gossipd: note if loaded store seems reasonably up-to-date.

If not, we can ask peers for full gossip (for now we just set a flag).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

gossipd/gossip_store.c

@@ -509,7 +509,7 @@ int gossip_store_readonly_fd(struct gossip_store *gs)
 	return fd;
 }
 
-void gossip_store_load(struct routing_state *rstate, struct gossip_store *gs)
+bool gossip_store_load(struct routing_state *rstate, struct gossip_store *gs)
 {
 	struct gossip_hdr hdr;
 	u32 msglen, checksum;
@@ -519,6 +519,8 @@ void gossip_store_load(struct routing_state *rstate, struct gossip_store *gs)
 	size_t stats[] = {0, 0, 0, 0};
 	struct timeabs start = time_now();
 	const u8 *chan_ann = NULL;
+	bool contents_ok;
+	u32 last_timestamp = 0;
 	u64 chan_ann_off = 0; /* Spurious gcc-9 (Ubuntu 9-20190402-1ubuntu1) 9.0.1 20190402 (experimental) warning */
 
 	gs->writable = false;
@@ -571,6 +573,9 @@ void gossip_store_load(struct routing_state *rstate, struct gossip_store *gs)
 			/* Save for channel_amount (next msg) */
 			chan_ann = tal_steal(gs, msg);
 			chan_ann_off = gs->len;
+			/* If we have a channel_announcement, that's a reasonable
+			 * timestamp to use. */
+			last_timestamp = be32_to_cpu(hdr.timestamp);
 			break;
 		case WIRE_GOSSIP_STORE_PRIVATE_UPDATE:
 			if (!fromwire_gossip_store_private_update(tmpctx, msg, &msg)) {
@@ -610,6 +615,9 @@ void gossip_store_load(struct routing_state *rstate, struct gossip_store *gs)
 		gs->len += sizeof(hdr) + msglen;
 		clean_tmpctx();
 	}
+
+	/* If last timestamp is within 24 hours, say we're OK. */
+	contents_ok = (last_timestamp >= time_now().ts.tv_sec - 24*3600);
 	goto out;
 
 truncate:
@@ -623,6 +631,7 @@ truncate_nomsg:
 	if (ftruncate(gs->fd, gs->len) != 0)
 		status_failed(STATUS_FAIL_INTERNAL_ERROR,
 			      "Truncating store: %s", strerror(errno));
+	contents_ok = false;
 out:
 	gs->writable = true;
 	/* If we ever truncated, we might have a dangling channel_announce */
@@ -638,4 +647,6 @@ out:
 	status_trace("gossip_store: Read %zu/%zu/%zu/%zu cannounce/cupdate/nannounce/cdelete from store (%zu deleted) in %"PRIu64" bytes",
 		     stats[0], stats[1], stats[2], stats[3], gs->deleted,
 		     gs->len);
+
+	return contents_ok;
 }

gossipd/gossip_store.h

@@ -23,8 +23,10 @@ struct gossip_store *gossip_store_new(struct routing_state *rstate,
  *
  * @param rstate The routing state to load init.
  * @param gs  The `gossip_store` to read from
+ *
+ * Returns true if the store seems fully populated.
  */
-void gossip_store_load(struct routing_state *rstate, struct gossip_store *gs);
+bool gossip_store_load(struct routing_state *rstate, struct gossip_store *gs);
 
 /**
  * Add a private channel_update message to the gossip_store

gossipd/gossipd.c

@@ -113,6 +113,9 @@ struct daemon {
 
 	/* What addresses we can actually announce. */
 	struct wireaddr *announcable;
+
+	/* Do we think we're missing gossip? */
+	bool gossip_missing;
 };
 
 /* This represents each peer we're gossiping with */
@@ -1829,6 +1832,12 @@ static void gossip_disable_local_channels(struct daemon *daemon)
 		local_disable_chan(daemon->rstate, c);
 }
 
+/*~ We've found gossip is missing. */
+static void gossip_missing(struct daemon *daemon)
+{
+	daemon->gossip_missing = true;
+}
+
 /*~ Parse init message from lightningd: starts the daemon properly. */
 static struct io_plan *gossip_init(struct io_conn *conn,
 				   struct daemon *daemon,
@@ -1859,7 +1868,8 @@ static struct io_plan *gossip_init(struct io_conn *conn,
 					   dev_gossip_time);
 
 	/* Load stored gossip messages */
-	gossip_store_load(daemon->rstate, daemon->rstate->gs);
+	if (!gossip_store_load(daemon->rstate, daemon->rstate->gs))
+		gossip_missing(daemon);
 
 	/* Now disable all local channels, they can't be connected yet. */
 	gossip_disable_local_channels(daemon);
@@ -2807,6 +2817,7 @@ int main(int argc, char *argv[])
 
 	daemon = tal(NULL, struct daemon);
 	list_head_init(&daemon->peers);
+	daemon->gossip_missing = false;
 
 	/* Note the use of time_mono() here.  That's a monotonic clock, which
 	 * is really useful: it can only be used to measure relative events