addipopt
extern int addipopt(char *, struct ipopt_names *, int, char *);
inc = addipopt((char *)ip + hlen, io, hlen - sizeof(ip_t),arg);
extern int addipopt(char *, struct ipopt_names *, int, char *);
if ((inc = addipopt(op, io, len, t))) {
if ((inc = addipopt(op, io, len, t))) {