ifaddrlist
ifaddrlist(struct ifaddrlist **ipaddrp, char *errbuf, size_t buflen)
struct ifaddrlist *al = NULL;
ssize_t ifaddrlist(struct ifaddrlist **, char *, size_t);
struct ifaddrlist *al, *al2;
n = ifaddrlist(&al, errbuf, sizeof errbuf);