net: delay freeing peer host device

With -netdev, virtio devices present offload
features to guest, depending on the backend used.
Thus, removing host netdev peer while guest is
active leads to guest-visible inconsistency and/or crashes.

As a solution, while guest (NIC) peer device exists,
we prevent the host peer from being deleted.
This patch does this by adding peer_deleted flag in nic state:
if host device is going away while guest device
is around, set this flag and keep a shell of
the host device around for as long as guest device exists.

The link is put down so all packets will get discarded.

At the moment, management can detect that device deletion
is delayed by doing info net. As a next step, we shall add
commands that control hotplug/unplug without
removing the device, and an event to report that
guest has responded to the hotplug event.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Alex Williamson <alex.williamson@redhat.com>

diff --git a/net.c b/net.c
index 3d0fde77b22af0574fd042316323436a6472f7d6..ed74c7f103bceb938c2c2a9336a7ad305b2d060c 100644 (file)
--- a/net.c
+++ b/net.c
@@ -281,29 +281,64 @@ NICState *qemu_new_nic(NetClientInfo *info,
     return nic;
 }
 
-void qemu_del_vlan_client(VLANClientState *vc)
+static void qemu_cleanup_vlan_client(VLANClientState *vc)
 {
     if (vc->vlan) {
         QTAILQ_REMOVE(&vc->vlan->clients, vc, next);
     } else {
-        if (vc->send_queue) {
-            qemu_del_net_queue(vc->send_queue);
-        }
         QTAILQ_REMOVE(&non_vlan_clients, vc, next);
-        if (vc->peer) {
-            vc->peer->peer = NULL;
-        }
     }
 
     if (vc->info->cleanup) {
         vc->info->cleanup(vc);
     }
+}
 
+static void qemu_free_vlan_client(VLANClientState *vc)
+{
+    if (!vc->vlan) {
+        if (vc->send_queue) {
+            qemu_del_net_queue(vc->send_queue);
+        }
+        if (vc->peer) {
+            vc->peer->peer = NULL;
+        }
+    }
     qemu_free(vc->name);
     qemu_free(vc->model);
     qemu_free(vc);
 }
 
+void qemu_del_vlan_client(VLANClientState *vc)
+{
+    /* If there is a peer NIC, delete and cleanup client, but do not free. */
+    if (!vc->vlan && vc->peer && vc->peer->info->type == NET_CLIENT_TYPE_NIC) {
+        NICState *nic = DO_UPCAST(NICState, nc, vc->peer);
+        if (nic->peer_deleted) {
+            return;
+        }
+        nic->peer_deleted = true;
+        /* Let NIC know peer is gone. */
+        vc->peer->link_down = true;
+        if (vc->peer->info->link_status_changed) {
+            vc->peer->info->link_status_changed(vc->peer);
+        }
+        qemu_cleanup_vlan_client(vc);
+        return;
+    }
+
+    /* If this is a peer NIC and peer has already been deleted, free it now. */
+    if (!vc->vlan && vc->peer && vc->info->type == NET_CLIENT_TYPE_NIC) {
+        NICState *nic = DO_UPCAST(NICState, nc, vc);
+        if (nic->peer_deleted) {
+            qemu_free_vlan_client(vc->peer);
+        }
+    }
+
+    qemu_cleanup_vlan_client(vc);
+    qemu_free_vlan_client(vc);
+}
+
 VLANClientState *
 qemu_find_vlan_client_by_name(Monitor *mon, int vlan_id,
                               const char *client_str)

diff --git a/net.h b/net.h
index 518cf9c1f73a080790d212bc7265b2efa53a658c..44c31a9b321f468ca4a3dbbca2bd97b5d9d45a66 100644 (file)
--- a/net.h
+++ b/net.h
@@ -72,6 +72,7 @@ typedef struct NICState {
     VLANClientState nc;
     NICConf *conf;
     void *opaque;
+    bool peer_deleted;
 } NICState;
 
 struct VLANState {