dns: add failure callback.

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

daemon/dns.c

@@ -16,11 +16,13 @@
 #include <sys/wait.h>
 
 struct dns_async {
+	size_t use;
 	struct lightningd_state *state;
-	struct io_plan *(*init)(struct io_conn *,
-				struct lightningd_state *,
-				const char *name, const char *port);
-	const char *name, *port;
+	struct io_plan *(*init)(struct io_conn *, struct lightningd_state *,
+				void *);
+	void (*fail)(struct lightningd_state *, void *arg);
+	const char *name;
+	void *arg;
 	int pid;
 	size_t num_addresses;
 	struct netaddr *addresses;
@@ -67,7 +69,9 @@ static struct io_plan *connected(struct io_conn *conn, struct dns_async *d)
 {
 	/* No longer need to try more connections. */
 	io_set_finish(conn, NULL, NULL);
-	return d->init(conn, d->state, d->name, d->port);
+
+	/* Keep use count, so reap_child won't fail. */
+	return d->init(conn, d->state, d->arg);
 }
 
 static void try_connect_one(struct dns_async *d);
@@ -104,25 +108,32 @@ static void try_connect_one(struct dns_async *d)
 		/* Now we can warn if it's overlength */
 		if (a->addrlen > sizeof(a->saddr)) {
 			log_broken(d->state->base_log,
-				   "DNS lookup gave overlength address for %s:%s"
+				   "DNS lookup gave overlength address for %s"
 				   " for family %u, len=%u",
-				   d->name, d->port,
-				   a->saddr.s.sa_family, a->addrlen);
+				   d->name, a->saddr.s.sa_family, a->addrlen);
 		} else {
 			/* Might not even be able to create eg. IPv6 sockets */
 			fd = socket(a->saddr.s.sa_family, a->type, a->protocol);
 			if (fd >= 0) {
 				io_new_conn(d->state, fd, init_conn, d);
-				break;
+				return;
 			}
 		}
 	}
+
+	/* We're out of things to try.  Fail. */
+	if (--d->use == 0)
+		d->fail(d->state, d->arg);
 }
 
 static struct io_plan *start_connecting(struct io_conn *conn,
 					struct dns_async *d)
 {
 	assert(d->num_addresses);
+
+	/* reap_child and our connections can race: only last one should call
+	 * fail. */
+	d->use++;
 	try_connect_one(d);
 	return io_close(conn);
 }
@@ -144,13 +155,18 @@ static struct io_plan *init_dns_conn(struct io_conn *conn, struct dns_async *d)
 static void reap_child(struct io_conn *conn, struct dns_async *d)
 {
 	waitpid(d->pid, NULL, 0);
+	/* Last user calls fail. */
+	if (--d->use == 0)
+		d->fail(d->state, d->arg);
 }
 
-struct dns_async *dns_resolve_and_connect(struct lightningd_state *state,
+struct dns_async *dns_resolve_and_connect_(struct lightningd_state *state,
 		  const char *name, const char *port,
 		  struct io_plan *(*init)(struct io_conn *,
 					  struct lightningd_state *,
-					  const char *name, const char *port))
+					  void *arg),
+		  void (*fail)(struct lightningd_state *, void *arg),
+		  void *arg)
 {
 	int pfds[2];
 	struct dns_async *d = tal(NULL, struct dns_async);
@@ -158,8 +174,9 @@ struct dns_async *dns_resolve_and_connect(struct lightningd_state *state,
 
 	d->state = state;
 	d->init = init;
-	d->name = tal_strdup(d, name);
-	d->port = tal_strdup(d, port);
+	d->fail = fail;
+	d->arg = arg;
+	d->name = tal_fmt(d, "%s:%s", name, port);
 
 	/* First fork child to get addresses. */
 	if (pipe(pfds) != 0) {
@@ -184,6 +201,7 @@ struct dns_async *dns_resolve_and_connect(struct lightningd_state *state,
 	}
 
 	close(pfds[1]);
+	d->use = 1;
 	conn = io_new_conn(state, pfds[0], init_dns_conn, d);
 	io_set_finish(conn, reap_child, d);
 	tal_steal(conn, d);

daemon/dns.h

@@ -3,14 +3,28 @@
 #include "config.h"
 #include <ccan/io/io.h>
 #include <ccan/tal/tal.h>
+#include <ccan/typesafe_cb/typesafe_cb.h>
 #include <stdbool.h>
 
 struct lightningd_state;
 struct netaddr;
-struct dns_async *dns_resolve_and_connect(struct lightningd_state *state,
+
+#define dns_resolve_and_connect(state, name, port, initfn, failfn, arg) \
+	dns_resolve_and_connect_((state), (name), (port),		\
+			typesafe_cb_preargs(struct io_plan *, void *, \
+					    (initfn), (arg),		\
+					    struct io_conn *,		\
+					    struct lightningd_state *), \
+			typesafe_cb_preargs(void, void *, (failfn), (arg), \
+					    struct lightningd_state *), \
+				 (arg))
+
+struct dns_async *dns_resolve_and_connect_(struct lightningd_state *state,
 		  const char *name, const char *port,
 		  struct io_plan *(*init)(struct io_conn *,
 					  struct lightningd_state *,
-					  const char *name, const char *port));
+					  void *arg),
+		  void (*fail)(struct lightningd_state *, void *arg),
+		  void *arg);
 
 #endif /* PETTYCOIN_DNS_H */

daemon/peer.c

@@ -80,18 +80,17 @@ static struct peer *new_peer(struct lightningd_state *state,
 	return peer;
 }
 
-struct io_plan *peer_connected_out(struct io_conn *conn,
-				   struct lightningd_state *state,
-				   const char *name, const char *port)
+static struct io_plan *peer_connected_out(struct io_conn *conn,
+					  struct lightningd_state *state,
+					  char *dest)
 {
 	struct peer *peer = new_peer(state, conn, SOCK_STREAM, IPPROTO_TCP,
 				     "out");
 	if (!peer) {
-		log_unusual(peer->log, "Failed to make peer for %s:%s",
-			    name, port);
+		log_unusual(peer->log, "Failed to make peer for %s", dest);
 		return io_close(conn);
 	}
-	log_info(peer->log, "Connected out to %s:%s", name, port);
+	log_info(peer->log, "Connected out to %s", dest);
 	return peer_crypto_setup(conn, peer, peer_test);
 }
 
@@ -191,12 +190,19 @@ void setup_listeners(struct lightningd_state *state, unsigned int portnum)
 		fatal("Could not bind to a network address");
 }
 
+static void peer_failed(struct lightningd_state *state, char *dest)
+{
+	/* FIXME: Better diagnostics! */
+	log_unusual(state->base_log, "Connect to %s failed", dest);
+}
+
 static void json_connect(struct command *cmd,
 			const char *buffer, const jsmntok_t *params)
 {
 	struct json_result *response;
 	jsmntok_t *host, *port;
 	const char *hoststr, *portstr;
+	char *dest;
 
 	json_get_params(buffer, params, "host", &host, "port", &port, NULL);
 
@@ -205,12 +211,13 @@ static void json_connect(struct command *cmd,
 		return;
 	}
 
-	hoststr = tal_strndup(cmd, buffer + host->start,
+	hoststr = tal_strndup(cmd->state, buffer + host->start,
 			      host->end - host->start);
-	portstr = tal_strndup(cmd, buffer + port->start,
+	portstr = tal_strndup(cmd->state, buffer + port->start,
 			      port->end - port->start);
+	dest = tal_fmt(cmd->state, "%s:%s", hoststr, portstr);
 	if (!dns_resolve_and_connect(cmd->state, hoststr, portstr,
-				     peer_connected_out)) {
+				     peer_connected_out, peer_failed, dest)) {
 		command_fail(cmd, "DNS failed");
 		return;
 	}

daemon/peer.h

@@ -25,11 +25,6 @@ struct peer {
 	struct log *log;
 };
 
-struct io_conn;
-struct io_plan *peer_connected_out(struct io_conn *conn,
-				   struct lightningd_state *state,
-				   const char *name, const char *port);
-
 void setup_listeners(struct lightningd_state *state, unsigned int portnum);
 
 #endif /* LIGHTNING_DAEMON_PEER_H */