[6bone] freebsd src addr wrong

[David Waitzman]

I have a 6bone tunnel connection with a non-routed tunnel endpoint 2001:: 
address.  I also have an official 6bone 3ffe:: address, which is assigned 
to one of my ether interfaces.

When I "ping6 www.kame.net" I see that my side of the tunnel is used as a 
source address.  I don't get ping responses back (presumably because 
www.kame.net does not know where to send responses, given that the address 
it is getting is not routed).

If I do a ping6 -S, selecting my 6bone 3ffe:: address as the source, then 
ping6 gets responses from kame just fine.

I am using FreeBSD 4.6.
We run Zebra-based BGP+ with our tunnel provider and thus have no default 
route.

My questions:
1. Should tunnel endpoint addresses be routable?
2. Or how do I force FreeBSD to use the ether's IPv6 address as a source by 
default?  (Not all applications have the equivalent of Ping6's -S option to 
force the source address selection.)

-david waitzman