For proper function, multicast(4) needs to be enabled. To do so, add the
following line to /etc/rc.conf.local:
    multicast_host=YES

To start avahi automatically, add the following to /etc/rc.local:
(after dbus-daemon but before Zeroconf-aware applications startup)

if [ -x ${PREFIX}/sbin/avahi-daemon ]; then
	echo -n ' avahi-daemon'; ${PREFIX}/sbin/avahi-daemon -D
fi
if [ -x ${PREFIX}/sbin/avahi-dnsconfd ]; then
	echo -n ' avahi-dnsconfd'; ${PREFIX}/sbin/avahi-dnsconfd -D
fi