NAT64: OpenBSD 5.1 will translate between IPv6 and IPv4
The packet filter, pf, in the upcoming version of OpenBSD 5.1 will include support for the network address translation mechanism NAT64. The patches for NAT64 support were incorporated in October 2011, but the feature has now made it to the official list of what will be in May 2012's release of OpenBSD.
NAT64 translates data packets between the two version of the internet protocol, IPv6 and IPv4, and allows IPv6-only hosts to communicate with IPv4-only servers. The basic techniques of NAT64 are covered in RFC 6052 and RFC 6146. NAT64 is envisioned to work with DNS64 which would handle the translation of A records to AAAA records. The manual page for pf gives more information on the feature which is described in sections on af-to rules.