[Qemu-devel] [PATCH] vhost: disable on tap link down

["Michael S. Tsirkin" <mst@redhat.com>]

qemu makes it possible to disable link at tap
which is not communicated to the guest but
causes all packets to be dropped.

Handle this with vhost simply by moving to the userspace emulation.

Note: it might be a good idea to make peer link status match
tap in this case, so the guest gets an event
and updates the carrier state. For now
stay bug for bug compatible with what we used to have.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reported-by: pradeep <psuriset@linux.vnet.ibm.com>
---

Untested.
Pradeep, mind trying this patch out and reporting?
Thanks!

 hw/virtio-net.c |    4 ++++
 net.c           |    7 +++++++
 2 files changed, 11 insertions(+), 0 deletions(-)

diff --git a/hw/virtio-net.c b/hw/virtio-net.c
index 671d952..fc2d6f5 100644
--- a/hw/virtio-net.c
+++ b/hw/virtio-net.c
@@ -112,6 +112,10 @@ static void virtio_net_vhost_status(VirtIONet *n, uint8_t status)
         return;
     }
 
+    if (n->nic->nc.peer->link_down) {
+        return;
+    }
+
     if (!tap_get_vhost_net(n->nic->nc.peer)) {
         return;
     }
diff --git a/net.c b/net.c
index 9ba5be2..57ee997 100644
--- a/net.c
+++ b/net.c
@@ -1324,6 +1324,13 @@ done:
     if (vc->info->link_status_changed) {
         vc->info->link_status_changed(vc);
     }
+
+    /* Notify peer. Don't update peer link status: this makes it possible to
+     * disconnect from host network without notifying the guest.
+     * FIXME: is this useful? Could just be an artifact of vlan support. */
+    if (vc->peer && vc->peer->info->link_status_changed) {
+        vc->peer->info->link_status_changed(vc->peer);
+    }
     return 0;
 }
 
-- 
1.7.3.2.91.g446ac