drivers/net/virtio_net.c - kernel/msm-4.19 - Gitiles

 /* A simple network driver using virtio.
  *
  * Copyright 2007 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
  * the Free Software Foundation; either version 2 of the License, or
  * (at your option) any later version.
  *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
  *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */
 //#define DEBUG
 #include <linux/netdevice.h>
 #include <linux/etherdevice.h>
 #include <linux/module.h>
 #include <linux/virtio.h>
 #include <linux/virtio_net.h>
 #include <linux/scatterlist.h>

 static int napi_weight = 128;
 module_param(napi_weight, int, 0444);

 static int csum = 1, gso = 1;
 module_param(csum, bool, 0444);
 module_param(gso, bool, 0444);

 /* FIXME: MTU in config. */
 #define MAX_PACKET_LEN (ETH_HLEN+ETH_DATA_LEN)

 struct virtnet_info
 {
 	struct virtio_device *vdev;
 	struct virtqueue *rvq, *svq;
 	struct net_device *dev;
 	struct napi_struct napi;

 	/* The skb we couldn't send because buffers were full. */
 	struct sk_buff *last_xmit_skb;

 	/* If we need to free in a timer, this is it. */
 	struct timer_list xmit_free_timer;

 	/* Number of input buffers, and max we've ever had. */
 	unsigned int num, max;

 	/* For cleaning up after transmission. */
 	struct tasklet_struct tasklet;
 	bool free_in_tasklet;

 	/* Receive & send queues. */
 	struct sk_buff_head recv;
 	struct sk_buff_head send;
 };

 static inline struct virtio_net_hdr *skb_vnet_hdr(struct sk_buff *skb)
 {
 	return (struct virtio_net_hdr *)skb->cb;
 }

 static inline void vnet_hdr_to_sg(struct scatterlist *sg, struct sk_buff *skb)
 {
 	sg_init_one(sg, skb_vnet_hdr(skb), sizeof(struct virtio_net_hdr));
 }

 static void skb_xmit_done(struct virtqueue *svq)
 {
 	struct virtnet_info *vi = svq->vdev->priv;

 	/* Suppress further interrupts. */
 	svq->vq_ops->disable_cb(svq);

 	/* We were probably waiting for more output buffers. */
 	netif_wake_queue(vi->dev);

 	/* Make sure we re-xmit last_xmit_skb: if there are no more packets
 	 * queued, start_xmit won't be called. */
 	tasklet_schedule(&vi->tasklet);
 }

 static void receive_skb(struct net_device *dev, struct sk_buff *skb,
 			unsigned len)
 {
 	struct virtio_net_hdr *hdr = skb_vnet_hdr(skb);

 	if (unlikely(len < sizeof(struct virtio_net_hdr) + ETH_HLEN)) {
 		pr_debug("%s: short packet %i\n", dev->name, len);
 		dev->stats.rx_length_errors++;
 		goto drop;
 	}
 	len -= sizeof(struct virtio_net_hdr);
 	BUG_ON(len > MAX_PACKET_LEN);

 	skb_trim(skb, len);

 	dev->stats.rx_bytes += skb->len;
 	dev->stats.rx_packets++;

 	if (hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
 		pr_debug("Needs csum!\n");
 		if (!skb_partial_csum_set(skb,hdr->csum_start,hdr->csum_offset))
 			goto frame_err;
 	}

 	skb->protocol = eth_type_trans(skb, dev);
 	pr_debug("Receiving skb proto 0x%04x len %i type %i\n",
 		 ntohs(skb->protocol), skb->len, skb->pkt_type);

 	if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
 		pr_debug("GSO!\n");
 		switch (hdr->gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
 		case VIRTIO_NET_HDR_GSO_TCPV4:
 			skb_shinfo(skb)->gso_type = SKB_GSO_TCPV4;
 			break;
 		case VIRTIO_NET_HDR_GSO_UDP:
 			skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
 			break;
 		case VIRTIO_NET_HDR_GSO_TCPV6:
 			skb_shinfo(skb)->gso_type = SKB_GSO_TCPV6;
 			break;
 		default:
 			if (net_ratelimit())
 				printk(KERN_WARNING "%s: bad gso type %u.\n",
 				       dev->name, hdr->gso_type);
 			goto frame_err;
 		}

 		if (hdr->gso_type & VIRTIO_NET_HDR_GSO_ECN)
 			skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN;

 		skb_shinfo(skb)->gso_size = hdr->gso_size;
 		if (skb_shinfo(skb)->gso_size == 0) {
 			if (net_ratelimit())
 				printk(KERN_WARNING "%s: zero gso size.\n",
 				       dev->name);
 			goto frame_err;
 		}

 		/* Header must be checked, and gso_segs computed. */
 		skb_shinfo(skb)->gso_type |= SKB_GSO_DODGY;
 		skb_shinfo(skb)->gso_segs = 0;
 	}

 	netif_receive_skb(skb);
 	return;

 frame_err:
 	dev->stats.rx_frame_errors++;
 drop:
 	dev_kfree_skb(skb);
 }

 static void try_fill_recv(struct virtnet_info *vi)
 {
 	struct sk_buff *skb;
 	struct scatterlist sg[2+MAX_SKB_FRAGS];
 	int num, err;

 	sg_init_table(sg, 2+MAX_SKB_FRAGS);
 	for (;;) {
 		skb = netdev_alloc_skb(vi->dev, MAX_PACKET_LEN);
 		if (unlikely(!skb))
 			break;

 		skb_put(skb, MAX_PACKET_LEN);
 		vnet_hdr_to_sg(sg, skb);
 		num = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1;
 		skb_queue_head(&vi->recv, skb);

 		err = vi->rvq->vq_ops->add_buf(vi->rvq, sg, 0, num, skb);
 		if (err) {
 			skb_unlink(skb, &vi->recv);
 			kfree_skb(skb);
 			break;
 		}
 		vi->num++;
 	}
 	if (unlikely(vi->num > vi->max))
 		vi->max = vi->num;
 	vi->rvq->vq_ops->kick(vi->rvq);
 }

 static void skb_recv_done(struct virtqueue *rvq)
 {
 	struct virtnet_info *vi = rvq->vdev->priv;
 	/* Schedule NAPI, Suppress further interrupts if successful. */
 	if (netif_rx_schedule_prep(vi->dev, &vi->napi)) {
 		rvq->vq_ops->disable_cb(rvq);
 		__netif_rx_schedule(vi->dev, &vi->napi);
 	}
 }

 static int virtnet_poll(struct napi_struct *napi, int budget)
 {
 	struct virtnet_info *vi = container_of(napi, struct virtnet_info, napi);
 	struct sk_buff *skb = NULL;
 	unsigned int len, received = 0;

 again:
 	while (received < budget &&
 	       (skb = vi->rvq->vq_ops->get_buf(vi->rvq, &len)) != NULL) {
 		__skb_unlink(skb, &vi->recv);
 		receive_skb(vi->dev, skb, len);
 		vi->num--;
 		received++;
 	}

 	/* FIXME: If we oom and completely run out of inbufs, we need
 	 * to start a timer trying to fill more. */
 	if (vi->num < vi->max / 2)
 		try_fill_recv(vi);

 	/* Out of packets? */
 	if (received < budget) {
 		netif_rx_complete(vi->dev, napi);
 		if (unlikely(!vi->rvq->vq_ops->enable_cb(vi->rvq))
 		    && napi_schedule_prep(napi)) {
 			vi->rvq->vq_ops->disable_cb(vi->rvq);
 			__netif_rx_schedule(vi->dev, napi);
 			goto again;
 		}
 	}

 	return received;
 }

 static void free_old_xmit_skbs(struct virtnet_info *vi)
 {
 	struct sk_buff *skb;
 	unsigned int len;

 	while ((skb = vi->svq->vq_ops->get_buf(vi->svq, &len)) != NULL) {
 		pr_debug("Sent skb %p\n", skb);
 		__skb_unlink(skb, &vi->send);
 		vi->dev->stats.tx_bytes += skb->len;
 		vi->dev->stats.tx_packets++;
 		kfree_skb(skb);
 	}
 }

 /* If the virtio transport doesn't always notify us when all in-flight packets
  * are consumed, we fall back to using this function on a timer to free them. */
 static void xmit_free(unsigned long data)
 {
 	struct virtnet_info *vi = (void *)data;

 	netif_tx_lock(vi->dev);

 	free_old_xmit_skbs(vi);

 	if (!skb_queue_empty(&vi->send))
 		mod_timer(&vi->xmit_free_timer, jiffies + (HZ/10));

 	netif_tx_unlock(vi->dev);
 }

 static int xmit_skb(struct virtnet_info *vi, struct sk_buff *skb)
 {
 	int num, err;
 	struct scatterlist sg[2+MAX_SKB_FRAGS];
 	struct virtio_net_hdr *hdr;
 	const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest;

 	sg_init_table(sg, 2+MAX_SKB_FRAGS);

 	pr_debug("%s: xmit %p " MAC_FMT "\n", vi->dev->name, skb,
 		 dest[0], dest[1], dest[2],
 		 dest[3], dest[4], dest[5]);

 	/* Encode metadata header at front. */
 	hdr = skb_vnet_hdr(skb);
 	if (skb->ip_summed == CHECKSUM_PARTIAL) {
 		hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
 		hdr->csum_start = skb->csum_start - skb_headroom(skb);
 		hdr->csum_offset = skb->csum_offset;
 	} else {
 		hdr->flags = 0;
 		hdr->csum_offset = hdr->csum_start = 0;
 	}

 	if (skb_is_gso(skb)) {
 		hdr->hdr_len = skb_transport_header(skb) - skb->data;
 		hdr->gso_size = skb_shinfo(skb)->gso_size;
 		if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4)
 			hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
 		else if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)
 			hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
 		else if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP)
 			hdr->gso_type = VIRTIO_NET_HDR_GSO_UDP;
 		else
 			BUG();
 		if (skb_shinfo(skb)->gso_type & SKB_GSO_TCP_ECN)
 			hdr->gso_type |= VIRTIO_NET_HDR_GSO_ECN;
 	} else {
 		hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE;
 		hdr->gso_size = hdr->hdr_len = 0;
 	}

 	vnet_hdr_to_sg(sg, skb);
 	num = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1;

 	err = vi->svq->vq_ops->add_buf(vi->svq, sg, num, 0, skb);
 	if (!err && !vi->free_in_tasklet)
 		mod_timer(&vi->xmit_free_timer, jiffies + (HZ/10));

 	return err;
 }

 static void xmit_tasklet(unsigned long data)
 {
 	struct virtnet_info *vi = (void *)data;

 	netif_tx_lock_bh(vi->dev);
 	if (vi->last_xmit_skb && xmit_skb(vi, vi->last_xmit_skb) == 0) {
 		vi->svq->vq_ops->kick(vi->svq);
 		vi->last_xmit_skb = NULL;
 	}
 	if (vi->free_in_tasklet)
 		free_old_xmit_skbs(vi);
 	netif_tx_unlock_bh(vi->dev);
 }

 static int start_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct virtnet_info *vi = netdev_priv(dev);

 again:
 	/* Free up any pending old buffers before queueing new ones. */
 	free_old_xmit_skbs(vi);

 	/* If we has a buffer left over from last time, send it now. */
 	if (unlikely(vi->last_xmit_skb) &&
 	    xmit_skb(vi, vi->last_xmit_skb) != 0)
 		goto stop_queue;

 	vi->last_xmit_skb = NULL;

 	/* Put new one in send queue and do transmit */
 	if (likely(skb)) {
 		__skb_queue_head(&vi->send, skb);
 		if (xmit_skb(vi, skb) != 0) {
 			vi->last_xmit_skb = skb;
 			skb = NULL;
 			goto stop_queue;
 		}
 	}
 done:
 	vi->svq->vq_ops->kick(vi->svq);
 	return NETDEV_TX_OK;

 stop_queue:
 	pr_debug("%s: virtio not prepared to send\n", dev->name);
 	netif_stop_queue(dev);

 	/* Activate callback for using skbs: if this returns false it
 	 * means some were used in the meantime. */
 	if (unlikely(!vi->svq->vq_ops->enable_cb(vi->svq))) {
 		vi->svq->vq_ops->disable_cb(vi->svq);
 		netif_start_queue(dev);
 		goto again;
 	}
 	if (skb) {
 		/* Drop this skb: we only queue one. */
 		vi->dev->stats.tx_dropped++;
 		kfree_skb(skb);
 	}
 	goto done;
 }

 #ifdef CONFIG_NET_POLL_CONTROLLER
 static void virtnet_netpoll(struct net_device *dev)
 {
 	struct virtnet_info *vi = netdev_priv(dev);

 	napi_schedule(&vi->napi);
 }
 #endif

 static int virtnet_open(struct net_device *dev)
 {
 	struct virtnet_info *vi = netdev_priv(dev);

 	napi_enable(&vi->napi);

 	/* If all buffers were filled by other side before we napi_enabled, we
 	 * won't get another interrupt, so process any outstanding packets
 	 * now.  virtnet_poll wants re-enable the queue, so we disable here.
 	 * We synchronize against interrupts via NAPI_STATE_SCHED */
 	if (netif_rx_schedule_prep(dev, &vi->napi)) {
 		vi->rvq->vq_ops->disable_cb(vi->rvq);
 		__netif_rx_schedule(dev, &vi->napi);
 	}
 	return 0;
 }

 static int virtnet_close(struct net_device *dev)
 {
 	struct virtnet_info *vi = netdev_priv(dev);

 	napi_disable(&vi->napi);

 	return 0;
 }

 static int virtnet_probe(struct virtio_device *vdev)
 {
 	int err;
 	struct net_device *dev;
 	struct virtnet_info *vi;

 	/* Allocate ourselves a network device with room for our info */
 	dev = alloc_etherdev(sizeof(struct virtnet_info));
 	if (!dev)
 		return -ENOMEM;

 	/* Set up network device as normal. */
 	dev->open = virtnet_open;
 	dev->stop = virtnet_close;
 	dev->hard_start_xmit = start_xmit;
 	dev->features = NETIF_F_HIGHDMA;
 #ifdef CONFIG_NET_POLL_CONTROLLER
 	dev->poll_controller = virtnet_netpoll;
 #endif
 	SET_NETDEV_DEV(dev, &vdev->dev);

 	/* Do we support "hardware" checksums? */
 	if (csum && virtio_has_feature(vdev, VIRTIO_NET_F_CSUM)) {
 		/* This opens up the world of extra features. */
 		dev->features |= NETIF_F_HW_CSUM|NETIF_F_SG|NETIF_F_FRAGLIST;
 		if (gso && virtio_has_feature(vdev, VIRTIO_NET_F_GSO)) {
 			dev->features |= NETIF_F_TSO | NETIF_F_UFO
 				| NETIF_F_TSO_ECN | NETIF_F_TSO6;
 		}
 		/* Individual feature bits: what can host handle? */
 		if (gso && virtio_has_feature(vdev, VIRTIO_NET_F_HOST_TSO4))
 			dev->features |= NETIF_F_TSO;
 		if (gso && virtio_has_feature(vdev, VIRTIO_NET_F_HOST_TSO6))
 			dev->features |= NETIF_F_TSO6;
 		if (gso && virtio_has_feature(vdev, VIRTIO_NET_F_HOST_ECN))
 			dev->features |= NETIF_F_TSO_ECN;
 		if (gso && virtio_has_feature(vdev, VIRTIO_NET_F_HOST_UFO))
 			dev->features |= NETIF_F_UFO;
 	}

 	/* Configuration may specify what MAC to use.  Otherwise random. */
 	if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC)) {
 		vdev->config->get(vdev,
 				  offsetof(struct virtio_net_config, mac),
 				  dev->dev_addr, dev->addr_len);
 	} else
 		random_ether_addr(dev->dev_addr);

 	/* Set up our device-specific information */
 	vi = netdev_priv(dev);
 	netif_napi_add(dev, &vi->napi, virtnet_poll, napi_weight);
 	vi->dev = dev;
 	vi->vdev = vdev;
 	vdev->priv = vi;

 	/* If they give us a callback when all buffers are done, we don't need
 	 * the timer. */
 	vi->free_in_tasklet = virtio_has_feature(vdev,VIRTIO_F_NOTIFY_ON_EMPTY);

 	/* We expect two virtqueues, receive then send. */
 	vi->rvq = vdev->config->find_vq(vdev, 0, skb_recv_done);
 	if (IS_ERR(vi->rvq)) {
 		err = PTR_ERR(vi->rvq);
 		goto free;
 	}

 	vi->svq = vdev->config->find_vq(vdev, 1, skb_xmit_done);
 	if (IS_ERR(vi->svq)) {
 		err = PTR_ERR(vi->svq);
 		goto free_recv;
 	}

 	/* Initialize our empty receive and send queues. */
 	skb_queue_head_init(&vi->recv);
 	skb_queue_head_init(&vi->send);

 	tasklet_init(&vi->tasklet, xmit_tasklet, (unsigned long)vi);

 	if (!vi->free_in_tasklet)
 		setup_timer(&vi->xmit_free_timer, xmit_free, (unsigned long)vi);

 	err = register_netdev(dev);
 	if (err) {
 		pr_debug("virtio_net: registering device failed\n");
 		goto free_send;
 	}

 	/* Last of all, set up some receive buffers. */
 	try_fill_recv(vi);

 	/* If we didn't even get one input buffer, we're useless. */
 	if (vi->num == 0) {
 		err = -ENOMEM;
 		goto unregister;
 	}

 	pr_debug("virtnet: registered device %s\n", dev->name);
 	return 0;

 unregister:
 	unregister_netdev(dev);
 free_send:
 	vdev->config->del_vq(vi->svq);
 free_recv:
 	vdev->config->del_vq(vi->rvq);
 free:
 	free_netdev(dev);
 	return err;
 }

 static void virtnet_remove(struct virtio_device *vdev)
 {
 	struct virtnet_info *vi = vdev->priv;
 	struct sk_buff *skb;

 	/* Stop all the virtqueues. */
 	vdev->config->reset(vdev);

 	if (!vi->free_in_tasklet)
 		del_timer_sync(&vi->xmit_free_timer);

 	/* Free our skbs in send and recv queues, if any. */
 	while ((skb = __skb_dequeue(&vi->recv)) != NULL) {
 		kfree_skb(skb);
 		vi->num--;
 	}
 	__skb_queue_purge(&vi->send);

 	BUG_ON(vi->num != 0);

 	vdev->config->del_vq(vi->svq);
 	vdev->config->del_vq(vi->rvq);
 	unregister_netdev(vi->dev);
 	free_netdev(vi->dev);
 }

 static struct virtio_device_id id_table[] = {
 	{ VIRTIO_ID_NET, VIRTIO_DEV_ANY_ID },
 	{ 0 },
 };

 static unsigned int features[] = {
 	VIRTIO_NET_F_CSUM, VIRTIO_NET_F_GUEST_CSUM,
 	VIRTIO_NET_F_GSO, VIRTIO_NET_F_MAC,
 	VIRTIO_NET_F_HOST_TSO4, VIRTIO_NET_F_HOST_UFO, VIRTIO_NET_F_HOST_TSO6,
 	VIRTIO_NET_F_HOST_ECN, VIRTIO_F_NOTIFY_ON_EMPTY,
 };

 static struct virtio_driver virtio_net = {
 	.feature_table = features,
 	.feature_table_size = ARRAY_SIZE(features),
 	.driver.name =	KBUILD_MODNAME,
 	.driver.owner =	THIS_MODULE,
 	.id_table =	id_table,
 	.probe =	virtnet_probe,
 	.remove =	__devexit_p(virtnet_remove),
 };

 static int __init init(void)
 {
 	return register_virtio_driver(&virtio_net);
 }

 static void __exit fini(void)
 {
 	unregister_virtio_driver(&virtio_net);
 }
 module_init(init);
 module_exit(fini);

 MODULE_DEVICE_TABLE(virtio, id_table);
 MODULE_DESCRIPTION("Virtio network driver");
 MODULE_LICENSE("GPL");
	/* A simple network driver using virtio.
	*
	* Copyright 2007 Rusty Russell <rusty@rustcorp.com.au> IBM Corporation
	*
	* This program is free software; you can redistribute it and/or modify
	* it under the terms of the GNU General Public License as published by
	* the Free Software Foundation; either version 2 of the License, or
	* (at your option) any later version.
	*
	* This program is distributed in the hope that it will be useful,
	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	* GNU General Public License for more details.
	*
	* You should have received a copy of the GNU General Public License
	* along with this program; if not, write to the Free Software
	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
	*/
	//#define DEBUG
	#include <linux/netdevice.h>
	#include <linux/etherdevice.h>
	#include <linux/module.h>
	#include <linux/virtio.h>
	#include <linux/virtio_net.h>
	#include <linux/scatterlist.h>

	static int napi_weight = 128;
	module_param(napi_weight, int, 0444);

	static int csum = 1, gso = 1;
	module_param(csum, bool, 0444);
	module_param(gso, bool, 0444);

	/* FIXME: MTU in config. */
	#define MAX_PACKET_LEN (ETH_HLEN+ETH_DATA_LEN)

	struct virtnet_info
	{
	struct virtio_device *vdev;
	struct virtqueue rvq, svq;
	struct net_device *dev;
	struct napi_struct napi;

	/* The skb we couldn't send because buffers were full. */
	struct sk_buff *last_xmit_skb;

	/* If we need to free in a timer, this is it. */
	struct timer_list xmit_free_timer;

	/* Number of input buffers, and max we've ever had. */
	unsigned int num, max;

	/* For cleaning up after transmission. */
	struct tasklet_struct tasklet;
	bool free_in_tasklet;

	/* Receive & send queues. */
	struct sk_buff_head recv;
	struct sk_buff_head send;
	};

	static inline struct virtio_net_hdr skb_vnet_hdr(struct sk_buff skb)
	{
	return (struct virtio_net_hdr *)skb->cb;
	}

	static inline void vnet_hdr_to_sg(struct scatterlist sg, struct sk_buff skb)
	{
	sg_init_one(sg, skb_vnet_hdr(skb), sizeof(struct virtio_net_hdr));
	}

	static void skb_xmit_done(struct virtqueue *svq)
	{
	struct virtnet_info *vi = svq->vdev->priv;

	/* Suppress further interrupts. */
	svq->vq_ops->disable_cb(svq);

	/* We were probably waiting for more output buffers. */
	netif_wake_queue(vi->dev);

	/* Make sure we re-xmit last_xmit_skb: if there are no more packets
	* queued, start_xmit won't be called. */
	tasklet_schedule(&vi->tasklet);
	}

	static void receive_skb(struct net_device dev, struct sk_buff skb,
	unsigned len)
	{
	struct virtio_net_hdr *hdr = skb_vnet_hdr(skb);

	if (unlikely(len < sizeof(struct virtio_net_hdr) + ETH_HLEN)) {
	pr_debug("%s: short packet %i\n", dev->name, len);
	dev->stats.rx_length_errors++;
	goto drop;
	}
	len -= sizeof(struct virtio_net_hdr);
	BUG_ON(len > MAX_PACKET_LEN);

	skb_trim(skb, len);

	dev->stats.rx_bytes += skb->len;
	dev->stats.rx_packets++;

	if (hdr->flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
	pr_debug("Needs csum!\n");
	if (!skb_partial_csum_set(skb,hdr->csum_start,hdr->csum_offset))
	goto frame_err;
	}

	skb->protocol = eth_type_trans(skb, dev);
	pr_debug("Receiving skb proto 0x%04x len %i type %i\n",
	ntohs(skb->protocol), skb->len, skb->pkt_type);

	if (hdr->gso_type != VIRTIO_NET_HDR_GSO_NONE) {
	pr_debug("GSO!\n");
	switch (hdr->gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {
	case VIRTIO_NET_HDR_GSO_TCPV4:
	skb_shinfo(skb)->gso_type = SKB_GSO_TCPV4;
	break;
	case VIRTIO_NET_HDR_GSO_UDP:
	skb_shinfo(skb)->gso_type = SKB_GSO_UDP;
	break;
	case VIRTIO_NET_HDR_GSO_TCPV6:
	skb_shinfo(skb)->gso_type = SKB_GSO_TCPV6;
	break;
	default:
	if (net_ratelimit())
	printk(KERN_WARNING "%s: bad gso type %u.\n",
	dev->name, hdr->gso_type);
	goto frame_err;
	}

	if (hdr->gso_type & VIRTIO_NET_HDR_GSO_ECN)
	skb_shinfo(skb)->gso_type \|= SKB_GSO_TCP_ECN;

	skb_shinfo(skb)->gso_size = hdr->gso_size;
	if (skb_shinfo(skb)->gso_size == 0) {
	if (net_ratelimit())
	printk(KERN_WARNING "%s: zero gso size.\n",
	dev->name);
	goto frame_err;
	}

	/* Header must be checked, and gso_segs computed. */
	skb_shinfo(skb)->gso_type \|= SKB_GSO_DODGY;
	skb_shinfo(skb)->gso_segs = 0;
	}

	netif_receive_skb(skb);
	return;

	frame_err:
	dev->stats.rx_frame_errors++;
	drop:
	dev_kfree_skb(skb);
	}

	static void try_fill_recv(struct virtnet_info *vi)
	{
	struct sk_buff *skb;
	struct scatterlist sg[2+MAX_SKB_FRAGS];
	int num, err;

	sg_init_table(sg, 2+MAX_SKB_FRAGS);
	for (;;) {
	skb = netdev_alloc_skb(vi->dev, MAX_PACKET_LEN);
	if (unlikely(!skb))
	break;

	skb_put(skb, MAX_PACKET_LEN);
	vnet_hdr_to_sg(sg, skb);
	num = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1;
	skb_queue_head(&vi->recv, skb);

	err = vi->rvq->vq_ops->add_buf(vi->rvq, sg, 0, num, skb);
	if (err) {
	skb_unlink(skb, &vi->recv);
	kfree_skb(skb);
	break;
	}
	vi->num++;
	}
	if (unlikely(vi->num > vi->max))
	vi->max = vi->num;
	vi->rvq->vq_ops->kick(vi->rvq);
	}

	static void skb_recv_done(struct virtqueue *rvq)
	{
	struct virtnet_info *vi = rvq->vdev->priv;
	/* Schedule NAPI, Suppress further interrupts if successful. */
	if (netif_rx_schedule_prep(vi->dev, &vi->napi)) {
	rvq->vq_ops->disable_cb(rvq);
	__netif_rx_schedule(vi->dev, &vi->napi);
	}
	}

	static int virtnet_poll(struct napi_struct *napi, int budget)
	{
	struct virtnet_info *vi = container_of(napi, struct virtnet_info, napi);
	struct sk_buff *skb = NULL;
	unsigned int len, received = 0;

	again:
	while (received < budget &&
	(skb = vi->rvq->vq_ops->get_buf(vi->rvq, &len)) != NULL) {
	__skb_unlink(skb, &vi->recv);
	receive_skb(vi->dev, skb, len);
	vi->num--;
	received++;
	}

	/* FIXME: If we oom and completely run out of inbufs, we need
	* to start a timer trying to fill more. */
	if (vi->num < vi->max / 2)
	try_fill_recv(vi);

	/* Out of packets? */
	if (received < budget) {
	netif_rx_complete(vi->dev, napi);
	if (unlikely(!vi->rvq->vq_ops->enable_cb(vi->rvq))
	&& napi_schedule_prep(napi)) {
	vi->rvq->vq_ops->disable_cb(vi->rvq);
	__netif_rx_schedule(vi->dev, napi);
	goto again;
	}
	}

	return received;
	}

	static void free_old_xmit_skbs(struct virtnet_info *vi)
	{
	struct sk_buff *skb;
	unsigned int len;

	while ((skb = vi->svq->vq_ops->get_buf(vi->svq, &len)) != NULL) {
	pr_debug("Sent skb %p\n", skb);
	__skb_unlink(skb, &vi->send);
	vi->dev->stats.tx_bytes += skb->len;
	vi->dev->stats.tx_packets++;
	kfree_skb(skb);
	}
	}

	/* If the virtio transport doesn't always notify us when all in-flight packets
	* are consumed, we fall back to using this function on a timer to free them. */
	static void xmit_free(unsigned long data)
	{
	struct virtnet_info vi = (void )data;

	netif_tx_lock(vi->dev);

	free_old_xmit_skbs(vi);

	if (!skb_queue_empty(&vi->send))
	mod_timer(&vi->xmit_free_timer, jiffies + (HZ/10));

	netif_tx_unlock(vi->dev);
	}

	static int xmit_skb(struct virtnet_info vi, struct sk_buff skb)
	{
	int num, err;
	struct scatterlist sg[2+MAX_SKB_FRAGS];
	struct virtio_net_hdr *hdr;
	const unsigned char dest = ((struct ethhdr )skb->data)->h_dest;

	sg_init_table(sg, 2+MAX_SKB_FRAGS);

	pr_debug("%s: xmit %p " MAC_FMT "\n", vi->dev->name, skb,
	dest[0], dest[1], dest[2],
	dest[3], dest[4], dest[5]);

	/* Encode metadata header at front. */
	hdr = skb_vnet_hdr(skb);
	if (skb->ip_summed == CHECKSUM_PARTIAL) {
	hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
	hdr->csum_start = skb->csum_start - skb_headroom(skb);
	hdr->csum_offset = skb->csum_offset;
	} else {
	hdr->flags = 0;
	hdr->csum_offset = hdr->csum_start = 0;
	}

	if (skb_is_gso(skb)) {
	hdr->hdr_len = skb_transport_header(skb) - skb->data;
	hdr->gso_size = skb_shinfo(skb)->gso_size;
	if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4)
	hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
	else if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)
	hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
	else if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP)
	hdr->gso_type = VIRTIO_NET_HDR_GSO_UDP;
	else
	BUG();
	if (skb_shinfo(skb)->gso_type & SKB_GSO_TCP_ECN)
	hdr->gso_type \|= VIRTIO_NET_HDR_GSO_ECN;
	} else {
	hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE;
	hdr->gso_size = hdr->hdr_len = 0;
	}

	vnet_hdr_to_sg(sg, skb);
	num = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1;

	err = vi->svq->vq_ops->add_buf(vi->svq, sg, num, 0, skb);
	if (!err && !vi->free_in_tasklet)
	mod_timer(&vi->xmit_free_timer, jiffies + (HZ/10));

	return err;
	}

	static void xmit_tasklet(unsigned long data)
	{
	struct virtnet_info vi = (void )data;

	netif_tx_lock_bh(vi->dev);
	if (vi->last_xmit_skb && xmit_skb(vi, vi->last_xmit_skb) == 0) {
	vi->svq->vq_ops->kick(vi->svq);
	vi->last_xmit_skb = NULL;
	}
	if (vi->free_in_tasklet)
	free_old_xmit_skbs(vi);
	netif_tx_unlock_bh(vi->dev);
	}

	static int start_xmit(struct sk_buff skb, struct net_device dev)
	{
	struct virtnet_info *vi = netdev_priv(dev);

	again:
	/* Free up any pending old buffers before queueing new ones. */
	free_old_xmit_skbs(vi);

	/* If we has a buffer left over from last time, send it now. */
	if (unlikely(vi->last_xmit_skb) &&
	xmit_skb(vi, vi->last_xmit_skb) != 0)
	goto stop_queue;

	vi->last_xmit_skb = NULL;

	/* Put new one in send queue and do transmit */
	if (likely(skb)) {
	__skb_queue_head(&vi->send, skb);
	if (xmit_skb(vi, skb) != 0) {
	vi->last_xmit_skb = skb;
	skb = NULL;
	goto stop_queue;
	}
	}
	done:
	vi->svq->vq_ops->kick(vi->svq);
	return NETDEV_TX_OK;

	stop_queue:
	pr_debug("%s: virtio not prepared to send\n", dev->name);
	netif_stop_queue(dev);

	/* Activate callback for using skbs: if this returns false it
	* means some were used in the meantime. */
	if (unlikely(!vi->svq->vq_ops->enable_cb(vi->svq))) {
	vi->svq->vq_ops->disable_cb(vi->svq);
	netif_start_queue(dev);
	goto again;
	}
	if (skb) {
	/* Drop this skb: we only queue one. */
	vi->dev->stats.tx_dropped++;
	kfree_skb(skb);
	}
	goto done;
	}

	#ifdef CONFIG_NET_POLL_CONTROLLER
	static void virtnet_netpoll(struct net_device *dev)
	{
	struct virtnet_info *vi = netdev_priv(dev);

	napi_schedule(&vi->napi);
	}
	#endif

	static int virtnet_open(struct net_device *dev)
	{
	struct virtnet_info *vi = netdev_priv(dev);

	napi_enable(&vi->napi);

	/* If all buffers were filled by other side before we napi_enabled, we
	* won't get another interrupt, so process any outstanding packets
	* now. virtnet_poll wants re-enable the queue, so we disable here.
	* We synchronize against interrupts via NAPI_STATE_SCHED */
	if (netif_rx_schedule_prep(dev, &vi->napi)) {
	vi->rvq->vq_ops->disable_cb(vi->rvq);
	__netif_rx_schedule(dev, &vi->napi);
	}
	return 0;
	}

	static int virtnet_close(struct net_device *dev)
	{
	struct virtnet_info *vi = netdev_priv(dev);

	napi_disable(&vi->napi);

	return 0;
	}

	static int virtnet_probe(struct virtio_device *vdev)
	{
	int err;
	struct net_device *dev;
	struct virtnet_info *vi;

	/* Allocate ourselves a network device with room for our info */
	dev = alloc_etherdev(sizeof(struct virtnet_info));
	if (!dev)
	return -ENOMEM;

	/* Set up network device as normal. */
	dev->open = virtnet_open;
	dev->stop = virtnet_close;
	dev->hard_start_xmit = start_xmit;
	dev->features = NETIF_F_HIGHDMA;
	#ifdef CONFIG_NET_POLL_CONTROLLER
	dev->poll_controller = virtnet_netpoll;
	#endif
	SET_NETDEV_DEV(dev, &vdev->dev);

	/* Do we support "hardware" checksums? */
	if (csum && virtio_has_feature(vdev, VIRTIO_NET_F_CSUM)) {
	/* This opens up the world of extra features. */
	dev->features \|= NETIF_F_HW_CSUM\|NETIF_F_SG\|NETIF_F_FRAGLIST;
	if (gso && virtio_has_feature(vdev, VIRTIO_NET_F_GSO)) {
	dev->features \|= NETIF_F_TSO \| NETIF_F_UFO
	\| NETIF_F_TSO_ECN \| NETIF_F_TSO6;
	}
	/* Individual feature bits: what can host handle? */
	if (gso && virtio_has_feature(vdev, VIRTIO_NET_F_HOST_TSO4))
	dev->features \|= NETIF_F_TSO;
	if (gso && virtio_has_feature(vdev, VIRTIO_NET_F_HOST_TSO6))
	dev->features \|= NETIF_F_TSO6;
	if (gso && virtio_has_feature(vdev, VIRTIO_NET_F_HOST_ECN))
	dev->features \|= NETIF_F_TSO_ECN;
	if (gso && virtio_has_feature(vdev, VIRTIO_NET_F_HOST_UFO))
	dev->features \|= NETIF_F_UFO;
	}

	/* Configuration may specify what MAC to use. Otherwise random. */
	if (virtio_has_feature(vdev, VIRTIO_NET_F_MAC)) {
	vdev->config->get(vdev,
	offsetof(struct virtio_net_config, mac),
	dev->dev_addr, dev->addr_len);
	} else
	random_ether_addr(dev->dev_addr);

	/* Set up our device-specific information */
	vi = netdev_priv(dev);
	netif_napi_add(dev, &vi->napi, virtnet_poll, napi_weight);
	vi->dev = dev;
	vi->vdev = vdev;
	vdev->priv = vi;

	/* If they give us a callback when all buffers are done, we don't need
	* the timer. */
	vi->free_in_tasklet = virtio_has_feature(vdev,VIRTIO_F_NOTIFY_ON_EMPTY);

	/* We expect two virtqueues, receive then send. */
	vi->rvq = vdev->config->find_vq(vdev, 0, skb_recv_done);
	if (IS_ERR(vi->rvq)) {
	err = PTR_ERR(vi->rvq);
	goto free;
	}

	vi->svq = vdev->config->find_vq(vdev, 1, skb_xmit_done);
	if (IS_ERR(vi->svq)) {
	err = PTR_ERR(vi->svq);
	goto free_recv;
	}

	/* Initialize our empty receive and send queues. */
	skb_queue_head_init(&vi->recv);
	skb_queue_head_init(&vi->send);

	tasklet_init(&vi->tasklet, xmit_tasklet, (unsigned long)vi);

	if (!vi->free_in_tasklet)
	setup_timer(&vi->xmit_free_timer, xmit_free, (unsigned long)vi);

	err = register_netdev(dev);
	if (err) {
	pr_debug("virtio_net: registering device failed\n");
	goto free_send;
	}

	/* Last of all, set up some receive buffers. */
	try_fill_recv(vi);

	/* If we didn't even get one input buffer, we're useless. */
	if (vi->num == 0) {
	err = -ENOMEM;
	goto unregister;
	}

	pr_debug("virtnet: registered device %s\n", dev->name);
	return 0;

	unregister:
	unregister_netdev(dev);
	free_send:
	vdev->config->del_vq(vi->svq);
	free_recv:
	vdev->config->del_vq(vi->rvq);
	free:
	free_netdev(dev);
	return err;
	}

	static void virtnet_remove(struct virtio_device *vdev)
	{
	struct virtnet_info *vi = vdev->priv;
	struct sk_buff *skb;

	/* Stop all the virtqueues. */
	vdev->config->reset(vdev);

	if (!vi->free_in_tasklet)
	del_timer_sync(&vi->xmit_free_timer);

	/* Free our skbs in send and recv queues, if any. */
	while ((skb = __skb_dequeue(&vi->recv)) != NULL) {
	kfree_skb(skb);
	vi->num--;
	}
	__skb_queue_purge(&vi->send);

	BUG_ON(vi->num != 0);

	vdev->config->del_vq(vi->svq);
	vdev->config->del_vq(vi->rvq);
	unregister_netdev(vi->dev);
	free_netdev(vi->dev);
	}

	static struct virtio_device_id id_table[] = {
	{ VIRTIO_ID_NET, VIRTIO_DEV_ANY_ID },
	{ 0 },
	};

	static unsigned int features[] = {
	VIRTIO_NET_F_CSUM, VIRTIO_NET_F_GUEST_CSUM,
	VIRTIO_NET_F_GSO, VIRTIO_NET_F_MAC,
	VIRTIO_NET_F_HOST_TSO4, VIRTIO_NET_F_HOST_UFO, VIRTIO_NET_F_HOST_TSO6,
	VIRTIO_NET_F_HOST_ECN, VIRTIO_F_NOTIFY_ON_EMPTY,
	};

	static struct virtio_driver virtio_net = {
	.feature_table = features,
	.feature_table_size = ARRAY_SIZE(features),
	.driver.name = KBUILD_MODNAME,
	.driver.owner = THIS_MODULE,
	.id_table = id_table,
	.probe = virtnet_probe,
	.remove = __devexit_p(virtnet_remove),
	};

	static int __init init(void)
	{
	return register_virtio_driver(&virtio_net);
	}

	static void __exit fini(void)
	{
	unregister_virtio_driver(&virtio_net);
	}
	module_init(init);
	module_exit(fini);

	MODULE_DEVICE_TABLE(virtio, id_table);
	MODULE_DESCRIPTION("Virtio network driver");
	MODULE_LICENSE("GPL");