Remove UseDirectoryGuards

It is obsoleted in an always-on direction by prop271.

changes/ticket20831

@@ -0,0 +1,6 @@
+  o Removed features:
+    - The NumDirectoryGuards and UseDirectoryGuards torrc options are
+      no longer present: all users that use entry guards will also use
+      directory guards. Related to proposal 271; implements part of
+      ticket 20831.
+

doc/tor.1.txt

@@ -1208,15 +1208,6 @@ The following options are useful only for clients (that is, if
     Authorities, Single Onion Services, and Tor2web clients. In these cases,
     the this option is ignored. (Default: 1)
 
-[[UseEntryGuardsAsDirGuards]] **UseEntryGuardsAsDirGuards** **0**|**1**::
-    If this option is set to 1, and UseEntryGuards is also set to 1,
-    we try to use our entry guards as directory
-    guards, and failing that, pick more nodes to act as our directory guards.
-    This helps prevent an adversary from enumerating clients. It's only
-    available for clients (non-relay, non-bridge) that aren't configured to
-    download any non-default directory material.  It doesn't currently
-    do anything when we lack a live consensus. (Default: 1)
-
 [[GuardfractionFile]] **GuardfractionFile** __FILENAME__::
     V3 authoritative directories only. Configures the location of the
     guardfraction file which contains information about how long relays

src/or/config.c

@@ -495,7 +495,7 @@ static config_var_t option_vars_[] = {
   V(UpdateBridgesFromAuthority,  BOOL,     "0"),
   V(UseBridges,                  BOOL,     "0"),
   VAR("UseEntryGuards",          BOOL,     UseEntryGuards_option, "1"),
-  V(UseEntryGuardsAsDirGuards,   BOOL,     "1"),
+  OBSOLETE("UseEntryGuardsAsDirGuards"),
   V(UseGuardFraction,            AUTOBOOL, "auto"),
   V(UseMicrodescriptors,         AUTOBOOL, "auto"),
   OBSOLETE("UseNTorHandshake"),

src/or/directory.c

@@ -442,10 +442,9 @@ should_use_directory_guards(const or_options_t *options)
   /* Public (non-bridge) servers never use directory guards. */
   if (public_server_mode(options))
     return 0;
-  /* If guards are disabled, or directory guards are disabled, we can't
-   * use directory guards.
+  /* If guards are disabled, we can't use directory guards.
    */
-  if (!options->UseEntryGuards || !options->UseEntryGuardsAsDirGuards)
+  if (!options->UseEntryGuards)
     return 0;
   /* If we're configured to fetch directory info aggressively or of a
    * nonstandard type, don't use directory guards. */

src/or/or.h

@@ -4070,8 +4070,6 @@ typedef struct {
   int UseEntryGuards;
 
   int NumEntryGuards; /**< How many entry guards do we try to establish? */
-  int UseEntryGuardsAsDirGuards; /** Boolean: Do we try to get directory info
-                                  * from a smallish number of fixed nodes? */
 
   /** If 1, we use any guardfraction information we see in the
    * consensus.  If 0, we don't.  If -1, let the consensus parameter

src/test/test_dir.c

@@ -4354,7 +4354,6 @@ test_dir_should_use_directory_guards(void *data)
   tt_int_op(should_use_directory_guards(options), OP_EQ, 0);
   tt_int_op(CALLED(public_server_mode), OP_EQ, 1);
 
-  options->UseEntryGuardsAsDirGuards = 1;
   options->UseEntryGuards = 1;
   options->DownloadExtraInfo = 0;
   options->FetchDirInfoEarly = 0;
@@ -4368,29 +4367,24 @@ test_dir_should_use_directory_guards(void *data)
   tt_int_op(CALLED(public_server_mode), OP_EQ, 3);
   options->UseEntryGuards = 1;
 
-  options->UseEntryGuardsAsDirGuards = 0;
-  tt_int_op(should_use_directory_guards(options), OP_EQ, 0);
-  tt_int_op(CALLED(public_server_mode), OP_EQ, 4);
-  options->UseEntryGuardsAsDirGuards = 1;
-
   options->DownloadExtraInfo = 1;
   tt_int_op(should_use_directory_guards(options), OP_EQ, 0);
-  tt_int_op(CALLED(public_server_mode), OP_EQ, 5);
+  tt_int_op(CALLED(public_server_mode), OP_EQ, 4);
   options->DownloadExtraInfo = 0;
 
   options->FetchDirInfoEarly = 1;
   tt_int_op(should_use_directory_guards(options), OP_EQ, 0);
-  tt_int_op(CALLED(public_server_mode), OP_EQ, 6);
+  tt_int_op(CALLED(public_server_mode), OP_EQ, 5);
   options->FetchDirInfoEarly = 0;
 
   options->FetchDirInfoExtraEarly = 1;
   tt_int_op(should_use_directory_guards(options), OP_EQ, 0);
-  tt_int_op(CALLED(public_server_mode), OP_EQ, 7);
+  tt_int_op(CALLED(public_server_mode), OP_EQ, 6);
   options->FetchDirInfoExtraEarly = 0;
 
   options->FetchUselessDescriptors = 1;
   tt_int_op(should_use_directory_guards(options), OP_EQ, 0);
-  tt_int_op(CALLED(public_server_mode), OP_EQ, 8);
+  tt_int_op(CALLED(public_server_mode), OP_EQ, 7);
   options->FetchUselessDescriptors = 0;
 
   done: