diff --git a/contrib/slapd-modules/samba4/Makefile b/contrib/slapd-modules/samba4/Makefile
index 8709a74ffe953bc0ff64b91990c43a1d3d3ad23e..525b5ad8c1cc96e97d20bd7325b7f97403600b6b 100644
--- a/contrib/slapd-modules/samba4/Makefile
+++ b/contrib/slapd-modules/samba4/Makefile
@@ -20,7 +20,7 @@ LIBTOOL=$(LDAP_BUILD)/libtool
 OPT=-g -O2
 CC=gcc
 
-DEFS=-DSLAPD_OVER_RDNVAL=2 -DSLAPD_OVER_PGUID=2
+DEFS=-DSLAPD_OVER_RDNVAL=2 -DSLAPD_OVER_PGUID=2 -DSLAPD_OVER_VERNUM=2
 
 LDAP_INC=-I$(LDAP_SRC)/include -I$(LDAP_SRC)/servers/slapd \
 	-I$(LDAP_BUILD)/include
@@ -37,7 +37,7 @@ libdir=$(exec_prefix)/lib
 libexecdir=$(exec_prefix)/libexec
 moduledir = $(libexecdir)$(ldap_subdir)
 
-PROGRAMS = pguid.la rdnval.la
+PROGRAMS = pguid.la rdnval.la vernum.la
 
 all:	$(PROGRAMS)
 
@@ -55,10 +55,18 @@ rdnval.la:	rdnval.lo
 	$(LIBTOOL) --mode=link $(CC) $(OPT) -version-info 0:0:0 \
 	-rpath $(moduledir) -module -o $@ $? $(LIBS)
 
+vernum.lo:	vernum.c
+	$(LIBTOOL) --mode=compile $(CC) $(OPT) $(DEFS) $(INCS) -c $?
+
+vernum.la:	vernum.lo
+	$(LIBTOOL) --mode=link $(CC) $(OPT) -version-info 0:0:0 \
+	-rpath $(moduledir) -module -o $@ $? $(LIBS)
+
 clean:
 	rm -f \
 		pguid.o pguid.lo pguid.la \
-		rdnval.o rdnval.lo rdnval.la 
+		rdnval.o rdnval.lo rdnval.la \
+		vernum.o vernum.lo vernum.la
 
 install: $(PROGRAMS)
 	mkdir -p $(DESTDIR)$(moduledir)
diff --git a/contrib/slapd-modules/samba4/README b/contrib/slapd-modules/samba4/README
index ecf338ce85900490eaf2409514705ebcff51a1ae..1806fac89e84fd42f4962af63f594e65c955381d 100644
--- a/contrib/slapd-modules/samba4/README
+++ b/contrib/slapd-modules/samba4/README
@@ -41,14 +41,21 @@ To use the overlay, add:
 to your slapd configuration file.  An instance is required for each database
 that needs to maintain this attribute.
 
-This overlay is only set up to be built as a dynamically loaded module.
-On most platforms, in order for the module to be usable, all of the 
+
+  - VERNUM
+
+This overlay increments a counter any time an attribute is modified.
+It is intended to increment the counter 'msDS-KeyVersionNumber' when
+the attribute 'unicodePwd' is modified.
+ 
+
+These overlays are only set up to be built as a dynamically loaded modules.
+On most platforms, in order for the modules to be usable, all of the 
 library dependencies must also be available as shared libraries.
 
-If you need to build the overlay statically, you will have to move it into the
-slapd/overlays directory and edit the Makefile and overlays.c to reference
-it. You will also have to define SLAPD_OVER_SMBK5PWD to SLAPD_MOD_STATIC,
-and add the relevant libraries to the main slapd link command.
+If you need to build the overlays statically, you will have to move them
+into the slapd/overlays directory and edit the Makefile and overlays.c
+to reference them. 
 
 ---
 This work is part of OpenLDAP Software <http://www.openldap.org/>.
diff --git a/contrib/slapd-modules/samba4/vernum.c b/contrib/slapd-modules/samba4/vernum.c
new file mode 100644
index 0000000000000000000000000000000000000000..b074d3fef1b14a01d345cb1d9fda491f0c639fc5
--- /dev/null
+++ b/contrib/slapd-modules/samba4/vernum.c
@@ -0,0 +1,459 @@
+/* vernum.c - RDN value overlay */
+/* $OpenLDAP$ */
+/* This work is part of OpenLDAP Software <http://www.openldap.org/>.
+ *
+ * Copyright 1998-2009 The OpenLDAP Foundation.
+ * Portions Copyright 2008 Pierangelo Masarati.
+ * 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>.
+ */
+/* ACKNOWLEDGEMENTS:
+ * This work was initially developed by Pierangelo Masarati
+ * for inclusion in OpenLDAP Software.
+ */
+
+#include "portable.h"
+
+#ifdef SLAPD_OVER_VERNUM
+
+#include <stdio.h>
+
+#include "ac/string.h"
+#include "ac/socket.h"
+
+#include "slap.h"
+#include "config.h"
+
+#include "lutil.h"
+
+/*
+ * Maintain an attribute (e.g. msDS-KeyVersionNumber) that consists
+ * in a counter of modifications of another attribute (e.g. unicodePwd).
+ */
+
+typedef struct vernum_t {
+	AttributeDescription	*vn_attr;
+	AttributeDescription	*vn_vernum;
+} vernum_t;
+
+static AttributeDescription	*ad_msDS_KeyVersionNumber;
+
+static struct berval		val_init = BER_BVC( "0" );
+static slap_overinst 		vernum;
+
+static int
+vernum_op_add( Operation *op, SlapReply *rs )
+{
+	slap_overinst	*on = (slap_overinst *) op->o_bd->bd_info;
+	vernum_t	*vn = (vernum_t *)on->on_bi.bi_private;
+
+	Attribute *a, **ap;
+	int rc;
+
+	/* NOTE: should we accept an entry still in mods format? */
+	assert( op->ora_e != NULL );
+
+	if ( BER_BVISEMPTY( &op->ora_e->e_nname ) ) {
+		return SLAP_CB_CONTINUE;
+	}
+
+	a = attr_find( op->ora_e->e_attrs, vn->vn_attr );
+	if ( a == NULL ) {
+		return SLAP_CB_CONTINUE;
+	}
+
+	if ( attr_find( op->ora_e->e_attrs, vn->vn_vernum ) != NULL ) {
+		/* already present - leave it alone */
+		return SLAP_CB_CONTINUE;
+	}
+
+	a = attr_alloc( vn->vn_vernum );
+
+	value_add_one( &a->a_vals, &val_init );
+	a->a_nvals = a->a_vals;
+	a->a_numvals = 1;
+
+	for ( ap = &op->ora_e->e_attrs; *ap != NULL; ap = &(*ap)->a_next )
+		/* goto tail */ ;
+
+	*ap = a;
+
+	return SLAP_CB_CONTINUE;
+}
+
+static int
+vernum_op_modify( Operation *op, SlapReply *rs )
+{
+	slap_overinst	*on = (slap_overinst *) op->o_bd->bd_info;
+	vernum_t	*vn = (vernum_t *)on->on_bi.bi_private;
+
+	Modifications *ml, **mlp;
+	struct berval val = BER_BVC( "1" );
+	int rc;
+	unsigned got = 0;
+
+	for ( ml = op->orm_modlist; ml != NULL; ml = ml->sml_next ) {
+		if ( ml->sml_desc == vn->vn_vernum ) {
+			/* already present - leave it alone
+			 * (or should we increment it anyway?) */
+			return SLAP_CB_CONTINUE;
+		}
+
+		if ( ml->sml_desc == vn->vn_attr ) {
+			got = 1;
+		}
+	}
+
+	if ( !got ) {
+		return SLAP_CB_CONTINUE;
+	}
+
+	for ( mlp = &op->orm_modlist; *mlp != NULL; mlp = &(*mlp)->sml_next )
+		/* goto tail */ ;
+
+	/* ITS#6561 */
+#ifdef SLAP_MOD_ADD_IF_NOT_PRESENT
+	/* the initial value is only added if the vernum attr is not present */
+	ml = SLAP_CALLOC( sizeof( Modifications ), 1 );
+	ml->sml_values = SLAP_CALLOC( sizeof( struct berval ) , 2 );
+	value_add_one( &ml->sml_values, &val_init );
+	ml->sml_nvalues = NULL;
+	ml->sml_numvals = 1;
+	ml->sml_op = SLAP_MOD_ADD_IF_NOT_PRESENT;
+	ml->sml_flags = SLAP_MOD_INTERNAL;
+	ml->sml_desc = vn->vn_vernum;
+	ml->sml_type = vn->vn_vernum->ad_cname;
+
+	*mlp = ml;
+	mlp = &ml->sml_next;
+#endif /* SLAP_MOD_ADD_IF_NOT_PRESENT */
+
+	/* this increments by 1 the vernum attr */
+	ml = SLAP_CALLOC( sizeof( Modifications ), 1 );
+	ml->sml_values = SLAP_CALLOC( sizeof( struct berval ) , 2 );
+	value_add_one( &ml->sml_values, &val );
+	ml->sml_nvalues = NULL;
+	ml->sml_numvals = 1;
+	ml->sml_op = LDAP_MOD_INCREMENT;
+	ml->sml_flags = SLAP_MOD_INTERNAL;
+	ml->sml_desc = vn->vn_vernum;
+	ml->sml_type = vn->vn_vernum->ad_cname;
+
+	*mlp = ml;
+
+	return SLAP_CB_CONTINUE;
+}
+
+static int
+vernum_db_init(
+	BackendDB	*be,
+	ConfigReply	*cr)
+{
+	slap_overinst	*on = (slap_overinst *) be->bd_info;
+	vernum_t	*vn = NULL;
+
+	if ( SLAP_ISGLOBALOVERLAY( be ) ) {
+		Log0( LDAP_DEBUG_ANY, LDAP_LEVEL_ERR,
+			"vernum_db_init: vernum cannot be used as global overlay.\n" );
+		return 1;
+	}
+
+	if ( be->be_nsuffix == NULL ) {
+		Log0( LDAP_DEBUG_ANY, LDAP_LEVEL_ERR,
+			"vernum_db_init: database must have suffix\n" );
+		return 1;
+	}
+
+	if ( BER_BVISNULL( &be->be_rootndn ) || BER_BVISEMPTY( &be->be_rootndn ) ) {
+		Log1( LDAP_DEBUG_ANY, LDAP_LEVEL_ERR,
+			"vernum_db_init: missing rootdn for database DN=\"%s\", YMMV\n",
+			be->be_suffix[ 0 ].bv_val );
+	}
+
+	vn = (vernum_t *)ch_calloc( 1, sizeof( vernum_t ) );
+
+	on->on_bi.bi_private = (void *)vn;
+
+	return 0;
+}
+
+typedef struct vernum_mod_t {
+	struct berval ndn;
+	struct vernum_mod_t *next;
+} vernum_mod_t;
+
+typedef struct {
+	BackendDB *bd;
+	vernum_mod_t *mods;
+} vernum_repair_cb_t;
+
+static int
+vernum_repair_cb( Operation *op, SlapReply *rs )
+{
+	int rc;
+	vernum_repair_cb_t *rcb = op->o_callback->sc_private;
+	vernum_mod_t *mod;
+	ber_len_t len;
+	BackendDB *save_bd = op->o_bd;
+
+	switch ( rs->sr_type ) {
+	case REP_SEARCH:
+		break;
+
+	case REP_SEARCHREF:
+	case REP_RESULT:
+		return rs->sr_err;
+
+	default:
+		assert( 0 );
+	}
+
+	assert( rs->sr_entry != NULL );
+
+	len = sizeof( vernum_mod_t ) + rs->sr_entry->e_nname.bv_len + 1;
+	mod = op->o_tmpalloc( len, op->o_tmpmemctx );
+	mod->ndn.bv_len = rs->sr_entry->e_nname.bv_len;
+	mod->ndn.bv_val = (char *)&mod[1];
+	lutil_strncopy( mod->ndn.bv_val, rs->sr_entry->e_nname.bv_val, rs->sr_entry->e_nname.bv_len );
+
+	mod->next = rcb->mods;
+	rcb->mods = mod;
+
+	Debug( LDAP_DEBUG_TRACE, "%s: vernum_repair_cb: scheduling entry DN=\"%s\" for repair\n",
+		op->o_log_prefix, rs->sr_entry->e_name.bv_val, 0 );
+
+	return 0;
+}
+
+static int
+vernum_repair( BackendDB *be )
+{
+	slap_overinst *on = (slap_overinst *)be->bd_info;
+	vernum_t *vn = (vernum_t *)on->on_bi.bi_private;
+	void *ctx = ldap_pvt_thread_pool_context();
+	Connection conn = { 0 };
+	OperationBuffer opbuf;
+	Operation *op;
+	BackendDB db;
+	slap_callback sc = { 0 };
+	vernum_repair_cb_t rcb = { 0 };
+	SlapReply rs = { REP_RESULT };
+	vernum_mod_t *rmod;
+	int nrepaired = 0;
+
+	connection_fake_init2( &conn, &opbuf, ctx, 0 );
+	op = &opbuf.ob_op;
+
+	op->o_tag = LDAP_REQ_SEARCH;
+	memset( &op->oq_search, 0, sizeof( op->oq_search ) );
+
+	assert( !BER_BVISNULL( &be->be_nsuffix[ 0 ] ) );
+
+	op->o_bd = select_backend( &be->be_nsuffix[ 0 ], 0 );
+	assert( op->o_bd != NULL );
+	assert( op->o_bd->be_nsuffix != NULL );
+
+	op->o_req_dn = op->o_bd->be_suffix[ 0 ];
+	op->o_req_ndn = op->o_bd->be_nsuffix[ 0 ];
+
+	op->o_dn = op->o_bd->be_rootdn;
+	op->o_ndn = op->o_bd->be_rootndn;
+
+	op->ors_scope = LDAP_SCOPE_SUBTREE;
+	op->ors_tlimit = SLAP_NO_LIMIT;
+	op->ors_slimit = SLAP_NO_LIMIT;
+	op->ors_attrs = slap_anlist_no_attrs;
+
+	op->ors_filterstr.bv_len = STRLENOF( "(&(=*)(!(=*)))" )
+		+ vn->vn_attr->ad_cname.bv_len
+		+ vn->vn_vernum->ad_cname.bv_len;
+	op->ors_filterstr.bv_val = op->o_tmpalloc( op->ors_filterstr.bv_len + 1, op->o_tmpmemctx );
+	snprintf( op->ors_filterstr.bv_val, op->ors_filterstr.bv_len + 1,
+		"(&(%s=*)(!(%s=*)))",
+		vn->vn_attr->ad_cname.bv_val,
+		vn->vn_vernum->ad_cname.bv_val );
+
+	op->ors_filter = str2filter_x( op, op->ors_filterstr.bv_val );
+	if ( op->ors_filter == NULL ) {
+		rs.sr_err = LDAP_OTHER;
+		goto done_search;
+	}
+	
+	op->o_callback = &sc;
+	sc.sc_response = vernum_repair_cb;
+	sc.sc_private = &rcb;
+	rcb.bd = &db;
+	db = *be;
+	db.bd_info = (BackendInfo *)on;
+
+	(void)op->o_bd->bd_info->bi_op_search( op, &rs );
+
+	op->o_tag = LDAP_REQ_MODIFY;
+	sc.sc_response = slap_null_cb;
+	sc.sc_private = NULL;
+	memset( &op->oq_modify, 0, sizeof( req_modify_s ) );
+
+	for ( rmod = rcb.mods; rmod != NULL; ) {
+		vernum_mod_t *rnext;
+		Modifications mod;
+		struct berval vals[2] = { BER_BVNULL };
+		SlapReply rs2 = { REP_RESULT };
+
+		mod.sml_flags = SLAP_MOD_INTERNAL;
+		mod.sml_op = LDAP_MOD_REPLACE;
+		mod.sml_desc = vn->vn_vernum;
+		mod.sml_type = vn->vn_vernum->ad_cname;
+		mod.sml_values = vals;
+		mod.sml_values[0] = val_init;
+		mod.sml_nvalues = NULL;
+		mod.sml_numvals = 1;
+		mod.sml_next = NULL;
+
+		op->o_req_dn = rmod->ndn;
+		op->o_req_ndn = rmod->ndn;
+
+		op->orm_modlist = &mod;
+
+		op->o_bd->be_modify( op, &rs2 );
+
+		slap_mods_free( op->orm_modlist->sml_next, 1 );
+		if ( rs2.sr_err == LDAP_SUCCESS ) {
+			Debug( LDAP_DEBUG_TRACE, "%s: vernum_repair: entry DN=\"%s\" repaired\n",
+				op->o_log_prefix, rmod->ndn.bv_val, 0 );
+			nrepaired++;
+
+		} else {
+			Debug( LDAP_DEBUG_ANY, "%s: vernum_repair: entry DN=\"%s\" repair failed (%d)\n",
+				op->o_log_prefix, rmod->ndn.bv_val, rs2.sr_err );
+		}
+
+		rnext = rmod->next;
+		op->o_tmpfree( rmod, op->o_tmpmemctx );
+		rmod = rnext;
+	}
+
+done_search:;
+	op->o_tmpfree( op->ors_filterstr.bv_val, op->o_tmpmemctx );
+	filter_free_x( op, op->ors_filter, 1 );
+
+	Log1( LDAP_DEBUG_STATS, LDAP_LEVEL_INFO,
+		"vernum: repaired=%d\n", nrepaired );
+
+	return 0;
+}
+
+static int
+vernum_db_open(
+	BackendDB	*be,
+	ConfigReply	*cr )
+{
+	slap_overinst *on = (slap_overinst *)be->bd_info;
+	vernum_t *vn = (vernum_t *)on->on_bi.bi_private;
+
+	if ( SLAP_SINGLE_SHADOW( be ) ) {
+		Log1( LDAP_DEBUG_ANY, LDAP_LEVEL_ERR,
+			"vernum incompatible with shadow database \"%s\".\n",
+			be->be_suffix[ 0 ].bv_val );
+		return 1;
+	}
+
+	/* default: unicodePwd & msDS-KeyVersionNumber */
+	if ( vn->vn_attr == NULL ) {
+		const char *text = NULL;
+		int rc;
+
+		rc = slap_str2ad( "unicodePwd", &vn->vn_attr, &text );
+		if ( rc != LDAP_SUCCESS ) {
+			Debug( LDAP_DEBUG_ANY, "vernum: unable to find attribute 'unicodePwd' (%d: %s)\n",
+				rc, text, 0 );
+			return 1;
+		}
+
+		vn->vn_vernum = ad_msDS_KeyVersionNumber;
+	}
+
+	return vernum_repair( be );
+}
+
+static int
+vernum_db_destroy(
+	BackendDB	*be,
+	ConfigReply	*cr )
+{
+	slap_overinst *on = (slap_overinst *)be->bd_info;
+	vernum_t *vn = (vernum_t *)on->on_bi.bi_private;
+
+	if ( vn ) {
+		ch_free( vn );
+		on->on_bi.bi_private = NULL;
+	}
+
+	return 0;
+}
+
+static struct {
+	char	*desc;
+	AttributeDescription **adp;
+} as[] = {
+	{ "( 1.2.840.113556.1.4.1782 "
+		"NAME 'msDS-KeyVersionNumber' "
+		"DESC 'in the original specification the syntax is 2.5.5.9' "
+		"SYNTAX '1.3.6.1.4.1.1466.115.121.1.27' "
+		"EQUALITY integerMatch "
+		"SINGLE-VALUE "
+		"USAGE dSAOperation "
+		"NO-USER-MODIFICATION " 
+		")",
+		&ad_msDS_KeyVersionNumber },
+	{ NULL }
+};
+
+int
+vernum_initialize(void)
+{
+	int code, i;
+
+	for ( i = 0; as[ i ].desc != NULL; i++ ) {
+		code = register_at( as[ i ].desc, as[ i ].adp, 0 );
+		if ( code ) {
+			Debug( LDAP_DEBUG_ANY,
+				"vernum_initialize: register_at #%d failed\n",
+				i, 0, 0 );
+			return code;
+		}
+
+		/* Allow Manager to set these as needed */
+		if ( is_at_no_user_mod( (*as[ i ].adp)->ad_type ) ) {
+			(*as[ i ].adp)->ad_type->sat_flags |=
+				SLAP_AT_MANAGEABLE;
+		}
+	}
+
+	vernum.on_bi.bi_type = "vernum";
+
+	vernum.on_bi.bi_op_add = vernum_op_add;
+	vernum.on_bi.bi_op_modify = vernum_op_modify;
+
+	vernum.on_bi.bi_db_init = vernum_db_init;
+	vernum.on_bi.bi_db_open = vernum_db_open;
+	vernum.on_bi.bi_db_destroy = vernum_db_destroy;
+
+	return overlay_register( &vernum );
+}
+
+#if SLAPD_OVER_VERNUM == SLAPD_MOD_DYNAMIC
+int
+init_module( int argc, char *argv[] )
+{
+	return vernum_initialize();
+}
+#endif /* SLAPD_OVER_VERNUM == SLAPD_MOD_DYNAMIC */
+
+#endif /* SLAPD_OVER_VERNUM */