static void xennet_move_rx_slot(struct netfront_queue *queue, struct sk_buff *skb,
				grant_ref_t ref)
{
	int new = xennet_rxidx(queue->rx.req_prod_pvt);

	BUG_ON(queue->rx_skbs[new]);
	queue->rx_skbs[new] = skb;
	queue->grant_rx_ref[new] = ref;
	RING_GET_REQUEST(&queue->rx, queue->rx.req_prod_pvt)->id = new;
	RING_GET_REQUEST(&queue->rx, queue->rx.req_prod_pvt)->gref = ref;
	queue->rx.req_prod_pvt++;
}