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plugins/pay: Exclude the entrypoint to a routehint to avoid cycles

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This uses @cdecker's idea of excluding the routehinted channel from the route,
and also consumes the route hints as it goes so that it makes progress.

I don't know if this is correct, but it reliably passes tests/test_pay.py::test_tlv_or_legacy
now.
This commit is contained in:
Rusty Russell
2020-07-23 14:20:10 +09:30
committed by Christian Decker
parent 56dd18e01e
commit 2556df5f7c
2 changed files with 25 additions and 0 deletions
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22
plugins/libplugin-pay.c
View File

@@ -26,6 +26,7 @@ struct payment *payment_new(tal_t *ctx, struct command *cmd,
p->getroute->riskfactorppm = 10000000;
p->abort = false;
p->route = NULL;
p->temp_exclusion = NULL;
/* Copy over the relevant pieces of information. */
if (parent != NULL) {
@@ -482,6 +483,16 @@ static void payment_getroute_add_excludes(struct payment *p,
for (size_t i=0; i<tal_count(nodes); i++)
json_add_node_id(js, NULL, &nodes[i]);
/* And make sure we don't route in a circle via the routehint! */
if (p->temp_exclusion) {
struct short_channel_id_dir scidd;
scidd.scid = *p->temp_exclusion;
for (size_t dir = 0; dir < 2; dir++) {
scidd.dir = dir;
json_add_short_channel_id_dir(js, NULL, &scidd);
}
}
json_array_end(js);
}
@@ -1776,6 +1787,12 @@ static struct route_info *next_routehint(struct routehints_data *d,
if (d->routehints == NULL || numhints == 0)
return NULL;
/* BOLT #11:
*
* - if a writer offers more than one of any field type, it:
* - MUST specify the most-preferred field first, followed
* by less-preferred fields, in order.
*/
for (; d->offset <numhints; d->offset++) {
curr = d->routehints[d->offset];
if (curr == NULL || !routehint_excluded(p, curr))
@@ -1840,8 +1857,13 @@ static void routehint_pre_getroute(struct routehints_data *d, struct payment *p)
type_to_string(tmpctx, struct short_channel_id,
&d->current_routehint->short_channel_id),
d->current_routehint->cltv_expiry_delta);
/* Exclude the entrypoint to the routehint, so we don't end up
* going through the destination to the entrypoint. */
p->temp_exclusion = &d->current_routehint[0].short_channel_id;
} else {
plugin_log(p->plugin, LOG_DBG, "Not using a routehint");
p->temp_exclusion = NULL;
}
}

3
plugins/libplugin-pay.h
View File

@@ -232,6 +232,9 @@ struct payment {
struct channel_hint *channel_hints;
struct node_id *excluded_nodes;
/* Optional temporarily excluded channel (i.e. this routehint) */
struct short_channel_id *temp_exclusion;
struct payment_result *result;
/* Did something happen that will cause all future attempts to fail?