linux 通过tun发送

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <net/if.h>
#include <linux/if_tun.h>

#define BUF_SIZE 2048

int main() {
    int fd, err;
    struct ifreq ifr;
    char buf[BUF_SIZE];

    // 打开TUN设备
    if ((fd = open("/dev/net/tun", O_RDWR)) < 0) {
        perror("Opening /dev/net/tun");
        exit(1);
    }

    // 配置TUN设备
    memset(&ifr, 0, sizeof(ifr));
    ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
    strncpy(ifr.ifr_name, "tap0", IFNAMSIZ);

    if ((err = ioctl(fd, TUNSETIFF, (void *) &ifr)) < 0) {
        perror("ioctl(TUNSETIFF)");
        exit(1);
    }

    printf("TUN device %s opened\n", ifr.ifr_name);

    while (1) {
        // 读取数据包
        int n = read(fd, buf, BUF_SIZE);
        if (n < 0) {
            perror("Reading from interface");
            close(fd);
            exit(1);
        }

        // 处理数据包（这里简单地打印出来）
        printf("Received %d bytes: ", n);
        for (int i = 0; i < n; i++) {
            printf("%02x ", (unsigned char)buf[i]);
        }
        printf("\n");
    }

    close(fd);
    return 0;
}