client_reply() is called either upon arp resolution (generally through an arp-reply) or upon the timeout of an arp-request. client_reply() simply unsets the timer associated with the arp-request and calls ipeth_arp_reply() so that ethernet packets that were waiting in the queue waiting for arp resolution can either be sent (if the arp-request got an answer) or discarded (if the arp-request timed out).