Network link detection in Linux

check_network_connection.c

#include <linux/mii.h>
#include <linux/sockios.h>

int check_iface_connected(int *psockfd)
{
    struct ifreq ifr;
    
    if (*psockfd == -1) {
        *psockfd = socket(AF_INET, SOCK_DGRAM, 0);
    }
    if (*psockfd != -1) {
        memset(&ifr, 0, sizeof(struct ifreq));
        strcpy(ifr.ifr_name, "eth0");
        if (ioctl(*psockfd, SIOCGMIIPHY, &ifr) != -1) {
            struct mii_ioctl_data *p_mii_data = (struct mii_ioctl_data *) &(ifr.ifr_data);
            p_mii_data->reg_num = MII_BMSR;
            
            if (ioctl(*psockfd, SIOCGMIIREG, &ifr) != -1) {
                if (p_mii_data->val_out & BMSR_LSTATUS) {
                    return TRUE;
                } else {
                    return FALSE;
                }
            }
        }
    }
    return FAIL;
}