Problem to read/write TAP driver in Windows 10

[Mariano Gentile]

Good Evening,


The first problem, ERROR_SUCCESS was my fault, adding debug statements
to check the other issues, which corrupted the error state.


I still have the other two problems, related with ERROR_GEN_FAILURE and
ERROR_INSUFFICIENT_BUFFER.

Any suggestions are welcome.


Best regards

Mariano Gentile


On 03/09/2018 11:46 AM, Mariano Gentile wrote:
> Good Morning,
>
> In the last days we were facing some errors in Windows 10,
> connected with the TAP driver, taken from the OpenVPN web site
> (we tested both versions, but normally we use the newest one
> tap-windows-9.21.2.exe).
>
> We faced three types of error.
>
> The first one I suppose it is just a simple mistake, since we see the
> error message:
> "Failed to read the TAP device: The operation completed successfully."
> Reading the code of "tun-win32.c" file, the "os_read_tun()" function
> returns an error
> if the "ReadFile()" function returns FALSE, but I suppose
> in that case it is not really an error, since the reported error is
> ERROR_SUCCESS.
> Even if the Microsoft documentation says that "ReadFile()" should return
> TRUE,
> I think we could easily catch this special error and just go on, do you
> agree?
>
> The second and third errors that we are facing are a bit more difficult
> to understand:
> “Failed to read from TAP device: A device attached to the system is not
> functioning.” -> ERROR_GEN_FAILURE
> "Failed to write the TAP device. The data area passed to a system call
> is too small" -> ERROR_INSUFFICIENT_BUFFER
> respectively from the function "ReadFile()" and "WriteFile()", both in
> the tun-win32.c file.
> I saw the last commits of OpenConnect and that part of code did not
> changed recently.
> I was trying to understand what is going wrong, but reading the
> Microsoft documentation,
> it seems that the two functions are indeed called in a proper way, so I
> have no clue at the moment.
>
> I would be glad to find a solution and help fixing this problem, but I
> am out of ideas.
> Do you have some hint about what could be wrong?
>
> Thanks
> Best regards
> Mariano Gentile
>

-- 
Mariano Gentile
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eMail: mag at schaeuffelhut-berger.de

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