static void prep_ifreq(struct ifreq *ifr, const char *ifname)
{
    memset(ifr, 0, sizeof(*ifr));
    snprintf(ifr->ifr_name, IFNAMSIZ, "%s", ifname);
}
static void prep_ifreq(struct ifreq *ifr, const char *ifname)
{
    memset(ifr, 0, sizeof(*ifr));
    snprintf(ifr->ifr_name, IFNAMSIZ, "%s", ifname);
}