Clarify use of magic number 0.98 with #define.

src/or/circuitbuild.c

@@ -529,10 +529,8 @@ void
 circuit_build_times_add_timeout_worker(circuit_build_times_t *cbt,
                                        double quantile_cutoff)
 {
-  /* We want to stay a bit short of 1.0, because longtail is
-   * loooooooooooooooooooooooooooooooooooooooooooooooooooong */
   build_time_t gentime = circuit_build_times_generate_sample(cbt,
-              quantile_cutoff, 0.98);
+              quantile_cutoff, MAX_SYNTHETIC_QUANTILE);
 
   if (gentime < (build_time_t)cbt->timeout*1000) {
     log_warn(LD_CIRC,

src/or/or.h

@@ -2867,6 +2867,11 @@ void entry_guards_free_all(void);
  * RECENT_CIRCUITS before calculating a new timeout */
 #define MAX_RECENT_TIMEOUT_RATE 0.7999999
 
+/** Maximum quantile to use to generate synthetic timeouts.
+ *  We want to stay a bit short of 1.0, because longtail is
+ *  loooooooooooooooooooooooooooooooooooooooooooooooooooong. */
+#define MAX_SYNTHETIC_QUANTILE 0.98
+
 /** Minimum circuits before estimating a timeout */
 #define MIN_CIRCUITS_TO_OBSERVE 500
 

src/or/test.c

@@ -3444,7 +3444,8 @@ test_circuit_timeout(void)
     int n = 0;
     for (i=0; i < MIN_CIRCUITS_TO_OBSERVE; i++) {
       if (circuit_build_times_add_time(&estimate,
-              circuit_build_times_generate_sample(&initial, 0, .98)) == 0) {
+              circuit_build_times_generate_sample(&initial, 0,
+                  MAX_SYNTHETIC_QUANTILE)) == 0) {
         n++;
       }
     }