virtio-net: announce self by guest

It's hard to track all mac addresses and their configurations (e.g
vlan or ipv6) in qemu. Without this information, it's impossible to
build proper garp packet after migration. The only possible solution
to this is let guest (who knows all configurations) to do this.

So, this patch introduces a new readonly config status bit of virtio-net,
VIRTIO_NET_S_ANNOUNCE which is used to notify guest to announce
presence of its link through config update interrupt.When guest has
done the announcement, it should ack the notification through
VIRTIO_NET_CTRL_ANNOUNCE_ACK cmd. This feature is negotiated by a new
feature bit VIRTIO_NET_F_ANNOUNCE (which has already been supported by
Linux guest).

During load, a counter of announcing rounds is set so that after the vm is
running it can trigger rounds of config interrupts to notify the guest to build
and send the correct garps.

Cc: Liuyongan <liuyongan@huawei.com>
Cc: Amos Kong <akong@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

1 files changed, 42 insertions, 0 deletions

diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c
index 0a34a8b908..318b033911 100644
--- a/hw/net/virtio-net.c
+++ b/hw/net/virtio-net.c
@@ -99,6 +99,16 @@ static bool virtio_net_started(VirtIONet *n, uint8_t status)
         (n->status & VIRTIO_NET_S_LINK_UP) && vdev->vm_running;
 }
 
+static void virtio_net_announce_timer(void *opaque)
+{
+    VirtIONet *n = opaque;
+    VirtIODevice *vdev = VIRTIO_DEVICE(n);
+
+    n->announce_counter--;
+    n->status |= VIRTIO_NET_S_ANNOUNCE;
+    virtio_notify_config(vdev);
+}
+
 static void virtio_net_vhost_status(VirtIONet *n, uint8_t status)
 {
     VirtIODevice *vdev = VIRTIO_DEVICE(n);
@@ -322,6 +332,9 @@ static void virtio_net_reset(VirtIODevice *vdev)
     n->nobcast = 0;
     /* multiqueue is disabled by default */
     n->curr_queues = 1;
+    timer_del(n->announce_timer);
+    n->announce_counter = 0;
+    n->status &= ~VIRTIO_NET_S_ANNOUNCE;
 
     /* Flush any MAC and VLAN filter table state */
     n->mac_table.in_use = 0;
@@ -731,6 +744,23 @@ static int virtio_net_handle_vlan_table(VirtIONet *n, uint8_t cmd,
     return VIRTIO_NET_OK;
 }
 
+static int virtio_net_handle_announce(VirtIONet *n, uint8_t cmd,
+                                      struct iovec *iov, unsigned int iov_cnt)
+{
+    if (cmd == VIRTIO_NET_CTRL_ANNOUNCE_ACK &&
+        n->status & VIRTIO_NET_S_ANNOUNCE) {
+        n->status &= ~VIRTIO_NET_S_ANNOUNCE;
+        if (n->announce_counter) {
+            timer_mod(n->announce_timer,
+                      qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL) +
+                      self_announce_delay(n->announce_counter));
+        }
+        return VIRTIO_NET_OK;
+    } else {
+        return VIRTIO_NET_ERR;
+    }
+}
+
 static int virtio_net_handle_mq(VirtIONet *n, uint8_t cmd,
                                 struct iovec *iov, unsigned int iov_cnt)
 {
@@ -794,6 +824,8 @@ static void virtio_net_handle_ctrl(VirtIODevice *vdev, VirtQueue *vq)
             status = virtio_net_handle_mac(n, ctrl.cmd, iov, iov_cnt);
         } else if (ctrl.class == VIRTIO_NET_CTRL_VLAN) {
             status = virtio_net_handle_vlan_table(n, ctrl.cmd, iov, iov_cnt);
+        } else if (ctrl.class == VIRTIO_NET_CTRL_ANNOUNCE) {
+            status = virtio_net_handle_announce(n, ctrl.cmd, iov, iov_cnt);
         } else if (ctrl.class == VIRTIO_NET_CTRL_MQ) {
             status = virtio_net_handle_mq(n, ctrl.cmd, iov, iov_cnt);
         } else if (ctrl.class == VIRTIO_NET_CTRL_GUEST_OFFLOADS) {
@@ -1451,6 +1483,12 @@ static int virtio_net_load(QEMUFile *f, void *opaque, int version_id)
         qemu_get_subqueue(n->nic, i)->link_down = link_down;
     }
 
+    if (vdev->guest_features & (0x1 << VIRTIO_NET_F_GUEST_ANNOUNCE) &&
+        vdev->guest_features & (0x1 << VIRTIO_NET_F_CTRL_VQ)) {
+        n->announce_counter = SELF_ANNOUNCE_ROUNDS;
+        timer_mod(n->announce_timer, qemu_clock_get_ms(QEMU_CLOCK_VIRTUAL));
+    }
+
     return 0;
 }
 
@@ -1553,6 +1591,8 @@ static void virtio_net_device_realize(DeviceState *dev, Error **errp)
     qemu_macaddr_default_if_unset(&n->nic_conf.macaddr);
     memcpy(&n->mac[0], &n->nic_conf.macaddr, sizeof(n->mac));
     n->status = VIRTIO_NET_S_LINK_UP;
+    n->announce_timer = timer_new_ms(QEMU_CLOCK_VIRTUAL,
+                                     virtio_net_announce_timer, n);
 
     if (n->netclient_type) {
         /*
@@ -1629,6 +1669,8 @@ static void virtio_net_device_unrealize(DeviceState *dev, Error **errp)
         }
     }
 
+    timer_del(n->announce_timer);
+    timer_free(n->announce_timer);
     g_free(n->vqs);
     qemu_del_nic(n->nic);
     virtio_cleanup(vdev);