github.com/afumu/libc@v0.0.6/musl/src/network/if_nametoindex.c (about)

     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  
     8  unsigned 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  }