DWORD __stdcall GetMTUDecrement ();Return Value:
The configured system-wide MTU decrement stored in the registry, or 0 if the value cannot be read
Parameters:None
Remarks:
This reads the stored MTUDecrement registry configuration, not the active adapter MTU. A valid stored decrement of 0, a missing value, or a failed registry operation all return 0; the return value cannot distinguish them.
These registry APIs do not send an IOCTL or report when the running driver adopts a new value. Coordinate activation with your driver deployment procedure. The getter opens/creates the configuration key through RegCreateKey, so access can fail under the caller’s registry permissions. See the pinned registry implementation.