A relay now advertises "tunnelled-dir-server" in its descriptor

When a relay does not have an open directory port but it has an
orport configured and is accepting client connections then it can
now service tunnelled directory requests, too. This was already true
of relays with an dirport configured.

We also conditionally stop advertising this functionality if the
relay is nearing its bandwidth usage limit - same as how dirport
advertisement is determined.

Partial implementation of prop 237, ticket 12538

1 files changed, 67 insertions, 32 deletions

diff --git a/src/or/router.c b/src/or/router.c
index 49e2e318f5..1927cfd38b 100644
--- a/src/or/router.c
+++ b/src/or/router.c
@@ -1099,39 +1099,25 @@ check_whether_dirport_reachable(void)
          can_reach_dir_port;
 }
 
-/** Look at a variety of factors, and return 0 if we don't want to
- * advertise the fact that we have a DirPort open. Else return the
- * DirPort we want to advertise.
- *
- * Log a helpful message if we change our mind about whether to publish
- * a DirPort.
+/** The lower threshold of remaining bandwidth required to advertise directory
+ * services */
+/* XXX Should this be increased? */
+#define MIN_BW_TO_ADVERTISE_DIRSERVER 51200
+
+/** Helper: Return 1 if we have sufficient resources for serving directory
+ * requests, return 0 otherwise.
+ * dir_port is either 0 or the configured DirPort number.
+ * If AccountingMax is set less than our advertised bandwidth, then don't
+ * serve requests. Likewise, if our advertised bandwidth is less than
+ * MIN_BW_TO_ADVERTISE_DIRSERVER, don't bother trying to serve requests.
  */
 static int
-decide_to_advertise_dirport(const or_options_t *options, uint16_t dir_port)
+router_should_be_directory_server(const or_options_t *options, int dir_port)
 {
   static int advertising=1; /* start out assuming we will advertise */
   int new_choice=1;
   const char *reason = NULL;
 
-  /* Section one: reasons to publish or not publish that aren't
-   * worth mentioning to the user, either because they're obvious
-   * or because they're normal behavior. */
-
-  if (!dir_port) /* short circuit the rest of the function */
-    return 0;
-  if (authdir_mode(options)) /* always publish */
-    return dir_port;
-  if (net_is_disabled())
-    return 0;
-  if (!check_whether_dirport_reachable())
-    return 0;
-  if (!router_get_advertised_dir_port(options, dir_port))
-    return 0;
-
-  /* Section two: reasons to publish or not publish that the user
-   * might find surprising. These are generally config options that
-   * make us choose not to publish. */
-
   if (accounting_is_enabled(options)) {
     /* Don't spend bytes for directory traffic if we could end up hibernating,
      * but allow DirPort otherwise. Some people set AccountingMax because
@@ -1158,10 +1144,9 @@ decide_to_advertise_dirport(const or_options_t *options, uint16_t dir_port)
       new_choice = 0;
       reason = "AccountingMax enabled";
     }
-#define MIN_BW_TO_ADVERTISE_DIRPORT 51200
-  } else if (options->BandwidthRate < MIN_BW_TO_ADVERTISE_DIRPORT ||
+  } else if (options->BandwidthRate < MIN_BW_TO_ADVERTISE_DIRSERVER ||
              (options->RelayBandwidthRate > 0 &&
-              options->RelayBandwidthRate < MIN_BW_TO_ADVERTISE_DIRPORT)) {
+              options->RelayBandwidthRate < MIN_BW_TO_ADVERTISE_DIRSERVER)) {
     /* if we're advertising a small amount */
     new_choice = 0;
     reason = "BandwidthRate under 50KB";
@@ -1169,15 +1154,61 @@ decide_to_advertise_dirport(const or_options_t *options, uint16_t dir_port)
 
   if (advertising != new_choice) {
     if (new_choice == 1) {
-      log_notice(LD_DIR, "Advertising DirPort as %d", dir_port);
+      if (dir_port > 0)
+        log_notice(LD_DIR, "Advertising DirPort as %d", dir_port);
+      else
+        log_notice(LD_DIR, "Advertising directory service support");
     } else {
       tor_assert(reason);
-      log_notice(LD_DIR, "Not advertising DirPort (Reason: %s)", reason);
+      log_notice(LD_DIR, "Not advertising Dir%s (Reason: %s)",
+                 dir_port ? "Port" : "ectory Service support", reason);
     }
     advertising = new_choice;
   }
 
-  return advertising ? dir_port : 0;
+  return advertising;
+}
+
+/** Return 1 if we are configured to accept either relay or directory requests
+ * from clients and we aren't at risk of exceeding our bandwidth limits, thus
+ * we should be a directory server. If not, return 0.
+ */
+int
+dir_server_mode(const or_options_t *options)
+{
+    return (server_mode(options) || options->DirPort_set) &&
+          router_should_be_directory_server(options, 0);
+}
+
+/** Look at a variety of factors, and return 0 if we don't want to
+ * advertise the fact that we have a DirPort open, else return the
+ * DirPort we want to advertise.
+ *
+ * Log a helpful message if we change our mind about whether to publish
+ * a DirPort.
+ */
+static int
+decide_to_advertise_dirport(const or_options_t *options, uint16_t dir_port)
+{
+  /* Part one: reasons to publish or not publish that aren't
+   * worth mentioning to the user, either because they're obvious
+   * or because they're normal behavior. */
+
+  if (!dir_port) /* short circuit the rest of the function */
+    return 0;
+  if (authdir_mode(options)) /* always publish */
+    return dir_port;
+  if (net_is_disabled())
+    return 0;
+  if (!check_whether_dirport_reachable())
+    return 0;
+  if (!router_get_advertised_dir_port(options, dir_port))
+    return 0;
+
+  /* Part two: reasons to publish or not publish that the user
+   * might find surprising. router_should_be_directory_server()
+   * considers config options that make us choose not to publish. */
+  return router_should_be_directory_server(options, dir_port) ? dir_port : 0;
 }
 
 /** Allocate and return a new extend_info_t that can be used to build
@@ -2642,6 +2673,10 @@ router_dump_router_to_string(routerinfo_t *router,
     tor_free(p6);
   }
 
+  if (dir_server_mode(options)) {
+    smartlist_add(chunks, tor_strdup("tunnelled-dir-server\n"));
+  }
+
   /* Sign the descriptor with Ed25519 */
   if (emit_ed_sigs)  {
     smartlist_add(chunks, tor_strdup("router-sig-ed25519 "));