Xpay limit path length 26.06

plugins/askrene/askrene.c

@@ -29,6 +29,8 @@
 #include <plugins/askrene/child/child_log.h>
 #include <plugins/askrene/layer.h>
 #include <plugins/askrene/reserve.h>
+#include <stdlib.h>
+#include <string.h>
 #include <sys/wait.h>
 #include <wire/wire_io.h>
 #include <wire/wire_sync.h>
@@ -91,6 +93,44 @@ static struct command_result *param_direction(struct command *cmd,
 	return NULL;
 }
 
+static bool is_maxhops(const char *s)
+{
+	return strncmp(s, "maxhops=", strlen("maxhops=")) == 0;
+}
+
+static bool parse_maxhops(const char *s, u32 *v)
+{
+	if(!is_maxhops(s))
+		return false;
+
+	const char *num = s + strlen("maxhops=");
+	char *end;
+	unsigned long n;
+
+	if (*num < '0' || *num > '9')
+		return false;
+	errno = 0;
+	n = strtoul(num, &end, 10);
+	if (*end != '\0' || errno == ERANGE || n > UINT32_MAX)
+		return false;
+	*v = n;
+	return true;
+}
+
+static u32 extract_maxhops(const char ***layers, u32 default_maxhops)
+{
+	u32 maxhops = default_maxhops;
+	for (size_t i = 0; i < tal_count(*layers); i++) {
+		u32 v;
+		if (parse_maxhops((*layers)[i], &v)) {
+			maxhops = v;
+			tal_arr_remove(layers, i);
+			i--;
+		}
+	}
+	return maxhops;
+}
+
 /* Valid, known layers */
 static struct command_result *param_layer_names(struct command *cmd,
 						const char *name,
@@ -112,6 +152,15 @@ static struct command_result *param_layer_names(struct command *cmd,
 						     "should be a string");
 		(*arr)[i] = json_strdup(*arr, buffer, t);
 
+		if (is_maxhops((*arr)[i])) {
+			u32 v;
+			if (!parse_maxhops((*arr)[i], &v))
+				return command_fail_badparam(
+				    cmd, name, buffer, t,
+				    "maxhops must be a u32");
+			continue;
+		}
+
 		/* Must be a known layer name */
 		if (streq((*arr)[i], "auto.localchans")
 		    || streq((*arr)[i], "auto.sourcefree")
@@ -359,6 +408,7 @@ struct getroutes_info {
 	/* Non-NULL if we are told to use "auto.localchans" */
 	struct layer *local_layer;
 	u32 maxparts;
+	u32 maxhops;
 };
 
 static void add_layer(const struct layer ***layers,
@@ -716,7 +766,11 @@ static struct command_result *do_getroutes(struct command *cmd,
 			  take(capacities),
 			  info->dev_algo == ALGO_SINGLE_PATH,
 			  deadline, srcnode, dstnode, info->amount,
-			  info->maxfee, info->finalcltv, info->maxdelay, info->maxparts,
+			  info->maxfee,
+			  info->finalcltv,
+			  info->maxdelay,
+			  info->maxparts,
+			  info->maxhops,
 			  include_fees,
 			  cmd->id, cmd->filter,
 			  include_next_node_id,
@@ -900,7 +954,7 @@ static struct command_result *json_getroutes(struct command *cmd,
 	/* FIXME: Typo in spec for CLTV in descripton! But it breaks our spelling check, so we omit it above */
 	const u32 maxdelay_allowed = 2016;
 	struct askrene *askrene = get_askrene(cmd->plugin);
-	const u32 default_maxparts = 100;
+	const u32 default_maxparts = 100, default_maxhops = 100;
 	struct getroutes_info *info = tal(cmd, struct getroutes_info);
 	/* param functions require pointers */
 	struct node_id *source, *dest;
@@ -962,6 +1016,11 @@ static struct command_result *json_getroutes(struct command *cmd,
 	info->additional_costs = new_htable(info, additional_cost_htable);
 	info->maxparts = *maxparts;
 
+	/* A trick to pass maxhops without introducing a new RPC or requiring
+	 * developer option.  We pass maxhops as a layer string, eg.
+	 * "maxhops=10" */
+	info->maxhops = extract_maxhops(&info->layers, default_maxhops);
+
 	if (askrene->num_live_requests >= askrene->max_children) {
 		cmd_log(tmpctx, cmd, LOG_INFORM,
 			"Too many running at once (%zu vs %u): waiting",

plugins/askrene/child/child.c

@@ -219,8 +219,11 @@ void run_child(const struct gossmap *gossmap,
 	       const struct gossmap_node *srcnode,
 	       const struct gossmap_node *dstnode,
 	       struct amount_msat amount, struct amount_msat maxfee,
-	       u32 finalcltv, u32 maxdelay, size_t maxparts,
-              bool include_fees,
+	       u32 finalcltv,
+	       u32 maxdelay,
+	       size_t maxparts,
+	       u32 maxhops,
+	       bool include_fees,
 	       const char *cmd_id,
 	       struct json_filter *cmd_filter,
 	       bool include_next_node_id,
@@ -243,11 +246,11 @@ void run_child(const struct gossmap *gossmap,
 	if (single_path) {
 		err = single_path_routes(rq, rq, deadline, srcnode, dstnode,
 					 amount, maxfee, finalcltv,
-					 maxdelay, &flows, &probability, &ecode);
+					 maxdelay, maxhops, &flows, &probability, &ecode);
 	} else {
 		err = default_routes(rq, rq, deadline, srcnode, dstnode,
 				     amount, maxfee, finalcltv, maxdelay,
-				     maxparts, &flows, &probability, &ecode);
+				     maxparts, maxhops, &flows, &probability, &ecode);
 	}
 	if (err) {
 		write_all(replyfd, &ecode, sizeof(ecode));

plugins/askrene/child/child.h

@@ -27,7 +27,10 @@ void run_child(const struct gossmap *gossmap,
 	       const struct gossmap_node *srcnode,
 	       const struct gossmap_node *dstnode,
 	       struct amount_msat amount, struct amount_msat maxfee,
-	       u32 finalcltv, u32 maxdelay, size_t maxparts,
+	       u32 finalcltv,
+	       u32 maxdelay,
+	       size_t maxparts,
+	       u32 maxhops,
 	       bool include_fees,
 	       const char *cmd_id,
 	       struct json_filter *cmd_filter,

plugins/askrene/child/flow.c

@@ -173,6 +173,17 @@ u64 flows_worst_delay(struct flow **flows)
 	return maxdelay;
 }
 
+u32 flows_worst_length(struct flow **flows)
+{
+	u32 maxlen = 0;
+	for (size_t i = 0; i < tal_count(flows); i++) {
+		u32 len = tal_count(flows[i]->path);
+		if (len > maxlen)
+			maxlen = len;
+	}
+	return maxlen;
+}
+
 const char *fmt_flows_step_scid(const tal_t *ctx,
 				const struct route_query *rq,
 				const struct flow *flow, size_t i)

plugins/askrene/child/flow.h

@@ -57,6 +57,9 @@ u64 flow_delay(const struct flow *flow);
 /* Max CLTV any of these flows requires */
 u64 flows_worst_delay(struct flow **flows);
 
+/* Max number of hops any of these flows requires */
+u32 flows_worst_length(struct flow **flows);
+
 const char *fmt_flows_step_scid(const tal_t *ctx,
 				const struct route_query *rq,
 				const struct flow *flow, size_t i);