dual IPv4/IPv6 stack support

Hey Folks, can anyone shed  some light on the current status and plans for dual IPv4/IPv6 support in Ceph? I know there were some work in that direction a while ago but IIUC it's never been completed. Any ideas why? Is there any work in progress? Is this still considered as doable? Do we still want it? Any estimates how hard it would be? Any comments are highly appreciated. Thanks, Igor