private static void OnStabilized(IntPtr context, IntPtr table)
{
Interop.IpHlpApi.FreeMibTable(table);
TeredoHelper helper = (TeredoHelper)GCHandle.FromIntPtr(context).Target !;
// Lock the TeredoHelper instance to ensure that only the first call to OnStabilized will get to call
// RunCallback. This is the only place that TeredoHelpers get locked, as individual instances are not
// exposed to higher layers, so there's no chance for deadlock.
if (!helper._runCallbackCalled)
{
lock (helper)
{
if (!helper._runCallbackCalled)
{
helper._runCallbackCalled = true;
ThreadPool.QueueUserWorkItem(o =>
{
TeredoHelper helper = (TeredoHelper)o !;
// We are intentionally not calling Dispose synchronously inside the OnStabilized callback.
// According to MSDN, calling CancelMibChangeNotify2 inside the callback results into deadlock.
helper.Dispose();
helper._callback.Invoke(helper._state);
}, helper);
}
}
}
}
// Returns true if the address table is already stable. Otherwise, calls callback when it becomes stable.
// 'Unsafe' because it does not flow ExecutionContext to the callback.
public static unsafe bool UnsafeNotifyStableUnicastIpAddressTable(Action <object> callback, object state)
{
Debug.Assert(callback != null);
TeredoHelper?helper = new TeredoHelper(callback, state);
try
{
uint err = Interop.IpHlpApi.NotifyStableUnicastIpAddressTable(AddressFamily.Unspecified,
out SafeFreeMibTable table, &OnStabilized, GCHandle.ToIntPtr(helper._gcHandle), out helper._cancelHandle);
table.Dispose();
if (err == Interop.IpHlpApi.ERROR_IO_PENDING)
{
Debug.Assert(helper._cancelHandle != null && !helper._cancelHandle.IsInvalid);
// Suppress synchronous Dispose. Dispose will be called asynchronously by the callback.
helper = null;
return(false);
}
if (err != Interop.IpHlpApi.ERROR_SUCCESS)
{
throw new Win32Exception((int)err);
}
return(true);
}
finally
{
helper?.Dispose();
}
}