gossipd: force a fresh node_announcement every 24 hours.

Even if nothing has changed.  Note that this is different from simply
re-xmitting the old one, in that it has a different timestamp, so others
will re-xmit it too.

This is a side-effect of reports that node_announcement propagation
through the network is poor:

	https://github.com/ElementsProject/lightning/issues/5037

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Protocol: We now refresh our ndoe_announcement every 24 hours, due to propagation issues.

gossipd/gossip_generation.c

@@ -214,13 +214,16 @@ static void sign_and_send_nannounce(struct daemon *daemon,
 
 /* Mutual recursion via timer */
 static void update_own_node_announcement_after_startup(struct daemon *daemon);
+static void setup_force_nannounce_regen_timer(struct daemon *daemon);
 
 /* This routine created a `node_announcement` for our node, and hands it to
  * the routing.c code like any other `node_announcement`.  Such announcements
  * are only accepted if there is an announced channel associated with that node
  * (to prevent spam), so we only call this once we've announced a channel. */
 /* Returns true if this sent one, or has arranged to send one in future. */
-static bool update_own_node_announcement(struct daemon *daemon, bool startup)
+static bool update_own_node_announcement(struct daemon *daemon,
+					 bool startup,
+					 bool always_refresh)
 {
 	u32 timestamp = gossip_time_now(daemon->rstate).ts.tv_sec;
 	u8 *nannounce;
@@ -247,6 +250,8 @@ static bool update_own_node_announcement(struct daemon *daemon, bool startup)
 
 		if (!nannounce_different(daemon->rstate->gs, self, nannounce,
 					 &only_missing_tlv)) {
+			if (always_refresh)
+				goto send;
 			return false;
 		}
 
@@ -288,7 +293,12 @@ static bool update_own_node_announcement(struct daemon *daemon, bool startup)
 		}
 	}
 
+send:
 	sign_and_send_nannounce(daemon, nannounce, timestamp);
+
+	/* Generate another one in 24 hours. */
+	setup_force_nannounce_regen_timer(daemon);
+
 	return true;
 }
 
@@ -303,10 +313,36 @@ static void force_self_nannounce_rexmit(struct daemon *daemon)
 static void update_own_node_announcement_after_startup(struct daemon *daemon)
 {
 	/* If that doesn't send one, arrange rexmit anyway */
-	if (!update_own_node_announcement(daemon, false))
+	if (!update_own_node_announcement(daemon, false, false))
 		force_self_nannounce_rexmit(daemon);
 }
 
+/* This creates and transmits a *new* node announcement */
+static void force_self_nannounce_regen(struct daemon *daemon)
+{
+	struct node *self = get_node(daemon->rstate, &daemon->id);
+
+	/* No channels left?  We'll restart timer once we have one. */
+	if (!self || !self->bcast.index)
+		return;
+
+	update_own_node_announcement(daemon, false, true);
+}
+
+/* Because node_announcement propagation is spotty, we rexmit this every
+ * 24 hours. */
+static void setup_force_nannounce_regen_timer(struct daemon *daemon)
+{
+	tal_free(daemon->node_announce_regen_timer);
+	daemon->node_announce_regen_timer
+		= new_reltimer(&daemon->timers,
+			       daemon,
+			       time_from_sec(24 * 3600),
+			       force_self_nannounce_regen,
+			       daemon);
+}
+
+
 /* Should we announce our own node?  Called at strategic places. */
 void maybe_send_own_node_announce(struct daemon *daemon, bool startup)
 {
@@ -318,7 +354,7 @@ void maybe_send_own_node_announce(struct daemon *daemon, bool startup)
 		return;
 
 	/* If we didn't send one, arrange rexmit of existing at startup */
-	if (!update_own_node_announcement(daemon, startup)) {
+	if (!update_own_node_announcement(daemon, startup, false)) {
 		if (startup)
 			force_self_nannounce_rexmit(daemon);
 	}

gossipd/gossipd.c

@@ -1059,6 +1059,7 @@ int main(int argc, char *argv[])
 	list_head_init(&daemon->peers);
 	daemon->deferred_txouts = tal_arr(daemon, struct short_channel_id, 0);
 	daemon->node_announce_timer = NULL;
+	daemon->node_announce_regen_timer = NULL;
 	daemon->current_blockheight = 0; /* i.e. unknown */
 	daemon->rates = NULL;
 	list_head_init(&daemon->deferred_updates);

gossipd/gossipd.h

@@ -47,9 +47,12 @@ struct daemon {
 	/* What addresses we can actually announce. */
 	struct wireaddr *announcable;
 
-	/* Timer until we can send a new node_announcement */
+	/* Timer until we can send an updated node_announcement */
 	struct oneshot *node_announce_timer;
 
+	/* Timer until we should force a new new node_announcement */
+	struct oneshot *node_announce_regen_timer;
+
 	/* Channels we have an announce for, but aren't deep enough. */
 	struct short_channel_id *deferred_txouts;