userspace stateless NAT64

 TAYGA is an out-of-kernel stateless NAT64 implementation for Linux
 that uses the TUN driver to exchange IPv4 and IPv6 packets with
 the kernel. It is intended to provide production-quality NAT64
 service for networks where dedicated NAT64 hardware would be
 overkill. TAYGA needs no kernel patches or out-of-tree
 modules, and it is compatible with all 2.4 and 2.6 kernels.