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conn.c

/* $OpenLDAP: pkg/ldap/servers/slapd/back-meta/conn.c,v 1.86.2.15 2008/04/14 21:19:57 quanah Exp $ */
/* This work is part of OpenLDAP Software <http://www.openldap.org/>.
 *
 * Copyright 1999-2008 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( Avlnode *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;
#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 = 1;

            if ( mt->mt_quarantine.ri_interval ) {
                  ldap_pvt_thread_mutex_lock( &mt->mt_quarantine_mutex );
                  if ( mt->mt_isquarantined == LDAP_BACK_FQ_YES ) {
                        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 ) {
                              if ( LogTest( LDAP_DEBUG_ANY ) ) {
                                    char  buf[ SLAP_TEXT_BUFLEN ];

                                    snprintf( buf, sizeof( buf ),
                                          "meta_back_init_one_conn[%d]: quarantine "
                                          "retry block #%d try #%d",
                                          candidate, ri->ri_idx, ri->ri_count );
                                    Debug( LDAP_DEBUG_ANY, "%s %s.\n",
                                          op->o_log_prefix, buf, 0 );
                              }
                        }

                        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,
            LDAP_BACK_CHASE_REFERRALS( mi ) ? LDAP_OPT_ON : LDAP_OPT_OFF );

#ifdef HAVE_TLS
      /* start TLS ("tls [try-]{start|propagate}" statement) */
      if ( ( LDAP_BACK_USE_TLS( mi )
            || ( op->o_conn->c_is_tls
                  && LDAP_BACK_PROPAGATE_TLS( mi ) ) )
            && !is_ldaps )
      {
#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_OTHER;
                        break;

                  case 0:
                        if ( nretries != 0 ) {
                              if ( nretries > 0 ) {
                                    nretries--;
                              }
                              LDAP_BACK_TV_SET( &tv );
                              goto retry;
                        }
                        rs->sr_err = LDAP_OTHER;
                        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;
                              }
                              
                              /* FIXME: in case a referral 
                               * is returned, should we try
                               * using it instead of the 
                               * configured URI? */
                              if ( rs->sr_err == LDAP_SUCCESS ) {
                                    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;
                  }

                  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
                        && LDAP_BACK_TLS_CRITICAL( mi ) ) )
            {

#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 );
                  }

            } 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 ) {
            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 ) {
            if ( LogTest( LDAP_DEBUG_ANY ) ) {
                  char  buf[ SLAP_TEXT_BUFLEN ];

                  /* this lock is required; however,
                   * it's invoked only when logging is on */
                  ldap_pvt_thread_mutex_lock( &mt->mt_uri_mutex );
                  snprintf( buf, sizeof( buf ),
                        "retrying URI=\"%s\" DN=\"%s\"",
                        mt->mt_uri,
                        BER_BVISNULL( &msc->msc_bound_ndn ) ?
                              "" : msc->msc_bound_ndn.bv_val );
                  ldap_pvt_thread_mutex_unlock( &mt->mt_uri_mutex );

                  Debug( LDAP_DEBUG_ANY,
                        "%s meta_back_retry[%d]: %s.\n",
                        op->o_log_prefix, candidate, buf );
            }

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

            if ( rc == LDAP_SUCCESS ) {
                  quarantine = 0;
                  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 );
                        }
                  }
            }

            /* don't send twice */
            sendok &= ~LDAP_BACK_SENDERR;
      }

      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)avl_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 = { 0 };
            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 ) {
            mc = ch_calloc( sizeof( metacandidates_t ), 1 );
            mc->mc_ntargets = mi->mi_ntargets;
            mc->mc_candidates = ch_calloc( sizeof( SlapReply ), mc->mc_ntargets );
            if ( op->o_threadctx ) {
                  void        *data = NULL;

                  data = (void *)mc;
                  ldap_pvt_thread_pool_setkey( op->o_threadctx,
                              &meta_back_candidates_dummy, data,
                              meta_back_candidates_keyfree,
                              NULL, NULL );

            } else {
                  mi->mi_candidates = mc;
            }

      } else if ( mc->mc_ntargets < mi->mi_ntargets ) {
            /* NOTE: in the future, may want to allow back-config
             * to add/remove targets from back-meta... */
            mc->mc_candidates = ch_realloc( mc->mc_candidates,
                        sizeof( SlapReply ) * mi->mi_ntargets );
            memset( &mc->mc_candidates[ mc->mc_ntargets ], 0,
                  sizeof( SlapReply ) * ( mi->mi_ntargets - mc->mc_ntargets ) );
            mc->mc_ntargets = mi->mi_ntargets;
      }

      return mc->mc_candidates;
}

/*
 * meta_back_getconn
 * 
 * Prepares the connection structure
 * 
 * RATIONALE:
 *
 * - determine what DN is being requested:
 *
 *    op    requires candidate      checks
 *
 *    add   unique                  parent of o_req_ndn
 *    bind  unique^*[/all]          o_req_ndn [no check]
 *    compare     unique^+          o_req_ndn
 *    delete      unique                  o_req_ndn
 *    modify      unique                  o_req_ndn
 *    search      any               o_req_ndn
 *    modrdn      unique[, unique]  o_req_ndn[, orr_nnewSup]
 *
 * - for ops that require the candidate to be unique, in case of multiple
 *   occurrences an internal search with sizeLimit=1 is performed
 *   if a unique candidate can actually be determined.  If none is found,
 *   the operation aborts; if multiple are found, the default target
 *   is used if defined and candidate; otherwise the operation aborts.
 *
 * *^note: actually, the bind operation is handled much like a search;
 *   i.e. the bind is broadcast to all candidate targets.
 *
 * +^note: actually, the compare operation is handled much like a search;
 *   i.e. the compare is broadcast to all candidate targets, while checking
 *   that exactly none (noSuchObject) or one (TRUE/FALSE/UNDEFINED) is
 *   returned.
 */
metaconn_t *
meta_back_getconn(
            Operation         *op,
      SlapReply         *rs,
      int               *candidate,
      ldap_back_send_t  sendok )
{
      metainfo_t  *mi = ( metainfo_t * )op->o_bd->be_private;
      metaconn_t  *mc = NULL,
                  mc_curr = { 0 };
      int         cached = META_TARGET_NONE,
                  i = META_TARGET_NONE,
                  err = LDAP_SUCCESS,
                  new_conn = 0,
                  ncandidates = 0;


      meta_op_type      op_type = META_OP_REQUIRE_SINGLE;
      enum        {
            META_DNTYPE_ENTRY,
            META_DNTYPE_PARENT,
            META_DNTYPE_NEWPARENT
      }           dn_type = META_DNTYPE_ENTRY;
      struct berval     ndn = op->o_req_ndn,
                  pndn;

      SlapReply   *candidates = meta_back_candidates_get( op );

      /* Internal searches are privileged and shared. So is root. */
      if ( ( !BER_BVISEMPTY( &op->o_ndn ) && META_BACK_PROXYAUTHZ_ALWAYS( mi ) )
            || ( BER_BVISEMPTY( &op->o_ndn ) && META_BACK_PROXYAUTHZ_ANON( mi ) )
            || op->o_do_not_cache || be_isroot( op ) )
      {
            LDAP_BACK_CONN_ISPRIV_SET( &mc_curr );
            mc_curr.mc_local_ndn = op->o_bd->be_rootndn;
            LDAP_BACK_PCONN_ROOTDN_SET( &mc_curr, op );

      } else if ( BER_BVISEMPTY( &op->o_ndn ) && META_BACK_PROXYAUTHZ_NOANON( mi ) )
      {
            LDAP_BACK_CONN_ISANON_SET( &mc_curr );
            BER_BVSTR( &mc_curr.mc_local_ndn, "" );
            LDAP_BACK_PCONN_ANON_SET( &mc_curr, op );

      } else {
            mc_curr.mc_local_ndn = op->o_ndn;

            /* Explicit binds must not be shared */
            if ( !BER_BVISEMPTY( &op->o_ndn )
                  || op->o_tag == LDAP_REQ_BIND
                  || SLAP_IS_AUTHZ_BACKEND( op ) )
            {
                  mc_curr.mc_conn = op->o_conn;
      
            } else {
                  LDAP_BACK_CONN_ISANON_SET( &mc_curr );
                  LDAP_BACK_PCONN_ANON_SET( &mc_curr, op );
            }
      }

      /* Explicit Bind requests always get their own conn */
      if ( sendok & LDAP_BACK_BINDING ) {
            mc_curr.mc_conn = op->o_conn;

      } else {
            /* Searches for a metaconn in the avl tree */
retry_lock:;
            ldap_pvt_thread_mutex_lock( &mi->mi_conninfo.lai_mutex );
            if ( LDAP_BACK_PCONN_ISPRIV( &mc_curr ) ) {
                  /* lookup a conn that's not binding */
                  LDAP_TAILQ_FOREACH( mc,
                        &mi->mi_conn_priv[ LDAP_BACK_CONN2PRIV( &mc_curr ) ].mic_priv,
                        mc_q )
                  {
                        if ( !LDAP_BACK_CONN_BINDING( mc ) && mc->mc_refcnt == 0 ) {
                              break;
                        }
                  }

                  if ( mc != NULL ) {
                        if ( mc != LDAP_TAILQ_LAST( &mi->mi_conn_priv[ LDAP_BACK_CONN2PRIV( mc ) ].mic_priv,
                              metaconn_t, mc_q ) )
                        {
                              LDAP_TAILQ_REMOVE( &mi->mi_conn_priv[ LDAP_BACK_CONN2PRIV( mc ) ].mic_priv,
                                    mc, mc_q );
                              LDAP_TAILQ_ENTRY_INIT( mc, mc_q );
                              LDAP_TAILQ_INSERT_TAIL( &mi->mi_conn_priv[ LDAP_BACK_CONN2PRIV( mc ) ].mic_priv,
                                    mc, mc_q );
                        }

                  } else if ( !LDAP_BACK_USE_TEMPORARIES( mi )
                        && mi->mi_conn_priv[ LDAP_BACK_CONN2PRIV( &mc_curr ) ].mic_num == mi->mi_conn_priv_max )
                  {
                        mc = LDAP_TAILQ_FIRST( &mi->mi_conn_priv[ LDAP_BACK_CONN2PRIV( &mc_curr ) ].mic_priv );
                  }
                  

            } else {
                  mc = (metaconn_t *)avl_find( mi->mi_conninfo.lai_tree, 
                        (caddr_t)&mc_curr, meta_back_conndn_cmp );
            }

            if ( mc ) {
                  /* catch taint errors */
                  assert( !LDAP_BACK_CONN_TAINTED( mc ) );

                  /* Don't reuse connections while they're still binding
                   * NOTE: only makes sense for binds */
                  if ( LDAP_BACK_CONN_BINDING( mc ) ) {
                        if ( !LDAP_BACK_USE_TEMPORARIES( mi ) ) {
                              ldap_pvt_thread_mutex_unlock( &mi->mi_conninfo.lai_mutex );

                              ldap_pvt_thread_yield();
                              goto retry_lock;
                        }

                        /* release conn, and create a temporary */
                        mc = NULL;

                  } else {
                        if ( ( mi->mi_conn_ttl != 0 && op->o_time > mc->mc_create_time + mi->mi_conn_ttl )
                              || ( mi->mi_idle_timeout != 0 && op->o_time > mc->mc_time + mi->mi_idle_timeout ) )
                        {
#if META_BACK_PRINT_CONNTREE > 0
                              meta_back_print_conntree( mi,
                                    ">>> meta_back_getconn(expired)" );
#endif /* META_BACK_PRINT_CONNTREE */

                              /* don't let anyone else use this expired connection */
                              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 {
                                    (void)avl_delete( &mi->mi_conninfo.lai_tree,
                                          (caddr_t)mc, meta_back_conndnmc_cmp );
                              }

#if META_BACK_PRINT_CONNTREE > 0
                              meta_back_print_conntree( mi,
                                    "<<< meta_back_getconn(expired)" );
#endif /* META_BACK_PRINT_CONNTREE */
                              LDAP_BACK_CONN_TAINTED_SET( mc );
                              LDAP_BACK_CONN_CACHED_CLEAR( mc );

                              Debug( LDAP_DEBUG_TRACE, "%s meta_back_getconn: mc=%p conn=%ld expired (tainted).\n",
                                    op->o_log_prefix, (void *)mc, LDAP_BACK_PCONN_ID( mc ) );
                        }

                        mc->mc_refcnt++;
                  }
            }
            ldap_pvt_thread_mutex_unlock( &mi->mi_conninfo.lai_mutex );
      }

      switch ( op->o_tag ) {
      case LDAP_REQ_ADD:
            /* if we go to selection, the entry must not exist,
             * and we must be able to resolve the parent */
            dn_type = META_DNTYPE_PARENT;
            dnParent( &ndn, &pndn );
            break;

      case LDAP_REQ_MODRDN:
            /* if nnewSuperior is not NULL, it must resolve
             * to the same candidate as the req_ndn */
            if ( op->orr_nnewSup ) {
                  dn_type = META_DNTYPE_NEWPARENT;
            }
            break;

      case LDAP_REQ_BIND:
            /* if bound as rootdn, the backend must bind to all targets
             * with the administrative identity
             * (unless pseoudoroot-bind-defer is TRUE) */
            if ( op->orb_method == LDAP_AUTH_SIMPLE && be_isroot_pw( op ) ) {
                  op_type = META_OP_REQUIRE_ALL;
            }
            break;

      case LDAP_REQ_COMPARE:
      case LDAP_REQ_DELETE:
      case LDAP_REQ_MODIFY:
            /* just a unique candidate */
            break;

      case LDAP_REQ_SEARCH:
            /* allow multiple candidates for the searchBase */
            op_type = META_OP_ALLOW_MULTIPLE;
            break;

      default:
            /* right now, just break (exop?) */
            break;
      }

      /*
       * require all connections ...
       */
      if ( op_type == META_OP_REQUIRE_ALL ) {

            /* Looks like we didn't get a bind. Open a new session... */
            if ( mc == NULL ) {
                  assert( new_conn == 0 );
                  mc = metaconn_alloc( op );
                  mc->mc_conn = mc_curr.mc_conn;
                  ber_dupbv( &mc->mc_local_ndn, &mc_curr.mc_local_ndn );
                  new_conn = 1;
                  if ( sendok & LDAP_BACK_BINDING ) {
                        LDAP_BACK_CONN_BINDING_SET( mc );
                  }
                  if ( LDAP_BACK_CONN_ISPRIV( &mc_curr ) ) {
                        LDAP_BACK_CONN_ISPRIV_SET( mc );

                  } else if ( LDAP_BACK_CONN_ISANON( &mc_curr ) ) {
                        LDAP_BACK_CONN_ISANON_SET( mc );
                  }

            } else if ( 0 ) {
                  /* TODO: if any of the connections is binding,
                   * release mc and create a new one */
            }

            for ( i = 0; i < mi->mi_ntargets; i++ ) {
                  /*
                   * The target is activated; if needed, it is
                   * also init'd
                   */
                  candidates[ i ].sr_err = meta_back_init_one_conn( op,
                        rs, mc, i, LDAP_BACK_CONN_ISPRIV( &mc_curr ),
                        LDAP_BACK_DONTSEND, !new_conn );
                  if ( candidates[ i ].sr_err == LDAP_SUCCESS ) {
                        if ( new_conn && ( sendok & LDAP_BACK_BINDING ) ) {
                              LDAP_BACK_CONN_BINDING_SET( &mc->mc_conns[ i ] );
                        }
                        META_CANDIDATE_SET( &candidates[ i ] );
                        ncandidates++;
      
                  } else {
                        
                        /*
                         * FIXME: in case one target cannot
                         * be init'd, should the other ones
                         * be tried?
                         */
                        META_CANDIDATE_RESET( &candidates[ i ] );
                        err = candidates[ i ].sr_err;
                        continue;
                  }
            }

            if ( ncandidates == 0 ) {
                  if ( new_conn ) {
                        mc->mc_refcnt = 0;
                        meta_back_conn_free( mc );

                  } else {
                        meta_back_release_conn( mi, mc );
                  }

                  rs->sr_err = LDAP_NO_SUCH_OBJECT;
                  rs->sr_text = "Unable to select valid candidates";

                  if ( sendok & LDAP_BACK_SENDERR ) {
                        if ( rs->sr_err == LDAP_NO_SUCH_OBJECT ) {
                              rs->sr_matched = op->o_bd->be_suffix[ 0 ].bv_val;
                        }
                        send_ldap_result( op, rs );
                        rs->sr_matched = NULL;
                  }

                  return NULL;
            }

            goto done;
      }
      
      /*
       * looks in cache, if any
       */
      if ( mi->mi_cache.ttl != META_DNCACHE_DISABLED ) {
            cached = i = meta_dncache_get_target( &mi->mi_cache, &op->o_req_ndn );
      }

      if ( op_type == META_OP_REQUIRE_SINGLE ) {
            metatarget_t            *mt = NULL;
            metasingleconn_t  *msc = NULL;

            int               j;

            for ( j = 0; j < mi->mi_ntargets; j++ ) {
                  META_CANDIDATE_RESET( &candidates[ j ] );
            }

            /*
             * tries to get a unique candidate
             * (takes care of default target)
             */
            if ( i == META_TARGET_NONE ) {
                  i = meta_back_get_candidate( op, rs, &ndn );

                  if ( rs->sr_err == LDAP_NO_SUCH_OBJECT && dn_type == META_DNTYPE_PARENT ) {
                        i = meta_back_get_candidate( op, rs, &pndn );
                  }
      
                  if ( i < 0 || rs->sr_err != LDAP_SUCCESS ) {
                        if ( mc != NULL ) {
                              meta_back_release_conn( mi, mc );
                        }

                        if ( sendok & LDAP_BACK_SENDERR ) {
                              if ( rs->sr_err == LDAP_NO_SUCH_OBJECT ) {
                                    rs->sr_matched = op->o_bd->be_suffix[ 0 ].bv_val;
                              }
                              send_ldap_result( op, rs );
                              rs->sr_matched = NULL;
                        }
                  
                        return NULL;
                  }
            }

            if ( dn_type == META_DNTYPE_NEWPARENT && meta_back_get_candidate( op, rs, op->orr_nnewSup ) != i )
            {
                  if ( mc != NULL ) {
                        meta_back_release_conn( mi, mc );
                  }

                  rs->sr_err = LDAP_UNWILLING_TO_PERFORM;
                  rs->sr_text = "Cross-target rename not supported";
                  if ( sendok & LDAP_BACK_SENDERR ) {
                        send_ldap_result( op, rs );
                  }

                  return NULL;
            }

            Debug( LDAP_DEBUG_TRACE,
      "==>meta_back_getconn: got target=%d for ndn=\"%s\" from cache\n",
                        i, op->o_req_ndn.bv_val, 0 );

            if ( mc == NULL ) {
                  /* Retries searching for a metaconn in the avl tree
                   * the reason is that the connection might have been
                   * created by meta_back_get_candidate() */
                  if ( !( sendok & LDAP_BACK_BINDING ) ) {
retry_lock2:;
                        ldap_pvt_thread_mutex_lock( &mi->mi_conninfo.lai_mutex );
                        mc = (metaconn_t *)avl_find( mi->mi_conninfo.lai_tree, 
                              (caddr_t)&mc_curr, meta_back_conndn_cmp );
                        if ( mc != NULL ) {
                              /* catch taint errors */
                              assert( !LDAP_BACK_CONN_TAINTED( mc ) );

                              /* Don't reuse connections while they're still binding */
                              if ( META_BACK_CONN_CREATING( &mc->mc_conns[ i ] )
                                    || LDAP_BACK_CONN_BINDING( &mc->mc_conns[ i ] ) )
                              {
                                    if ( !LDAP_BACK_USE_TEMPORARIES( mi ) ) {
                                          ldap_pvt_thread_mutex_unlock( &mi->mi_conninfo.lai_mutex );
                                          ldap_pvt_thread_yield();
                                          goto retry_lock2;
                                    }

                                    mc = NULL;

                              } else {
                                    mc->mc_refcnt++;
                              }
                        }
                        ldap_pvt_thread_mutex_unlock( &mi->mi_conninfo.lai_mutex );
                  }

                  /* Looks like we didn't get a bind. Open a new session... */
                  if ( mc == NULL ) {
                        assert( new_conn == 0 );
                        mc = metaconn_alloc( op );
                        mc->mc_conn = mc_curr.mc_conn;
                        ber_dupbv( &mc->mc_local_ndn, &mc_curr.mc_local_ndn );
                        new_conn = 1;
                        if ( sendok & LDAP_BACK_BINDING ) {
                              LDAP_BACK_CONN_BINDING_SET( mc );
                        }
                        if ( LDAP_BACK_CONN_ISPRIV( &mc_curr ) ) {
                              LDAP_BACK_CONN_ISPRIV_SET( mc );

                        } else if ( LDAP_BACK_CONN_ISANON( &mc_curr ) ) {
                              LDAP_BACK_CONN_ISANON_SET( mc );
                        }
                  }
            }

            /*
             * Clear all other candidates
             */
            ( void )meta_clear_unused_candidates( op, i );

            mt = mi->mi_targets[ i ];
            msc = &mc->mc_conns[ i ];

            /*
             * The target is activated; if needed, it is
             * also init'd. In case of error, meta_back_init_one_conn
             * sends the appropriate result.
             */
            err = meta_back_init_one_conn( op, rs, mc, i,
                  LDAP_BACK_CONN_ISPRIV( &mc_curr ), sendok, !new_conn );
            if ( err != LDAP_SUCCESS ) {
                  /*
                   * FIXME: in case one target cannot
                   * be init'd, should the other ones
                   * be tried?
                   */
                  META_CANDIDATE_RESET( &candidates[ i ] );
                  if ( new_conn ) {
                        mc->mc_refcnt = 0;
                        meta_back_conn_free( mc );

                  } else {
                        meta_back_release_conn( mi, mc );
                  }
                  return NULL;
            }

            if ( new_conn && ( sendok & LDAP_BACK_BINDING ) ) {
                  LDAP_BACK_CONN_BINDING_SET( &mc->mc_conns[ i ] );
            }

            candidates[ i ].sr_err = LDAP_SUCCESS;
            META_CANDIDATE_SET( &candidates[ i ] );
            ncandidates++;

            if ( candidate ) {
                  *candidate = i;
            }

      /*
       * if no unique candidate ...
       */
      } else {

            /* Looks like we didn't get a bind. Open a new session... */
            if ( mc == NULL ) {
                  assert( new_conn == 0 );
                  mc = metaconn_alloc( op );
                  mc->mc_conn = mc_curr.mc_conn;
                  ber_dupbv( &mc->mc_local_ndn, &mc_curr.mc_local_ndn );
                  new_conn = 1;
                  if ( LDAP_BACK_CONN_ISPRIV( &mc_curr ) ) {
                        LDAP_BACK_CONN_ISPRIV_SET( mc );

                  } else if ( LDAP_BACK_CONN_ISANON( &mc_curr ) ) {
                        LDAP_BACK_CONN_ISANON_SET( mc );
                  }
            }

            for ( i = 0; i < mi->mi_ntargets; i++ ) {
                  metatarget_t            *mt = mi->mi_targets[ i ];

                  META_CANDIDATE_RESET( &candidates[ i ] );

                  if ( i == cached 
                        || meta_back_is_candidate( mt, &op->o_req_ndn,
                              LDAP_SCOPE_SUBTREE ) )
                  {

                        /*
                         * The target is activated; if needed, it is
                         * also init'd
                         */
                        int lerr = meta_back_init_one_conn( op, rs, mc, i,
                              LDAP_BACK_CONN_ISPRIV( &mc_curr ),
                              LDAP_BACK_DONTSEND, !new_conn );
                        candidates[ i ].sr_err = lerr;
                        if ( lerr == LDAP_SUCCESS ) {
                              META_CANDIDATE_SET( &candidates[ i ] );
                              ncandidates++;

                              Debug( LDAP_DEBUG_TRACE, "%s: meta_back_getconn[%d]\n",
                                    op->o_log_prefix, i, 0 );

                        } else if ( lerr == LDAP_UNAVAILABLE && !META_BACK_ONERR_STOP( mi ) ) {
                              META_CANDIDATE_SET( &candidates[ i ] );

                              Debug( LDAP_DEBUG_TRACE, "%s: meta_back_getconn[%d] %s\n",
                                    op->o_log_prefix, i,
                                    mt->mt_isquarantined != LDAP_BACK_FQ_NO ? "quarantined" : "unavailable" );

                        } else {
                        
                              /*
                               * FIXME: in case one target cannot
                               * be init'd, should the other ones
                               * be tried?
                               */
                              if ( new_conn ) {
                                    ( void )meta_clear_one_candidate( op, mc, i );
                              }
                              /* leave the target candidate, but record the error for later use */
                              err = lerr;

                              if ( lerr == LDAP_UNAVAILABLE && mt->mt_isquarantined != LDAP_BACK_FQ_NO ) {
                                    Debug( LDAP_DEBUG_TRACE, "%s: meta_back_getconn[%d] quarantined err=%d\n",
                                          op->o_log_prefix, i, lerr );

                              } else {
                                    Debug( LDAP_DEBUG_ANY, "%s: meta_back_getconn[%d] failed err=%d\n",
                                          op->o_log_prefix, i, lerr );
                              }

                              if ( META_BACK_ONERR_STOP( mi ) ) {
                                    if ( sendok & LDAP_BACK_SENDERR ) {
                                          send_ldap_result( op, rs );
                                    }
                                    if ( new_conn ) {
                                          mc->mc_refcnt = 0;
                                          meta_back_conn_free( mc );

                                    } else {
                                          meta_back_release_conn( mi, mc );
                                    }

                                    return NULL;
                              }

                              continue;
                        }

                  } else {
                        if ( new_conn ) {
                              ( void )meta_clear_one_candidate( op, mc, i );
                        }
                  }
            }

            if ( ncandidates == 0 ) {
                  if ( new_conn ) {
                        mc->mc_refcnt = 0;
                        meta_back_conn_free( mc );

                  } else {
                        meta_back_release_conn( mi, mc );
                  }

                  if ( rs->sr_err == LDAP_SUCCESS ) {
                        rs->sr_err = LDAP_NO_SUCH_OBJECT;
                        rs->sr_text = "Unable to select valid candidates";
                  }

                  if ( sendok & LDAP_BACK_SENDERR ) {
                        if ( rs->sr_err == LDAP_NO_SUCH_OBJECT ) {
                              rs->sr_matched = op->o_bd->be_suffix[ 0 ].bv_val;
                        }
                        send_ldap_result( op, rs );
                        rs->sr_matched = NULL;
                  }

                  return NULL;
            }
      }

done:;
      /* clear out meta_back_init_one_conn non-fatal errors */
      rs->sr_err = LDAP_SUCCESS;
      rs->sr_text = NULL;

      /* touch the timestamp */
      if ( mi->mi_idle_timeout != 0 ) {
            mc->mc_time = op->o_time;
      }

      if ( new_conn ) {
            if ( mi->mi_conn_ttl ) {
                  mc->mc_create_time = op->o_time;
            }

            /*
             * Inserts the newly created metaconn in the avl tree
             */
            ldap_pvt_thread_mutex_lock( &mi->mi_conninfo.lai_mutex );
#if META_BACK_PRINT_CONNTREE > 0
            meta_back_print_conntree( mi, ">>> meta_back_getconn" );
#endif /* META_BACK_PRINT_CONNTREE */

            err = 0;
            if ( LDAP_BACK_PCONN_ISPRIV( mc ) ) {
                  if ( mi->mi_conn_priv[ LDAP_BACK_CONN2PRIV( mc ) ].mic_num < mi->mi_conn_priv_max ) {
                        LDAP_TAILQ_INSERT_TAIL( &mi->mi_conn_priv[ LDAP_BACK_CONN2PRIV( mc ) ].mic_priv, mc, mc_q );
                        mi->mi_conn_priv[ LDAP_BACK_CONN2PRIV( mc ) ].mic_num++;
                        LDAP_BACK_CONN_CACHED_SET( mc );

                  } else {
                        LDAP_BACK_CONN_TAINTED_SET( mc );
                  }
                  rs->sr_err = 0;

            } else if ( !( sendok & LDAP_BACK_BINDING ) ) {
                  err = avl_insert( &mi->mi_conninfo.lai_tree, ( caddr_t )mc,
                              meta_back_conndn_cmp, meta_back_conndn_dup );
                  LDAP_BACK_CONN_CACHED_SET( mc );
            }

#if META_BACK_PRINT_CONNTREE > 0
            meta_back_print_conntree( mi, "<<< meta_back_getconn" );
#endif /* META_BACK_PRINT_CONNTREE */
            ldap_pvt_thread_mutex_unlock( &mi->mi_conninfo.lai_mutex );

            if ( !LDAP_BACK_PCONN_ISPRIV( mc ) ) {
                  /*
                   * Err could be -1 in case a duplicate metaconn is inserted
                   */
                  switch ( err ) {
                  case 0:
                        break;

                  case -1:
                        LDAP_BACK_CONN_CACHED_CLEAR( mc );
                        /* duplicate: free and try to get the newly created one */
                        if ( !( sendok & LDAP_BACK_BINDING ) && !LDAP_BACK_USE_TEMPORARIES( mi ) ) {
                              mc->mc_refcnt = 0;      
                              meta_back_conn_free( mc );
      
                              new_conn = 0;
                              goto retry_lock;
                        }

                        LDAP_BACK_CONN_TAINTED_SET( mc );
                        break;

                  default:
                        LDAP_BACK_CONN_CACHED_CLEAR( mc );
                        Debug( LDAP_DEBUG_ANY,
                              "%s meta_back_getconn: candidates=%d conn=%ld insert failed\n",
                              op->o_log_prefix, ncandidates,
                              LDAP_BACK_PCONN_ID( mc ) );
      
                        mc->mc_refcnt = 0;      
                        meta_back_conn_free( mc );

                        rs->sr_err = LDAP_OTHER;
                        rs->sr_text = "Proxy bind collision";
                        if ( sendok & LDAP_BACK_SENDERR ) {
                              send_ldap_result( op, rs );
                        }
                        return NULL;
                  }
            }

            Debug( LDAP_DEBUG_TRACE,
                  "%s meta_back_getconn: candidates=%d conn=%ld inserted\n",
                  op->o_log_prefix, ncandidates,
                  LDAP_BACK_PCONN_ID( mc ) );

      } else {
            Debug( LDAP_DEBUG_TRACE,
                  "%s meta_back_getconn: candidates=%d conn=%ld fetched\n",
                  op->o_log_prefix, ncandidates,
                  LDAP_BACK_PCONN_ID( mc ) );
      }

      return mc;
}

void
meta_back_release_conn_lock(
            metainfo_t        *mi,
      metaconn_t        *mc,
      int               dolock )
{
      assert( mc != NULL );

      if ( dolock ) {
            ldap_pvt_thread_mutex_lock( &mi->mi_conninfo.lai_mutex );
      }
      assert( mc->mc_refcnt > 0 );
      mc->mc_refcnt--;
      /* NOTE: the connection is removed if either it is tainted
       * or if it is shared and no one else is using it.  This needs
       * to occur because for intrinsic reasons cached connections
       * that are not privileged would live forever and pollute
       * the connection space (and eat up resources).  Maybe this
       * should be configurable... */
      if ( LDAP_BACK_CONN_TAINTED( mc ) || !LDAP_BACK_CONN_CACHED( mc ) ) {
#if META_BACK_PRINT_CONNTREE > 0
            meta_back_print_conntree( mi, ">>> meta_back_release_conn" );
#endif /* META_BACK_PRINT_CONNTREE */

            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 if ( LDAP_BACK_CONN_CACHED( mc ) ) {
                  metaconn_t  *tmpmc;

                  tmpmc = avl_delete( &mi->mi_conninfo.lai_tree,
                        ( caddr_t )mc, meta_back_conndnmc_cmp );

                  /* Overparanoid, but useful... */
                  assert( tmpmc == NULL || tmpmc == mc );
            }

            LDAP_BACK_CONN_CACHED_CLEAR( mc );

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

            if ( mc->mc_refcnt == 0 ) {
                  meta_back_conn_free( mc );
                  mc = NULL;
            }
      }

      if ( mc != NULL && LDAP_BACK_CONN_BINDING( mc ) ) {
            LDAP_BACK_CONN_BINDING_CLEAR( mc );
      }

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

void
meta_back_quarantine(
      Operation   *op,
      SlapReply   *rs,
      int         candidate )
{
      metainfo_t        *mi = (metainfo_t *)op->o_bd->be_private;
      metatarget_t            *mt = mi->mi_targets[ candidate ];

      slap_retry_info_t *ri = &mt->mt_quarantine;

      ldap_pvt_thread_mutex_lock( &mt->mt_quarantine_mutex );

      if ( rs->sr_err == LDAP_UNAVAILABLE ) {
            time_t      new_last = slap_get_time();

            switch ( mt->mt_isquarantined ) {
            case LDAP_BACK_FQ_NO:
                  if ( ri->ri_last == new_last ) {
                        goto done;
                  }

                  Debug( LDAP_DEBUG_ANY,
                        "%s meta_back_quarantine[%d]: enter.\n",
                        op->o_log_prefix, candidate, 0 );

                  ri->ri_idx = 0;
                  ri->ri_count = 0;
                  break;

            case LDAP_BACK_FQ_RETRYING:
                  if ( LogTest( LDAP_DEBUG_ANY ) ) {
                        char  buf[ SLAP_TEXT_BUFLEN ];

                        snprintf( buf, sizeof( buf ),
                              "meta_back_quarantine[%d]: block #%d try #%d failed",
                              candidate, ri->ri_idx, ri->ri_count );
                        Debug( LDAP_DEBUG_ANY, "%s %s.\n",
                              op->o_log_prefix, buf, 0 );
                  }

                  ++ri->ri_count;
                  if ( ri->ri_num[ ri->ri_idx ] != SLAP_RETRYNUM_FOREVER
                        && ri->ri_count == ri->ri_num[ ri->ri_idx ] )
                  {
                        ri->ri_count = 0;
                        ++ri->ri_idx;
                  }
                  break;

            default:
                  break;
            }

            mt->mt_isquarantined = LDAP_BACK_FQ_YES;
            ri->ri_last = new_last;

      } else if ( mt->mt_isquarantined == LDAP_BACK_FQ_RETRYING ) {
            Debug( LDAP_DEBUG_ANY,
                  "%s meta_back_quarantine[%d]: exit.\n",
                  op->o_log_prefix, candidate, 0 );

            if ( mi->mi_quarantine_f ) {
                  (void)mi->mi_quarantine_f( mi, candidate,
                        mi->mi_quarantine_p );
            }

            ri->ri_count = 0;
            ri->ri_idx = 0;
            mt->mt_isquarantined = LDAP_BACK_FQ_NO;
      }

done:;
      ldap_pvt_thread_mutex_unlock( &mt->mt_quarantine_mutex );
}


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