Fix several logic bugs in the previous IPv6 variable change and

re-add $ipv6_enable support for backward compatibility.  From
UPDATING:

 1. To use IPv6, simply define $ifconfig_IF_ipv6 like $ifconfig_IF
    for IPv4.  For aliases, $ifconfig_IF_aliasN should be used.
    Note that both variables need the "inet6" keyword at the head.

    Do not set $ipv6_network_interfaces manually if you do not
    understand what you are doing.  It is not needed in most cases.

    $ipv6_ifconfig_IF and $ipv6_ifconfig_IF_aliasN still work, but
    they are obsolete.

 2. $ipv6_enable is obsolete.  Use $ipv6_prefer and/or
    "inet6 accept_rtadv" keyword in ifconfig(8) instead.

    If you define $ipv6_enable=YES, it means $ipv6_prefer=YES and
    all configured interfaces have "inet6 accept_rtadv" in the
    $ifconfig_IF_ipv6.  These are for backward compatibility.

 3. A new variable $ipv6_prefer has been added.  If NO, IPv6
    functionality of interfaces with no corresponding
    $ifconfig_IF_ipv6 is disabled by using "inet6 ifdisabled" flag,
    and the default address selection policy of ip6addrctl(8)
    is the IPv4-preferred one (see rc.d/ip6addrctl for more details).
    Note that if you want to configure IPv6 functionality on the
    disabled interfaces after boot, first you need to clear the flag by
    using ifconfig(8) like:

         ifconfig em0 inet6 -ifdisabled

    If YES, the default address selection policy is set as
    IPv6-preferred.

    The default value of $ipv6_prefer is NO.

 4. If your system need to receive Router Advertisement messages,
    define "inet6 accept_rtadv" in $ifconfig_IF_ipv6.  The rc(8)
    scripts automatically invoke rtsol(8) when the interface becomes
    UP.  The Router Advertisement messages are used for SLAAC
    (State-Less Address AutoConfiguration).

1 files changed, 2 insertions, 0 deletions

diff --git a/etc/rc.d/ip6addrctl b/etc/rc.d/ip6addrctl
index 518ac25..66f1952 100755
--- a/etc/rc.d/ip6addrctl
+++ b/etc/rc.d/ip6addrctl
@@ -19,6 +19,8 @@ status_cmd="ip6addrctl"
 prefer_ipv6_cmd="ip6addrctl_prefer_ipv6"
 prefer_ipv4_cmd="ip6addrctl_prefer_ipv4"
 
+set_rcvar_obsolete ipv6_enable ipv6_prefer
+
 ip6addrctl_prefer_ipv6()
 {
 	ip6addrctl flush >/dev/null 2>&1