I have a question about a special LDAP setup , I try to use sock backend for bind user that after succesfull bind have to search on another backend, 

Here my slapd.conf on openldap 2.4.11

access to * by users read

##################BACKEND SOCK#################################################
database                sock
suffix                  "dc=reg-bus-users-local,dc=it"
#catturo le richieste riscritte da rwm bloccando richieste di lettura e scrittura dirette

socketpath              /tmp/ldapauthorization.sock

#######################################################################
# ldbm and/or bdb database definitions
#######################################################################

database        bdb
suffix          "dc=tfk,dc=tfkdatastore"
rootdn          "cn=Root,dc=tfk,dc=tfkdatastore"
rootpw          xxxxx

I also made a fake bind in server listening on socket ldapauthorization.sock

if ($request eq "BIND\n") {
      my %req = ();

      print "RESULT\n";
      print "code: 0\n";
      print "matched: cn=fratbrother,dc=reg-bus-users-local,dc=it\n";

}

my ldapsearch is : 
ldapsearch -H ldap://localhost:389/ -D "cn=fratbrother,dc=reg-bus-users-local,dc=it" -w xxxx  -x -b "dc=tfk,dc=tfkdatastore" "(objectClass=*)"  "*"

result : 

ldap_bind: Insufficient access (50)

my goal if work , is to make bind = (bind + search attribute) in other ldap server  check the validity of attribute and then response bind succesfull,
so redirected bind with check on remote attribute , is possible to do that ? is the right usage of backend sock ?

Ps : also noted that ldap does not connect to socket but make response directly "insufficient access".
Ps : sorry for the bad english

Thanks in Advance
Stefano Vitali