arp_pln
ah->arp_pln = sizeof (ah->arp_spa); /* protocol address length */
ah->arp_pln != sizeof (ah->arp_spa)) {
arp->arp_pln != sizeof (arp->arp_spa)) {
ap->arp_pln != sizeof(ap->arp_spa) )
ap->arp_pln = sizeof(ap->arp_spa); /* protocol address length */
ap->arp_pln);
out->arp_ea.arp_pln = sizeof (struct in_addr);
out->arp_ea.arp_pln = sizeof (struct in_addr);
ea->arp_pln = sizeof (ea->arp_spa); /* protocol address length */