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pay: Add a limit to the fee.

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Fixes: #717
This commit is contained in:
ZmnSCPxj
2018-02-07 13:17:58 +00:00
committed by Christian Decker
parent e1284b1df1
commit 354fafbf60
1 changed files with 65 additions and 2 deletions
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67
lightningd/pay.c
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@@ -701,6 +701,8 @@ AUTODATA(json_command, &sendpay_command);
struct pay {
struct sha256 payment_hash;
struct command *cmd;
u64 msatoshi;
double maxfeepercent;
};
static void json_pay_getroute_reply(struct subd *gossip,
@@ -708,6 +710,10 @@ static void json_pay_getroute_reply(struct subd *gossip,
struct pay *pay)
{
struct route_hop *route;
u64 msatoshi_sent;
u64 fee;
double feepercent;
struct json_result *data;
fromwire_gossip_getroute_reply(reply, reply, NULL, &route);
@@ -717,14 +723,45 @@ static void json_pay_getroute_reply(struct subd *gossip,
return;
}
msatoshi_sent = route[0].amount;
fee = msatoshi_sent - pay->msatoshi;
/* FIXME: IEEE Double-precision floating point has only 53 bits
* of precision. Total satoshis that can ever be created is
* slightly less than 2100000000000000. Total msatoshis that
* can ever be created is 1000 times that or
* 2100000000000000000, requiring 60.865 bits of precision,
* and thus losing precision in the below. Currently, OK, as,
* payments are limited to 4294967295 msatoshi. */
feepercent = ((double) fee) * 100.0 / ((double) pay->msatoshi);
if (feepercent > pay->maxfeepercent) {
data = new_json_result(pay);
json_object_start(data, NULL);
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_object_end(data);
command_fail_detailed(pay->cmd, PAY_ROUTE_TOO_EXPENSIVE,
data,
"Fee %"PRIu64" is %f%% "
"of payment %"PRIu64"; "
"max fee requested is %f%%",
fee, feepercent,
pay->msatoshi,
pay->maxfeepercent);
return;
}
send_payment(pay->cmd, &pay->payment_hash, route);
}
static void json_pay(struct command *cmd,
const char *buffer, const jsmntok_t *params)
{
jsmntok_t *bolt11tok, *msatoshitok, *desctok, *riskfactortok;
jsmntok_t *bolt11tok, *msatoshitok, *desctok, *riskfactortok, *maxfeetok;
double riskfactor = 1.0;
double maxfeepercent = 0.5;
u64 msatoshi;
struct pay *pay = tal(cmd, struct pay);
struct bolt11 *b11;
@@ -736,6 +773,7 @@ static void json_pay(struct command *cmd,
"?msatoshi", &msatoshitok,
"?description", &desctok,
"?riskfactor", &riskfactortok,
"?maxfeepercent", &maxfeetok,
NULL)) {
return;
}
@@ -776,6 +814,7 @@ static void json_pay(struct command *cmd,
return;
}
}
pay->msatoshi = msatoshi;
if (riskfactortok
&& !json_tok_double(buffer, riskfactortok, &riskfactor)) {
@@ -785,6 +824,26 @@ static void json_pay(struct command *cmd,
return;
}
if (maxfeetok
&& !json_tok_double(buffer, maxfeetok, &maxfeepercent)) {
command_fail(cmd, "'%.*s' is not a valid double",
(int)(maxfeetok->end - maxfeetok->start),
buffer + maxfeetok->start);
return;
}
/* Ensure it is in range 0.0 <= maxfeepercent <= 100.0 */
if (!(0.0 <= maxfeepercent)) {
command_fail(cmd, "%f maxfeepercent must be non-negative",
maxfeepercent);
return;
}
if (!(maxfeepercent <= 100.0)) {
command_fail(cmd, "%f maxfeepercent must be <= 100.0",
maxfeepercent);
return;
}
pay->maxfeepercent = maxfeepercent;
/* FIXME: use b11->routes */
req = towire_gossip_getroute_request(cmd, &cmd->ld->id,
&b11->receiver_id,
@@ -797,7 +856,11 @@ static void json_pay(struct command *cmd,
static const struct json_command pay_command = {
"pay",
json_pay,
"Send payment specified by {bolt11} with optional {msatoshi} (if and only if {bolt11} does not have amount), {description} (required if {bolt11} uses description hash) and {riskfactor} (default 1.0)"
"Send payment specified by {bolt11} with optional {msatoshi} "
"(if and only if {bolt11} does not have amount), "
"{description} (required if {bolt11} uses description hash), "
"{riskfactor} (default 1.0), and "
"{maxfeepercent} (default 0.5) the maximum acceptable fee as a percentage (e.g. 0.5 => 0.5%)"
};
AUTODATA(json_command, &pay_command);