The if_nameindex() function is used to obtain a list of interface names and their corresponding indices. The if_nameindex() function is not supported by IPv4-only stacks. However, if a mixture of IPv4-only and IPv4 and IPv6 stacks are active under CINET, CINET assigns a single interface index to the IPv4-only stack. This allows applications using IPv6 sockets to target an IPv4-only stack but does not allow the selection of a particular interface on an IPv4-only stack. Not all interfaces are returned in the output from if_nameindex(). VIPA interfaces are not returned. Interfaces that have never been activated are not returned.