DIVERT and SOCKET are not usable for TPROXY4 stuff in Squid due to what bug https://bugzilla.redhat.com/show_bug.cgi?id=662399 calls a user space problem.
libvirtd VMs cannot have outside accessible IPv6 addresses autoconfigured. I mentioned the problem, at least as far as I was able to find it at https://bugzilla.redhat.com/show_bug.cgi?id=514749
I would be doing more IPv6 testing but none of the F15 isos from fedoraproject.org will boot. They all crash on boot.
Trever