linux probe whether network line is attached to network card normally

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

 

// ifname like "eth0".
// Notice: call this function need root privilege.
// return value:
// -1 -- error , details about error, pls check errno
// 1 -- interface link up
// 0 -- interface link down.

inline int GetNetlinkStatus(uint8_t *ifname)
{
    int sockfd;
    struct ifreq ifr;
    struct ethtool_value edata;

    edata.cmd = ETHTOOL_GLINK;
    edata.data = 0;

    memset(&ifr, 0, sizeof(ifr));
    strncpy(ifr.ifr_name, (char *)ifname, sizeof(ifr.ifr_name) - 1);

    ifr.ifr_data = (char *) &edata;

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

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

    close(sockfd);

    return edata.data;
}