Yeah I agree this does seem like something that really ought to simply be configurable out of the box with options for transparently handling both 6-to-4 and 4-

Yeah I agree this does seem like something that really ought to simply be configurable out of the box with options for transparently handling both 6-to-4 and 4-to-6 when the appropriate services are discoverable or configured on the network. The top level reply here discussing how MacOS handles it seems like something that should be able to be recreated with iptables, but when searching I am extremely surprised to discover that Linux does not seem to have the ability to do anything similar. It seems most solutions focus on using socat in userspace to proxy data between the sockets which is not really a practical solution.