Library (libinet.a)
#include <net/if.h>
void if_freenameindex (struct if_nameindex *ptr);
The argument to this function must be a pointer that was returned by if_nameindex.
The if_nametoindex subroutine, if_indextoname subroutine, and if_nameindex subroutine.
Subroutines Overview in AIX Version 4 General Programming Concepts: Writing and Debugging Programs.