Add the torrc option HiddenServiceNumIntroductionPoints

This is a way to specify the amount of introduction points an hidden service
can have. Maximum value is 10 and the default is 3.

Fixes #4862

Signed-off-by: David Goulet <dgoulet@ev0ke.net>

changes/bug4862

@@ -0,0 +1,8 @@
+  o Major feature (Hidden Service):
+    - Remove the introduction point adaptative algorithm which is leaking
+      popularity by changing the amount of introduction points depending on
+      the amount of traffic the HS sees. With this, we stick to only 3
+      introduction points.
+    - Add the torrc option HiddenServiceNumIntroductionPoints for an
+      operatory to specify a fix amount of introduction points. Maximum
+      value is 10 and default is 3.

doc/tor.1.txt

@@ -2177,6 +2177,10 @@ The following options are used to configure a hidden service.
     only owner is able to read the hidden service directory. (Default: 0)
     Has no effect on Windows.
 
+[[HiddenServiceNumIntroductionPoints]] **HiddenServiceNumIntroductionPoints** __NUM__::
+    Number of introduction points the hidden service will have. You can't
+    have more than 10. (Default: 3)
+
 TESTING NETWORK OPTIONS
 -----------------------
 

src/or/config.c

@@ -288,6 +288,7 @@ static config_var_t option_vars_[] = {
   VAR("HiddenServiceAllowUnknownPorts",LINELIST_S, RendConfigLines, NULL),
   VAR("HiddenServiceMaxStreams",LINELIST_S, RendConfigLines, NULL),
   VAR("HiddenServiceMaxStreamsCloseCircuit",LINELIST_S, RendConfigLines, NULL),
+  VAR("HiddenServiceNumIntroductionPoints", LINELIST_S, RendConfigLines, NULL),
   V(HiddenServiceStatistics,     BOOL,     "0"),
   V(HidServAuth,                 LINELIST, NULL),
   V(CloseHSClientCircuitsImmediatelyOnTimeout, BOOL, "0"),

src/or/rendservice.c

@@ -87,6 +87,8 @@ struct rend_service_port_config_s {
 
 /** Try to maintain this many intro points per service by default. */
 #define NUM_INTRO_POINTS_DEFAULT 3
+/** Maximum number of intro points per service. */
+#define NUM_INTRO_POINTS_MAX 10
 
 /** If we can't build our intro circuits, don't retry for this long. */
 #define INTRO_CIRC_RETRY_PERIOD (60*5)
@@ -577,7 +579,22 @@ rend_config_services(const or_options_t *options, int validate_only)
       log_info(LD_CONFIG,
                "HiddenServiceMaxStreamsCloseCircuit=%d for %s",
                (int)service->max_streams_close_circuit, service->directory);
-
+    } else if (!strcasecmp(line->key, "HiddenServiceNumIntroductionPoints")) {
+      service->n_intro_points_wanted =
+        (unsigned int) tor_parse_long(line->value, 10,
+                                      NUM_INTRO_POINTS_DEFAULT,
+                                      NUM_INTRO_POINTS_MAX, &ok, NULL);
+      if (!ok) {
+        log_warn(LD_CONFIG,
+                 "HiddenServiceNumIntroductionPoints "
+                 "should be between %d and %d, not %s",
+                 NUM_INTRO_POINTS_DEFAULT, NUM_INTRO_POINTS_MAX,
+                 line->value);
+        rend_service_free(service);
+        return -1;
+      }
+      log_info(LD_CONFIG, "HiddenServiceNumIntroductionPoints=%d for %s",
+               service->n_intro_points_wanted, service->directory);
     } else if (!strcasecmp(line->key, "HiddenServiceAuthorizeClient")) {
       /* Parse auth type and comma-separated list of client names and add a
        * rend_authorized_client_t for each client to the service's list