Function prune_network

gossipd/gossmap_manage.c:409–471

Every half a week we look for dead channels (faster in dev) */

/* Every half a week we look for dead channels (faster in dev) */
static void prune_network(struct gossmap_manage *gm)
{
	u64 now = clock_time().ts.tv_sec;
	/* Anything below this highwater mark ought to be pruned */
	const s64 highwater = now - GOSSIP_PRUNE_INTERVAL(gm->daemon->dev_fast_gossip_prune);
	const struct gossmap_node *me;
	struct gossmap *gossmap;

	/* We reload this every time we delete a channel: that way we can tell if it's
	 * time to remove a node! */
	gossmap = gossmap_manage_get_gossmap(gm);
	me = gossmap_find_node(gossmap, &gm->daemon->id);

	/* Now iterate through all channels and see if it is still alive */
	for (size_t i = 0; i < gossmap_max_chan_idx(gossmap); i++) {
		struct gossmap_chan *chan = gossmap_chan_byidx(gossmap, i);
		u32 timestamp[2];
		struct short_channel_id scid;

		if (!chan)
			continue;

		/* BOLT #7:
		 * - if the `timestamp` of the latest `channel_update` in
		 *   either direction is older than two weeks (1209600 seconds):
		 *    - MAY prune the channel.
		 */
		/* This is a fancy way of saying "both ends must refresh!" */
		timestamp[0] = get_timestamp(gossmap, chan, 0);
		timestamp[1] = get_timestamp(gossmap, chan, 1);

		if (timestamp[0] >= highwater && timestamp[1] >= highwater)
			continue;

		scid = gossmap_chan_scid(gossmap, chan);

		/* If it's dying anyway, don't bother pruning. */
		if (channel_already_dying(gm->dying_channels, scid))
			continue;

		/* Is it one of mine? */
		if (gossmap_nth_node(gossmap, chan, 0) == me
		    || gossmap_nth_node(gossmap, chan, 1) == me) {
			int local = (gossmap_nth_node(gossmap, chan, 1) == me);
			status_unusual("Pruning local channel %s from gossip_store: local channel_update time %u, remote %u",
				       fmt_short_channel_id(tmpctx, scid),
				       timestamp[local], timestamp[!local]);
		}

		status_debug("Pruning channel %s from network view (ages %u and %u)",
			     fmt_short_channel_id(tmpctx, scid),
			     timestamp[0], timestamp[1]);

		remove_channel(gm, gossmap, chan, scid);

		gossmap = gossmap_manage_get_gossmap(gm);
		me = gossmap_find_node(gossmap, &gm->daemon->id);
	}