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renepay: add a channel filtering paymod

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We add a channel filtering paymod that disables channels that have very
low max_htlc. It can be expanded to consider other properties as well,
for instance high base fee, low capacity or high latency.

Changelog-Added: renepay: prune the network by disabling channels we
don't like, eg. very low max_htlc.

Signed-off-by: Lagrang3 <lagrang3@protonmail.com>
This commit is contained in:
Lagrang3 2024-08-13 12:59:52 +09:30 committed by ShahanaFarooqui
parent c0dd3cd826
commit 44d53dc473
1 changed files with 77 additions and 14 deletions
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91
plugins/renepay/mods.c
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@ -1080,6 +1080,71 @@ static struct command_result *knowledgerelax_cb(struct payment *payment)
REGISTER_PAYMENT_MODIFIER(knowledgerelax, knowledgerelax_cb);
/*****************************************************************************
* channelfilter
*
* Disable some channels. The possible motivations are:
* - avoid the overhead of unproductive routes that go through channels with
* very low max_htlc that would lead us to a payment partition with too
* many HTCLs,
* - avoid channels with very small capacity as well, for which the probability
* of success is always small anyways,
* - discard channels with very high base fee that would break our cost
* estimation,
* - avoid high latency tor nodes.
* All combined should reduce the size of the network we explore hopefully
* reducing the runtime of the MCF solver (FIXME: I should measure this
* eventually).
* FIXME: shall we set these threshold parameters as plugin options?
*/
static struct command_result *channelfilter_cb(struct payment *payment)
{
assert(payment);
assert(pay_plugin->gossmap);
const double HTLC_MAX_FRACTION = 0.01; // 1%
const u64 HTLC_MAX_STOP_MSAT = 1000000000; // 1M sats
u64 disabled_count = 0;
u64 htlc_max_threshold = HTLC_MAX_FRACTION * payment->payment_info
.amount.millisatoshis; /* Raw: a fraction of this amount. */
/* Don't exclude channels with htlc_max above HTLC_MAX_STOP_MSAT even if
* that represents a fraction of the payment smaller than
* HTLC_MAX_FRACTION. */
htlc_max_threshold = MIN(htlc_max_threshold, HTLC_MAX_STOP_MSAT);
for (const struct gossmap_node *node =
gossmap_first_node(pay_plugin->gossmap);
node; node = gossmap_next_node(pay_plugin->gossmap, node)) {
for (size_t i = 0; i < node->num_chans; i++) {
int dir;
const struct gossmap_chan *chan = gossmap_nth_chan(
pay_plugin->gossmap, node, i, &dir);
const u64 htlc_max =
fp16_to_u64(chan->half[dir].htlc_max);
if (htlc_max < htlc_max_threshold) {
struct short_channel_id_dir scidd = {
.scid = gossmap_chan_scid(
pay_plugin->gossmap, chan),
.dir = dir};
disabledmap_add_channel(payment->disabledmap,
scidd);
disabled_count++;
}
}
}
// FIXME: prune the network over other parameters, eg. capacity,
// fees, ...
plugin_log(pay_plugin->plugin, LOG_DBG,
"channelfilter: disabling %" PRIu64 " channels.",
disabled_count);
return payment_continue(payment);
}
REGISTER_PAYMENT_MODIFIER(channelfilter, channelfilter_cb);
/*****************************************************************************
* alwaystrue
*
@ -1135,22 +1200,20 @@ void *payment_virtual_program[] = {
/*4*/ OP_CALL, &knowledgerelax_pay_mod,
/*6*/ OP_CALL, &getmychannels_pay_mod,
/*8*/ OP_CALL, &routehints_pay_mod,
// TODO: add a channel filter, for example disable channels that have
// htlcmax < 0.1% of payment amount, or base fee > 100msat, or
// proportional_fee > 10%, or capacity < 10% payment amount
/*10*/OP_CALL, &channelfilter_pay_mod,
// TODO shadow_additions
/* do */
/*10*/ OP_CALL, &pendingsendpays_pay_mod,
/*12*/ OP_CALL, &checktimeout_pay_mod,
/*14*/ OP_CALL, &refreshgossmap_pay_mod,
/*16*/ OP_CALL, &compute_routes_pay_mod,
/*18*/ OP_CALL, &send_routes_pay_mod,
/*12*/ OP_CALL, &pendingsendpays_pay_mod,
/*14*/ OP_CALL, &checktimeout_pay_mod,
/*16*/ OP_CALL, &refreshgossmap_pay_mod,
/*18*/ OP_CALL, &compute_routes_pay_mod,
/*20*/ OP_CALL, &send_routes_pay_mod,
/*do*/
/*20*/ OP_CALL, &sleep_pay_mod,
/*22*/ OP_CALL, &collect_results_pay_mod,
/*22*/ OP_CALL, &sleep_pay_mod,
/*24*/ OP_CALL, &collect_results_pay_mod,
/*while*/
/*24*/ OP_IF, &nothaveresults_pay_cond, (void *)20,
/*26*/ OP_IF, &nothaveresults_pay_cond, (void *)22,
/* while */
/*27*/ OP_IF, &retry_pay_cond, (void *)10,
/*30*/ OP_CALL, &end_pay_mod, /* safety net, default failure if reached */
/*32*/ NULL};
/*29*/ OP_IF, &retry_pay_cond, (void *)12,
/*32*/ OP_CALL, &end_pay_mod, /* safety net, default failure if reached */
/*34*/ NULL};