WINTUN: Error registering rings (Error 87, INVALID_ARGUMENT)

[Simon Rozman]

Hi,

> I am currently trying to create a testtool using the WINTUN driver to
> establish a 1:1 connection to another client and see what wintun is
> capable of. Unfortunately I cannot get the rings to register. I have
> written a small testprogram in order to reproduce this.
> 
>     #include <windows.h>
>     #include <winioctl.h>
>     #include <IPHlpApi.h>
>     #include <ndisguid.h>
>     #include <TlHelp32.h>
>     #include <tchar.h>
>     #include <securitybaseapi.h>
>     #include <cfgmgr32.h>
> 
>     #include <stdint.h>
>     #include <stdio.h>
>     #include <string>
>     #include <assert.h>
> 
>     #pragma pack(push, 1)

Remove the #pragma pack(push, 1)!!!

>     typedef struct _TUN_PACKET_PROTO {
>         ULONG Size;
>         UCHAR Data[]; // max packet size as defined by the driver.
>     } TUN_PACKET_PROTO;
> 
>     typedef struct _TUN_RING_PROTO {
>         volatile ULONG Head;
>         volatile ULONG Tail;
>         volatile LONG Alertable;
>         UCHAR Data[];
>     } TUN_RING_PROTO;

.
.
.

>     typedef struct _TUN_RING {
>         volatile ULONG Head;
>         volatile ULONG Tail;
>         volatile LONG Alertable;
>         UCHAR Data[WINTUN_RING_CAPACITY + (TUN_MAX_PACKET_SIZE-
> TUN_ALIGNMENT)];
>     } TUN_RING;
> 
>     typedef struct _TUN_PACKET {
>         ULONG Size;
>         UCHAR Data[WINTUN_MAX_PACKET_SIZE]; // max packet size as
> defined by the driver.
>     } TUN_PACKET;
> 
>     typedef struct _TUN_REGISTER_RINGS {
>         struct {
>             ULONG RingSize;
>             TUN_RING *Ring;
>             HANDLE TailMoved;
>         } Send, Receive;
>     } TUN_REGISTER_RINGS;
>     #pragma pack(pop)

Remove #pragma pack(pop)
 
> I cannot figure out what I am doing wrong. Can somebody point out the
> error for me? Thanks!

With the #pragma removed, your test program kind of works:

Output with #pragma pack:
Opened wintun device.
Could not register ring buffers (87).
Experiment failed.
Size TUNRING: 8454156 (8454156)
Capacity: 8388608

Output without #pragma pack:
Opened wintun device.
Size TUNRING: 8454156 (8454156)
Capacity: 8388608

And one more thing... Markus, please: why all the profanity in your code? Code is a work of art. A poetry. I understand Microsoft is silly a lot of times and difficult to go along with. But don't let that turn *you* into a silly grumpy geek. :)

Regards,
Simon