Create an ARP reply (just change what needs to be changed
    from a request)

def create_ip_arp_reply(srchw, dsthw, srcip, targetip):
    '''
    Create an ARP reply (just change what needs to be changed
    from a request)
    '''
    pkt = create_ip_arp_request(srchw, srcip, targetip)
    pkt[0].dst = dsthw
    pkt[1].operation = ArpOperation.Reply
    pkt[1].targethwaddr = dsthw
    return pkt