_simple_hash
hash_index = _simple_hash(hash_start, hash_size);
hash_index = _simple_hash((u8 *)&(arp->ip_src), sizeof(arp->ip_src));
hash_index = _simple_hash((u8 *)&arp->ip_dst, sizeof(arp->ip_dst));
u32 hash_src = _simple_hash((u8 *)&arp->ip_src,
u32 ip_src_hash = _simple_hash((u8 *)&(arp->ip_src), sizeof(arp->ip_src));