tor/src/or/networkstatus.c

/* Copyright (c) 2001 Matej Pfajfar.
 * Copyright (c) 2001-2004, Roger Dingledine.
 * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
 * Copyright (c) 2007-2010, The Tor Project, Inc. */
/* See LICENSE for licensing information */

/**
 * \file networkstatus.c
 * \brief Functions and structures for handling network status documents as a
 * client or cache.
 */

#include "or.h"

/* For tracking v2 networkstatus documents.  Only caches do this now. */

/** Map from descriptor digest of routers listed in the v2 networkstatus
 * documents to download_status_t* */
static digestmap_t *v2_download_status_map = NULL;
/** Global list of all of the current v2 network_status documents that we know
 * about.  This list is kept sorted by published_on. */
static smartlist_t *networkstatus_v2_list = NULL;
/** True iff any member of networkstatus_v2_list has changed since the last
 * time we called download_status_map_update_from_v2_networkstatus() */
static int networkstatus_v2_list_has_changed = 0;

/** Map from lowercase nickname to identity digest of named server, if any. */
static strmap_t *named_server_map = NULL;
/** Map from lowercase nickname to (void*)1 for all names that are listed
 * as unnamed for some server in the consensus. */
static strmap_t *unnamed_server_map = NULL;

/** Most recently received and validated v3 consensus network status. */
static networkstatus_t *current_consensus = NULL;

/** A v3 consensus networkstatus that we've received, but which we don't
 * have enough certificates to be happy about. */
static networkstatus_t *consensus_waiting_for_certs = NULL;
/** The encoded version of consensus_waiting_for_certs. */
static char *consensus_waiting_for_certs_body = NULL;
/** When did we set the current value of consensus_waiting_for_certs?  If this
 * is too recent, we shouldn't try to fetch a new consensus for a little while,
 * to give ourselves time to get certificates for this one. */
static time_t consensus_waiting_for_certs_set_at = 0;
/** Set to 1 if we've been holding on to consensus_waiting_for_certs so long
 * that we should treat it as maybe being bad. */
static int consensus_waiting_for_certs_dl_failed = 0;

/** The last time we tried to download a networkstatus, or 0 for "never".  We
 * use this to rate-limit download attempts for directory caches (including
 * mirrors).  Clients don't use this now. */
static time_t last_networkstatus_download_attempted = 0;

/** A time before which we shouldn't try to replace the current consensus:
 * this will be at some point after the next consensus becomes valid, but
 * before the current consensus becomes invalid. */
static time_t time_to_download_next_consensus = 0;
/** Download status for the current consensus networkstatus. */
static download_status_t consensus_dl_status = { 0, 0, DL_SCHED_CONSENSUS };

/** True iff we have logged a warning about this OR's version being older than
 * listed by the authorities. */
static int have_warned_about_old_version = 0;
/** True iff we have logged a warning about this OR's version being newer than
 * listed by the authorities. */
static int have_warned_about_new_version = 0;

static void download_status_map_update_from_v2_networkstatus(void);
static void routerstatus_list_update_named_server_map(void);

/** Forget that we've warned about anything networkstatus-related, so we will
 * give fresh warnings if the same behavior happens again. */
void
networkstatus_reset_warnings(void)
{
  if (current_consensus) {
    SMARTLIST_FOREACH(current_consensus->routerstatus_list,
                      routerstatus_t *, rs,
                      rs->name_lookup_warned = 0);
  }

  have_warned_about_old_version = 0;
  have_warned_about_new_version = 0;
}

/** Reset the descriptor download failure count on all networkstatus docs, so
 * that we can retry any long-failed documents immediately.
 */
void
networkstatus_reset_download_failures(void)
{
  const smartlist_t *networkstatus_v2_list = networkstatus_get_v2_list();
  SMARTLIST_FOREACH(networkstatus_v2_list, networkstatus_v2_t *, ns,
     SMARTLIST_FOREACH(ns->entries, routerstatus_t *, rs,
       {
         if (!router_get_by_descriptor_digest(rs->descriptor_digest))
           rs->need_to_mirror = 1;
       }));;

  download_status_reset(&consensus_dl_status);
  if (v2_download_status_map) {
    digestmap_iter_t *iter;
    digestmap_t *map = v2_download_status_map;
    const char *key;
    void *val;
    download_status_t *dls;
    for (iter = digestmap_iter_init(map); !digestmap_iter_done(iter);
         iter = digestmap_iter_next(map, iter) ) {
      digestmap_iter_get(iter, &key, &val);
      dls = val;
      download_status_reset(dls);
    }
  }
}

/** Repopulate our list of network_status_t objects from the list cached on
 * disk.  Return 0 on success, -1 on failure. */
int
router_reload_v2_networkstatus(void)
{
  smartlist_t *entries;
  struct stat st;
  char *s;
  char *filename = get_datadir_fname("cached-status");
  int maybe_delete = !directory_caches_v2_dir_info(get_options());
  time_t now = time(NULL);
  if (!networkstatus_v2_list)
    networkstatus_v2_list = smartlist_create();

  entries = tor_listdir(filename);
  if (!entries) { /* dir doesn't exist */
    tor_free(filename);
    return 0;
  } else if (!smartlist_len(entries) && maybe_delete) {
    rmdir(filename);
    tor_free(filename);
    smartlist_free(entries);
    return 0;
  }
  tor_free(filename);
  SMARTLIST_FOREACH(entries, const char *, fn, {
      char buf[DIGEST_LEN];
      if (maybe_delete) {
        filename = get_datadir_fname2("cached-status", fn);
        remove_file_if_very_old(filename, now);
        tor_free(filename);
        continue;
      }
      if (strlen(fn) != HEX_DIGEST_LEN ||
          base16_decode(buf, sizeof(buf), fn, strlen(fn))) {
        log_info(LD_DIR,
                 "Skipping cached-status file with unexpected name \"%s\"",fn);
        continue;
      }
      filename = get_datadir_fname2("cached-status", fn);
      s = read_file_to_str(filename, 0, &st);
      if (s) {
        if (router_set_networkstatus_v2(s, st.st_mtime, NS_FROM_CACHE,
                                        NULL)<0) {
          log_warn(LD_FS, "Couldn't load networkstatus from \"%s\"",filename);
        }
        tor_free(s);
      }
      tor_free(filename);
    });
  SMARTLIST_FOREACH(entries, char *, fn, tor_free(fn));
  smartlist_free(entries);
  networkstatus_v2_list_clean(time(NULL));
  routers_update_all_from_networkstatus(time(NULL), 2);
  return 0;
}

/** Read the cached v3 consensus networkstatus from the disk. */
int
router_reload_consensus_networkstatus(void)
{
  char *filename;
  char *s;
  struct stat st;
  or_options_t *options = get_options();
  const unsigned int flags = NSSET_FROM_CACHE | NSSET_DONT_DOWNLOAD_CERTS;

  /* FFFF Suppress warnings if cached consensus is bad? */

  filename = get_datadir_fname("cached-consensus");
  s = read_file_to_str(filename, RFTS_IGNORE_MISSING, NULL);
  if (s) {
    if (networkstatus_set_current_consensus(s, flags) < -1) {
      log_warn(LD_FS, "Couldn't load consensus networkstatus from \"%s\"",
               filename);
    }
    tor_free(s);
  }
  tor_free(filename);

  filename = get_datadir_fname("unverified-consensus");
  s = read_file_to_str(filename, RFTS_IGNORE_MISSING, NULL);
  if (s) {
    if (networkstatus_set_current_consensus(s,
                                     flags|NSSET_WAS_WAITING_FOR_CERTS)) {
      log_info(LD_FS, "Couldn't load consensus networkstatus from \"%s\"",
               filename);
    }
    tor_free(s);
  }
  tor_free(filename);

  if (!current_consensus ||
      (stat(options->FallbackNetworkstatusFile, &st)==0 &&
       st.st_mtime > current_consensus->valid_after)) {
    s = read_file_to_str(options->FallbackNetworkstatusFile,
                         RFTS_IGNORE_MISSING, NULL);
    if (s) {
      if (networkstatus_set_current_consensus(s,
                                              flags|NSSET_ACCEPT_OBSOLETE)) {
        log_info(LD_FS, "Couldn't load consensus networkstatus from \"%s\"",
                 options->FallbackNetworkstatusFile);
      } else {
        log_notice(LD_FS,
                   "Loaded fallback consensus networkstatus from \"%s\"",
                   options->FallbackNetworkstatusFile);
      }
      tor_free(s);
    }
  }

  if (!current_consensus) {
    if (!named_server_map)
      named_server_map = strmap_new();
    if (!unnamed_server_map)
      unnamed_server_map = strmap_new();
  }

  update_certificate_downloads(time(NULL));

  routers_update_all_from_networkstatus(time(NULL), 3);

  return 0;
}

/** Free all storage held by the vote_routerstatus object <b>rs</b>. */
static void
vote_routerstatus_free(vote_routerstatus_t *rs)
{
  tor_free(rs->version);
  tor_free(rs->status.exitsummary);
  tor_free(rs);
}

/** Free all storage held by the routerstatus object <b>rs</b>. */
void
routerstatus_free(routerstatus_t *rs)
{
  tor_free(rs->exitsummary);
  tor_free(rs);
}

/** Free all storage held by the networkstatus object <b>ns</b>. */
void
networkstatus_v2_free(networkstatus_v2_t *ns)
{
  tor_free(ns->source_address);
  tor_free(ns->contact);
  if (ns->signing_key)
    crypto_free_pk_env(ns->signing_key);
  tor_free(ns->client_versions);
  tor_free(ns->server_versions);
  if (ns->entries) {
    SMARTLIST_FOREACH(ns->entries, routerstatus_t *, rs,
                      routerstatus_free(rs));
    smartlist_free(ns->entries);
  }
  tor_free(ns);
}

/** Clear all storage held in <b>ns</b>. */
void
networkstatus_vote_free(networkstatus_t *ns)
{
  if (!ns)
    return;

  tor_free(ns->client_versions);
  tor_free(ns->server_versions);
  if (ns->known_flags) {
    SMARTLIST_FOREACH(ns->known_flags, char *, c, tor_free(c));
    smartlist_free(ns->known_flags);
  }
  if (ns->net_params) {
    SMARTLIST_FOREACH(ns->net_params, char *, c, tor_free(c));
    smartlist_free(ns->net_params);
  }
  if (ns->supported_methods) {
    SMARTLIST_FOREACH(ns->supported_methods, char *, c, tor_free(c));
    smartlist_free(ns->supported_methods);
  }
  if (ns->voters) {
    SMARTLIST_FOREACH(ns->voters, networkstatus_voter_info_t *, voter,
    {
      tor_free(voter->nickname);
      tor_free(voter->address);
      tor_free(voter->contact);
      tor_free(voter->signature);
      tor_free(voter);
    });
    smartlist_free(ns->voters);
  }
  if (ns->cert)
    authority_cert_free(ns->cert);

  if (ns->routerstatus_list) {
    if (ns->type == NS_TYPE_VOTE || ns->type == NS_TYPE_OPINION) {
      SMARTLIST_FOREACH(ns->routerstatus_list, vote_routerstatus_t *, rs,
                        vote_routerstatus_free(rs));
    } else {
      SMARTLIST_FOREACH(ns->routerstatus_list, routerstatus_t *, rs,
                        routerstatus_free(rs));
    }

    smartlist_free(ns->routerstatus_list);
  }
  if (ns->desc_digest_map)
    digestmap_free(ns->desc_digest_map, NULL);

  memset(ns, 11, sizeof(*ns));
  tor_free(ns);
}

/** Return the voter info from <b>vote</b> for the voter whose identity digest
 * is <b>identity</b>, or NULL if no such voter is associated with
 * <b>vote</b>. */
networkstatus_voter_info_t *
networkstatus_get_voter_by_id(networkstatus_t *vote,
                              const char *identity)
{
  if (!vote || !vote->voters)
    return NULL;
  SMARTLIST_FOREACH(vote->voters, networkstatus_voter_info_t *, voter,
    if (!memcmp(voter->identity_digest, identity, DIGEST_LEN))
      return voter);
  return NULL;
}

/** Check whether the signature on <b>voter</b> is correctly signed by
 * the signing key of <b>cert</b>. Return -1 if <b>cert</b> doesn't match the
 * signing key; otherwise set the good_signature or bad_signature flag on
 * <b>voter</b>, and return 0. */
/* (private; exposed for testing.) */
int
networkstatus_check_voter_signature(networkstatus_t *consensus,
                                    networkstatus_voter_info_t *voter,
                                    authority_cert_t *cert)
{
  char d[DIGEST_LEN];
  char *signed_digest;
  size_t signed_digest_len;
  if (crypto_pk_get_digest(cert->signing_key, d)<0)
    return -1;
  if (memcmp(voter->signing_key_digest, d, DIGEST_LEN))
    return -1;
  signed_digest_len = crypto_pk_keysize(cert->signing_key);
  signed_digest = tor_malloc(signed_digest_len);
  if (crypto_pk_public_checksig(cert->signing_key,
                                signed_digest,
                                voter->signature,
                                voter->signature_len) != DIGEST_LEN ||
      memcmp(signed_digest, consensus->networkstatus_digest, DIGEST_LEN)) {
    log_warn(LD_DIR, "Got a bad signature on a networkstatus vote");
    voter->bad_signature = 1;
  } else {
    voter->good_signature = 1;
  }
  tor_free(signed_digest);
  return 0;
}

/** Given a v3 networkstatus consensus in <b>consensus</b>, check every
 * as-yet-unchecked signature on <b>consensus</b>.  Return 1 if there is a
 * signature from every recognized authority on it, 0 if there are
 * enough good signatures from recognized authorities on it, -1 if we might
 * get enough good signatures by fetching missing certificates, and -2
 * otherwise.  Log messages at INFO or WARN: if <b>warn</b> is over 1, warn
 * about every problem; if warn is at least 1, warn only if we can't get
 * enough signatures; if warn is negative, log nothing at all. */
int
networkstatus_check_consensus_signature(networkstatus_t *consensus,
                                        int warn)
{
  int n_good = 0;
  int n_missing_key = 0;
  int n_bad = 0;
  int n_unknown = 0;
  int n_no_signature = 0;
  int n_v3_authorities = get_n_authorities(V3_AUTHORITY);
  int n_required = n_v3_authorities/2 + 1;
  smartlist_t *need_certs_from = smartlist_create();
  smartlist_t *unrecognized = smartlist_create();
  smartlist_t *missing_authorities = smartlist_create();
  int severity;
  time_t now = time(NULL);

  tor_assert(consensus->type == NS_TYPE_CONSENSUS);

  SMARTLIST_FOREACH(consensus->voters, networkstatus_voter_info_t *, voter,
  {
    if (!voter->good_signature && !voter->bad_signature && voter->signature) {
      /* we can try to check the signature. */
      int is_v3_auth = trusteddirserver_get_by_v3_auth_digest(
                                          voter->identity_digest) != NULL;
      authority_cert_t *cert =
        authority_cert_get_by_digests(voter->identity_digest,
                                      voter->signing_key_digest);
      if (!is_v3_auth) {
        smartlist_add(unrecognized, voter);
        ++n_unknown;
        continue;
      } else if (!cert || cert->expires < now) {
        smartlist_add(need_certs_from, voter);
        ++n_missing_key;
        continue;
      }
      if (networkstatus_check_voter_signature(consensus, voter, cert) < 0) {
        smartlist_add(need_certs_from, voter);
        ++n_missing_key;
        continue;
      }
    }
    if (voter->good_signature)
      ++n_good;
    else if (voter->bad_signature)
      ++n_bad;
    else
      ++n_no_signature;
  });

  /* Now see whether we're missing any voters entirely. */
  SMARTLIST_FOREACH(router_get_trusted_dir_servers(),
                    trusted_dir_server_t *, ds,
    {
      if ((ds->type & V3_AUTHORITY) &&
          !networkstatus_get_voter_by_id(consensus, ds->v3_identity_digest))
        smartlist_add(missing_authorities, ds);
    });

  if (warn > 1 || (warn >= 0 && n_good < n_required))
    severity = LOG_WARN;
  else
    severity = LOG_INFO;

  if (warn >= 0) {
    SMARTLIST_FOREACH(unrecognized, networkstatus_voter_info_t *, voter,
      {
        log_info(LD_DIR, "Consensus includes unrecognized authority '%s' "
                 "at %s:%d (contact %s; identity %s)",
                 voter->nickname, voter->address, (int)voter->dir_port,
                 voter->contact?voter->contact:"n/a",
                 hex_str(voter->identity_digest, DIGEST_LEN));
      });
    SMARTLIST_FOREACH(need_certs_from, networkstatus_voter_info_t *, voter,
      {
        log_info(LD_DIR, "Looks like we need to download a new certificate "
                 "from authority '%s' at %s:%d (contact %s; identity %s)",
                 voter->nickname, voter->address, (int)voter->dir_port,
                 voter->contact?voter->contact:"n/a",
                 hex_str(voter->identity_digest, DIGEST_LEN));
      });
    SMARTLIST_FOREACH(missing_authorities, trusted_dir_server_t *, ds,
      {
        log_info(LD_DIR, "Consensus does not include configured "
                 "authority '%s' at %s:%d (identity %s)",
                 ds->nickname, ds->address, (int)ds->dir_port,
                 hex_str(ds->v3_identity_digest, DIGEST_LEN));
      });
    log(severity, LD_DIR,
        "%d unknown, %d missing key, %d good, %d bad, %d no signature, "
        "%d required", n_unknown, n_missing_key, n_good, n_bad,
        n_no_signature, n_required);
  }

  smartlist_free(unrecognized);
  smartlist_free(need_certs_from);
  smartlist_free(missing_authorities);

  if (n_good == n_v3_authorities)
    return 1;
  else if (n_good >= n_required)
    return 0;
  else if (n_good + n_missing_key >= n_required)
    return -1;
  else
    return -2;
}

/** Helper: return a newly allocated string containing the name of the filename
 * where we plan to cache the network status with the given identity digest. */
char *
networkstatus_get_cache_filename(const char *identity_digest)
{
  char fp[HEX_DIGEST_LEN+1];
  base16_encode(fp, HEX_DIGEST_LEN+1, identity_digest, DIGEST_LEN);
  return get_datadir_fname2("cached-status", fp);
}

/** Helper for smartlist_sort: Compare two networkstatus objects by
 * publication date. */
static int
_compare_networkstatus_v2_published_on(const void **_a, const void **_b)
{
  const networkstatus_v2_t *a = *_a, *b = *_b;
  if (a->published_on < b->published_on)
    return -1;
  else if (a->published_on > b->published_on)
    return 1;
  else
    return 0;
}

/** Add the parsed v2 networkstatus in <b>ns</b> (with original document in
 * <b>s</b>) to the disk cache (and the in-memory directory server cache) as
 * appropriate. */
static int
add_networkstatus_to_cache(const char *s,
                           v2_networkstatus_source_t source,
                           networkstatus_v2_t *ns)
{
  if (source != NS_FROM_CACHE) {
    char *fn = networkstatus_get_cache_filename(ns->identity_digest);
    if (write_str_to_file(fn, s, 0)<0) {
      log_notice(LD_FS, "Couldn't write cached network status to \"%s\"", fn);
    }
    tor_free(fn);
  }

  if (directory_caches_v2_dir_info(get_options()))
    dirserv_set_cached_networkstatus_v2(s,
                                        ns->identity_digest,
                                        ns->published_on);

  return 0;
}

/** How far in the future do we allow a network-status to get before removing
 * it? (seconds) */
#define NETWORKSTATUS_ALLOW_SKEW (24*60*60)

/** Given a string <b>s</b> containing a network status that we received at
 * <b>arrived_at</b> from <b>source</b>, try to parse it, see if we want to
 * store it, and put it into our cache as necessary.
 *
 * If <b>source</b> is NS_FROM_DIR or NS_FROM_CACHE, do not replace our
 * own networkstatus_t (if we're an authoritative directory server).
 *
 * If <b>source</b> is NS_FROM_CACHE, do not write our networkstatus_t to the
 * cache.
 *
 * If <b>requested_fingerprints</b> is provided, it must contain a list of
 * uppercased identity fingerprints.  Do not update any networkstatus whose
 * fingerprint is not on the list; after updating a networkstatus, remove its
 * fingerprint from the list.
 *
 * Return 0 on success, -1 on failure.
 *
 * Callers should make sure that routers_update_all_from_networkstatus() is
 * invoked after this function succeeds.
 */
int
router_set_networkstatus_v2(const char *s, time_t arrived_at,
                            v2_networkstatus_source_t source,
                            smartlist_t *requested_fingerprints)
{
  networkstatus_v2_t *ns;
  int i, found;
  time_t now;
  int skewed = 0;
  trusted_dir_server_t *trusted_dir = NULL;
  const char *source_desc = NULL;
  char fp[HEX_DIGEST_LEN+1];
  char published[ISO_TIME_LEN+1];

  if (!directory_caches_v2_dir_info(get_options()))
    return 0; /* Don't bother storing it. */

  ns = networkstatus_v2_parse_from_string(s);
  if (!ns) {
    log_warn(LD_DIR, "Couldn't parse network status.");
    return -1;
  }
  base16_encode(fp, HEX_DIGEST_LEN+1, ns->identity_digest, DIGEST_LEN);
  if (!(trusted_dir =
        router_get_trusteddirserver_by_digest(ns->identity_digest)) ||
      !(trusted_dir->type & V2_AUTHORITY)) {
    log_info(LD_DIR, "Network status was signed, but not by an authoritative "
             "directory we recognize.");
    source_desc = fp;
  } else {
    source_desc = trusted_dir->description;
  }
  now = time(NULL);
  if (arrived_at > now)
    arrived_at = now;

  ns->received_on = arrived_at;

  format_iso_time(published, ns->published_on);

  if (ns->published_on > now + NETWORKSTATUS_ALLOW_SKEW) {
    char dbuf[64];
    long delta = now - ns->published_on;
    format_time_interval(dbuf, sizeof(dbuf), delta);
    log_warn(LD_GENERAL, "Network status from %s was published %s in the "
             "future (%s GMT). Check your time and date settings! "
             "Not caching.",
             source_desc, dbuf, published);
    control_event_general_status(LOG_WARN,
                       "CLOCK_SKEW MIN_SKEW=%ld SOURCE=NETWORKSTATUS:%s:%d",
                       delta, ns->source_address, ns->source_dirport);
    skewed = 1;
  }

  if (!networkstatus_v2_list)
    networkstatus_v2_list = smartlist_create();

  if ( (source == NS_FROM_DIR_BY_FP || source == NS_FROM_DIR_ALL) &&
       router_digest_is_me(ns->identity_digest)) {
    /* Don't replace our own networkstatus when we get it from somebody else.*/
    networkstatus_v2_free(ns);
    return 0;
  }

  if (requested_fingerprints) {
    if (smartlist_string_isin(requested_fingerprints, fp)) {
      smartlist_string_remove(requested_fingerprints, fp);
    } else {
      if (source != NS_FROM_DIR_ALL) {
        char *requested =
          smartlist_join_strings(requested_fingerprints," ",0,NULL);
        log_warn(LD_DIR,
               "We received a network status with a fingerprint (%s) that we "
               "never requested. (We asked for: %s.) Dropping.",
               fp, requested);
        tor_free(requested);
        return 0;
      }
    }
  }

  if (!trusted_dir) {
    if (!skewed) {
      /* We got a non-trusted networkstatus, and we're a directory cache.
       * This means that we asked an authority, and it told us about another
       * authority we didn't recognize. */
      log_info(LD_DIR,
               "We do not recognize authority (%s) but we are willing "
               "to cache it.", fp);
      add_networkstatus_to_cache(s, source, ns);
      networkstatus_v2_free(ns);
    }
    return 0;
  }

  found = 0;
  for (i=0; i < smartlist_len(networkstatus_v2_list); ++i) {
    networkstatus_v2_t *old_ns = smartlist_get(networkstatus_v2_list, i);

    if (!memcmp(old_ns->identity_digest, ns->identity_digest, DIGEST_LEN)) {
      if (!memcmp(old_ns->networkstatus_digest,
                  ns->networkstatus_digest, DIGEST_LEN)) {
        /* Same one we had before. */
        networkstatus_v2_free(ns);
        tor_assert(trusted_dir);
        log_info(LD_DIR,
                 "Not replacing network-status from %s (published %s); "
                 "we already have it.",
                 trusted_dir->description, published);
        if (old_ns->received_on < arrived_at) {
          if (source != NS_FROM_CACHE) {
            char *fn;
            fn = networkstatus_get_cache_filename(old_ns->identity_digest);
            /* We use mtime to tell when it arrived, so update that. */
            touch_file(fn);
            tor_free(fn);
          }
          old_ns->received_on = arrived_at;
        }
        download_status_failed(&trusted_dir->v2_ns_dl_status, 0);
        return 0;
      } else if (old_ns->published_on >= ns->published_on) {
        char old_published[ISO_TIME_LEN+1];
        format_iso_time(old_published, old_ns->published_on);
        tor_assert(trusted_dir);
        log_info(LD_DIR,
                 "Not replacing network-status from %s (published %s);"
                 " we have a newer one (published %s) for this authority.",
                 trusted_dir->description, published,
                 old_published);
        networkstatus_v2_free(ns);
        download_status_failed(&trusted_dir->v2_ns_dl_status, 0);
        return 0;
      } else {
        networkstatus_v2_free(old_ns);
        smartlist_set(networkstatus_v2_list, i, ns);
        found = 1;
        break;
      }
    }
  }

  if (source != NS_FROM_CACHE && trusted_dir) {
    download_status_reset(&trusted_dir->v2_ns_dl_status);
  }

  if (!found)
    smartlist_add(networkstatus_v2_list, ns);

/** Retain any routerinfo mentioned in a V2 networkstatus for at least this
 * long. */
#define V2_NETWORKSTATUS_ROUTER_LIFETIME (3*60*60)

  {
    time_t live_until = ns->published_on + V2_NETWORKSTATUS_ROUTER_LIFETIME;
    SMARTLIST_FOREACH(ns->entries, routerstatus_t *, rs,
    {
      signed_descriptor_t *sd =
        router_get_by_descriptor_digest(rs->descriptor_digest);
      if (sd) {
        if (sd->last_listed_as_valid_until < live_until)
          sd->last_listed_as_valid_until = live_until;
      } else {
        rs->need_to_mirror = 1;
      }
    });
  }

  log_info(LD_DIR, "Setting networkstatus %s %s (published %s)",
           source == NS_FROM_CACHE?"cached from":
           ((source == NS_FROM_DIR_BY_FP || source == NS_FROM_DIR_ALL) ?
             "downloaded from":"generated for"),
           trusted_dir->description, published);
  networkstatus_v2_list_has_changed = 1;

  smartlist_sort(networkstatus_v2_list,
                 _compare_networkstatus_v2_published_on);

  if (!skewed)
    add_networkstatus_to_cache(s, source, ns);

  return 0;
}

/** Remove all very-old network_status_t objects from memory and from the
 * disk cache. */
void
networkstatus_v2_list_clean(time_t now)
{
  int i;
  if (!networkstatus_v2_list)
    return;

  for (i = 0; i < smartlist_len(networkstatus_v2_list); ++i) {
    networkstatus_v2_t *ns = smartlist_get(networkstatus_v2_list, i);
    char *fname = NULL;
    if (ns->published_on + MAX_NETWORKSTATUS_AGE > now)
      continue;
    /* Okay, this one is too old.  Remove it from the list, and delete it
     * from the cache. */
    smartlist_del(networkstatus_v2_list, i--);
    fname = networkstatus_get_cache_filename(ns->identity_digest);
    if (file_status(fname) == FN_FILE) {
      log_info(LD_DIR, "Removing too-old networkstatus in %s", fname);
      unlink(fname);
    }
    tor_free(fname);
    if (directory_caches_v2_dir_info(get_options())) {
      dirserv_set_cached_networkstatus_v2(NULL, ns->identity_digest, 0);
    }
    networkstatus_v2_free(ns);
  }

  /* And now go through the directory cache for any cached untrusted
   * networkstatuses and other network info. */
  dirserv_clear_old_networkstatuses(now - MAX_NETWORKSTATUS_AGE);
  dirserv_clear_old_v1_info(now);
}

/** Helper for bsearching a list of routerstatus_t pointers: compare a
 * digest in the key to the identity digest of a routerstatus_t. */
static int
_compare_digest_to_routerstatus_entry(const void *_key, const void **_member)
{
  const char *key = _key;
  const routerstatus_t *rs = *_member;
  return memcmp(key, rs->identity_digest, DIGEST_LEN);
}

/** Return the entry in <b>ns</b> for the identity digest <b>digest</b>, or
 * NULL if none was found. */
routerstatus_t *
networkstatus_v2_find_entry(networkstatus_v2_t *ns, const char *digest)
{
  return smartlist_bsearch(ns->entries, digest,
                           _compare_digest_to_routerstatus_entry);
}

/** Return the entry in <b>ns</b> for the identity digest <b>digest</b>, or
 * NULL if none was found. */
routerstatus_t *
networkstatus_vote_find_entry(networkstatus_t *ns, const char *digest)
{
  return smartlist_bsearch(ns->routerstatus_list, digest,
                           _compare_digest_to_routerstatus_entry);
}

/*XXXX make this static once functions are moved into this file. */
/** Search the routerstatuses in <b>ns</b> for one whose identity digest is
 * <b>digest</b>.  Return value and set *<b>found_out</b> as for
 * smartlist_bsearch_idx(). */
int
networkstatus_vote_find_entry_idx(networkstatus_t *ns,
                                  const char *digest, int *found_out)
{
  return smartlist_bsearch_idx(ns->routerstatus_list, digest,
                               _compare_digest_to_routerstatus_entry,
                               found_out);
}

/** Return a list of the v2 networkstatus documents. */
const smartlist_t *
networkstatus_get_v2_list(void)
{
  if (!networkstatus_v2_list)
    networkstatus_v2_list = smartlist_create();
  return networkstatus_v2_list;
}

/** Return the consensus view of the status of the router whose current
 * <i>descriptor</i> digest is <b>digest</b>, or NULL if no such router is
 * known. */
routerstatus_t *
router_get_consensus_status_by_descriptor_digest(const char *digest)
{
  if (!current_consensus) return NULL;
  if (!current_consensus->desc_digest_map) {
    digestmap_t * m = current_consensus->desc_digest_map = digestmap_new();
    SMARTLIST_FOREACH(current_consensus->routerstatus_list,
                      routerstatus_t *, rs,
     {
       digestmap_set(m, rs->descriptor_digest, rs);
     });
  }
  return digestmap_get(current_consensus->desc_digest_map, digest);
}

/** Given the digest of a router descriptor, return its current download
 * status, or NULL if the digest is unrecognized. */
download_status_t *
router_get_dl_status_by_descriptor_digest(const char *d)
{
  routerstatus_t *rs;
  if ((rs = router_get_consensus_status_by_descriptor_digest(d)))
    return &rs->dl_status;
  if (v2_download_status_map)
    return digestmap_get(v2_download_status_map, d);

  return NULL;
}

/** Return the consensus view of the status of the router whose identity
 * digest is <b>digest</b>, or NULL if we don't know about any such router. */
routerstatus_t *
router_get_consensus_status_by_id(const char *digest)
{
  if (!current_consensus)
    return NULL;
  return smartlist_bsearch(current_consensus->routerstatus_list, digest,
                           _compare_digest_to_routerstatus_entry);
}

/** Given a nickname (possibly verbose, possibly a hexadecimal digest), return
 * the corresponding routerstatus_t, or NULL if none exists.  Warn the
 * user if <b>warn_if_unnamed</b> is set, and they have specified a router by
 * nickname, but the Named flag isn't set for that router. */
routerstatus_t *
router_get_consensus_status_by_nickname(const char *nickname,
                                        int warn_if_unnamed)
{
  char digest[DIGEST_LEN];
  routerstatus_t *best=NULL;
  smartlist_t *matches=NULL;
  const char *named_id=NULL;

  if (!current_consensus || !nickname)
    return NULL;

  /* Is this name really a hexadecimal identity digest? */
  if (nickname[0] == '$') {
    if (base16_decode(digest, DIGEST_LEN, nickname+1, strlen(nickname+1))<0)
      return NULL;
    return networkstatus_vote_find_entry(current_consensus, digest);
  } else if (strlen(nickname) == HEX_DIGEST_LEN &&
       (base16_decode(digest, DIGEST_LEN, nickname, strlen(nickname))==0)) {
    return networkstatus_vote_find_entry(current_consensus, digest);
  }

  /* Is there a server that is Named with this name? */
  if (named_server_map)
    named_id = strmap_get_lc(named_server_map, nickname);
  if (named_id)
    return networkstatus_vote_find_entry(current_consensus, named_id);

  /* Okay; is this name listed as Unnamed? */
  if (unnamed_server_map &&
      strmap_get_lc(unnamed_server_map, nickname)) {
    log_info(LD_GENERAL, "The name %s is listed as Unnamed; it is not the "
             "canonical name of any server we know.", escaped(nickname));
    return NULL;
  }

  /* This name is not canonical for any server; go through the list and
   * see who it matches. */
  /*XXXX This is inefficient; optimize it if it matters. */
  matches = smartlist_create();
  SMARTLIST_FOREACH(current_consensus->routerstatus_list,
                    routerstatus_t *, lrs,
    {
      if (!strcasecmp(lrs->nickname, nickname)) {
        if (lrs->is_named) {
          tor_fragile_assert() /* This should never happen. */
          smartlist_free(matches);
          return lrs;
        } else {
          if (lrs->is_unnamed) {
            tor_fragile_assert(); /* nor should this. */
            smartlist_clear(matches);
            best=NULL;
            break;
          }
          smartlist_add(matches, lrs);
          best = lrs;
        }
      }
    });

  if (smartlist_len(matches)>1 && warn_if_unnamed) {
    int any_unwarned=0;
    SMARTLIST_FOREACH(matches, routerstatus_t *, lrs,
      {
        if (! lrs->name_lookup_warned) {
          lrs->name_lookup_warned=1;
          any_unwarned=1;
        }
      });
    if (any_unwarned) {
      log_warn(LD_CONFIG,"There are multiple matches for the nickname \"%s\","
               " but none is listed as named by the directory authorities. "
               "Choosing one arbitrarily.", nickname);
    }
  } else if (warn_if_unnamed && best && !best->name_lookup_warned) {
    char fp[HEX_DIGEST_LEN+1];
    base16_encode(fp, sizeof(fp),
                  best->identity_digest, DIGEST_LEN);
    log_warn(LD_CONFIG,
         "When looking up a status, you specified a server \"%s\" by name, "
         "but the directory authorities do not have any key registered for "
         "this nickname -- so it could be used by any server, "
         "not just the one you meant. "
         "To make sure you get the same server in the future, refer to "
         "it by key, as \"$%s\".", nickname, fp);
    best->name_lookup_warned = 1;
  }
  smartlist_free(matches);
  return best;
}

/** Return the identity digest that's mapped to officially by
 * <b>nickname</b>. */
const char *
networkstatus_get_router_digest_by_nickname(const char *nickname)
{
  if (!named_server_map)
    return NULL;
  return strmap_get_lc(named_server_map, nickname);
}

/** Return true iff <b>nickname</b> is disallowed from being the nickname
 * of any server. */
int
networkstatus_nickname_is_unnamed(const char *nickname)
{
  if (!unnamed_server_map)
    return 0;
  return strmap_get_lc(unnamed_server_map, nickname) != NULL;
}

/** How frequently do directory authorities re-download fresh networkstatus
 * documents? */
#define AUTHORITY_NS_CACHE_INTERVAL (10*60)

/** How frequently do non-authority directory caches re-download fresh
 * networkstatus documents? */
#define NONAUTHORITY_NS_CACHE_INTERVAL (60*60)

/** We are a directory server, and so cache network_status documents.
 * Initiate downloads as needed to update them.  For v2 authorities,
 * this means asking each trusted directory for its network-status.
 * For caches, this means asking a random v2 authority for all
 * network-statuses.
 */
static void
update_v2_networkstatus_cache_downloads(time_t now)
{
  int authority = authdir_mode_v2(get_options());
  int interval =
    authority ? AUTHORITY_NS_CACHE_INTERVAL : NONAUTHORITY_NS_CACHE_INTERVAL;
  const smartlist_t *trusted_dir_servers = router_get_trusted_dir_servers();

  if (last_networkstatus_download_attempted + interval >= now)
    return;

  last_networkstatus_download_attempted = now;

  if (authority) {
    /* An authority launches a separate connection for everybody. */
    SMARTLIST_FOREACH_BEGIN(trusted_dir_servers, trusted_dir_server_t *, ds)
      {
         char resource[HEX_DIGEST_LEN+6]; /* fp/hexdigit.z\0 */
         tor_addr_t addr;
         if (!(ds->type & V2_AUTHORITY))
           continue;
         if (router_digest_is_me(ds->digest))
           continue;
         tor_addr_from_ipv4h(&addr, ds->addr);
         /* Is this quite sensible with IPv6 or multiple addresses? */
         if (connection_get_by_type_addr_port_purpose(
                CONN_TYPE_DIR, &addr, ds->dir_port,
                DIR_PURPOSE_FETCH_V2_NETWORKSTATUS)) {
           /* XXX the above dir_port won't be accurate if we're
            * doing a tunneled conn. In that case it should be or_port.
            * How to guess from here? Maybe make the function less general
            * and have it know that it's looking for dir conns. -RD */
           /* Only directory caches download v2 networkstatuses, and they
            * don't use tunneled connections.  I think it's okay to ignore
            * this. */
           continue;
         }
         strlcpy(resource, "fp/", sizeof(resource));
         base16_encode(resource+3, sizeof(resource)-3, ds->digest, DIGEST_LEN);
         strlcat(resource, ".z", sizeof(resource));
         directory_initiate_command_routerstatus(
               &ds->fake_status, DIR_PURPOSE_FETCH_V2_NETWORKSTATUS,
               ROUTER_PURPOSE_GENERAL,
               0, /* Not private */
               resource,
               NULL, 0 /* No payload. */,
               0 /* No I-M-S. */);
      }
    SMARTLIST_FOREACH_END(ds);
  } else {
    /* A non-authority cache launches one connection to a random authority. */
    /* (Check whether we're currently fetching network-status objects.) */
    if (!connection_get_by_type_purpose(CONN_TYPE_DIR,
                                        DIR_PURPOSE_FETCH_V2_NETWORKSTATUS))
      directory_get_from_dirserver(DIR_PURPOSE_FETCH_V2_NETWORKSTATUS,
                                   ROUTER_PURPOSE_GENERAL, "all.z",
                                   PDS_RETRY_IF_NO_SERVERS);
  }
}

/** How many times will we try to fetch a consensus before we give up? */
#define CONSENSUS_NETWORKSTATUS_MAX_DL_TRIES 8
/** How long will we hang onto a possibly live consensus for which we're
 * fetching certs before we check whether there is a better one? */
#define DELAY_WHILE_FETCHING_CERTS (20*60)

/** If we want to download a fresh consensus, launch a new download as
 * appropriate. */
static void
update_consensus_networkstatus_downloads(time_t now)
{
  or_options_t *options = get_options();
  if (!networkstatus_get_live_consensus(now))
    time_to_download_next_consensus = now; /* No live consensus? Get one now!*/
  if (time_to_download_next_consensus > now)
    return; /* Wait until the current consensus is older. */
  if (authdir_mode_v3(options))
    return; /* Authorities never fetch a consensus */
  if (!download_status_is_ready(&consensus_dl_status, now,
                                CONSENSUS_NETWORKSTATUS_MAX_DL_TRIES))
    return; /* We failed downloading a consensus too recently. */
  if (connection_get_by_type_purpose(CONN_TYPE_DIR,
                                     DIR_PURPOSE_FETCH_CONSENSUS))
    return; /* There's an in-progress download.*/

  if (consensus_waiting_for_certs) {
    /* XXXX make sure this doesn't delay sane downloads. */
    if (consensus_waiting_for_certs_set_at + DELAY_WHILE_FETCHING_CERTS > now)
      return; /* We're still getting certs for this one. */
    else {
      if (!consensus_waiting_for_certs_dl_failed) {
        download_status_failed(&consensus_dl_status, 0);
        consensus_waiting_for_certs_dl_failed=1;
      }
    }
  }

  log_info(LD_DIR, "Launching networkstatus consensus download.");
  directory_get_from_dirserver(DIR_PURPOSE_FETCH_CONSENSUS,
                               ROUTER_PURPOSE_GENERAL, NULL,
                               PDS_RETRY_IF_NO_SERVERS);
}

/** Called when an attempt to download a consensus fails: note that the
 * failure occurred, and possibly retry. */
void
networkstatus_consensus_download_failed(int status_code)
{
  download_status_failed(&consensus_dl_status, status_code);
  /* Retry immediately, if appropriate. */
  update_consensus_networkstatus_downloads(time(NULL));
}

/** How long do we (as a cache) wait after a consensus becomes non-fresh
 * before trying to fetch another? */
#define CONSENSUS_MIN_SECONDS_BEFORE_CACHING 120

/** Update the time at which we'll consider replacing the current
 * consensus. */
void
update_consensus_networkstatus_fetch_time(time_t now)
{
  or_options_t *options = get_options();
  networkstatus_t *c = networkstatus_get_live_consensus(now);
  if (c) {
    long dl_interval;
    long interval = c->fresh_until - c->valid_after;
    time_t start;
    if (directory_fetches_dir_info_early(options)) {
      /* We want to cache the next one at some point after this one
       * is no longer fresh... */
      start = c->fresh_until + CONSENSUS_MIN_SECONDS_BEFORE_CACHING;
      /* But only in the first half-interval after that. */
      dl_interval = interval/2;
    } else {
      /* We're an ordinary client or a bridge. Give all the caches enough
       * time to download the consensus. */
      start = c->fresh_until + (interval*3)/4;
      /* But download the next one well before this one is expired. */
      dl_interval = ((c->valid_until - start) * 7 )/ 8;

      /* If we're a bridge user, make use of the numbers we just computed
       * to choose the rest of the interval *after* them. */
      if (directory_fetches_dir_info_later(options)) {
        /* Give all the *clients* enough time to download the consensus. */
        start = start + dl_interval + CONSENSUS_MIN_SECONDS_BEFORE_CACHING;
        /* But try to get it before ours actually expires. */
        dl_interval = (c->valid_until - start) -
                      CONSENSUS_MIN_SECONDS_BEFORE_CACHING;
      }
    }
    if (dl_interval < 1)
      dl_interval = 1;
    /* We must not try to replace c while it's still the most valid: */
    tor_assert(c->fresh_until < start);
    /* We must download the next one before c is invalid: */
    tor_assert(start+dl_interval < c->valid_until);
    time_to_download_next_consensus = start +crypto_rand_int((int)dl_interval);
    {
      char tbuf1[ISO_TIME_LEN+1];
      char tbuf2[ISO_TIME_LEN+1];
      char tbuf3[ISO_TIME_LEN+1];
      format_local_iso_time(tbuf1, c->fresh_until);
      format_local_iso_time(tbuf2, c->valid_until);
      format_local_iso_time(tbuf3, time_to_download_next_consensus);
      log_info(LD_DIR, "Live consensus %s the most recent until %s and will "
               "expire at %s; fetching the next one at %s.",
               (c->fresh_until > now) ? "will be" : "was",
               tbuf1, tbuf2, tbuf3);
    }
  } else {
    time_to_download_next_consensus = now;
    log_info(LD_DIR, "No live consensus; we should fetch one immediately.");
  }

}

/** Return 1 if there's a reason we shouldn't try any directory
 * fetches yet (e.g. we demand bridges and none are yet known).
 * Else return 0. */
int
should_delay_dir_fetches(or_options_t *options)
{
  if (options->UseBridges && !any_bridge_descriptors_known()) {
    log_info(LD_DIR, "delaying dir fetches (no running bridges known)");
    return 1;
  }
  return 0;
}

/** Launch requests for networkstatus documents and authority certificates as
 * appropriate. */
void
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))
    update_v2_networkstatus_cache_downloads(now);
  update_consensus_networkstatus_downloads(now);
  update_certificate_downloads(now);
}

/** Launch requests as appropriate for missing directory authority
 * certificates. */
void
update_certificate_downloads(time_t now)
{
  if (consensus_waiting_for_certs)
    authority_certs_fetch_missing(consensus_waiting_for_certs, now);
  else
    authority_certs_fetch_missing(current_consensus, now);
}

/** Return 1 if we have a consensus but we don't have enough certificates
 * to start using it yet. */
int
consensus_is_waiting_for_certs(void)
{
  return consensus_waiting_for_certs ? 1 : 0;
}

/** Return the network status with a given identity digest. */
networkstatus_v2_t *
networkstatus_v2_get_by_digest(const char *digest)
{
  SMARTLIST_FOREACH(networkstatus_v2_list, networkstatus_v2_t *, ns,
    {
      if (!memcmp(ns->identity_digest, digest, DIGEST_LEN))
        return ns;
    });
  return NULL;
}

/** Return the most recent consensus that we have downloaded, or NULL if we
 * don't have one. */
networkstatus_t *
networkstatus_get_latest_consensus(void)
{
  return current_consensus;
}

/** Return the most recent consensus that we have downloaded, or NULL if it is
 * no longer live. */
networkstatus_t *
networkstatus_get_live_consensus(time_t now)
{
  if (current_consensus &&
      current_consensus->valid_after <= now &&
      now <= current_consensus->valid_until)
    return current_consensus;
  else
    return NULL;
}

/* XXXX remove this in favor of get_live_consensus. But actually,
 * leave something like it for bridge users, who need to not totally
 * lose if they spend a while fetching a new consensus. */
/** As networkstatus_get_live_consensus(), but is way more tolerant of expired
 * consensuses. */
networkstatus_t *
networkstatus_get_reasonably_live_consensus(time_t now)
{
#define REASONABLY_LIVE_TIME (24*60*60)
  if (current_consensus &&
      current_consensus->valid_after <= now &&
      now <= current_consensus->valid_until+REASONABLY_LIVE_TIME)
    return current_consensus;
  else
    return NULL;
}

/** Given two router status entries for the same router identity, return 1 if
 * if the contents have changed between them. Otherwise, return 0. */
static int
routerstatus_has_changed(const routerstatus_t *a, const routerstatus_t *b)
{
  tor_assert(!memcmp(a->identity_digest, b->identity_digest, DIGEST_LEN));

  return strcmp(a->nickname, b->nickname) ||
         memcmp(a->descriptor_digest, b->descriptor_digest, DIGEST_LEN) ||
         a->addr != b->addr ||
         a->or_port != b->or_port ||
         a->dir_port != b->dir_port ||
         a->is_authority != b->is_authority ||
         a->is_exit != b->is_exit ||
         a->is_stable != b->is_stable ||
         a->is_fast != b->is_fast ||
         a->is_running != b->is_running ||
         a->is_named != b->is_named ||
         a->is_unnamed != b->is_unnamed ||
         a->is_valid != b->is_valid ||
         a->is_v2_dir != b->is_v2_dir ||
         a->is_possible_guard != b->is_possible_guard ||
         a->is_bad_exit != b->is_bad_exit ||
         a->is_bad_directory != b->is_bad_directory ||
         a->is_hs_dir != b->is_hs_dir ||
         a->version_known != b->version_known ||
         a->version_supports_begindir != b->version_supports_begindir ||
         a->version_supports_extrainfo_upload !=
           b->version_supports_extrainfo_upload ||
         a->version_supports_conditional_consensus !=
           b->version_supports_conditional_consensus ||
         a->version_supports_v3_dir != b->version_supports_v3_dir;
}

/** Notify controllers of any router status entries that changed between
 * <b>old_c</b> and <b>new_c</b>. */
static void
notify_control_networkstatus_changed(const networkstatus_t *old_c,
                                     const networkstatus_t *new_c)
{
  smartlist_t *changed;
  if (old_c == new_c)
    return;

  /* tell the controller exactly which relays are still listed, as well
   * as what they're listed as */
  control_event_newconsensus(new_c);

  if (!control_event_is_interesting(EVENT_NS))
    return;

  if (!old_c) {
    control_event_networkstatus_changed(new_c->routerstatus_list);
    return;
  }
  changed = smartlist_create();

  SMARTLIST_FOREACH_JOIN(old_c->routerstatus_list, routerstatus_t *, rs_old,
                         new_c->routerstatus_list, routerstatus_t *, rs_new,
                         memcmp(rs_old->identity_digest,
                                rs_new->identity_digest, DIGEST_LEN),
                         smartlist_add(changed, rs_new)) {
    if (routerstatus_has_changed(rs_old, rs_new))
      smartlist_add(changed, rs_new);
  } SMARTLIST_FOREACH_JOIN_END(rs_old, rs_new);

  control_event_networkstatus_changed(changed);
  smartlist_free(changed);
}

/** Copy all the ancillary information (like router download status and so on)
 * from <b>old_c</b> to <b>new_c</b>. */
static void
networkstatus_copy_old_consensus_info(networkstatus_t *new_c,
                                      const networkstatus_t *old_c)
{
  if (old_c == new_c)
    return;
  if (!old_c || !smartlist_len(old_c->routerstatus_list))
    return;

  SMARTLIST_FOREACH_JOIN(old_c->routerstatus_list, routerstatus_t *, rs_old,
                         new_c->routerstatus_list, routerstatus_t *, rs_new,
                         memcmp(rs_old->identity_digest,
                                rs_new->identity_digest, DIGEST_LEN),
                         STMT_NIL) {
    /* Okay, so we're looking at the same identity. */
    rs_new->name_lookup_warned = rs_old->name_lookup_warned;
    rs_new->last_dir_503_at = rs_old->last_dir_503_at;

    if (!memcmp(rs_old->descriptor_digest, rs_new->descriptor_digest,
                DIGEST_LEN)) {
      /* And the same descriptor too! */
      memcpy(&rs_new->dl_status, &rs_old->dl_status,sizeof(download_status_t));
    }
  } SMARTLIST_FOREACH_JOIN_END(rs_old, rs_new);
}

/** Try to replace the current cached v3 networkstatus with the one in
 * <b>consensus</b>.  If we don't have enough certificates to validate it,
 * store it in consensus_waiting_for_certs and launch a certificate fetch.
 *
 * If flags & NSSET_FROM_CACHE, this networkstatus has come from the disk
 * cache.  If flags & NSSET_WAS_WAITING_FOR_CERTS, this networkstatus was
 * already received, but we were waiting for certificates on it.  If flags &
 * NSSET_DONT_DOWNLOAD_CERTS, do not launch certificate downloads as needed.
 * If flags & NSSET_ACCEPT_OBSOLETE, then we should be willing to take this
 * consensus, even if it comes from many days in the past.
 *
 * Return 0 on success, <0 on failure.  On failure, caller should increment
 * the failure count as appropriate.
 *
 * We return -1 for mild failures that don't need to be reported to the
 * user, and -2 for more serious problems.
 */
int
networkstatus_set_current_consensus(const char *consensus, unsigned flags)
{
  networkstatus_t *c;
  int r, result = -1;
  time_t now = time(NULL);
  char *unverified_fname = NULL, *consensus_fname = NULL;
  const unsigned from_cache = flags & NSSET_FROM_CACHE;
  const unsigned was_waiting_for_certs = flags & NSSET_WAS_WAITING_FOR_CERTS;
  const unsigned dl_certs = !(flags & NSSET_DONT_DOWNLOAD_CERTS);
  const unsigned accept_obsolete = flags & NSSET_ACCEPT_OBSOLETE;

  /* Make sure it's parseable. */
  c = networkstatus_parse_vote_from_string(consensus, NULL, NS_TYPE_CONSENSUS);
  if (!c) {
    log_warn(LD_DIR, "Unable to parse networkstatus consensus");
    result = -2;
    goto done;
  }

  if (from_cache && !accept_obsolete &&
      c->valid_until < now-OLD_ROUTER_DESC_MAX_AGE) {
    /* XXX022 when we try to make fallbackconsensus work again, we should
     * consider taking this out. Until then, believing obsolete consensuses
     * is causing more harm than good. See also bug 887. */
    log_info(LD_DIR, "Loaded an obsolete consensus. Discarding.");
    goto done;
  }

  if (current_consensus &&
      !memcmp(c->networkstatus_digest, current_consensus->networkstatus_digest,
              DIGEST_LEN)) {
    /* We already have this one. That's a failure. */
    log_info(LD_DIR, "Got a consensus we already have");
    goto done;
  }

  if (current_consensus && c->valid_after <= current_consensus->valid_after) {
    /* We have a newer one.  There's no point in accepting this one,
     * even if it's great. */
    log_info(LD_DIR, "Got a consensus at least as old as the one we have");
    goto done;
  }

  consensus_fname = get_datadir_fname("cached-consensus");
  unverified_fname = get_datadir_fname("unverified-consensus");

  /* Make sure it's signed enough. */
  if ((r=networkstatus_check_consensus_signature(c, 1))<0) {
    if (r == -1) {
      /* Okay, so it _might_ be signed enough if we get more certificates. */
      if (!was_waiting_for_certs) {
        log_info(LD_DIR,
                 "Not enough certificates to check networkstatus consensus");
      }
      if (!current_consensus ||
          c->valid_after > current_consensus->valid_after) {
        if (consensus_waiting_for_certs)
          networkstatus_vote_free(consensus_waiting_for_certs);
        tor_free(consensus_waiting_for_certs_body);
        consensus_waiting_for_certs = c;
        c = NULL; /* Prevent free. */
        consensus_waiting_for_certs_body = tor_strdup(consensus);
        consensus_waiting_for_certs_set_at = now;
        consensus_waiting_for_certs_dl_failed = 0;
        if (!from_cache) {
          write_str_to_file(unverified_fname, consensus, 0);
        }
        if (dl_certs)
          authority_certs_fetch_missing(c, now);
        /* This case is not a success or a failure until we get the certs
         * or fail to get the certs. */
        result = 0;
      } else {
        /* Even if we had enough signatures, we'd never use this as the
         * latest consensus. */
        if (was_waiting_for_certs && from_cache)
          unlink(unverified_fname);
      }
      goto done;
    } else {
      /* This can never be signed enough:  Kill it. */
      if (!was_waiting_for_certs) {
        log_warn(LD_DIR, "Not enough good signatures on networkstatus "
                 "consensus");
        result = -2;
      }
      if (was_waiting_for_certs && (r < -1) && from_cache)
        unlink(unverified_fname);
      goto done;
    }
  }

  if (!from_cache)
    control_event_client_status(LOG_NOTICE, "CONSENSUS_ARRIVED");

  /* Are we missing any certificates at all? */
  if (r != 1 && dl_certs)
    authority_certs_fetch_missing(c, now);

  notify_control_networkstatus_changed(current_consensus, c);

  if (current_consensus) {
    networkstatus_copy_old_consensus_info(c, current_consensus);
    networkstatus_vote_free(current_consensus);
  }

  if (consensus_waiting_for_certs &&
      consensus_waiting_for_certs->valid_after <= c->valid_after) {
    networkstatus_vote_free(consensus_waiting_for_certs);
    consensus_waiting_for_certs = NULL;
    if (consensus != consensus_waiting_for_certs_body)
      tor_free(consensus_waiting_for_certs_body);
    else
      consensus_waiting_for_certs_body = NULL;
    consensus_waiting_for_certs_set_at = 0;
    consensus_waiting_for_certs_dl_failed = 0;
    unlink(unverified_fname);
  }

  /* Reset the failure count only if this consensus is actually valid. */
  if (c->valid_after <= now && now <= c->valid_until) {
    download_status_reset(&consensus_dl_status);
  } else {
    if (!from_cache)
      download_status_failed(&consensus_dl_status, 0);
  }

  current_consensus = c;
  c = NULL; /* Prevent free. */

  update_consensus_networkstatus_fetch_time(now);
  dirvote_recalculate_timing(get_options(), now);
  routerstatus_list_update_named_server_map();

  if (!from_cache) {
    write_str_to_file(consensus_fname, consensus, 0);
  }

  if (directory_caches_dir_info(get_options()))
    dirserv_set_cached_networkstatus_v3(consensus,
                                        current_consensus->valid_after);

  if (ftime_definitely_before(now, current_consensus->valid_after)) {
    char tbuf[ISO_TIME_LEN+1];
    char dbuf[64];
    long delta = now - current_consensus->valid_after;
    format_iso_time(tbuf, current_consensus->valid_after);
    format_time_interval(dbuf, sizeof(dbuf), delta);
    log_warn(LD_GENERAL, "Our clock is %s behind the time published in the "
             "consensus network status document (%s GMT).  Tor needs an "
             "accurate clock to work correctly. Please check your time and "
             "date settings!", dbuf, tbuf);
    control_event_general_status(LOG_WARN,
                    "CLOCK_SKEW MIN_SKEW=%ld SOURCE=CONSENSUS", delta);
  }

  router_dir_info_changed();

  result = 0;
 done:
  if (c)
    networkstatus_vote_free(c);
  tor_free(consensus_fname);
  tor_free(unverified_fname);
  return result;
}

/** Called when we have gotten more certificates: see whether we can
 * now verify a pending consensus. */
void
networkstatus_note_certs_arrived(void)
{
  if (consensus_waiting_for_certs) {
    if (networkstatus_check_consensus_signature(
                                    consensus_waiting_for_certs, 0)>=0) {
      if (!networkstatus_set_current_consensus(
                                 consensus_waiting_for_certs_body,
                                 NSSET_WAS_WAITING_FOR_CERTS)) {
        tor_free(consensus_waiting_for_certs_body);
      }
    }
  }
}

/** If the network-status list has changed since the last time we called this
 * function, update the status of every routerinfo from the network-status
 * list. If <b>dir_version</b> is 2, it's a v2 networkstatus that changed.
 * If <b>dir_version</b> is 3, it's a v3 consensus that changed.
 */
void
routers_update_all_from_networkstatus(time_t now, int dir_version)
{
  routerlist_t *rl = router_get_routerlist();
  networkstatus_t *consensus = networkstatus_get_live_consensus(now);

  if (networkstatus_v2_list_has_changed)
    download_status_map_update_from_v2_networkstatus();

  if (!consensus || dir_version < 3) /* nothing more we should do */
    return;

  /* calls router_dir_info_changed() when it's done -- more routers
   * might be up or down now, which might affect whether there's enough
   * directory info. */
  routers_update_status_from_consensus_networkstatus(rl->routers, 0);

  SMARTLIST_FOREACH(rl->routers, routerinfo_t *, ri,
                    ri->cache_info.routerlist_index = ri_sl_idx);
  if (rl->old_routers)
    signed_descs_update_status_from_consensus_networkstatus(rl->old_routers);

  if (!have_warned_about_old_version) {
    int is_server = server_mode(get_options());
    version_status_t status;
    const char *recommended = is_server ?
      consensus->server_versions : consensus->client_versions;
    status = tor_version_is_obsolete(VERSION, recommended);

    if (status == VS_RECOMMENDED) {
      log_info(LD_GENERAL, "The directory authorities say my version is ok.");
    } else if (status == VS_EMPTY) {
      log_info(LD_GENERAL,
               "The directory authorities don't recommend any versions.");
    } else if (status == VS_NEW || status == VS_NEW_IN_SERIES) {
      if (!have_warned_about_new_version) {
        log_notice(LD_GENERAL, "This version of Tor (%s) is newer than any "
                   "recommended version%s, according to the directory "
                   "authorities. Recommended versions are: %s",
                   VERSION,
                   status == VS_NEW_IN_SERIES ? " in its series" : "",
                   recommended);
        have_warned_about_new_version = 1;
        control_event_general_status(LOG_WARN, "DANGEROUS_VERSION "
                                     "CURRENT=%s REASON=%s RECOMMENDED=\"%s\"",
                                     VERSION, "NEW", recommended);
      }
    } else {
      log_warn(LD_GENERAL, "Please upgrade! "
               "This version of Tor (%s) is %s, according to the directory "
               "authorities. Recommended versions are: %s",
               VERSION,
               status == VS_OLD ? "obsolete" : "not recommended",
               recommended);
      have_warned_about_old_version = 1;
      control_event_general_status(LOG_WARN, "DANGEROUS_VERSION "
           "CURRENT=%s REASON=%s RECOMMENDED=\"%s\"",
           VERSION, status == VS_OLD ? "OBSOLETE" : "UNRECOMMENDED",
           recommended);
    }
  }
}

/** Update v2_download_status_map to contain an entry for every router
 * descriptor listed in the v2 networkstatuses. */
static void
download_status_map_update_from_v2_networkstatus(void)
{
  digestmap_t *dl_status;
  if (!networkstatus_v2_list)
    return;
  if (!v2_download_status_map)
    v2_download_status_map = digestmap_new();

  dl_status = digestmap_new();
  SMARTLIST_FOREACH(networkstatus_v2_list, networkstatus_v2_t *, ns,
  {
    SMARTLIST_FOREACH(ns->entries, routerstatus_t *, rs,
    {
      const char *d = rs->descriptor_digest;
      download_status_t *s;
      if (digestmap_get(dl_status, d))
        continue;
      if (!(s = digestmap_remove(v2_download_status_map, d))) {
        s = tor_malloc_zero(sizeof(download_status_t));
      }
      digestmap_set(dl_status, d, s);
    });
  });
  digestmap_free(v2_download_status_map, _tor_free);
  v2_download_status_map = dl_status;
  networkstatus_v2_list_has_changed = 0;
}

/** Update our view of the list of named servers from the most recently
 * retrieved networkstatus consensus. */
static void
routerstatus_list_update_named_server_map(void)
{
  if (!current_consensus)
    return;

  if (named_server_map)
    strmap_free(named_server_map, _tor_free);
  named_server_map = strmap_new();
  if (unnamed_server_map)
    strmap_free(unnamed_server_map, NULL);
  unnamed_server_map = strmap_new();
  SMARTLIST_FOREACH(current_consensus->routerstatus_list, routerstatus_t *, rs,
    {
      if (rs->is_named) {
        strmap_set_lc(named_server_map, rs->nickname,
                      tor_memdup(rs->identity_digest, DIGEST_LEN));
      }
      if (rs->is_unnamed) {
        strmap_set_lc(unnamed_server_map, rs->nickname, (void*)1);
      }
    });
}

/** Given a list <b>routers</b> of routerinfo_t *, update each status field
 * according to our current consensus networkstatus.  May re-order
 * <b>routers</b>. */
void
routers_update_status_from_consensus_networkstatus(smartlist_t *routers,
                                                   int reset_failures)
{
  trusted_dir_server_t *ds;
  or_options_t *options = get_options();
  int authdir = authdir_mode_v2(options) || authdir_mode_v3(options);
  int namingdir = authdir && options->NamingAuthoritativeDir;
  networkstatus_t *ns = current_consensus;
  if (!ns || !smartlist_len(ns->routerstatus_list))
    return;
  if (!networkstatus_v2_list)
    networkstatus_v2_list = smartlist_create();

  routers_sort_by_identity(routers);

  SMARTLIST_FOREACH_JOIN(ns->routerstatus_list, routerstatus_t *, rs,
                         routers, routerinfo_t *, router,
                         memcmp(rs->identity_digest,
                               router->cache_info.identity_digest, DIGEST_LEN),
  {
    /* We have no routerstatus for this router. Clear flags and skip it. */
    if (!namingdir)
      router->is_named = 0;
    if (!authdir) {
      if (router->purpose == ROUTER_PURPOSE_GENERAL)
        router_clear_status_flags(router);
    }
  }) {
    /* We have a routerstatus for this router. */
    const char *digest = router->cache_info.identity_digest;

    ds = router_get_trusteddirserver_by_digest(digest);

    if (!namingdir) {
      if (rs->is_named && !strcasecmp(router->nickname, rs->nickname))
        router->is_named = 1;
      else
        router->is_named = 0;
    }
    /* Is it the same descriptor, or only the same identity? */
    if (!memcmp(router->cache_info.signed_descriptor_digest,
                rs->descriptor_digest, DIGEST_LEN)) {
      if (ns->valid_until > router->cache_info.last_listed_as_valid_until)
        router->cache_info.last_listed_as_valid_until = ns->valid_until;
    }

    if (!authdir) {
      /* If we're not an authdir, believe others. */
      router->is_valid = rs->is_valid;
      router->is_running = rs->is_running;
      router->is_fast = rs->is_fast;
      router->is_stable = rs->is_stable;
      router->is_possible_guard = rs->is_possible_guard;
      router->is_exit = rs->is_exit;
      router->is_bad_directory = rs->is_bad_directory;
      router->is_bad_exit = rs->is_bad_exit;
      router->is_hs_dir = rs->is_hs_dir;
    }
    if (router->is_running && ds) {
      download_status_reset(&ds->v2_ns_dl_status);
    }
    if (reset_failures) {
      download_status_reset(&rs->dl_status);
    }
  } SMARTLIST_FOREACH_JOIN_END(rs, router);

  /* Now update last_listed_as_valid_until from v2 networkstatuses. */
  /* XXXX If this is slow, we need to rethink the code. */
  SMARTLIST_FOREACH(networkstatus_v2_list, networkstatus_v2_t *, ns, {
    time_t live_until = ns->published_on + V2_NETWORKSTATUS_ROUTER_LIFETIME;
    SMARTLIST_FOREACH_JOIN(ns->entries, routerstatus_t *, rs,
                         routers, routerinfo_t *, ri,
                         memcmp(rs->identity_digest,
                                ri->cache_info.identity_digest, DIGEST_LEN),
                         STMT_NIL) {
      if (!memcmp(ri->cache_info.signed_descriptor_digest,
                  rs->descriptor_digest, DIGEST_LEN)) {
        if (live_until > ri->cache_info.last_listed_as_valid_until)
          ri->cache_info.last_listed_as_valid_until = live_until;
      }
    } SMARTLIST_FOREACH_JOIN_END(rs, ri);
  });

  router_dir_info_changed();
}

/** Given a list of signed_descriptor_t, update their fields (mainly, when
 * they were last listed) from the most recent consensus. */
void
signed_descs_update_status_from_consensus_networkstatus(smartlist_t *descs)
{
  networkstatus_t *ns = current_consensus;
  if (!ns)
    return;

  if (!ns->desc_digest_map) {
    char dummy[DIGEST_LEN];
    /* instantiates the digest map. */
    memset(dummy, 0, sizeof(dummy));
    router_get_consensus_status_by_descriptor_digest(dummy);
  }
  SMARTLIST_FOREACH(descs, signed_descriptor_t *, d,
  {
    routerstatus_t *rs = digestmap_get(ns->desc_digest_map,
                                       d->signed_descriptor_digest);
    if (rs) {
      if (ns->valid_until > d->last_listed_as_valid_until)
        d->last_listed_as_valid_until = ns->valid_until;
    }
  });
}

/** Generate networkstatus lines for a single routerstatus_t object, and
 * return the result in a newly allocated string.  Used only by controller
 * interface (for now.) */
char *
networkstatus_getinfo_helper_single(routerstatus_t *rs)
{
  char buf[RS_ENTRY_LEN+1];
  routerstatus_format_entry(buf, sizeof(buf), rs, NULL, 0, 1);
  return tor_strdup(buf);
}

/** Alloc and return a string describing routerstatuses for the most
 * recent info of each router we know about that is of purpose
 * <b>purpose_string</b>. Return NULL if unrecognized purpose.
 *
 * Right now this function is oriented toward listing bridges (you
 * shouldn't use this for general-purpose routers, since those
 * should be listed from the consensus, not from the routers list). */
char *
networkstatus_getinfo_by_purpose(const char *purpose_string, time_t now)
{
  time_t cutoff = now - ROUTER_MAX_AGE_TO_PUBLISH;
  char *answer;
  routerlist_t *rl = router_get_routerlist();
  smartlist_t *statuses;
  uint8_t purpose = router_purpose_from_string(purpose_string);
  routerstatus_t rs;
  int bridge_auth = authdir_mode_bridge(get_options());

  if (purpose == ROUTER_PURPOSE_UNKNOWN) {
    log_info(LD_DIR, "Unrecognized purpose '%s' when listing router statuses.",
             purpose_string);
    return NULL;
  }

  statuses = smartlist_create();
  SMARTLIST_FOREACH(rl->routers, routerinfo_t *, ri, {
    if (ri->cache_info.published_on < cutoff)
      continue;
    if (ri->purpose != purpose)
      continue;
    if (bridge_auth && ri->purpose == ROUTER_PURPOSE_BRIDGE)
      dirserv_set_router_is_running(ri, now);
    /* then generate and write out status lines for each of them */
    set_routerstatus_from_routerinfo(&rs, ri, now, 0, 0, 0, 0);
    smartlist_add(statuses, networkstatus_getinfo_helper_single(&rs));
  });

  answer = smartlist_join_strings(statuses, "", 0, NULL);
  SMARTLIST_FOREACH(statuses, char *, cp, tor_free(cp));
  smartlist_free(statuses);
  return answer;
}

/** Write out router status entries for all our bridge descriptors. */
void
networkstatus_dump_bridge_status_to_file(time_t now)
{
  char *status = networkstatus_getinfo_by_purpose("bridge", now);
  or_options_t *options = get_options();
  size_t len = strlen(options->DataDirectory) + 32;
  char *fname = tor_malloc(len);
  tor_snprintf(fname, len, "%s"PATH_SEPARATOR"networkstatus-bridges",
               options->DataDirectory);
  write_str_to_file(fname,status,0);
  tor_free(fname);
  tor_free(status);
}

/** Return the value of a integer parameter from the networkstatus <b>ns</b>
 * whose name is <b>param_name</b>.  If <b>ns</b> is NULL, try loading the
 * latest consensus ourselves. Return <b>default_val</b> if no latest
 * consensus, or if it has no parameter called <b>param_name</b>. */
int32_t
networkstatus_get_param(networkstatus_t *ns, const char *param_name,
                        int32_t default_val)
{
  size_t name_len;

  if (!ns) /* if they pass in null, go find it ourselves */
    ns = networkstatus_get_latest_consensus();

  if (!ns || !ns->net_params)
    return default_val;

  name_len = strlen(param_name);

  SMARTLIST_FOREACH_BEGIN(ns->net_params, const char *, p) {
    if (!strcmpstart(p, param_name) && p[name_len] == '=') {
      int ok=0;
      long v = tor_parse_long(p+name_len+1, 10, INT32_MIN, INT32_MAX, &ok,
                              NULL);
      if (ok)
        return (int32_t) v;
    }
  } SMARTLIST_FOREACH_END(p);

  return default_val;
}

/** If <b>question</b> is a string beginning with "ns/" in a format the
 * control interface expects for a GETINFO question, set *<b>answer</b> to a
 * newly-allocated string containing networkstatus lines for the appropriate
 * ORs.  Return 0 on success, -1 on unrecognized question format. */
int
getinfo_helper_networkstatus(control_connection_t *conn,
                             const char *question, char **answer)
{
  routerstatus_t *status;
  (void) conn;

  if (!current_consensus) {
    *answer = tor_strdup("");
    return 0;
  }

  if (!strcmp(question, "ns/all")) {
    smartlist_t *statuses = smartlist_create();
    SMARTLIST_FOREACH(current_consensus->routerstatus_list,
                      routerstatus_t *, rs,
      {
        smartlist_add(statuses, networkstatus_getinfo_helper_single(rs));
      });
    *answer = smartlist_join_strings(statuses, "", 0, NULL);
    SMARTLIST_FOREACH(statuses, char *, cp, tor_free(cp));
    smartlist_free(statuses);
    return 0;
  } else if (!strcmpstart(question, "ns/id/")) {
    char d[DIGEST_LEN];

    if (base16_decode(d, DIGEST_LEN, question+6, strlen(question+6)))
      return -1;
    status = router_get_consensus_status_by_id(d);
  } else if (!strcmpstart(question, "ns/name/")) {
    status = router_get_consensus_status_by_nickname(question+8, 0);
  } else if (!strcmpstart(question, "ns/purpose/")) {
    *answer = networkstatus_getinfo_by_purpose(question+11, time(NULL));
    return *answer ? 0 : -1;
  } else {
    return -1;
  }

  if (status)
    *answer = networkstatus_getinfo_helper_single(status);
  return 0;
}

/** Free all storage held locally in this module. */
void
networkstatus_free_all(void)
{
  if (networkstatus_v2_list) {
    SMARTLIST_FOREACH(networkstatus_v2_list, networkstatus_v2_t *, ns,
                      networkstatus_v2_free(ns));
    smartlist_free(networkstatus_v2_list);
    networkstatus_v2_list = NULL;
  }
  if (v2_download_status_map) {
    digestmap_free(v2_download_status_map, _tor_free);
    v2_download_status_map = NULL;
  }
  if (current_consensus) {
    networkstatus_vote_free(current_consensus);
    current_consensus = NULL;
  }
  if (consensus_waiting_for_certs) {
    networkstatus_vote_free(consensus_waiting_for_certs);
    consensus_waiting_for_certs = NULL;
  }
  tor_free(consensus_waiting_for_certs_body);
  if (named_server_map) {
    strmap_free(named_server_map, _tor_free);
  }
  if (unnamed_server_map) {
    strmap_free(unnamed_server_map, NULL);
  }
}