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alias-base

The dereference of aliases is unfortunately not supported by the 389ds ldap server. Therefore here is a small plugin which resolves aliases during base search. Subtree and onelevel searches are not supported.

Compiling

yum install 389-ds-base-devel
make

Installing

cp libalias-base-plugin.so /usr/lib64/dirsrv/plugins
chown root:root /usr/lib64/dirsrv/plugins/libalias-base-plugin.so
chmod 755 /usr/lib64/dirsrv/plugins/libalias-base-plugin.so
ldapadd -H ldap://ldapserver -D "cn=Directory Manager" -W -f alias-base.ldif
systemctl restart dirsrv@ldapserver

Removing

ldapdelete -H ldap://ldapserver -D "cn=Directory Manager" -W "cn=alias-base,cn=plugins,cn=config"
systemctl restart dirsrv@ldapserver
rm /usr/lib64/dirsrv/plugins/libalias-base-plugin.so

Why

Consider you have the Oracle database MYDB, and you keep your tnsnames in the LDAP:

dn: cn=MYDB,cn=OracleContext,dc=world
objectClass: top
objectClass: orclNetService
cn: MYDB
orclNetDescString: (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=DBHOST)(PORT=1521))(CONNECT_DATA=(SERVICE_NAME=MYDB)))

Now you have migrated the data from the other db MYOLDDB into this MYDB. On the clients side the tnsname MYOLDDB is still configured. To enable clients to connect to the new DB without changing their settings, you can create an alias like this:

dn: cn=MYOLDDB,cn=OracleContext,dc=world
objectClass: top
objectClass: alias
objectClass: orclNetServiceAlias
cn: MYOLDDB
aliasedObjectName: cn=MYDB,cn=OracleContext,dc=world

Example

Here is what happening with and without plugin:

without pluginwith plugin

$ ldapsearch -a find -s base -x -LLL -H ldap://ldapserver -b "cn=MYDB,cn=OracleContext,dc=world" orclNetDescString

dn: cn=MYDB,cn=OracleContext,dc=world
orclNetDescString: (DESCRIPTION=...

dn: cn=MYDB,cn=OracleContext,dc=world
orclNetDescString: (DESCRIPTION=...

ldapsearch -a find -s base -x -LLL -H ldap://ldapserver -b "cn=MYOLDDB,cn=OracleContext,dc=world" orclNetDescString

dn: cn=MYOLDDB,cn=OracleContext,dc=world

⚠️ orclNetDescString not returned

 
dn: cn=MYDB,cn=OracleContext,dc=world
orclNetDescString: (DESCRIPTION=...

✅ orclNetDescString is here and dn is MYDB

tnsping MYDB

Used parameter files:
c:\...\OraCli193_64\network\admin\sqlnet.ora

Used LDAP adapter to resolve the alias
Attempting to contact (DESCRIPTION=...
OK (20 msec)

Used parameter files:
c:\...\OraCli193_64\network\admin\sqlnet.ora

Used LDAP adapter to resolve the alias
Attempting to contact (DESCRIPTION=...
OK (20 msec)

tnsping MYOLDDB

Used parameter files:
c:\...\OraCli193_64\network\admin\sqlnet.ora

TNS-03505: Failed to resolve name

⚠️ The client throws TNS-03505

 
Used parameter files:
c:\...\OraCli193_64\network\admin\sqlnet.ora

Used LDAP adapter to resolve the alias
Attempting to contact (DESCRIPTION=...
OK (20 msec)

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