closing: add option to set closing range.

This affects the range we offer even without quick-close, but it's
more critical for quick-close.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Changelog-Added: JSONRPC: `close` now takes a `feerange` parameter to set min/max fee rates for mutual close.

lightningd/channel.c

@@ -263,6 +263,7 @@ struct channel *new_unsaved_channel(struct peer *peer,
 	channel->closing_fee_negotiation_step_unit
 		= CLOSING_FEE_NEGOTIATION_STEP_UNIT_PERCENTAGE;
 	channel->shutdown_wrong_funding = NULL;
+	channel->closing_feerate_range = NULL;
 
 	/* Channel is connected! */
 	channel->connected = true;
@@ -429,6 +430,7 @@ struct channel *new_channel(struct peer *peer, u64 dbid,
 		= CLOSING_FEE_NEGOTIATION_STEP_UNIT_PERCENTAGE;
 	channel->shutdown_wrong_funding
 		= tal_steal(channel, shutdown_wrong_funding);
+	channel->closing_feerate_range = NULL;
 	if (local_shutdown_scriptpubkey)
 		channel->shutdown_scriptpubkey[LOCAL]
 			= tal_steal(channel, local_shutdown_scriptpubkey);

lightningd/channel.h

@@ -174,6 +174,9 @@ struct channel {
 	/* optional wrong_funding for mutual close */
 	const struct bitcoin_outpoint *shutdown_wrong_funding;
 
+	/* optional feerate min/max for mutual close */
+	u32 *closing_feerate_range;
+
 	/* Reestablishment stuff: last sent commit and revocation details. */
 	bool last_was_revoke;
 	struct changed_htlc *last_sent_commit;

lightningd/closing_control.c

@@ -193,7 +193,7 @@ void peer_start_closingd(struct channel *channel,
 			 struct per_peer_state *pps)
 {
 	u8 *initmsg;
-	u32 feerate, *max_feerate;
+	u32 min_feerate, feerate, *max_feerate;
 	struct amount_msat their_msat;
 	struct amount_sat feelimit;
 	int hsmfd;
@@ -266,6 +266,14 @@ void peer_start_closingd(struct channel *channel,
 	} else
 		max_feerate = NULL;
 
+	min_feerate = feerate_min(ld, NULL);
+
+	/* If they specified feerates in `close`, they apply now! */
+	if (channel->closing_feerate_range) {
+		min_feerate = channel->closing_feerate_range[0];
+		max_feerate = &channel->closing_feerate_range[1];
+	}
+
 	/* BOLT #3:
 	 *
 	 * Each node offering a signature:
@@ -298,8 +306,7 @@ void peer_start_closingd(struct channel *channel,
 				       amount_msat_to_sat_round_down(channel->our_msat),
 				       amount_msat_to_sat_round_down(their_msat),
 				       channel->our_config.dust_limit,
-				       feerate_min(ld, NULL), feerate,
-				       max_feerate,
+				       min_feerate, feerate, max_feerate,
 				       feelimit,
 				       channel->shutdown_scriptpubkey[LOCAL],
 				       channel->shutdown_scriptpubkey[REMOTE],

lightningd/peer_control.c

@@ -1661,6 +1661,31 @@ static struct command_result *param_outpoint(struct command *cmd,
 				     "should be a txid:outnum");
 }
 
+static struct command_result *param_feerate_range(struct command *cmd,
+						  const char *name,
+						  const char *buffer,
+						  const jsmntok_t *tok,
+						  u32 **feerate_range)
+{
+	struct command_result *ret;
+	u32 *rate;
+
+	*feerate_range = tal_arr(cmd, u32, 2);
+	if (tok->type != JSMN_ARRAY || tok->size != 2)
+		return command_fail_badparam(cmd, name, buffer, tok,
+					     "should be an array of 2 entries");
+
+	ret = param_feerate(cmd, name, buffer, tok+1, &rate);
+	if (ret)
+		return ret;
+	(*feerate_range)[0] = *rate;
+	ret = param_feerate(cmd, name, buffer, tok+2, &rate);
+	if (ret)
+		return ret;
+	(*feerate_range)[1] = *rate;
+	return NULL;
+}
+
 static struct command_result *json_close(struct command *cmd,
 					 const char *buffer,
 					 const jsmntok_t *obj UNNEEDED,
@@ -1674,6 +1699,7 @@ static struct command_result *json_close(struct command *cmd,
 	bool close_script_set, wrong_funding_changed, *force_lease_close;
 	const char *fee_negotiation_step_str;
 	struct bitcoin_outpoint *wrong_funding;
+	u32 *feerate_range;
 	char* end;
 	bool anysegwit;
 
@@ -1687,6 +1713,7 @@ static struct command_result *json_close(struct command *cmd,
 		   p_opt("wrong_funding", param_outpoint, &wrong_funding),
 		   p_opt_def("force_lease_closed", param_bool,
 			     &force_lease_close, false),
+		   p_opt("feerange", param_feerate_range, &feerate_range),
 		   NULL))
 		return command_param_failed();
 
@@ -1845,6 +1872,9 @@ static struct command_result *json_close(struct command *cmd,
 			wrong_funding_changed = false;
 	}
 
+	/* Works fine if feerate_range is NULL */
+	channel->closing_feerate_range = tal_steal(channel, feerate_range);
+
 	/* Normal case.
 	 * We allow states shutting down and sigexchange; a previous
 	 * close command may have timed out, and this current command

lightningd/test/run-invoice-select-inchan.c

@@ -534,6 +534,11 @@ struct command_result *param_escaped_string(struct command *cmd UNNEEDED,
 					    const jsmntok_t *tok UNNEEDED,
 					    const char **str UNNEEDED)
 { fprintf(stderr, "param_escaped_string called!\n"); abort(); }
+/* Generated stub for param_feerate */
+struct command_result *param_feerate(struct command *cmd UNNEEDED, const char *name UNNEEDED,
+				     const char *buffer UNNEEDED, const jsmntok_t *tok UNNEEDED,
+				     u32 **feerate UNNEEDED)
+{ fprintf(stderr, "param_feerate called!\n"); abort(); }
 /* Generated stub for param_label */
 struct command_result *param_label(struct command *cmd UNNEEDED, const char *name UNNEEDED,
 				   const char * buffer UNNEEDED, const jsmntok_t *tok UNNEEDED,