linux+加载tun.ko

sudo modprobe tun

sudo insmod /lib/modules/$(uname -r)/kernel/drivers/net/tun.ko

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.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) {
        perror("Opening /dev/net/tun");
        return fd;
    }

    memset(&ifr, 0, sizeof(ifr));
    ifr.ifr_flags = IFF_TAP | IFF_NO_PI;

    strncpy(ifr.ifr_name, dev, IFNAMSIZ);

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

    return fd;
}

int main() {
    char tun_name[IFNAMSIZ];
    char buffer[2048];
    int tun_fd;

    strcpy(tun_name, "tap0");
    tun_fd = tun_alloc(tun_name);

    if (tun_fd < 0) {
        printf("Error allocating TUN device %s\n", tun_name);
        exit(1);
    }

    printf("Successfully allocated TUN device: %s\n", tun_name);

    while (1) {
        int nread = read(tun_fd, buffer, sizeof(buffer));
        if (nread < 0) {
            perror("Reading from interface");
            close(tun_fd);
            exit(1);
        }

        // Process the data in 'buffer' here

        // For example, just echo the data back
        write(tun_fd, buffer, nread);
    }

    close(tun_fd);
    return 0;
}