Linux CIFS is IPv6 Enabled
At the SambaXP 2007 conference Steve French and David Holder IPv6 enabled the Linux CIFS client. At the SambaXP party on the Tuesday evening they successfully connected the Linux CIFS client to Windows Server Longhorn over IPv6 for the first time.
David Holder will be publishing instructions for testing the Linux CIFS client over IPv6. Steve has already posted an IPv6 enabled version. See http://lists.samba.org/archive/linux-cifs-client/2007-April/001924.html.