What does ip6addrctl do

[Ernie Luzar]

In /etc/defaults/rc.conf I see this

ip6addrctl_enable="YES" # Set to YES to enable default address selection
ip6addrctl_verbose="NO" # Set to YES to enable verbose configuration 
messages
ip6addrctl_policy="AUTO"        # A pre-defined address selection policy
                                 # (ipv4_prefer, ipv6_prefer, or AUTO)


There is no documentation included in the base release about this. Is it 
still available?  If so where to look to find out what it does?