Handling the 7 reserved characters when mounted to Mac

[Steve French]

One minor clarification

On Mac files can be created with the 7 reserved characters (but they
get remapped automatically on the wire).  On Windows you would have to
have SFU (services for unix), or SUA or equivalent in order to create
such files (and those characters get remapped when stored), and of
course CIFS/SMB2/SMB3 treats them as reserved as well (thus the need
to remap them).

On Wed, Sep 17, 2014 at 8:03 PM, Steve French <smfrench at gmail.com> wrote:
> There are seven reserved characters that need to be remapped when
> mounting to Windows, Mac (or any server without Unix Extensions) which
> are valid in POSIX but not in the other OS.
>
> : \ < > ? * |
>
> We use the normal UCS-2 remap range for this in order to convert this
> to/from UTF8 as did Windows Services for Unix (basically add 0xF000 to
> any of the 7 reserved characters).
>
> Mac used a very slightly different "Services for Mac" remap range
> 0xF021 through 0xF027.  The attached patch allows cifs.ko (the kernel
> client) to read directories on macs containing files with these
> characters and display their names properly.  In theory this even
> might be useful on mounts to Samba when the vfs_catia module is loaded
> and we are mounted with smb3.
>
> Currently the 7 reserved characters look very strange in directory
> listings from cifs.ko to Mac server.  This patch allows these file
> name characters to be read (requires specifying mapchars on mount).
>
> Two additional changes are needed:
> 1) Make it more automatic: a way of detecting that we are mounted to a
> Mac so we know to try to always remap these characters (at least for
> smb2.1 mounts to them and eventually smb3 when they support that)
>
> 2) A deterministic way of deciding when to use the normal mapchars
> approach vs. the mac mappings when creating a file with any of the
> seven characters in its name.  It may be ok in some cases to be able
> to translate file names in both formats properly when listing
> directories - but when creating files we have to use the same
> mechanism and decide when to use which, especially on SMB3 mounts
> (which do not have an option for posix pathnames).  Will need to
> decouple turning mac character mapping on/off from mapchars mount
> option.
>
> --
> Thanks,
>
> Steve



-- 
Thanks,

Steve
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