netdev - [RFC v3 PATCH 5/4 PATCH] virtio-net: send gratuitous packet when needed

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Date:	Thu, 27 Oct 2011 16:57:41 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	aliguori@...ibm.com, mst@...hat.com, jan.kiszka@...mens.com,
	rusty@...tcorp.com.au, linux-kernel@...r.kernel.org,
	blauwirbel@...il.com, netdev@...r.kernel.org, stefanha@...il.com
Cc:	qemu-devel@...gnu.org, kvm@...r.kernel.org
Subject: [RFC v3 PATCH 5/4 PATCH] virtio-net: send gratuitous packet when
	needed

As hypervior does not have the knowledge of guest network
configuration, it's better to ask guest to send gratuitous packet when
needed.

This make let virtio-net driver can send gratuitous packet.

Guest check VIRTIO_NET_S_ANNOUNCE during config change interrupt. When
this bit is set, a workqueue would be scheduled to send gratuitous
packet through NETDEV_NOTIFY_PEERS.

This feature is negotiated through bit VIRTIO_NET_F_GUEST_ANNOUNCE.

Changes from v2:
- Fix the race between unregister_dev() and workqueue

Signed-off-by: Jason Wang <jasowang@...hat.com>
---
 drivers/net/virtio_net.c   |   32 ++++++++++++++++++++++++++++++--
 include/linux/virtio_net.h |    2 ++
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index b8225f3..19ee718 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -71,6 +71,9 @@ struct virtnet_info {
 	/* Work struct for refilling if we run low on memory. */
 	struct delayed_work refill;
 
+	/* Work struct for sending gratituous packet. */
+	struct work_struct announce;
+
 	/* Chain pages by the private ptr. */
 	struct page *pages;
 
@@ -507,6 +510,13 @@ static void refill_work(struct work_struct *work)
 		schedule_delayed_work(&vi->refill, HZ/2);
 }
 
+static void announce_work(struct work_struct *work)
+{
+	struct virtnet_info *vi = container_of(work, struct virtnet_info,
+					       announce);
+	netif_notify_peers(vi->dev);
+}
+
 static int virtnet_poll(struct napi_struct *napi, int budget)
 {
 	struct virtnet_info *vi = container_of(napi, struct virtnet_info, napi);
@@ -923,11 +933,23 @@ static void virtnet_update_status(struct virtnet_info *vi)
 			      &v, sizeof(v));
 
 	/* Ignore unknown (future) status bits */
-	v &= VIRTIO_NET_S_LINK_UP;
+	v &= VIRTIO_NET_S_LINK_UP | VIRTIO_NET_S_ANNOUNCE;
 
 	if (vi->status == v)
 		return;
 
+	if (v & VIRTIO_NET_S_ANNOUNCE) {
+		v &= ~VIRTIO_NET_S_ANNOUNCE;
+		vi->vdev->config->set(vi->vdev,
+				      offsetof(struct virtio_net_config,
+					       status),
+				      &v, sizeof(v));
+
+		if ((v & VIRTIO_NET_S_LINK_UP) &&
+		    virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_ANNOUNCE))
+			schedule_work(&vi->announce);
+	}
+
 	vi->status = v;
 
 	if (vi->status & VIRTIO_NET_S_LINK_UP) {
@@ -1016,6 +1038,8 @@ static int virtnet_probe(struct virtio_device *vdev)
 		goto free;
 
 	INIT_DELAYED_WORK(&vi->refill, refill_work);
+	if (virtio_has_feature(vdev, VIRTIO_NET_F_GUEST_ANNOUNCE))
+		INIT_WORK(&vi->announce, announce_work);
 	sg_init_table(vi->rx_sg, ARRAY_SIZE(vi->rx_sg));
 	sg_init_table(vi->tx_sg, ARRAY_SIZE(vi->tx_sg));
 
@@ -1075,6 +1099,8 @@ static int virtnet_probe(struct virtio_device *vdev)
 	return 0;
 
 unregister:
+	if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_ANNOUNCE))
+		cancel_work_sync(&vi->announce);
 	unregister_netdev(dev);
 	cancel_delayed_work_sync(&vi->refill);
 free_vqs:
@@ -1115,7 +1141,8 @@ static void __devexit virtnet_remove(struct virtio_device *vdev)
 	/* Stop all the virtqueues. */
 	vdev->config->reset(vdev);
 
-
+	if(virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_ANNOUNCE))
+		cancel_work_sync(&vi->announce);
 	unregister_netdev(vi->dev);
 	cancel_delayed_work_sync(&vi->refill);
 
@@ -1144,6 +1171,7 @@ static unsigned int features[] = {
 	VIRTIO_NET_F_GUEST_ECN, VIRTIO_NET_F_GUEST_UFO,
 	VIRTIO_NET_F_MRG_RXBUF, VIRTIO_NET_F_STATUS, VIRTIO_NET_F_CTRL_VQ,
 	VIRTIO_NET_F_CTRL_RX, VIRTIO_NET_F_CTRL_VLAN,
+	VIRTIO_NET_F_GUEST_ANNOUNCE,
 };
 
 static struct virtio_driver virtio_net_driver = {
diff --git a/include/linux/virtio_net.h b/include/linux/virtio_net.h
index 970d5a2..44a38d6 100644
--- a/include/linux/virtio_net.h
+++ b/include/linux/virtio_net.h
@@ -49,8 +49,10 @@
 #define VIRTIO_NET_F_CTRL_RX	18	/* Control channel RX mode support */
 #define VIRTIO_NET_F_CTRL_VLAN	19	/* Control channel VLAN filtering */
 #define VIRTIO_NET_F_CTRL_RX_EXTRA 20	/* Extra RX mode control support */
+#define VIRTIO_NET_F_GUEST_ANNOUNCE 21  /* Guest can send gratituous packet */
 
 #define VIRTIO_NET_S_LINK_UP	1	/* Link is up */
+#define VIRTIO_NET_S_ANNOUNCE   2       /* Announcement is needed */
 
 struct virtio_net_config {
 	/* The config defining mac address (if VIRTIO_NET_F_MAC) */

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