Split sampled_guards_update_from_consensus() into subfunctions

                                 DFLT_REMOVE_UNLISTED_GUARDS_AFTER_DAYS,

                                 1, 365*10);

}

/**

 * Return number of seconds that will make a guard no longer eligible

 * for selection if unlisted for this long.

 */

static time_t

get_remove_unlisted_guards_after_seconds(void)

{

  return get_remove_unlisted_guards_after_days() * 24 * 60 * 60;

}

/**

 * We remove unconfirmed guards from the sample after this many days,

 * regardless of whether they are listed or unlisted.

}

/**

 * Update the status of all sampled guards based on the arrival of a

 * new consensus networkstatus document.  This will include marking

 * some guards as listed or unlisted, and removing expired guards. */

STATIC void

sampled_guards_update_from_consensus(guard_selection_t *gs)

 * Enumerate <b>sampled_entry_guards</b> smartlist in <b>gs</b>.

 * For each <b>entry_guard_t</b> object in smartlist, do the following:

 *  * Update <b>currently_listed</b> field to reflect if guard is listed

 *    in guard selection <b>gs</b>.

 *  * Set <b>unlisted_since_date</b> to approximate UNIX time of

 *    unlisting if guard is unlisted (randomize within 20% of

 *    get_remove_unlisted_guards_after_seconds()). Otherwise,

 *    set it to 0.

 *

 * Require <b>gs</b> to be non-null pointer.

 * Return a number of entries updated.

 */

static size_t

sampled_guards_update_consensus_presence(guard_selection_t *gs)

{

  tor_assert(gs);

  const int REMOVE_UNLISTED_GUARDS_AFTER =

    (get_remove_unlisted_guards_after_days() * 86400);

  const int unlisted_since_slop = REMOVE_UNLISTED_GUARDS_AFTER / 5;

  size_t n_changes = 0;

  // It's important to use only a live consensus here; we don't want to

  // make changes based on anything expired or old.

  if (live_consensus_is_missing(gs)) {

    log_info(LD_GUARD, "Not updating the sample guard set; we have "

             "no live consensus.");

    return;

  }

  log_info(LD_GUARD, "Updating sampled guard status based on received "

           "consensus.");

  tor_assert(gs);

  int n_changes = 0;

  const time_t unlisted_since_slop =

    get_remove_unlisted_guards_after_seconds() /  5;

  /* First: Update listed/unlisted. */

  SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {

    /* XXXX #20827 check ed ID too */

    const int is_listed = entry_guard_is_listed(gs, guard);

    }

  } SMARTLIST_FOREACH_END(guard);

  const time_t remove_if_unlisted_since =

    approx_time() - REMOVE_UNLISTED_GUARDS_AFTER;

  const time_t maybe_remove_if_sampled_before =

    approx_time() - get_guard_lifetime();

  const time_t remove_if_confirmed_before =

    approx_time() - get_guard_confirmed_min_lifetime();

  return n_changes;

}

/**

 * Enumerate <b>sampled_entry_guards</b> smartlist in <b>gs</b>.

 * For each <b>entry_guard_t</b> object in smartlist, do the following:

 * * If <b>currently_listed</b> is false and <b>unlisted_since_date</b>

 *   is earlier than <b>remove_if_unlisted_since</b> - remove it.

 * * Otherwise, check if <b>sampled_on_date</b> is earlier than

 *   <b>maybe_remove_if_sampled_before</b>.

 *   * When above condition is correct, remove the guard if:

 *     * It was never confirmed.

 *     * It was confirmed before <b>remove_if_confirmed_before</b>.

 *

 * Require <b>gs</b> to be non-null pointer.

 * Return number of entries deleted.

 */

static size_t

sampled_guards_prune_obsolete_entries(guard_selection_t *gs,

                                  const time_t remove_if_unlisted_since,

                                  const time_t maybe_remove_if_sampled_before,

                                  const time_t remove_if_confirmed_before)

{

  size_t n_changes = 0;

  tor_assert(gs);

  /* Then: remove the ones that have been junk for too long */

  SMARTLIST_FOREACH_BEGIN(gs->sampled_entry_guards, entry_guard_t *, guard) {

    int rmv = 0;

        guard->unlisted_since_date < remove_if_unlisted_since) {

      /*

        "We have a live consensus, and {IS_LISTED} is false, and

         {FIRST_UNLISTED_AT} is over {REMOVE_UNLISTED_GUARDS_AFTER}

         {FIRST_UNLISTED_AT} is over get_remove_unlisted_guards_after_days()

         days in the past."

      */

      log_info(LD_GUARD, "Removing sampled guard %s: it has been unlisted "

    }

  } SMARTLIST_FOREACH_END(guard);

  return n_changes;

}

/**

 * Update the status of all sampled guards based on the arrival of a

 * new consensus networkstatus document.  This will include marking

 * some guards as listed or unlisted, and removing expired guards. */

STATIC void

sampled_guards_update_from_consensus(guard_selection_t *gs)

{

  tor_assert(gs);

  // It's important to use only a live consensus here; we don't want to

  // make changes based on anything expired or old.

  if (live_consensus_is_missing(gs)) {

    log_info(LD_GUARD, "Not updating the sample guard set; we have "

             "no live consensus.");

    return;

  }

  log_info(LD_GUARD, "Updating sampled guard status based on received "

           "consensus.");

  /* First: Update listed/unlisted. */

  size_t n_changes = sampled_guards_update_consensus_presence(gs);

  const time_t remove_if_unlisted_since =

    approx_time() - get_remove_unlisted_guards_after_seconds();

  const time_t maybe_remove_if_sampled_before =

    approx_time() - get_guard_lifetime();

  const time_t remove_if_confirmed_before =

    approx_time() - get_guard_confirmed_min_lifetime();

  /* Then: remove the ones that have been junk for too long */

  n_changes +=

    sampled_guards_prune_obsolete_entries(gs,

                                          remove_if_unlisted_since,

                                          maybe_remove_if_sampled_before,

                                          remove_if_confirmed_before);

  if (n_changes) {

    gs->primary_guards_up_to_date = 0;

    entry_guards_update_filtered_sets(gs);