tun linux 创建

sudo ip tuntap add mode tun tun0
sudo ip link set tun0 up

sudo tunctl -t tun0
sudo ifconfig tun0 up

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.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 fd;
    }

    memset(&ifr, 0, sizeof(ifr));
    ifr.ifr_flags = IFF_TUN | IFF_NO_PI;
    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() {
    char tun_name[IFNAMSIZ];
    strcpy(tun_name, "tun0");
    int tun_fd = tun_alloc(tun_name);

    if (tun_fd < 0) {
        perror("Allocating interface");
        exit(1);
    }

    printf("TUN device %s opened with file descriptor %d
", tun_name, tun_fd);

    // 这里可以添加代码来读取和写入tun设备的数据包

    close(tun_fd);
    return 0;
}