IPVERSION
ip->ip_v = IPVERSION; /* half-char */
if (ip->ip_v == IPVERSION && /* half char */
outip->ip_v = IPVERSION;
IP_V_A(ip, IPVERSION);
if (ip->ip_v != IPVERSION && ip->ip_p != IPPROTO_UDP) {
iphp->ip_v = IPVERSION;
if (iphp->ip_v != IPVERSION) {
#ifndef IPVERSION
iphp->ip_v = IPVERSION;