gossipd: don't keep channel_announcement messages in memory.

MCP results from 5 runs, min-max(mean +/- stddev):
	store_load_msec:35107-37944(36686+/-1e+03)
	vsz_kb:1218036
	store_rewrite_sec:14.060000-17.970000(15.966+/-1.6)
	listnodes_sec:1.270000-1.350000(1.314+/-0.034)
	listchannels_sec:28.510000-30.270000(29.6+/-0.6)
	routing_sec:30.230000-31.510000(30.83+/-0.44)
	peer_write_all_sec:67.390000-70.710000(68.568+/-1.2)

MCP notable changes from previous patch (>1 stddev):
	-vsz_kb:1780516
	+vsz_kb:1218036

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

gossipd/gossip_store.c

@@ -174,7 +174,7 @@ static bool add_local_unnannounced(int fd,
 		const u8 *msg;
 
 		/* Ignore already announced. */
-		if (c->channel_announce)
+		if (is_chan_public(c))
 			continue;
 
 		msg = towire_gossipd_local_add_channel(tmpctx, &c->scid,

gossipd/gossipd.c

@@ -1112,7 +1112,7 @@ static void maybe_create_next_scid_reply(struct peer *peer)
 		if (!chan || !is_chan_public(chan))
 			continue;
 
-		queue_peer_msg(peer, chan->channel_announce);
+		queue_peer_from_store(peer, &chan->bcast);
 		if (chan->half[0].channel_update)
 			queue_peer_msg(peer, chan->half[0].channel_update);
 		if (chan->half[1].channel_update)

gossipd/routing.c

@@ -424,7 +424,6 @@ struct chan *new_chan(struct routing_state *rstate,
 	chan->nodes[n1idx] = n1;
 	chan->nodes[!n1idx] = n2;
 	chan->txout_script = NULL;
-	chan->channel_announce = NULL;
 	broadcastable_init(&chan->bcast);
 	chan->sat = satoshis;
 	chan->local_disabled = false;
@@ -917,14 +916,14 @@ static bool is_local_channel(const struct routing_state *rstate,
 
 static void add_channel_announce_to_broadcast(struct routing_state *rstate,
 					      struct chan *chan,
+					      const u8 *channel_announce,
 					      u32 timestamp,
 					      u32 index)
 {
 	chan->bcast.timestamp = timestamp;
 	/* 0, unless we're loading from store */
 	chan->bcast.index = index;
-	insert_broadcast(&rstate->broadcasts, chan->channel_announce,
-			 &chan->bcast);
+	insert_broadcast(&rstate->broadcasts, channel_announce, &chan->bcast);
 	rstate->local_channel_announced |= is_local_channel(rstate, chan);
 }
 
@@ -950,6 +949,9 @@ bool routing_add_channel_announcement(struct routing_state *rstate,
 	if (taken(msg))
 		tal_steal(tmpctx, msg);
 
+	if (taken(msg))
+		tal_steal(tmpctx, msg);
+
 	if (!fromwire_channel_announcement(
 		    tmpctx, msg, &node_signature_1, &node_signature_2,
 		    &bitcoin_signature_1, &bitcoin_signature_2, &features, &chain_hash,
@@ -1427,15 +1429,17 @@ bool routing_add_channel_update(struct routing_state *rstate,
 	 *     receiving the first corresponding `channel_update`.
 	 */
 	if (uc) {
-		chan->channel_announce = tal_steal(chan, uc->channel_announce);
-		add_channel_announce_to_broadcast(rstate, chan, timestamp,
+		add_channel_announce_to_broadcast(rstate, chan,
+						  uc->channel_announce,
+						  timestamp,
 						  uc->index);
-	} else if (!chan->channel_announce) {
+	} else if (!is_chan_public(chan)) {
 		/* For private channels, we get updates without an announce: don't
 		 * broadcast them!  But save local ones to store anyway. */
 		struct half_chan *hc = &chan->half[direction];
 		/* Don't save if we're loading from store */
-		if (is_local_channel(rstate, chan) && !index) {
+		assert(is_local_channel(rstate, chan));
+		if (!index) {
 			hc->bcast.index = gossip_store_add(rstate->broadcasts->gs,
 							   hc->channel_update);
 		} else

gossipd/routing.h

@@ -52,9 +52,6 @@ struct chan {
 	/* node[0].id < node[1].id */
 	struct node *nodes[2];
 
-	/* NULL if not announced yet (ie. not public). */
-	const u8 *channel_announce;
-
 	/* Timestamp and index into store file */
 	struct broadcastable bcast;