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Re: FindFirstFile fails for some network directories

On Mon, Aug 17, 2015 at 3:03 PM, Orgad Shaneh <> wrote:
> Hi,
> I have 2 network shares with similar contents:
> \\netapp1\CM\CompilationResults
> \\aclnas01\versions\CompilationResults
> Trying to list all the files within these directories using Ruby
> succeeds for netapp1, but fails for aclnas01.
> The failing ruby command is:
>   ruby -e "print Dir.glob('//aclnas01/versions/CompilationResults/*')"
> The exact same command succeeds when executed from a normal command
> prompt, or when the directory is on netapp1 (on both shells).
> After debugging Ruby, I found out that FindFirstFile returns an
> INVALID_HANDLE when invoked from cygwin environment.
> The following application succeeds on command prompt and fails on cygwin:
> #include <stdio.h>
> #include <windows.h>
> int main()
> {
>     const TCHAR *aclnas = TEXT("//aclnas01/versions/CompilationResults");
>     const TCHAR *netapp = TEXT("//netapp1/CM/CompilationResults");
>     WIN32_FIND_DATA fd;
>     printf("%d\n", FindFirstFile(aclnas, &fd) !=
> INVALID_HANDLE_VALUE); // Fails on cygwin
>     printf("%d\n", FindFirstFile(netapp, &fd) !=
> INVALID_HANDLE_VALUE); // Always succeeds
>     return 0;
> }
> Output on cmd is 1 1, on cygwin it is 0 1.
> Process Monitor shows that when executed from cygwin, CreateFile is
> called with Open for Backup flag. I can't say for sure if this causes
> the failure, but that's the only difference I could find between these
> executions.
> This bug was previously reported on github/msys2[1], but it wasn't solved.
> I only have read access to these servers, but I might have cooperation
> of the sys admin (can't promise though).
> Any help will be appreciated.
> Thanks,
> - Orgad
> [1]


Using Wireshark, I discovered that aclnas01 uses SMB, while netapp1 uses SMB2.

For some reason, when executed from command prompt, a FIND_FIRST2
request is sent and the server replies, while with cygwin a "NT Create
AndX" request is sent and denied.

To minimize the captured packets, I executed the application twice,
and captured only the second execution (to avoid session initiation).

Working capture:
Failing capture:

Does cygwin implement SMB on its own, or is this difference a
side-effect of the "Backup Intent" flag?

- Orgad

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