[cifs-protocol] Response to SVHDX_OPEN_DEVICE_CONTEXT[_V2] when shared VHDX is not supported

Uri Simchoni uri at samba.org
Wed Feb 24 20:40:58 UTC 2016

Hi Bryan,

This is a clarification request following recently-closed 

I would appreciate a clarification with regards to Shared VHDX and 

In the correspondence of that case, it was indicated that upon receiving 
context, an SMB3.0.2 or SMB3.1.1 server which does not support SVHDX on 
that share should ignore the context (If I understand correctly - that's 
the way to signal to the client that SVHDX is not supported).

However, my reading of [MS-SMB2], including the errata, suggests otherwise:

1. The errata says "The server MUST fail create contexts having a 
NameLength less than 4 with a STATUS_INVALID_PARAMETER error." - OK, the 
server doesn't fail the context and moves on with processing the Open.

2. says "If IsSharedVHDSupported is FALSE, the server MUST 
fail the request with STATUS_INVALID_DEVICE_REQUEST"
Whereas IsSharedVHDSupported is a global state variable signaling 
support for share VHDX - that is, it's FALSE in our case.

It is true that is about SVHDX_OPEN_DEVICE_CONTEXT and in the 
aforementioned case the context was SVHDX_OPEN_DEVICE_CONTEXT_V2, but 
read this section as relating to SVHDX_OPEN_DEVICE_CONTEXT_V2 as well, 
because there's no other reference to SVHDX_OPEN_DEVICE_CONTEXT_V2 
handling (and since it's a tunneling operation, the SMB server doesn't 
care much if it's _V2 or not).

Please advise.


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