         assert( over_type != NULL );
1016
1017         for ( ; on; on = on->on_next ) {
1018                 if ( strcmp( on->on_bi.bi_type, over_type ) == 0 ) {
1019                         goto foundit;
1020                 }
1021
1022                 if ( on->on_bi.bi_obsolete_names != NULL ) {
1023                         int     i;
1024
1025                         for ( i = 0; on->on_bi.bi_obsolete_names[ i ] != NULL; i++ ) {
1026                                 if ( strcmp( on->on_bi.bi_obsolete_names[ i ], over_type ) == 0 ) {
1027                                         Debug( LDAP_DEBUG_ANY,
1028                                                 "overlay_find(\"%s\"): "
1029                                                 "obsolete name for \"%s\".\n",
1030                                                 on->on_bi.bi_obsolete_names[ i ],
1031                                                 on->on_bi.bi_type, 0 );
1032                                         goto foundit;
1033                                 }
1034                         }
1035                 }
1036         }
1037
1038 foundit:;
1039         return on;
1040 }
1041
1042 static const char overtype[] = "over";
1043
1044 /*
1045  * returns TRUE (1) if the database is actually an overlay instance;
1046  * FALSE (0) otherwise.
1047  */
1048
1049 int
1050 overlay_is_over( BackendDB *be )
1051 {
1052         return be->bd_info->bi_type == overtype;
1053 }
1054
1055 /*
1056  * returns TRUE (1) if the given database is actually an overlay
1057  * instance and, somewhere in the list, contains the requested overlay;
1058  * FALSE (0) otherwise.
1059  */
1060
1061 int
1062 overlay_is_inst( BackendDB *be, const char *over_type )
1063 {
1064         slap_overinst   *on;
1065
1066         assert( be != NULL );
1067
1068         if ( !overlay_is_over( be ) ) {
1069                 return 0;
1070         }
1071         
1072         on = ((slap_overinfo *)be->bd_info->bi_private)->oi_list;
1073         for ( ; on; on = on->on_next ) {
1074                 if ( strcmp( on->on_bi.bi_type, over_type ) == 0 ) {
1075                         return 1;
1076                 }
1077         }
1078
1079         return 0;
1080 }
1081
1082 int
1083 overlay_register_control( BackendDB *be, const char *oid )
1084 {
1085         int             gotit = 0;
1086         int             cid;
1087
1088         if ( slap_find_control_id( oid, &cid ) == LDAP_CONTROL_NOT_FOUND ) {
1089                 return -1;
1090         }
1091
1092         if ( SLAP_ISGLOBALOVERLAY( be ) ) {
1093                 BackendDB *bd;
1094                 
1095                 /* add to all backends... */
1096                 LDAP_STAILQ_FOREACH( bd, &backendDB, be_next ) {
1097                         if ( bd == be->bd_self ) {
1098                                 gotit = 1;
1099                         }
1100
1101                         /* overlays can be instanciated multiple times, use
1102                          * be_ctrls[ cid ] as an instance counter, so that the
1103                          * overlay's controls are only really disabled after the
1104                          * last instance called overlay_register_control() */
1105                         bd->be_ctrls[ cid ]++;
1106                         bd->be_ctrls[ SLAP_MAX_CIDS ] = 1;
1107                 }
1108
1109         }
1110         
1111         if ( !gotit ) {
1112                 /* overlays can be instanciated multiple times, use
1113                  * be_ctrls[ cid ] as an instance counter, so that the
1114                  * overlay's controls are only really unregistered after the
1115                  * last instance called overlay_register_control() */
1116                 be->bd_self->be_ctrls[ cid ]++;
1117                 be->bd_self->be_ctrls[ SLAP_MAX_CIDS ] = 1;
1118         }
1119
1120         return 0;
1121 }
1122
1123 #ifdef SLAP_CONFIG_DELETE
1124 void
1125 overlay_unregister_control( BackendDB *be, const char *oid )
1126 {
1127         int             gotit = 0;
1128         int             cid;
1129
1130         if ( slap_find_control_id( oid, &cid ) == LDAP_CONTROL_NOT_FOUND ) {
1131                 return;
1132         }
1133
1134         if ( SLAP_ISGLOBALOVERLAY( be ) ) {
1135                 BackendDB *bd;
1136
1137                 /* remove from all backends... */
1138                 LDAP_STAILQ_FOREACH( bd, &backendDB, be_next ) {
1139                         if ( bd == be->bd_self ) {
1140                                 gotit = 1;
1141                         }
1142
1143                         bd->be_ctrls[ cid ]--;
1144                 }
1145         }
1146
1147         if ( !gotit ) {
1148                 be->bd_self->be_ctrls[ cid ]--;
1149         }
1150 }
1151 #endif /* SLAP_CONFIG_DELETE */
1152
1153 void
1154 overlay_destroy_one( BackendDB *be, slap_overinst *on )
1155 {
1156         slap_overinfo *oi = on->on_info;
1157         slap_overinst **oidx;
1158
1159         for ( oidx = &oi->oi_list; *oidx; oidx = &(*oidx)->on_next ) {
1160                 if ( *oidx == on ) {
1161                         *oidx = on->on_next;
1162                         if ( on->on_bi.bi_db_destroy ) {
1163                                 BackendInfo *bi_orig = be->bd_info;
1164                                 be->bd_info = (BackendInfo *)on;
1165                                 on->on_bi.bi_db_destroy( be, NULL );
1166                                 be->bd_info = bi_orig;
1167                         }
1168                         free( on );
1169                         break;
1170                 }
1171         }
1172 }
1173
1174 #ifdef SLAP_CONFIG_DELETE
1175 typedef struct ov_remove_ctx {
1176         BackendDB *be;
1177         slap_overinst *on;
1178 } ov_remove_ctx;
1179
1180 int
1181 overlay_remove_cb( Operation *op, SlapReply *rs )
1182 {
1183         ov_remove_ctx *rm_ctx = (ov_remove_ctx*) op->o_callback->sc_private;
1184         BackendInfo *bi_orig = rm_ctx->be->bd_info;
1185
1186         rm_ctx->be->bd_info = (BackendInfo*) rm_ctx->on;
1187
1188         if ( rm_ctx->on->on_bi.bi_db_close ) {
1189                 rm_ctx->on->on_bi.bi_db_close( rm_ctx->be, NULL );
1190         }
1191         if ( rm_ctx->on->on_bi.bi_db_destroy ) {
1192                 rm_ctx->on->on_bi.bi_db_destroy( rm_ctx->be, NULL );
1193         }
1194
1195         /* clean up after removing last overlay */
1196         if ( ! rm_ctx->on->on_info->oi_list ) {
1197                 /* reset db flags and bd_info to orig */
1198                 SLAP_DBFLAGS( rm_ctx->be ) &= ~SLAP_DBFLAG_GLOBAL_OVERLAY;
1199                 rm_ctx->be->bd_info = rm_ctx->on->on_info->oi_orig;
1200                 ch_free(rm_ctx->on->on_info);
1201         } else {
1202                 rm_ctx->be->bd_info = bi_orig;
1203         }
1204         free( rm_ctx->on );
1205         op->o_tmpfree(rm_ctx, op->o_tmpmemctx);
1206         return SLAP_CB_CONTINUE;
1207 }
1208
1209 void
1210 overlay_remove( BackendDB *be, slap_overinst *on, Operation *op )
1211 {
1212         slap_overinfo *oi = on->on_info;
1213         slap_overinst **oidx;
1214         ov_remove_ctx *rm_ctx;
1215         slap_callback *rm_cb, *cb;
1216
1217         /* remove overlay from oi_list */
1218         for ( oidx = &oi->oi_list; *oidx; oidx = &(*oidx)->on_next ) {
1219                 if ( *oidx == on ) {
1220                         *oidx = on->on_next;
1221                         break;
1222                 }
1223         }
1224
1225         /* The db_close and db_destroy handlers to cleanup a release
1226          * the overlay's resources are called from the cleanup callback
1227          */
1228         rm_ctx = op->o_tmpalloc( sizeof( ov_remove_ctx ), op->o_tmpmemctx );
1229         rm_ctx->be = be;
1230         rm_ctx->on = on;
1231
1232         rm_cb = op->o_tmpalloc( sizeof( slap_callback ), op->o_tmpmemctx );
1233         rm_cb->sc_next = NULL;
1234         rm_cb->sc_cleanup = overlay_remove_cb;
1235         rm_cb->sc_response = NULL;
1236         rm_cb->sc_private = (void*) rm_ctx;
1237
1238         /* Append callback to the end of the list */
1239         if ( !op->o_callback ) {
1240                 op->o_callback = rm_cb;
1241         } else {
1242                 for ( cb = op->o_callback; cb->sc_next; cb = cb->sc_next );
1243                 cb->sc_next = rm_cb;
1244         }
1245 }
1246 #endif /* SLAP_CONFIG_DELETE */
1247
1248 void
1249 overlay_insert( BackendDB *be, slap_overinst *on2, slap_overinst ***prev,
1250         int idx )
1251 {
1252         slap_overinfo *oi = (slap_overinfo *)be->bd_info;
1253
1254         if ( idx == -1 ) {
1255                 on2->on_next = oi->oi_list;
1256                 oi->oi_list = on2;
1257         } else {
1258                 int i, novs;
1259                 slap_overinst *on, **prev;
1260
1261                 /* Since the list is in reverse order and is singly linked,
1262                  * we have to count the overlays and then insert backwards.
1263                  * Adding on overlay at a specific point should be a pretty
1264                  * infrequent occurrence.
1265                  */
1266                 novs = 0;
1267                 for ( on = oi->oi_list; on; on=on->on_next )
1268                         novs++;
1269
1270                 if (idx > novs)
1271                         idx = 0;
1272                 else
1273                         idx = novs - idx;
1274
1275                 /* advance to insertion point */
1276                 prev = &oi->oi_list;
1277                 for ( i=0; i<idx; i++ ) {
1278                         on = *prev;
1279                         prev = &on->on_next;
1280                 }
1281                 /* insert */
1282                 on2->on_next = *prev;
1283                 *prev = on2;
1284         }
1285 }
1286
1287 void
1288 overlay_move( BackendDB *be, slap_overinst *on, int idx )
1289 {
1290         slap_overinfo *oi = (slap_overinfo *)be->bd_info;
1291         slap_overinst **onp;
1292
1293         for (onp = &oi->oi_list; *onp; onp= &(*onp)->on_next) {
1294                 if ( *onp == on ) {
1295                         *onp = on->on_next;
1296                         break;
1297                 }
1298         }
1299         overlay_insert( be, on, &onp, idx );
1300 }
1301
1302 /* add an overlay to a particular backend. */
1303 int
1304 overlay_config( BackendDB *be, const char *ov, int idx, BackendInfo **res, ConfigReply *cr )
1305 {
1306         slap_overinst *on = NULL, *on2 = NULL, **prev;
1307         slap_overinfo *oi = NULL;
1308         BackendInfo *bi = NULL;
1309
1310         if ( res )
1311                 *res = NULL;
1312
1313         on = overlay_find( ov );
1314         if ( !on ) {
1315                 Debug( LDAP_DEBUG_ANY, "overlay \"%s\" not found\n", ov, 0, 0 );
1316                 return 1;
1317         }
1318
1319         /* If this is the first overlay on this backend, set up the
1320          * overlay info structure
1321          */
1322         if ( !overlay_is_over( be ) ) {
1323                 int     isglobal = 0;
1324
1325                 /* NOTE: the first time a global overlay is configured,
1326                  * frontendDB gets this flag; it is used later by overlays
1327                  * to determine if they're stacked on top of the frontendDB */
1328                 if ( be->bd_info == frontendDB->bd_info || SLAP_ISGLOBALOVERLAY( be ) ) {
1329                         isglobal = 1;
1330                         if ( on->on_bi.bi_flags & SLAPO_BFLAG_DBONLY ) {
1331                                 Debug( LDAP_DEBUG_ANY, "overlay_config(): "
1332                                         "overlay \"%s\" cannot be global.\n",
1333                                         ov, 0, 0 );
1334                                 return 1;
1335                         }
1336
1337                 } else if ( on->on_bi.bi_flags & SLAPO_BFLAG_GLOBONLY ) {
1338                         Debug( LDAP_DEBUG_ANY, "overlay_config(): "
1339                                 "overlay \"%s\" can only be global.\n",
1340                                 ov, 0, 0 );
1341                         return 1;
1342                 }
1343
1344                 oi = ch_malloc( sizeof( slap_overinfo ) );
1345                 oi->oi_orig = be->bd_info;
1346                 oi->oi_bi = *be->bd_info;
1347                 oi->oi_origdb = be;
1348
1349                 if ( isglobal ) {
1350                         SLAP_DBFLAGS( be ) |= SLAP_DBFLAG_GLOBAL_OVERLAY;
1351                 }
1352
1353                 /* Save a pointer to ourself in bi_private.
1354                  */
1355                 oi->oi_bi.bi_private = oi;
1356                 oi->oi_list = NULL;
1357                 bi = (BackendInfo *)oi;
1358
1359                 bi->bi_type = (char *)overtype;
1360
1361                 bi->bi_db_config = over_db_config;
1362                 bi->bi_db_open = over_db_open;
1363                 bi->bi_db_close = over_db_close;
1364                 bi->bi_db_destroy = over_db_destroy;
1365
1366                 bi->bi_op_bind = over_op_bind;
1367                 bi->bi_op_unbind = over_op_unbind;
1368                 bi->bi_op_search = over_op_search;
1369                 bi->bi_op_compare = over_op_compare;
1370                 bi->bi_op_modify = over_op_modify;
1371                 bi->bi_op_modrdn = over_op_modrdn;
1372                 bi->bi_op_add = over_op_add;
1373                 bi->bi_op_delete = over_op_delete;
1374                 bi->bi_op_abandon = over_op_abandon;
1375                 bi->bi_op_cancel = over_op_cancel;
1376
1377                 bi->bi_extended = over_op_extended;
1378
1379                 /*
1380                  * this is fine because it has the same
1381                  * args of the operations; we need to rework
1382                  * all the hooks to share the same args
1383                  * of the operations...
1384                  */
1385                 bi->bi_operational = over_aux_operational;
1386                 bi->bi_chk_referrals = over_aux_chk_referrals;
1387                 bi->bi_chk_controls = over_aux_chk_controls;
1388
1389                 /* these have specific arglists */
1390                 bi->bi_entry_get_rw = over_entry_get_rw;
1391                 bi->bi_entry_release_rw = over_entry_release_rw;
1392                 bi->bi_access_allowed = over_access_allowed;
1393                 bi->bi_acl_group = over_acl_group;
1394                 bi->bi_acl_attribute = over_acl_attribute;
1395                 
1396                 bi->bi_connection_init = over_connection_init;
1397                 bi->bi_connection_destroy = over_connection_destroy;
1398
1399                 be->bd_info = bi;
1400
1401         } else {
1402                 if ( overlay_is_inst( be, ov ) ) {
1403                         if ( SLAPO_SINGLE( be ) ) {
1404                                 Debug( LDAP_DEBUG_ANY, "overlay_config(): "
1405                                         "overlay \"%s\" already in list\n",
1406                                         ov, 0, 0 );
1407                                 return 1;
1408                         }
1409                 }
1410
1411                 oi = be->bd_info->bi_private;
1412         }
1413
1414         /* Insert new overlay into list. By default overlays are
1415          * added to head of list and executed in LIFO order.
1416          */
1417         on2 = ch_calloc( 1, sizeof(slap_overinst) );
1418         *on2 = *on;
1419         on2->on_info = oi;
1420
1421         prev = &oi->oi_list;
1422         /* Do we need to find the insertion point? */
1423         if ( idx >= 0 ) {
1424                 int i;
1425
1426                 /* count current overlays */
1427                 for ( i=0, on=oi->oi_list; on; on=on->on_next, i++ );
1428
1429                 /* are we just appending a new one? */
1430                 if ( idx >= i )
1431                         idx = -1;
1432         }
1433         overlay_insert( be, on2, &prev, idx );
1434
1435         /* Any initialization needed? */
1436         if ( on2->on_bi.bi_db_init ) {
1437                 int rc;
1438                 be->bd_info = (BackendInfo *)on2;
1439                 rc = on2->on_bi.bi_db_init( be, cr);
1440                 be->bd_info = (BackendInfo *)oi;
1441                 if ( rc ) {
1442                         *prev = on2->on_next;
1443                         ch_free( on2 );
1444                         on2 = NULL;
1445                         return rc;
1446                 }
1447         }
1448
1449         if ( res )
1450                 *res = &on2->on_bi;
1451
1452         return 0;
1453 }