How to write an overlay that perform search from within an overlay?

[hptf <hptf@free.fr>]

Hello all,

I am trying to write an overlay that is able to get the previous/old values of
an Entity, before it is updated by a modify/delete.

For that purpose, my first tries were to use a search from within the overlay,
or pre-read.

I try many method, (inspired by existing overlay), but none seems to work for
now:
    - use of pre-read seems to be very complicated; moreover, pre-read ctrl
seems to be returned as already ber-encoded, meaning that I need to re-decode
the ber to get the value ... this is (too) expensive
   - use of search from within overlay raise, for now, some problems:
        * if using translucent like call to 'be_entry_get_rw' I got deadlock on
hdb
        * if using rc = nop->o_bd->be_search(nop,&nrs); from within overlay, it
seems that response is sent also to remote client socket, and not stay confined
to overlay call ( and, btw, I fail to get the result:
rs->sr_un.sru_search.r_entry is NULL )

I, for sure, miss something.
 Do you have any clue, example, advice that may help me to continue ?

Thanks in advance for your help.
hp tf

PS: This is a repost in the good mailing list, initial message post in openldap-devel@openldap.org, sorry for the inconvenience.