extended attributes and lsextattr/extattr_list_file

[manu%netbsd.org@localhost (Emmanuel Dreyfus)]

Hello

I implemented extattr_list_file for UFS1. The thing works fine, but I
notice the data expected by lsextattr(8) is not in the same shape as
described in NetBSD documentation and in FUSE and Linux.

In FUSE and Linux, listing extended attributes returns a buffer with NUL
separated extended attribute names. NetBSD's extattr_list_file(2) says
we do that.

In NetBSD's lsextattr(8) the expected data is a buffer with NUL
separated extended attribute names, each with a one-byte string length
prepended. I made a kernel implementation that matches what lsextattr(8)
expects. My kernel implementation therefore works with existing
lsextattr(8) but it does not match extattr_list_file(2) man page.

Beside the need to update the documentation, here are two problems
1) having to convert FUSE LISTXATTR output to extattr_list_file(2)
format is a pain
2) we also provide a lsxattr(2) Linux-like system call, and this is just
a wrapper to extattr_list_file(2), without conversion. Therefore our
lsxattr(2) is broken. 

I therefore propose to modify lsextattr(8) so that it expects data that
match what extattr_list_file(2) is supposed to send in the
documentation, and rework my UFS1 extattr_list_file implementation to
behave just like advertised in the documentation.

That breaks backward compatibility with non UFS1 filesystems
implementing extattr_list_file, but as far as I know that does not
exists. That could also make more dificult the task of importing future
extended attribute code from FreeBSD.

Opinions?

-- 
Emmanuel Dreyfus
http://hcpnet.free.fr/pubz
manu%netbsd.org@localhost