Function if_nametoindex

tools/compat/if_nametoindex.c:75–112

 */

unsigned int
if_nametoindex(const char *ifname)
{
	int s;
	struct ifreq ifr;
	struct ifaddrs *ifaddrs, *ifa;
	unsigned int ni;

	s = _socket(AF_INET, SOCK_DGRAM | SOCK_CLOEXEC, 0);
	if (s != -1) {
		memset(&ifr, 0, sizeof(ifr));
		strlcpy(ifr.ifr_name, ifname, sizeof(ifr.ifr_name));
		if (_ioctl(s, SIOCGIFINDEX, &ifr) != -1) {
			_close(s);
			return (ifr.ifr_index);
		}
		_close(s);
	}

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

	ni = 0;

	for (ifa = ifaddrs; ifa != NULL; ifa = ifa->ifa_next) {
		if (ifa->ifa_addr &&
		    ifa->ifa_addr->sa_family == AF_LINK &&
		    strcmp(ifa->ifa_name, ifname) == 0) {
			ni = LLINDEX((struct sockaddr_dl*)ifa->ifa_addr);
			break;
		}
	}

	freeifaddrs(ifaddrs);
	if (!ni)
		errno = ENXIO;
	return(ni);
}