gossipd: don't keep channel_updates in memory.

This requires some trickiness when we want to re-add unannounced channels
to the store after compaction, so we extract a common "copy_message" to
transfer from old store to new.

MCP results from 5 runs, min-max(mean +/- stddev):
	store_load_msec:36034-37853(37109.8+/-5.9e+02)
	vsz_kb:577456
	store_rewrite_sec:12.490000-13.250000(12.862+/-0.27)
	listnodes_sec:1.250000-1.480000(1.364+/-0.09)
	listchannels_sec:30.820000-31.480000(31.068+/-0.24)
	routing_sec:26.940000-27.990000(27.616+/-0.39)
	peer_write_all_sec:65.690000-68.600000(66.698+/-0.99)

MCP notable changes from previous patch (>1 stddev):
	-vsz_kb:1202316
	+vsz_kb:577456

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

gossipd/gossip_store.c

@@ -158,13 +158,56 @@ static bool gossip_store_append(int fd,
 		write(fd, msg, msglen) == msglen);
 }
 
+/* Copy a whole message from one gossip_store to another.  Returns
+ * total msg length including header, or 0 on error. */
+static size_t copy_message(int in_fd, int out_fd, unsigned offset)
+{
+	beint32_t belen, becsum;
+	u32 msglen;
+	u8 *msg;
+
+	/* FIXME: optimize both read and allocation */
+	if (lseek(in_fd, offset, SEEK_SET) < 0
+	    || read(in_fd, &belen, sizeof(belen)) != sizeof(belen)
+	    || read(in_fd, &becsum, sizeof(becsum)) != sizeof(becsum)) {
+		status_broken("Failed reading header from to gossip store @%u"
+			      ": %s",
+			      offset, strerror(errno));
+		return 0;
+	}
+
+	msglen = be32_to_cpu(belen);
+	msg = tal_arr(NULL, u8, sizeof(belen) + sizeof(becsum) + msglen);
+	memcpy(msg, &belen, sizeof(belen));
+	memcpy(msg + sizeof(belen), &becsum, sizeof(becsum));
+	if (read(in_fd, msg + sizeof(belen) + sizeof(becsum), msglen)
+	    != msglen) {
+		status_broken("Failed reading %u from to gossip store @%u"
+			      ": %s",
+			      msglen, offset, strerror(errno));
+		tal_free(msg);
+		return 0;
+	}
+
+	if (write(out_fd, msg, msglen + sizeof(belen) + sizeof(becsum))
+	    != msglen + sizeof(belen) + sizeof(becsum)) {
+		status_broken("Failed writing to gossip store: %s",
+			      strerror(errno));
+		tal_free(msg);
+		return 0;
+	}
+
+	tal_free(msg);
+	return msglen + sizeof(belen) + sizeof(becsum);
+}
+
 /* Local unannounced channels don't appear in broadcast map, but we need to
  * remember them anyway, so we manually append to the store.
  *
  * Note these do *not* add to gs->count, since that's compared with
  * the broadcast map count.
 */
-static bool add_local_unnannounced(int fd,
+static bool add_local_unnannounced(int in_fd, int out_fd,
 				   struct routing_state *rstate,
 				   struct node *self,
 				   u64 *len)
@@ -182,18 +225,23 @@ static bool add_local_unnannounced(int fd,
 
 		msg = towire_gossipd_local_add_channel(tmpctx, &c->scid,
 						       &peer->id, c->sat);
-		if (!gossip_store_append(fd, rstate, msg, len))
+		if (!gossip_store_append(out_fd, rstate, msg, len))
 			return false;
 
 		for (size_t i = 0; i < 2; i++) {
-			u32 idx;
+			size_t len_with_header;
-			msg = c->half[i].channel_update;
+
-			if (!msg)
+			if (!is_halfchan_defined(&c->half[i]))
 				continue;
-			idx = *len;
+
-			if (!gossip_store_append(fd, rstate, msg, len))
+			len_with_header = copy_message(in_fd, out_fd,
+						       c->half[i].bcast.index);
+			if (!len_with_header)
 				return false;
-			c->half[i].bcast.index = idx;
+
+			c->half[i].bcast.index = *len;
+
+			*len += len_with_header;
 		}
 	}
 
@@ -283,7 +331,7 @@ bool gossip_store_compact(struct gossip_store *gs,
 
 	/* Local unannounced channels are not in the store! */
 	self = get_node(gs->rstate, &gs->rstate->local_id);
-	if (self && !add_local_unnannounced(fd, gs->rstate, self,
+	if (self && !add_local_unnannounced(gs->fd, fd, gs->rstate, self,
 					    &len)) {
 		status_broken("Failed writing unannounced to gossip store: %s",
 			      strerror(errno));

gossipd/gossipd.c

@@ -1113,10 +1113,10 @@ static void maybe_create_next_scid_reply(struct peer *peer)
 			continue;
 
 		queue_peer_from_store(peer, &chan->bcast);
-		if (chan->half[0].channel_update)
+		if (is_halfchan_defined(&chan->half[0]))
-			queue_peer_msg(peer, chan->half[0].channel_update);
+			queue_peer_from_store(peer, &chan->half[0].bcast);
-		if (chan->half[1].channel_update)
+		if (is_halfchan_defined(&chan->half[1]))
-			queue_peer_msg(peer, chan->half[1].channel_update);
+			queue_peer_from_store(peer, &chan->half[1].bcast);
 
 		/* Record node ids for later transmission of node_announcement */
 		tal_arr_expand(&peer->scid_query_nodes, chan->nodes[0]->id);
@@ -1374,7 +1374,7 @@ static void maybe_update_local_channel(struct daemon *daemon,
 	bool local_disabled;
 
 	/* Don't generate a channel_update for an uninitialized channel. */
-	if (!hc->channel_update)
+	if (!is_halfchan_defined(hc))
 		return;
 
 	/* Nothing to update? */
@@ -1455,9 +1455,13 @@ static bool handle_get_update(struct peer *peer, const u8 *msg)
 	/* Since we're going to send it out, make sure it's up-to-date. */
 	maybe_update_local_channel(peer->daemon, chan, direction);
 
-	/* It's possible this is NULL, if we've never sent a channel_update
+ 	/* It's possible this is zero, if we've never sent a channel_update
 	 * for that channel. */
-	update = chan->half[direction].channel_update;
+	if (!is_halfchan_defined(&chan->half[direction]))
+		update = NULL;
+	else
+		update = gossip_store_get(tmpctx, rstate->broadcasts->gs,
+					  chan->half[direction].bcast.index);
 out:
 	status_trace("peer %s schanid %s: %s update",
 		     type_to_string(tmpctx, struct node_id, &peer->id),

gossipd/routing.c

@@ -386,8 +386,6 @@ static void init_half_chan(struct routing_state *rstate,
 {
 	struct half_chan *c = &chan->half[channel_idx];
 
-	c->channel_update = NULL;
-
 	/* Set the channel direction */
 	c->channel_flags = channel_idx;
 	// TODO: wireup message_flags
@@ -971,11 +969,17 @@ bool routing_add_channel_announcement(struct routing_state *rstate,
 	 * add fresh ones.  But if we're loading off disk right now, we can't
 	 * do that. */
 	if (chan && index == 0) {
-		/* Steal any private updates */
+		/* Reload any private updates */
-		private_updates[0]
+		if (chan->half[0].bcast.index)
-			= tal_steal(NULL, chan->half[0].channel_update);
+			private_updates[0]
-		private_updates[1]
+				= gossip_store_get(NULL,
-			= tal_steal(NULL, chan->half[1].channel_update);
+						   rstate->broadcasts->gs,
+						   chan->half[0].bcast.index);
+		if (chan->half[1].bcast.index)
+			private_updates[1]
+				= gossip_store_get(NULL,
+						   rstate->broadcasts->gs,
+						   chan->half[1].bcast.index);
 	}
 
 	/* Pretend it didn't exist, for the moment. */
@@ -1330,6 +1334,10 @@ bool routing_add_channel_update(struct routing_state *rstate,
 	if (taken(update))
 		tal_steal(tmpctx, update);
 
+	/* In case it's free in a failure path */
+	if (taken(update))
+		tal_steal(tmpctx, update);
+
 	if (!fromwire_channel_update(update, &signature, &chain_hash,
 				     &short_channel_id, &timestamp,
 				     &message_flags, &channel_flags,
@@ -1388,18 +1396,6 @@ bool routing_add_channel_update(struct routing_state *rstate,
 	/* Discard older updates */
 	hc = &chan->half[direction];
 	if (is_halfchan_defined(hc) && timestamp <= hc->bcast.timestamp) {
-		/* They're not supposed to do this! */
-		if (timestamp == hc->bcast.timestamp
-		    && !memeq(hc->channel_update, tal_count(hc->channel_update),
-			      update, tal_count(update))) {
-			status_debug("Bad gossip repeated timestamp for %s(%u): %s then %s",
-				       type_to_string(tmpctx,
-						      struct short_channel_id,
-						      &short_channel_id),
-				       channel_flags,
-				       tal_hex(tmpctx, hc->channel_update),
-				       tal_hex(tmpctx, update));
-		}
 		SUPERVERBOSE("Ignoring outdated update.");
 		/* Ignoring != failing */
 		return true;
@@ -1416,15 +1412,9 @@ bool routing_add_channel_update(struct routing_state *rstate,
 			      message_flags, channel_flags,
 			      timestamp, htlc_minimum, htlc_maximum);
 
-	/* Replace any old one. */
-	tal_free(chan->half[direction].channel_update);
 	/* Safe even if was never added */
 	broadcast_del(rstate->broadcasts, &chan->half[direction].bcast);
 
-	chan->half[direction].channel_update
-		= tal_dup_arr(chan, u8, update, tal_count(update), 0);
-
-
 	/* BOLT #7:
 	 *   - MUST consider the `timestamp` of the `channel_announcement` to be
 	 *     the `timestamp` of a corresponding `channel_update`.
@@ -1444,7 +1434,7 @@ bool routing_add_channel_update(struct routing_state *rstate,
 		assert(is_local_channel(rstate, chan));
 		if (!index) {
 			hc->bcast.index = gossip_store_add(rstate->broadcasts->gs,
-							   hc->channel_update);
+							   update);
 		} else
 			hc->bcast.index = index;
 		return true;
@@ -1454,7 +1444,7 @@ bool routing_add_channel_update(struct routing_state *rstate,
 	chan->half[direction].bcast.index = index;
 
 	insert_broadcast(&rstate->broadcasts,
-			 chan->half[direction].channel_update,
+			 update,
 			 &chan->half[direction].bcast);
 
 	if (uc) {

gossipd/routing.h

@@ -14,9 +14,6 @@
 #include <wire/wire.h>
 
 struct half_chan {
-	/* Cached `channel_update` which initialized below (or NULL) */
-	const u8 *channel_update;
-
 	/* millisatoshi. */
 	u32 base_fee;
 	/* millionths */
@@ -66,7 +63,7 @@ static inline bool is_chan_public(const struct chan *chan)
 
 static inline bool is_halfchan_defined(const struct half_chan *hc)
 {
-	return hc->channel_update != NULL;
+	return hc->bcast.index != 0;
 }
 
 static inline bool is_halfchan_enabled(const struct half_chan *hc)

gossipd/test/run-bench-find_route.c

@@ -137,8 +137,8 @@ static void add_connection(struct routing_state *rstate,
 	c->proportional_fee = proportional_fee;
 	c->delay = delay;
 	c->channel_flags = node_id_idx(&nodes[from], &nodes[to]);
-	/* This must be non-NULL, otherwise we consider it disabled! */
+	/* This must be non-zero, otherwise we consider it disabled! */
-	c->channel_update = tal(chan, u8);
+	c->bcast.index = 1;
 	c->htlc_maximum = AMOUNT_MSAT(-1ULL);
 	c->htlc_minimum = AMOUNT_MSAT(0);
 }

gossipd/test/run-find_route-specific.c

@@ -120,8 +120,8 @@ get_or_make_connection(struct routing_state *rstate,
 	if (!chan)
 		chan = new_chan(rstate, &scid, from_id, to_id, satoshis);
 
-	/* Make sure it's seen as initialized (update non-NULL). */
+	/* Make sure it's seen as initialized (index non-zero). */
-	chan->half[idx].channel_update = (void *)chan;
+	chan->half[idx].bcast.index = 1;
 	chan->half[idx].htlc_minimum = AMOUNT_MSAT(0);
 	if (!amount_sat_to_msat(&chan->half[idx].htlc_maximum, satoshis))
 		abort();

gossipd/test/run-find_route.c

@@ -126,8 +126,8 @@ static void add_connection(struct routing_state *rstate,
 		chan = new_chan(rstate, &scid, from, to, satoshis);
 
 	c = &chan->half[node_id_idx(from, to)];
-	/* Make sure it's seen as initialized (update non-NULL). */
+	/* Make sure it's seen as initialized (index non-zero). */
-	c->channel_update = (void *)c;
+	c->bcast.index = 1;
 	c->base_fee = base_fee;
 	c->proportional_fee = proportional_fee;
 	c->delay = delay;