gossipd: use u32 for timestamp.

We used an s64 so we could use -1 and save a check, but that's just
silly as we have adjacent non-u64 fields: wastes 7 bytes per node
and 16 per channel.

Interestingly, this seemed to make us a little slower for some reason.

MCP results from 5 runs, min-max(mean +/- stddev):
	store_load_msec:35569-38776(37169.8+/-1.2e+03)
	vsz_kb:2621808
	store_rewrite_sec:35.870000-40.290000(38.14+/-1.6)
	listnodes_sec:0.740000-0.800000(0.768+/-0.023)
	listchannels_sec:29.820000-32.730000(30.972+/-0.99)
	routing_sec:30.110000-30.590000(30.346+/-0.18)
	peer_write_all_sec:52.420000-59.160000(54.692+/-2.5)

MCP notable changes from previous patch (>1 stddev):
	-store_load_msec:32825-36365(34615.6+/-1.1e+03)
	+store_load_msec:35569-38776(37169.8+/-1.2e+03)
	-vsz_kb:2637488
	+vsz_kb:2621808
	-store_rewrite_sec:35.150000-36.200000(35.59+/-0.4)
	+store_rewrite_sec:35.870000-40.290000(38.14+/-1.6)
	-listnodes_sec:0.590000-0.710000(0.682+/-0.046)
	+listnodes_sec:0.740000-0.800000(0.768+/-0.023)
	-peer_write_all_sec:49.020000-52.890000(50.376+/-1.5)
	+peer_write_all_sec:52.420000-59.160000(54.692+/-2.5)

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

gossipd/gossipd.c

@@ -388,7 +388,6 @@ static void send_node_announcement(struct daemon *daemon)
 	u32 timestamp = time_now().ts.tv_sec;
 	secp256k1_ecdsa_signature sig;
 	u8 *msg, *nannounce, *err;
-	s64 last_timestamp;
 	struct node *self = get_node(daemon->rstate, &daemon->id);
 
 	/* BOLT #7:
@@ -397,14 +396,8 @@ static void send_node_announcement(struct daemon *daemon)
 	 *   - MUST set `timestamp` to be greater than that of any previous
 	 *   `node_announcement` it has previously created.
 	 */
-	if (self)
+	if (self && self->node_announcement && timestamp <= self->last_timestamp)
-		last_timestamp = self->last_timestamp;
+		timestamp = self->last_timestamp + 1;
-	else
-		/* last_timestamp is carefully a s64, so this works */
-		last_timestamp = -1;
-
-	if (timestamp <= last_timestamp)
-		timestamp = last_timestamp + 1;
 
 	/* Get an unsigned one. */
 	nannounce = create_node_announcement(tmpctx, daemon, NULL, timestamp);
@@ -438,7 +431,7 @@ static bool node_announcement_redundant(struct daemon *daemon)
 	if (!n)
 		return false;
 
-	if (n->last_timestamp == -1)
+	if (!n->node_announcement)
 		return false;
 
 	if (tal_count(n->addresses) != tal_count(daemon->announcable))
@@ -2062,10 +2055,12 @@ static void append_node(const struct gossip_getnodes_entry ***entries,
 
 	e = tal(*entries, struct gossip_getnodes_entry);
 	e->nodeid = n->id;
-	e->last_timestamp = n->last_timestamp;
 	/* Timestamp on wire is an unsigned 32 bit: we use a 64-bit signed, so
 	 * -1 means "we never received a channel_update". */
-	if (e->last_timestamp >= 0) {
+	if (!n->node_announcement)
+		e->last_timestamp = -1;
+	else {
+		e->last_timestamp = n->last_timestamp;
 		e->globalfeatures = n->globalfeatures;
 		e->addresses = n->addresses;
 		BUILD_ASSERT(ARRAY_SIZE(e->alias) == ARRAY_SIZE(n->alias));

gossipd/routing.c

@@ -231,7 +231,6 @@ static struct node *new_node(struct routing_state *rstate,
 	n->globalfeatures = NULL;
 	n->node_announcement = NULL;
 	n->node_announcement_index = 0;
-	n->last_timestamp = -1;
 	n->addresses = tal_arr(n, struct wireaddr, 0);
 	node_map_add(rstate->nodes, n);
 	tal_add_destructor2(n, destroy_node, rstate);
@@ -1193,7 +1192,7 @@ static void set_connection_values(struct chan *chan,
 				  u32 delay,
 				  u8 message_flags,
 				  u8 channel_flags,
-				  u64 timestamp,
+				  u32 timestamp,
 				  struct amount_msat htlc_minimum,
 				  struct amount_msat htlc_maximum)
 {
@@ -1658,7 +1657,7 @@ u8 *handle_node_announcement(struct routing_state *rstate, const u8 *node_ann)
 		return NULL;
 	}
 
-	if (node->last_timestamp >= timestamp) {
+	if (node->node_announcement && node->last_timestamp >= timestamp) {
 		SUPERVERBOSE("Ignoring node announcement, it's outdated.");
 		return NULL;
 	}
@@ -1853,6 +1852,8 @@ void route_prune(struct routing_state *rstate)
 		if (!is_chan_public(chan))
 			continue;
 
+		/* Rare case where we examine timestamp even without update;
+		 * it's used to prune channels where update never arrives */
 		if (chan->half[0].last_timestamp < highwater
 		    && chan->half[1].last_timestamp < highwater) {
 			status_trace(

gossipd/routing.h

@@ -25,8 +25,7 @@ struct half_chan {
 	/* Delay for HTLC in blocks.*/
 	u32 delay;
 
-	/* -1 if channel_update is NULL */
+	u32 last_timestamp;
-	s64 last_timestamp;
 
 	/* Minimum and maximum number of msatoshi in an HTLC */
 	struct amount_msat htlc_minimum, htlc_maximum;
@@ -114,8 +113,7 @@ HTABLE_DEFINE_TYPE(struct chan, chan_map_scid, hash_scid, chan_eq_scid, chan_map
 struct node {
 	struct node_id id;
 
-	/* -1 means never; other fields undefined */
+	u32 last_timestamp;
-	s64 last_timestamp;
 
 	/* IP/Hostname and port of this node (may be NULL) */
 	struct wireaddr *addresses;