1#define _GNU_SOURCE
 2#include <net/if.h>
 3#include <sys/socket.h>
 4#include <sys/ioctl.h>
 5#include <string.h>
 6#include "syscall.h"
 7
 8unsigned if_nametoindex(const char *name)
 9{
10	struct ifreq ifr;
11	int fd, r;
12
13	if ((fd = socket(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC, 0)) < 0) return 0;
14	strncpy(ifr.ifr_name, name, sizeof ifr.ifr_name);
15	r = ioctl(fd, SIOCGIFINDEX, &ifr);
16	__syscall(SYS_close, fd);
17	return r < 0 ? 0 : ifr.ifr_ifindex;
18}