renepay: use askrene-inform-channel

Use askrene-inform-channel to update the knowledge of the liquidity when
a payment attempt fails.

Changelog-None

Signed-off-by: Lagrang3 <[email protected]>

Author: Lagrang3

plugins/renepay/routefail.c

@@ -2,11 +2,14 @@
 #include <common/json_stream.h>
 #include <common/jsonrpc_errors.h>
 #include <plugins/renepay/renepay.h>
+#include <plugins/renepay/renepayconfig.h>
 #include <plugins/renepay/routefail.h>
 #include <plugins/renepay/routetracker.h>
 #include <plugins/renepay/utils.h>
 #include <wire/peer_wiregen.h>
 
+#define MIN(x, y) ((x) < (y) ? (x) : (y))
+
 enum node_type {
 	FINAL_NODE,
 	INTERMEDIATE_NODE,
@@ -102,6 +105,32 @@ static void bias_channel(struct routefail *r, struct short_channel_id_dir scidd,
 	send_outreq(req);
 }
 
+static void channel_can_send(struct routefail *r,
+			     struct short_channel_id_dir scidd,
+			     struct amount_msat amount)
+{
+	struct out_req *req = add_to_rpcbatch(
+	    r->batch, "askrene-inform-channel", NULL, log_routefail_err, r);
+	json_add_string(req->js, "layer", RENEPAY_LAYER);
+	json_add_short_channel_id_dir(req->js, "short_channel_id_dir", scidd);
+	json_add_amount_msat(req->js, "amount_msat", amount);
+	json_add_string(req->js, "inform", "unconstrained");
+	send_outreq(req);
+}
+
+static void channel_cannot_send(struct routefail *r,
+				struct short_channel_id_dir scidd,
+				struct amount_msat amount)
+{
+	struct out_req *req = add_to_rpcbatch(
+	    r->batch, "askrene-inform-channel", NULL, log_routefail_err, r);
+	json_add_string(req->js, "layer", RENEPAY_LAYER);
+	json_add_short_channel_id_dir(req->js, "short_channel_id_dir", scidd);
+	json_add_amount_msat(req->js, "amount_msat", amount);
+	json_add_string(req->js, "inform", "constrained");
+	send_outreq(req);
+}
+
 /*****************************************************************************
  * update_gossip
  *
@@ -301,6 +330,25 @@ static void handle_failure(struct routefail *r)
 			node_type = ORIGIN_NODE;
 		else
 			node_type = INTERMEDIATE_NODE;
+
+		/* All channels before the hop that failed have supposedly the
+		 * ability to forward the payment. This is information. */
+		const int last_good_channel =
+		    MIN(*result->erring_index, path_len) - 1;
+		for (int i = 0; i <= last_good_channel; i++) {
+			scidd.scid = route->hops[i].scid;
+			scidd.dir = route->hops[i].direction;
+			channel_can_send(r, scidd, route->hops[i].amount);
+		}
+		if (failcode == WIRE_TEMPORARY_CHANNEL_FAILURE &&
+		    (last_good_channel + 1) < path_len) {
+			scidd.scid = route->hops[last_good_channel + 1].scid;
+			scidd.dir =
+			    route->hops[last_good_channel + 1].direction;
+			channel_cannot_send(
+			    r, scidd,
+			    route->hops[last_good_channel + 1].amount);
+		}
 	}
 
 	switch (failcode) {

plugins/renepay/routetracker.c

@@ -342,6 +342,8 @@ struct command_result *notification_sendpay_success(struct command *cmd,
 			   json_tok_full_len(sub), json_tok_full(buf, sub));
 
 	assert(route->result->status == SENDPAY_COMPLETE);
+	// FIXME: call askrene-inform-channel with inform=succeeded for this
+	// route
 	routetracker_add_to_final(payment, payment->routetracker, route);
 	return notification_handled(cmd);
 }