install address selection policy into kernel when there is

/etc/ip6addrctl.conf.
following sample of ip6addrctl.conf is a good default:

#Prefix       Precedence Label
::1/128               50     0
::/0                  40     1
2002::/16             30     2
::/96                 20     3
::ffff:0:0/96         10     4

etc/rc.d/Makefile

@@ -15,7 +15,7 @@ FILES=	DAEMON LOGIN NETWORKING SERVERS \
 	gbde \
 	hostname \
 	inetd initdiskless initrandom \
-	ip6fw ipfilter ipfs ipfw ipmon \
+	ip6addrctl ip6fw ipfilter ipfs ipfw ipmon \
 	ipnat ipsec ipxrouted isdnd \
 	jail \
 	kadmind kerberos keyserv kldxref kpasswdd \

etc/rc.d/ip6addrctl

@@ -0,0 +1,33 @@
+#!/bin/sh
+#
+# $FreeBSD$
+#
+
+# PROVIDE: ip6addrctl
+# REQUIRE: mountcritlocal netif
+# BEFORE: network_ipv6
+# KEYWORD: FreeBSD
+
+. /etc/rc.subr
+. /etc/network.subr
+
+name="ip6addrctl"
+start_cmd="ip6addrctl_start"
+stop_cmd=':'
+
+ip6addrctl_start()
+{
+	if ifconfig lo0 inet6 >/dev/null 2>&1; then
+		# We have IPv6 support in kernel.
+
+		# install the policy of the address selection algorithm.
+		if [ -f /etc/ip6addrctl.conf ]; then
+			ip6addrctl flush >/dev/null 2>&1
+			ip6addrctl install /etc/ip6addrctl.conf
+			ip6addrctl
+		fi
+	fi
+}
+
+load_rc_config $name
+run_rc_command "$1"