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ControlDevice: Generate serial numbers for UsbDk devices

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Windows recognizes USB devices by PID/VID/SN combination,
for each new USB device plugged in it generates a new
cached driver information entry in the registry.

When UsbDk hides or redirects a device it creates a virtual
device with UsbDk VID/PID and a generated serial number.

On one hand, this serial number should be unique because
there should be no multiple devices with the same PID/VID/SN
combination at any given moment of time. On the other hand,
UsbDk should re-use serial numbers of unplugged devices,
because we don't want Windows to cache one more driver
information entry each time we redirect of hide a device.

This patch introduces a simple but efficient mechanism
for serial number generation for virtual UsbDk devices.

Signed-off-by: Dmitry Fleytman <dfleytma@redhat.com>
This commit is contained in:
Dmitry Fleytman 2017-02-19 13:55:24 +02:00
parent 2e945fe180
commit a4bf95a211
2 changed files with 49 additions and 0 deletions
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43
UsbDk/ControlDevice.cpp
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@ -271,6 +271,49 @@ ULONG CUsbDkControlDevice::CountDevices()
return numberDevices;
}
void CUsbDkControlDevice::RegisterHiddenDevice(CUsbDkFilterDevice &FilterDevice)
{
// Windows recognizes USB devices by PID/VID/SN combination,
// for each new USB device plugged in it generates a new
// cached driver information entry in the registry.
//
// When UsbDk hides or redirects a device it creates a virtual
// device with UsbDk VID / PID and a generated serial number.
//
// On one hand, this serial number should be unique because
// there should be no multiple devices with the same PID/VID/SN
// combination at any given moment of time. On the other hand,
// UsbDk should re-use serial numbers of unplugged devices,
// because we don't want Windows to cache one more driver
// information entry each time we redirect of hide a device.
//
// This function implements a simple but efficient mechanism
// for serial number generation for virtual UsbDk devices
CLockedContext<CWdmSpinLock> Ctx(m_HiddenDevicesLock);
bool NoSuchSN = false;
for (ULONG MinSN = 0; !NoSuchSN; MinSN++)
{
NoSuchSN = m_HiddenDevices.ForEach([MinSN](CUsbDkFilterDevice *Filter)
{ return (Filter->GetSerialNumber() != MinSN); });
if (NoSuchSN)
{
FilterDevice.SetSerialNumber(MinSN);
}
}
m_HiddenDevices.PushBack(&FilterDevice);
}
void CUsbDkControlDevice::UnregisterHiddenDevice(CUsbDkFilterDevice &FilterDevice)
{
CLockedContext<CWdmSpinLock> Ctx(m_HiddenDevicesLock);
m_HiddenDevices.Remove(&FilterDevice);
}
bool CUsbDkControlDevice::ShouldHide(const USB_DEVICE_DESCRIPTOR &DevDescriptor) const
{
auto Hide = false;