rem: string_to_number(s, 0, 255, &ftos);
add: if (string_to_number(s, 0, 255, &ftos) == -1) exit_error(PARAMETER_PROBLEM, "Invalid ftos `%s'\n", s);
context: parse_ftos(const unsigned char *s, struct ipt_FTOS_info *finfo){	unsigned int ftos;       	string_to_number(s, 0, 255, &ftos);    	finfo->ftos = (u_int8_t )ftos;    	return;}