[Samba] Fruit & uchg

[Perttu Aaltonen]

> On 28. Apr 2021, at 13.34, Andrew Walker <walker.aj325 at gmail.com> wrote:
> 
> 
> 
> On Wed, Apr 28, 2021 at 5:23 AM Perttu Aaltonen <perttu.aaltonen at mac.com <mailto:perttu.aaltonen at mac.com>> wrote:
> 
>> On 27. Apr 2021, at 21.59, Andrew Walker <walker.aj325 at gmail.com <mailto:walker.aj325 at gmail.com>> wrote:
>> 
>> 
>> 
>> On Tue, Apr 27, 2021 at 8:19 AM Perttu Aaltonen via samba <samba at lists.samba.org <mailto:samba at lists.samba.org>> wrote:
>> Hello Ralph & others knowledgeable in vfs_fruit and Netatalk.
>> 
>> How does Samba and Netatalk store the “uchg” user immutable file flag set in macOS? Is it stored in an extended attribute? The behaviour I’m seeing is that setting this flag from either AFP or SMB side isn’t reflected on the other side. Is there a way to change this behaviour?
>> 
>> Thanks,
>> Perttu
>> -- 
>> To unsubscribe from this list go to the following URL and read the
>> instructions:  https://lists.samba.org/mailman/options/samba <https://lists.samba.org/mailman/options/samba>
>> 
>> Ralph can correct me if I'm wrong, but I believe the MacOS SMB client converts schg to the DOS readonly attribute. How this is applied to the samba server depends on samba's configuration. The default is to write it inside the user.DOSATTRIB xattr for the file. In the case of FreeNAS we convert DOS readonly to FreeBSD's urdonly file flag. In this case readonly is enforced by kernel / filesystem, but behavior differs from schg.  I presume when you write to do the same to a MacOS SMB server it sets uchg on the other side?
> 
> Hi Andrew. I can see user.DOSATTRIB on the server (Ubuntu + Samba + ZFS), but its content doesn’t change when I set uchg flag from the Mac client side and look at it with the getfattr command. So I’m not sure exactly how the server stores it. In any case it isn’t compatible with Netatalk since the flags don’t carry over, although I should have all the correct vfs_fruit settings for Netatalk compatibility.
> 
> -Perttu 
> 
> ZoL doesn't expose some of the nice ZFS features like these DOS modes (at least yet). I see MacOS setting DOS readonly in pcaps on my samba server.  Remember that Apple has to also make these bits such that Windows clients can set / remove them, and so the options for how such things can be implemented are limited. Looking at pcap from a MacOS server, I see the same behavior (setting DOS RO), but MacOS appears to map readonly to uchg. 
> 
> Perhaps there's benefit to having vfs_fruit set "locked" in the AFP info xattr before moving on to setting DOS readonly in the next vfs module. I don't really like the idea of setting/unsetting uchg though. That feels like it would be less than ideal for the poor soul who would have to administer the server.

I thought it might have something to do with ZoL or getfattr not showing everything. Users of this particular server like to use locking to prevent accidental changes and luckily the find command in macOS can find them and do changes in bulk if need arises.

Thanks for looking into it. In this case any code changes probably wouldn’t make it in time, but it would be of course nice to have this mapped across protocols.

-Perttu