payalgo: Add maximum delay.

Fixes: ElementsProject#1086

doc/lightning-pay.7

@@ -2,12 +2,12 @@
 .\"     Title: lightning-pay
 .\"    Author: [see the "AUTHOR" section]
 .\" Generator: DocBook XSL Stylesheets v1.79.1 <http://docbook.sf.net/>
-.\"      Date: 03/16/2018
+.\"      Date: 03/21/2018
 .\"    Manual: \ \&
 .\"    Source: \ \&
 .\"  Language: English
 .\"
-.TH "LIGHTNING\-PAY" "7" "03/16/2018" "\ \&" "\ \&"
+.TH "LIGHTNING\-PAY" "7" "03/21/2018" "\ \&" "\ \&"
 .\" -----------------------------------------------------------------
 .\" * Define some portability stuff
 .\" -----------------------------------------------------------------
@@ -31,12 +31,12 @@
 lightning-pay \- Protocol for sending a payment to a BOLT11 invoice
 .SH "SYNOPSIS"
 .sp
-\fBpay\fR \fIbolt11\fR [\fImsatoshi\fR] [\fIdescription\fR] [\fIriskfactor\fR] [\fImaxfeepercent\fR] [\fIretry_for\fR]
+\fBpay\fR \fIbolt11\fR [\fImsatoshi\fR] [\fIdescription\fR] [\fIriskfactor\fR] [\fImaxfeepercent\fR] [\fIretry_for\fR] [\fImaxdelay\fR]
 .SH "DESCRIPTION"
 .sp
 The \fBpay\fR RPC command attempts to find a route to the given destination, and send the funds it asks for\&. If the \fIbolt11\fR does not contain an amount, \fImsatoshi\fR is required, otherwise if it is specified it must be \fInull\fR\&. If \fIbolt11\fR contains a description hash (\fIh\fR field) \fIdescription\fR is required, otherwise it is unused\&. The \fIriskfactor\fR is described in detail in lightning\-getroute(7), and defaults to 1\&.0\&. The \fImaxfeepercent\fR limits the money paid in fees, and defaults to 0\&.5\&. The \(oqmaxfeepercent\(cq is a percentage of the amount that is to be paid\&.
 .sp
-The \fBpay\fR RPC command will randomize routes slightly, as long as the route achieves the targeted \fImaxfeepercent\fR\&.
+The \fBpay\fR RPC command will randomize routes slightly, as long as the route achieves the targeted \fImaxfeepercent\fR and \fImaxdelay\fR\&.
 .sp
 The response will occur when the payment fails or succeeds\&. Once a payment has succeeded, calls to \fBpay\fR with the same \fIbolt11\fR will succeed immediately\&.
 .sp
@@ -122,13 +122,19 @@ field of the error will be routing failure object\&.
 .sp -1
 .IP \(bu 2.3
 .\}
-206\&. Route too expensive\&. The
+206\&. Route too expensive\&. Either the fee or the needed total locktime for the route exceeds your
+\fImaxfeepercent\fR
+or
+\fImaxdelay\fR
+settings, respectively\&. The
 \fIdata\fR
 field of the error will indicate the actual
 \fIfee\fR
 as well as the
 \fIfeepercent\fR
-percentage that the fee has of the destination payment amount\&.
+percentage that the fee has of the destination payment amount\&. It will also indicate the actual
+\fIdelay\fR
+along the route\&.
 .RE
 .sp
 .RS 4

doc/lightning-pay.7.txt

@@ -8,7 +8,7 @@ lightning-pay - Protocol for sending a payment to a BOLT11 invoice
 
 SYNOPSIS
 --------
-*pay* 'bolt11' ['msatoshi'] ['description'] ['riskfactor'] ['maxfeepercent'] ['retry_for']
+*pay* 'bolt11' ['msatoshi'] ['description'] ['riskfactor'] ['maxfeepercent'] ['retry_for'] ['maxdelay']
 
 DESCRIPTION
 -----------
@@ -24,7 +24,7 @@ The `maxfeepercent' is a percentage of the amount that is to be
 paid.
 
 The *pay* RPC command will randomize routes slightly, as long as the
-route achieves the targeted 'maxfeepercent'.
+route achieves the targeted 'maxfeepercent' and 'maxdelay'.
 
 The response will occur when the payment fails or succeeds.  Once a
 payment has succeeded, calls to *pay* with the same 'bolt11' will
@@ -65,10 +65,14 @@ The following error codes may occur:
 * 203. Permanent failure at destination. The 'data' field of
   the error will be routing failure object.
 * 205. Unable to find a route.
-* 206. Route too expensive. The 'data' field of the error will
-  indicate the actual 'fee' as well as the 'feepercent'
-  percentage that the fee has of the destination payment
-  amount.
+* 206. Route too expensive.
+  Either the fee or the needed total locktime for the route
+  exceeds your 'maxfeepercent' or 'maxdelay' settings,
+  respectively.
+  The 'data' field of the error will indicate the actual 'fee'
+  as well as the 'feepercent' percentage that the fee has of the
+  destination payment amount.
+  It will also indicate the actual 'delay' along the route.
 * 207. Invoice expired. Payment took too long before expiration,
   or already expired at the time you initiated payment.
   The 'data' field of the error indicates 'now' (the current time)

lightningd/payalgo.c

@@ -104,6 +104,7 @@ struct pay {
 	u64 msatoshi;
 	double riskfactor;
 	double maxfeepercent;
+	u32 maxdelay;
 
 	/* Number of getroute and sendpay tries */
 	unsigned int getroute_tries;
@@ -407,7 +408,9 @@ static void json_pay_getroute_reply(struct subd *gossip UNUSED,
 	u64 fee;
 	double feepercent;
 	bool fee_too_high;
+	bool delay_too_high;
 	struct json_result *data;
+	char const *err;
 
 	fromwire_gossip_getroute_reply(reply, reply, &route);
 
@@ -434,30 +437,48 @@ static void json_pay_getroute_reply(struct subd *gossip UNUSED,
 	 * payments are limited to 4294967295 msatoshi. */
 	feepercent = ((double) fee) * 100.0 / ((double) pay->msatoshi);
 	fee_too_high = (feepercent > pay->maxfeepercent);
+	delay_too_high = (route[0].delay > pay->maxdelay);
 	/* compare fuzz to range */
-	if (fee_too_high && pay->fuzz < 0.01) {
+	if ((fee_too_high || delay_too_high) && pay->fuzz < 0.01) {
 		data = new_json_result(pay);
 		json_object_start(data, NULL);
+		json_add_u64(data, "msatoshi", pay->msatoshi);
 		json_add_u64(data, "fee", fee);
 		json_add_double(data, "feepercent", feepercent);
-		json_add_u64(data, "msatoshi", pay->msatoshi);
 		json_add_double(data, "maxfeepercent", pay->maxfeepercent);
+		json_add_u64(data, "delay", (u64) route[0].delay);
+		json_add_num(data, "maxdelay", pay->maxdelay);
 		json_add_num(data, "getroute_tries", pay->getroute_tries);
 		json_add_num(data, "sendpay_tries", pay->sendpay_tries);
+		json_add_route(data, "route",
+			       route, tal_count(route));
 		json_add_failures(data, "failures", &pay->pay_failures);
 		json_object_end(data);
 
-		command_fail_detailed(pay->cmd, PAY_ROUTE_TOO_EXPENSIVE,
-				      data,
+		err = "";
+		if (fee_too_high)
+			err = tal_fmt(pay,
 				      "Fee %"PRIu64" is %f%% "
 				      "of payment %"PRIu64"; "
-				      "max fee requested is %f%%",
+				      "max fee requested is %f%%.",
 				      fee, feepercent,
 				      pay->msatoshi,
 				      pay->maxfeepercent);
+		if (fee_too_high && delay_too_high)
+			err = tal_fmt(pay, "%s ", err);
+		if (delay_too_high)
+			err = tal_fmt(pay,
+				      "%s"
+				      "Delay (locktime) is %"PRIu32" blocks; "
+				      "max delay requested is %u.",
+				      err, route[0].delay, pay->maxdelay);
+
+
+		command_fail_detailed(pay->cmd, PAY_ROUTE_TOO_EXPENSIVE,
+				      data, "%s", err);
 		return;
 	}
-	if (fee_too_high) {
+	if (fee_too_high || delay_too_high) {
 		/* Retry with lower fuzz */
 		pay->fuzz -= 0.15;
 		if (pay->fuzz <= 0.0)
@@ -575,13 +596,15 @@ static void json_pay(struct command *cmd,
 {
 	jsmntok_t *bolt11tok, *msatoshitok, *desctok, *riskfactortok, *maxfeetok;
 	jsmntok_t *retryfortok;
+	jsmntok_t *maxdelaytok;
 	double riskfactor = 1.0;
 	double maxfeepercent = 0.5;
 	u64 msatoshi;
 	struct pay *pay = tal(cmd, struct pay);
 	struct bolt11 *b11;
 	char *fail, *b11str, *desc;
 	unsigned int retryfor = 60;
+	unsigned int maxdelay = 500;
 
 	if (!json_get_params(cmd, buffer, params,
 			     "bolt11", &bolt11tok,
@@ -590,6 +613,7 @@ static void json_pay(struct command *cmd,
 			     "?riskfactor", &riskfactortok,
 			     "?maxfeepercent", &maxfeetok,
 			     "?retry_for", &retryfortok,
+			     "?maxdelay", &maxdelaytok,
 			     NULL)) {
 		return;
 	}
@@ -672,14 +696,32 @@ static void json_pay(struct command *cmd,
 	}
 	pay->maxfeepercent = maxfeepercent;
 
+	if (maxdelaytok
+	    && !json_tok_number(buffer, maxdelaytok, &maxdelay)) {
+		command_fail(cmd, "'%.*s' is not a valid double",
+			     maxdelaytok->end - maxdelaytok->start,
+			     buffer + maxdelaytok->start);
+		return;
+	}
+	if (maxdelay < pay->min_final_cltv_expiry) {
+		command_fail(cmd,
+			     "maxdelay (%u) must be greater than "
+			     "min_final_cltv_expiry (%"PRIu32") of "
+			     "invoice",
+			     maxdelay, pay->min_final_cltv_expiry);
+		return;
+	}
+	pay->maxdelay = maxdelay;
+
 	pay->getroute_tries = 0;
 	pay->sendpay_tries = 0;
 	/* Higher fuzz increases the potential fees we will pay, since
 	 * higher fuzz makes it more likely that high-fee paths get
 	 * selected. We start with very high fuzz, but if the
 	 * returned route is too expensive for the given
-	 * `maxfeepercent` we reduce the fuzz. Starting with high
-	 * fuzz means, if the user allows high fee, we can take
+	 * `maxfeepercent` or `maxdelay` we reduce the fuzz.
+	 * Starting with high
+	 * fuzz means, if the user allows high fee/locktime, we can take
 	 * advantage of that to increase randomization and
 	 * improve privacy somewhat. */
 	pay->fuzz = 0.75;