[cifs-protocol] Create Context SMB2_CREATE_QUERY_ON_DISK_ID payload

[Aurélien Aptel]

Aurélien Aptel via cifs-protocol <cifs-protocol at lists.samba.org> writes:

> Hi,
>
> There is a create context SMB2_CREATE_QUERY_ON_DISK_ID that MS-SMB2
> describes as, for the request:
>
>     ("QFid")
>     The client is requesting that the server return a 32-
>     byte opaque BLOB that uniquely identifies the file
>     being opened on disk. No data is passed to the
>     server by the client.
>
> for the response:
>
>     ("QFid")
>     The server returned DiskID of the open file in a volume.
>     SMB2_CREATE_CONTEXT Response takes the same
>     form as defined in section 2.2.13.2.
>
>
> So on one side it reads "32-byte opaque blob" but on the other
> "DiskID". I could not find a reference to what is a DiskId.
>
> After some testing Windows Server seems to return the persistent file id
> + something, which Samba does as well, with the following note:
>
>     /* From conversations with Microsoft engineers at
>        the MS plugfest. The first 8 bytes are the "volume index"
>        == inode, the second 8 bytes are the "volume id",
>        == dev. This will be updated in the SMB2 doc. */
>
> Samba returns
> - file id (8 bytes)
> - device id (4 bytes)
> - padded to 32 bytes with garbage
>
> We started to rely on the first 8 bytes being the FileId in the linux
> kernel client but recently we had a customer with a Dell EMC server that
> doesn't do that.
>
> Could we clarify the situation on the meaning of this payload, or at
> least the first 8 bytes being the FileId?
>
> Cheers,
> -- 
> Aurélien Aptel / SUSE Labs Samba Team
> GPG: 1839 CB5F 9F5B FB9B AA97  8C99 03C8 A49B 521B D5D3
> SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg, DE
> GF: Felix Imendörffer, Mary Higgins, Sri Rasiah HRB 247165 (AG München)
>
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-- 
Aurélien Aptel / SUSE Labs Samba Team
GPG: 1839 CB5F 9F5B FB9B AA97  8C99 03C8 A49B 521B D5D3
SUSE Software Solutions Germany GmbH, Maxfeldstr. 5, 90409 Nürnberg, DE
GF: Felix Imendörffer, Mary Higgins, Sri Rasiah HRB 247165 (AG München)