Commit 1fc94bfd authored by Roger Dingledine's avatar Roger Dingledine
Browse files

spread guard rotation out throughout the month

parent 0642ab24

ChangeLog

+7 −0
Original line number Diff line number Diff line
@@ -8,6 +8,13 @@ Changes in version 0.2.1.23 - 2010-0?-?? 
      automatically discard guards picked using the old algorithm. Fixes

      bug 1217; bugfix on 0.2.1.3-alpha. Found by Mike Perry.



  o Minor features:

    - Avoid a mad rush at the beginning of each month when each client

      rotates half of its guards. Instead we spread the rotation out

      throughout the month, but we still avoid leaving a precise timestamp

      in the state file about when we first picked the guard. Improves

      over the behavior introduced in 0.1.2.17.





Changes in version 0.2.1.22 - 2010-01-19

  Tor 0.2.1.22 fixes a critical privacy problem in bridge directory

src/or/circuitbuild.c

+10 −20
Original line number Diff line number Diff line
@@ -58,7 +58,6 @@ static int count_acceptable_routers(smartlist_t *routers); 
static int onion_append_hop(crypt_path_t **head_ptr, extend_info_t *choice);



static void entry_guards_changed(void);

static time_t start_of_month(time_t when);



/** Iterate over values of circ_id, starting from conn-\>next_circ_id,

 * and with the high bit specified by conn-\>circ_id_type, until we get
@@ -2137,7 +2136,12 @@ add_an_entry_guard(routerinfo_t *chosen, int reset_status) 
  log_info(LD_CIRC, "Chose '%s' as new entry guard.", router->nickname);

  strlcpy(entry->nickname, router->nickname, sizeof(entry->nickname));

  memcpy(entry->identity, router->cache_info.identity_digest, DIGEST_LEN);

  entry->chosen_on_date = start_of_month(time(NULL));

  /* Choose expiry time smudged over the past month. The goal here

   * is to a) spread out when Tor clients rotate their guards, so they

   * don't all select them on the same day, and b) avoid leaving a

   * precise timestamp in the state file about when we first picked

   * this guard. For details, see the Jan 2010 or-dev thread. */

  entry->chosen_on_date = time(NULL) - crypto_rand_int(3600*24*30);

  entry->chosen_by_version = tor_strdup(VERSION);

  if (chosen) /* prepend */

    smartlist_insert(entry_guards, 0, entry);
@@ -2188,7 +2192,7 @@ static int 
remove_obsolete_entry_guards(void)

{

  int changed = 0, i;

  time_t this_month = start_of_month(time(NULL));

  time_t now = time(NULL);



  for (i = 0; i < smartlist_len(entry_guards); ++i) {

    entry_guard_t *entry = smartlist_get(entry_guards, i);
@@ -2220,9 +2224,8 @@ remove_obsolete_entry_guards(void) 
      }

      tor_free(tor_ver);

    }

    if (!version_is_bad && entry->chosen_on_date + 3600*24*35 < this_month) {

      /* It's been more than a month, and probably more like two since

       * chosen_on_date is clipped to the beginning of its month. */

    if (!version_is_bad && entry->chosen_on_date + 3600*24*60 < now) {

      /* It's been 2 months since the date listed in our state file. */

      msg = "was selected several months ago";

      date_is_bad = 1;

    }
@@ -2673,19 +2676,6 @@ choose_random_entry(cpath_build_state_t *state) 
  return r;

}



/** Helper: Return the start of the month containing <b>time</b>. */

static time_t

start_of_month(time_t now)

{

  struct tm tm;

  tor_gmtime_r(&now, &tm);

  tm.tm_sec = 0;

  tm.tm_min = 0;

  tm.tm_hour = 0;

  tm.tm_mday = 1;

  return tor_timegm(&tm);

}



/** Parse <b>state</b> and learn about the entry guards it describes.

 * If <b>set</b> is true, and there are no errors, replace the global

 * entry_list with what we find.
@@ -2794,7 +2784,7 @@ entry_guards_parse_state(or_state_t *state, int set, char **msg) 
     } else {

       if (state_version) {

         e->chosen_by_version = tor_strdup(state_version);

         e->chosen_on_date = start_of_month(time(NULL));

         e->chosen_on_date = time(NULL) - crypto_rand_int(3600*24*30);

       }

     }

   });