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plugins/offers: improve reply path logic.

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We generate a reply path by simply reversing the outgoing path:

	A->B->C gives reply path B->A
	A->B gives reply path A

But if we are not a public node, we can't use ourselves as the first
entry of the reply path: this happens if we directly connect to the
head of a blinded path (as we now support).

In this case, give the entire path as a blinded path.  We could do
this all the time, but there are some cases where nodes don't like
sending replies where the node itself is the head of the blinded
path (like CLN v24.05 or before!).

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
This commit is contained in:
Rusty Russell 2024-07-10 12:27:27 +09:30 committed by Vincenzo Palazzo
parent e95f8a9751
commit 80ab83a495
1 changed files with 26 additions and 6 deletions
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32
plugins/fetchinvoice.c
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@ -410,27 +410,47 @@ static struct command_result *param_offer(struct command *cmd,
}
static struct blinded_path *make_reply_path(const tal_t *ctx,
struct plugin *plugin,
const struct sent *sent,
const struct pubkey *path,
struct secret *reply_secret)
{
struct pubkey *ids;
assert(tal_count(path) > 0);
assert(tal_count(path) > 1);
randombytes_buf(reply_secret, sizeof(struct secret));
if (sent->dev_reply_path) {
ids = sent->dev_reply_path;
} else {
size_t nhops = tal_count(path);
size_t nhops = tal_count(path), start;
struct node_id second_last;
/* Usually we have path A->B->C and we make
* reply B->A. But if B is not public,
* we need to use the full thing.
*
* This happens when we connect directly to the
* head of a blinded path, but we're not a public
* node.
*/
node_id_from_pubkey(&second_last, &path[nhops-2]);
if (!gossmap_find_node(get_gossmap(plugin), &second_last))
start = nhops - 1;
else
start = nhops - 2;
/* FIXME: Could create an independent reply path, not just
* reverse existing. */
ids = tal_arr(tmpctx, struct pubkey, nhops - 1);
for (int i = nhops - 2; i >= 0; i--)
ids[nhops - 2 - i] = path[i];
ids = tal_arr(tmpctx, struct pubkey, start + 1);
for (int i = start; i >= 0; i--)
ids[start - i] = path[i];
}
plugin_log(plugin, LOG_DBG, "Reply path:");
for (size_t i = 0; i < tal_count(ids); i++)
plugin_log(plugin, LOG_DBG, "...%s", fmt_pubkey(tmpctx, &ids[i]));
/* Reply path */
return incoming_message_blinded_path(ctx, ids, NULL, reply_secret);
@ -473,7 +493,7 @@ static struct command_result *establish_path_done(struct command *cmd,
"Refusing to talk to ourselves");
/* Add reply path to final_tlv (it already contains invoice_request/invoice) */
final_tlv->reply_path = make_reply_path(final_tlv, sent, path, sent->reply_secret);
final_tlv->reply_path = make_reply_path(final_tlv, cmd->plugin, sent, path, sent->reply_secret);
/* Replace first hop with scidd if they said to */
if (sent->dev_path_use_scidd)