tap.c

/**
 * tap.c
 * Function: Implementation of TAP device creation and management
 * Author: Cyans from Chang'an University
 */

#include "tap.h"

int tap_alloc(char *dev) {
    struct ifreq ifr;
    int fd, err; 
    
    if ((fd = open("/dev/net/tun", O_RDWR)) < 0) {
        perror("Opening /dev/net/tun");
        return fd;
    }

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

    ifr.ifr_flags = IFF_TAP | IFF_NO_PI;

    if (*dev) {
        strncpy(ifr.ifr_name, dev, IFNAMSIZ);
    }

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

    strcpy(dev, ifr.ifr_name);

    return fd; 
}