ping: complete JSON RPC ping commands even if one ping gets no response.

We would never complete further ping commands if we had < responses
than pings.  Oops.

Fixes: #1928
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

gossipd/gossip_wire.csv

@@ -52,6 +52,7 @@ gossip_ping,,num_pong_bytes,u16
 gossip_ping,,len,u16
 
 gossip_ping_reply,3108
+gossip_ping_reply,,id,struct pubkey
 # False if id in gossip_ping was unknown.
 gossip_ping_reply,,sent,bool
 # 0 == no pong expected

gossipd/gossipd.c

@@ -648,7 +648,7 @@ static void handle_pong(struct peer *peer, const u8 *pong)
 	}
 
 	daemon_conn_send(&peer->daemon->master,
-			 take(towire_gossip_ping_reply(NULL, true,
+			 take(towire_gossip_ping_reply(NULL, &peer->id, true,
 						       tal_count(pong))));
 }
 
@@ -1557,7 +1557,8 @@ static struct io_plan *ping_req(struct io_conn *conn, struct daemon *daemon,
 	peer = find_peer(daemon, &id);
 	if (!peer) {
 		daemon_conn_send(&daemon->master,
-				 take(towire_gossip_ping_reply(NULL, false, 0)));
+				 take(towire_gossip_ping_reply(NULL, &id,
+							       false, 0)));
 		goto out;
 	}
 
@@ -1581,7 +1582,8 @@ static struct io_plan *ping_req(struct io_conn *conn, struct daemon *daemon,
 	 */
 	if (num_pong_bytes >= 65532)
 		daemon_conn_send(&daemon->master,
-				 take(towire_gossip_ping_reply(NULL, true, 0)));
+				 take(towire_gossip_ping_reply(NULL, &id,
+							       true, 0)));
 	else
 		peer->num_pings_outstanding++;
 

lightningd/Makefile

@@ -75,12 +75,12 @@ LIGHTNINGD_SRC :=				\
 	lightningd/payalgo.c			\
 	lightningd/peer_control.c		\
 	lightningd/peer_htlcs.c			\
+	lightningd/ping.c			\
 	lightningd/subd.c			\
 	lightningd/watch.c
 
 # Source files without corresponding headers
 LIGHTNINGD_SRC_NOHDR :=				\
-	lightningd/ping.c			\
 	lightningd/memdump.c
 
 LIGHTNINGD_OBJS := $(LIGHTNINGD_SRC:.c=.o) $(LIGHTNINGD_SRC_NOHDR:.c=.o)

lightningd/gossip_control.c

@@ -27,6 +27,7 @@
 #include <lightningd/jsonrpc_errors.h>
 #include <lightningd/log.h>
 #include <lightningd/param.h>
+#include <lightningd/ping.h>
 #include <sodium/randombytes.h>
 #include <string.h>
 #include <wire/gen_peer_wire.h>
@@ -121,7 +122,6 @@ static unsigned gossip_msg(struct subd *gossip, const u8 *msg, const int *fds)
 	case WIRE_GOSSIP_GETNODES_REPLY:
 	case WIRE_GOSSIP_GETROUTE_REPLY:
 	case WIRE_GOSSIP_GETCHANNELS_REPLY:
-	case WIRE_GOSSIP_PING_REPLY:
 	case WIRE_GOSSIP_SCIDS_REPLY:
 	case WIRE_GOSSIP_QUERY_CHANNEL_RANGE_REPLY:
 	case WIRE_GOSSIP_RESOLVE_CHANNEL_REPLY:
@@ -131,6 +131,10 @@ static unsigned gossip_msg(struct subd *gossip, const u8 *msg, const int *fds)
 	case WIRE_GOSSIP_LOCAL_CHANNEL_CLOSE:
 		break;
 
+	case WIRE_GOSSIP_PING_REPLY:
+		ping_reply(gossip, msg);
+		break;
+
 	case WIRE_GOSSIP_GET_TXOUT:
 		get_txout(gossip, msg);
 		break;

lightningd/lightningd.c

@@ -176,6 +176,7 @@ static struct lightningd *new_lightningd(const tal_t *ctx)
 	list_head_init(&ld->waitsendpay_commands);
 	list_head_init(&ld->sendpay_commands);
 	list_head_init(&ld->close_commands);
+	list_head_init(&ld->ping_commands);
 
 	/*~ Tal also explicitly supports arrays: it stores the number of
 	 * elements, which can be accessed with tal_count() (or tal_bytelen()

lightningd/lightningd.h

@@ -162,6 +162,8 @@ struct lightningd {
 	struct list_head sendpay_commands;
 	/* Outstanding close commands. */
 	struct list_head close_commands;
+	/* Outstanding ping commands. */
+	struct list_head ping_commands;
 
 	/* Maintained by invoices.c */
 	struct invoices *invoices;

lightningd/ping.c

@@ -10,28 +10,71 @@
 #include <lightningd/log.h>
 #include <lightningd/param.h>
 #include <lightningd/peer_control.h>
+#include <lightningd/ping.h>
 #include <lightningd/subd.h>
 
-static void ping_reply(struct subd *subd, const u8 *msg, const int *fds UNUSED,
-		       struct command *cmd)
+struct ping_command {
+	struct list_node list;
+	struct pubkey id;
+	struct command *cmd;
+};
+
+static struct ping_command *find_ping_cmd(struct lightningd *ld,
+					  const struct pubkey *id)
+{
+	struct ping_command *i;
+
+	list_for_each(&ld->ping_commands, i, list) {
+		if (pubkey_eq(id, &i->id))
+			return i;
+	}
+	return NULL;
+}
+
+static void destroy_ping_command(struct ping_command *pc)
+{
+	list_del(&pc->list);
+}
+
+static struct ping_command *new_ping_command(const tal_t *ctx,
+					     struct lightningd *ld,
+					     const struct pubkey *peer_id,
+					     struct command *cmd)
+{
+	struct ping_command *pc = tal(ctx, struct ping_command);
+
+	pc->id = *peer_id;
+	pc->cmd = cmd;
+	list_add_tail(&ld->ping_commands, &pc->list);
+	tal_add_destructor(pc, destroy_ping_command);
+
+	return pc;
+}
+
+void ping_reply(struct subd *subd, const u8 *msg)
 {
 	u16 totlen;
 	bool ok, sent = true;
+	struct pubkey id;
+	struct ping_command *pc;
 
 	log_debug(subd->ld->log, "Got ping reply!");
-	ok = fromwire_gossip_ping_reply(msg, &sent, &totlen);
+	ok = fromwire_gossip_ping_reply(msg, &id, &sent, &totlen);
+
+	pc = find_ping_cmd(subd->ld, &id);
+	assert(pc);
 
 	if (!ok)
-		command_fail(cmd, LIGHTNINGD, "Bad reply message");
+		command_fail(pc->cmd, LIGHTNINGD, "Bad reply message");
 	else if (!sent)
-		command_fail(cmd, LIGHTNINGD, "Unknown peer");
+		command_fail(pc->cmd, LIGHTNINGD, "Unknown peer");
 	else {
-		struct json_result *response = new_json_result(cmd);
+		struct json_result *response = new_json_result(pc->cmd);
 
 		json_object_start(response, NULL);
 		json_add_num(response, "totlen", totlen);
 		json_object_end(response);
-		command_success(cmd, response);
+		command_success(pc->cmd, response);
 	}
 }
 
@@ -76,10 +119,12 @@ static void json_ping(struct command *cmd,
 		return;
 	}
 
+	/* parent is cmd, so when we complete cmd, we free this. */
+	new_ping_command(cmd, cmd->ld, id, cmd);
+
 	/* gossipd handles all pinging, even if it's in another daemon. */
 	msg = towire_gossip_ping(NULL, id, *pongbytes, *len);
-	subd_req(cmd->ld->gossip, cmd->ld->gossip,
-		 take(msg), -1, 0, ping_reply, cmd);
+	subd_send_msg(cmd->ld->gossip, take(msg));
 	command_still_pending(cmd);
 }
 

lightningd/ping.h

@@ -0,0 +1,9 @@
+#ifndef LIGHTNING_LIGHTNINGD_PING_H
+#define LIGHTNING_LIGHTNINGD_PING_H
+#include "config.h"
+#include <ccan/short_types/short_types.h>
+
+struct subd;
+void ping_reply(struct subd *subd, const u8 *msg);
+
+#endif /* LIGHTNING_LIGHTNINGD_PING_H */