check network interface status

check iface

#include <stdio.h>
#include <stdlib.h>
#include <linux/sockios.h>
#include <linux/ethtool.h>
#include <stdint.h>
#include <sys/types.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <linux/if.h>
#include <unistd.h>
#include <errno.h>


static int get_iface_status(const char *iface_name)
{
    int sockfd;
    struct ifreq ifr;
    struct ethtool_value eval;
    eval.cmd = ETHTOOL_GLINK;
    /* eval.data = 0; */
    
    memset(&ifr, 0, sizeof(ifr));
    strncpy(ifr.ifr_name, iface_name, sizeof(ifr.ifr_name));
    ifr.ifr_data = (char *)&eval;

    if ((sockfd = socket(PF_PACKET, SOCK_DGRAM, 0)) == 0)
        return -1;

    if (ioctl(sockfd, SIOCETHTOOL, &ifr) == -1) {
        close(sockfd);
        perror("ioctrl");
        return -1;
    }

    close(sockfd);
    return eval.data;
}

int main()
{
    const char *test_face = "eth0";
    int ret = get_iface_status(test_face);
    if (ret == 1)
        printf("%s is up\n", test_face);
    else
        printf("%s is down\n", test_face);
    return 0;
}