First of all, znode_phys_t hasn't been used for storing file attributes for
a long time now. Modern ZFS versions use a System Attribute table with a
flexible layout. But more importantly all the required information is
available in znode_t itself.
It's not easy to include zfs_znode.h in userland without breaking code
because the most interesting parts of the header are kernel-only. And
hardcoding field offsets is too fragile. So, I created a new compilation
unit that includes zfs_znode.h using some mild kludges to get it and its
dependencies to compile in userland. The compilation unit exports
interesting field offsets and does not have any other code.