gossipd: use array[32] not pointer for alias.

And use ARRAY_SIZE() everywhere which will break compile if it's not a
literal array, plus assertions that it's the same length.

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

gossipd/gossipd.c

@@ -1,3 +1,4 @@
+#include <ccan/array_size/array_size.h>
 #include <ccan/asort/asort.h>
 #include <ccan/build_assert/build_assert.h>
 #include <ccan/cast/cast.h>
@@ -84,7 +85,7 @@ struct daemon {
 	/* Global features to list in node_announcement. */
 	u8 *globalfeatures;
 
-	u8 alias[33];
+	u8 alias[32];
 	u8 rgb[3];
 
 	/* What we can actually announce. */
@@ -1410,8 +1411,10 @@ static void append_node(const struct gossip_getnodes_entry ***nodes,
 	} else {
 		new->last_timestamp = n->last_timestamp;
 		new->addresses = n->addresses;
-		new->alias = n->alias;
-		memcpy(new->color, n->rgb_color, 3);
+		BUILD_ASSERT(ARRAY_SIZE(new->alias) == ARRAY_SIZE(n->alias));
+		BUILD_ASSERT(ARRAY_SIZE(new->color) == ARRAY_SIZE(n->rgb_color));
+		memcpy(new->alias, n->alias, ARRAY_SIZE(new->alias));
+		memcpy(new->color, n->rgb_color, ARRAY_SIZE(new->color));
 	}
 	*tal_arr_expand(nodes) = new;
 }

gossipd/routing.c

@@ -145,7 +145,6 @@ static struct node *new_node(struct routing_state *rstate,
 	n = tal(rstate, struct node);
 	n->id = *id;
 	n->chans = tal_arr(n, struct chan *, 0);
-	n->alias = NULL;
 	n->gfeatures = NULL;
 	n->node_announcement = NULL;
 	n->node_announcement_index = 0;
@@ -1306,9 +1305,8 @@ bool routing_add_node_announcement(struct routing_state *rstate, const u8 *msg T
 	node->addresses = tal_steal(node, wireaddrs);
 
 	node->last_timestamp = timestamp;
-	memcpy(node->rgb_color, rgb_color, 3);
-	tal_free(node->alias);
-	node->alias = tal_dup_arr(node, u8, alias, 32, 0);
+	memcpy(node->rgb_color, rgb_color, ARRAY_SIZE(node->rgb_color));
+	memcpy(node->alias, alias, ARRAY_SIZE(node->alias));
 	tal_free(node->gfeatures);
 	node->gfeatures = tal_steal(node, features);
 

gossipd/routing.h

@@ -110,8 +110,8 @@ struct node {
 		struct chan *prev;
 	} bfg[ROUTING_MAX_HOPS+1];
 
-	/* UTF-8 encoded alias as tal_arr, not zero terminated */
-	u8 *alias;
+	/* UTF-8 encoded alias, not zero terminated */
+	u8 alias[32];
 
 	/* Color to be used when displaying the name */
 	u8 rgb_color[3];

lightningd/gossip_control.c

@@ -202,7 +202,10 @@ static void json_getnodes_reply(struct subd *gossip UNUSED, const u8 *reply,
 			json_object_end(response);
 			continue;
 		}
-		esc = json_escape(NULL, (const char *)nodes[i]->alias);
+		esc = json_escape(NULL,
+				  take(tal_strndup(NULL,
+						   (const char *)nodes[i]->alias,
+						   ARRAY_SIZE(nodes[i]->alias))));
 		json_add_escaped_string(response, "alias", take(esc));
 		json_add_hex(response, "color",
 			     nodes[i]->color, ARRAY_SIZE(nodes[i]->color));

lightningd/gossip_msg.c

@@ -1,3 +1,4 @@
+#include <ccan/array_size/array_size.h>
 #include <common/bolt11.h>
 #include <common/wireaddr.h>
 #include <lightningd/gossip_msg.h>
@@ -20,7 +21,6 @@ struct gossip_getnodes_entry *fromwire_gossip_getnodes_entry(const tal_t *ctx,
 	entry->last_timestamp = fromwire_u64(pptr, max);
 	if (entry->last_timestamp < 0) {
 		entry->addresses = NULL;
-		entry->alias = NULL;
 		return entry;
 	}
 	numaddresses = fromwire_u8(pptr, max);
@@ -33,10 +33,8 @@ struct gossip_getnodes_entry *fromwire_gossip_getnodes_entry(const tal_t *ctx,
 			return NULL;
 		}
 	}
-	/* Make sure alias is NUL terminated */
-	entry->alias = tal_arrz(entry, u8, fromwire_u8(pptr, max)+1);
-	fromwire(pptr, max, entry->alias, tal_count(entry->alias)-1);
-	fromwire(pptr, max, entry->color, sizeof(entry->color));
+	fromwire(pptr, max, entry->alias, ARRAY_SIZE(entry->alias));
+	fromwire(pptr, max, entry->color, ARRAY_SIZE(entry->color));
 
 	return entry;
 }
@@ -58,9 +56,8 @@ void towire_gossip_getnodes_entry(u8 **pptr,
 	for (i=0; i<numaddresses; i++) {
 		towire_wireaddr(pptr, &entry->addresses[i]);
 	}
-	towire_u8(pptr, tal_count(entry->alias));
-	towire(pptr, entry->alias, tal_count(entry->alias));
-	towire(pptr, entry->color, sizeof(entry->color));
+	towire(pptr, entry->alias, ARRAY_SIZE(entry->alias));
+	towire(pptr, entry->color, ARRAY_SIZE(entry->color));
 }
 
 void fromwire_route_hop(const u8 **pptr, size_t *max, struct route_hop *entry)

lightningd/gossip_msg.h

@@ -16,7 +16,7 @@ struct gossip_getnodes_entry {
 	u8 *globalfeatures;
 	s64 last_timestamp; /* -1 means never: following fields ignored */
 	struct wireaddr *addresses;
-	u8 *alias;
+	u8 alias[32];
 	u8 color[3];
 };