clr_flag(char *ifname, short flag)
static int clr_flag(char *ifname, short flag)
clr_flag(char *ifname, short flag){  struct ifreq ifr;  strcpy(ifr.ifr_name, ifname);  if (ioctl(skfd, SIOCGIFFLAGS, &ifr) < 0) {    fprintf(stderr, _("%s: unknown interface.\n"), ifname);    return -1;  }  strcpy(ifr.ifr_name, ifname);  ifr.ifr_flags &= ~flag;  if (ioctl(skfd, SIOCSIFFLAGS, &ifr) < 0) {    perror("SIOCSIFFLAGS");    return -1;  }  return(0);}