syncprov.c

/* $OpenLDAP$ */
/* syncprov.c - syncrepl provider */
/* This work is part of OpenLDAP Software <http://www.openldap.org/>.
 *
 * Copyright 2004-2020 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>.
 */
/* ACKNOWLEDGEMENTS:
 * This work was initially developed by Howard Chu for inclusion in
 * OpenLDAP Software.
 */

#include "portable.h"

#ifdef SLAPD_OVER_SYNCPROV

#include <ac/string.h>
#include "lutil.h"
#include "slap.h"
#include "config.h"
#include "ldap_rq.h"

#ifdef LDAP_DEVEL
#define	CHECK_CSN	1
#endif

/* A modify request on a particular entry */
typedef struct modinst {
	struct modinst *mi_next;
	Operation *mi_op;
} modinst;

typedef struct modtarget {
	struct modinst *mt_mods;
	struct modinst *mt_tail;
	struct berval mt_dn;
	ldap_pvt_thread_mutex_t mt_mutex;
} modtarget;

/* All the info of a psearch result that's shared between
 * multiple queues
 */
typedef struct resinfo {
	struct syncres *ri_list;
	Entry *ri_e;
	struct berval ri_dn;
	struct berval ri_ndn;
	struct berval ri_uuid;
	struct berval ri_csn;
	struct berval ri_cookie;
	char ri_isref;
	ldap_pvt_thread_mutex_t ri_mutex;
} resinfo;

/* A queued result of a persistent search */
typedef struct syncres {
	struct syncres *s_next;	/* list of results on this psearch queue */
	struct syncres *s_rilist;	/* list of psearches using this result */
	resinfo *s_info;
	char s_mode;
} syncres;

/* Record of a persistent search */
typedef struct syncops {
	struct syncops *s_next;
	struct syncprov_info_t *s_si;
	struct berval	s_base;		/* ndn of search base */
	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
#define	PS_TASK_QUEUED		0x20

	int		s_inuse;	/* reference count */
	struct syncres *s_res;
	struct syncres *s_restail;
	void *s_pool_cookie;
	ldap_pvt_thread_mutex_t	s_mutex;
} syncops;

/* A received sync control */
typedef struct sync_control {
	struct sync_cookie sr_state;
	int sr_rhint;
} sync_control;

#if 0 /* moved back to slap.h */
#define	o_sync	o_ctrlflag[slap_cids.sc_LDAPsync]
#endif
/* o_sync_mode uses data bits of o_sync */
#define	o_sync_mode	o_ctrlflag[slap_cids.sc_LDAPsync]

#define SLAP_SYNC_NONE					(LDAP_SYNC_NONE<<SLAP_CONTROL_SHIFT)
#define SLAP_SYNC_REFRESH				(LDAP_SYNC_REFRESH_ONLY<<SLAP_CONTROL_SHIFT)
#define SLAP_SYNC_PERSIST				(LDAP_SYNC_RESERVED<<SLAP_CONTROL_SHIFT)
#define SLAP_SYNC_REFRESH_AND_PERSIST	(LDAP_SYNC_REFRESH_AND_PERSIST<<SLAP_CONTROL_SHIFT)

/* Record of which searches matched at premodify step */
typedef struct syncmatches {
	struct syncmatches *sm_next;
	syncops *sm_op;
} syncmatches;

/* Session log data */
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;

typedef struct sessionlog {
	BerVarray	sl_mincsn;
	int		*sl_sids;
	int		sl_numcsns;
	int		sl_num;
	int		sl_size;
	int		sl_playing;
	slog_entry *sl_head;
	slog_entry *sl_tail;
	ldap_pvt_thread_mutex_t sl_mutex;
} sessionlog;

/* The main state for this overlay */
typedef struct syncprov_info_t {
	syncops		*si_ops;
	struct berval	si_contextdn;
	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 */
	int		si_nopres;	/* Skip present phase */
	int		si_usehint;	/* use reload hint */
	int		si_active;	/* True if there are active mods */
	int		si_dirty;	/* True if the context is dirty, i.e changes
						 * have been made without updating the csn. */
	time_t	si_chklast;	/* time of last checkpoint */
	Avlnode	*si_mods;	/* entries being modified */
	sessionlog	*si_logs;
	ldap_pvt_thread_rdwr_t	si_csn_rwlock;
	ldap_pvt_thread_mutex_t	si_ops_mutex;
	ldap_pvt_thread_mutex_t	si_mods_mutex;
	ldap_pvt_thread_mutex_t	si_resp_mutex;
} syncprov_info_t;

typedef struct opcookie {
	slap_overinst *son;
	syncmatches *smatches;
	modtarget *smt;
	Entry *se;
	struct berval sdn;	/* DN of entry, for deletes */
	struct berval sndn;
	struct berval suuid;	/* UUID of entry */
	struct berval sctxcsn;
	short osid;	/* sid of op csn */
	short rsid;	/* sid of relay */
	short sreference;	/* Is the entry a reference? */
	syncres ssres;
} opcookie;

typedef struct fbase_cookie {
	struct berval *fdn;	/* DN of a modified entry, for scope testing */
	syncops *fss;	/* persistent search we're testing against */
	int fbase;	/* if TRUE we found the search base and it's still valid */
	int fscope;	/* if TRUE then fdn is within the psearch scope */
} fbase_cookie;

static AttributeName csn_anlist[3];
static AttributeName uuid_anlist[2];

/* Build a LDAPsync intermediate state control */
static int
syncprov_state_ctrl(
	Operation	*op,
	SlapReply	*rs,
	Entry		*e,
	int		entry_sync_state,
	LDAPControl	**ctrls,
	int		num_ctrls,
	int		send_cookie,
	struct berval	*cookie )
{
	Attribute* a;
	int ret;

	BerElementBuffer berbuf;
	BerElement *ber = (BerElement *)&berbuf;
	LDAPControl *cp;
	struct berval bv;
	struct berval	entryuuid_bv = BER_BVNULL;

	ber_init2( ber, 0, LBER_USE_DER );
	ber_set_option( ber, LBER_OPT_BER_MEMCTX, &op->o_tmpmemctx );

	for ( a = e->e_attrs; a != NULL; a = a->a_next ) {
		AttributeDescription *desc = a->a_desc;
		if ( desc == slap_schema.si_ad_entryUUID ) {
			entryuuid_bv = a->a_nvals[0];
			break;
		}
	}

	/* FIXME: what if entryuuid is NULL or empty ? */

	if ( send_cookie && cookie ) {
		ber_printf( ber, "{eOON}",
			entry_sync_state, &entryuuid_bv, cookie );
	} else {
		ber_printf( ber, "{eON}",
			entry_sync_state, &entryuuid_bv );
	}

	ret = ber_flatten2( ber, &bv, 0 );
	if ( ret == 0 ) {
		cp = op->o_tmpalloc( sizeof( LDAPControl ) + bv.bv_len, op->o_tmpmemctx );
		cp->ldctl_oid = LDAP_CONTROL_SYNC_STATE;
		cp->ldctl_iscritical = (op->o_sync == SLAP_CONTROL_CRITICAL);
		cp->ldctl_value.bv_val = (char *)&cp[1];
		cp->ldctl_value.bv_len = bv.bv_len;
		AC_MEMCPY( cp->ldctl_value.bv_val, bv.bv_val, bv.bv_len );
		ctrls[num_ctrls] = cp;
	}
	ber_free_buf( ber );

	if ( ret < 0 ) {
		Debug( LDAP_DEBUG_TRACE,
			"slap_build_sync_ctrl: ber_flatten2 failed (%d)\n",
			ret );
		send_ldap_error( op, rs, LDAP_OTHER, "internal error" );
		return LDAP_OTHER;
	}

	return LDAP_SUCCESS;
}

/* Build a LDAPsync final state control */
static int
syncprov_done_ctrl(
	Operation	*op,
	SlapReply	*rs,
	LDAPControl	**ctrls,
	int			num_ctrls,
	int			send_cookie,
	struct berval *cookie,
	int			refreshDeletes )
{
	int ret;
	BerElementBuffer berbuf;
	BerElement *ber = (BerElement *)&berbuf;
	LDAPControl *cp;
	struct berval bv;

	ber_init2( ber, NULL, LBER_USE_DER );
	ber_set_option( ber, LBER_OPT_BER_MEMCTX, &op->o_tmpmemctx );

	ber_printf( ber, "{" );
	if ( send_cookie && cookie ) {
		ber_printf( ber, "O", cookie );
	}
	if ( refreshDeletes == LDAP_SYNC_REFRESH_DELETES ) {
		ber_printf( ber, "b", refreshDeletes );
	}
	ber_printf( ber, "N}" );

	ret = ber_flatten2( ber, &bv, 0 );
	if ( ret == 0 ) {
		cp = op->o_tmpalloc( sizeof( LDAPControl ) + bv.bv_len, op->o_tmpmemctx );
		cp->ldctl_oid = LDAP_CONTROL_SYNC_DONE;
		cp->ldctl_iscritical = (op->o_sync == SLAP_CONTROL_CRITICAL);
		cp->ldctl_value.bv_val = (char *)&cp[1];
		cp->ldctl_value.bv_len = bv.bv_len;
		AC_MEMCPY( cp->ldctl_value.bv_val, bv.bv_val, bv.bv_len );
		ctrls[num_ctrls] = cp;
	}

	ber_free_buf( ber );

	if ( ret < 0 ) {
		Debug( LDAP_DEBUG_TRACE,
			"syncprov_done_ctrl: ber_flatten2 failed (%d)\n",
			ret );
		send_ldap_error( op, rs, LDAP_OTHER, "internal error" );
		return LDAP_OTHER;
	}

	return LDAP_SUCCESS;
}

static int
syncprov_sendinfo(
	Operation	*op,
	SlapReply	*rs,
	int			type,
	struct berval *cookie,
	int			refreshDone,
	BerVarray	syncUUIDs,
	int			refreshDeletes )
{
	BerElementBuffer berbuf;
	BerElement *ber = (BerElement *)&berbuf;
	struct berval rspdata;

	int ret;

	ber_init2( ber, NULL, LBER_USE_DER );
	ber_set_option( ber, LBER_OPT_BER_MEMCTX, &op->o_tmpmemctx );

	if ( type ) {
		switch ( type ) {
		case LDAP_TAG_SYNC_NEW_COOKIE:
			Debug( LDAP_DEBUG_SYNC, "%s syncprov_sendinfo: "
				"sending a new cookie=%s\n",
				op->o_log_prefix, cookie->bv_val );
			ber_printf( ber, "tO", type, cookie );
			break;
		case LDAP_TAG_SYNC_REFRESH_DELETE:
		case LDAP_TAG_SYNC_REFRESH_PRESENT:
			Debug( LDAP_DEBUG_SYNC, "%s syncprov_sendinfo: "
				"%s cookie=%s\n",
				op->o_log_prefix,
				type == LDAP_TAG_SYNC_REFRESH_DELETE ? "refreshDelete" : "refreshPresent",
				cookie ? cookie->bv_val : "" );
			ber_printf( ber, "t{", type );
			if ( cookie ) {
				ber_printf( ber, "O", cookie );
			}
			if ( refreshDone == 0 ) {
				ber_printf( ber, "b", refreshDone );
			}
			ber_printf( ber, "N}" );
			break;
		case LDAP_TAG_SYNC_ID_SET:
			Debug( LDAP_DEBUG_SYNC, "%s syncprov_sendinfo: "
				"%s syncIdSet cookie=%s\n",
				op->o_log_prefix, refreshDeletes ? "delete" : "present",
				cookie ? cookie->bv_val : "" );
			ber_printf( ber, "t{", type );
			if ( cookie ) {
				ber_printf( ber, "O", cookie );
			}
			if ( refreshDeletes == 1 ) {
				ber_printf( ber, "b", refreshDeletes );
			}
			ber_printf( ber, "[W]", syncUUIDs );
			ber_printf( ber, "N}" );
			break;
		default:
			Debug( LDAP_DEBUG_TRACE,
				"%s syncprov_sendinfo: invalid syncinfo type (%d)\n",
				op->o_log_prefix, type );
			return LDAP_OTHER;
		}
	}

	ret = ber_flatten2( ber, &rspdata, 0 );

	if ( ret < 0 ) {
		Debug( LDAP_DEBUG_TRACE,
			"syncprov_sendinfo: ber_flatten2 failed (%d)\n",
			ret );
		send_ldap_error( op, rs, LDAP_OTHER, "internal error" );
		return LDAP_OTHER;
	}

	rs->sr_rspoid = LDAP_SYNC_INFO;
	rs->sr_rspdata = &rspdata;
	send_ldap_intermediate( op, rs );
	rs->sr_rspdata = NULL;
	ber_free_buf( ber );

	return LDAP_SUCCESS;
}

/* Find a modtarget in an AVL tree */
static int
sp_avl_cmp( const void *c1, const void *c2 )
{
	const modtarget *m1, *m2;
	int rc;

	m1 = c1; m2 = c2;
	rc = m1->mt_dn.bv_len - m2->mt_dn.bv_len;

	if ( rc ) return rc;
	return ber_bvcmp( &m1->mt_dn, &m2->mt_dn );
}

/* syncprov_findbase:
 *   finds the true DN of the base of a search (with alias dereferencing) and
 * checks to make sure the base entry doesn't get replaced with a different
 * entry (e.g., swapping trees via ModDN, or retargeting an alias). If a
 * change is detected, any persistent search on this base must be terminated /
 * reloaded.
 *   On the first call, we just save the DN and entryID. On subsequent calls
 * we compare the DN and entryID with the saved values.
 */
static int
findbase_cb( Operation *op, SlapReply *rs )
{
	slap_callback *sc = op->o_callback;

	if ( rs->sr_type == REP_SEARCH && rs->sr_err == LDAP_SUCCESS ) {
		fbase_cookie *fc = sc->sc_private;

		/* If no entryID, we're looking for the first time.
		 * Just store whatever we got.
		 */
		if ( fc->fss->s_eid == NOID ) {
			fc->fbase = 2;
			fc->fss->s_eid = rs->sr_entry->e_id;
			ber_dupbv( &fc->fss->s_base, &rs->sr_entry->e_nname );

		} else if ( rs->sr_entry->e_id == fc->fss->s_eid &&
			dn_match( &rs->sr_entry->e_nname, &fc->fss->s_base )) {

		/* OK, the DN is the same and the entryID is the same. */
			fc->fbase = 1;
		}
	}
	if ( rs->sr_err != LDAP_SUCCESS ) {
		Debug( LDAP_DEBUG_ANY, "findbase failed! %d\n", rs->sr_err );
	}
	return LDAP_SUCCESS;
}

static Filter generic_filter = { LDAP_FILTER_PRESENT, { 0 }, NULL };
static struct berval generic_filterstr = BER_BVC("(objectclass=*)");

static int
syncprov_findbase( Operation *op, fbase_cookie *fc )
{
	/* Use basic parameters from syncrepl search, but use
	 * current op's threadctx / tmpmemctx
	 */
	ldap_pvt_thread_mutex_lock( &fc->fss->s_mutex );
	if ( fc->fss->s_flags & PS_FIND_BASE ) {
		slap_callback cb = {0};
		Operation fop;
		SlapReply frs = { REP_RESULT };
		int rc;

		fc->fss->s_flags ^= PS_FIND_BASE;
		ldap_pvt_thread_mutex_unlock( &fc->fss->s_mutex );

		fop = *fc->fss->s_op;

		fop.o_bd = fop.o_bd->bd_self;
		fop.o_hdr = op->o_hdr;
		fop.o_time = op->o_time;
		fop.o_tincr = op->o_tincr;
		fop.o_extra = op->o_extra;

		cb.sc_response = findbase_cb;
		cb.sc_private = fc;

		fop.o_sync_mode = 0;	/* turn off sync mode */
		fop.o_managedsait = SLAP_CONTROL_CRITICAL;
		fop.o_callback = &cb;
		fop.o_tag = LDAP_REQ_SEARCH;
		fop.ors_scope = LDAP_SCOPE_BASE;
		fop.ors_limit = NULL;
		fop.ors_slimit = 1;
		fop.ors_tlimit = SLAP_NO_LIMIT;
		fop.ors_attrs = slap_anlist_no_attrs;
		fop.ors_attrsonly = 1;
		fop.ors_filter = &generic_filter;
		fop.ors_filterstr = generic_filterstr;

		Debug( LDAP_DEBUG_SYNC, "%s syncprov_findbase: searching\n", op->o_log_prefix );
		rc = fop.o_bd->be_search( &fop, &frs );
	} else {
		ldap_pvt_thread_mutex_unlock( &fc->fss->s_mutex );
		fc->fbase = 1;
	}

	/* After the first call, see if the fdn resides in the scope */
	if ( fc->fbase == 1 ) {
		switch ( fc->fss->s_op->ors_scope ) {
		case LDAP_SCOPE_BASE:
			fc->fscope = dn_match( fc->fdn, &fc->fss->s_base );
			break;
		case LDAP_SCOPE_ONELEVEL: {
			struct berval pdn;
			dnParent( fc->fdn, &pdn );
			fc->fscope = dn_match( &pdn, &fc->fss->s_base );
			break; }
		case LDAP_SCOPE_SUBTREE:
			fc->fscope = dnIsSuffix( fc->fdn, &fc->fss->s_base );
			break;
		case LDAP_SCOPE_SUBORDINATE:
			fc->fscope = dnIsSuffix( fc->fdn, &fc->fss->s_base ) &&
				!dn_match( fc->fdn, &fc->fss->s_base );
			break;
		}
	}

	if ( fc->fbase )
		return LDAP_SUCCESS;

	/* If entryID has changed, then the base of this search has
	 * changed. Invalidate the psearch.
	 */
	return LDAP_NO_SUCH_OBJECT;
}

/* syncprov_findcsn:
 *   This function has three different purposes, but they all use a search
 * that filters on entryCSN so they're combined here.
 * 1: at startup time, after a contextCSN has been read from the database,
 * we search for all entries with CSN >= contextCSN in case the contextCSN
 * was not checkpointed at the previous shutdown.
 *
 * 2: when the current contextCSN is known and we have a sync cookie, we search
 * for one entry with CSN = the cookie CSN. If not found, try <= cookie CSN.
 * If an entry is found, the cookie CSN is valid, otherwise it is stale.
 *
 * 3: during a refresh phase, we search for all entries with CSN <= the cookie
 * CSN, and generate Present records for them. We always collect this result
 * in SyncID sets, even if there's only one match.
 */
typedef enum find_csn_t {
	FIND_MAXCSN	= 1,
	FIND_CSN	= 2,
	FIND_PRESENT	= 3
} find_csn_t;

static int
findmax_cb( Operation *op, SlapReply *rs )
{
	if ( rs->sr_type == REP_SEARCH && rs->sr_err == LDAP_SUCCESS ) {
		struct berval *maxcsn = op->o_callback->sc_private;
		Attribute *a = attr_find( rs->sr_entry->e_attrs,
			slap_schema.si_ad_entryCSN );

		if ( a && ber_bvcmp( &a->a_vals[0], maxcsn ) > 0 &&
			slap_parse_csn_sid( &a->a_vals[0] ) == slap_serverID ) {
			maxcsn->bv_len = a->a_vals[0].bv_len;
			strcpy( maxcsn->bv_val, a->a_vals[0].bv_val );
		}
	}
	return LDAP_SUCCESS;
}

static int
findcsn_cb( Operation *op, SlapReply *rs )
{
	slap_callback *sc = op->o_callback;

	/* We just want to know that at least one exists, so it's OK if
	 * we exceed the unchecked limit.
	 */
	if ( rs->sr_err == LDAP_ADMINLIMIT_EXCEEDED ||
		(rs->sr_type == REP_SEARCH && rs->sr_err == LDAP_SUCCESS )) {
		sc->sc_private = (void *)1;
	}
	return LDAP_SUCCESS;
}

/* Build a list of entryUUIDs for sending in a SyncID set */

#define UUID_LEN	16

typedef struct fpres_cookie {
	int num;
	BerVarray uuids;
	char *last;
} fpres_cookie;

static int
findpres_cb( Operation *op, SlapReply *rs )
{
	slap_callback *sc = op->o_callback;
	fpres_cookie *pc = sc->sc_private;
	Attribute *a;
	int ret = SLAP_CB_CONTINUE;

	switch ( rs->sr_type ) {
	case REP_SEARCH:
		a = attr_find( rs->sr_entry->e_attrs, slap_schema.si_ad_entryUUID );
		if ( a ) {
			pc->uuids[pc->num].bv_val = pc->last;
			AC_MEMCPY( pc->uuids[pc->num].bv_val, a->a_nvals[0].bv_val,
				pc->uuids[pc->num].bv_len );
			pc->num++;
			pc->last = pc->uuids[pc->num].bv_val;
			pc->uuids[pc->num].bv_val = NULL;
		}
		ret = LDAP_SUCCESS;
		if ( pc->num != SLAP_SYNCUUID_SET_SIZE )
			break;
		/* FALLTHRU */
	case REP_RESULT:
		ret = rs->sr_err;
		if ( pc->num ) {
			ret = syncprov_sendinfo( op, rs, LDAP_TAG_SYNC_ID_SET, NULL,
				0, pc->uuids, 0 );
			pc->uuids[pc->num].bv_val = pc->last;
			pc->num = 0;
			pc->last = pc->uuids[0].bv_val;
		}
		break;
	default:
		break;
	}
	return ret;
}

static int
syncprov_findcsn( Operation *op, find_csn_t mode, struct berval *csn )
{
	slap_overinst		*on = (slap_overinst *)op->o_bd->bd_info;
	syncprov_info_t		*si = on->on_bi.bi_private;

	slap_callback cb = {0};
	Operation fop;
	SlapReply frs = { REP_RESULT };
	char buf[LDAP_PVT_CSNSTR_BUFSIZE + STRLENOF("(entryCSN<=)")];
	char cbuf[LDAP_PVT_CSNSTR_BUFSIZE];
	struct berval maxcsn;
	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;

	if ( mode != FIND_MAXCSN ) {
		srs = op->o_controls[slap_cids.sc_LDAPsync];
	}

	Debug( LDAP_DEBUG_SYNC, "%s syncprov_findcsn: mode=%s csn=%s\n",
		op->o_log_prefix,
		mode == FIND_MAXCSN ?
			"FIND_MAXCSN" :
			mode == FIND_CSN ?
				"FIND_CSN" :
				"FIND_PRESENT",
		csn ? csn->bv_val : "" );

	fop = *op;
	fop.o_sync_mode &= SLAP_CONTROL_MASK;	/* turn off sync_mode */
	/* We want pure entries, not referrals */
	fop.o_managedsait = SLAP_CONTROL_CRITICAL;

	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;
	fop.ors_limit = NULL;
	fop.ors_tlimit = SLAP_NO_LIMIT;
	fop.ors_filter = &cf;
	fop.ors_filterstr.bv_val = buf;

again:
	switch( mode ) {
	case FIND_MAXCSN:
		cf.f_choice = LDAP_FILTER_GE;
		/* If there are multiple CSNs, use the one with our serverID */
		for ( i=0; i<si->si_numcsns; i++) {
			if ( slap_serverID == si->si_sids[i] ) {
				maxid = i;
				break;
			}
		}
		if ( i == si->si_numcsns ) {
			/* No match: this is multimaster, and none of the content in the DB
			 * originated locally. Treat like no CSN.
			 */
			return LDAP_NO_SUCH_OBJECT;
		}
		cf.f_av_value = si->si_ctxcsn[maxid];
		fop.ors_filterstr.bv_len = snprintf( buf, sizeof( buf ),
			"(entryCSN>=%s)", cf.f_av_value.bv_val );
		if ( 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, cf.f_av_value.bv_val );
		maxcsn.bv_val = cbuf;
		maxcsn.bv_len = cf.f_av_value.bv_len;
		break;
	case FIND_CSN:
		if ( BER_BVISEMPTY( &cf.f_av_value )) {
			cf.f_av_value = *csn;
		}
		fop.o_dn = op->o_bd->be_rootdn;
		fop.o_ndn = op->o_bd->be_rootndn;
		fop.o_req_dn = op->o_bd->be_suffix[0];
		fop.o_req_ndn = op->o_bd->be_nsuffix[0];
		/* Look for exact match the first time */
		if ( findcsn_retry ) {
			cf.f_choice = LDAP_FILTER_EQUALITY;
			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 = snprintf( buf, sizeof( buf ),
				"(entryCSN<=%s)", cf.f_av_value.bv_val );
		}
		if ( fop.ors_filterstr.bv_len >= sizeof( buf ) ) {
			return LDAP_OTHER;
		}
		fop.ors_attrsonly = 1;
		fop.ors_attrs = slap_anlist_no_attrs;
		fop.ors_slimit = 1;
		cb.sc_private = NULL;
		cb.sc_response = findcsn_cb;
		break;
	case FIND_PRESENT:
		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;
		cb.sc_private = &pcookie;
		cb.sc_response = findpres_cb;
		pcookie.num = 0;

		/* preallocate storage for a full set */
		pcookie.uuids = op->o_tmpalloc( (SLAP_SYNCUUID_SET_SIZE+1) *
			sizeof(struct berval) + SLAP_SYNCUUID_SET_SIZE * UUID_LEN,
			op->o_tmpmemctx );
		pcookie.last = (char *)(pcookie.uuids + SLAP_SYNCUUID_SET_SIZE+1);
		pcookie.uuids[0].bv_val = pcookie.last;
		pcookie.uuids[0].bv_len = UUID_LEN;
		for (i=1; i<SLAP_SYNCUUID_SET_SIZE; i++) {
			pcookie.uuids[i].bv_val = pcookie.uuids[i-1].bv_val + UUID_LEN;
			pcookie.uuids[i].bv_len = UUID_LEN;
		}
		break;
	}

	fop.o_bd->bd_info = (BackendInfo *)on->on_info;
	fop.o_bd->be_search( &fop, &frs );
	fop.o_bd->bd_info = (BackendInfo *)on;

	switch( mode ) {
	case FIND_MAXCSN:
		if ( ber_bvcmp( &si->si_ctxcsn[maxid], &maxcsn )) {
#ifdef CHECK_CSN
			Syntax *syn = slap_schema.si_ad_contextCSN->ad_type->sat_syntax;
			assert( !syn->ssyn_validate( syn, &maxcsn ));
#endif
			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. */
		Debug( LDAP_DEBUG_SYNC, "%s syncprov_findcsn: csn%s=%s %sfound\n",
			op->o_log_prefix,
			cf.f_choice == LDAP_FILTER_EQUALITY ? "=" : "<",
			cf.f_av_value.bv_val, cb.sc_private ? "" : "not " );
		if ( !cb.sc_private ) {
			/* If we didn't find an exact match, then try for <= */
			if ( findcsn_retry ) {
				findcsn_retry = 0;
				rs_reinit( &frs, REP_RESULT );
				goto again;
			}
			rc = LDAP_NO_SUCH_OBJECT;
		}
		break;
	case FIND_PRESENT:
		op->o_tmpfree( pcookie.uuids, op->o_tmpmemctx );
		break;
	}

	return rc;
}

static void free_resinfo( syncres *sr )
{
	syncres **st;
	int freeit = 0;
	ldap_pvt_thread_mutex_lock( &sr->s_info->ri_mutex );
	for (st = &sr->s_info->ri_list; *st; st = &(*st)->s_rilist) {
		if (*st == sr) {
			*st = sr->s_rilist;
			break;
		}
	}
	if ( !sr->s_info->ri_list )
		freeit = 1;
	ldap_pvt_thread_mutex_unlock( &sr->s_info->ri_mutex );
	if ( freeit ) {
		ldap_pvt_thread_mutex_destroy( &sr->s_info->ri_mutex );
		if ( sr->s_info->ri_e )
			entry_free( sr->s_info->ri_e );
		if ( !BER_BVISNULL( &sr->s_info->ri_cookie ))
			ch_free( sr->s_info->ri_cookie.bv_val );
		ch_free( sr->s_info );
	}
}

#define FS_UNLINK	1
#define FS_LOCK		2

static int
syncprov_free_syncop( syncops *so, int flags )
{
	syncres *sr, *srnext;
	GroupAssertion *ga, *gnext;

	if ( flags & FS_LOCK )
		ldap_pvt_thread_mutex_lock( &so->s_mutex );
	/* already being freed, or still in use */
	if ( !so->s_inuse || --so->s_inuse > 0 ) {
		if ( flags & FS_LOCK )
			ldap_pvt_thread_mutex_unlock( &so->s_mutex );
		return 0;
	}
	ldap_pvt_thread_mutex_unlock( &so->s_mutex );
	if (( flags & FS_UNLINK ) && so->s_si ) {
		syncops **sop;
		ldap_pvt_thread_mutex_lock( &so->s_si->si_ops_mutex );
		for ( sop = &so->s_si->si_ops; *sop; sop = &(*sop)->s_next ) {
			if ( *sop == so ) {
				*sop = so->s_next;
				break;
			}
		}
		ldap_pvt_thread_mutex_unlock( &so->s_si->si_ops_mutex );
	}
	if ( so->s_flags & PS_IS_DETACHED ) {
		filter_free( so->s_op->ors_filter );
		for ( ga = so->s_op->o_groups; ga; ga=gnext ) {
			gnext = ga->ga_next;
			ch_free( ga );
		}
		ch_free( so->s_op );
	}
	ch_free( so->s_base.bv_val );
	for ( sr=so->s_res; sr; sr=srnext ) {
		srnext = sr->s_next;
		free_resinfo( sr );
		ch_free( sr );
	}
	ldap_pvt_thread_mutex_destroy( &so->s_mutex );
	ch_free( so );
	return 1;
}

/* Send a persistent search response */
static int
syncprov_sendresp( Operation *op, resinfo *ri, syncops *so, int mode )
{
	SlapReply rs = { REP_SEARCH };
	struct berval cookie, csns[2];
	Entry e_uuid = {0};
	Attribute a_uuid = {0};

	if ( so->s_op->o_abandon )
		return SLAPD_ABANDON;

	rs.sr_ctrls = op->o_tmpalloc( sizeof(LDAPControl *)*2, op->o_tmpmemctx );
	rs.sr_ctrls[1] = NULL;
	rs.sr_flags = REP_CTRLS_MUSTBEFREED;
	csns[0] = ri->ri_csn;
	BER_BVZERO( &csns[1] );
	slap_compose_sync_cookie( op, &cookie, csns, so->s_rid,
				 slap_serverID ? slap_serverID : -1, NULL );

#ifdef LDAP_DEBUG
	if ( so->s_sid > 0 ) {
		Debug( LDAP_DEBUG_SYNC, "%s syncprov_sendresp: to=%03x, cookie=%s\n",
			op->o_log_prefix, so->s_sid, cookie.bv_val );
	} else {
		Debug( LDAP_DEBUG_SYNC, "%s syncprov_sendresp: cookie=%s\n",
			op->o_log_prefix, cookie.bv_val );
	}
#endif

	e_uuid.e_attrs = &a_uuid;
	a_uuid.a_desc = slap_schema.si_ad_entryUUID;
	a_uuid.a_nvals = &ri->ri_uuid;
	rs.sr_err = syncprov_state_ctrl( op, &rs, &e_uuid,
		mode, rs.sr_ctrls, 0, 1, &cookie );
	op->o_tmpfree( cookie.bv_val, op->o_tmpmemctx );

	rs.sr_entry = &e_uuid;
	if ( mode == LDAP_SYNC_ADD || mode == LDAP_SYNC_MODIFY ) {
		e_uuid = *ri->ri_e;
		e_uuid.e_private = NULL;
	}

	switch( mode ) {
	case LDAP_SYNC_ADD:
		if ( ri->ri_isref && so->s_op->o_managedsait <= SLAP_CONTROL_IGNORED ) {
			rs.sr_ref = get_entry_referrals( op, rs.sr_entry );
			rs.sr_err = send_search_reference( op, &rs );
			ber_bvarray_free( rs.sr_ref );
			break;
		}
		/* fallthru */
	case LDAP_SYNC_MODIFY:
		Debug( LDAP_DEBUG_SYNC, "%s syncprov_sendresp: sending %s, dn=%s\n",
			op->o_log_prefix,
			mode == LDAP_SYNC_ADD ? "LDAP_SYNC_ADD" : "LDAP_SYNC_MODIFY",
			e_uuid.e_nname.bv_val );
		rs.sr_attrs = op->ors_attrs;
		rs.sr_err = send_search_entry( op, &rs );
		break;
	case LDAP_SYNC_DELETE:
		Debug( LDAP_DEBUG_SYNC, "%s syncprov_sendresp: "
			"sending LDAP_SYNC_DELETE, dn=%s\n",
			op->o_log_prefix, ri->ri_dn.bv_val );
		e_uuid.e_attrs = NULL;
		e_uuid.e_name = ri->ri_dn;
		e_uuid.e_nname = ri->ri_ndn;
		if ( ri->ri_isref && so->s_op->o_managedsait <= SLAP_CONTROL_IGNORED ) {
			struct berval bv = BER_BVNULL;
			rs.sr_ref = &bv;
			rs.sr_err = send_search_reference( op, &rs );
		} else {
			rs.sr_err = send_search_entry( op, &rs );
		}
		break;
	default:
		assert(0);
	}
	return rs.sr_err;
}

static void
syncprov_qstart( syncops *so );

/* Play back queued responses */
static int
syncprov_qplay( Operation *op, syncops *so )
{
	syncres *sr;
	int rc = 0;

	do {
		ldap_pvt_thread_mutex_lock( &so->s_mutex );
		sr = so->s_res;
		/* Exit loop with mutex held */
		if ( !sr )
			break;
		so->s_res = sr->s_next;
		if ( !so->s_res )
			so->s_restail = NULL;
		ldap_pvt_thread_mutex_unlock( &so->s_mutex );

		if ( !so->s_op->o_abandon ) {

			if ( sr->s_mode == LDAP_SYNC_NEW_COOKIE ) {
				SlapReply rs = { REP_INTERMEDIATE };

				rc = syncprov_sendinfo( op, &rs, LDAP_TAG_SYNC_NEW_COOKIE,
					&sr->s_info->ri_cookie, 0, NULL, 0 );
			} else {
				rc = syncprov_sendresp( op, sr->s_info, so, sr->s_mode );
			}
		}

		free_resinfo( sr );
		ch_free( sr );

		if ( so->s_op->o_abandon )
			continue;

		/* Exit loop with mutex held */
		ldap_pvt_thread_mutex_lock( &so->s_mutex );
		break;

	} while (1);

	/* We now only send one change at a time, to prevent one
	 * psearch from hogging all the CPU. Resubmit this task if
	 * there are more responses queued and no errors occurred.
	 */

	if ( rc == 0 && so->s_res ) {
		syncprov_qstart( so );
	}

	return rc;
}

/* task for playing back queued responses */
static void *
syncprov_qtask( void *ctx, void *arg )
{
	syncops *so = arg;
	OperationBuffer opbuf;