From the openldap-software mailing list:

Is it possible to set up OpenLDAP in a way: 1) a client connects to a slave, and wants to write something, 2) slave connects to the master, 3) slave writes the change on behalf of the client, and gets the changes back 4) client is notified, that the change was done Use OpenLDAP 2.3, and the set an instance of the “chain” overlay as global. Follow test007/test017 as guidelines; slapd- ldap(5) and slapo-chain(5) should be of help in configuring the required features of slapo-chain as appropriate.

I must test that. Just what the doctor called for.