Extended attribute interfaces

[Casey Schaufler]

Robert Watson wrote:

> Kernel EAs: Extended attributes intended for consumption and use by the
> kernel, to back file system services such as ACLs, et al, to.
> 
> System EAs: Extended attributes that may be consumed by userland or
> kernel, but require privilege to do so from userland (CAP_EXT_ATTR or the
> like).
> 
> Application EAs: Extended attributes intended for consumption by userland
> applications, subject to the mandatory and discretionary protection
> provided to the normal file data.

I still want the fourth kind, which only the owner can set.
Think in terms of an icon or a README.


> I still find myself uncomfortable with the prefixing of funky characters
> to the front of the attribute name hower.  At some point, I'd just prefer
> to have different API calls, in that case:
> 
>   extattr_system_get_file()
>   extattr_application_get_file()
> 
>   extattr_get(EA_SYSTEM, )
>   extattr_get(EA_APPLICATION, )

If you keep the differentiator in the attribute name
you can add attribute types to the kernel without changing
the API. Example, if someone wanted to add an attribute
type which could only be modified by your boss ("*attributes",
where the * is pronounced asshole (Joke!)) you could do so
without adding an extattr_asshole_get_file() interface.

-- 

Casey Schaufler				Manager, Trust Technology, SGI
casey at sgi.com				voice: 650.933.1634
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