net.inet6.icmp6.nd6_useloopback - what is it supposed to do?

[Garrett Cooper]

Hi,
    I've been TAHI testing FreeBSD 7.x sources for the past couple
months and over the course of my testing via the TAHI IPv6 conformance
test, I changed the knob value from net.inet6.icmp6.nd6_useloopback=1
-> net.inet6.icmp6.nd6_useloopback=0 and ran into a slew of errors
with the addr.p2 phase-1 TAHI tests.
    I was wondering if someone could describe what the beforementioned
sysctl is supposed to do from a functional perspective, how it might
tie into other IPv6 RFCs (if applicable), and if disabled how it would
affect a system with IPv6 enabled.
Thanks,
-Garrett