Displaying streams as xattrs

Jeremy Allison jra at samba.org
Thu May 25 20:22:02 UTC 2023

On Thu, May 25, 2023 at 03:11:13PM -0500, Steve French wrote:
>On Thu, May 25, 2023 at 11:22 AM Jeremy Allison <jra at samba.org> wrote:
>> On Thu, May 25, 2023 at 08:49:47PM +1000, ronnie sahlberg wrote:
>> >>
>> >> just took a look at how the ntfs-3g module is handling this. It was an option
>> >> streams_interface=value, which allows "windows", which means that the
>> >> alternative data streams are accessable as-is like in Windows, with ":" being
>> >> the separator. This might be a nice option for cifsfs also. That option would
>> >> just be usable if no posix extensions are enabled of course.
>You can already open alternate data streams remotely (from cifs.ko on Linux
>as you can from Windows and Macs etc. just open "file:streamname"), but on
>Linux you have to disable the reserved character mapping ("nomapposix")
>otherwise ":" would get remapped on open in the Unicode conversion.
>There may be a better way to list streams in the future (e.g. to help
>backup applications
>that need to be able to save files created by Macs or Windows that need these
>e.g. Virus checkers etc. use ADS, and looking at my Windows machines, PDFs
>can have small "Zone Identifiers" saved in streams), but you can
>already list them
>with "smbinfo filestreaminfo <filename>"
>I was thinking mainly about backup scenarios whether this came up as
>listing them
>also via a pseudo-xattr (IIRC Macs do something similar).

I think cifsfs providing access to ADS remotely on Windows
and Samba shares is fine.

What I'm scared of is adding ADS as a generic "feature" to
the Linux VFS and other filesystems :-).

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