User pointers are void* values that are passed into an interface at post time and returned to the caller at completion time through one of the test functions. These pointers are never stored or transmitted over the network; they are intended for local use by the interface caller. They may be used for any purpose. For example, it may be set to point at a data structure that tracks the state of the system. When the pointer is returned at completion time, the caller can then map back to this data structure immediately without searching because it has a direct pointer.