While setting up and testing new 2.4 infra (2.4.33), I've come across
the situation where the proxy (slapd-ldap) doesn't pass LDAP_UNAVAILABLE
back to the client when the backend slapd goes away. Is this behavior
configurable on the proxy, something along the lines of
chain-return-error?
It is not configurable, AFAIR. It's by design, as the proxy struggles to
return as much information as possible while hiding problems at the remote
host side. However I understand in some cases it might be preferable to
behave differently; something along the lines of the "onerr" directive for
slapd-meta(5). I suggest you file an ITS <http://www.openldap.org/its>.