fprintf(stderr, _("%s: unknown interface.\n"), ifname);
fprintf(stderr, _("%s: unknown interface: %s\n"), ifname, strerror(errno));
static int 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);}