tap: use an exit notifier to call down_script

We would like to move back net_cleanup() at the end of main function,
like it used to be until f30dbae63a46f23116715dff8d130c, but minimum
tap cleanup is necessary regarless at exit() time. Use an exit notifier
to call TAP down_script. If net_cleanup() is called first, then remove
the exit notifier as it will become a dangling pointer otherwise.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20160711144847.16651-1-marcandre.lureau@redhat.com>
Reviewed-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 20 insertions, 7 deletions

diff --git a/net/tap.c b/net/tap.c
index 676bad4..e9c32f3 100644
--- a/net/tap.c
+++ b/net/tap.c
@@ -58,6 +58,7 @@ typedef struct TAPState {
     bool enabled;
     VHostNetState *vhost_net;
     unsigned host_vnet_hdr_len;
+    Notifier exit;
 } TAPState;
 
 static void launch_script(const char *setup_script, const char *ifname,
@@ -292,10 +293,22 @@ static void tap_set_offload(NetClientState *nc, int csum, int tso4,
     tap_fd_set_offload(s->fd, csum, tso4, tso6, ecn, ufo);
 }
 
+static void tap_exit_notify(Notifier *notifier, void *data)
+{
+    TAPState *s = container_of(notifier, TAPState, exit);
+    Error *err = NULL;
+
+    if (s->down_script[0]) {
+        launch_script(s->down_script, s->down_script_arg, s->fd, &err);
+        if (err) {
+            error_report_err(err);
+        }
+    }
+}
+
 static void tap_cleanup(NetClientState *nc)
 {
     TAPState *s = DO_UPCAST(TAPState, nc, nc);
-    Error *err = NULL;
 
     if (s->vhost_net) {
         vhost_net_cleanup(s->vhost_net);
@@ -304,12 +317,8 @@ static void tap_cleanup(NetClientState *nc)
 
     qemu_purge_queued_packets(nc);
 
-    if (s->down_script[0]) {
-        launch_script(s->down_script, s->down_script_arg, s->fd, &err);
-        if (err) {
-            error_report_err(err);
-        }
-    }
+    tap_exit_notify(&s->exit, NULL);
+    qemu_remove_exit_notifier(&s->exit);
 
     tap_read_poll(s, false);
     tap_write_poll(s, false);
@@ -379,6 +388,10 @@ static TAPState *net_tap_fd_init(NetClientState *peer,
     }
     tap_read_poll(s, true);
     s->vhost_net = NULL;
+
+    s->exit.notify = tap_exit_notify;
+    qemu_add_exit_notifier(&s->exit);
+
     return s;
 }