Function if_nameindex

tools/compat/if_nameindex.c:81–143

 */

struct if_nameindex *
if_nameindex(void)
{
	struct ifaddrs *ifaddrs, *ifa;
	unsigned int ni;
	int nbytes;
	struct if_nameindex *ifni, *ifni2;
	char *cp;

	if (getifaddrs(&ifaddrs) < 0)
		return(NULL);

	/*
	 * First, find out how many interfaces there are, and how
	 * much space we need for the string names.
	 */
	ni = 0;
	nbytes = 0;
	for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {
		if (ifa->ifa_addr &&
		    ifa->ifa_addr->sa_family == AF_LINK) {
			nbytes += strlen(ifa->ifa_name) + 1;
			ni++;
		}
	}

	/*
	 * Next, allocate a chunk of memory, use the first part
	 * for the array of structures, and the last part for
	 * the strings.
	 */
	cp = malloc((ni + 1) * sizeof(struct if_nameindex) + nbytes);
	ifni = (struct if_nameindex *)cp;
	if (ifni == NULL)
		goto out;
	cp += (ni + 1) * sizeof(struct if_nameindex);

	/*
	 * Now just loop through the list of interfaces again,
	 * filling in the if_nameindex array and making copies
	 * of all the strings.
	 */
	ifni2 = ifni;
	for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {
		if (ifa->ifa_addr &&
		    ifa->ifa_addr->sa_family == AF_LINK) {
			ifni2->if_index =
			    LLINDEX((struct sockaddr_dl*)ifa->ifa_addr);
			ifni2->if_name = cp;
			strcpy(cp, ifa->ifa_name);
			ifni2++;
			cp += strlen(cp) + 1;
		}
	}
	/*
	 * Finally, don't forget to terminate the array.
	 */
	ifni2->if_index = 0;