Help with IOCTL_USB_GET_DESCRIPTOR_FROM_NODE_CONNECTION

I'm trying to get the configuration descriptor for a device I already have a PUSB_NODE_CONNECTION_INFORMATION_EX structure for. I'm working off of the usbview example in the Windows DDK. Here's the relevant portion of the code...

Code:

/******************************************************
				* Fill the fields necessary for the request
				******************************************************/
				
				// Zero out the request struct
	
				len = sizeof(configreqbuf);
				memset(configreq, 0, len);
				
				configreq->ConnectionIndex = conninfo->ConnectionIndex;
	
				// descriptor type is high byte, descriptor index is low
	
				configreq->SetupPacket.wValue = ((USB_CONFIGURATION_DESCRIPTOR_TYPE << 8) | (unsigned char)0);
				configreq->SetupPacket.wLength = (unsigned short)(len - sizeof(USB_DESCRIPTOR_REQUEST));
				
				/*****************************************************
				* Get length, dynamically resize, and get descriptor
				*****************************************************/
				
				err = DeviceIoControl(rhub, IOCTL_USB_GET_DESCRIPTOR_FROM_NODE_CONNECTION, configreq, len, configreq, len, &len, NULL);
				
				if(!err || configdesc->wTotalLength < sizeof(USB_CONFIGURATION_DESCRIPTOR))
				{
					printf("DEBUG! %d\n\n", GetLastError());
					return(NULL);
				}
				configdesc = (PUSB_CONFIGURATION_DESCRIPTOR)malloc(len);
				configreq->ConnectionIndex = conninfo->ConnectionIndex;
				
				configreq->SetupPacket.wValue = ((USB_CONFIGURATION_DESCRIPTOR_TYPE << 8) | (unsigned char)0);
				configreq->SetupPacket.wLength = (unsigned short)(len - sizeof(USB_DESCRIPTOR_REQUEST));
				
				err = DeviceIoControl(rhub, IOCTL_USB_GET_DESCRIPTOR_FROM_NODE_CONNECTION, configdesc, len, configdesc, len, &len, NULL);
				
				if(!err)
					return(NULL);
					
				return(configdesc);

The declarations are here:

Code:

	HANDLE rhub, ctlr;
	PUSB_DESCRIPTOR_REQUEST configreq;
	PUSB_CONFIGURATION_DESCRIPTOR configdesc;
	char *rhubname, *tmp, *name, *configreqbuf;
	int numports = -1, i, len = 65536, err, x;
	PUSB_NODE_CONNECTION_INFORMATION_EX conninfo = (PUSB_NODE_CONNECTION_INFORMATION_EX)malloc(sizeof(unsigned char) * 65536);

It fails at the following line with error code 2 (ERROR_FILE_NOT_FOUND). Anyone know what I'm doing wrong?

I managed to fix it by not getting the size and just allocating a large buffer. It's not the most elegant solution, but I'll free it after. I have another question, however, once I have the configuration descriptor, how do I get the interface and endpoint descriptors? According to MSDN, the UsbBuildGetDescriptorRequest macro only supports three types for the third argument, DescriptorType, and those are USB_DEVICE_DESCRIPTOR_TYPE, USB_CONFIGURATION_DESCRIPTOR_TYPE, and USB_STRING_DESCRIPTOR_TYPE.

Check out the function on this page: WinUsb_QueryInterfaceSettings Function (Windows Driver Kit)
It seems to give you an interface descriptor with the number of endpoints and here you seem to be able to get info about endpoints: WinUsb_QueryPipe Function (Windows Driver Kit)