gossipd: hand raw pubkeys in getnodes and getchannels entries.

We spend quite a bit of time in libsecp256k1 moving them to and from
DER encoding.  With a bit of care, we can transfer the raw bytes from
gossipd and manually decode them so a malformed one can't make us
abort().

Before:
	real	0m0.629000-0.695000(0.64985+/-0.019)s

After:
	real	0m0.359000-0.433000(0.37645+/-0.023)s

At this point, the main issues are 11% of time spent in ccan/io's
backend_wake (I tried using a hash table there, but that actually makes
the small-number-of-fds case slower), and 65% of gossipd's time is
in marshalling the response (all those tal_resize add up!).

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

gossipd/gossipd.c

@@ -1370,6 +1370,11 @@ static struct io_plan *getroute_req(struct io_conn *conn, struct daemon *daemon,
 	return daemon_conn_read_next(conn, &daemon->master);
 }
 
+#define raw_pubkey(arr, id)				\
+	do { BUILD_ASSERT(sizeof(arr) == sizeof(*id));	\
+		memcpy(arr, id, sizeof(*id));		\
+	} while(0)
+
 static void append_half_channel(struct gossip_getchannels_entry **entries,
 				const struct chan *chan,
 				int idx)
@@ -1382,8 +1387,8 @@ static void append_half_channel(struct gossip_getchannels_entry **entries,
 
 	e = tal_arr_expand(entries);
 
-	e->source = chan->nodes[idx]->id;
-	e->destination = chan->nodes[!idx]->id;
+	raw_pubkey(e->source, &chan->nodes[idx]->id);
+	raw_pubkey(e->destination, &chan->nodes[!idx]->id);
 	e->satoshis = chan->satoshis;
 	e->channel_flags = c->channel_flags;
 	e->message_flags = c->message_flags;
@@ -1442,7 +1447,7 @@ static void append_node(const struct gossip_getnodes_entry ***entries,
 
 	*tal_arr_expand(entries) = e
 		= tal(*entries, struct gossip_getnodes_entry);
-	e->nodeid = n->id;
+	raw_pubkey(e->nodeid, &n->id);
 	e->last_timestamp = n->last_timestamp;
 	if (e->last_timestamp < 0)
 		return;

lightningd/gossip_control.c

@@ -177,6 +177,24 @@ void gossipd_notify_spend(struct lightningd *ld,
 	subd_send_msg(ld->gossip, msg);
 }
 
+/* Gossipd shouldn't give us bad pubkeys, but don't abort if they do */
+static void json_add_raw_pubkey(struct json_result *response,
+			 const char *fieldname,
+			 const u8 raw_pubkey[sizeof(struct pubkey)])
+{
+	secp256k1_pubkey pubkey;
+	u8 der[PUBKEY_DER_LEN];
+	size_t outlen = PUBKEY_DER_LEN;
+
+	memcpy(&pubkey, raw_pubkey, sizeof(pubkey));
+	if (!secp256k1_ec_pubkey_serialize(secp256k1_ctx, der, &outlen,
+					   &pubkey,
+					   SECP256K1_EC_COMPRESSED))
+		json_add_string(response, fieldname, "INVALID PUBKEY");
+	else
+		json_add_hex(response, fieldname, der, sizeof(der));
+}
+
 static void json_getnodes_reply(struct subd *gossip UNUSED, const u8 *reply,
 				const int *fds UNUSED,
 				struct command *cmd)
@@ -198,7 +216,7 @@ static void json_getnodes_reply(struct subd *gossip UNUSED, const u8 *reply,
 		struct json_escaped *esc;
 
 		json_object_start(response, NULL);
-		json_add_pubkey(response, "nodeid", &nodes[i]->nodeid);
+		json_add_raw_pubkey(response, "nodeid", nodes[i]->nodeid);
 		if (nodes[i]->last_timestamp < 0) {
 			json_object_end(response);
 			continue;
@@ -349,9 +367,9 @@ static void json_listchannels_reply(struct subd *gossip UNUSED, const u8 *reply,
 	json_array_start(response, "channels");
 	for (i = 0; i < tal_count(entries); i++) {
 		json_object_start(response, NULL);
-		json_add_pubkey(response, "source", &entries[i].source);
-		json_add_pubkey(response, "destination",
-				&entries[i].destination);
+		json_add_raw_pubkey(response, "source", entries[i].source);
+		json_add_raw_pubkey(response, "destination",
+				    entries[i].destination);
 		json_add_string(response, "short_channel_id",
 				type_to_string(reply, struct short_channel_id,
 					       &entries[i].short_channel_id));

lightningd/gossip_msg.c

@@ -12,7 +12,7 @@ struct gossip_getnodes_entry *fromwire_gossip_getnodes_entry(const tal_t *ctx,
 	u16 flen;
 
 	entry = tal(ctx, struct gossip_getnodes_entry);
-	fromwire_pubkey(pptr, max, &entry->nodeid);
+	fromwire(pptr, max, entry->nodeid, sizeof(entry->nodeid));
 
 	entry->last_timestamp = fromwire_u64(pptr, max);
 	if (entry->last_timestamp < 0) {
@@ -43,7 +43,7 @@ struct gossip_getnodes_entry *fromwire_gossip_getnodes_entry(const tal_t *ctx,
 void towire_gossip_getnodes_entry(u8 **pptr,
 				  const struct gossip_getnodes_entry *entry)
 {
-	towire_pubkey(pptr, &entry->nodeid);
+	towire(pptr, entry->nodeid, sizeof(entry->nodeid));
 	towire_u64(pptr, entry->last_timestamp);
 
 	if (entry->last_timestamp < 0)
@@ -97,8 +97,8 @@ void fromwire_gossip_getchannels_entry(const u8 **pptr, size_t *max,
 				       struct gossip_getchannels_entry *entry)
 {
 	fromwire_short_channel_id(pptr, max, &entry->short_channel_id);
-	fromwire_pubkey(pptr, max, &entry->source);
-	fromwire_pubkey(pptr, max, &entry->destination);
+	fromwire(pptr, max, entry->source, sizeof(entry->source));
+	fromwire(pptr, max, entry->destination, sizeof(entry->destination));
 	entry->satoshis = fromwire_u64(pptr, max);
 	entry->message_flags = fromwire_u8(pptr, max);
 	entry->channel_flags = fromwire_u8(pptr, max);
@@ -114,8 +114,8 @@ void towire_gossip_getchannels_entry(u8 **pptr,
 				     const struct gossip_getchannels_entry *entry)
 {
 	towire_short_channel_id(pptr, &entry->short_channel_id);
-	towire_pubkey(pptr, &entry->source);
-	towire_pubkey(pptr, &entry->destination);
+	towire(pptr, entry->source, sizeof(entry->source));
+	towire(pptr, entry->destination, sizeof(entry->destination));
 	towire_u64(pptr, entry->satoshis);
 	towire_u8(pptr, entry->message_flags);
 	towire_u8(pptr, entry->channel_flags);

lightningd/gossip_msg.h

@@ -12,7 +12,8 @@ struct peer_features {
 };
 
 struct gossip_getnodes_entry {
-	struct pubkey nodeid;
+	/* This is raw to optimize marshaling: be careful! */
+	u8 nodeid[sizeof(struct pubkey)];
 	s64 last_timestamp; /* -1 means never: following fields ignored */
 	u8 *globalfeatures;
 	struct wireaddr *addresses;
@@ -21,7 +22,8 @@ struct gossip_getnodes_entry {
 };
 
 struct gossip_getchannels_entry {
-	struct pubkey source, destination;
+	/* These are raw to optimize marshaling: be careful! */
+	u8 source[sizeof(struct pubkey)], destination[sizeof(struct pubkey)];
 	u64 satoshis;
 	struct short_channel_id short_channel_id;
 	u8 message_flags;