conn.c

/* $OpenLDAP$ */
/* This work is part of OpenLDAP Software <http://www.openldap.org/>.
 *
 * Copyright 1999-2021 The OpenLDAP Foundation.
 * Portions Copyright 2001-2003 Pierangelo Masarati.
 * Portions Copyright 1999-2003 Howard Chu.
 * 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 the Howard Chu for inclusion
 * in OpenLDAP Software and subsequently enhanced by Pierangelo
 * Masarati.
 */

#include "portable.h"

#include <stdio.h>

#include <ac/errno.h>
#include <ac/socket.h>
#include <ac/string.h>


#define AVL_INTERNAL
#include "slap.h"
#include "../back-ldap/back-ldap.h"
#include "back-meta.h"

/*
 * meta_back_conndn_cmp
 *
 * compares two struct metaconn based on the value of the conn pointer
 * and of the local DN; used by avl stuff
 */
int
meta_back_conndn_cmp(
	const void *c1,
	const void *c2 )
{
	metaconn_t	*mc1 = ( metaconn_t * )c1;
        metaconn_t	*mc2 = ( metaconn_t * )c2;
	int		rc;
	
	/* If local DNs don't match, it is definitely not a match */
	/* For shared sessions, conn is NULL. Only explicitly
	 * bound sessions will have non-NULL conn.
	 */
	rc = SLAP_PTRCMP( mc1->mc_conn, mc2->mc_conn );
	if ( rc == 0 ) {
		rc = ber_bvcmp( &mc1->mc_local_ndn, &mc2->mc_local_ndn );
	}

	return rc;
}

/*
 * meta_back_conndnmc_cmp
 *
 * compares two struct metaconn based on the value of the conn pointer,
 * the local DN and the struct pointer; used by avl stuff
 */
static int
meta_back_conndnmc_cmp(
	const void *c1,
	const void *c2 )
{
	metaconn_t	*mc1 = ( metaconn_t * )c1;
        metaconn_t	*mc2 = ( metaconn_t * )c2;
	int		rc;
	
	/* If local DNs don't match, it is definitely not a match */
	/* For shared sessions, conn is NULL. Only explicitly
	 * bound sessions will have non-NULL conn.
	 */
	rc = SLAP_PTRCMP( mc1->mc_conn, mc2->mc_conn );
	if ( rc == 0 ) {
		rc = ber_bvcmp( &mc1->mc_local_ndn, &mc2->mc_local_ndn );
		if ( rc == 0 ) {
			rc = SLAP_PTRCMP( mc1, mc2 );
		}
	}

	return rc;
}

/*
 * meta_back_conn_cmp
 *
 * compares two struct metaconn based on the value of the conn pointer;
 * used by avl stuff
 */
int
meta_back_conn_cmp(
	const void *c1,
	const void *c2 )
{
	metaconn_t	*mc1 = ( metaconn_t * )c1;
        metaconn_t	*mc2 = ( metaconn_t * )c2;
	
	/* For shared sessions, conn is NULL. Only explicitly
	 * bound sessions will have non-NULL conn.
	 */
	return SLAP_PTRCMP( mc1->mc_conn, mc2->mc_conn );
}

/*
 * meta_back_conndn_dup
 *
 * returns -1 in case a duplicate struct metaconn has been inserted;
 * used by avl stuff
 */
int
meta_back_conndn_dup(
	void *c1,
	void *c2 )
{
	metaconn_t	*mc1 = ( metaconn_t * )c1;
	metaconn_t	*mc2 = ( metaconn_t * )c2;

	/* Cannot have more than one shared session with same DN */
	if ( mc1->mc_conn == mc2->mc_conn &&
		dn_match( &mc1->mc_local_ndn, &mc2->mc_local_ndn ) )
	{
		return -1;
	}
		
	return 0;
}

/*
 * Debug stuff (got it from libavl)
 */
#if META_BACK_PRINT_CONNTREE > 0
static void
meta_back_print( metaconn_t *mc, char *avlstr )
{
	int	i;

	fputs( "targets=[", stderr );
	for ( i = 0; i < mc->mc_info->mi_ntargets; i++ ) {
		fputc( mc->mc_conns[ i ].msc_ld ? '*' : 'o', stderr);
	}
	fputc( ']', stderr );

	fprintf( stderr, " mc=%p local=\"%s\" conn=%p refcnt=%d%s %s\n",
		(void *)mc,
		mc->mc_local_ndn.bv_val ? mc->mc_local_ndn.bv_val : "",
		(void *)mc->mc_conn,
		mc->mc_refcnt,
		LDAP_BACK_CONN_TAINTED( mc ) ? " tainted" : "",
		avlstr );
}

static void
meta_back_ravl_print( TAvlnode *root, int depth )
{
	int     	i;

	if ( root == 0 ) {
		return;
	}
	
	meta_back_ravl_print( root->avl_right, depth + 1 );
	
	for ( i = 0; i < depth; i++ ) {
		fprintf( stderr, "-" );
	}
	fputc( ' ', stderr );

	meta_back_print( (metaconn_t *)root->avl_data,
		avl_bf2str( root->avl_bf ) );

	meta_back_ravl_print( root->avl_left, depth + 1 );
}

/* NOTE: duplicate from back-ldap/bind.c */
static char* priv2str[] = {
	"privileged",
	"privileged/TLS",
	"anonymous",
	"anonymous/TLS",
	"bind",
	"bind/TLS",
	NULL
};

void
meta_back_print_conntree( metainfo_t *mi, char *msg )
{
	int	c;

	fprintf( stderr, "========> %s\n", msg );
	
	for ( c = LDAP_BACK_PCONN_FIRST; c < LDAP_BACK_PCONN_LAST; c++ ) {
		int		i = 0;
		metaconn_t	*mc;

		fprintf( stderr, "  %s[%d]\n", priv2str[ c ], mi->mi_conn_priv[ c ].mic_num );

		LDAP_TAILQ_FOREACH( mc, &mi->mi_conn_priv[ c ].mic_priv, mc_q )
		{
			fprintf( stderr, "    [%d] ", i );
			meta_back_print( mc, "" );
			i++;
		}
	}
	
	if ( mi->mi_conninfo.lai_tree == NULL ) {
		fprintf( stderr, "\t(empty)\n" );

	} else {
		meta_back_ravl_print( mi->mi_conninfo.lai_tree, 0 );
	}
	
	fprintf( stderr, "<======== %s\n", msg );
}
#endif /* META_BACK_PRINT_CONNTREE */
/*
 * End of debug stuff
 */

/*
 * metaconn_alloc
 * 
 * Allocates a connection structure, making room for all the referenced targets
 */
static metaconn_t *
metaconn_alloc(
       	Operation 		*op )
{
	metainfo_t	*mi = ( metainfo_t * )op->o_bd->be_private;
	metaconn_t	*mc;
	int		ntargets = mi->mi_ntargets;

	assert( ntargets > 0 );

	/* malloc all in one */
	mc = ( metaconn_t * )ch_calloc( 1, sizeof( metaconn_t )
		+ sizeof( metasingleconn_t ) * ( ntargets - 1 ) );
	if ( mc == NULL ) {
		return NULL;
	}

	mc->mc_info = mi;

	mc->mc_authz_target = META_BOUND_NONE;
	mc->mc_refcnt = 1;

	return mc;
}

/*
 * meta_back_init_one_conn
 * 
 * Initializes one connection
 */
int
meta_back_init_one_conn(
	Operation		*op,
	SlapReply		*rs,
	metaconn_t		*mc,
	int			candidate,
	int			ispriv,
	ldap_back_send_t	sendok,
	int			dolock )
{
	metainfo_t		*mi = ( metainfo_t * )op->o_bd->be_private;
	metatarget_t		*mt = mi->mi_targets[ candidate ];
	metasingleconn_t	*msc = &mc->mc_conns[ candidate ];
	int			version;
	dncookie		dc;
	int			isauthz = ( candidate == mc->mc_authz_target );
	int			do_return = 0;
#ifdef HAVE_TLS
	int			is_ldaps = 0;
	int			do_start_tls = 0;
#endif /* HAVE_TLS */

	/* if the server is quarantined, and
	 * - the current interval did not expire yet, or
	 * - no more retries should occur,
	 * don't return the connection */
	if ( mt->mt_isquarantined ) {
		slap_retry_info_t	*ri = &mt->mt_quarantine;
		int			dont_retry = 0;

		if ( mt->mt_quarantine.ri_interval ) {
			ldap_pvt_thread_mutex_lock( &mt->mt_quarantine_mutex );
			dont_retry = ( mt->mt_isquarantined > LDAP_BACK_FQ_NO );
			if ( dont_retry ) {
				dont_retry = ( ri->ri_num[ ri->ri_idx ] == SLAP_RETRYNUM_TAIL
					|| slap_get_time() < ri->ri_last + ri->ri_interval[ ri->ri_idx ] );
				if ( !dont_retry ) {
					Debug(LDAP_DEBUG_ANY,
					      "%s meta_back_init_one_conn[%d]: quarantine " "retry block #%d try #%d.\n",
					      op->o_log_prefix,
					      candidate, ri->ri_idx,
					      ri->ri_count );

					mt->mt_isquarantined = LDAP_BACK_FQ_RETRYING;
				}

			}
			ldap_pvt_thread_mutex_unlock( &mt->mt_quarantine_mutex );
		}

		if ( dont_retry ) {
			rs->sr_err = LDAP_UNAVAILABLE;
			if ( op->o_conn && ( sendok & LDAP_BACK_SENDERR ) ) {
				rs->sr_text = "Target is quarantined";
				send_ldap_result( op, rs );
			}
			return rs->sr_err;
		}
	}

retry_lock:;
	if ( dolock ) {
		ldap_pvt_thread_mutex_lock( &mi->mi_conninfo.lai_mutex );
	}

	/*
	 * Already init'ed
	 */
	if ( LDAP_BACK_CONN_ISBOUND( msc )
		|| LDAP_BACK_CONN_ISANON( msc ) )
	{
		assert( msc->msc_ld != NULL );
		rs->sr_err = LDAP_SUCCESS;
		do_return = 1;

	} else if ( META_BACK_CONN_CREATING( msc )
		|| LDAP_BACK_CONN_BINDING( msc ) )
	{
		if ( !LDAP_BACK_USE_TEMPORARIES( mi ) ) {
			if ( dolock ) {
				ldap_pvt_thread_mutex_unlock( &mi->mi_conninfo.lai_mutex );
			}

			ldap_pvt_thread_yield();
			goto retry_lock;
		}

		/* sounds more appropriate */
		rs->sr_err = LDAP_BUSY;
		rs->sr_text = "No connections to target are available";
		do_return = 1;

	} else if ( META_BACK_CONN_INITED( msc ) ) {
		assert( msc->msc_ld != NULL );
		rs->sr_err = LDAP_SUCCESS;
		do_return = 1;

	} else {
		/*
		 * creating...
		 */
		META_BACK_CONN_CREATING_SET( msc );
	}

	if ( dolock ) {
		ldap_pvt_thread_mutex_unlock( &mi->mi_conninfo.lai_mutex );
	}

	if ( do_return ) {
		if ( rs->sr_err != LDAP_SUCCESS
			&& op->o_conn
			&& ( sendok & LDAP_BACK_SENDERR ) )
		{
			send_ldap_result( op, rs );
		}

		return rs->sr_err;
	}

	assert( msc->msc_ld == NULL );
       
	/*
	 * Attempts to initialize the connection to the target ds
	 */
	ldap_pvt_thread_mutex_lock( &mt->mt_uri_mutex );
	rs->sr_err = ldap_initialize( &msc->msc_ld, mt->mt_uri );
#ifdef HAVE_TLS
	is_ldaps = ldap_is_ldaps_url( mt->mt_uri );
#endif /* HAVE_TLS */
	ldap_pvt_thread_mutex_unlock( &mt->mt_uri_mutex );
	if ( rs->sr_err != LDAP_SUCCESS ) {
		goto error_return;
	}

	/*
	 * Set LDAP version. This will always succeed: If the client
	 * bound with a particular version, then so can we.
	 */
	if ( mt->mt_version != 0 ) {
		version = mt->mt_version;

	} else if ( op->o_conn->c_protocol != 0 ) {
		version = op->o_conn->c_protocol;

	} else {
		version = LDAP_VERSION3;
	}
	ldap_set_option( msc->msc_ld, LDAP_OPT_PROTOCOL_VERSION, &version );
	ldap_set_urllist_proc( msc->msc_ld, mt->mt_urllist_f, mt->mt_urllist_p );

	/* automatically chase referrals ("chase-referrals [{yes|no}]" statement) */
	ldap_set_option( msc->msc_ld, LDAP_OPT_REFERRALS,
		META_BACK_TGT_CHASE_REFERRALS( mt ) ? LDAP_OPT_ON : LDAP_OPT_OFF );

	slap_client_keepalive(msc->msc_ld, &mt->mt_tls.sb_keepalive);

	if ( mt->mt_tls.sb_tcp_user_timeout > 0 ) {
		ldap_set_option( msc->msc_ld, LDAP_OPT_TCP_USER_TIMEOUT,
				&mt->mt_tls.sb_tcp_user_timeout );
	}



#ifdef HAVE_TLS
	{
		slap_bindconf *sb = NULL;

		if ( ispriv ) {
			sb = &mt->mt_idassert.si_bc;
		} else {
			sb = &mt->mt_tls;
		}

		bindconf_tls_set( sb, msc->msc_ld );

		if ( !is_ldaps ) {
			if ( META_BACK_TGT_USE_TLS( mt )
				|| ( op->o_conn->c_is_tls && META_BACK_TGT_PROPAGATE_TLS( mt ) ) )
			{
				do_start_tls = 1;
			}
		}
	}

	/* start TLS ("tls [try-]{start|propagate}" statement) */
	if ( do_start_tls ) {
#ifdef SLAP_STARTTLS_ASYNCHRONOUS
		/*
		 * use asynchronous StartTLS; in case, chase referral
		 * FIXME: OpenLDAP does not return referral on StartTLS yet
		 */
		int		msgid;

		rs->sr_err = ldap_start_tls( msc->msc_ld, NULL, NULL, &msgid );
		if ( rs->sr_err == LDAP_SUCCESS ) {
			LDAPMessage	*res = NULL;
			int		rc, nretries = mt->mt_nretries;
			struct timeval	tv;

			LDAP_BACK_TV_SET( &tv );

retry:;
			rc = ldap_result( msc->msc_ld, msgid, LDAP_MSG_ALL, &tv, &res );
			switch ( rc ) {
			case -1:
				rs->sr_err = LDAP_UNAVAILABLE;
				rs->sr_text = "Remote server down";
				break;

			case 0:
				if ( nretries != 0 ) {
					if ( nretries > 0 ) {
						nretries--;
					}
					LDAP_BACK_TV_SET( &tv );
					goto retry;
				}
				rs->sr_err = LDAP_OTHER;
				rs->sr_text = "Timeout, no more retries";
				break;

			default:
				/* only touch when activity actually took place... */
				if ( mi->mi_idle_timeout != 0 && msc->msc_time < op->o_time ) {
					msc->msc_time = op->o_time;
				}
				break;
			}

			if ( rc == LDAP_RES_EXTENDED ) {
				struct berval	*data = NULL;

				/* NOTE: right now, data is unused, so don't get it */
				rs->sr_err = ldap_parse_extended_result( msc->msc_ld,
					res, NULL, NULL /* &data */ , 0 );
				if ( rs->sr_err == LDAP_SUCCESS ) {
					int		err;

					/* FIXME: matched? referrals? response controls? */
					rs->sr_err = ldap_parse_result( msc->msc_ld,
						res, &err, NULL, NULL, NULL, NULL, 1 );
					res = NULL;

					if ( rs->sr_err == LDAP_SUCCESS ) {
						rs->sr_err = err;
					}
					rs->sr_err = slap_map_api2result( rs );
					
					/* FIXME: in case a referral 
					 * is returned, should we try
					 * using it instead of the 
					 * configured URI? */
					if ( rs->sr_err == LDAP_SUCCESS ) {
						rs->sr_err = ldap_install_tls( msc->msc_ld );

					} else if ( rs->sr_err == LDAP_REFERRAL ) {
						/* FIXME: LDAP_OPERATIONS_ERROR? */
						rs->sr_err = LDAP_OTHER;
						rs->sr_text = "Unwilling to chase referral "
							"returned by Start TLS exop";
					}

					if ( data ) {
						ber_bvfree( data );
					}
				}

			} else {
				rs->sr_err = LDAP_OTHER;
				rs->sr_text = "Unknown response to StartTLS request :"
					" an ExtendedResponse is expected";
			}

			if ( res != NULL ) {
				ldap_msgfree( res );
			}
		}
#else /* ! SLAP_STARTTLS_ASYNCHRONOUS */
		/*
		 * use synchronous StartTLS
		 */
		rs->sr_err = ldap_start_tls_s( msc->msc_ld, NULL, NULL );
#endif /* ! SLAP_STARTTLS_ASYNCHRONOUS */

		/* if StartTLS is requested, only attempt it if the URL
		 * is not "ldaps://"; this may occur not only in case
		 * of misconfiguration, but also when used in the chain 
		 * overlay, where the "uri" can be parsed out of a referral */
		if ( rs->sr_err == LDAP_SERVER_DOWN
			|| ( rs->sr_err != LDAP_SUCCESS
				&& META_BACK_TGT_TLS_CRITICAL( mt ) ) )
		{

#ifdef DEBUG_205
			Debug( LDAP_DEBUG_ANY,
				"### %s meta_back_init_one_conn(TLS) "
				"ldap_unbind_ext[%d] ld=%p\n",
				op->o_log_prefix, candidate,
				(void *)msc->msc_ld );
#endif /* DEBUG_205 */

			/* need to trash a failed Start TLS */
			meta_clear_one_candidate( op, mc, candidate );
			goto error_return;
		}
	}
#endif /* HAVE_TLS */

	/*
	 * Set the network timeout if set
	 */
	if ( mt->mt_network_timeout != 0 ) {
		struct timeval	network_timeout;

		network_timeout.tv_usec = 0;
		network_timeout.tv_sec = mt->mt_network_timeout;

		ldap_set_option( msc->msc_ld, LDAP_OPT_NETWORK_TIMEOUT,
				(void *)&network_timeout );
	}

	/*
	 * If the connection DN is not null, an attempt to rewrite it is made
	 */

	if ( ispriv ) {
		if ( !BER_BVISNULL( &mt->mt_idassert_authcDN ) ) {
			ber_bvreplace( &msc->msc_bound_ndn, &mt->mt_idassert_authcDN );
			if ( !BER_BVISNULL( &mt->mt_idassert_passwd ) ) {
				if ( !BER_BVISNULL( &msc->msc_cred ) ) {
					memset( msc->msc_cred.bv_val, 0,
						msc->msc_cred.bv_len );
				}
				ber_bvreplace( &msc->msc_cred, &mt->mt_idassert_passwd );
			}
			LDAP_BACK_CONN_ISIDASSERT_SET( msc );

		} else {
			ber_bvreplace( &msc->msc_bound_ndn, &slap_empty_bv );
		}

	} else {
		if ( !BER_BVISNULL( &msc->msc_cred ) ) {
			memset( msc->msc_cred.bv_val, 0, msc->msc_cred.bv_len );
			ber_memfree_x( msc->msc_cred.bv_val, NULL );
			BER_BVZERO( &msc->msc_cred );
		}
		if ( !BER_BVISNULL( &msc->msc_bound_ndn ) ) {
			ber_memfree_x( msc->msc_bound_ndn.bv_val, NULL );
			BER_BVZERO( &msc->msc_bound_ndn );
		}
		if ( !BER_BVISEMPTY( &op->o_ndn )
			&& SLAP_IS_AUTHZ_BACKEND( op )
			&& isauthz )
		{
			dc.target = mt;
			dc.conn = op->o_conn;
			dc.rs = rs;
			dc.ctx = "bindDN";
		
			/*
			 * Rewrite the bind dn if needed
			 */
			if ( ldap_back_dn_massage( &dc, &op->o_conn->c_dn,
						&msc->msc_bound_ndn ) )
			{

#ifdef DEBUG_205
				Debug( LDAP_DEBUG_ANY,
					"### %s meta_back_init_one_conn(rewrite) "
					"ldap_unbind_ext[%d] ld=%p\n",
					op->o_log_prefix, candidate,
					(void *)msc->msc_ld );
#endif /* DEBUG_205 */

				/* need to trash a connection not fully established */
				meta_clear_one_candidate( op, mc, candidate );
				goto error_return;
			}
			
			/* copy the DN if needed */
			if ( msc->msc_bound_ndn.bv_val == op->o_conn->c_dn.bv_val ) {
				ber_dupbv( &msc->msc_bound_ndn, &op->o_conn->c_dn );
			}

			assert( !BER_BVISNULL( &msc->msc_bound_ndn ) );

		} else {
			ber_dupbv( &msc->msc_bound_ndn, (struct berval *)&slap_empty_bv );
		}
	}

	assert( !BER_BVISNULL( &msc->msc_bound_ndn ) );

error_return:;
	if ( dolock ) {
		ldap_pvt_thread_mutex_lock( &mi->mi_conninfo.lai_mutex );
	}
	META_BACK_CONN_CREATING_CLEAR( msc );
	if ( rs->sr_err == LDAP_SUCCESS ) {
		/*
		 * Sets a cookie for the rewrite session
		 */
		( void )rewrite_session_init( mt->mt_rwmap.rwm_rw, op->o_conn );
		META_BACK_CONN_INITED_SET( msc );
	}
	if ( dolock ) {
		ldap_pvt_thread_mutex_unlock( &mi->mi_conninfo.lai_mutex );
	}

	if ( rs->sr_err != LDAP_SUCCESS ) {
		/* Get the error message and print it in TRACE mode */
		if ( LogTest( LDAP_DEBUG_TRACE ) ) {
			Log( LDAP_DEBUG_TRACE, ldap_syslog_level, "%s: meta_back_init_one_conn[%d] failed err=%d text=%s\n",
				op->o_log_prefix, candidate, rs->sr_err, rs->sr_text );
		}

		rs->sr_err = slap_map_api2result( rs );
		if ( sendok & LDAP_BACK_SENDERR ) {
			send_ldap_result( op, rs );
		}
	}

	return rs->sr_err;
}

/*
 * meta_back_retry
 * 
 * Retries one connection
 */
int
meta_back_retry(
	Operation		*op,
	SlapReply		*rs,
	metaconn_t		**mcp,
	int			candidate,
	ldap_back_send_t	sendok )
{
	metainfo_t		*mi = ( metainfo_t * )op->o_bd->be_private;
	metatarget_t		*mt = mi->mi_targets[ candidate ];
	metaconn_t		*mc = *mcp;
	metasingleconn_t	*msc = &mc->mc_conns[ candidate ];
	int			rc = LDAP_UNAVAILABLE,
				binding,
				quarantine = 1;

	ldap_pvt_thread_mutex_lock( &mi->mi_conninfo.lai_mutex );

	assert( !META_BACK_CONN_CREATING( msc ) );
	binding = LDAP_BACK_CONN_BINDING( msc );
	LDAP_BACK_CONN_BINDING_CLEAR( msc );

	assert( mc->mc_refcnt > 0 );
	if ( mc->mc_refcnt == 1 ) {
		struct berval save_cred;

		if ( LogTest( LDAP_DEBUG_ANY ) ) {
			/* this lock is required; however,
			 * it's invoked only when logging is on */
			ldap_pvt_thread_mutex_lock( &mt->mt_uri_mutex );
			Debug(LDAP_DEBUG_ANY,
			      "%s meta_back_retry[%d]: retrying URI=\"%s\" DN=\"%s\".\n",
			      op->o_log_prefix, candidate, mt->mt_uri,
			      BER_BVISNULL(&msc->msc_bound_ndn) ? "" : msc->msc_bound_ndn.bv_val );
			ldap_pvt_thread_mutex_unlock( &mt->mt_uri_mutex );
		}

		/* save credentials, if any, for later use;
		 * meta_clear_one_candidate() would free them */
		save_cred = msc->msc_cred;
		BER_BVZERO( &msc->msc_cred );

		meta_clear_one_candidate( op, mc, candidate );
		LDAP_BACK_CONN_ISBOUND_CLEAR( msc );

		( void )rewrite_session_delete( mt->mt_rwmap.rwm_rw, op->o_conn );

		/* mc here must be the regular mc, reset and ready for init */
		rc = meta_back_init_one_conn( op, rs, mc, candidate,
			LDAP_BACK_CONN_ISPRIV( mc ), sendok, 0 );

		/* restore credentials, if any and if needed;
		 * meta_back_init_one_conn() restores msc_bound_ndn, if any;
		 * if no msc_bound_ndn is restored, destroy credentials */
		if ( !BER_BVISNULL( &msc->msc_bound_ndn )
			&& BER_BVISNULL( &msc->msc_cred ) )
		{
			msc->msc_cred = save_cred;

		} else if ( !BER_BVISNULL( &save_cred ) ) {
			memset( save_cred.bv_val, 0, save_cred.bv_len );
			ber_memfree_x( save_cred.bv_val, NULL );
		}

		/* restore the "binding" flag, in case */
		if ( binding ) {
			LDAP_BACK_CONN_BINDING_SET( msc );
		}

		if ( rc == LDAP_SUCCESS ) {
			quarantine = 0;
			LDAP_BACK_CONN_BINDING_SET( msc ); binding = 1;
			rc = meta_back_single_dobind( op, rs, mcp, candidate,
				sendok, mt->mt_nretries, 0 );

			Debug( LDAP_DEBUG_ANY,
				"%s meta_back_retry[%d]: "
				"meta_back_single_dobind=%d\n",
				op->o_log_prefix, candidate, rc );
			if ( rc == LDAP_SUCCESS ) {
				if ( !BER_BVISNULL( &msc->msc_bound_ndn ) &&
					!BER_BVISEMPTY( &msc->msc_bound_ndn ) )
				{
					LDAP_BACK_CONN_ISBOUND_SET( msc );

				} else {
					LDAP_BACK_CONN_ISANON_SET( msc );
				}

				/* when bound, dispose of the "binding" flag */
				if ( binding ) {
					LDAP_BACK_CONN_BINDING_CLEAR( msc );
				}
			}
		}

#if 0	/* ITS#7591, following stmt drops needed result msgs */
		/* don't send twice */
		sendok &= ~LDAP_BACK_SENDERR;
#endif
	}

	if ( rc != LDAP_SUCCESS ) {
		SlapReply		*candidates = meta_back_candidates_get( op );

		candidates[ candidate ].sr_err = rc;

		if ( *mcp != NULL ) {
			if ( mc->mc_refcnt == 1 ) {
				if ( binding ) {
					LDAP_BACK_CONN_BINDING_CLEAR( msc );
				}
				(void)meta_clear_one_candidate( op, mc, candidate );
			}

			LDAP_BACK_CONN_TAINTED_SET( mc );
			/* only release if mandatory; otherwise
			 * let the caller do what's best before
			 * releasing */
			if ( META_BACK_ONERR_STOP( mi ) ) {
				meta_back_release_conn_lock( mi, mc, 0 );
				*mcp = NULL;

			} else {
#if META_BACK_PRINT_CONNTREE > 0
				meta_back_print_conntree( mi, ">>> meta_back_retry" );
#endif /* META_BACK_PRINT_CONNTREE */

				/* FIXME: could be done better, reworking meta_back_release_conn_lock() */
				if ( LDAP_BACK_PCONN_ISPRIV( mc ) ) {
					if ( mc->mc_q.tqe_prev != NULL ) {
						assert( LDAP_BACK_CONN_CACHED( mc ) );
						assert( mi->mi_conn_priv[ LDAP_BACK_CONN2PRIV( mc ) ].mic_num > 0 );
						LDAP_TAILQ_REMOVE( &mi->mi_conn_priv[ LDAP_BACK_CONN2PRIV( mc ) ].mic_priv,
							mc, mc_q );
						mi->mi_conn_priv[ LDAP_BACK_CONN2PRIV( mc ) ].mic_num--;
						LDAP_TAILQ_ENTRY_INIT( mc, mc_q );

					} else {
						assert( !LDAP_BACK_CONN_CACHED( mc ) );
					}

				} else {
					/* FIXME: check if in tree, for consistency? */
					(void)ldap_tavl_delete( &mi->mi_conninfo.lai_tree,
						( caddr_t )mc, meta_back_conndnmc_cmp );
				}
				LDAP_BACK_CONN_CACHED_CLEAR( mc );

#if META_BACK_PRINT_CONNTREE > 0
				meta_back_print_conntree( mi, "<<< meta_back_retry" );
#endif /* META_BACK_PRINT_CONNTREE */
			}
		}

		if ( sendok & LDAP_BACK_SENDERR ) {
			rs->sr_err = rc;
			rs->sr_text = "Unable to retry";
			send_ldap_result( op, rs );
		}
	}

	if ( quarantine && META_BACK_TGT_QUARANTINE( mt ) ) {
		meta_back_quarantine( op, rs, candidate );
	}

	ldap_pvt_thread_mutex_unlock( &mi->mi_conninfo.lai_mutex );

	return rc == LDAP_SUCCESS ? 1 : 0;
}

/*
 * callback for unique candidate selection
 */
static int
meta_back_conn_cb( Operation *op, SlapReply *rs )
{
	assert( op->o_tag == LDAP_REQ_SEARCH );

	switch ( rs->sr_type ) {
	case REP_SEARCH:
		((long *)op->o_callback->sc_private)[0] = (long)op->o_private;
		break;

	case REP_SEARCHREF:
	case REP_RESULT:
		break;

	default:
		return rs->sr_err;
	}

	return 0;
}


static int
meta_back_get_candidate(
	Operation	*op,
	SlapReply	*rs,
	struct berval	*ndn )
{
	metainfo_t	*mi = ( metainfo_t * )op->o_bd->be_private;
	long		candidate;

	/*
	 * tries to get a unique candidate
	 * (takes care of default target)
	 */
	candidate = meta_back_select_unique_candidate( mi, ndn );

	/*
	 * if any is found, inits the connection
	 */
	if ( candidate == META_TARGET_NONE ) {
		rs->sr_err = LDAP_NO_SUCH_OBJECT;
		rs->sr_text = "No suitable candidate target found";

	} else if ( candidate == META_TARGET_MULTIPLE ) {
		Operation	op2 = *op;
		SlapReply	rs2 = { REP_RESULT };
		slap_callback	cb2 = { 0 };
		int		rc;

		/* try to get a unique match for the request ndn
		 * among the multiple candidates available */
		op2.o_tag = LDAP_REQ_SEARCH;
		op2.o_req_dn = *ndn;
		op2.o_req_ndn = *ndn;
		op2.ors_scope = LDAP_SCOPE_BASE;
		op2.ors_deref = LDAP_DEREF_NEVER;
		op2.ors_attrs = slap_anlist_no_attrs;
		op2.ors_attrsonly = 0;
		op2.ors_limit = NULL;
		op2.ors_slimit = 1;
		op2.ors_tlimit = SLAP_NO_LIMIT;

		op2.ors_filter = (Filter *)slap_filter_objectClass_pres;
		op2.ors_filterstr = *slap_filterstr_objectClass_pres;

		op2.o_callback = &cb2;
		cb2.sc_response = meta_back_conn_cb;
		cb2.sc_private = (void *)&candidate;

		rc = op->o_bd->be_search( &op2, &rs2 );

		switch ( rs2.sr_err ) {
		case LDAP_SUCCESS:
		default:
			rs->sr_err = rs2.sr_err;
			break;

		case LDAP_SIZELIMIT_EXCEEDED:
			/* if multiple candidates can serve the operation,
			 * and a default target is defined, and it is
			 * a candidate, try using it (FIXME: YMMV) */
			if ( mi->mi_defaulttarget != META_DEFAULT_TARGET_NONE
				&& meta_back_is_candidate( mi->mi_targets[ mi->mi_defaulttarget ],
						ndn, op->o_tag == LDAP_REQ_SEARCH ? op->ors_scope : LDAP_SCOPE_BASE ) )
			{
				candidate = mi->mi_defaulttarget;
				rs->sr_err = LDAP_SUCCESS;
				rs->sr_text = NULL;

			} else {
				rs->sr_err = LDAP_UNWILLING_TO_PERFORM;
				rs->sr_text = "Unable to select unique candidate target";
			}
			break;
		}

	} else {
		rs->sr_err = LDAP_SUCCESS;
	}

	return candidate;
}

static void	*meta_back_candidates_dummy;

static void
meta_back_candidates_keyfree(
	void		*key,
	void		*data )
{
	metacandidates_t	*mc = (metacandidates_t *)data;

	ber_memfree_x( mc->mc_candidates, NULL );
	ber_memfree_x( data, NULL );
}

SlapReply *
meta_back_candidates_get( Operation *op )
{
	metainfo_t		*mi = ( metainfo_t * )op->o_bd->be_private;
	metacandidates_t	*mc;

	if ( op->o_threadctx ) {
		void		*data = NULL;

		ldap_pvt_thread_pool_getkey( op->o_threadctx,
				&meta_back_candidates_dummy, &data, NULL );
		mc = (metacandidates_t *)data;

	} else {
		mc = mi->mi_candidates;
	}

	if ( mc == NULL ) {