What is the purpose of CAP_LARGE_READX?

[Jeremy Allison]

On Fri, Jan 18, 2013 at 09:10:33AM +1100, Andrew Bartlett wrote:
> On Thu, 2013-01-17 at 13:54 -0800, Jeremy Allison wrote:
> > On Fri, Jan 18, 2013 at 08:44:42AM +1100, Andrew Bartlett wrote:
> > > I'm chasing a bug where a MacOSX client asks for 64k of data, we ignore
> > > the high bits, and return 0 bytes.  The client then writes a 64k zero
> > > page locally. 
> > > 
> > > The formal bug report will follow once I clear the details with the
> > > reporter, but it raised in my head some 'meta' questions.
> > > 
> > > What is the purpose of CAP_LARGE_READX?  The Samba smbd file server only
> > > mentions it to claim support for it in negprot, but does not use it in
> > > reply.c since
> > > https://git.samba.org/?p=samba.git;a=commitdiff;h=f8c26c16b82989e002b839fc9eba6386fc036f6a
> > > 
> > > I would say 'so, we should not advertise it', but the trace I've been
> > > given of Win2008R2 also claims the same flag, but that patch claims it
> > > also isn't supported.
> > > 
> > > If the only way to do large reads and writes with SMB1 is via the unix
> > > extensions, what is the purpose of the capability flag?
> > 
> > Was created to allow implementations to do unix extensions without
> > having to allow large readX or large writeX calls (there's also a
> > CAP_LARGE_WRITEX). As we're the only server who ever implemented
> > the unix extensions they appear synonomous, but they're not.
> 
> I guess what I'm puzzled at is windows advertising it, but not honouring
> it, or getting a closer idea what's really going on.

Oh, ok - if Windows is advertizing it them I'm completely confused,
and I'm not remembering the CAP flags correctly. Sorry, ignore my
previous comment :-).

Jeremy.