EXTATTR_NAMESPACE_USER
,
EXTATTR_NAMESPACE_SYSTEM
.
The semantics of these attributes are intended to be as follows: user
attribute data is protected according the normal discretionary
and mandatory protections associated with the data in the file or
directory; system attribute data is protected such that appropriate
privilege is required to directly access or manipulate these attributes.
Reads of extended attribute data may return specific contiguous regions of the meta-data, in the style of VOP_READ(9), but writes will replace the entire current ``value'' associated with a given name. As there are a plethora of file systems with differing extended attributes, availability and functionality of these functions may be limited, and they should be used with awareness of the underlying semantics of the supporting file system. Authorization schemes for extended attribute data may also vary by file system, as well as maximum attribute size, and whether or not any or specific new attributes may be defined.
Extended attributes are named using a nul-terminated character string. Depending on underlying file system semantics, this name may or may not be case-sensitive. Appropriate vnode extended attribute calls are: VOP_GETEXTATTR(9), VOP_LISTEXTATTR(9), and VOP_SETEXTATTR(9).