Does the CreateDisposition flag of a client depend on Server's response ?

[Tom Talpey]

This is worth figuring out.

Because it's a file in your Downloads folder, it was probably
created by a browser. This means it has an additional stream
which indicates it's from the internet. Defender and other
tools use the presence of that stream to throw the "Do you
really want to open this file?" dialogs.

When you copy the file to a non-stream filesystem, that stream
is obviously lost, in which case robocopy is not going to do
anything special. But when copying to a filesystem that does,
it will take a different path, copying everything. Or maybe it's
the fact that it's in the Downloads folder, and robocopy is
being clever. Or just a bug in the Win10 robocopy you mentioned
you're using.

Would you happen to have a Windows system with an NTFS share
that you could robocopy the same file to, and grab a trace?

It would give us the breadcrumbs to figure out what's missing.
Maybe there's some other volume or filesystem attribute that's
missing, and confusing robocopy.

Tom.

On 2/4/2023 3:17 AM, varun mittal wrote:
> Nothing fancy, simple copy command:
> robocopy C:\Users\mittal\Downloads Y:\Shared\Folder1\Subfolder 
> <file-name> /COPY:DAT /R:1 /W:10
> 
> On Sat, Feb 4, 2023, 8:05 AM Tom Talpey <tom at talpey.com 
> <mailto:tom at talpey.com>> wrote:
> 
>     On 2/3/2023 12:50 PM, Jeremy Allison via samba-technical wrote:
>      > On Fri, Feb 03, 2023 at 08:51:57PM +0530, varun mittal wrote:
>      >>   I was able to narrow it down to the "Named Streams" bit in
>      >>   "FileFSAttributeInformation" response.
>      >>   When this value is toggled from 0 to 1, as is advertised by
>      >>   `streams_xattr` VFS module, Robocopy
>      >>   switched from FILE_OPEN to FILE_OPEN_IF.
>      >>   Thanks
>      >
>      > Thanks for tracking that down. What strange behavior.
>      > I can't see why having a stream would make the open
>      > change to optionally creating the file, but it's good
>      > info to know. Thanks for posting the follow-up to
>      > the list !
> 
>     It's not the presence af a stream, it's that the fileystem supports
>     named streams. It's getting that from a FileFsAttributeInformation
>     on the root directory.
> 
>     Robocopy has a very broad range of OS- and FS-dependent behaviors
>     and optimizations. I bet there's some combination of its 1000-odd
>     commandline options that can change this.
> 
>     Varun, what exact robocopy command are you seeing this from?
> 
>     Tom.
>