SMB3 Unix extensions

[Steve French]

On Fri, Apr 28, 2017 at 10:53 AM, Jeremy Allison <jra at samba.org> wrote:
> On Fri, Apr 28, 2017 at 10:56:28AM +0200, Stefan Metzmacher wrote:
>> Am 27.04.2017 um 18:13 schrieb Jeremy Allison:
>> > On Thu, Apr 27, 2017 at 04:36:30PM +0200, Stefan Metzmacher wrote:
>> >>
>> >> As far as I remember the idea was to just do this by file handle.
>> >>
>> >> So the client will just try to use the create context and the returned
>> >> create context defines the features available just for that file handle.
>> >
>> > Yes, that's right.
>> >
>> >> So NO global negotiation anymore!
>> >
>> > That was my original idea, but no, we need it. The reason is
>> > (David Kruse pointed this out) that it allows the client to
>> > determine if a UNIX create context that is ignored by the server
>> > is not returned because the server can't grant or doesn't want
>> > to grant UNIX handles on this part of the file system, vs
>> > a server that doesn't grant UNIX handles because it doesn't
>> > implement UNIX extensions.
>> >
>> > The initial Negprot extension tells the client that yes,
>> > I can do UNIX handles I just don't want to for this handle.
>>
>> Why does a client need to care about this?
>> Just avoiding a few bytes for the ignored create context?
>
> No, there was a good reason, I just can't remember
> it right now whilst I'm writing my second SambaXP
> talk :-).
>
> Steve, can you remember the use case ?

The client needs to know if the server supports Unix Extensions before
it sends the SMB2 CREATE request so that it doesn't attempt to do an
unrecoverable
operation (create supersede/overwrite or delete e.g) which behaves
differently based
on whether case sensitive turns out to be supported or not.

-- 
Thanks,

Steve