Question

I’ve got an app that needs to disable infrastructure access and then re-enable it (please don’t ask why. I’m under NDA and it would be hard to explain why without violating that). I’m doing this with p/Invoke in C#.

To disable it, I’m creating the INTF_ENTRY structure, setting the adapter guid, then setting dwCtlFlags to 0 and calling

uint outFlags;
WZCSAPI.INTF_ENTRY intf = new WZCSAPI.INTF_ENTRY();
intf.wszGuid = adapterGuid;
intf.dwCtlFlags = 0;
WZCSetInterface(null, (uint)INTF_FLAGS.INTF_CM_MASK, ref intf, out outFlags)

This works beautifully and does exactly what I expect. My XP settings under “Wireless Network Connection Properties/Wireless Networks/Advanced” switches from “Any available network (access point preferred)” to “Computer-to-computer (ad hoc) networks only”. This is exactly what I need it to do…

Before doing this, I retrieve the original settings for the CM_MASK.

So, later on, I try the same thing to restore it (in this case, origCMMask = 2):

uint outFlags;
WZCSAPI.INTF_ENTRY intf = new WZCSAPI.INTF_ENTRY();
intf.wszGuid = adapterGuid;
intf.dwCtlFlags = origCMMask;
WZCSetInterface(null, (uint)INTF_FLAGS.INTF_CM_MASK, ref intf, out outFlags)

But the “Any Available Network” option is not restored in the settings dialog and the HKLM\SOFTWARE\Microsoft\WZCSVC\Parameters\Interface{guid}\ControlFlags concurs that the CM Mask is NOT set back to 2, but is still set to 0 (actual value is 0x07918000, instead of the normal 0x07818002).

Is there some step I’m missing?

Answer 1

You could try with the WlanSetInterface Function, if you have Windows XP with SP3, passing wlan_intf_opcode_bss_type as the OpCode.

Alternatively, you can also try manually with one of the NETSH WLAN command line actions, at least to validate the approach.