I just chatted with Martin Schwenke who implemented POSIX ACLs for FSAL_VFS. He pointed out that he implemented acl_{get,set}_fd_np for Linux, so it should be usable. I've never tried compiling though...
Really? Where is it?
We should be able to get it working though.
acl_set_fd_np() and acl_get_fd_np() are ten-liner library functions in FreeBSD's libc, but they rely on libc internals that may not have anything analogous in glibc. Need to look at glibc and/or linux's libacl