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Subject[V4 PATCH] virtio-net: send gratuitous packet when needed
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As hypervior does not have the knowledge of guest network configuration, it's
better to ask guest to send gratuitous packet when needed.

Guest test VIRTIO_NET_S_ANNOUNCE bit during config change interrupt and when it
is set, a workqueue is scheduled to send gratuitous packet through
NETDEV_NOTIFY_PEERS. This feature is negotiated through bit
VIRTIO_NET_F_GUEST_ANNOUNCE.

Changes from v3:
- cancel the workqueue during freeze

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

Signed-off-by: Jason Wang <jasowang@redhat.com>
---
drivers/net/virtio_net.c | 31 ++++++++++++++++++++++++++++++-
include/linux/virtio_net.h | 2 ++
2 files changed, 32 insertions(+), 1 deletions(-)
diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 4880aa8..45f7ac6 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c
@@ -72,6 +72,9 @@ 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;

@@ -512,6 +515,13 @@ static void refill_work(struct work_struct *work)
queue_delayed_work(system_nrt_wq, &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);
@@ -787,6 +797,8 @@ static int virtnet_close(struct net_device *dev)

/* Make sure refill_work doesn't re-enable napi! */
cancel_delayed_work_sync(&vi->refill);
+ if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_ANNOUNCE))
+ cancel_work_sync(&vi->announce);
napi_disable(&vi->napi);

return 0;
@@ -962,11 +974,23 @@ static void virtnet_update_status(struct virtnet_info *vi)
return;

/* 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) {
@@ -1076,6 +1100,8 @@ 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));

@@ -1187,6 +1213,8 @@ static int virtnet_freeze(struct virtio_device *vdev)
virtqueue_disable_cb(vi->svq);
if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_CTRL_VQ))
virtqueue_disable_cb(vi->cvq);
+ if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_ANNOUNCE))
+ cancel_work_sync(&vi->announce);

netif_device_detach(vi->dev);
cancel_delayed_work_sync(&vi->refill);
@@ -1233,6 +1261,7 @@ 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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