Pretentious Yet Pointless
``If the socket address structure with the interface name is present, an ifi_info structure is allocated and the interface flags are stored. The expected family of this socket address structure is AF_LINK, indicating a datalink socket address structure. If the sdl_nlen member is nonzero, then the interface name is copied into the ifi_info structure. Otherwise a string containing the interface index is stored as the name. If the sdl_nlen member is nonzero, then the hardware address (e.g. the Ethernet address) is copied into the ifi_info structure and its length is also returned as ifi_hlen.''
[Richard Stevens, Unix Network Programming]