arp_pro
ah->arp_pro = htons(ETHERTYPE_IP);
ah->arp_pro != htons(ETHERTYPE_IP) ||
arp->arp_pro != htons(ETHERTYPE_IP) ||
ap->arp_pro = htons(ETHERTYPE_IP);
ap->arp_pro != htons(ETHERTYPE_IP) ||
ntohs (ap->arp_pro) != ETHERTYPE_IP ||