gossipd: fix riskfactor passing.

We used a u16, and a 1000 multiplier, which meant we wrapped at
riskfactor 66.  We also never undid the multiplier, so we ended up
applying 1000x the riskfactor they specified.

This changes us to pass the riskfactor with a 1M multiplier.  The next
patch changes the definition of riskfactor to be more useful.

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

gossipd/gossip_wire.csv

@@ -29,7 +29,8 @@ gossip_getroute_request,3006
 gossip_getroute_request,,source,struct pubkey
 gossip_getroute_request,,destination,struct pubkey
 gossip_getroute_request,,msatoshi,u64
-gossip_getroute_request,,riskfactor,u16
+# We don't pass doubles, so pass riskfactor * 1000000.
+gossip_getroute_request,,riskfactor_by_million,u64
 gossip_getroute_request,,final_cltv,u32
 gossip_getroute_request,,fuzz,double
 gossip_getroute_request,,num_excluded,u16

gossipd/gossipd.c

@@ -1894,7 +1894,7 @@ static struct io_plan *getroute_req(struct io_conn *conn, struct daemon *daemon,
 	struct pubkey source, destination;
 	u64 msatoshi;
 	u32 final_cltv;
-	u16 riskfactor;
+	u64 riskfactor_by_million;
 	u32 max_hops;
 	u8 *out;
 	struct route_hop *hops;
@@ -1909,7 +1909,7 @@ static struct io_plan *getroute_req(struct io_conn *conn, struct daemon *daemon,
 	 * avoid being too predictable. */
 	if (!fromwire_gossip_getroute_request(msg, msg,
 					      &source, &destination,
-					      &msatoshi, &riskfactor,
+					      &msatoshi, &riskfactor_by_million,
 					      &final_cltv, &fuzz,
 					      &excluded,
 					      &max_hops))
@@ -1921,7 +1921,7 @@ static struct io_plan *getroute_req(struct io_conn *conn, struct daemon *daemon,
 
 	/* routing.c does all the hard work; can return NULL. */
 	hops = get_route(tmpctx, daemon->rstate, &source, &destination,
-			 msatoshi, riskfactor, final_cltv,
+			 msatoshi, riskfactor_by_million / 1000000.0, final_cltv,
 			 fuzz, pseudorand_u64(), excluded, max_hops);
 
 	out = towire_gossip_getroute_reply(NULL, hops);

lightningd/gossip_control.c

@@ -352,7 +352,8 @@ static struct command_result *json_getroute(struct command *cmd,
 	}
 
 	u8 *req = towire_gossip_getroute_request(cmd, source, destination,
-						 *msatoshi, *riskfactor * 1000,
+						 *msatoshi,
+						 *riskfactor * 1000000.0,
 						 *cltv, fuzz,
 						 excluded,
 						 *max_hops);