df-open: add a 'open_commands' list to stash pending opens around in

`openchannel_signed` commands hang out across the openingd/channeld
boundary -- we don't return until we've successfully broadcast the
transaction (or timed out waiting for them to send a tx_sigs back).

lightningd/lightningd.c

@@ -195,6 +195,7 @@ 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->open_commands);
 	list_head_init(&ld->ping_commands);
 	list_head_init(&ld->waitblockheight_commands);
 

lightningd/lightningd.h

@@ -178,6 +178,8 @@ struct lightningd {
 	struct list_head sendpay_commands;
 	/* Outstanding close commands. */
 	struct list_head close_commands;
+	/* Outstanding openchannel_signed commands. */
+	struct list_head open_commands;
 	/* Outstanding ping commands. */
 	struct list_head ping_commands;
 

lightningd/peer_control.c

@@ -74,6 +74,17 @@ struct close_command {
 	bool force;
 };
 
+struct open_command {
+	/* Inside struct lightningd open_commands. */
+	struct list_node list;
+	/* Command structure. This is the parent of the open command. */
+	struct command *cmd;
+	/* Channel being opened. */
+	struct channel *channel;
+	/* PSBT in flight */
+	struct wally_psbt *psbt;
+};
+
 static void destroy_peer(struct peer *peer)
 {
 	list_del_from(&peer->ld->peers, &peer->list);
@@ -324,6 +335,68 @@ register_close_command(struct lightningd *ld,
 			     &close_command_timeout, cc);
 }
 
+/* Destroy the open command structure in reaction to the
+ * channel being destroyed. */
+static void
+destroy_open_command_on_channel_destroy(struct channel *_ UNUSED,
+					struct open_command *oc)
+{
+	/* The oc has the command as parent, so resolving the
+	 * command destroys the oc and triggers destroy_open_command.
+	 * Clear the oc->channel first so that we will not try to
+	 * remove a destructor. */
+	oc->channel = NULL;
+	was_pending(command_fail(oc->cmd, LIGHTNINGD,
+				 "Channel forgotten before open concluded."));
+}
+
+/* Destroy the open command structure. */
+static void
+destroy_open_command(struct open_command *oc)
+{
+	list_del(&oc->list);
+	/* If destroy_close_command_on_channel_destroy was
+	 * triggered beforehand, it will have cleared
+	 * the channel field, preventing us from removing it
+	 * from an already-destroyed channel. */
+	if (!oc->channel)
+		return;
+	tal_del_destructor2(oc->channel,
+			    &destroy_open_command_on_channel_destroy,
+			    oc);
+}
+
+struct open_command *find_open_command(struct lightningd *ld,
+				       struct channel *channel)
+{
+	struct open_command *oc, *n;
+
+	list_for_each_safe (&ld->open_commands, oc, n, list) {
+		if (oc->channel != channel)
+			continue;
+		return oc;
+	}
+
+	return NULL;
+}
+
+void register_open_command(struct lightningd *ld,
+			   struct command *cmd,
+			   struct channel *channel)
+{
+	struct open_command *oc;
+	assert(channel);
+
+	oc = tal(cmd, struct open_command);
+	list_add_tail(&ld->open_commands, &oc->list);
+	oc->cmd = cmd;
+	oc->channel = channel;
+	tal_add_destructor(oc, &destroy_open_command);
+	tal_add_destructor2(channel,
+			    &destroy_open_command_on_channel_destroy,
+			    oc);
+}
+
 static bool invalid_last_tx(const struct bitcoin_tx *tx)
 {
 	/* This problem goes back further, but was discovered just before the

lightningd/peer_control.h

@@ -16,6 +16,7 @@
 #include <wire/peer_wire.h>
 
 struct per_peer_state;
+struct wally_psbt;
 
 struct peer {
 	/* Inside ld->peers. */
@@ -89,6 +90,16 @@ void channel_watch_funding(struct lightningd *ld, struct channel *channel);
 
 struct amount_msat channel_amount_receivable(const struct channel *channel);
 
+/* Find the open command that was registered for this channel */
+struct open_command *find_open_command(struct lightningd *ld,
+				       struct channel *channel);
+
+/* Save an `openchannel_signed` command */
+void register_open_command(struct lightningd *ld,
+			   struct command *cmd,
+			   struct channel *channel);
+
+
 /* Pull peers, channels and HTLCs from db, and wire them up.
  * Returns any HTLCs we have to resubmit via htlcs_resubmit. */
 struct htlc_in_map *load_channels_from_wallet(struct lightningd *ld);