Unfinished patch for switching from isaac to siphash...

siphash-route-bench.patch

diff --git a/gossipd/routing.c b/gossipd/routing.c
index 69db3001..5798c239 100644
--- a/gossipd/routing.c
+++ b/gossipd/routing.c
@@ -5,7 +5,6 @@
 #include <ccan/array_size/array_size.h>
 #include <ccan/crypto/siphash24/siphash24.h>
 #include <ccan/endian/endian.h>
-#include <ccan/isaac/isaac64.h>
 #include <ccan/structeq/structeq.h>
 #include <ccan/tal/str/str.h>
 #include <common/features.h>
@@ -334,28 +333,18 @@ static u64 risk_fee(u64 amount, u32 delay, double riskfactor)
 /* We track totals, rather than costs.  That's because the fee depends
  * on the current amount passing through. */
 static void bfg_one_edge(struct node *node, size_t edgenum, double riskfactor,
-			 double fuzz, const struct isaac64_ctx *baserng)
+			 double fuzz, const struct siphash_seed *base_seed)
 {
 	struct node_connection *c = node->in[edgenum];
 	size_t h;
-	struct isaac64_ctx myrng;
 	double fee_scale = 1.0;
-	u8 *scid;
 
 	if (fuzz != 0.0) {
-		/* Copy RNG state */
-		myrng = *baserng;
-
-		/* Provide the channel short ID, as additional
-		 * entropy. */
-		scid = tal_arr(NULL, u8, 0);
-		towire_short_channel_id(&scid, &c->short_channel_id);
-		isaac64_reseed(&myrng,
-			       (const unsigned char *) scid, tal_len(scid));
-		tal_free(scid);
+		u64 scid = short_channel_id_to_uint(&c->short_channel_id);
+		u64 h =	siphash24(base_seed, &scid, sizeof(scid));
 
 		/* Scale fees for this channel */
-		fee_scale = 1.0 + fuzz * isaac64_next_signed_double(&myrng);
+		fee_scale = 1.0 + fuzz * h / UINT64_MAX;
 	}
 
 	assert(c->dst == node);
@@ -403,7 +392,7 @@ static struct node_connection *
 find_route(const tal_t *ctx, struct routing_state *rstate,
 	   const struct pubkey *from, const struct pubkey *to, u64 msatoshi,
 	   double riskfactor,
-	   double fuzz, struct isaac64_ctx *baserng,
+	   double fuzz, const struct siphash_seed *base_seed,
 	   u64 *fee, struct node_connection ***route)
 {
 	struct node *n, *src, *dst;
@@ -465,7 +454,7 @@ find_route(const tal_t *ctx, struct routing_state *rstate,
 					continue;
 				}
 				bfg_one_edge(n, i, riskfactor,
-					     fuzz, baserng);
+					     fuzz, base_seed);
 				SUPERVERBOSE("...done");
 			}
 		}
@@ -1144,7 +1133,7 @@ struct route_hop *get_route(tal_t *ctx, struct routing_state *rstate,
 			    const struct pubkey *destination,
 			    const u32 msatoshi, double riskfactor,
 			    u32 final_cltv,
-			    double fuzz, u8 *seed)
+			    double fuzz, const struct siphash_seed *base_seed)
 {
 	struct node_connection **route;
 	u64 total_amount;
@@ -1153,14 +1142,10 @@ struct route_hop *get_route(tal_t *ctx, struct routing_state *rstate,
 	struct route_hop *hops;
 	int i;
 	struct node_connection *first_conn;
-	isaac64_ctx baserng;
-
-	/* Load base RNG */
-	isaac64_init(&baserng, (const unsigned char*) seed, tal_count(seed));
 
 	first_conn = find_route(ctx, rstate, source, destination, msatoshi,
 				riskfactor / BLOCKS_PER_YEAR / 10000,
-				fuzz, &baserng,
+				fuzz, base_seed,
 				&fee, &route);
 
 	if (!first_conn) {
diff --git a/gossipd/routing.h b/gossipd/routing.h
index 1afd71b1..b68bfe66 100644
--- a/gossipd/routing.h
+++ b/gossipd/routing.h
@@ -187,7 +187,8 @@ struct route_hop *get_route(tal_t *ctx, struct routing_state *rstate,
 			    const struct pubkey *destination,
 			    const u32 msatoshi, double riskfactor,
 			    u32 final_cltv,
-			    double fuzz, u8 *seed);
+			    double fuzz,
+			    const struct siphash_seed *base_seed);
 /* Disable channel(s) based on the given routing failure. */
 void routing_failure(struct routing_state *rstate,
 		     const struct pubkey *erring_node,
diff --git a/gossipd/test/run-bench-find_route.c b/gossipd/test/run-bench-find_route.c
index 03643f7d..42a1abed 100644
--- a/gossipd/test/run-bench-find_route.c
+++ b/gossipd/test/run-bench-find_route.c
@@ -177,6 +167,7 @@ int main(int argc, char *argv[])
 	struct pubkey me = nodeid(0);
 	bool perfme = false;
 	const double riskfactor = 0.01 / BLOCKS_PER_YEAR / 10000;
+	struct siphash_seed base_seed;
 
 	secp256k1_ctx = secp256k1_context_create(SECP256K1_CONTEXT_VERIFY
 						 | SECP256K1_CONTEXT_SIGN);
@@ -194,6 +185,7 @@ int main(int argc, char *argv[])
 	if (argc > 3)
 		opt_usage_and_exit("[num_nodes [num_runs]]");
 
+	memset(&base_seed, 0, sizeof(base_seed));
 	for (size_t i = 0; i < num_nodes; i++)
 		populate_random_node(rstate, i);
 
@@ -212,7 +204,7 @@ int main(int argc, char *argv[])
 		nc = find_route(ctx, rstate, &from, &to,
 				pseudorand(100000),
 				riskfactor,
-				0.0, NULL,
+				0.75, &base_seed,
 				&fee, &route);
 		num_success += (nc != NULL);
 		tal_free(route);