pong: embed version string into ping replies if DEVELOPER=1.

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

channeld/channel.c

@@ -1514,22 +1514,13 @@ static void handle_peer_fail_malformed_htlc(struct peer *peer, const u8 *msg)
 
 static void handle_pong(struct peer *peer, const u8 *pong)
 {
-	u8 *ignored;
-
-	status_trace("Got pong!");
-	if (!fromwire_pong(pong, pong, &ignored))
-		peer_failed(&peer->cs,
-			    peer->gossip_index,
-			    &peer->channel_id,
-			    "Bad pong %s", tal_hex(pong, pong));
-
-	if (!peer->num_pings_outstanding)
+	const char *err = got_pong(pong, &peer->num_pings_outstanding);
+	if (err)
 		peer_failed(&peer->cs,
 			    peer->gossip_index,
 			    &peer->channel_id,
-			    "Unexpected pong");
+			    "%s", err);
 
-	peer->num_pings_outstanding--;
 	wire_sync_write(MASTER_FD,
 			take(towire_channel_ping_reply(pong, tal_len(pong))));
 }

common/ping.c

@@ -1,4 +1,6 @@
 #include <common/ping.h>
+#include <common/status.h>
+#include <common/version.h>
 #include <wire/gen_peer_wire.h>
 
 bool check_ping_make_pong(const tal_t *ctx, const u8 *ping, u8 **pong)
@@ -31,6 +33,10 @@ bool check_ping_make_pong(const tal_t *ctx, const u8 *ping, u8 **pong)
 		 * as secrets, or portions of initialized memory.
 		*/
 		ignored = tal_arrz(ctx, u8, num_pong_bytes);
+#if DEVELOPER
+		/* Embed version */
+		strncpy((char *)ignored, version(), num_pong_bytes);
+#endif
 		*pong = towire_pong(ctx, ignored);
 		tal_free(ignored);
 	} else
@@ -53,3 +59,25 @@ u8 *make_ping(const tal_t *ctx, u16 num_pong_bytes, u16 padlen)
 	tal_free(ignored);
 	return ping;
 }
+
+const char *got_pong(const u8 *pong, size_t *num_pings_outstanding)
+{
+	u8 *ignored;
+	int i;
+
+	if (!fromwire_pong(pong, pong, &ignored))
+		return "Bad pong";
+
+	if (*num_pings_outstanding == 0)
+		return "Unexpected pong";
+
+	for (i = 0; i < tal_len(ignored); i++) {
+		if (ignored[i] < ' ' || ignored[i] == 127)
+			break;
+	}
+	status_trace("Got pong %zu bytes (%.*s...)",
+		     tal_len(ignored), i, (char *)ignored);
+
+	(*num_pings_outstanding)--;
+	return NULL;
+}

common/ping.h

@@ -10,4 +10,7 @@ bool check_ping_make_pong(const tal_t *ctx, const u8 *ping, u8 **pong);
 /* Make a ping packet requesting num_pong_bytes */
 u8 *make_ping(const tal_t *ctx, u16 num_pong_bytes, u16 padlen);
 
+/* Returns error string if something wrong. */
+const char *got_pong(const u8 *pong, size_t *num_pings_outstanding);
+
 #endif /* LIGHTNING_COMMON_PING_H */

gossipd/gossip.c

@@ -502,20 +502,13 @@ static void handle_ping(struct peer *peer, u8 *ping)
 
 static void handle_pong(struct peer *peer, const u8 *pong)
 {
-	u8 *ignored;
+	const char *err = got_pong(pong, &peer->local->num_pings_outstanding);
 
-	status_trace("Got pong!");
-	if (!fromwire_pong(pong, pong, &ignored)) {
-		peer_error(peer, "Bad pong");
+	if (err) {
+		peer_error(peer, "%s", err);
 		return;
 	}
 
-	if (!peer->local->num_pings_outstanding) {
-		peer_error(peer, "Unexpected pong");
-		return;
-	}
-
-	peer->local->num_pings_outstanding--;
 	daemon_conn_send(&peer->daemon->master,
 			 take(towire_gossip_ping_reply(pong, true,
 						       tal_len(pong))));

tests/test_lightningd.py

@@ -1863,11 +1863,17 @@ class LightningDTests(BaseLightningDTests):
 
         # Test gossip pinging.
         self.ping_tests(l1, l2)
+        if DEVELOPER:
+            l1.daemon.wait_for_log('Got pong 1000 bytes \({}\.\.\.\)'
+                                   .format(l2.info['version']), timeout=1)
 
         self.fund_channel(l1, l2, 10**5)
 
         # channeld pinging
         self.ping_tests(l1, l2)
+        if DEVELOPER:
+            l1.daemon.wait_for_log('Got pong 1000 bytes \({}\.\.\.\)'
+                                   .format(l2.info['version']))
 
     @unittest.skipIf(not DEVELOPER, "needs DEVELOPER=1")
     def test_routing_gossip_reconnect(self):