filter-buffer: Add status_changed callback processing

While the status of filter-buffer changing from 'on' to 'off',
it need to release all the buffered packets, and delete the related
timer, while switch from 'off' to 'on', it need to resume the release
packets timer.

Here, we extract the process of setup timer into a new helper,
which will be used in the new status_changed callback.
Signed-off-by: Nzhanghailiang <zhang.zhanghailiang@huawei.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Yang Hongyang <hongyang.yang@easystack.cn>
Signed-off-by: NJason Wang <jasowang@redhat.com>

net/filter-buffer.c

@@ -100,6 +100,19 @@ static void filter_buffer_cleanup(NetFilterState *nf)
     }
 }
 
+static void filter_buffer_setup_timer(NetFilterState *nf)
+{
+    FilterBufferState *s = FILTER_BUFFER(nf);
+
+    if (s->interval) {
+        timer_init_us(&s->release_timer, QEMU_CLOCK_VIRTUAL,
+                      filter_buffer_release_timer, nf);
+        /* Timer armed to fire in s->interval microseconds. */
+        timer_mod(&s->release_timer,
+                  qemu_clock_get_us(QEMU_CLOCK_VIRTUAL) + s->interval);
+    }
+}
+
 static void filter_buffer_setup(NetFilterState *nf, Error **errp)
 {
     FilterBufferState *s = FILTER_BUFFER(nf);
@@ -115,12 +128,20 @@ static void filter_buffer_setup(NetFilterState *nf, Error **errp)
     }
 
     s->incoming_queue = qemu_new_net_queue(qemu_netfilter_pass_to_next, nf);
-    if (s->interval) {
-        timer_init_us(&s->release_timer, QEMU_CLOCK_VIRTUAL,
-                      filter_buffer_release_timer, nf);
-        /* Timer armed to fire in s->interval microseconds. */
-        timer_mod(&s->release_timer,
-                  qemu_clock_get_us(QEMU_CLOCK_VIRTUAL) + s->interval);
+    filter_buffer_setup_timer(nf);
+}
+
+static void filter_buffer_status_changed(NetFilterState *nf, Error **errp)
+{
+    FilterBufferState *s = FILTER_BUFFER(nf);
+
+    if (!nf->on) {
+        if (s->interval) {
+            timer_del(&s->release_timer);
+        }
+        filter_buffer_flush(nf);
+    } else {
+        filter_buffer_setup_timer(nf);
     }
 }
 
@@ -131,6 +152,7 @@ static void filter_buffer_class_init(ObjectClass *oc, void *data)
     nfc->setup = filter_buffer_setup;
     nfc->cleanup = filter_buffer_cleanup;
     nfc->receive_iov = filter_buffer_receive_iov;
+    nfc->status_changed = filter_buffer_status_changed;
 }
 
 static void filter_buffer_get_interval(Object *obj, Visitor *v,