Re: [nfsv4] [RFD] How to interpret empty path components in fs_locations/fs_locations_info

On Tue, 2010-10-19 at 21:08 -0400, david.noveck@emc.com wrote:
> >      1. The server may specify a 'pathname4' entry with no components
> >      2. The server may specify a 'pathname4' with a single component
> of
> >         length 0.
> 
> > The following question then arose: if we allow representations 
> > of type 2. above, then presumably we must also allow for the fact 
> > that the server may embed zero-length components anywhere in the 
> > 'pathname4' array. 
> 
> Why do you presume that?
> 
> I guess it is the only way you can make representation 2 appear logical.
> 
> I just don't think that representation 2 is logical.  Representation 1
> makes the most sense having more than one representation for the same
> thing does not really make sense.
> 
> But we have a practical problem, in that some servers generate
> representation 2 and it doesn't seem fair at this point to reject what
> they are sending if we can figure out what was intended.  The spec
> didn't tell them to do something else.
> 
> So I think it makes sense to say:
> 
>      you SHOULD send representation 1.
>      you MAY send representation 2.
>      you MUST NOT send a pathname4 with a zero-length component 
>          unless it is an instance of representation 2.

Agreed.

>      you MUST accept representation 1.
>      you SHOULD accept representation 2.

Agreed

>      you MUST reject a pathname 4 with a zero-length component
>          unless it is an instance of representation 2. 

I'm not sure I agree with this. If a client is given a crazy pathname by
the server, through an fs_locations request, but it still manages to
make sense of it, then why shouldn't it make the attempt? The
alternative would be to tell the application 'EIO'...

Cheers
  Trond

> -----Original Message-----
> From: nfsv4-bounces@ietf.org [mailto:nfsv4-bounces@ietf.org] On Behalf
> Of Trond Myklebust
> Sent: Tuesday, October 19, 2010 5:25 PM
> To: nfsv4@ietf.org
> Subject: [nfsv4] [RFD] How to interpret empty path components in
> fs_locations/fs_locations_info
> 
> Hi,
> 
> An issue was raised in the fedfs concall last week concerning how to
> represent the root directory in fs_locations/fs_locations_info.
> 
> As near as the group on the call could determine, there are 2 possible
> representations, neither of which appear to be explicitly forbidden by
> the spec:
> 
>      1. The server may specify a 'pathname4' entry with no components
>      2. The server may specify a 'pathname4' with a single component of
>         length 0.
> 
> The following question then arose: if we allow representations of type
> 2. above, then presumably we must also allow for the fact that the
> server may embed zero-length components anywhere in the 'pathname4'
> array. We assume that the interpretation would then be the same as a
> POSIX path of the form /a/b/////c (i.e. the path should be interpreted
> as equivalent to /a/b/c)?
> 
> The question we'd like to put to the list is therefore whether or not
> clients should be required to deal with this, or whether the spec should
> be amended to discourage (or even forbid) servers from using this kind
> of representation for a path?
> 
> Cheers
>   Trond
> 
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