Only authorities should automatically download v2 networkstatus documents

Clients and relays haven't used them since early 0.2.0.x.  The only
remaining use by authorities learning about new relays ahead of scedule;
see proposal 147 for what we intend to do about that.

We're leaving in an option (FetchV2Networkstatus) to manually fetch v2
networkstatuses, because apparently dnsel and maybe bwauth want them.

This fixes bug 3022.

changes/bug3022

@@ -0,0 +1,6 @@
+  o Removed features
+    - Caches no longer download and serve v2 networkstatus documents
+      unless FetchV2Networkstatus flag is set: these documents haven't
+      haven't been used by clients or relays since 0.2.0.x.  Resolves
+      bug 3022.
+

doc/tor.1.txt

@@ -1171,6 +1171,12 @@ if DirPort is non-zero):
     Set an entrance policy for this server, to limit who can connect to the
     directory ports. The policies have the same form as exit policies above.
 
+**FetchV2Networkstatus** **0**|**1**::
+    If set, we try to fetch the (obsolete, unused) version 2 network status
+    consensus documents from the directory authorities. No currently
+    supported Tor version uses them.  (Default: 0.)
+
+
 DIRECTORY AUTHORITY SERVER OPTIONS
 ----------------------------------
 

src/or/config.c

@@ -255,6 +255,7 @@ static config_var_t _option_vars[] = {
   V(FetchServerDescriptors,      BOOL,     "1"),
   V(FetchHidServDescriptors,     BOOL,     "1"),
   V(FetchUselessDescriptors,     BOOL,     "0"),
+  V(FetchV2Networkstatus,        BOOL,     "0"),
 #ifdef WIN32
   V(GeoIPFile,                   FILENAME, "<default>"),
 #else

src/or/directory.c

@@ -353,6 +353,7 @@ directory_get_from_dirserver(uint8_t dir_purpose, uint8_t router_purpose,
       break;
     case DIR_PURPOSE_FETCH_V2_NETWORKSTATUS:
       type = V2_AUTHORITY;
+      prefer_authority = 1; /* Only v2 authorities have these anyway. */
       break;
     case DIR_PURPOSE_FETCH_SERVERDESC:
       type = (router_purpose == ROUTER_PURPOSE_BRIDGE ? BRIDGE_AUTHORITY :

src/or/networkstatus.c

@@ -1356,7 +1356,7 @@ update_networkstatus_downloads(time_t now)
   or_options_t *options = get_options();
   if (should_delay_dir_fetches(options))
     return;
-  if (directory_fetches_dir_info_early(options))
+  if (authdir_mode_any_main(options) || options->FetchV2Networkstatus)
     update_v2_networkstatus_cache_downloads(now);
   update_consensus_networkstatus_downloads(now);
   update_certificate_downloads(now);

src/or/or.h

@@ -2489,7 +2489,9 @@ typedef struct {
   /** Boolean: do we publish hidden service descriptors to the HS auths? */
   int PublishHidServDescriptors;
   int FetchServerDescriptors; /**< Do we fetch server descriptors as normal? */
-  int FetchHidServDescriptors; /** and hidden service descriptors? */
+  int FetchHidServDescriptors; /**< and hidden service descriptors? */
+  int FetchV2Networkstatus; /**< Do we fetch v2 networkstatus documents when
+                             * we don't need to? */
   int HidServDirectoryV2; /**< Do we participate in the HS DHT? */
 
   int MinUptimeHidServDirectoryV2; /**< As directory authority, accept hidden