Adding upstream version 2.4.47+dfsg.upstream/2.4.47+dfsgupstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1440 insertions, 0 deletions

diff --git a/servers/slapd/backover.c b/servers/slapd/backover.c
new file mode 100644
index 0000000..b5a44ea
--- /dev/null
+++ b/servers/slapd/backover.c
@@ -0,0 +1,1440 @@
+/* backover.c - backend overlay routines */
+/* $OpenLDAP$ */
+/* This work is part of OpenLDAP Software <http://www.openldap.org/>.
+ *
+ * Copyright 2003-2018 The OpenLDAP Foundation.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted only as authorized by the OpenLDAP
+ * Public License.
+ *
+ * A copy of this license is available in the file LICENSE in the
+ * top-level directory of the distribution or, alternatively, at
+ * <http://www.OpenLDAP.org/license.html>.
+ */
+
+/* Functions to overlay other modules over a backend. */
+
+#include "portable.h"
+
+#include <stdio.h>
+
+#include <ac/string.h>
+#include <ac/socket.h>
+
+#define SLAPD_TOOLS
+#include "slap.h"
+#include "config.h"
+
+static slap_overinst *overlays;
+
+static int
+over_db_config(
+	BackendDB *be,
+	const char *fname,
+	int lineno,
+	int argc,
+	char **argv
+)
+{
+	slap_overinfo *oi = be->bd_info->bi_private;
+	slap_overinst *on = oi->oi_list;
+	BackendInfo *bi_orig = be->bd_info;
+	struct ConfigOCs *be_cf_ocs = be->be_cf_ocs;
+	ConfigArgs ca = {0};
+	int rc = 0;
+
+	if ( oi->oi_orig->bi_db_config ) {
+		be->bd_info = oi->oi_orig;
+		be->be_cf_ocs = oi->oi_orig->bi_cf_ocs;
+		rc = oi->oi_orig->bi_db_config( be, fname, lineno,
+			argc, argv );
+
+		if ( be->bd_info != oi->oi_orig ) {
+			slap_overinfo	*oi2;
+			slap_overinst	*on2, **onp;
+			BackendDB	be2 = *be;
+			int		i;
+
+			/* a database added an overlay;
+			 * work it around... */
+			assert( overlay_is_over( be ) );
+			
+			oi2 = ( slap_overinfo * )be->bd_info->bi_private;
+			on2 = oi2->oi_list;
+
+			/* need to put a uniqueness check here as well;
+			 * note that in principle there could be more than
+			 * one overlay as a result of multiple calls to
+			 * overlay_config() */
+			be2.bd_info = (BackendInfo *)oi;
+
+			for ( i = 0, onp = &on2; *onp; i++, onp = &(*onp)->on_next ) {
+				if ( overlay_is_inst( &be2, (*onp)->on_bi.bi_type ) ) {
+					Debug( LDAP_DEBUG_ANY, "over_db_config(): "
+							"warning, freshly added "
+							"overlay #%d \"%s\" is already in list\n",
+							i, (*onp)->on_bi.bi_type, 0 );
+
+					/* NOTE: if the overlay already exists,
+					 * there is no way to merge the results
+					 * of the configuration that may have 
+					 * occurred during bi_db_config(); we
+					 * just issue a warning, and the 
+					 * administrator should deal with this */
+				}
+			}
+			*onp = oi->oi_list;
+
+			oi->oi_list = on2;
+
+			ch_free( be->bd_info );
+		}
+
+		be->bd_info = (BackendInfo *)oi;
+		if ( rc != SLAP_CONF_UNKNOWN ) return rc;
+	}
+
+	ca.argv = argv;
+	ca.argc = argc;
+	ca.fname = fname;
+	ca.lineno = lineno;
+	ca.be = be;
+	snprintf( ca.log, sizeof( ca.log ), "%s: line %d",
+			ca.fname, ca.lineno );
+	ca.op = SLAP_CONFIG_ADD;
+	ca.valx = -1;
+
+	for (; on; on=on->on_next) {
+		rc = SLAP_CONF_UNKNOWN;
+		if (on->on_bi.bi_cf_ocs) {
+			ConfigTable *ct;
+			ca.bi = &on->on_bi;
+			ct = config_find_keyword( on->on_bi.bi_cf_ocs->co_table, &ca );
+			if ( ct ) {
+				ca.table = on->on_bi.bi_cf_ocs->co_type;
+				rc = config_add_vals( ct, &ca );
+				if ( rc != SLAP_CONF_UNKNOWN )
+					break;
+			}
+		}
+		if (on->on_bi.bi_db_config && rc == SLAP_CONF_UNKNOWN) {
+			be->bd_info = &on->on_bi;
+			rc = on->on_bi.bi_db_config( be, fname, lineno,
+				argc, argv );
+			if ( rc != SLAP_CONF_UNKNOWN ) break;
+		}
+	}
+	be->bd_info = bi_orig;
+	be->be_cf_ocs = be_cf_ocs;
+	
+	return rc;
+}
+
+static int
+over_db_open(
+	BackendDB *be,
+	ConfigReply *cr
+)
+{
+	slap_overinfo *oi = be->bd_info->bi_private;
+	slap_overinst *on = oi->oi_list;
+	BackendDB db = *be;
+	int rc = 0;
+
+	db.be_flags |= SLAP_DBFLAG_OVERLAY;
+	db.bd_info = oi->oi_orig;
+	if ( db.bd_info->bi_db_open ) {
+		rc = db.bd_info->bi_db_open( &db, cr );
+	}
+
+	for (; on && rc == 0; on=on->on_next) {
+		db.bd_info = &on->on_bi;
+		if ( db.bd_info->bi_db_open ) {
+			rc = db.bd_info->bi_db_open( &db, cr );
+		}
+	}
+
+	return rc;
+}
+
+static int
+over_db_close(
+	BackendDB *be,
+	ConfigReply *cr
+)
+{
+	slap_overinfo *oi = be->bd_info->bi_private;
+	slap_overinst *on = oi->oi_list;
+	BackendInfo *bi_orig = be->bd_info;
+	int rc = 0;
+
+	for (; on && rc == 0; on=on->on_next) {
+		be->bd_info = &on->on_bi;
+		if ( be->bd_info->bi_db_close ) {
+			rc = be->bd_info->bi_db_close( be, cr );
+		}
+	}
+
+	if ( oi->oi_orig->bi_db_close ) {
+		be->bd_info = oi->oi_orig;
+		rc = be->bd_info->bi_db_close( be, cr );
+	}
+
+	be->bd_info = bi_orig;
+	return rc;
+}
+
+static int
+over_db_destroy(
+	BackendDB *be,
+	ConfigReply *cr
+)
+{
+	slap_overinfo *oi = be->bd_info->bi_private;
+	slap_overinst *on = oi->oi_list, *next;
+	BackendInfo *bi_orig = be->bd_info;
+	int rc = 0;
+
+	be->bd_info = oi->oi_orig;
+	if ( be->bd_info->bi_db_destroy ) {
+		rc = be->bd_info->bi_db_destroy( be, cr );
+	}
+
+	for (; on && rc == 0; on=on->on_next) {
+		be->bd_info = &on->on_bi;
+		if ( be->bd_info->bi_db_destroy ) {
+			rc = be->bd_info->bi_db_destroy( be, cr );
+		}
+	}
+
+	on = oi->oi_list;
+	if ( on ) {
+		for (next = on->on_next; on; on=next) {
+			next = on->on_next;
+			free( on );
+		}
+	}
+	be->bd_info = bi_orig;
+	free( oi );
+	return rc;
+}
+
+static int
+over_back_response ( Operation *op, SlapReply *rs )
+{
+	slap_overinfo *oi = op->o_callback->sc_private;
+	slap_overinst *on = oi->oi_list;
+	int rc = SLAP_CB_CONTINUE;
+	BackendDB *be = op->o_bd, db = *op->o_bd;
+
+	db.be_flags |= SLAP_DBFLAG_OVERLAY;
+	op->o_bd = &db;
+	for (; on; on=on->on_next ) {
+		if ( on->on_response ) {
+			db.bd_info = (BackendInfo *)on;
+			rc = on->on_response( op, rs );
+			if ( rc != SLAP_CB_CONTINUE ) break;
+		}
+	}
+	/* Bypass the remaining on_response layers, but allow
+	 * normal execution to continue.
+	 */
+	if ( rc == SLAP_CB_BYPASS )
+		rc = SLAP_CB_CONTINUE;
+	op->o_bd = be;
+	return rc;
+}
+
+static int
+over_access_allowed(
+	Operation		*op,
+	Entry			*e,
+	AttributeDescription	*desc,
+	struct berval		*val,
+	slap_access_t		access,
+	AccessControlState	*state,
+	slap_mask_t		*maskp )
+{
+	slap_overinfo *oi;
+	slap_overinst *on;
+	BackendInfo *bi;
+	BackendDB *be = op->o_bd, db;
+	int rc = SLAP_CB_CONTINUE;
+
+	/* FIXME: used to happen for instance during abandon
+	 * when global overlays are used... */
+	assert( op->o_bd != NULL );
+
+	bi = op->o_bd->bd_info;
+	/* Were we invoked on the frontend? */
+	if ( !bi->bi_access_allowed ) {
+		oi = frontendDB->bd_info->bi_private;
+	} else {
+		oi = op->o_bd->bd_info->bi_private;
+	}
+	on = oi->oi_list;
+
+	for ( ; on; on = on->on_next ) {
+		if ( on->on_bi.bi_access_allowed ) {
+			/* NOTE: do not copy the structure until required */
+		 	if ( !SLAP_ISOVERLAY( op->o_bd ) ) {
+ 				db = *op->o_bd;
+				db.be_flags |= SLAP_DBFLAG_OVERLAY;
+				op->o_bd = &db;
+			}
+
+			op->o_bd->bd_info = (BackendInfo *)on;
+			rc = on->on_bi.bi_access_allowed( op, e,
+				desc, val, access, state, maskp );
+			if ( rc != SLAP_CB_CONTINUE ) break;
+		}
+	}
+
+	if ( rc == SLAP_CB_CONTINUE ) {
+		BI_access_allowed	*bi_access_allowed;
+
+		/* if the database structure was changed, o_bd points to a
+		 * copy of the structure; put the original bd_info in place */
+		if ( SLAP_ISOVERLAY( op->o_bd ) ) {
+			op->o_bd->bd_info = oi->oi_orig;
+		}
+
+		if ( oi->oi_orig->bi_access_allowed ) {
+			bi_access_allowed = oi->oi_orig->bi_access_allowed;
+		} else {
+			bi_access_allowed = slap_access_allowed;
+		}
+
+		rc = bi_access_allowed( op, e,
+			desc, val, access, state, maskp );
+	}
+	/* should not fall thru this far without anything happening... */
+	if ( rc == SLAP_CB_CONTINUE ) {
+		/* access not allowed */
+		rc = 0;
+	}
+
+	op->o_bd = be;
+	op->o_bd->bd_info = bi;
+
+	return rc;
+}
+
+int
+overlay_entry_get_ov(
+	Operation		*op,
+	struct berval	*dn,
+	ObjectClass		*oc,
+	AttributeDescription	*ad,
+	int	rw,
+	Entry	**e,
+	slap_overinst *on )
+{
+	slap_overinfo *oi = on->on_info;
+	BackendDB *be = op->o_bd, db;
+	BackendInfo *bi = op->o_bd->bd_info;
+	int rc = SLAP_CB_CONTINUE;
+
+	for ( ; on; on = on->on_next ) {
+		if ( on->on_bi.bi_entry_get_rw ) {
+			/* NOTE: do not copy the structure until required */
+		 	if ( !SLAP_ISOVERLAY( op->o_bd ) ) {
+ 				db = *op->o_bd;
+				db.be_flags |= SLAP_DBFLAG_OVERLAY;
+				op->o_bd = &db;
+			}
+
+			op->o_bd->bd_info = (BackendInfo *)on;
+			rc = on->on_bi.bi_entry_get_rw( op, dn,
+				oc, ad, rw, e );
+			if ( rc != SLAP_CB_CONTINUE ) break;
+		}
+	}
+
+	if ( rc == SLAP_CB_CONTINUE ) {
+		/* if the database structure was changed, o_bd points to a
+		 * copy of the structure; put the original bd_info in place */
+		if ( SLAP_ISOVERLAY( op->o_bd ) ) {
+			op->o_bd->bd_info = oi->oi_orig;
+		}
+
+		if ( oi->oi_orig->bi_entry_get_rw ) {
+			rc = oi->oi_orig->bi_entry_get_rw( op, dn,
+				oc, ad, rw, e );
+		}
+	}
+	/* should not fall thru this far without anything happening... */
+	if ( rc == SLAP_CB_CONTINUE ) {
+		rc = LDAP_UNWILLING_TO_PERFORM;
+	}
+
+	op->o_bd = be;
+	op->o_bd->bd_info = bi;
+
+	return rc;
+}
+
+static int
+over_entry_get_rw(
+	Operation		*op,
+	struct berval	*dn,
+	ObjectClass		*oc,
+	AttributeDescription	*ad,
+	int	rw,
+	Entry	**e )
+{
+	slap_overinfo *oi;
+	slap_overinst *on;
+
+	assert( op->o_bd != NULL );
+
+	oi = op->o_bd->bd_info->bi_private;
+	on = oi->oi_list;
+
+	return overlay_entry_get_ov( op, dn, oc, ad, rw, e, on );
+}
+
+int
+overlay_entry_release_ov(
+	Operation	*op,
+	Entry	*e,
+	int rw,
+	slap_overinst *on )
+{
+	slap_overinfo *oi = on->on_info;
+	BackendDB *be = op->o_bd, db;
+	BackendInfo *bi = op->o_bd->bd_info;
+	int rc = SLAP_CB_CONTINUE;
+
+	for ( ; on; on = on->on_next ) {
+		if ( on->on_bi.bi_entry_release_rw ) {
+			/* NOTE: do not copy the structure until required */
+		 	if ( !SLAP_ISOVERLAY( op->o_bd ) ) {
+ 				db = *op->o_bd;
+				db.be_flags |= SLAP_DBFLAG_OVERLAY;
+				op->o_bd = &db;
+			}
+
+			op->o_bd->bd_info = (BackendInfo *)on;
+			rc = on->on_bi.bi_entry_release_rw( op, e, rw );
+			if ( rc != SLAP_CB_CONTINUE ) break;
+		}
+	}
+
+	if ( rc == SLAP_CB_CONTINUE ) {
+		/* if the database structure was changed, o_bd points to a
+		 * copy of the structure; put the original bd_info in place */
+		if ( SLAP_ISOVERLAY( op->o_bd ) ) {
+			op->o_bd->bd_info = oi->oi_orig;
+		}
+
+		if ( oi->oi_orig->bi_entry_release_rw ) {
+			rc = oi->oi_orig->bi_entry_release_rw( op, e, rw );
+		}
+	}
+	/* should not fall thru this far without anything happening... */
+	if ( rc == SLAP_CB_CONTINUE ) {
+		entry_free( e );
+		rc = 0;
+	}
+
+	op->o_bd = be;
+	op->o_bd->bd_info = bi;
+
+	return rc;
+}
+
+static int
+over_entry_release_rw(
+	Operation	*op,
+	Entry	*e,
+	int rw )
+{
+	slap_overinfo *oi;
+	slap_overinst *on;
+
+	assert( op->o_bd != NULL );
+
+	oi = op->o_bd->bd_info->bi_private;
+	on = oi->oi_list;
+
+	return overlay_entry_release_ov( op, e, rw, on );
+}
+
+static int
+over_acl_group(
+	Operation		*op,
+	Entry			*e,
+	struct berval		*gr_ndn,
+	struct berval		*op_ndn,
+	ObjectClass		*group_oc,
+	AttributeDescription	*group_at )
+{
+	slap_overinfo *oi;
+	slap_overinst *on;
+	BackendInfo *bi;
+	BackendDB *be = op->o_bd, db;
+	int rc = SLAP_CB_CONTINUE;
+
+	/* FIXME: used to happen for instance during abandon
+	 * when global overlays are used... */
+	assert( be != NULL );
+
+	bi = be->bd_info;
+	oi = bi->bi_private;
+	on = oi->oi_list;
+
+	for ( ; on; on = on->on_next ) {
+		if ( on->on_bi.bi_acl_group ) {
+			/* NOTE: do not copy the structure until required */
+		 	if ( !SLAP_ISOVERLAY( op->o_bd ) ) {
+ 				db = *op->o_bd;
+				db.be_flags |= SLAP_DBFLAG_OVERLAY;
+				op->o_bd = &db;
+			}
+
+			op->o_bd->bd_info = (BackendInfo *)on;
+			rc = on->on_bi.bi_acl_group( op, e,
+				gr_ndn, op_ndn, group_oc, group_at );
+			if ( rc != SLAP_CB_CONTINUE ) break;
+		}
+	}
+
+	if ( rc == SLAP_CB_CONTINUE ) {
+		BI_acl_group		*bi_acl_group;
+
+		/* if the database structure was changed, o_bd points to a
+		 * copy of the structure; put the original bd_info in place */
+		if ( SLAP_ISOVERLAY( op->o_bd ) ) {
+			op->o_bd->bd_info = oi->oi_orig;
+		}
+
+		if ( oi->oi_orig->bi_acl_group ) {
+			bi_acl_group = oi->oi_orig->bi_acl_group;
+		} else {
+			bi_acl_group = backend_group;
+		}
+
+		rc = bi_acl_group( op, e,
+			gr_ndn, op_ndn, group_oc, group_at );
+	}
+	/* should not fall thru this far without anything happening... */
+	if ( rc == SLAP_CB_CONTINUE ) {
+		/* access not allowed */
+		rc = 0;
+	}
+
+	op->o_bd = be;
+	op->o_bd->bd_info = bi;
+
+	return rc;
+}
+
+static int
+over_acl_attribute(
+	Operation		*op,
+	Entry			*target,
+	struct berval		*entry_ndn,
+	AttributeDescription	*entry_at,
+	BerVarray		*vals,
+	slap_access_t		access )
+{
+	slap_overinfo *oi;
+	slap_overinst *on;
+	BackendInfo *bi;
+	BackendDB *be = op->o_bd, db;
+	int rc = SLAP_CB_CONTINUE;
+
+	/* FIXME: used to happen for instance during abandon
+	 * when global overlays are used... */
+	assert( be != NULL );
+
+	bi = be->bd_info;
+	oi = bi->bi_private;
+	on = oi->oi_list;
+
+	for ( ; on; on = on->on_next ) {
+		if ( on->on_bi.bi_acl_attribute ) {
+			/* NOTE: do not copy the structure until required */
+		 	if ( !SLAP_ISOVERLAY( op->o_bd ) ) {
+ 				db = *op->o_bd;
+				db.be_flags |= SLAP_DBFLAG_OVERLAY;
+				op->o_bd = &db;
+			}
+
+			op->o_bd->bd_info = (BackendInfo *)on;
+			rc = on->on_bi.bi_acl_attribute( op, target,
+				entry_ndn, entry_at, vals, access );
+			if ( rc != SLAP_CB_CONTINUE ) break;
+		}
+	}
+
+	if ( rc == SLAP_CB_CONTINUE ) {
+		BI_acl_attribute		*bi_acl_attribute;
+
+		/* if the database structure was changed, o_bd points to a
+		 * copy of the structure; put the original bd_info in place */
+		if ( SLAP_ISOVERLAY( op->o_bd ) ) {
+			op->o_bd->bd_info = oi->oi_orig;
+		}
+
+		if ( oi->oi_orig->bi_acl_attribute ) {
+			bi_acl_attribute = oi->oi_orig->bi_acl_attribute;
+		} else {
+			bi_acl_attribute = backend_attribute;
+		}
+
+		rc = bi_acl_attribute( op, target,
+			entry_ndn, entry_at, vals, access );
+	}
+	/* should not fall thru this far without anything happening... */
+	if ( rc == SLAP_CB_CONTINUE ) {
+		/* access not allowed */
+		rc = 0;
+	}
+
+	op->o_bd = be;
+	op->o_bd->bd_info = bi;
+
+	return rc;
+}
+
+int
+overlay_callback_after_backover( Operation *op, slap_callback *sc, int append )
+{
+	slap_callback **scp;
+
+	for ( scp = &op->o_callback; *scp != NULL; scp = &(*scp)->sc_next ) {
+		if ( (*scp)->sc_response == over_back_response ) {
+			sc->sc_next = (*scp)->sc_next;
+			(*scp)->sc_next = sc;
+			return 0;
+		}
+	}
+
+	if ( append ) {
+		*scp = sc;
+		return 0;
+	}
+
+	return 1;
+}
+
+/*
+ * default return code in case of missing backend function
+ * and overlay stack returning SLAP_CB_CONTINUE
+ */
+static int op_rc[ op_last ] = {
+	LDAP_UNWILLING_TO_PERFORM,	/* bind */
+	LDAP_UNWILLING_TO_PERFORM,	/* unbind */
+	LDAP_UNWILLING_TO_PERFORM,	/* search */
+	SLAP_CB_CONTINUE,		/* compare; pass to frontend */
+	LDAP_UNWILLING_TO_PERFORM,	/* modify */
+	LDAP_UNWILLING_TO_PERFORM,	/* modrdn */
+	LDAP_UNWILLING_TO_PERFORM,	/* add */
+	LDAP_UNWILLING_TO_PERFORM,	/* delete */
+	LDAP_UNWILLING_TO_PERFORM,	/* abandon */
+	LDAP_UNWILLING_TO_PERFORM,	/* cancel */
+	LDAP_UNWILLING_TO_PERFORM,	/* extended */
+	LDAP_SUCCESS,			/* aux_operational */
+	LDAP_SUCCESS,			/* aux_chk_referrals */
+	SLAP_CB_CONTINUE		/* aux_chk_controls; pass to frontend */
+};
+
+int overlay_op_walk(
+	Operation *op,
+	SlapReply *rs,
+	slap_operation_t which,
+	slap_overinfo *oi,
+	slap_overinst *on
+)
+{
+	BI_op_bind **func;
+	int rc = SLAP_CB_CONTINUE;
+
+	for (; on; on=on->on_next ) {
+		func = &on->on_bi.bi_op_bind;
+		if ( func[which] ) {
+			op->o_bd->bd_info = (BackendInfo *)on;
+			rc = func[which]( op, rs );
+			if ( rc != SLAP_CB_CONTINUE ) break;
+		}
+	}
+	if ( rc == SLAP_CB_BYPASS )
+		rc = SLAP_CB_CONTINUE;
+
+	/* if an overlay halted processing, make sure
+	 * any previously set cleanup handlers are run
+	 */
+	if ( rc != SLAP_CB_CONTINUE )
+		goto cleanup;
+
+	func = &oi->oi_orig->bi_op_bind;
+	if ( func[which] ) {
+		op->o_bd->bd_info = oi->oi_orig;
+		rc = func[which]( op, rs );
+	}
+	/* should not fall thru this far without anything happening... */
+	if ( rc == SLAP_CB_CONTINUE ) {
+		rc = op_rc[ which ];
+	}
+
+	/* The underlying backend didn't handle the request, make sure
+	 * overlay cleanup is processed.
+	 */
+	if ( rc == LDAP_UNWILLING_TO_PERFORM ) {
+		slap_callback *sc_next;
+cleanup:
+		for ( ; op->o_callback && op->o_callback->sc_response !=
+			over_back_response; op->o_callback = sc_next ) {
+			sc_next = op->o_callback->sc_next;
+			if ( op->o_callback->sc_cleanup ) {
+				op->o_callback->sc_cleanup( op, rs );
+			}
+		}
+	}
+	return rc;
+}
+
+static int
+over_op_func(
+	Operation *op,
+	SlapReply *rs,
+	slap_operation_t which
+)
+{
+	slap_overinfo *oi;
+	slap_overinst *on;
+	BackendDB *be = op->o_bd, db;
+	slap_callback cb = {NULL, over_back_response, NULL, NULL}, **sc;
+	int rc = SLAP_CB_CONTINUE;
+
+	/* FIXME: used to happen for instance during abandon
+	 * when global overlays are used... */
+	assert( op->o_bd != NULL );
+
+	oi = op->o_bd->bd_info->bi_private;
+	on = oi->oi_list;
+
+ 	if ( !SLAP_ISOVERLAY( op->o_bd )) {
+ 		db = *op->o_bd;
+		db.be_flags |= SLAP_DBFLAG_OVERLAY;
+		op->o_bd = &db;
+	}
+	cb.sc_next = op->o_callback;
+	cb.sc_private = oi;
+	op->o_callback = &cb;
+
+	rc = overlay_op_walk( op, rs, which, oi, on );
+	for ( sc = &op->o_callback; *sc; sc = &(*sc)->sc_next ) {
+		if ( *sc == &cb ) {
+			*sc = cb.sc_next;
+			break;
+		}
+	}
+
+	op->o_bd = be;
+	return rc;
+}
+
+static int
+over_op_bind( Operation *op, SlapReply *rs )
+{
+	return over_op_func( op, rs, op_bind );
+}
+
+static int
+over_op_unbind( Operation *op, SlapReply *rs )
+{
+	return over_op_func( op, rs, op_unbind );
+}
+
+static int
+over_op_search( Operation *op, SlapReply *rs )
+{
+	return over_op_func( op, rs, op_search );
+}
+
+static int
+over_op_compare( Operation *op, SlapReply *rs )
+{
+	return over_op_func( op, rs, op_compare );
+}
+
+static int
+over_op_modify( Operation *op, SlapReply *rs )
+{
+	return over_op_func( op, rs, op_modify );
+}
+
+static int
+over_op_modrdn( Operation *op, SlapReply *rs )
+{
+	return over_op_func( op, rs, op_modrdn );
+}
+
+static int
+over_op_add( Operation *op, SlapReply *rs )
+{
+	return over_op_func( op, rs, op_add );
+}
+
+static int
+over_op_delete( Operation *op, SlapReply *rs )
+{
+	return over_op_func( op, rs, op_delete );
+}
+
+static int
+over_op_abandon( Operation *op, SlapReply *rs )
+{
+	return over_op_func( op, rs, op_abandon );
+}
+
+static int
+over_op_cancel( Operation *op, SlapReply *rs )
+{
+	return over_op_func( op, rs, op_cancel );
+}
+
+static int
+over_op_extended( Operation *op, SlapReply *rs )
+{
+	return over_op_func( op, rs, op_extended );
+}
+
+static int
+over_aux_operational( Operation *op, SlapReply *rs )
+{
+	return over_op_func( op, rs, op_aux_operational );
+}
+
+static int
+over_aux_chk_referrals( Operation *op, SlapReply *rs )
+{
+	return over_op_func( op, rs, op_aux_chk_referrals );
+}
+
+static int
+over_aux_chk_controls( Operation *op, SlapReply *rs )
+{
+	return over_op_func( op, rs, op_aux_chk_controls );
+}
+
+enum conn_which {
+	conn_init = 0,
+	conn_destroy,
+	conn_last
+};
+
+static int
+over_connection_func(
+	BackendDB	*bd,
+	Connection	*conn,
+	enum conn_which	which
+)
+{
+	slap_overinfo		*oi;
+	slap_overinst		*on;
+	BackendDB		db;
+	int			rc = SLAP_CB_CONTINUE;
+	BI_connection_init	**func;
+
+	/* FIXME: used to happen for instance during abandon
+	 * when global overlays are used... */
+	assert( bd != NULL );
+
+	oi = bd->bd_info->bi_private;
+	on = oi->oi_list;
+
+ 	if ( !SLAP_ISOVERLAY( bd ) ) {
+ 		db = *bd;
+		db.be_flags |= SLAP_DBFLAG_OVERLAY;
+		bd = &db;
+	}
+
+	for ( ; on; on = on->on_next ) {
+		func = &on->on_bi.bi_connection_init;
+		if ( func[ which ] ) {
+			bd->bd_info = (BackendInfo *)on;
+			rc = func[ which ]( bd, conn );
+			if ( rc != SLAP_CB_CONTINUE ) break;
+		}
+	}
+
+	func = &oi->oi_orig->bi_connection_init;
+	if ( func[ which ] && rc == SLAP_CB_CONTINUE ) {
+		bd->bd_info = oi->oi_orig;
+		rc = func[ which ]( bd, conn );
+	}
+	/* should not fall thru this far without anything happening... */
+	if ( rc == SLAP_CB_CONTINUE ) {
+		rc = LDAP_UNWILLING_TO_PERFORM;
+	}
+
+	return rc;
+}
+
+static int
+over_connection_init(
+	BackendDB	*bd,
+	Connection	*conn
+)
+{
+	return over_connection_func( bd, conn, conn_init );
+}
+
+static int
+over_connection_destroy(
+	BackendDB	*bd,
+	Connection	*conn
+)
+{
+	return over_connection_func( bd, conn, conn_destroy );
+}
+
+int
+overlay_register(
+	slap_overinst *on
+)
+{
+	slap_overinst	*tmp;
+
+	/* FIXME: check for duplicates? */
+	for ( tmp = overlays; tmp != NULL; tmp = tmp->on_next ) {
+		if ( strcmp( on->on_bi.bi_type, tmp->on_bi.bi_type ) == 0 ) {
+			Debug( LDAP_DEBUG_ANY,
+				"overlay_register(\"%s\"): "
+				"name already in use.\n",
+				on->on_bi.bi_type, 0, 0 );
+			return -1;
+		}
+
+		if ( on->on_bi.bi_obsolete_names != NULL ) {
+			int	i;
+
+			for ( i = 0; on->on_bi.bi_obsolete_names[ i ] != NULL; i++ ) {
+				if ( strcmp( on->on_bi.bi_obsolete_names[ i ], tmp->on_bi.bi_type ) == 0 ) {
+					Debug( LDAP_DEBUG_ANY,
+						"overlay_register(\"%s\"): "
+						"obsolete name \"%s\" already in use "
+						"by overlay \"%s\".\n",
+						on->on_bi.bi_type,
+						on->on_bi.bi_obsolete_names[ i ],
+						tmp->on_bi.bi_type );
+					return -1;
+				}
+			}
+		}
+
+		if ( tmp->on_bi.bi_obsolete_names != NULL ) {
+			int	i;
+
+			for ( i = 0; tmp->on_bi.bi_obsolete_names[ i ] != NULL; i++ ) {
+				int	j;
+
+				if ( strcmp( on->on_bi.bi_type, tmp->on_bi.bi_obsolete_names[ i ] ) == 0 ) {
+					Debug( LDAP_DEBUG_ANY,
+						"overlay_register(\"%s\"): "
+						"name already in use "
+						"as obsolete by overlay \"%s\".\n",
+						on->on_bi.bi_type,
+						tmp->on_bi.bi_obsolete_names[ i ], 0 );
+					return -1;
+				}
+
+				if ( on->on_bi.bi_obsolete_names != NULL ) {
+					for ( j = 0; on->on_bi.bi_obsolete_names[ j ] != NULL; j++ ) {
+						if ( strcmp( on->on_bi.bi_obsolete_names[ j ], tmp->on_bi.bi_obsolete_names[ i ] ) == 0 ) {
+							Debug( LDAP_DEBUG_ANY,
+								"overlay_register(\"%s\"): "
+								"obsolete name \"%s\" already in use "
+								"as obsolete by overlay \"%s\".\n",
+								on->on_bi.bi_type,
+								on->on_bi.bi_obsolete_names[ j ],
+								tmp->on_bi.bi_type );
+							return -1;
+						}
+					}
+				}
+			}
+		}
+	}
+
+	on->on_next = overlays;
+	overlays = on;
+	return 0;
+}
+
+/*
+ * iterator on registered overlays; overlay_next( NULL ) returns the first
+ * overlay; subsequent calls with the previously returned value allow to 
+ * iterate over the entire list; returns NULL when no more overlays are 
+ * registered.
+ */
+
+slap_overinst *
+overlay_next(
+	slap_overinst *on
+)
+{
+	if ( on == NULL ) {
+		return overlays;
+	}
+
+	return on->on_next;
+}
+
+/*
+ * returns a specific registered overlay based on the type; NULL if not
+ * registered.
+ */
+
+slap_overinst *
+overlay_find( const char *over_type )
+{
+	slap_overinst *on = overlays;
+
+	assert( over_type != NULL );
+
+	for ( ; on; on = on->on_next ) {
+		if ( strcmp( on->on_bi.bi_type, over_type ) == 0 ) {
+			goto foundit;
+		}
+
+		if ( on->on_bi.bi_obsolete_names != NULL ) {
+			int	i;
+
+			for ( i = 0; on->on_bi.bi_obsolete_names[ i ] != NULL; i++ ) {
+				if ( strcmp( on->on_bi.bi_obsolete_names[ i ], over_type ) == 0 ) {
+					Debug( LDAP_DEBUG_ANY,
+						"overlay_find(\"%s\"): "
+						"obsolete name for \"%s\".\n",
+						on->on_bi.bi_obsolete_names[ i ],
+						on->on_bi.bi_type, 0 );
+					goto foundit;
+				}
+			}
+		}
+	}
+
+foundit:;
+	return on;
+}
+
+static const char overtype[] = "over";
+
+/*
+ * returns TRUE (1) if the database is actually an overlay instance;
+ * FALSE (0) otherwise.
+ */
+
+int
+overlay_is_over( BackendDB *be )
+{
+	return be->bd_info->bi_type == overtype;
+}
+
+/*
+ * returns TRUE (1) if the given database is actually an overlay
+ * instance and, somewhere in the list, contains the requested overlay;
+ * FALSE (0) otherwise.
+ */
+
+int
+overlay_is_inst( BackendDB *be, const char *over_type )
+{
+	slap_overinst	*on;
+
+	assert( be != NULL );
+
+	if ( !overlay_is_over( be ) ) {
+		return 0;
+	}
+	
+	on = ((slap_overinfo *)be->bd_info->bi_private)->oi_list;
+	for ( ; on; on = on->on_next ) {
+		if ( strcmp( on->on_bi.bi_type, over_type ) == 0 ) {
+			return 1;
+		}
+	}
+
+	return 0;
+}
+
+int
+overlay_register_control( BackendDB *be, const char *oid )
+{
+	int		gotit = 0;
+	int		cid;
+
+	if ( slap_find_control_id( oid, &cid ) == LDAP_CONTROL_NOT_FOUND ) {
+		return -1;
+	}
+
+	if ( SLAP_ISGLOBALOVERLAY( be ) ) {
+		BackendDB *bd;
+		
+		/* add to all backends... */
+		LDAP_STAILQ_FOREACH( bd, &backendDB, be_next ) {
+			if ( bd == be->bd_self ) {
+				gotit = 1;
+			}
+
+			/* overlays can be instanciated multiple times, use
+			 * be_ctrls[ cid ] as an instance counter, so that the
+			 * overlay's controls are only really disabled after the
+			 * last instance called overlay_register_control() */
+			bd->be_ctrls[ cid ]++;
+			bd->be_ctrls[ SLAP_MAX_CIDS ] = 1;
+		}
+
+	}
+	
+	if ( !gotit ) {
+		/* overlays can be instanciated multiple times, use
+		 * be_ctrls[ cid ] as an instance counter, so that the
+		 * overlay's controls are only really unregistered after the
+		 * last instance called overlay_register_control() */
+		be->bd_self->be_ctrls[ cid ]++;
+		be->bd_self->be_ctrls[ SLAP_MAX_CIDS ] = 1;
+	}
+
+	return 0;
+}
+
+#ifdef SLAP_CONFIG_DELETE
+void
+overlay_unregister_control( BackendDB *be, const char *oid )
+{
+	int		gotit = 0;
+	int		cid;
+
+	if ( slap_find_control_id( oid, &cid ) == LDAP_CONTROL_NOT_FOUND ) {
+		return;
+	}
+
+	if ( SLAP_ISGLOBALOVERLAY( be ) ) {
+		BackendDB *bd;
+
+		/* remove from all backends... */
+		LDAP_STAILQ_FOREACH( bd, &backendDB, be_next ) {
+			if ( bd == be->bd_self ) {
+				gotit = 1;
+			}
+
+			bd->be_ctrls[ cid ]--;
+		}
+	}
+
+	if ( !gotit ) {
+		be->bd_self->be_ctrls[ cid ]--;
+	}
+}
+#endif /* SLAP_CONFIG_DELETE */
+
+void
+overlay_destroy_one( BackendDB *be, slap_overinst *on )
+{
+	slap_overinfo *oi = on->on_info;
+	slap_overinst **oidx;
+
+	for ( oidx = &oi->oi_list; *oidx; oidx = &(*oidx)->on_next ) {
+		if ( *oidx == on ) {
+			*oidx = on->on_next;
+			if ( on->on_bi.bi_db_destroy ) {
+				BackendInfo *bi_orig = be->bd_info;
+				be->bd_info = (BackendInfo *)on;
+				on->on_bi.bi_db_destroy( be, NULL );
+				be->bd_info = bi_orig;
+			}
+			free( on );
+			break;
+		}
+	}
+}
+
+#ifdef SLAP_CONFIG_DELETE
+typedef struct ov_remove_ctx {
+	BackendDB *be;
+	slap_overinst *on;
+} ov_remove_ctx;
+
+int
+overlay_remove_cb( Operation *op, SlapReply *rs )
+{
+	ov_remove_ctx *rm_ctx = (ov_remove_ctx*) op->o_callback->sc_private;
+	BackendInfo *bi_orig = rm_ctx->be->bd_info;
+
+	rm_ctx->be->bd_info = (BackendInfo*) rm_ctx->on;
+
+	if ( rm_ctx->on->on_bi.bi_db_close ) {
+		rm_ctx->on->on_bi.bi_db_close( rm_ctx->be, NULL );
+	}
+	if ( rm_ctx->on->on_bi.bi_db_destroy ) {
+		rm_ctx->on->on_bi.bi_db_destroy( rm_ctx->be, NULL );
+	}
+
+	/* clean up after removing last overlay */
+	if ( ! rm_ctx->on->on_info->oi_list ) {
+		/* reset db flags and bd_info to orig */
+		SLAP_DBFLAGS( rm_ctx->be ) &= ~SLAP_DBFLAG_GLOBAL_OVERLAY;
+		rm_ctx->be->bd_info = rm_ctx->on->on_info->oi_orig;
+		ch_free(rm_ctx->on->on_info);
+	} else {
+		rm_ctx->be->bd_info = bi_orig;
+	}
+	free( rm_ctx->on );
+	op->o_tmpfree(rm_ctx, op->o_tmpmemctx);
+	return SLAP_CB_CONTINUE;
+}
+
+void
+overlay_remove( BackendDB *be, slap_overinst *on, Operation *op )
+{
+	slap_overinfo *oi = on->on_info;
+	slap_overinst **oidx;
+	ov_remove_ctx *rm_ctx;
+	slap_callback *rm_cb, *cb;
+
+	/* remove overlay from oi_list */
+	for ( oidx = &oi->oi_list; *oidx; oidx = &(*oidx)->on_next ) {
+		if ( *oidx == on ) {
+			*oidx = on->on_next;
+			break;
+		}
+	}
+
+	/* The db_close and db_destroy handlers to cleanup a release
+	 * the overlay's resources are called from the cleanup callback
+	 */
+	rm_ctx = op->o_tmpalloc( sizeof( ov_remove_ctx ), op->o_tmpmemctx );
+	rm_ctx->be = be;
+	rm_ctx->on = on;
+
+	rm_cb = op->o_tmpalloc( sizeof( slap_callback ), op->o_tmpmemctx );
+	rm_cb->sc_next = NULL;
+	rm_cb->sc_cleanup = overlay_remove_cb;
+	rm_cb->sc_response = NULL;
+	rm_cb->sc_private = (void*) rm_ctx;
+	rm_cb->sc_writewait = NULL;
+
+	/* Append callback to the end of the list */
+	if ( !op->o_callback ) {
+		op->o_callback = rm_cb;
+	} else {
+		for ( cb = op->o_callback; cb->sc_next; cb = cb->sc_next );
+		cb->sc_next = rm_cb;
+	}
+}
+#endif /* SLAP_CONFIG_DELETE */
+
+void
+overlay_insert( BackendDB *be, slap_overinst *on2, slap_overinst ***prev,
+	int idx )
+{
+	slap_overinfo *oi = (slap_overinfo *)be->bd_info;
+
+	if ( idx == -1 ) {
+		on2->on_next = oi->oi_list;
+		oi->oi_list = on2;
+	} else {
+		int i, novs;
+		slap_overinst *on, **prev;
+
+		/* Since the list is in reverse order and is singly linked,
+		 * we have to count the overlays and then insert backwards.
+		 * Adding on overlay at a specific point should be a pretty
+		 * infrequent occurrence.
+		 */
+		novs = 0;
+		for ( on = oi->oi_list; on; on=on->on_next )
+			novs++;
+
+		if (idx > novs)
+			idx = 0;
+		else
+			idx = novs - idx;
+
+		/* advance to insertion point */
+		prev = &oi->oi_list;
+		for ( i=0; i<idx; i++ ) {
+			on = *prev;
+			prev = &on->on_next;
+		}
+		/* insert */
+		on2->on_next = *prev;
+		*prev = on2;
+	}
+}
+
+void
+overlay_move( BackendDB *be, slap_overinst *on, int idx )
+{
+	slap_overinfo *oi = (slap_overinfo *)be->bd_info;
+	slap_overinst **onp;
+
+	for (onp = &oi->oi_list; *onp; onp= &(*onp)->on_next) {
+		if ( *onp == on ) {
+			*onp = on->on_next;
+			break;
+		}
+	}
+	overlay_insert( be, on, &onp, idx );
+}
+
+/* add an overlay to a particular backend. */
+int
+overlay_config( BackendDB *be, const char *ov, int idx, BackendInfo **res, ConfigReply *cr )
+{
+	slap_overinst *on = NULL, *on2 = NULL, **prev;
+	slap_overinfo *oi = NULL;
+	BackendInfo *bi = NULL;
+
+	if ( res )
+		*res = NULL;
+
+	on = overlay_find( ov );
+	if ( !on ) {
+		Debug( LDAP_DEBUG_ANY, "overlay \"%s\" not found\n", ov, 0, 0 );
+		return 1;
+	}
+
+	/* If this is the first overlay on this backend, set up the
+	 * overlay info structure
+	 */
+	if ( !overlay_is_over( be ) ) {
+		int	isglobal = 0;
+
+		/* NOTE: the first time a global overlay is configured,
+		 * frontendDB gets this flag; it is used later by overlays
+		 * to determine if they're stacked on top of the frontendDB */
+		if ( be->bd_info == frontendDB->bd_info || SLAP_ISGLOBALOVERLAY( be ) ) {
+			isglobal = 1;
+			if ( on->on_bi.bi_flags & SLAPO_BFLAG_DBONLY ) {
+				Debug( LDAP_DEBUG_ANY, "overlay_config(): "
+					"overlay \"%s\" cannot be global.\n",
+					ov, 0, 0 );
+				return 1;
+			}
+
+		} else if ( on->on_bi.bi_flags & SLAPO_BFLAG_GLOBONLY ) {
+			Debug( LDAP_DEBUG_ANY, "overlay_config(): "
+				"overlay \"%s\" can only be global.\n",
+				ov, 0, 0 );
+			return 1;
+		}
+
+		oi = ch_malloc( sizeof( slap_overinfo ) );
+		oi->oi_orig = be->bd_info;
+		oi->oi_bi = *be->bd_info;
+		oi->oi_origdb = be;
+
+		if ( isglobal ) {
+			SLAP_DBFLAGS( be ) |= SLAP_DBFLAG_GLOBAL_OVERLAY;
+		}
+
+		/* Save a pointer to ourself in bi_private.
+		 */
+		oi->oi_bi.bi_private = oi;
+		oi->oi_list = NULL;
+		bi = (BackendInfo *)oi;
+
+		bi->bi_type = (char *)overtype;
+
+		bi->bi_db_config = over_db_config;
+		bi->bi_db_open = over_db_open;
+		bi->bi_db_close = over_db_close;
+		bi->bi_db_destroy = over_db_destroy;
+
+		bi->bi_op_bind = over_op_bind;
+		bi->bi_op_unbind = over_op_unbind;
+		bi->bi_op_search = over_op_search;
+		bi->bi_op_compare = over_op_compare;
+		bi->bi_op_modify = over_op_modify;
+		bi->bi_op_modrdn = over_op_modrdn;
+		bi->bi_op_add = over_op_add;
+		bi->bi_op_delete = over_op_delete;
+		bi->bi_op_abandon = over_op_abandon;
+		bi->bi_op_cancel = over_op_cancel;
+
+		bi->bi_extended = over_op_extended;
+
+		/*
+		 * this is fine because it has the same
+		 * args of the operations; we need to rework
+		 * all the hooks to share the same args
+		 * of the operations...
+		 */
+		bi->bi_operational = over_aux_operational;
+		bi->bi_chk_referrals = over_aux_chk_referrals;
+		bi->bi_chk_controls = over_aux_chk_controls;
+
+		/* these have specific arglists */
+		bi->bi_entry_get_rw = over_entry_get_rw;
+		bi->bi_entry_release_rw = over_entry_release_rw;
+		bi->bi_access_allowed = over_access_allowed;
+		bi->bi_acl_group = over_acl_group;
+		bi->bi_acl_attribute = over_acl_attribute;
+		
+		bi->bi_connection_init = over_connection_init;
+		bi->bi_connection_destroy = over_connection_destroy;
+
+		be->bd_info = bi;
+
+	} else {
+		if ( overlay_is_inst( be, ov ) ) {
+			if ( SLAPO_SINGLE( be ) ) {
+				Debug( LDAP_DEBUG_ANY, "overlay_config(): "
+					"overlay \"%s\" already in list\n",
+					ov, 0, 0 );
+				return 1;
+			}
+		}
+
+		oi = be->bd_info->bi_private;
+	}
+
+	/* Insert new overlay into list. By default overlays are
+	 * added to head of list and executed in LIFO order.
+	 */
+	on2 = ch_calloc( 1, sizeof(slap_overinst) );
+	*on2 = *on;
+	on2->on_info = oi;
+
+	prev = &oi->oi_list;
+	/* Do we need to find the insertion point? */
+	if ( idx >= 0 ) {
+		int i;
+
+		/* count current overlays */
+		for ( i=0, on=oi->oi_list; on; on=on->on_next, i++ );
+
+		/* are we just appending a new one? */
+		if ( idx >= i )
+			idx = -1;
+	}
+	overlay_insert( be, on2, &prev, idx );
+
+	/* Any initialization needed? */
+	if ( on2->on_bi.bi_db_init ) {
+		int rc;
+		be->bd_info = (BackendInfo *)on2;
+		rc = on2->on_bi.bi_db_init( be, cr);
+		be->bd_info = (BackendInfo *)oi;
+		if ( rc ) {
+			*prev = on2->on_next;
+			ch_free( on2 );
+			on2 = NULL;
+			return rc;
+		}
+	}
+
+	if ( res )
+		*res = &on2->on_bi;
+
+	return 0;
+}
+