Merge branch 'bug5452'

changes/bug5452

@@ -0,0 +1,4 @@
+  o Minor features:
+    - Check CircuitBuildTimeout and LearnCircuitBuildTimeout in
+      options_validate(); warn if LearnCircuitBuildTimeout is disabled
+      and CircuitBuildTimeout is set unreasonably low. Fixes bug 5452.

src/or/config.c

@@ -3320,6 +3320,13 @@ compute_publishserverdescriptor(or_options_t *options)
  * expose more information than we're comfortable with. */
 #define MIN_HEARTBEAT_PERIOD (30*60)
 
+/** Lowest recommended value for CircuitBuildTimeout; if it is set too low
+ * and LearnCircuitBuildTimeout is off, the failure rate for circuit
+ * construction may be very high.  In that case, if it is set below this
+ * threshold emit a warning.
+ * */
+#define RECOMMENDED_MIN_CIRCUIT_BUILD_TIMEOUT (10)
+
 /** Return 0 if every setting in <b>options</b> is reasonable, and a
  * permissible transition from <b>old_options</b>. Else return -1.
  * Should have no side effects, except for normalizing the contents of
@@ -3716,6 +3723,17 @@ options_validate(or_options_t *old_options, or_options_t *options,
     options->LearnCircuitBuildTimeout = 0;
   }
 
+  if (!(options->LearnCircuitBuildTimeout) &&
+        options->CircuitBuildTimeout < RECOMMENDED_MIN_CIRCUIT_BUILD_TIMEOUT) {
+    log_warn(LD_CONFIG,
+        "CircuitBuildTimeout is shorter (%d seconds) than recommended "
+        "(%d seconds), and LearnCircuitBuildTimeout is disabled.  "
+        "If tor isn't working, raise this value or enable "
+        "LearnCircuitBuildTimeout.",
+        options->CircuitBuildTimeout,
+        RECOMMENDED_MIN_CIRCUIT_BUILD_TIMEOUT );
+  }
+
   if (options->MaxCircuitDirtiness < MIN_MAX_CIRCUIT_DIRTINESS) {
     log_warn(LD_CONFIG, "MaxCircuitDirtiness option is too short; "
              "raising to %d seconds.", MIN_MAX_CIRCUIT_DIRTINESS);