libplugin-pay: make sure get_gossmap calls are balanced by put_gossmap.

This will become important when we apply localmods to the gossmap at these points.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

plugins/libplugin-pay.c

@@ -2,6 +2,7 @@
 #include <ccan/array_size/array_size.h>
 #include <ccan/tal/str/str.h>
 #include <common/blindedpay.h>
+#include <common/daemon.h>
 #include <common/dijkstra.h>
 #include <common/gossmap.h>
 #include <common/json_stream.h>
@@ -16,6 +17,7 @@
 #include <wire/peer_wire.h>
 
 static struct gossmap *global_gossmap;
+static bool got_gossmap;
 
 static void init_gossmap(struct plugin *plugin)
 {
@@ -33,15 +35,29 @@ static void init_gossmap(struct plugin *plugin)
 			   num_channel_updates_rejected);
 }
 
-struct gossmap *get_gossmap(struct plugin *plugin)
+static struct gossmap *get_gossmap(struct payment *payment)
 {
+	assert(!got_gossmap);
 	if (!global_gossmap)
-		init_gossmap(plugin);
+		init_gossmap(payment->plugin);
 	else
 		gossmap_refresh(global_gossmap, NULL);
+	got_gossmap = true;
 	return global_gossmap;
 }
 
+static void put_gossmap(struct payment *payment)
+{
+	assert(got_gossmap);
+	got_gossmap = false;
+}
+
+int libplugin_pay_poll(struct pollfd *fds, nfds_t nfds, int timeout)
+{
+	assert(!got_gossmap);
+	return daemon_poll(fds, nfds, timeout);
+}
+
 struct payment *payment_new(tal_t *ctx, struct command *cmd,
 			    struct payment *parent,
 			    struct payment_modifier **mods)
@@ -832,10 +848,11 @@ static struct command_result *payment_getroute(struct payment *p)
 	 * free an eventual stale route. */
 	p->route = tal_free(p->route);
 
-	gossmap = get_gossmap(p->plugin);
+	gossmap = get_gossmap(p);
 
 	dst = gossmap_find_node(gossmap, p->getroute->destination);
 	if (!dst) {
+		put_gossmap(p);
 		payment_fail(
 			p, "Unknown destination %s",
 			type_to_string(tmpctx, struct node_id,
@@ -848,6 +865,7 @@ static struct command_result *payment_getroute(struct payment *p)
 	/* If we don't exist in gossip, routing can't happen. */
 	src = gossmap_find_node(gossmap, p->local_id);
 	if (!src) {
+		put_gossmap(p);
 		payment_fail(p, "We don't have any channels");
 
 		/* Let payment_finished_ handle this, so we mark it as pending */
@@ -857,6 +875,8 @@ static struct command_result *payment_getroute(struct payment *p)
 	p->route = route(p, gossmap, src, dst, p->getroute->amount, p->getroute->cltv,
 			 p->getroute->riskfactorppm / 1000000.0, p->getroute->max_hops,
 			 p, &errstr);
+	put_gossmap(p);
+
 	if (!p->route) {
 		payment_fail(p, "%s", errstr);
 		/* Let payment_finished_ handle this, so we mark it as pending */
@@ -2751,7 +2771,7 @@ static void routehint_pre_getroute(struct routehints_data *d, struct payment *p)
 static void routehint_check_reachable(struct payment *p)
 {
 	const struct gossmap_node *dst, *src;
-	struct gossmap *gossmap = get_gossmap(p->plugin);
+	struct gossmap *gossmap = get_gossmap(p);
 	const struct dijkstra *dij;
 	struct route_hop *r;
 	struct payment *root = payment_root(p);
@@ -2811,6 +2831,7 @@ static void routehint_check_reachable(struct payment *p)
 	}
 
 	routehint_pre_getroute(d, p);
+	put_gossmap(p);
 
 	paymod_log(p, LOG_DBG,
 		   "The destination is%s directly reachable %s attempts "
@@ -2835,7 +2856,7 @@ static void routehint_step_cb(struct routehints_data *d, struct payment *p)
 		 * beginning, and every other payment will filter out the
 		 * exluded ones on the fly. */
 		if (p->parent == NULL) {
-			map = get_gossmap(p->plugin);
+			map = get_gossmap(p);
 			d->routehints = filter_routehints(
 			    map, p, d, p->local_id, p->routes);
 			/* filter_routehints modifies the array, but
@@ -2858,6 +2879,7 @@ static void routehint_step_cb(struct routehints_data *d, struct payment *p)
 			 * in paymod, paymod should use (and mutate) the
 			 * p->routes array, and
 			 */
+			put_gossmap(p);
 			p->routes = d->routehints;
 
 			paymod_log(p, LOG_DBG,

plugins/libplugin-pay.h

@@ -2,6 +2,7 @@
 #define LIGHTNING_PLUGINS_LIBPLUGIN_PAY_H
 #include "config.h"
 
+#include <ccan/io/io.h>
 #include <common/bolt11.h>
 #include <common/route.h>
 #include <plugins/libplugin.h>
@@ -488,7 +489,7 @@ void json_add_payment_success(struct json_stream *js,
 			      const struct preimage *preimage,
 			      const struct payment_tree_result *result);
 
-/* For special effects, like inspecting your own routes. */
-struct gossmap *get_gossmap(struct plugin *plugin);
+/* Overriding io_poll for extra checks. */
+int libplugin_pay_poll(struct pollfd *fds, nfds_t nfds, int timeout);
 
 #endif /* LIGHTNING_PLUGINS_LIBPLUGIN_PAY_H */

plugins/pay.c

@@ -1307,4 +1307,5 @@ int main(int argc, char *argv[])
 				  "Disable multi-part payments.",
 				  flag_option, &disablempp),
 		    NULL);
+	io_poll_override(libplugin_pay_poll);
 }

plugins/test/run-route-overlong.c

@@ -21,6 +21,9 @@ struct command_result *command_finished(struct command *cmd UNNEEDED, struct jso
 /* Generated stub for command_still_pending */
 struct command_result *command_still_pending(struct command *cmd UNNEEDED)
 { fprintf(stderr, "command_still_pending called!\n"); abort(); }
+/* Generated stub for daemon_poll */
+int daemon_poll(struct pollfd *fds UNNEEDED, nfds_t nfds UNNEEDED, int timeout UNNEEDED)
+{ fprintf(stderr, "daemon_poll called!\n"); abort(); }
 /* Generated stub for feature_offered */
 bool feature_offered(const u8 *features UNNEEDED, size_t f UNNEEDED)
 { fprintf(stderr, "feature_offered called!\n"); abort(); }