API: `fundchannel_cancel` can cancel fundchannel process before funding broadcast

channeld/channel_wire.csv

@@ -198,3 +198,10 @@ msgdata,channel_specific_feerates,feerate_ppm,u32,
 msgtype,channel_got_announcement,1017
 msgdata,channel_got_announcement,remote_ann_node_sig,secp256k1_ecdsa_signature,
 msgdata,channel_got_announcement,remote_ann_bitcoin_sig,secp256k1_ecdsa_signature,
+
+# Ask channeld to send a error message. Used in forgetting channel case.
+msgtype,channel_send_error,1008
+msgdata,channel_send_error,reason,wirestring,
+
+# Tell master channeld has sent the error message.
+msgtype,channel_send_error_reply,1108

channeld/channeld.c

@@ -2796,6 +2796,20 @@ static void handle_shutdown_cmd(struct peer *peer, const u8 *inmsg)
 	start_commit_timer(peer);
 }
 
+static void handle_send_error(struct peer *peer, const u8 *msg)
+{
+	char *reason;
+	if (!fromwire_channel_send_error(msg, msg, &reason))
+		master_badmsg(WIRE_CHANNEL_SEND_ERROR, msg);
+	status_debug("Send error reason: %s", reason);
+	sync_crypto_write(peer->pps,
+			  take(towire_errorfmt(NULL, &peer->channel_id,
+					       "%s", reason)));
+
+	wire_sync_write(MASTER_FD,
+			take(towire_channel_send_error_reply(NULL)));
+}
+
 #if DEVELOPER
 static void handle_dev_reenable_commit(struct peer *peer)
 {
@@ -2849,6 +2863,9 @@ static void req_in(struct peer *peer, const u8 *msg)
 	case WIRE_CHANNEL_SEND_SHUTDOWN:
 		handle_shutdown_cmd(peer, msg);
 		return;
+	case WIRE_CHANNEL_SEND_ERROR:
+		handle_send_error(peer, msg);
+		return;
 #if DEVELOPER
 	case WIRE_CHANNEL_DEV_REENABLE_COMMIT:
 		handle_dev_reenable_commit(peer);
@@ -2875,6 +2892,7 @@ static void req_in(struct peer *peer, const u8 *msg)
 	case WIRE_CHANNEL_DEV_REENABLE_COMMIT_REPLY:
 	case WIRE_CHANNEL_FAIL_FALLEN_BEHIND:
 	case WIRE_CHANNEL_DEV_MEMLEAK_REPLY:
+	case WIRE_CHANNEL_SEND_ERROR_REPLY:
 		break;
 	}
 	master_badmsg(-1, msg);

lightningd/channel_control.c

@@ -3,10 +3,13 @@
 #include <ccan/cast/cast.h>
 #include <channeld/gen_channel_wire.h>
 #include <common/features.h>
+#include <common/json_command.h>
+#include <common/jsonrpc_errors.h>
 #include <common/memleak.h>
 #include <common/per_peer_state.h>
 #include <common/timeout.h>
 #include <common/utils.h>
+#include <common/wallet_tx.h>
 #include <common/wire_error.h>
 #include <errno.h>
 #include <gossipd/gossip_constants.h>
@@ -15,6 +18,7 @@
 #include <lightningd/channel_control.h>
 #include <lightningd/closing_control.h>
 #include <lightningd/hsm_control.h>
+#include <lightningd/jsonrpc.h>
 #include <lightningd/lightningd.h>
 #include <lightningd/log.h>
 #include <lightningd/peer_control.h>
@@ -230,6 +234,33 @@ static void peer_start_closingd_after_shutdown(struct channel *channel,
 	channel_set_state(channel, CHANNELD_SHUTTING_DOWN, CLOSINGD_SIGEXCHANGE);
 }
 
+static void handle_error_channel(struct channel *channel,
+				 const u8 *msg)
+{
+	struct command **forgets = tal_steal(tmpctx, channel->forgets);
+	channel->forgets = tal_arr(channel, struct command *, 0);
+
+	if (!fromwire_channel_send_error_reply(msg)) {
+		channel_internal_error(channel, "bad send_error_reply: %s",
+				       tal_hex(tmpctx, msg));
+		return;
+	}
+
+	/* Forget the channel. */
+	delete_channel(channel);
+
+	for (size_t i = 0; i < tal_count(forgets); i++) {
+		assert(!forgets[i]->json_stream);
+
+		struct json_stream *response;
+		response = json_stream_success(forgets[i]);
+		json_add_string(response, "cancelled", "Channel open canceled by RPC(after fundchannel_complete)");
+		was_pending(command_success(forgets[i], response));
+	}
+
+	tal_free(forgets);
+}
+
 static unsigned channel_msg(struct subd *sd, const u8 *msg, const int *fds)
 {
 	enum channel_wire_type t = fromwire_peektype(msg);
@@ -262,6 +293,9 @@ static unsigned channel_msg(struct subd *sd, const u8 *msg, const int *fds)
 	case WIRE_CHANNEL_FAIL_FALLEN_BEHIND:
 		channel_fail_fallen_behind(sd->channel, msg);
 		break;
+	case WIRE_CHANNEL_SEND_ERROR_REPLY:
+		handle_error_channel(sd->channel, msg);
+		break;
 
 	/* And we never get these from channeld. */
 	case WIRE_CHANNEL_INIT:
@@ -281,6 +315,7 @@ static unsigned channel_msg(struct subd *sd, const u8 *msg, const int *fds)
 	case WIRE_CHANNEL_OFFER_HTLC_REPLY:
 	case WIRE_CHANNEL_DEV_REENABLE_COMMIT_REPLY:
 	case WIRE_CHANNEL_DEV_MEMLEAK_REPLY:
+	case WIRE_CHANNEL_SEND_ERROR:
 		break;
 	}
 
@@ -578,3 +613,109 @@ void channel_notify_new_block(struct lightningd *ld,
 
 	tal_free(to_forget);
 }
+
+static void process_check_funding_broadcast(struct bitcoind *bitcoind UNUSED,
+					    const struct bitcoin_tx_output *txout,
+					    void *arg)
+{
+	struct channel *cancel = arg;
+
+	if (txout != NULL) {
+		for (size_t i = 0; i < tal_count(cancel->forgets); i++)
+			was_pending(command_fail(cancel->forgets[i], LIGHTNINGD,
+				    "The funding transaction has been broadcast, "
+				    "please consider `close` or `dev-fail`! "));
+		tal_free(cancel->forgets);
+		cancel->forgets = tal_arr(cancel, struct command *, 0);
+		return;
+	}
+
+	const char *error_reason = "Cancel channel by our RPC "
+				   "command before funding "
+				   "transaction broadcast.";
+	/* Set error so we don't try to reconnect. */
+	cancel->error = towire_errorfmt(cancel, NULL, "%s", error_reason);
+
+	subd_send_msg(cancel->owner,
+		      take(towire_channel_send_error(NULL, error_reason)));
+}
+
+struct command_result *cancel_channel_before_broadcast(struct command *cmd,
+						       const char *buffer,
+						       struct peer *peer,
+						       const jsmntok_t *cidtok)
+{
+	struct channel *cancel_channel, *channel;
+
+	cancel_channel = NULL;
+	if (!cidtok) {
+		list_for_each(&peer->channels, channel, list) {
+			if (cancel_channel) {
+				return command_fail(cmd, LIGHTNINGD,
+						    "Multiple channels:"
+						    " please specify channel_id");
+			}
+			cancel_channel = channel;
+		}
+		if (!cancel_channel)
+			return command_fail(cmd, LIGHTNINGD,
+					    "No channels matching that peer_id");
+	} else {
+		struct channel_id channel_cid;
+		struct channel_id cid;
+		if (!json_tok_channel_id(buffer, cidtok, &cid))
+			return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
+					    "Invalid channel_id parameter.");
+
+		list_for_each(&peer->channels, channel, list) {
+			if (!channel)
+				return command_fail(cmd, LIGHTNINGD,
+						    "No channels matching "
+						    "that peer_id");
+			derive_channel_id(&channel_cid,
+					  &channel->funding_txid,
+					  channel->funding_outnum);
+			if (channel_id_eq(&channel_cid, &cid)) {
+				cancel_channel = channel;
+				break;
+			}
+		}
+		if (!cancel_channel)
+			return command_fail(cmd, JSONRPC2_INVALID_PARAMS,
+					    "Channel ID not found: '%.*s'",
+					    cidtok->end - cidtok->start,
+					    buffer + cidtok->start);
+	}
+
+	/* Check if we broadcast the transaction. (We store the transaction type into DB
+	 * before broadcast). */
+	enum wallet_tx_type type;
+	if(wallet_transaction_type(cmd->ld->wallet,
+				   &cancel_channel->funding_txid,
+				   &type))
+		return command_fail(cmd, LIGHTNINGD,
+				    "Has the funding transaction been broadcast? "
+				    "Please use `close` or `dev-fail` instead.");
+
+	if (channel_has_htlc_out(cancel_channel) ||
+	    channel_has_htlc_in(cancel_channel)) {
+		return command_fail(cmd, LIGHTNINGD,
+				    "This channel has HTLCs attached and it is "
+				    "not safe to cancel. Has the funding transaction "
+				    "been broadcast? Please use `close` or `dev-fail` "
+				    "instead.");
+	}
+
+	tal_arr_expand(&cancel_channel->forgets, cmd);
+
+	/* Check if the transaction is onchain. */
+	/* Note: The above check and this check can't completely ensure that
+	 * the funding transaction isn't broadcast. We can't know if the funding
+	 * is broadcast by external wallet and the transaction hasn't been onchain. */
+	bitcoind_gettxout(cmd->ld->topology->bitcoind,
+			  &cancel_channel->funding_txid,
+			  cancel_channel->funding_outnum,
+			  process_check_funding_broadcast,
+			  cancel_channel);
+	return command_still_pending(cmd);
+}

lightningd/channel_control.h

@@ -23,4 +23,11 @@ bool channel_tell_depth(struct lightningd *ld,
 void channel_notify_new_block(struct lightningd *ld,
 			      u32 block_height);
 
+/* Cancel the channel after `fundchannel_complete` succeeds
+ * but before funding broadcasts. */
+struct command_result *cancel_channel_before_broadcast(struct command *cmd,
+						       const char *buffer,
+						       struct peer *peer,
+						       const jsmntok_t *cidtok);
+
 #endif /* LIGHTNING_LIGHTNINGD_CHANNEL_CONTROL_H */

lightningd/opening_control.c

@@ -295,7 +295,8 @@ static void funding_success(struct channel *channel)
 	/* Well, those cancels didn't work! */
 	for (size_t i = 0; i < tal_count(fc->cancels); i++)
 		was_pending(command_fail(fc->cancels[i], LIGHTNINGD,
-					 "Funding succeeded before cancel"));
+					 "Funding succeeded before cancel. "
+					 "Try fundchannel_cancel again."));
 
 	response = json_stream_success(cmd);
 	json_add_string(response, "channel_id",
@@ -1189,7 +1190,7 @@ static struct command_result *json_fund_channel_complete(struct command *cmd,
 }
 
 /**
- * json_fund_channel_cancel - Entrypoint for cancelling an in flight channel-funding
+ * json_fund_channel_cancel - Entrypoint for cancelling a channel which funding isn't broadcast
  */
 static struct command_result *json_fund_channel_cancel(struct command *cmd,
 						       const char *buffer,
@@ -1199,10 +1200,12 @@ static struct command_result *json_fund_channel_cancel(struct command *cmd,
 
 	struct node_id *id;
 	struct peer *peer;
+	const jsmntok_t *cidtok;
 	u8 *msg;
 
 	if (!param(cmd, buffer, params,
 		   p_req("id", param_node_id, &id),
+		   p_opt("channel_id", param_tok, &cidtok),
 		   NULL))
 		return command_param_failed();
 
@@ -1211,40 +1214,18 @@ static struct command_result *json_fund_channel_cancel(struct command *cmd,
 		return command_fail(cmd, LIGHTNINGD, "Unknown peer");
 	}
 
-	if (!peer->uncommitted_channel) {
-		return command_fail(cmd, LIGHTNINGD, "Peer not connected");
+	if (peer->uncommitted_channel) {
+		if(!peer->uncommitted_channel->fc || !peer->uncommitted_channel->fc->inflight)
+			return command_fail(cmd, LIGHTNINGD, "No channel funding in progress.");
+
+		/* Make sure this gets notified if we succeed or cancel */
+		tal_arr_expand(&peer->uncommitted_channel->fc->cancels, cmd);
+		msg = towire_opening_funder_cancel(NULL);
+		subd_send_msg(peer->uncommitted_channel->openingd, take(msg));
+		return command_still_pending(cmd);
 	}
 
-	if (!peer->uncommitted_channel->fc || !peer->uncommitted_channel->fc->inflight)
-		return command_fail(cmd, LIGHTNINGD, "No channel funding in progress.");
-
-	/**
-	 * there's a question of 'state machinery' here. as is, we're not checking
-	 * to see if you've already called `complete` -- we expect you
-	 * the caller to EITHER pick 'complete' or 'cancel'.
-	 * but if for some reason you've decided to test your luck, how much
-	 * 'handling' can we do for that case? the easiest thing to do is to
-	 * say "sorry you've already called complete", we can't cancel this.
-	 *
-	 * there's also the state you might end up in where you've called
-	 * complete (and it's completed and been passed off to channeld) but
-	 * you've decided (for whatever reason) not to broadcast the transaction
-	 * so your channels have ended up in this 'waiting' state. neither of us
-	 * are actually out any amount of cash, but it'd be nice if there's a way
-	 * to signal to c-lightning (+ your peer) that this channel is dead on arrival.
-	 * ... but also if you then broadcast this tx you'd be in trouble cuz we're
-	 * both going to forget about it. the meta question here is how 'undoable'
-	 * should we make any of this. how much tools do we give you, reader?
-	 *
-	 * for now, let's settle for the EITHER / OR case and disregard the larger
-	 * question about 'how long cancelable'.
-	 */
-
-	/* Make sure this gets notified if we succeed or cancel */
-	tal_arr_expand(&peer->uncommitted_channel->fc->cancels, cmd);
-	msg = towire_opening_funder_cancel(NULL);
-	subd_send_msg(peer->uncommitted_channel->openingd, take(msg));
-	return command_still_pending(cmd);
+	return cancel_channel_before_broadcast(cmd, buffer, peer, cidtok);
 }
 
 /**

wallet/wallet.c

@@ -2847,6 +2847,23 @@ void wallet_transaction_annotate(struct wallet *w,
 	db_exec_prepared_v2(take(stmt));
 }
 
+bool wallet_transaction_type(struct wallet *w, const struct bitcoin_txid *txid,
+			     enum wallet_tx_type *type)
+{
+	struct db_stmt *stmt = db_prepare_v2(w->db, SQL("SELECT type FROM transactions WHERE id=?"));
+	db_bind_sha256(stmt, 0, &txid->shad.sha);
+	db_query_prepared(stmt);
+
+	if (!db_step(stmt)) {
+		tal_free(stmt);
+		return false;
+	}
+
+	*type = db_column_int(stmt, 0);
+	tal_free(stmt);
+	return true;
+}
+
 u32 wallet_transaction_height(struct wallet *w, const struct bitcoin_txid *txid)
 {
 	u32 blockheight;

wallet/wallet.h

@@ -1066,6 +1066,16 @@ void wallet_transaction_annotate(struct wallet *w,
 				 const struct bitcoin_txid *txid,
 				 enum wallet_tx_type type, u64 channel_id);
 
+/**
+ * Get the type of a transaction we are watching by its
+ * txid.
+ *
+ * Returns false if the transaction was not stored in DB.
+ * Returns true if the transaction exists and sets the `type` parameter.
+ */
+bool wallet_transaction_type(struct wallet *w, const struct bitcoin_txid *txid,
+			     enum wallet_tx_type *type);
+
 /**
  * Get the confirmation height of a transaction we are watching by its
  * txid. Returns 0 if the transaction was not part of any block.