common: add routing test using real data which crashes.

The amount is set not to crash by default, but run
"common/test/run-route-infloop 8388607" and you'll see a crash.

Sorry about the 7MB blob, but this testing was quite revealing and
I consider it worth adding.

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

common/test/Makefile

@@ -38,7 +38,7 @@ common/test/run-json:					\
 	wire/peer_wiregen.o				\
 	wire/towire.o
 
-common/test/run-route common/test/run-route-specific:	\
+common/test/run-route common/test/run-route-specific common/test/run-route-infloop:	\
 	common/amount.o					\
 	common/dijkstra.o				\
 	common/fp16.o					\

common/test/run-route-infloop.c

@@ -0,0 +1,161 @@
+/* Test based on bug report from Ken Sedgewick, where routing would crash.
+ * I took his gossip_store (this version is compacted) and brute forced routes from
+ * his node with different amounts until I reproduced it */
+#include "config.h"
+#include <assert.h>
+#include <common/channel_type.h>
+#include <common/dijkstra.h>
+#include <common/gossmap.h>
+#include <common/gossip_store.h>
+#include <common/route.h>
+#include <common/setup.h>
+#include <common/type_to_string.h>
+#include <common/utils.h>
+#include <math.h>
+#include <stdio.h>
+#include <inttypes.h>
+#include <wire/peer_wiregen.h>
+#include <unistd.h>
+
+/* AUTOGENERATED MOCKS START */
+/* Generated stub for fromwire_bigsize */
+bigsize_t fromwire_bigsize(const u8 **cursor UNNEEDED, size_t *max UNNEEDED)
+{ fprintf(stderr, "fromwire_bigsize called!\n"); abort(); }
+/* Generated stub for fromwire_channel_id */
+bool fromwire_channel_id(const u8 **cursor UNNEEDED, size_t *max UNNEEDED,
+			 struct channel_id *channel_id UNNEEDED)
+{ fprintf(stderr, "fromwire_channel_id called!\n"); abort(); }
+/* Generated stub for fromwire_tlv */
+bool fromwire_tlv(const u8 **cursor UNNEEDED, size_t *max UNNEEDED,
+		  const struct tlv_record_type *types UNNEEDED, size_t num_types UNNEEDED,
+		  void *record UNNEEDED, struct tlv_field **fields UNNEEDED,
+		  const u64 *extra_types UNNEEDED, size_t *err_off UNNEEDED, u64 *err_type UNNEEDED)
+{ fprintf(stderr, "fromwire_tlv called!\n"); abort(); }
+/* Generated stub for towire_bigsize */
+void towire_bigsize(u8 **pptr UNNEEDED, const bigsize_t val UNNEEDED)
+{ fprintf(stderr, "towire_bigsize called!\n"); abort(); }
+/* Generated stub for towire_channel_id */
+void towire_channel_id(u8 **pptr UNNEEDED, const struct channel_id *channel_id UNNEEDED)
+{ fprintf(stderr, "towire_channel_id called!\n"); abort(); }
+/* Generated stub for towire_tlv */
+void towire_tlv(u8 **pptr UNNEEDED,
+		const struct tlv_record_type *types UNNEEDED, size_t num_types UNNEEDED,
+		const void *record UNNEEDED)
+{ fprintf(stderr, "towire_tlv called!\n"); abort(); }
+/* AUTOGENERATED MOCKS END */
+
+/* Node id 03942f5fe67645fdce4584e7f159c1f0a396b05fbc15f0fb7d6e83c553037b1c73 */
+static struct gossmap *gossmap;
+
+static u64 capacity_bias(const struct gossmap *map,
+			 const struct gossmap_chan *c,
+			 int dir,
+			 struct amount_msat amount)
+{
+	struct amount_sat capacity;
+	u64 amtmsat = amount.millisatoshis; /* Raw: lengthy math */
+	double capmsat;
+
+	/* Can fail in theory if gossmap changed underneath. */
+	if (!gossmap_chan_get_capacity(map, c, &capacity))
+		return 0;
+
+	capmsat = (double)capacity.satoshis * 1000; /* Raw: lengthy math */
+	return -log((capmsat + 1 - amtmsat) / (capmsat + 1));
+}
+
+static u64 route_score(u32 distance,
+		       struct amount_msat cost,
+		       struct amount_msat risk,
+		       int dir,
+		       const struct gossmap_chan *c)
+{
+	u64 cmsat = cost.millisatoshis; /* Raw: lengthy math */
+	u64 rmsat = risk.millisatoshis; /* Raw: lengthy math */
+	u64 bias = capacity_bias(gossmap, c, dir, cost);
+
+	/* Smoothed harmonic mean to avoid division by 0 */
+	u64 costs = (cmsat * rmsat * bias) / (cmsat + rmsat + bias + 1);
+
+	if (costs > 0xFFFFFFFF)
+		costs = 0xFFFFFFFF;
+	return costs;
+}
+
+int main(int argc, char *argv[])
+{
+	const double riskfactor = 10;
+	const u32 final_delay = 159;
+	struct node_id my_id;
+	const struct gossmap_node **nodes, *me;
+	u64 amt;
+
+	common_setup(argv[0]);
+
+	/* 8388607 crashes, use half that so we don't break CI! */
+	if (!argv[1])
+		amt = 8388607 / 2;
+	else
+		amt = atol(argv[1]);
+	gossmap = gossmap_load(tmpctx, "tests/data/routing_gossip_store", NULL);
+
+	nodes = tal_arr(tmpctx, const struct gossmap_node *, 0);
+	for (struct gossmap_node *n = gossmap_first_node(gossmap);
+	     n;
+	     n = gossmap_next_node(gossmap, n)) {
+		tal_arr_expand(&nodes, n);
+	}
+
+	assert(node_id_from_hexstr("03942f5fe67645fdce4584e7f159c1f0a396b05fbc15f0fb7d6e83c553037b1c73",
+				   strlen("03942f5fe67645fdce4584e7f159c1f0a396b05fbc15f0fb7d6e83c553037b1c73"),
+				   &my_id));
+	me = gossmap_find_node(gossmap, &my_id);
+	assert(me);
+
+	printf("Destination node, success, probability, hops, fees, cltv, scid...\n");
+	for (size_t i = 0; i < tal_count(nodes); i++) {
+		const struct dijkstra *dij;
+		struct route_hop *r;
+		struct node_id them;
+
+		if (nodes[i] == me)
+			continue;
+
+		dij = dijkstra(tmpctx, gossmap, nodes[i], amount_msat(amt), riskfactor,
+			       route_can_carry, route_score, NULL);
+		r = route_from_dijkstra(tmpctx, gossmap, dij, me, amount_msat(amt), final_delay);
+
+		gossmap_node_get_id(gossmap, nodes[i], &them);
+
+		printf("%s,", node_id_to_hexstr(tmpctx, &them));
+		if (!r) {
+			printf("0,0.0,");
+		} else {
+			double probability = 1;
+			for (size_t j = 0; j < tal_count(r); j++) {
+				struct amount_sat capacity_sat;
+				u64 cap_msat;
+				struct gossmap_chan *c = gossmap_find_chan(gossmap, &r[j].scid);
+				assert(c);
+				assert(gossmap_chan_get_capacity(gossmap, c, &capacity_sat));
+
+				cap_msat = capacity_sat.satoshis * 1000;
+				/* Assume linear distribution, implying probability depends on
+				 * amount we would leave in channel */
+				assert(cap_msat >= r[0].amount.millisatoshis);
+				probability *= (double)(cap_msat - r[0].amount.millisatoshis) / cap_msat;
+			}
+			printf("1,%f,%zu,%"PRIu64",%u",
+			       probability,
+			       tal_count(r),
+			       r[0].amount.millisatoshis - amt,
+			       r[0].delay - final_delay);
+			for (size_t j = 0; j < tal_count(r); j++)
+				printf(",%s/%u", short_channel_id_to_str(tmpctx, &r[j].scid), r[j].direction);
+		}
+		printf("\n");
+	}
+
+	common_shutdown();
+	return 0;
+}

tools/check-spelling.sh

@@ -1,6 +1,6 @@
 #!/usr/bin/env bash
 
-if git --no-pager grep -nHiE 'l[ightn]{6}g|l[ightn]{8}g|ilghtning|lgihtning|lihgtning|ligthning|lighnting|lightinng|lightnnig|lightnign' -- . ':!tools/check-spelling.sh' | grep -vE "highlighting|LightningGrpc"; then
+if git --no-pager grep -nHiE 'l[ightn]{6}g|l[ightn]{8}g|ilghtning|lgihtning|lihgtning|ligthning|lighnting|lightinng|lightnnig|lightnign' -- . ':!tools/check-spelling.sh' ':!tests/data/routing_gossip_store' | grep -vE "highlighting|LightningGrpc"; then
     echo "Identified a likely misspelling of the word \"lightning\" (see above). Please fix."
     echo "Is this warning incorrect? Please teach tools/check-spelling.sh about the exciting new word."
     exit 1