#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/stat.h>
#include <fcntl.h>

#include <linux/if.h>
#include <linux/if_tun.h>

int tun_alloc(char *dev) {
    struct ifreq ifr;
    int fd, err;

    if ((fd = open("/dev/net/tun", O_RDWR)) < 0)
        return tun_alloc_old(dev);

    memset(&ifr, 0, sizeof(ifr));

    /* Flags: IFF_TUN   - TUN device (no Ethernet headers) 
     *        IFF_TAP   - TAP device  
     *        IFF_NO_PI - Do not provide packet information  
     */ 
    ifr.ifr_flags = IFF_TUN; 
    if(*dev)
        strncpy(ifr.ifr_name, dev, IFNAMSIZ);

    if ((err = ioctl(fd, TUNSETIFF, (void *) &ifr)) < 0) {
        close(fd);
        return err;
    }

    strcpy(dev, ifr.ifr_name);
    return fd;
} 

int main(void) {
    tun_alloc("/dev/net/tun42");
}