Re: [Openvpn-users] Re: No TAP-Win32 adapter in XP SP2

[James Yonan <jim@xxxxxxxxx>]

On Wed, 2 Mar 2005, Scott Hughes wrote:

> James Yonan <jim <at> yonan.net> writes:
> > That's quite unusual.  99%+ of people who install 2.0 on XP SP2 get the 
> > icon, unless they are using an installer which hides it.  Are 
> > you using the GUI or non-GUI install?
> 
> I started off with the GUI install.  I then tried the non-GUI install.  Then I
> tried other software packages (such as tinc and colinux) which use the TAP-Win32
> adapter to see if one of those had the magic touch.  None of these put the icon
> in my Network Connections folder.
> 
> I tried digging around the 'netsh' cli to see if there was some way to
> manipulate the adapter..  Such as giving it a name or bridging it with another
> connection.  I couldn't figure out how to do that, and I didn't see any hint
> that it was possible.
> 
> And I figured it was an odd problem, since any reference to the problem I could
> find seemed to be resolved by using the latest version (with the HWID change). 
> With my friend google, I couldn't find a single occurence of someone who had
> this problem with a more recent version of OpenVPN and XP SP2.  I want this to
> work so badly, I'm contemplating a re-install of WindowsXP...  But, if someone
> knew what the "secret knock" is to get it to show up, I'd appreciate the time
> you'll save me.

While I'd certainly like to get to the bottom of this latest
disappearance, you should also understand that having the icon is not
necessary for OpenVPN to function.  Some people even hide it on purpose.  
OpenVPN doesn't care if the icon exists and will even let you choose a
hidden adapter using the "dev-node" directive, by referring directly to
the device GUID.  In most cases, you don't even need the "dev-node"  
directive.  OpenVPN will automatically find a free TAP-Win32 adapter, even
one that lacks an icon.

Just for reference, here is my current understanding of the hidden adapter 
issue:

Windows provides a "feature" that allows a device driver to indicate in 
it's INF file that it would like to be hidden.  For example in the 
TAP-Win32 INF file, we have:

;----------------- Characteristics ------------
;    NCF_PHYSICAL = 0x04
;    NCF_VIRTUAL = 0x01
;    NCF_SOFTWARE_ENUMERATED = 0x02
;    NCF_HIDDEN = 0x08
;    NCF_NO_SERVICE = 0x10
;    NCF_HAS_UI = 0x80
;----------------- Characteristics ------------

[tap0801.ndi]
   CopyFiles       = tap0801.driver, tap0801.files
   AddReg          = tap0801.reg
   AddReg          = tap0801.params.reg
   Characteristics = 0x81
;--------------------------------------------

If the registry item "Characteristics" has the NCF_HIDDEN (0x08) bit set,
the adapter will be hidden (e.g. Characteristics = 0x89). It also seems
that there are other, undocumented triggers which will cause the adapter
icon to be hidden, such as length of the HWID string.  There may be even 
additional undocumented triggers that we don't know about.

One thing that might be worth checking is to verify that the 
"Characteristics" registry entry for the device is in fact 0x81.

It might also be worth checking out this newsgroup:

http://groups-beta.google.com/group/microsoft.public.development.device.drivers

This is where most driver development discussion takes place.  MS 
employees are active in the group.

James

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