Skip packet on NBL allocation failure properly

Should NBL allocation persist to fail, the receive ring could eventually
fill up as there will be no TunReturnNetBufferLists() calls to advance
its head.

Signed-off-by: Simon Rozman <simon@rozman.si>

wintun.c

@@ -503,6 +503,8 @@ TunProcessReceiveData(_Inout_ TUN_CTX *Ctx)
         if (!Nbl)
         {
             InterlockedIncrement64((LONG64 *)&Ctx->Statistics.ifInDiscards);
+            KeWaitForSingleObject(&Ctx->Device.Receive.ActiveNbls.Empty, Executive, KernelMode, FALSE, NULL);
+            InterlockedSetU(&Ring->Head, RingHead);
             continue;
         }