Subject: [nfsv4] Question On the' Access' and 'Supported' bitmasks in the NFSV4 Access Operation

From: Kaukab Uddin <[email-masked]>
Date: Thu, 29 Jan 2004 11:10:40 -0800

Just trying to validate our understanding on these two bitmasks:

 1) We interpret the 'access' bitmask to reflect all supported rights for
that
      user with respect to the file; irrespective of what has been
requested.

2) We interpret the 'supported' bitmask to reflect  rights that have been
requested
     and can be supported by the server for that user.

Is our interpretation correct?

Regards;
Kaukab

---

From: Spencer Shepler <[email-masked]>
Date: Thu, 29 Jan 2004 13:52:54 -0600

On Jan 29, 2004, at 1:10 PM, Kaukab Uddin wrote:

> 1) We interpret the 'access' bitmask to reflect all supported rights 
> for that
> user with respect to the file; irrespective of what has been requested.
>
> 2) We interpret the 'supported' bitmask to reflect rights that have 
> been requested

Not quite.

To quote RFC3530:

"The first, "supported", represents the access rights for which the 
server can verify reliably."

An example of what might occur is the client asks about ACCESS4_EXTEND
and it turns out that the server does not support that concept in its 
implementation
and therefore the supported bit mask will not include ACCESS4_EXTEND to
represent the server's capabilities.

to quote again:

"The second, "access", represents the access rights available to the 
user for the filehandle provided"

Therefore the access mask is what is available to the user as 
identified in the
RPC credential (in response to the requestor's mask).  Therefore, if 
the request
was for ACCESS4_READ and ACCESS4_EXTEND, the response may
be ACCESS4_READ for the "access" bitmask and the "supported" mask would
be the same.  This indicates to the client that the user has READ 
access and
the server doesn't support EXTEND; it does not indicate the user 
doesn't have EXTEND
access.

I am sure this is still unclear. :-)

Spencer

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