[PATCH] vfs: ignore shared VHDX create context by default

[Steve French]

On Wed, Feb 24, 2016 at 11:32 PM, Uri Simchoni <uri at samba.org> wrote:
> Hi,
>
> Attached is a fix for https://bugzilla.samba.org/show_bug.cgi?id=11753.
>
> This patch causes smbd to ignore SVHDX_OPEN_DEVICE_CONTEXT or
> SVHDX_OPEN_DEVICE_CONTEXT_V2 create contexts by default.
>
> The default can be overriden by a VFS module if this module adds support for
> RSVD protocol (not sure all the pieces are in there).
>
> This fixes Windows backup against Samba 4.3.x series.
>
> [MS-SMB2] rev 48.0 states (3.3.5.9.14) that the open should fail if this
> create context is specified and the server does not support RSVD (a.k.a.
> SCSI tunneling) protocol. However, according to discussions with
> dochelp at microsoft.com, the context should be ignored in this case.
>
> Review/push appreciated.
>
> Thanks,
> Uri.

I also saw this context used in VHD/VHDX creation, and with
current 4-4-stable (and 4-4-test) branch, from the Windows 2012R2
GUIs for creating virtual machines:

Computer Management -> Disk Management -> More Actions -> Create VHDX

I can create a VHDX on a NET USEd drive to current Samba 4.4-rc

but, I have a second apparently identical Windows 2012R2 server
for which I get an "Incorrect Function" pop up error doing the
same thing.   Comparing the wireshark traces I don't
see obvious reasons for the error, the ioctl errors
are the expected ones (set resiliency, integrity, compression)
and no obvious create errors.

Any ideas why HyperV VHDX creation would fail to current
Samba (to the same server) in some cases (Windows 2012R2
install/config as client to Samba)  but not others?

-- 
Thanks,

Steve