net: Introduce announce timer

The 'announce timer' will be used by migration, and explicit
requests for qemu to perform network announces.

Based on the work by Germano Veit Michel <germano@redhat.com>
 and Vlad Yasevich <vyasevic@redhat.com>

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>

net/announce.c

@@ -0,0 +1,60 @@
+/*
+ *  Self-announce
+ *  (c) 2017-2019 Red Hat, Inc.
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+#include "qemu-common.h"
+#include "net/announce.h"
+#include "qapi/clone-visitor.h"
+#include "qapi/qapi-visit-net.h"
+
+int64_t qemu_announce_timer_step(AnnounceTimer *timer)
+{
+    int64_t step;
+
+    step =  timer->params.initial +
+            (timer->params.rounds - timer->round - 1) *
+            timer->params.step;
+
+    if (step < 0 || step > timer->params.max) {
+        step = timer->params.max;
+    }
+    timer_mod(timer->tm, qemu_clock_get_ms(timer->type) + step);
+
+    return step;
+}
+
+void qemu_announce_timer_del(AnnounceTimer *timer)
+{
+    if (timer->tm) {
+        timer_del(timer->tm);
+        timer_free(timer->tm);
+        timer->tm = NULL;
+    }
+}
+
+/*
+ * Under BQL/main thread
+ * Reset the timer to the given parameters/type/notifier.
+ */
+void qemu_announce_timer_reset(AnnounceTimer *timer,
+                               AnnounceParameters *params,
+                               QEMUClockType type,
+                               QEMUTimerCB *cb,
+                               void *opaque)
+{
+    /*
+     * We're under the BQL, so the current timer can't
+     * be firing, so we should be able to delete it.
+     */
+    qemu_announce_timer_del(timer);
+
+    QAPI_CLONE_MEMBERS(AnnounceParameters, &timer->params, params);
+    timer->round = params->rounds;
+    timer->type = type;
+    timer->tm = timer_new_ms(type, cb, opaque);
+}