I tried with ltb's latest Jessie builds but same problem occurs. I fast-checked tls_o.c, i can't find any code relative to handshake timeout (https://www.openldap.org/devel/gitweb.cgi?p=openldap.git;a=blob;f=libraries/...), but as i never handle any ssl lib code, i can be completely mistaken.

On Jessie, default timeout on gnuTLS seems to be 3600 secs, I will try to wait.

/usr/local/openldap/libexec/slapd -V @(#) $OpenLDAP: slapd 2.4.44 (Feb 8 2016 17:34:53) $ root@debian8:/opt/paquet-openldap-debian/openldap-ltb-2.4.44/servers/slapd