如何通过C更改默认网关

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <net/if.h>
#include <arpa/inet.h>

int main() {
    int sockfd;
    struct ifreq ifr;
    struct sockaddr_in *sin;
    char *iface = "eth0";  // 需要更改默认网关的网络接口名称
    char *gateway = "192.168.0.1";  // 新的默认网关地址

    // 创建socket对象
    sockfd = socket(AF_INET, SOCK_DGRAM, 0);
    if (sockfd < 0) {
        perror("socket");
        exit(1);
    }

    // 获取网络接口的信息
    strncpy(ifr.ifr_name, iface, IFNAMSIZ);
    if (ioctl(sockfd, SIOCGIFADDR, &ifr) < 0) {
        perror("ioctl");
        close(sockfd);
        exit(1);
    }
    sin = (struct sockaddr_in *)&ifr.ifr_addr;

    // 设置新的默认网关
    sin->sin_family = AF_INET;
    sin->sin_addr.s_addr = inet_addr(gateway);
    if (ioctl(sockfd, SIOCSIFADDR, &ifr) < 0) {
        perror("ioctl");
        close(sockfd);
        exit(1);
    }

    printf("Default gateway changed to %s\n", gateway);

    // 关闭socket对象
    close(sockfd);

    return 0;
}