X-Git-Url: https://git.sur5r.net/?a=blobdiff_plain;f=servers%2Fslapd%2Foverlays%2Fsyncprov.c;h=ad8b9bb329e0b507e54f8dbaf4833156c4058aeb;hb=37d65aed6e108ba43e158121086df6ce0076bd85;hp=d86a7cad6e058f99dd3941f10009dc7a46fb7b55;hpb=aecf0f41643fecb43f08f824f69ee1b734a89d38;p=openldap

diff --git a/servers/slapd/overlays/syncprov.c b/servers/slapd/overlays/syncprov.c
index d86a7cad6e..ad8b9bb329 100644
--- a/servers/slapd/overlays/syncprov.c
+++ b/servers/slapd/overlays/syncprov.c
@@ -2,7 +2,7 @@
 /* syncprov.c - syncrepl provider */
 /* This work is part of OpenLDAP Software <http://www.openldap.org/>.
  *
- * Copyright 2004-2005 The OpenLDAP Foundation.
+ * Copyright 2004-2008 The OpenLDAP Foundation.
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -59,12 +59,14 @@ typedef struct syncops {
 	ID		s_eid;		/* entryID of search base */
 	Operation	*s_op;		/* search op */
 	int		s_rid;
+	int		s_sid;
 	struct berval s_filterstr;
 	int		s_flags;	/* search status */
 #define	PS_IS_REFRESHING	0x01
 #define	PS_IS_DETACHED		0x02
 #define	PS_WROTE_BASE		0x04
 #define	PS_FIND_BASE		0x08
+#define	PS_FIX_FILTER		0x10
 
 	int		s_inuse;	/* reference count */
 	struct syncres *s_res;
@@ -102,6 +104,7 @@ typedef struct slog_entry {
 	struct slog_entry *se_next;
 	struct berval se_uuid;
 	struct berval se_csn;
+	int	se_sid;
 	ber_tag_t	se_tag;
 } slog_entry;
 
@@ -117,7 +120,9 @@ typedef struct sessionlog {
 /* The main state for this overlay */
 typedef struct syncprov_info_t {
 	syncops		*si_ops;
-	struct berval	si_ctxcsn;	/* ldapsync context */
+	BerVarray	si_ctxcsn;	/* ldapsync context */
+	int		*si_sids;
+	int		si_numcsns;
 	int		si_chkops;	/* checkpointing info */
 	int		si_chktime;
 	int		si_numops;	/* number of ops since last checkpoint */
@@ -126,10 +131,9 @@ typedef struct syncprov_info_t {
 	time_t	si_chklast;	/* time of last checkpoint */
 	Avlnode	*si_mods;	/* entries being modified */
 	sessionlog	*si_logs;
-	ldap_pvt_thread_mutex_t	si_csn_mutex;
+	ldap_pvt_thread_rdwr_t	si_csn_rwlock;
 	ldap_pvt_thread_mutex_t	si_ops_mutex;
 	ldap_pvt_thread_mutex_t	si_mods_mutex;
-	char		si_ctxcsnbuf[LDAP_LUTIL_CSNSTR_BUFSIZE];
 } syncprov_info_t;
 
 typedef struct opcookie {
@@ -400,6 +404,7 @@ syncprov_findbase( Operation *op, fbase_cookie *fc )
 		slap_callback cb = {0};
 		Operation fop;
 		SlapReply frs = { REP_RESULT };
+		BackendInfo *bi;
 		int rc;
 
 		fc->fss->s_flags ^= PS_FIND_BASE;
@@ -411,6 +416,7 @@ syncprov_findbase( Operation *op, fbase_cookie *fc )
 		fop.o_bd = op->o_bd;
 		fop.o_time = op->o_time;
 		fop.o_tincr = op->o_tincr;
+		bi = op->o_bd->bd_info;
 
 		cb.sc_response = findbase_cb;
 		cb.sc_private = fc;
@@ -428,9 +434,8 @@ syncprov_findbase( Operation *op, fbase_cookie *fc )
 		fop.ors_filter = &generic_filter;
 		fop.ors_filterstr = generic_filterstr;
 
-		fop.o_bd->bd_info = on->on_info->oi_orig;
-		rc = fop.o_bd->be_search( &fop, &frs );
-		fop.o_bd->bd_info = (BackendInfo *)on;
+		rc = overlay_op_walk( &fop, &frs, op_search, on->on_info, on );
+		op->o_bd->bd_info = bi;
 	} else {
 		ldap_pvt_thread_mutex_unlock( &fc->fss->s_mutex );
 		fc->fbase = 1;
@@ -579,23 +584,16 @@ syncprov_findcsn( Operation *op, find_csn_t mode )
 	char buf[LDAP_LUTIL_CSNSTR_BUFSIZE + STRLENOF("(entryCSN<=)")];
 	char cbuf[LDAP_LUTIL_CSNSTR_BUFSIZE];
 	struct berval maxcsn;
-	Filter cf, af;
-#ifdef LDAP_COMP_MATCH
-	AttributeAssertion eq = { NULL, BER_BVNULL, NULL };
-#else
-	AttributeAssertion eq = { NULL, BER_BVNULL };
-#endif
+	Filter cf;
+	AttributeAssertion eq = ATTRIBUTEASSERTION_INIT;
 	fpres_cookie pcookie;
 	sync_control *srs = NULL;
 	struct slap_limits_set fc_limits;
 	int i, rc = LDAP_SUCCESS, findcsn_retry = 1;
+	int maxid = 0;
 
 	if ( mode != FIND_MAXCSN ) {
 		srs = op->o_controls[slap_cids.sc_LDAPsync];
-
-		if ( srs->sr_state.ctxcsn.bv_len >= LDAP_LUTIL_CSNSTR_BUFSIZE ) {
-			return LDAP_OTHER;
-		}
 	}
 
 	fop = *op;
@@ -605,6 +603,7 @@ syncprov_findcsn( Operation *op, find_csn_t mode )
 
 	cf.f_ava = &eq;
 	cf.f_av_desc = slap_schema.si_ad_entryCSN;
+	BER_BVZERO( &cf.f_av_value );
 	cf.f_next = NULL;
 
 	fop.o_callback = &cb;
@@ -617,32 +616,55 @@ again:
 	switch( mode ) {
 	case FIND_MAXCSN:
 		cf.f_choice = LDAP_FILTER_GE;
-		cf.f_av_value = si->si_ctxcsn;
-		fop.ors_filterstr.bv_len = sprintf( buf, "(entryCSN>=%s)",
-			cf.f_av_value.bv_val );
+		cf.f_av_value = si->si_ctxcsn[0];
+		/* If there are multiple CSNs, use the largest */
+		for ( i=1; i<si->si_numcsns; i++) {
+			if ( ber_bvcmp( &cf.f_av_value, &si->si_ctxcsn[i] ) < 0 ) {
+				cf.f_av_value = si->si_ctxcsn[i];
+				maxid = i;
+			}
+		}
+		fop.ors_filterstr.bv_len = snprintf( buf, sizeof( buf ),
+			"(entryCSN>=%s)", cf.f_av_value.bv_val );
+		if ( fop.ors_filterstr.bv_len < 0 || fop.ors_filterstr.bv_len >= sizeof( buf ) ) {
+			return LDAP_OTHER;
+		}
 		fop.ors_attrsonly = 0;
 		fop.ors_attrs = csn_anlist;
 		fop.ors_slimit = SLAP_NO_LIMIT;
 		cb.sc_private = &maxcsn;
 		cb.sc_response = findmax_cb;
-		strcpy( cbuf, si->si_ctxcsn.bv_val );
+		strcpy( cbuf, cf.f_av_value.bv_val );
 		maxcsn.bv_val = cbuf;
-		maxcsn.bv_len = si->si_ctxcsn.bv_len;
+		maxcsn.bv_len = cf.f_av_value.bv_len;
 		break;
 	case FIND_CSN:
-		cf.f_av_value = srs->sr_state.ctxcsn;
+		if ( BER_BVISEMPTY( &cf.f_av_value )) {
+			cf.f_av_value = srs->sr_state.ctxcsn[0];
+			/* If there are multiple CSNs, use the smallest */
+			for ( i=1; i<srs->sr_state.numcsns; i++ ) {
+				if ( ber_bvcmp( &cf.f_av_value, &srs->sr_state.ctxcsn[i] )
+					> 0 ) {
+					cf.f_av_value = srs->sr_state.ctxcsn[i];
+				}
+			}
+		}
 		/* Look for exact match the first time */
 		if ( findcsn_retry ) {
 			cf.f_choice = LDAP_FILTER_EQUALITY;
-			fop.ors_filterstr.bv_len = sprintf( buf, "(entryCSN=%s)",
-				cf.f_av_value.bv_val );
+			fop.ors_filterstr.bv_len = snprintf( buf, sizeof( buf ),
+				"(entryCSN=%s)", cf.f_av_value.bv_val );
 		/* On retry, look for <= */
 		} else {
 			cf.f_choice = LDAP_FILTER_LE;
 			fop.ors_limit = &fc_limits;
+			memset( &fc_limits, 0, sizeof( fc_limits ));
 			fc_limits.lms_s_unchecked = 1;
-			fop.ors_filterstr.bv_len = sprintf( buf, "(entryCSN<=%s)",
-				cf.f_av_value.bv_val );
+			fop.ors_filterstr.bv_len = snprintf( buf, sizeof( buf ),
+				"(entryCSN<=%s)", cf.f_av_value.bv_val );
+		}
+		if ( fop.ors_filterstr.bv_len < 0 || fop.ors_filterstr.bv_len >= sizeof( buf ) ) {
+			return LDAP_OTHER;
 		}
 		fop.ors_attrsonly = 1;
 		fop.ors_attrs = slap_anlist_no_attrs;
@@ -651,14 +673,8 @@ again:
 		cb.sc_response = findcsn_cb;
 		break;
 	case FIND_PRESENT:
-		af.f_choice = LDAP_FILTER_AND;
-		af.f_next = NULL;
-		af.f_and = &cf;
-		cf.f_choice = LDAP_FILTER_LE;
-		cf.f_av_value = srs->sr_state.ctxcsn;
-		cf.f_next = op->ors_filter;
-		fop.ors_filter = &af;
-		filter2bv_x( &fop, fop.ors_filter, &fop.ors_filterstr );
+		fop.ors_filter = op->ors_filter;
+		fop.ors_filterstr = op->ors_filterstr;
 		fop.ors_attrsonly = 0;
 		fop.ors_attrs = uuid_anlist;
 		fop.ors_slimit = SLAP_NO_LIMIT;
@@ -686,8 +702,10 @@ again:
 
 	switch( mode ) {
 	case FIND_MAXCSN:
-		strcpy( si->si_ctxcsnbuf, maxcsn.bv_val );
-		si->si_ctxcsn.bv_len = maxcsn.bv_len;
+		if ( ber_bvcmp( &si->si_ctxcsn[maxid], &maxcsn )) {
+			ber_bvreplace( &si->si_ctxcsn[maxid], &maxcsn );
+			si->si_numops++;	/* ensure a checkpoint */
+		}
 		break;
 	case FIND_CSN:
 		/* If matching CSN was not found, invalidate the context. */
@@ -702,7 +720,6 @@ again:
 		break;
 	case FIND_PRESENT:
 		op->o_tmpfree( pcookie.uuids, op->o_tmpmemctx );
-		op->o_tmpfree( fop.ors_filterstr.bv_val, op->o_tmpmemctx );
 		break;
 	}
 
@@ -747,7 +764,7 @@ syncprov_sendresp( Operation *op, opcookie *opc, syncops *so,
 
 	SlapReply rs = { REP_SEARCH };
 	LDAPControl *ctrls[2];
-	struct berval cookie;
+	struct berval cookie, csns[2];
 	Entry e_uuid = {0};
 	Attribute a_uuid = {0};
 
@@ -755,7 +772,11 @@ syncprov_sendresp( Operation *op, opcookie *opc, syncops *so,
 		return SLAPD_ABANDON;
 
 	ctrls[1] = NULL;
-	slap_compose_sync_cookie( op, &cookie, &opc->sctxcsn, so->s_rid );
+	csns[0] = opc->sctxcsn;
+	BER_BVZERO( &csns[1] );
+	slap_compose_sync_cookie( op, &cookie, csns, so->s_rid, so->s_sid );
+
+	Debug( LDAP_DEBUG_SYNC, "syncprov_sendresp: cookie=%s\n", cookie.bv_val, 0, 0 );
 
 	e_uuid.e_attrs = &a_uuid;
 	a_uuid.a_desc = slap_schema.si_ad_entryUUID;
@@ -773,7 +794,7 @@ syncprov_sendresp( Operation *op, opcookie *opc, syncops *so,
 			rs.sr_flags = REP_ENTRY_MUSTRELEASE;
 		if ( opc->sreference ) {
 			rs.sr_ref = get_entry_referrals( op, rs.sr_entry );
-			send_search_reference( op, &rs );
+			rs.sr_err = send_search_reference( op, &rs );
 			ber_bvarray_free( rs.sr_ref );
 			if ( !rs.sr_entry )
 				*e = NULL;
@@ -785,7 +806,7 @@ syncprov_sendresp( Operation *op, opcookie *opc, syncops *so,
 		if ( rs.sr_entry->e_private )
 			rs.sr_flags = REP_ENTRY_MUSTRELEASE;
 		rs.sr_attrs = op->ors_attrs;
-		send_search_entry( op, &rs );
+		rs.sr_err = send_search_entry( op, &rs );
 		if ( !rs.sr_entry )
 			*e = NULL;
 		break;
@@ -797,9 +818,9 @@ syncprov_sendresp( Operation *op, opcookie *opc, syncops *so,
 		if ( opc->sreference ) {
 			struct berval bv = BER_BVNULL;
 			rs.sr_ref = &bv;
-			send_search_reference( op, &rs );
+			rs.sr_err = send_search_reference( op, &rs );
 		} else {
-			send_search_entry( op, &rs );
+			rs.sr_err = send_search_entry( op, &rs );
 		}
 		break;
 	default:
@@ -821,10 +842,9 @@ syncprov_qplay( Operation *op, slap_overinst *on, syncops *so )
 	syncres *sr;
 	Entry *e;
 	opcookie opc;
-	int rc;
+	int rc = 0;
 
 	opc.son = on;
-	op->o_bd->bd_info = (BackendInfo *)on->on_info;
 
 	for (;;) {
 		ldap_pvt_thread_mutex_lock( &so->s_mutex );
@@ -846,16 +866,19 @@ syncprov_qplay( Operation *op, slap_overinst *on, syncops *so )
 		e = NULL;
 
 		if ( sr->s_mode != LDAP_SYNC_DELETE ) {
-			rc = be_entry_get_rw( op, &opc.sndn, NULL, NULL, 0, &e );
+			rc = overlay_entry_get_ov( op, &opc.sndn, NULL, NULL, 0, &e, on );
 			if ( rc ) {
+				Debug( LDAP_DEBUG_SYNC, "syncprov_qplay: failed to get %s, "
+					"error (%d), ignoring...\n", opc.sndn.bv_val, rc, 0 );
 				ch_free( sr );
+				rc = 0;
 				continue;
 			}
 		}
 		rc = syncprov_sendresp( op, &opc, so, &e, sr->s_mode );
 
 		if ( e ) {
-			be_entry_release_rw( op, e, 0 );
+			overlay_entry_release_ov( op, e, 0, on );
 		}
 
 		ch_free( sr );
@@ -863,7 +886,6 @@ syncprov_qplay( Operation *op, slap_overinst *on, syncops *so )
 		if ( rc )
 			break;
 	}
-	op->o_bd->bd_info = (BackendInfo *)on;
 	return rc;
 }
 
@@ -877,16 +899,17 @@ syncprov_qtask( void *ctx, void *arg )
 	OperationBuffer opbuf;
 	Operation *op;
 	BackendDB be;
+	int rc;
 
-	op = (Operation *) &opbuf;
+	op = &opbuf.ob_op;
 	*op = *so->s_op;
-	op->o_hdr = (Opheader *)(op+1);
-	op->o_controls = (void **)(op->o_hdr+1);
-	memset( op->o_controls, 0, SLAP_MAX_CIDS * sizeof(void *));
+	op->o_hdr = &opbuf.ob_hdr;
+	op->o_controls = opbuf.ob_controls;
+	memset( op->o_controls, 0, sizeof(opbuf.ob_controls) );
 
 	*op->o_hdr = *so->s_op->o_hdr;
 
-	op->o_tmpmemctx = slap_sl_mem_create(SLAP_SLAB_SIZE, SLAP_SLAB_STACK, ctx);
+	op->o_tmpmemctx = slap_sl_mem_create(SLAP_SLAB_SIZE, SLAP_SLAB_STACK, ctx, 1);
 	op->o_tmpmfuncs = &slap_sl_mfuncs;
 	op->o_threadctx = ctx;
 
@@ -897,28 +920,80 @@ syncprov_qtask( void *ctx, void *arg )
 	op->o_private = NULL;
 	op->o_callback = NULL;
 
-	syncprov_qplay( op, on, so );
+	rc = syncprov_qplay( op, on, so );
 
 	/* decrement use count... */
 	syncprov_free_syncop( so );
 
 	/* wait until we get explicitly scheduled again */
 	ldap_pvt_thread_mutex_lock( &slapd_rq.rq_mutex );
-	ldap_pvt_runqueue_stoptask( &slapd_rq, so->s_qtask );
-	ldap_pvt_runqueue_resched( &slapd_rq, so->s_qtask, 1 );
+	ldap_pvt_runqueue_stoptask( &slapd_rq, rtask );
+	if ( rc == 0 ) {
+		ldap_pvt_runqueue_resched( &slapd_rq, rtask, 1 );
+	} else {
+		/* bail out on any error */
+		ldap_pvt_runqueue_remove( &slapd_rq, rtask );
+	}
 	ldap_pvt_thread_mutex_unlock( &slapd_rq.rq_mutex );
 
+#if 0	/* FIXME: connection_close isn't exported from slapd.
+		 * should it be?
+		 */
+	if ( rc ) {
+		ldap_pvt_thread_mutex_lock( &op->o_conn->c_mutex );
+		if ( connection_state_closing( op->o_conn )) {
+			connection_close( op->o_conn );
+		}
+		ldap_pvt_thread_mutex_unlock( &op->o_conn->c_mutex );
+	}
+#endif
 	return NULL;
 }
 
+/* Start the task to play back queued psearch responses */
+static void
+syncprov_qstart( syncops *so )
+{
+	int wake=0;
+	ldap_pvt_thread_mutex_lock( &slapd_rq.rq_mutex );
+	if ( !so->s_qtask ) {
+		so->s_qtask = ldap_pvt_runqueue_insert( &slapd_rq, RUNQ_INTERVAL,
+			syncprov_qtask, so, "syncprov_qtask",
+			so->s_op->o_conn->c_peer_name.bv_val );
+		++so->s_inuse;
+		wake = 1;
+	} else {
+		if (!ldap_pvt_runqueue_isrunning( &slapd_rq, so->s_qtask ) &&
+			!so->s_qtask->next_sched.tv_sec ) {
+			so->s_qtask->interval.tv_sec = 0;
+			ldap_pvt_runqueue_resched( &slapd_rq, so->s_qtask, 0 );
+			so->s_qtask->interval.tv_sec = RUNQ_INTERVAL;
+			++so->s_inuse;
+			wake = 1;
+		}
+	}
+	ldap_pvt_thread_mutex_unlock( &slapd_rq.rq_mutex );
+	if ( wake )
+		slap_wake_listener();
+}
+
 /* Queue a persistent search response */
 static int
 syncprov_qresp( opcookie *opc, syncops *so, int mode )
 {
 	syncres *sr;
+	int sid, srsize;
 
-	sr = ch_malloc(sizeof(syncres) + opc->suuid.bv_len + 1 +
-		opc->sdn.bv_len + 1 + opc->sndn.bv_len + 1 + opc->sctxcsn.bv_len + 1 );
+	/* Don't send changes back to their originator */
+	sid = slap_parse_csn_sid( &opc->sctxcsn );
+	if ( sid >= 0 && sid == so->s_sid )
+		return LDAP_SUCCESS;
+
+	srsize = sizeof(syncres) + opc->suuid.bv_len + 1 +
+		opc->sdn.bv_len + 1 + opc->sndn.bv_len + 1;
+	if ( opc->sctxcsn.bv_len )
+		srsize += opc->sctxcsn.bv_len + 1;
+	sr = ch_malloc( srsize );
 	sr->s_next = NULL;
 	sr->s_dn.bv_val = (char *)(sr + 1);
 	sr->s_dn.bv_len = opc->sdn.bv_len;
@@ -931,9 +1006,13 @@ syncprov_qresp( opcookie *opc, syncops *so, int mode )
 		 opc->sndn.bv_val ) + 1;
 	sr->s_uuid.bv_len = opc->suuid.bv_len;
 	AC_MEMCPY( sr->s_uuid.bv_val, opc->suuid.bv_val, opc->suuid.bv_len );
-	sr->s_csn.bv_val = sr->s_uuid.bv_val + sr->s_uuid.bv_len + 1;
+	if ( opc->sctxcsn.bv_len ) {
+		sr->s_csn.bv_val = sr->s_uuid.bv_val + sr->s_uuid.bv_len + 1;
+		strcpy( sr->s_csn.bv_val, opc->sctxcsn.bv_val );
+	} else {
+		sr->s_csn.bv_val = NULL;
+	}
 	sr->s_csn.bv_len = opc->sctxcsn.bv_len;
-	strcpy( sr->s_csn.bv_val, opc->sctxcsn.bv_val );
 
 	ldap_pvt_thread_mutex_lock( &so->s_mutex );
 	if ( !so->s_res ) {
@@ -949,22 +1028,7 @@ syncprov_qresp( opcookie *opc, syncops *so, int mode )
 		so->s_flags |= PS_FIND_BASE;
 	}
 	if ( so->s_flags & PS_IS_DETACHED ) {
-		ldap_pvt_thread_mutex_lock( &slapd_rq.rq_mutex );
-		if ( !so->s_qtask ) {
-			so->s_qtask = ldap_pvt_runqueue_insert( &slapd_rq, RUNQ_INTERVAL,
-				syncprov_qtask, so, "syncprov_qtask",
-				so->s_op->o_conn->c_peer_name.bv_val );
-			++so->s_inuse;
-		} else {
-			if (!ldap_pvt_runqueue_isrunning( &slapd_rq, so->s_qtask ) &&
-				!so->s_qtask->next_sched.tv_sec ) {
-				so->s_qtask->interval.tv_sec = 0;
-				ldap_pvt_runqueue_resched( &slapd_rq, so->s_qtask, 0 );
-				so->s_qtask->interval.tv_sec = RUNQ_INTERVAL;
-				++so->s_inuse;
-			}
-		}
-		ldap_pvt_thread_mutex_unlock( &slapd_rq.rq_mutex );
+		syncprov_qstart( so );
 	}
 	ldap_pvt_thread_mutex_unlock( &so->s_mutex );
 	return LDAP_SUCCESS;
@@ -978,7 +1042,7 @@ syncprov_drop_psearch( syncops *so, int lock )
 			ldap_pvt_thread_mutex_lock( &so->s_op->o_conn->c_mutex );
 		so->s_op->o_conn->c_n_ops_executing--;
 		so->s_op->o_conn->c_n_ops_completed++;
-		LDAP_STAILQ_REMOVE( &so->s_op->o_conn->c_ops, so->s_op, slap_op,
+		LDAP_STAILQ_REMOVE( &so->s_op->o_conn->c_ops, so->s_op, Operation,
 			o_next );
 		if ( lock )
 			ldap_pvt_thread_mutex_unlock( &so->s_op->o_conn->c_mutex );
@@ -1045,11 +1109,12 @@ syncprov_matchops( Operation *op, opcookie *opc, int saveit )
 
 	fbase_cookie fc;
 	syncops *ss, *sprev, *snext;
-	Entry *e;
+	Entry *e = NULL;
 	Attribute *a;
 	int rc;
 	struct berval newdn;
 	int freefdn = 0;
+	BackendDB *b0 = op->o_bd, db;
 
 	fc.fdn = &op->o_req_ndn;
 	/* compute new DN */
@@ -1062,16 +1127,21 @@ syncprov_matchops( Operation *op, opcookie *opc, int saveit )
 		freefdn = 1;
 	}
 	if ( op->o_tag != LDAP_REQ_ADD ) {
-		op->o_bd->bd_info = (BackendInfo *)on->on_info;
-		rc = be_entry_get_rw( op, fc.fdn, NULL, NULL, 0, &e );
+		if ( !SLAP_ISOVERLAY( op->o_bd )) {
+			db = *op->o_bd;
+			op->o_bd = &db;
+		}
+		rc = overlay_entry_get_ov( op, fc.fdn, NULL, NULL, 0, &e, on );
 		/* If we're sending responses now, make a copy and unlock the DB */
 		if ( e && !saveit ) {
 			Entry *e2 = entry_dup( e );
-			be_entry_release_rw( op, e, 0 );
+			overlay_entry_release_ov( op, e, 0, on );
 			e = e2;
 		}
-		op->o_bd->bd_info = (BackendInfo *)on;
-		if ( rc ) return;
+		if ( rc ) {
+			op->o_bd = b0;
+			return;
+		}
 	} else {
 		e = op->ora_e;
 	}
@@ -1162,13 +1232,16 @@ syncprov_matchops( Operation *op, opcookie *opc, int saveit )
 	ldap_pvt_thread_mutex_unlock( &si->si_ops_mutex );
 
 	if ( op->o_tag != LDAP_REQ_ADD && e ) {
-		op->o_bd->bd_info = (BackendInfo *)on->on_info;
-		be_entry_release_rw( op, e, 0 );
-		op->o_bd->bd_info = (BackendInfo *)on;
+		if ( !SLAP_ISOVERLAY( op->o_bd )) {
+			op->o_bd = &db;
+		}
+		overlay_entry_release_ov( op, e, 0, on );
+		op->o_bd = b0;
 	}
 	if ( freefdn ) {
 		op->o_tmpfree( fc.fdn->bv_val, op->o_tmpmemctx );
 	}
+	op->o_bd = b0;
 }
 
 static int
@@ -1223,16 +1296,14 @@ syncprov_op_cleanup( Operation *op, SlapReply *rs )
 static void
 syncprov_checkpoint( Operation *op, SlapReply *rs, slap_overinst *on )
 {
-	syncprov_info_t		*si = on->on_bi.bi_private;
+	syncprov_info_t *si = (syncprov_info_t *)on->on_bi.bi_private;
 	Modifications mod;
 	Operation opm;
 	SlapReply rsm = { 0 };
-	struct berval bv[2];
 	slap_callback cb = {0};
 
-	mod.sml_values = bv;
-	bv[1].bv_val = NULL;
-	bv[0] = si->si_ctxcsn;
+	mod.sml_numvals = si->si_numcsns;
+	mod.sml_values = si->si_ctxcsn;
 	mod.sml_nvalues = NULL;
 	mod.sml_desc = slap_schema.si_ad_contextCSN;
 	mod.sml_op = LDAP_MOD_REPLACE;
@@ -1244,20 +1315,21 @@ syncprov_checkpoint( Operation *op, SlapReply *rs, slap_overinst *on )
 	opm.o_tag = LDAP_REQ_MODIFY;
 	opm.o_callback = &cb;
 	opm.orm_modlist = &mod;
+	opm.orm_no_opattrs = 1;
 	opm.o_req_dn = op->o_bd->be_suffix[0];
 	opm.o_req_ndn = op->o_bd->be_nsuffix[0];
 	opm.o_bd->bd_info = on->on_info->oi_orig;
 	opm.o_managedsait = SLAP_CONTROL_NONCRITICAL;
-	SLAP_DBFLAGS( opm.o_bd ) |= SLAP_DBFLAG_NOLASTMOD;
+	opm.o_no_schema_check = 1;
 	opm.o_bd->be_modify( &opm, &rsm );
-	SLAP_DBFLAGS( opm.o_bd ) ^= SLAP_DBFLAG_NOLASTMOD;
 	if ( mod.sml_next != NULL ) {
 		slap_mods_free( mod.sml_next, 1 );
 	}
+	opm.orm_no_opattrs = 0;
 }
 
 static void
-syncprov_add_slog( Operation *op, struct berval *csn )
+syncprov_add_slog( Operation *op )
 {
 	opcookie *opc = op->o_callback->sc_private;
 	slap_overinst *on = opc->son;
@@ -1269,18 +1341,19 @@ syncprov_add_slog( Operation *op, struct berval *csn )
 	{
 		/* Allocate a record. UUIDs are not NUL-terminated. */
 		se = ch_malloc( sizeof( slog_entry ) + opc->suuid.bv_len + 
-			csn->bv_len + 1 );
+			op->o_csn.bv_len + 1 );
 		se->se_next = NULL;
 		se->se_tag = op->o_tag;
 
-		se->se_uuid.bv_val = (char *)(se+1);
+		se->se_uuid.bv_val = (char *)(&se[1]);
 		AC_MEMCPY( se->se_uuid.bv_val, opc->suuid.bv_val, opc->suuid.bv_len );
 		se->se_uuid.bv_len = opc->suuid.bv_len;
 
 		se->se_csn.bv_val = se->se_uuid.bv_val + opc->suuid.bv_len;
-		AC_MEMCPY( se->se_csn.bv_val, csn->bv_val, csn->bv_len );
-		se->se_csn.bv_val[csn->bv_len] = '\0';
-		se->se_csn.bv_len = csn->bv_len;
+		AC_MEMCPY( se->se_csn.bv_val, op->o_csn.bv_val, op->o_csn.bv_len );
+		se->se_csn.bv_val[op->o_csn.bv_len] = '\0';
+		se->se_csn.bv_len = op->o_csn.bv_len;
+		se->se_sid = slap_parse_csn_sid( &se->se_csn );
 
 		ldap_pvt_thread_mutex_lock( &sl->sl_mutex );
 		if ( sl->sl_head ) {
@@ -1297,9 +1370,6 @@ syncprov_add_slog( Operation *op, struct berval *csn )
 			sl->sl_mincsn.bv_len = se->se_csn.bv_len;
 			ch_free( se );
 			sl->sl_num--;
-			if ( !sl->sl_head ) {
-				sl->sl_tail = NULL;
-			}
 		}
 		ldap_pvt_thread_mutex_unlock( &sl->sl_mutex );
 	}
@@ -1318,12 +1388,14 @@ playlog_cb( Operation *op, SlapReply *rs )
 /* enter with sl->sl_mutex locked, release before returning */
 static void
 syncprov_playlog( Operation *op, SlapReply *rs, sessionlog *sl,
-	struct berval *oldcsn, struct berval *ctxcsn )
+	sync_control *srs, BerVarray ctxcsn, int numcsns, int *sids )
 {
 	slap_overinst		*on = (slap_overinst *)op->o_bd->bd_info;
 	slog_entry *se;
 	int i, j, ndel, num, nmods, mmods;
+	char cbuf[LDAP_LUTIL_CSNSTR_BUFSIZE];
 	BerVarray uuids;
+	struct berval delcsn[2];
 
 	if ( !sl->sl_num ) {
 		ldap_pvt_thread_mutex_unlock( &sl->sl_mutex );
@@ -1336,19 +1408,49 @@ syncprov_playlog( Operation *op, SlapReply *rs, sessionlog *sl,
 
 	uuids = op->o_tmpalloc( (num+1) * sizeof( struct berval ) +
 		num * UUID_LEN, op->o_tmpmemctx );
-
 	uuids[0].bv_val = (char *)(uuids + num + 1);
 
+	delcsn[0].bv_len = 0;
+	delcsn[0].bv_val = cbuf;
+	BER_BVZERO(&delcsn[1]);
+
 	/* Make a copy of the relevant UUIDs. Put the Deletes up front
 	 * and everything else at the end. Do this first so we can
 	 * unlock the list mutex.
 	 */
+	Debug( LDAP_DEBUG_SYNC, "srs csn %s\n",
+		srs->sr_state.ctxcsn[0].bv_val, 0, 0 );
 	for ( se=sl->sl_head; se; se=se->se_next ) {
-		if ( ber_bvcmp( &se->se_csn, oldcsn ) < 0 ) continue;
-		if ( ber_bvcmp( &se->se_csn, ctxcsn ) > 0 ) break;
+		int k;
+		Debug( LDAP_DEBUG_SYNC, "log csn %s\n", se->se_csn.bv_val, 0, 0 );
+		ndel = 1;
+		for ( k=0; k<srs->sr_state.numcsns; k++ ) {
+			if ( se->se_sid == srs->sr_state.sids[k] ) {
+				ndel = ber_bvcmp( &se->se_csn, &srs->sr_state.ctxcsn[k] );
+				break;
+			}
+		}
+		if ( ndel <= 0 ) {
+			Debug( LDAP_DEBUG_SYNC, "cmp %d, too old\n", ndel, 0, 0 );
+			continue;
+		}
+		ndel = 0;
+		for ( k=0; k<numcsns; k++ ) {
+			if ( se->se_sid == sids[k] ) {
+				ndel = ber_bvcmp( &se->se_csn, &ctxcsn[k] );
+				break;
+			}
+		}
+		if ( ndel > 0 ) {
+			Debug( LDAP_DEBUG_SYNC, "cmp %d, too new\n", ndel, 0, 0 );
+			break;
+		}
 		if ( se->se_tag == LDAP_REQ_DELETE ) {
 			j = i;
 			i++;
+			AC_MEMCPY( cbuf, se->se_csn.bv_val, se->se_csn.bv_len );
+			delcsn[0].bv_len = se->se_csn.bv_len;
+			delcsn[0].bv_val[delcsn[0].bv_len] = '\0';
 		} else {
 			nmods++;
 			j = num - nmods;
@@ -1393,11 +1495,7 @@ syncprov_playlog( Operation *op, SlapReply *rs, sessionlog *sl,
 		SlapReply frs = { REP_RESULT };
 		int rc;
 		Filter mf, af;
-#ifdef LDAP_COMP_MATCH
-		AttributeAssertion eq = { NULL, BER_BVNULL, NULL };
-#else
-		AttributeAssertion eq;
-#endif
+		AttributeAssertion eq = ATTRIBUTEASSERTION_INIT;
 		slap_callback cb = {0};
 
 		fop = *op;
@@ -1429,6 +1527,7 @@ syncprov_playlog( Operation *op, SlapReply *rs, sessionlog *sl,
 			mf.f_av_value = uuids[i];
 			cb.sc_private = NULL;
 			fop.ors_slimit = 1;
+			frs.sr_nentries = 0;
 			rc = fop.o_bd->be_search( &fop, &frs );
 
 			/* If entry was not found, add to delete list */
@@ -1439,9 +1538,18 @@ syncprov_playlog( Operation *op, SlapReply *rs, sessionlog *sl,
 		fop.o_bd->bd_info = (BackendInfo *)on;
 	}
 	if ( ndel ) {
+		struct berval cookie;
+
+		slap_compose_sync_cookie( op, &cookie, delcsn, srs->sr_state.rid,
+			srs->sr_state.sid );
+
+		Debug( LDAP_DEBUG_SYNC, "syncprov_playlog: cookie=%s\n", cookie.bv_val, 0, 0 );
+
 		uuids[ndel].bv_val = NULL;
-		syncprov_sendinfo( op, rs, LDAP_TAG_SYNC_ID_SET, NULL, 0, uuids, 1 );
+		syncprov_sendinfo( op, rs, LDAP_TAG_SYNC_ID_SET, &cookie, 0, uuids, 1 );
+		op->o_tmpfree( cookie.bv_val, op->o_tmpmemctx );
 	}
+	op->o_tmpfree( uuids, op->o_tmpmemctx );
 }
 
 static int
@@ -1454,51 +1562,75 @@ syncprov_op_response( Operation *op, SlapReply *rs )
 
 	if ( rs->sr_err == LDAP_SUCCESS )
 	{
-		struct berval maxcsn = BER_BVNULL, curcsn = BER_BVNULL;
+		struct berval maxcsn = BER_BVNULL;
 		char cbuf[LDAP_LUTIL_CSNSTR_BUFSIZE];
+		int do_check = 0, have_psearches;
 
 		/* Update our context CSN */
 		cbuf[0] = '\0';
-		ldap_pvt_thread_mutex_lock( &si->si_csn_mutex );
-		slap_get_commit_csn( op, &maxcsn, &curcsn );
+		ldap_pvt_thread_rdwr_wlock( &si->si_csn_rwlock );
+		slap_get_commit_csn( op, &maxcsn );
 		if ( !BER_BVISNULL( &maxcsn ) ) {
+			int i, sid;
 			strcpy( cbuf, maxcsn.bv_val );
-			if ( ber_bvcmp( &maxcsn, &si->si_ctxcsn ) > 0 ) {
-				strcpy( si->si_ctxcsnbuf, cbuf );
-				si->si_ctxcsn.bv_len = maxcsn.bv_len;
+			sid = slap_parse_csn_sid( &maxcsn );
+			for ( i=0; i<si->si_numcsns; i++ ) {
+				if ( sid == si->si_sids[i] ) {
+					if ( ber_bvcmp( &maxcsn, &si->si_ctxcsn[i] ) > 0 ) {
+						ber_bvreplace( &si->si_ctxcsn[i], &maxcsn );
+					}
+					break;
+				}
+			}
+			/* It's a new SID for us */
+			if ( i == si->si_numcsns ) {
+				value_add_one( &si->si_ctxcsn, &maxcsn );
+				si->si_numcsns++;
+				si->si_sids = ch_realloc( si->si_sids, si->si_numcsns *
+					sizeof(int));
+				si->si_sids[i] = sid;
 			}
 		}
 
 		/* Don't do any processing for consumer contextCSN updates */
 		if ( SLAP_SYNC_SHADOW( op->o_bd ) && 
 			op->o_msgid == SLAP_SYNC_UPDATE_MSGID ) {
-			ldap_pvt_thread_mutex_unlock( &si->si_csn_mutex );
+			ldap_pvt_thread_rdwr_wunlock( &si->si_csn_rwlock );
 			return SLAP_CB_CONTINUE;
 		}
 
 		si->si_numops++;
 		if ( si->si_chkops || si->si_chktime ) {
-			int do_check=0;
 			if ( si->si_chkops && si->si_numops >= si->si_chkops ) {
 				do_check = 1;
 				si->si_numops = 0;
 			}
 			if ( si->si_chktime &&
 				(op->o_time - si->si_chklast >= si->si_chktime )) {
-				do_check = 1;
-				si->si_chklast = op->o_time;
-			}
-			if ( do_check ) {
-				syncprov_checkpoint( op, rs, on );
+				if ( si->si_chklast ) {
+					do_check = 1;
+					si->si_chklast = op->o_time;
+				} else {
+					si->si_chklast = 1;
+				}
 			}
 		}
-		ldap_pvt_thread_mutex_unlock( &si->si_csn_mutex );
+		ldap_pvt_thread_rdwr_wunlock( &si->si_csn_rwlock );
+
+		if ( do_check ) {
+			ldap_pvt_thread_rdwr_rlock( &si->si_csn_rwlock );
+			syncprov_checkpoint( op, rs, on );
+			ldap_pvt_thread_rdwr_runlock( &si->si_csn_rwlock );
+		}
 
 		opc->sctxcsn.bv_len = maxcsn.bv_len;
 		opc->sctxcsn.bv_val = cbuf;
 
 		/* Handle any persistent searches */
-		if ( si->si_ops ) {
+		ldap_pvt_thread_mutex_lock( &si->si_ops_mutex );
+		have_psearches = ( si->si_ops != NULL );
+		ldap_pvt_thread_mutex_unlock( &si->si_ops_mutex );
+		if ( have_psearches ) {
 			switch(op->o_tag) {
 			case LDAP_REQ_ADD:
 			case LDAP_REQ_MODIFY:
@@ -1521,7 +1653,7 @@ syncprov_op_response( Operation *op, SlapReply *rs )
 
 		/* Add any log records */
 		if ( si->si_logs && op->o_tag != LDAP_REQ_ADD ) {
-			syncprov_add_slog( op, &curcsn );
+			syncprov_add_slog( op );
 		}
 
 	}
@@ -1544,19 +1676,17 @@ syncprov_op_compare( Operation *op, SlapReply *rs )
 	{
 		Entry e = {0};
 		Attribute a = {0};
-		struct berval bv[2];
 
 		e.e_name = op->o_bd->be_suffix[0];
 		e.e_nname = op->o_bd->be_nsuffix[0];
-
-		BER_BVZERO( &bv[1] );
-		bv[0] = si->si_ctxcsn;
+		e.e_attrs = &a;
 
 		a.a_desc = slap_schema.si_ad_contextCSN;
-		a.a_vals = bv;
-		a.a_nvals = a.a_vals;
 
-		ldap_pvt_thread_mutex_lock( &si->si_csn_mutex );
+		ldap_pvt_thread_rdwr_rlock( &si->si_csn_rwlock );
+
+		a.a_vals = si->si_ctxcsn;
+		a.a_nvals = a.a_vals;
 
 		rs->sr_err = access_allowed( op, &e, op->oq_compare.rs_ava->aa_desc,
 			&op->oq_compare.rs_ava->aa_value, ACL_COMPARE, NULL );
@@ -1575,17 +1705,17 @@ syncprov_op_compare( Operation *op, SlapReply *rs )
 
 		rs->sr_err = LDAP_COMPARE_FALSE;
 
-		if ( value_find_ex( op->oq_compare.rs_ava->aa_desc,
+		if ( attr_valfind( &a,
 			SLAP_MR_ATTRIBUTE_VALUE_NORMALIZED_MATCH |
 				SLAP_MR_ASSERTED_VALUE_NORMALIZED_MATCH,
-				a.a_nvals, &op->oq_compare.rs_ava->aa_value, op->o_tmpmemctx ) == 0 )
+				&op->oq_compare.rs_ava->aa_value, NULL, op->o_tmpmemctx ) == 0 )
 		{
 			rs->sr_err = LDAP_COMPARE_TRUE;
 		}
 
 return_results:;
 
-		ldap_pvt_thread_mutex_unlock( &si->si_csn_mutex );
+		ldap_pvt_thread_rdwr_runlock( &si->si_csn_rwlock );
 
 		send_ldap_result( op, rs );
 
@@ -1603,12 +1733,19 @@ syncprov_op_mod( Operation *op, SlapReply *rs )
 {
 	slap_overinst		*on = (slap_overinst *)op->o_bd->bd_info;
 	syncprov_info_t		*si = on->on_bi.bi_private;
+	slap_callback *cb;
+	opcookie *opc;
+	int have_psearches, cbsize;
 
-	slap_callback *cb = op->o_tmpcalloc(1, sizeof(slap_callback)+
-		sizeof(opcookie) +
-		(si->si_ops ? sizeof(modinst) : 0 ),
-		op->o_tmpmemctx);
-	opcookie *opc = (opcookie *)(cb+1);
+	ldap_pvt_thread_mutex_lock( &si->si_ops_mutex );
+	have_psearches = ( si->si_ops != NULL );
+	ldap_pvt_thread_mutex_unlock( &si->si_ops_mutex );
+
+	cbsize = sizeof(slap_callback) + sizeof(opcookie) +
+		(have_psearches ? sizeof(modinst) : 0 );
+
+	cb = op->o_tmpcalloc(1, cbsize, op->o_tmpmemctx);
+	opc = (opcookie *)(cb+1);
 	opc->son = on;
 	cb->sc_response = syncprov_op_response;
 	cb->sc_cleanup = syncprov_op_cleanup;
@@ -1619,7 +1756,7 @@ syncprov_op_mod( Operation *op, SlapReply *rs )
 	/* If there are active persistent searches, lock this operation.
 	 * See seqmod.c for the locking logic on its own.
 	 */
-	if ( si->si_ops ) {
+	if ( have_psearches ) {
 		modtarget *mt, mtdummy;
 		modinst *mi;
 
@@ -1666,7 +1803,7 @@ syncprov_op_mod( Operation *op, SlapReply *rs )
 		}
 	}
 
-	if (( si->si_ops || si->si_logs ) && op->o_tag != LDAP_REQ_ADD )
+	if (( have_psearches || si->si_logs ) && op->o_tag != LDAP_REQ_ADD )
 		syncprov_matchops( op, opc, 1 );
 
 	return SLAP_CB_CONTINUE;
@@ -1684,9 +1821,12 @@ syncprov_op_extended( Operation *op, SlapReply *rs )
 typedef struct searchstate {
 	slap_overinst *ss_on;
 	syncops *ss_so;
-	int ss_present;
-	struct berval ss_ctxcsn;
-	char ss_csnbuf[LDAP_LUTIL_CSNSTR_BUFSIZE];
+	BerVarray ss_ctxcsn;
+	int *ss_sids;
+	int ss_numcsns;
+#define	SS_PRESENT	0x01
+#define	SS_CHANGED	0x02
+	int ss_flags;
 } searchstate;
 
 static int
@@ -1700,9 +1840,17 @@ syncprov_search_cleanup( Operation *op, SlapReply *rs )
 	return 0;
 }
 
+typedef struct SyncOperationBuffer {
+	Operation		sob_op;
+	Opheader		sob_hdr;
+	AttributeName	sob_extra;	/* not always present */
+	/* Further data allocated here */
+} SyncOperationBuffer;
+
 static void
 syncprov_detach_op( Operation *op, syncops *so, slap_overinst *on )
 {
+	SyncOperationBuffer *sopbuf2;
 	Operation *op2;
 	int i, alen = 0;
 	size_t size;
@@ -1714,14 +1862,15 @@ syncprov_detach_op( Operation *op, syncops *so, slap_overinst *on )
 		alen += op->ors_attrs[i].an_name.bv_len + 1;
 	}
 	/* Make a new copy of the operation */
-	size = sizeof(Operation) + sizeof(Opheader) +
+	size = offsetof( SyncOperationBuffer, sob_extra ) +
 		(i ? ( (i+1) * sizeof(AttributeName) + alen) : 0) +
 		op->o_req_dn.bv_len + 1 +
 		op->o_req_ndn.bv_len + 1 +
 		op->o_ndn.bv_len + 1 +
 		so->s_filterstr.bv_len + 1;
-	op2 = (Operation *)ch_calloc( 1, size );
-	op2->o_hdr = (Opheader *)(op2+1);
+	sopbuf2 = ch_calloc( 1, size );
+	op2 = &sopbuf2->sob_op;
+	op2->o_hdr = &sopbuf2->sob_hdr;
 
 	/* Copy the fields we care about explicitly, leave the rest alone */
 	*op2->o_hdr = *op->o_hdr;
@@ -1731,18 +1880,18 @@ syncprov_detach_op( Operation *op, syncops *so, slap_overinst *on )
 	op2->o_request = op->o_request;
 	op2->o_private = on;
 
+	ptr = (char *) sopbuf2 + offsetof( SyncOperationBuffer, sob_extra );
 	if ( i ) {
-		op2->ors_attrs = (AttributeName *)(op2->o_hdr + 1);
-		ptr = (char *)(op2->ors_attrs+i+1);
+		op2->ors_attrs = (AttributeName *) ptr;
+		ptr = (char *) &op2->ors_attrs[i+1];
 		for (i=0; !BER_BVISNULL( &op->ors_attrs[i].an_name ); i++) {
 			op2->ors_attrs[i] = op->ors_attrs[i];
 			op2->ors_attrs[i].an_name.bv_val = ptr;
 			ptr = lutil_strcopy( ptr, op->ors_attrs[i].an_name.bv_val ) + 1;
 		}
 		BER_BVZERO( &op2->ors_attrs[i].an_name );
-	} else {
-		ptr = (char *)(op2->o_hdr + 1);
 	}
+
 	op2->o_authz = op->o_authz;
 	op2->o_ndn.bv_val = ptr;
 	ptr = lutil_strcopy(ptr, op->o_ndn.bv_val) + 1;
@@ -1756,7 +1905,15 @@ syncprov_detach_op( Operation *op, syncops *so, slap_overinst *on )
 	op2->ors_filterstr.bv_val = ptr;
 	strcpy( ptr, so->s_filterstr.bv_val );
 	op2->ors_filterstr.bv_len = so->s_filterstr.bv_len;
-	op2->ors_filter = str2filter( ptr );
+
+	/* Skip the AND/GE clause that we stuck on in front */
+	if ( so->s_flags & PS_FIX_FILTER ) {
+		op2->ors_filter = op->ors_filter->f_and->f_next;
+		so->s_flags ^= PS_FIX_FILTER;
+	} else {
+		op2->ors_filter = op->ors_filter;
+	}
+	op2->ors_filter = filter_dup( op2->ors_filter, NULL );
 	so->s_op = op2;
 
 	/* Copy any cached group ACLs individually */
@@ -1778,6 +1935,9 @@ syncprov_detach_op( Operation *op, syncops *so, slap_overinst *on )
 	LDAP_STAILQ_INSERT_TAIL( &op->o_conn->c_ops, op2, o_next );
 	so->s_flags |= PS_IS_DETACHED;
 	ldap_pvt_thread_mutex_unlock( &op->o_conn->c_mutex );
+
+	/* Prevent anyone else from trying to send a result for this op */
+	op->o_abandon = 1;
 }
 
 static int
@@ -1804,14 +1964,48 @@ syncprov_search_response( Operation *op, SlapReply *rs )
 			a = attr_find( rs->sr_operational_attrs, slap_schema.si_ad_entryCSN );
 		}
 		if ( a ) {
-			/* Make sure entry is less than the snapshot'd contextCSN */
-			if ( ber_bvcmp( &a->a_nvals[0], &ss->ss_ctxcsn ) > 0 )
+			int i, sid;
+			sid = slap_parse_csn_sid( &a->a_nvals[0] );
+
+			/* Don't send changed entries back to the originator */
+			if ( sid == srs->sr_state.sid && srs->sr_state.numcsns ) {
+				Debug( LDAP_DEBUG_SYNC,
+					"Entry %s changed by peer, ignored\n",
+					rs->sr_entry->e_name.bv_val, 0, 0 );
 				return LDAP_SUCCESS;
+			}
 
-			/* Don't send the ctx entry twice */
-			if ( !BER_BVISNULL( &srs->sr_state.ctxcsn ) &&
-				bvmatch( &a->a_nvals[0], &srs->sr_state.ctxcsn ) )
-				return LDAP_SUCCESS;
+			/* If not a persistent search */
+			if ( !ss->ss_so ) {
+				/* Make sure entry is less than the snapshot'd contextCSN */
+				for ( i=0; i<ss->ss_numcsns; i++ ) {
+					if ( sid == ss->ss_sids[i] && ber_bvcmp( &a->a_nvals[0],
+						&ss->ss_ctxcsn[i] ) > 0 ) {
+						Debug( LDAP_DEBUG_SYNC,
+							"Entry %s CSN %s greater than snapshot %s\n",
+							rs->sr_entry->e_name.bv_val,
+							a->a_nvals[0].bv_val,
+							ss->ss_ctxcsn[i].bv_val );
+						return LDAP_SUCCESS;
+					}
+				}
+			}
+
+			/* Don't send old entries twice */
+			if ( srs->sr_state.ctxcsn ) {
+				for ( i=0; i<srs->sr_state.numcsns; i++ ) {
+					if ( sid == srs->sr_state.sids[i] &&
+						ber_bvcmp( &a->a_nvals[0],
+							&srs->sr_state.ctxcsn[i] )<= 0 ) {
+						Debug( LDAP_DEBUG_SYNC,
+							"Entry %s CSN %s older or equal to ctx %s\n",
+							rs->sr_entry->e_name.bv_val,
+							a->a_nvals[0].bv_val,
+							srs->sr_state.ctxcsn[i].bv_val );
+						return LDAP_SUCCESS;
+					}
+				}
+			}
 		}
 		rs->sr_ctrls = op->o_tmpalloc( sizeof(LDAPControl *)*2,
 			op->o_tmpmemctx );
@@ -1821,24 +2015,32 @@ syncprov_search_response( Operation *op, SlapReply *rs )
 	} else if ( rs->sr_type == REP_RESULT && rs->sr_err == LDAP_SUCCESS ) {
 		struct berval cookie;
 
-		slap_compose_sync_cookie( op, &cookie, &ss->ss_ctxcsn,
-			srs->sr_state.rid );
+		if ( ss->ss_flags & SS_CHANGED ) {
+			slap_compose_sync_cookie( op, &cookie, ss->ss_ctxcsn,
+				srs->sr_state.rid, srs->sr_state.sid );
 
-		/* Is this a regular refresh? */
+			Debug( LDAP_DEBUG_SYNC, "syncprov_search_response: cookie=%s\n", cookie.bv_val, 0, 0 );
+		}
+
+		/* Is this a regular refresh?
+		 * Note: refresh never gets here if there were no changes
+		 */
 		if ( !ss->ss_so ) {
 			rs->sr_ctrls = op->o_tmpalloc( sizeof(LDAPControl *)*2,
 				op->o_tmpmemctx );
 			rs->sr_ctrls[1] = NULL;
 			rs->sr_err = syncprov_done_ctrl( op, rs, rs->sr_ctrls,
-				0, 1, &cookie, ss->ss_present ?  LDAP_SYNC_REFRESH_PRESENTS :
+				0, 1, &cookie, ( ss->ss_flags & SS_PRESENT ) ?  LDAP_SYNC_REFRESH_PRESENTS :
 					LDAP_SYNC_REFRESH_DELETES );
 			op->o_tmpfree( cookie.bv_val, op->o_tmpmemctx );
 		} else {
 		/* It's RefreshAndPersist, transition to Persist phase */
-			syncprov_sendinfo( op, rs, ( ss->ss_present && rs->sr_nentries ) ?
+			syncprov_sendinfo( op, rs, ( ss->ss_flags & SS_PRESENT ) ?
 	 			LDAP_TAG_SYNC_REFRESH_PRESENT : LDAP_TAG_SYNC_REFRESH_DELETE,
-				&cookie, 1, NULL, 0 );
-			op->o_tmpfree( cookie.bv_val, op->o_tmpmemctx );
+				( ss->ss_flags & SS_CHANGED ) ? &cookie : NULL,
+				1, NULL, 0 );
+			if ( ss->ss_flags & SS_CHANGED )
+				op->o_tmpfree( cookie.bv_val, op->o_tmpmemctx );
 
 			/* Detach this Op from frontend control */
 			ldap_pvt_thread_mutex_lock( &ss->ss_so->s_mutex );
@@ -1847,6 +2049,10 @@ syncprov_search_response( Operation *op, SlapReply *rs )
 			ss->ss_so->s_flags ^= PS_IS_REFRESHING;
 
 			syncprov_detach_op( op, ss->ss_so, on );
+
+			/* If there are queued responses, fire them off */
+			if ( ss->ss_so->s_res )
+				syncprov_qstart( ss->ss_so );
 			ldap_pvt_thread_mutex_unlock( &ss->ss_so->s_mutex );
 
 			return LDAP_SUCCESS;
@@ -1862,12 +2068,13 @@ syncprov_op_search( Operation *op, SlapReply *rs )
 	slap_overinst		*on = (slap_overinst *)op->o_bd->bd_info;
 	syncprov_info_t		*si = (syncprov_info_t *)on->on_bi.bi_private;
 	slap_callback	*cb;
-	int gotstate = 0, nochange = 0, do_present;
+	int gotstate = 0, changed = 0, do_present = 0;
 	syncops *sop = NULL;
 	searchstate *ss;
 	sync_control *srs;
-	struct berval ctxcsn;
-	char csnbuf[LDAP_LUTIL_CSNSTR_BUFSIZE];
+	BerVarray ctxcsn;
+	int i, *sids, numcsns;
+	struct berval mincsn;
 
 	if ( !(op->o_sync_mode & SLAP_SYNC_REFRESH) ) return SLAP_CB_CONTINUE;
 
@@ -1876,8 +2083,6 @@ syncprov_op_search( Operation *op, SlapReply *rs )
 		return rs->sr_err;
 	}
 
-	do_present = si->si_nopres ? 0 : 1;
-
 	srs = op->o_controls[slap_cids.sc_LDAPsync];
 	op->o_managedsait = SLAP_CONTROL_NONCRITICAL;
 
@@ -1896,10 +2101,12 @@ syncprov_op_search( Operation *op, SlapReply *rs )
 		/* syncprov_findbase expects to be called as a callback... */
 		sc.sc_private = &opc;
 		opc.son = on;
+		ldap_pvt_thread_mutex_init( &so.s_mutex );
 		cb = op->o_callback;
 		op->o_callback = &sc;
 		rs->sr_err = syncprov_findbase( op, &fc );
 		op->o_callback = cb;
+		ldap_pvt_thread_mutex_destroy( &so.s_mutex );
 
 		if ( rs->sr_err != LDAP_SUCCESS ) {
 			send_ldap_result( op, rs );
@@ -1909,6 +2116,7 @@ syncprov_op_search( Operation *op, SlapReply *rs )
 		*sop = so;
 		ldap_pvt_thread_mutex_init( &sop->s_mutex );
 		sop->s_rid = srs->sr_state.rid;
+		sop->s_sid = srs->sr_state.sid;
 		sop->s_inuse = 1;
 
 		ldap_pvt_thread_mutex_lock( &si->si_ops_mutex );
@@ -1918,44 +2126,104 @@ syncprov_op_search( Operation *op, SlapReply *rs )
 	}
 
 	/* snapshot the ctxcsn */
-	ldap_pvt_thread_mutex_lock( &si->si_csn_mutex );
-	strcpy( csnbuf, si->si_ctxcsnbuf );
-	ctxcsn.bv_len = si->si_ctxcsn.bv_len;
-	ldap_pvt_thread_mutex_unlock( &si->si_csn_mutex );
-	ctxcsn.bv_val = csnbuf;
+	ldap_pvt_thread_rdwr_rlock( &si->si_csn_rwlock );
+	numcsns = si->si_numcsns;
+	if ( numcsns ) {
+		ber_bvarray_dup_x( &ctxcsn, si->si_ctxcsn, op->o_tmpmemctx );
+		sids = op->o_tmpalloc( numcsns * sizeof(int), op->o_tmpmemctx );
+		for ( i=0; i<numcsns; i++ )
+			sids[i] = si->si_sids[i];
+	} else {
+		ctxcsn = NULL;
+		sids = NULL;
+	}
+	ldap_pvt_thread_rdwr_runlock( &si->si_csn_rwlock );
 	
 	/* If we have a cookie, handle the PRESENT lookups */
-	if ( !BER_BVISNULL( &srs->sr_state.ctxcsn )) {
+	if ( srs->sr_state.ctxcsn ) {
 		sessionlog *sl;
+		int i, j;
 
-		/* The cookie was validated when it was parsed, just use it */
+		/* If we don't have any CSN of our own yet, pretend nothing
+		 * has changed.
+		 */
+		if ( !numcsns )
+			goto no_change;
 
-		/* If just Refreshing and nothing has changed, shortcut it */
-		if ( bvmatch( &srs->sr_state.ctxcsn, &ctxcsn )) {
-			nochange = 1;
-			if ( !(op->o_sync_mode & SLAP_SYNC_PERSIST) ) {
-				LDAPControl	*ctrls[2];
+		if ( !si->si_nopres )
+			do_present = SS_PRESENT;
 
-				ctrls[0] = NULL;
-				ctrls[1] = NULL;
-				syncprov_done_ctrl( op, rs, ctrls, 0, 0,
-					NULL, LDAP_SYNC_REFRESH_DELETES );
-				rs->sr_ctrls = ctrls;
-				rs->sr_err = LDAP_SUCCESS;
-				send_ldap_result( op, rs );
-				rs->sr_ctrls = NULL;
-				return rs->sr_err;
+		/* If there are SIDs we don't recognize in the cookie, drop them */
+		for (i=0; i<srs->sr_state.numcsns; ) {
+			for (j=0; j<numcsns; j++) {
+				if ( srs->sr_state.sids[i] == sids[j] ) {
+					break;
+				}
+			}
+			/* not found */
+			if ( j == numcsns ) {
+				struct berval tmp = srs->sr_state.ctxcsn[i];
+				j = srs->sr_state.numcsns - 1;
+				srs->sr_state.ctxcsn[i] = srs->sr_state.ctxcsn[j];
+				tmp.bv_len = 0;
+				srs->sr_state.ctxcsn[j] = tmp;
+				srs->sr_state.numcsns = j;
+				srs->sr_state.sids[i] = srs->sr_state.sids[j];
+				continue;
+			}
+			i++;
+		}
+
+		/* Find the smallest CSN */
+		mincsn = srs->sr_state.ctxcsn[0];
+		for ( i=1; i<srs->sr_state.numcsns; i++ ) {
+			if ( ber_bvcmp( &mincsn, &srs->sr_state.ctxcsn[i] ) > 0 )
+				mincsn = srs->sr_state.ctxcsn[i];
+		}
+
+		/* If nothing has changed, shortcut it */
+		if ( srs->sr_state.numcsns == numcsns ) {
+			int i, j;
+			for ( i=0; i<srs->sr_state.numcsns; i++ ) {
+				for ( j=0; j<numcsns; j++ ) {
+					if ( srs->sr_state.sids[i] != sids[j] )
+						continue;
+					if ( !bvmatch( &srs->sr_state.ctxcsn[i], &ctxcsn[j] ))
+						changed = SS_CHANGED;
+					break;
+				}
+				if ( changed )
+					break;
+			}
+			if ( !changed ) {
+				do_present = 0;
+no_change:		if ( !(op->o_sync_mode & SLAP_SYNC_PERSIST) ) {
+					LDAPControl	*ctrls[2];
+
+					ctrls[0] = NULL;
+					ctrls[1] = NULL;
+					syncprov_done_ctrl( op, rs, ctrls, 0, 0,
+						NULL, LDAP_SYNC_REFRESH_DELETES );
+					rs->sr_ctrls = ctrls;
+					rs->sr_err = LDAP_SUCCESS;
+					send_ldap_result( op, rs );
+					rs->sr_ctrls = NULL;
+					return rs->sr_err;
+				}
+				goto shortcut;
 			}
-			goto shortcut;
 		}
 		/* Do we have a sessionlog for this search? */
 		sl=si->si_logs;
 		if ( sl ) {
 			ldap_pvt_thread_mutex_lock( &sl->sl_mutex );
-			if ( ber_bvcmp( &srs->sr_state.ctxcsn, &sl->sl_mincsn ) >= 0 ) {
+			/* Are there any log entries, and is the consumer state
+			 * present in the session log?
+			 */
+			if ( sl->sl_num > 0 && ber_bvcmp( &mincsn, &sl->sl_mincsn ) >= 0 ) {
 				do_present = 0;
 				/* mutex is unlocked in playlog */
-				syncprov_playlog( op, rs, sl, &srs->sr_state.ctxcsn, &ctxcsn );
+				syncprov_playlog( op, rs, sl, srs, ctxcsn, numcsns, sids );
 			} else {
 				ldap_pvt_thread_mutex_unlock( &sl->sl_mutex );
 			}
@@ -1965,6 +2233,10 @@ syncprov_op_search( Operation *op, SlapReply *rs )
 			/* No, so a reload is required */
 			/* the 2.2 consumer doesn't send this hint */
 			if ( si->si_usehint && srs->sr_rhint == 0 ) {
+				if ( ctxcsn )
+					ber_bvarray_free_x( ctxcsn, op->o_tmpmemctx );
+				if ( sids )
+					op->o_tmpfree( sids, op->o_tmpmemctx );
 				send_ldap_error( op, rs, LDAP_SYNC_REFRESH_REQUIRED, "sync cookie is stale" );
 				return rs->sr_err;
 			}
@@ -1973,10 +2245,17 @@ syncprov_op_search( Operation *op, SlapReply *rs )
 			/* If changed and doing Present lookup, send Present UUIDs */
 			if ( do_present && syncprov_findcsn( op, FIND_PRESENT ) !=
 				LDAP_SUCCESS ) {
+				if ( ctxcsn )
+					ber_bvarray_free_x( ctxcsn, op->o_tmpmemctx );
+				if ( sids )
+					op->o_tmpfree( sids, op->o_tmpmemctx );
 				send_ldap_result( op, rs );
 				return rs->sr_err;
 			}
 		}
+	} else {
+		/* No consumer state, assume something has changed */
+		changed = SS_CHANGED;
 	}
 
 shortcut:
@@ -1988,7 +2267,7 @@ shortcut:
 	}
 
 	/* If something changed, find the changes */
-	if ( gotstate && !nochange ) {
+	if ( gotstate && changed ) {
 		Filter *fand, *fava;
 
 		fand = op->o_tmpalloc( sizeof(Filter), op->o_tmpmemctx );
@@ -2002,10 +2281,12 @@ shortcut:
 #ifdef LDAP_COMP_MATCH
 		fava->f_ava->aa_cf = NULL;
 #endif
-		ber_dupbv_x( &fava->f_ava->aa_value, &srs->sr_state.ctxcsn, op->o_tmpmemctx );
+		ber_dupbv_x( &fava->f_ava->aa_value, &mincsn, op->o_tmpmemctx );
 		fava->f_next = op->ors_filter;
 		op->ors_filter = fand;
 		filter2bv_x( op, op->ors_filter, &op->ors_filterstr );
+		if ( sop )
+			sop->s_flags |= PS_FIX_FILTER;
 	}
 
 	/* Let our callback add needed info to returned entries */
@@ -2013,25 +2294,21 @@ shortcut:
 	ss = (searchstate *)(cb+1);
 	ss->ss_on = on;
 	ss->ss_so = sop;
-	ss->ss_present = do_present;
-	ss->ss_ctxcsn.bv_len = ctxcsn.bv_len;
-	ss->ss_ctxcsn.bv_val = ss->ss_csnbuf;
-	strcpy( ss->ss_ctxcsn.bv_val, ctxcsn.bv_val );
+	ss->ss_flags = do_present | changed;
+	ss->ss_ctxcsn = ctxcsn;
+	ss->ss_numcsns = numcsns;
+	ss->ss_sids = sids;
 	cb->sc_response = syncprov_search_response;
 	cb->sc_cleanup = syncprov_search_cleanup;
 	cb->sc_private = ss;
 	cb->sc_next = op->o_callback;
 	op->o_callback = cb;
 
-#if 0	/* I don't think we need to shortcircuit back-bdb any more */
-	op->o_sync_mode &= SLAP_CONTROL_MASK;
-#endif
-
 	/* If this is a persistent search and no changes were reported during
 	 * the refresh phase, just invoke the response callback to transition
 	 * us into persist phase
 	 */
-	if ( nochange ) {
+	if ( !changed ) {
 		rs->sr_err = LDAP_SUCCESS;
 		rs->sr_nentries = 0;
 		send_ldap_result( op, rs );
@@ -2048,6 +2325,12 @@ syncprov_operational(
 	slap_overinst		*on = (slap_overinst *)op->o_bd->bd_info;
 	syncprov_info_t		*si = (syncprov_info_t *)on->on_bi.bi_private;
 
+	/* This prevents generating unnecessarily; frontend will strip
+	 * any statically stored copy.
+	 */
+	if ( op->o_sync != SLAP_CONTROL_NONE )
+		return SLAP_CB_CONTINUE;
+
 	if ( rs->sr_entry &&
 		dn_match( &rs->sr_entry->e_nname, op->o_bd->be_nsuffix )) {
 
@@ -2060,26 +2343,35 @@ syncprov_operational(
 					break;
 			}
 
-			if ( !a ) {
-				for ( ap = &rs->sr_operational_attrs; *ap; ap=&(*ap)->a_next );
-
-				a = ch_malloc( sizeof(Attribute));
-				a->a_desc = slap_schema.si_ad_contextCSN;
-				a->a_vals = ch_malloc( 2 * sizeof(struct berval));
-				a->a_vals[1].bv_val = NULL;
-				a->a_nvals = a->a_vals;
-				a->a_next = NULL;
-				a->a_flags = 0;
-				*ap = a;
-			}
+			ldap_pvt_thread_rdwr_rlock( &si->si_csn_rwlock );
+			if ( si->si_ctxcsn ) {
+				if ( !a ) {
+					for ( ap = &rs->sr_operational_attrs; *ap;
+						ap=&(*ap)->a_next );
 
-			ldap_pvt_thread_mutex_lock( &si->si_csn_mutex );
-			if ( !ap ) {
-				strcpy( a->a_vals[0].bv_val, si->si_ctxcsnbuf );
-			} else {
-				ber_dupbv( &a->a_vals[0], &si->si_ctxcsn );
+					a = attr_alloc( slap_schema.si_ad_contextCSN );
+					*ap = a;
+				}
+
+				if ( !ap ) {
+					if ( !rs->sr_flags & REP_ENTRY_MODIFIABLE ) {
+						rs->sr_entry = entry_dup( rs->sr_entry );
+						rs->sr_flags |=
+							REP_ENTRY_MODIFIABLE|REP_ENTRY_MUSTBEFREED;
+						a = attr_find( rs->sr_entry->e_attrs,
+							slap_schema.si_ad_contextCSN );
+					}
+					if ( a->a_nvals != a->a_vals ) {
+						ber_bvarray_free( a->a_nvals );
+					}
+					a->a_nvals = NULL;
+					ber_bvarray_free( a->a_vals );
+					a->a_vals = NULL;
+					a->a_numvals = 0;
+				}
+				attr_valadd( a, si->si_ctxcsn, si->si_ctxcsn, si->si_numcsns );
 			}
-			ldap_pvt_thread_mutex_unlock( &si->si_csn_mutex );
+			ldap_pvt_thread_rdwr_runlock( &si->si_csn_rwlock );
 		}
 	}
 	return SLAP_CB_CONTINUE;
@@ -2136,10 +2428,14 @@ sp_cf_gen(ConfigArgs *c)
 		case SP_CHKPT:
 			if ( si->si_chkops || si->si_chktime ) {
 				struct berval bv;
-				bv.bv_len = sprintf( c->msg, "%d %d",
-					si->si_chkops, si->si_chktime );
-				bv.bv_val = c->msg;
-				value_add_one( &c->rvalue_vals, &bv );
+				bv.bv_len = snprintf( c->cr_msg, sizeof( c->cr_msg ),
+					"%d %d", si->si_chkops, si->si_chktime );
+				if ( bv.bv_len < 0 || bv.bv_len >= sizeof( c->cr_msg ) ) {
+					rc = 1;
+				} else {
+					bv.bv_val = c->cr_msg;
+					value_add_one( &c->rvalue_vals, &bv );
+				}
 			} else {
 				rc = 1;
 			}
@@ -2197,27 +2493,31 @@ sp_cf_gen(ConfigArgs *c)
 	switch ( c->type ) {
 	case SP_CHKPT:
 		if ( lutil_atoi( &si->si_chkops, c->argv[1] ) != 0 ) {
-			sprintf( c->msg, "%s unable to parse checkpoint ops # \"%s\"",
+			snprintf( c->cr_msg, sizeof( c->cr_msg ), "%s unable to parse checkpoint ops # \"%s\"",
 				c->argv[0], c->argv[1] );
-			Debug( LDAP_DEBUG_CONFIG, "%s: %s\n", c->log, c->msg, 0 );
+			Debug( LDAP_DEBUG_CONFIG|LDAP_DEBUG_NONE,
+				"%s: %s\n", c->log, c->cr_msg, 0 );
 			return ARG_BAD_CONF;
 		}
 		if ( si->si_chkops <= 0 ) {
-			sprintf( c->msg, "%s invalid checkpoint ops # \"%d\"",
+			snprintf( c->cr_msg, sizeof( c->cr_msg ), "%s invalid checkpoint ops # \"%d\"",
 				c->argv[0], si->si_chkops );
-			Debug( LDAP_DEBUG_CONFIG, "%s: %s\n", c->log, c->msg, 0 );
+			Debug( LDAP_DEBUG_CONFIG|LDAP_DEBUG_NONE,
+				"%s: %s\n", c->log, c->cr_msg, 0 );
 			return ARG_BAD_CONF;
 		}
 		if ( lutil_atoi( &si->si_chktime, c->argv[2] ) != 0 ) {
-			sprintf( c->msg, "%s unable to parse checkpoint time \"%s\"",
+			snprintf( c->cr_msg, sizeof( c->cr_msg ), "%s unable to parse checkpoint time \"%s\"",
 				c->argv[0], c->argv[1] );
-			Debug( LDAP_DEBUG_CONFIG, "%s: %s\n", c->log, c->msg, 0 );
+			Debug( LDAP_DEBUG_CONFIG|LDAP_DEBUG_NONE,
+				"%s: %s\n", c->log, c->cr_msg, 0 );
 			return ARG_BAD_CONF;
 		}
 		if ( si->si_chktime <= 0 ) {
-			sprintf( c->msg, "%s invalid checkpoint time \"%d\"",
+			snprintf( c->cr_msg, sizeof( c->cr_msg ), "%s invalid checkpoint time \"%d\"",
 				c->argv[0], si->si_chkops );
-			Debug( LDAP_DEBUG_CONFIG, "%s: %s\n", c->log, c->msg, 0 );
+			Debug( LDAP_DEBUG_CONFIG|LDAP_DEBUG_NONE,
+				"%s: %s\n", c->log, c->cr_msg, 0 );
 			return ARG_BAD_CONF;
 		}
 		si->si_chktime *= 60;
@@ -2227,9 +2527,10 @@ sp_cf_gen(ConfigArgs *c)
 		int size = c->value_int;
 
 		if ( size < 0 ) {
-			sprintf( c->msg, "%s size %d is negative",
+			snprintf( c->cr_msg, sizeof( c->cr_msg ), "%s size %d is negative",
 				c->argv[0], size );
-			Debug( LDAP_DEBUG_CONFIG, "%s: %s\n", c->log, c->msg, 0 );
+			Debug( LDAP_DEBUG_CONFIG|LDAP_DEBUG_NONE,
+				"%s: %s\n", c->log, c->cr_msg, 0 );
 			return ARG_BAD_CONF;
 		}
 		sl = si->si_logs;
@@ -2273,21 +2574,27 @@ syncprov_db_otask(
  */
 static int
 syncprov_db_open(
-    BackendDB *be
+	BackendDB *be,
+	ConfigReply *cr
 )
 {
 	slap_overinst   *on = (slap_overinst *) be->bd_info;
 	syncprov_info_t *si = (syncprov_info_t *)on->on_bi.bi_private;
 
 	Connection conn = { 0 };
-	OperationBuffer opbuf = { 0 };
-	char ctxcsnbuf[LDAP_LUTIL_CSNSTR_BUFSIZE];
-	Operation *op = (Operation *) &opbuf;
-	Entry *e;
+	OperationBuffer opbuf;
+	Operation *op;
+	Entry *e = NULL;
 	Attribute *a;
 	int rc;
 	void *thrctx = NULL;
 
+	if ( !SLAP_LASTMOD( be )) {
+		Debug( LDAP_DEBUG_ANY,
+			"syncprov_db_open: invalid config, lastmod must be enabled\n", 0, 0, 0 );
+		return -1;
+	}
+
 	if ( slapMode & SLAP_TOOL_MODE ) {
 		return 0;
 	}
@@ -2298,62 +2605,60 @@ syncprov_db_open(
 	}
 
 	thrctx = ldap_pvt_thread_pool_context();
-	connection_fake_init( &conn, op, thrctx );
+	connection_fake_init( &conn, &opbuf, thrctx );
+	op = &opbuf.ob_op;
 	op->o_bd = be;
 	op->o_dn = be->be_rootdn;
 	op->o_ndn = be->be_rootndn;
 
-	ctxcsnbuf[0] = '\0';
-
-	op->o_bd->bd_info = on->on_info->oi_orig;
-	rc = be_entry_get_rw( op, be->be_nsuffix, NULL,
-		slap_schema.si_ad_contextCSN, 0, &e );
+	rc = overlay_entry_get_ov( op, be->be_nsuffix, NULL,
+		slap_schema.si_ad_contextCSN, 0, &e, on );
 
 	if ( e ) {
 		ldap_pvt_thread_t tid;
 
 		a = attr_find( e->e_attrs, slap_schema.si_ad_contextCSN );
 		if ( a ) {
-			si->si_ctxcsn.bv_len = a->a_nvals[0].bv_len;
-			if ( si->si_ctxcsn.bv_len >= sizeof(si->si_ctxcsnbuf ))
-				si->si_ctxcsn.bv_len = sizeof(si->si_ctxcsnbuf)-1;
-			strncpy( si->si_ctxcsnbuf, a->a_nvals[0].bv_val,
-				si->si_ctxcsn.bv_len );
-			si->si_ctxcsnbuf[si->si_ctxcsn.bv_len] = '\0';
-			strcpy( ctxcsnbuf, si->si_ctxcsnbuf );
-		}
-		be_entry_release_rw( op, e, 0 );
-		if ( !BER_BVISEMPTY( &si->si_ctxcsn ) ) {
-			op->o_bd->bd_info = (BackendInfo *)on;
+			ber_bvarray_dup_x( &si->si_ctxcsn, a->a_vals, NULL );
+			si->si_numcsns = a->a_numvals;
+			si->si_sids = slap_parse_csn_sids( si->si_ctxcsn, a->a_numvals, NULL );
+		}
+		overlay_entry_release_ov( op, e, 0, on );
+		if ( si->si_ctxcsn ) {
 			op->o_req_dn = be->be_suffix[0];
 			op->o_req_ndn = be->be_nsuffix[0];
 			op->ors_scope = LDAP_SCOPE_SUBTREE;
 			ldap_pvt_thread_create( &tid, 0, syncprov_db_otask, op );
 			ldap_pvt_thread_join( tid, NULL );
 		}
-	} else if ( SLAP_SYNC_SHADOW( op->o_bd )) {
-		/* If we're also a consumer, and we didn't find the context entry,
-		 * then don't generate anything, wait for our provider to send it
-		 * to us.
-		 */
-		goto out;
 	}
 
-	if ( BER_BVISEMPTY( &si->si_ctxcsn ) ) {
-		si->si_ctxcsn.bv_len = sizeof( si->si_ctxcsnbuf );
-		slap_get_csn( op, &si->si_ctxcsn, 0 );
-	}
+	/* Didn't find a contextCSN, should we generate one? */
+	if ( !si->si_ctxcsn ) {
+		char csnbuf[ LDAP_LUTIL_CSNSTR_BUFSIZE ];
+		struct berval csn;
 
-	/* If our ctxcsn is different from what was read from the root
-	 * entry, make sure we do a checkpoint on close
-	 */
-	if ( strcmp( si->si_ctxcsnbuf, ctxcsnbuf )) {
+		if ( SLAP_SYNC_SHADOW( op->o_bd )) {
+		/* If we're also a consumer, then don't generate anything.
+		 * Wait for our provider to send it to us, or for a local
+		 * modify if we have multimaster.
+		 */
+			goto out;
+		}
+		csn.bv_val = csnbuf;
+		csn.bv_len = sizeof( csnbuf );
+		slap_get_csn( op, &csn, 0 );
+		value_add_one( &si->si_ctxcsn, &csn );
+		si->si_numcsns = 1;
+		si->si_sids = ch_malloc( sizeof(int) );
+		si->si_sids[0] = slap_serverID;
+
+		/* make sure we do a checkpoint on close */
 		si->si_numops++;
 	}
 
 out:
 	op->o_bd->bd_info = (BackendInfo *)on;
-	ldap_pvt_thread_pool_context_reset( thrctx );
 	return 0;
 }
 
@@ -2361,7 +2666,8 @@ out:
  */
 static int
 syncprov_db_close(
-    BackendDB *be
+	BackendDB *be,
+	ConfigReply *cr
 )
 {
     slap_overinst   *on = (slap_overinst *) be->bd_info;
@@ -2371,19 +2677,19 @@ syncprov_db_close(
 		return 0;
 	}
 	if ( si->si_numops ) {
-		Connection conn;
+		Connection conn = {0};
 		OperationBuffer opbuf;
-		Operation *op = (Operation *) &opbuf;
+		Operation *op;
 		SlapReply rs = {REP_RESULT};
 		void *thrctx;
 
 		thrctx = ldap_pvt_thread_pool_context();
-		connection_fake_init( &conn, op, thrctx );
+		connection_fake_init( &conn, &opbuf, thrctx );
+		op = &opbuf.ob_op;
 		op->o_bd = be;
 		op->o_dn = be->be_rootdn;
 		op->o_ndn = be->be_rootndn;
 		syncprov_checkpoint( op, &rs, on );
-		ldap_pvt_thread_pool_context_reset( thrctx );
 	}
 
     return 0;
@@ -2391,18 +2697,25 @@ syncprov_db_close(
 
 static int
 syncprov_db_init(
-	BackendDB *be
+	BackendDB *be,
+	ConfigReply *cr
 )
 {
 	slap_overinst	*on = (slap_overinst *)be->bd_info;
 	syncprov_info_t	*si;
 
+	if ( SLAP_ISGLOBALOVERLAY( be ) ) {
+		Debug( LDAP_DEBUG_ANY,
+			"syncprov must be instantiated within a database.\n",
+			0, 0, 0 );
+		return 1;
+	}
+
 	si = ch_calloc(1, sizeof(syncprov_info_t));
 	on->on_bi.bi_private = si;
-	ldap_pvt_thread_mutex_init( &si->si_csn_mutex );
+	ldap_pvt_thread_rdwr_init( &si->si_csn_rwlock );
 	ldap_pvt_thread_mutex_init( &si->si_ops_mutex );
 	ldap_pvt_thread_mutex_init( &si->si_mods_mutex );
-	si->si_ctxcsn.bv_val = si->si_ctxcsnbuf;
 
 	csn_anlist[0].an_desc = slap_schema.si_ad_entryCSN;
 	csn_anlist[0].an_name = slap_schema.si_ad_entryCSN->ad_cname;
@@ -2417,7 +2730,8 @@ syncprov_db_init(
 
 static int
 syncprov_db_destroy(
-	BackendDB *be
+	BackendDB *be,
+	ConfigReply *cr
 )
 {
 	slap_overinst	*on = (slap_overinst *)be->bd_info;
@@ -2425,11 +2739,23 @@ syncprov_db_destroy(
 
 	if ( si ) {
 		if ( si->si_logs ) {
+			slog_entry *se = si->si_logs->sl_head;
+
+			while ( se ) {
+				slog_entry *se_next = se->se_next;
+				ch_free( se );
+				se = se_next;
+			}
+				
 			ch_free( si->si_logs );
 		}
+		if ( si->si_ctxcsn )
+			ber_bvarray_free( si->si_ctxcsn );
+		if ( si->si_sids )
+			ch_free( si->si_sids );
 		ldap_pvt_thread_mutex_destroy( &si->si_mods_mutex );
 		ldap_pvt_thread_mutex_destroy( &si->si_ops_mutex );
-		ldap_pvt_thread_mutex_destroy( &si->si_csn_mutex );
+		ldap_pvt_thread_rdwr_destroy( &si->si_csn_rwlock );
 		ch_free( si );
 	}
 
@@ -2460,8 +2786,13 @@ static int syncprov_parseCtrl (
 		return LDAP_PROTOCOL_ERROR;
 	}
 
+	if ( BER_BVISNULL( &ctrl->ldctl_value ) ) {
+		rs->sr_text = "Sync control value is absent";
+		return LDAP_PROTOCOL_ERROR;
+	}
+
 	if ( BER_BVISEMPTY( &ctrl->ldctl_value ) ) {
-		rs->sr_text = "Sync control value is empty (or absent)";
+		rs->sr_text = "Sync control value is empty";
 		return LDAP_PROTOCOL_ERROR;
 	}
 
@@ -2519,10 +2850,14 @@ static int syncprov_parseCtrl (
 	sr->sr_rhint = rhint;
 	if (!BER_BVISNULL(&cookie)) {
 		ber_dupbv_x( &sr->sr_state.octet_str, &cookie, op->o_tmpmemctx );
-		slap_parse_sync_cookie( &sr->sr_state, op->o_tmpmemctx );
-		if ( sr->sr_state.rid == -1 ) {
-			rs->sr_text = "Sync control : cookie parsing error";
-			return LDAP_PROTOCOL_ERROR;
+		/* If parse fails, pretend no cookie was sent */
+		if ( slap_parse_sync_cookie( &sr->sr_state, op->o_tmpmemctx ) ||
+			sr->sr_state.rid == -1 ) {
+			if ( sr->sr_state.ctxcsn ) {
+				ber_bvarray_free_x( sr->sr_state.ctxcsn, op->o_tmpmemctx );
+				sr->sr_state.ctxcsn = NULL;
+			}
+			sr->sr_state.numcsns = 0;
 		}
 	}