Kurt Zeilenga authored Jun 19, 2017 and Quanah Gibson-Mount committed Mar 26, 2020

The spec says that upon StartTLS 'success', both TLS communications is
established on the octet following the Start TLS response (and the
request)... and that once one starts TLS communications, one can never
go back to LDAP without TLS. So if there's a TLS failure (whether as
part of TLS nego or later), LDAP communications cannot be continued
(without TLS).

Only ignoring LDAP errors (rc > 0) ensures that if TLS negotiation
fails, we don't attempt to send LDAP operations without TLS.