lightningd: add --dev-allow-shutdown-destination-change to unstick ex…

…isting nodes.

This will solve the problem for users who already hit the bug fixed by
the previous patch!

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

lightningd/closing_control.c

@@ -692,7 +692,8 @@ static struct command_result *json_close(struct command *cmd,
 	if (close_to_script) {
 		bool is_p2sh;
 
-		if (!tal_arr_eq(close_to_script, channel->shutdown_scriptpubkey[LOCAL])) {
+		if (!tal_arr_eq(close_to_script, channel->shutdown_scriptpubkey[LOCAL])
+		    && !cmd->ld->dev_allow_shutdown_destination_change) {
 			const u8 *defp2tr, *defp2wpkh;
 			/* We cannot change the closing script once we've
 			 * started shutdown: onchaind relies on it for output

lightningd/lightningd.c

@@ -146,6 +146,7 @@ static struct lightningd *new_lightningd(const tal_t *ctx)
 	ld->dev_disable_commit = -1;
 	ld->dev_no_ping_timer = false;
 	ld->dev_any_channel_type = false;
+	ld->dev_allow_shutdown_destination_change = false;
 
 	/*~ This is a CCAN list: an embedded double-linked list.  It's not
 	 * really typesafe, but relies on convention to access the contents.

lightningd/lightningd.h

@@ -343,6 +343,9 @@ struct lightningd {
 	/* Tell openingd/dualopend to accept all, allow sending any. */
 	bool dev_any_channel_type;
 
+	/* Allow changing of shutdown output point even if dangerous */
+	bool dev_allow_shutdown_destination_change;
+
 	/* tor support */
 	struct wireaddr *proxyaddr;
 	bool always_use_proxy;

lightningd/options.c

@@ -907,6 +907,10 @@ static void dev_register_opts(struct lightningd *ld)
 		     opt_set_bool,
 		     &ld->dev_any_channel_type,
 		     "Allow sending any channel type, and accept any");
+	clnopt_noarg("--dev-allow-shutdown-destination-change", OPT_DEV,
+		     opt_set_bool,
+		     &ld->dev_allow_shutdown_destination_change,
+		     "Allow destination override on close, even if risky");
 }
 
 static const struct config testnet_config = {