Gentoo uses a default ulimit of 1024 open files. While this will have some benefits, it causes trouble in combination with some packages. While i.e. for named the number of open files can be adjusted by changing one config file entry (see comment 4 of http://bugs.gentoo.org/show_bug.cgi?id=296663) or for squid there is an entry in /etc/conf.d/squid, it is not possible to increase this limit for slapd, which causes many trouble if this vital service fails because this limit prevents it from opening further files. Trying to solve it via changing the limit in /etc/security/limits.conf fails, because the service is started via start-stop-daemon (you can't use -c ldap for it, because it uses privileged ports) and also seems to not read the limit-file by itself.
See the rc_ulimit parameters in /etc/rc.conf and add them to your /etc/conf.d/slapd as needed.
