if_indextoname.c raw

   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 <errno.h>
   7  #include "syscall.h"
   8  
   9  char *if_indextoname(unsigned index, char *name)
  10  {
  11  	struct ifreq ifr;
  12  	int fd, r;
  13  
  14  	if ((fd = socket(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC, 0)) < 0) return 0;
  15  	ifr.ifr_ifindex = index;
  16  	r = ioctl(fd, SIOCGIFNAME, &ifr);
  17  	__syscall(SYS_close, fd);
  18  	if (r < 0) {
  19  		if (errno == ENODEV) errno = ENXIO;
  20  		return 0;
  21  	}
  22  	return strncpy(name, ifr.ifr_name, IF_NAMESIZE);
  23  }
  24