Split routerlist.c into 4 separate modules

There are now separate modules for:
    * the list of router descriptors
    * the list of authorities and fallbacks
    * managing authority certificates
    * selecting random nodes

1 files changed, 1108 insertions, 0 deletions

diff --git a/src/feature/nodelist/node_select.c b/src/feature/nodelist/node_select.c
new file mode 100644
index 0000000000..a9f045d456
--- /dev/null
+++ b/src/feature/nodelist/node_select.c
@@ -0,0 +1,1108 @@
+/* Copyright (c) 2001 Matej Pfajfar.
+ * Copyright (c) 2001-2004, Roger Dingledine.
+ * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
+ * Copyright (c) 2007-2018, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file node_select.c
+ * \brief Code to choose nodes randomly based on restrictions and
+ *   weighted probabilities.
+ **/
+
+#define NODE_SELECT_PRIVATE
+#include "core/or/or.h"
+
+#include "app/config/config.h"
+#include "core/mainloop/connection.h"
+#include "core/or/policies.h"
+#include "core/or/reasons.h"
+#include "feature/client/entrynodes.h"
+#include "feature/dircache/directory.h"
+#include "feature/nodelist/dirlist.h"
+#include "feature/nodelist/microdesc.h"
+#include "feature/nodelist/networkstatus.h"
+#include "feature/nodelist/node_select.h"
+#include "feature/nodelist/nodelist.h"
+#include "feature/nodelist/routerlist.h"
+#include "feature/nodelist/routerset.h"
+#include "feature/relay/router.h"
+#include "lib/crypt_ops/crypto_rand.h"
+#include "lib/math/fp.h"
+
+#include "feature/dirclient/dir_server_st.h"
+#include "feature/nodelist/networkstatus_st.h"
+#include "feature/nodelist/node_st.h"
+#include "feature/nodelist/routerinfo_st.h"
+#include "feature/nodelist/routerstatus_st.h"
+
+static int compute_weighted_bandwidths(const smartlist_t *sl,
+                                       bandwidth_weight_rule_t rule,
+                                       double **bandwidths_out,
+                                       double *total_bandwidth_out);
+static const routerstatus_t *router_pick_trusteddirserver_impl(
+                const smartlist_t *sourcelist, dirinfo_type_t auth,
+                int flags, int *n_busy_out);
+static const routerstatus_t *router_pick_dirserver_generic(
+                              smartlist_t *sourcelist,
+                              dirinfo_type_t type, int flags);
+
+/** Try to find a running dirserver that supports operations of <b>type</b>.
+ *
+ * If there are no running dirservers in our routerlist and the
+ * <b>PDS_RETRY_IF_NO_SERVERS</b> flag is set, set all the fallback ones
+ * (including authorities) as running again, and pick one.
+ *
+ * If the <b>PDS_IGNORE_FASCISTFIREWALL</b> flag is set, then include
+ * dirservers that we can't reach.
+ *
+ * If the <b>PDS_ALLOW_SELF</b> flag is not set, then don't include ourself
+ * (if we're a dirserver).
+ *
+ * Don't pick a fallback directory mirror if any non-fallback is viable;
+ * (the fallback directory mirrors include the authorities)
+ * try to avoid using servers that have returned 503 recently.
+ */
+const routerstatus_t *
+router_pick_directory_server(dirinfo_type_t type, int flags)
+{
+  int busy = 0;
+  const routerstatus_t *choice;
+
+  choice = router_pick_directory_server_impl(type, flags, &busy);
+  if (choice || !(flags & PDS_RETRY_IF_NO_SERVERS))
+    return choice;
+
+  if (busy) {
+    /* If the reason that we got no server is that servers are "busy",
+     * we must be excluding good servers because we already have serverdesc
+     * fetches with them.  Do not mark down servers up because of this. */
+    tor_assert((flags & (PDS_NO_EXISTING_SERVERDESC_FETCH|
+                         PDS_NO_EXISTING_MICRODESC_FETCH)));
+    return NULL;
+  }
+
+  log_info(LD_DIR,
+           "No reachable router entries for dirservers. "
+           "Trying them all again.");
+  /* mark all fallback directory mirrors as up again */
+  router_reset_status_download_failures();
+  /* try again */
+  choice = router_pick_directory_server_impl(type, flags, NULL);
+  return choice;
+}
+
+/** Try to find a running fallback directory. Flags are as for
+ * router_pick_directory_server.
+ */
+const routerstatus_t *
+router_pick_dirserver_generic(smartlist_t *sourcelist,
+                              dirinfo_type_t type, int flags)
+{
+  const routerstatus_t *choice;
+  int busy = 0;
+
+  if (smartlist_len(sourcelist) == 1) {
+    /* If there's only one choice, then we should disable the logic that
+     * would otherwise prevent us from choosing ourself. */
+    flags |= PDS_ALLOW_SELF;
+  }
+
+  choice = router_pick_trusteddirserver_impl(sourcelist, type, flags, &busy);
+  if (choice || !(flags & PDS_RETRY_IF_NO_SERVERS))
+    return choice;
+  if (busy) {
+    /* If the reason that we got no server is that servers are "busy",
+     * we must be excluding good servers because we already have serverdesc
+     * fetches with them.  Do not mark down servers up because of this. */
+    tor_assert((flags & (PDS_NO_EXISTING_SERVERDESC_FETCH|
+                         PDS_NO_EXISTING_MICRODESC_FETCH)));
+    return NULL;
+  }
+
+  log_info(LD_DIR,
+           "No dirservers are reachable. Trying them all again.");
+  mark_all_dirservers_up(sourcelist);
+  return router_pick_trusteddirserver_impl(sourcelist, type, flags, NULL);
+}
+
+/* Common retry code for router_pick_directory_server_impl and
+ * router_pick_trusteddirserver_impl. Retry with the non-preferred IP version.
+ * Must be called before RETRY_WITHOUT_EXCLUDE().
+ *
+ * If we got no result, and we are applying IP preferences, and we are a
+ * client that could use an alternate IP version, try again with the
+ * opposite preferences. */
+#define RETRY_ALTERNATE_IP_VERSION(retry_label)                               \
+  STMT_BEGIN                                                                  \
+    if (result == NULL && try_ip_pref && options->ClientUseIPv4               \
+        && fascist_firewall_use_ipv6(options) && !server_mode(options)        \
+        && !n_busy) {                                                         \
+      n_excluded = 0;                                                         \
+      n_busy = 0;                                                             \
+      try_ip_pref = 0;                                                        \
+      goto retry_label;                                                       \
+    }                                                                         \
+  STMT_END                                                                    \
+
+/* Common retry code for router_pick_directory_server_impl and
+ * router_pick_trusteddirserver_impl. Retry without excluding nodes, but with
+ * the preferred IP version. Must be called after RETRY_ALTERNATE_IP_VERSION().
+ *
+ * If we got no result, and we are excluding nodes, and StrictNodes is
+ * not set, try again without excluding nodes. */
+#define RETRY_WITHOUT_EXCLUDE(retry_label)                                    \
+  STMT_BEGIN                                                                  \
+    if (result == NULL && try_excluding && !options->StrictNodes              \
+        && n_excluded && !n_busy) {                                           \
+      try_excluding = 0;                                                      \
+      n_excluded = 0;                                                         \
+      n_busy = 0;                                                             \
+      try_ip_pref = 1;                                                        \
+      goto retry_label;                                                       \
+    }                                                                         \
+  STMT_END
+
+/* Common code used in the loop within router_pick_directory_server_impl and
+ * router_pick_trusteddirserver_impl.
+ *
+ * Check if the given <b>identity</b> supports extrainfo. If not, skip further
+ * checks.
+ */
+#define SKIP_MISSING_TRUSTED_EXTRAINFO(type, identity)                        \
+  STMT_BEGIN                                                                  \
+    int is_trusted_extrainfo = router_digest_is_trusted_dir_type(             \
+                               (identity), EXTRAINFO_DIRINFO);                \
+    if (((type) & EXTRAINFO_DIRINFO) &&                                       \
+        !router_supports_extrainfo((identity), is_trusted_extrainfo))         \
+      continue;                                                               \
+  STMT_END
+
+#ifndef LOG_FALSE_POSITIVES_DURING_BOOTSTRAP
+#define LOG_FALSE_POSITIVES_DURING_BOOTSTRAP 0
+#endif
+
+/* Log a message if rs is not found or not a preferred address */
+static void
+router_picked_poor_directory_log(const routerstatus_t *rs)
+{
+  const networkstatus_t *usable_consensus;
+  usable_consensus = networkstatus_get_reasonably_live_consensus(time(NULL),
+                                                 usable_consensus_flavor());
+
+#if !LOG_FALSE_POSITIVES_DURING_BOOTSTRAP
+  /* Don't log early in the bootstrap process, it's normal to pick from a
+   * small pool of nodes. Of course, this won't help if we're trying to
+   * diagnose bootstrap issues. */
+  if (!smartlist_len(nodelist_get_list()) || !usable_consensus
+      || !router_have_minimum_dir_info()) {
+    return;
+  }
+#endif /* !LOG_FALSE_POSITIVES_DURING_BOOTSTRAP */
+
+  /* We couldn't find a node, or the one we have doesn't fit our preferences.
+   * Sometimes this is normal, sometimes it can be a reachability issue. */
+  if (!rs) {
+    /* This happens a lot, so it's at debug level */
+    log_debug(LD_DIR, "Wanted to make an outgoing directory connection, but "
+              "we couldn't find a directory that fit our criteria. "
+              "Perhaps we will succeed next time with less strict criteria.");
+  } else if (!fascist_firewall_allows_rs(rs, FIREWALL_OR_CONNECTION, 1)
+             && !fascist_firewall_allows_rs(rs, FIREWALL_DIR_CONNECTION, 1)
+             ) {
+    /* This is rare, and might be interesting to users trying to diagnose
+     * connection issues on dual-stack machines. */
+    log_info(LD_DIR, "Selected a directory %s with non-preferred OR and Dir "
+             "addresses for launching an outgoing connection: "
+             "IPv4 %s OR %d Dir %d IPv6 %s OR %d Dir %d",
+             routerstatus_describe(rs),
+             fmt_addr32(rs->addr), rs->or_port,
+             rs->dir_port, fmt_addr(&rs->ipv6_addr),
+             rs->ipv6_orport, rs->dir_port);
+  }
+}
+
+#undef LOG_FALSE_POSITIVES_DURING_BOOTSTRAP
+
+/* Check if we already have a directory fetch from ap, for serverdesc
+ * (including extrainfo) or microdesc documents.
+ * If so, return 1, if not, return 0.
+ * Also returns 0 if addr is NULL, tor_addr_is_null(addr), or dir_port is 0.
+ */
+STATIC int
+router_is_already_dir_fetching(const tor_addr_port_t *ap, int serverdesc,
+                               int microdesc)
+{
+  if (!ap || tor_addr_is_null(&ap->addr) || !ap->port) {
+    return 0;
+  }
+
+  /* XX/teor - we're not checking tunnel connections here, see #17848
+   */
+  if (serverdesc && (
+     connection_get_by_type_addr_port_purpose(
+       CONN_TYPE_DIR, &ap->addr, ap->port, DIR_PURPOSE_FETCH_SERVERDESC)
+  || connection_get_by_type_addr_port_purpose(
+       CONN_TYPE_DIR, &ap->addr, ap->port, DIR_PURPOSE_FETCH_EXTRAINFO))) {
+    return 1;
+  }
+
+  if (microdesc && (
+     connection_get_by_type_addr_port_purpose(
+       CONN_TYPE_DIR, &ap->addr, ap->port, DIR_PURPOSE_FETCH_MICRODESC))) {
+    return 1;
+  }
+
+  return 0;
+}
+
+/* Check if we already have a directory fetch from the ipv4 or ipv6
+ * router, for serverdesc (including extrainfo) or microdesc documents.
+ * If so, return 1, if not, return 0.
+ */
+static int
+router_is_already_dir_fetching_(uint32_t ipv4_addr,
+                                const tor_addr_t *ipv6_addr,
+                                uint16_t dir_port,
+                                int serverdesc,
+                                int microdesc)
+{
+  tor_addr_port_t ipv4_dir_ap, ipv6_dir_ap;
+
+  /* Assume IPv6 DirPort is the same as IPv4 DirPort */
+  tor_addr_from_ipv4h(&ipv4_dir_ap.addr, ipv4_addr);
+  ipv4_dir_ap.port = dir_port;
+  tor_addr_copy(&ipv6_dir_ap.addr, ipv6_addr);
+  ipv6_dir_ap.port = dir_port;
+
+  return (router_is_already_dir_fetching(&ipv4_dir_ap, serverdesc, microdesc)
+       || router_is_already_dir_fetching(&ipv6_dir_ap, serverdesc, microdesc));
+}
+
+/** Pick a random running valid directory server/mirror from our
+ * routerlist.  Arguments are as for router_pick_directory_server(), except:
+ *
+ * If <b>n_busy_out</b> is provided, set *<b>n_busy_out</b> to the number of
+ * directories that we excluded for no other reason than
+ * PDS_NO_EXISTING_SERVERDESC_FETCH or PDS_NO_EXISTING_MICRODESC_FETCH.
+ */
+STATIC const routerstatus_t *
+router_pick_directory_server_impl(dirinfo_type_t type, int flags,
+                                  int *n_busy_out)
+{
+  const or_options_t *options = get_options();
+  const node_t *result;
+  smartlist_t *direct, *tunnel;
+  smartlist_t *trusted_direct, *trusted_tunnel;
+  smartlist_t *overloaded_direct, *overloaded_tunnel;
+  time_t now = time(NULL);
+  const networkstatus_t *consensus = networkstatus_get_latest_consensus();
+  const int requireother = ! (flags & PDS_ALLOW_SELF);
+  const int fascistfirewall = ! (flags & PDS_IGNORE_FASCISTFIREWALL);
+  const int no_serverdesc_fetching =(flags & PDS_NO_EXISTING_SERVERDESC_FETCH);
+  const int no_microdesc_fetching = (flags & PDS_NO_EXISTING_MICRODESC_FETCH);
+  int try_excluding = 1, n_excluded = 0, n_busy = 0;
+  int try_ip_pref = 1;
+
+  if (!consensus)
+    return NULL;
+
+ retry_search:
+
+  direct = smartlist_new();
+  tunnel = smartlist_new();
+  trusted_direct = smartlist_new();
+  trusted_tunnel = smartlist_new();
+  overloaded_direct = smartlist_new();
+  overloaded_tunnel = smartlist_new();
+
+  const int skip_or_fw = router_skip_or_reachability(options, try_ip_pref);
+  const int skip_dir_fw = router_skip_dir_reachability(options, try_ip_pref);
+  const int must_have_or = directory_must_use_begindir(options);
+
+  /* Find all the running dirservers we know about. */
+  SMARTLIST_FOREACH_BEGIN(nodelist_get_list(), const node_t *, node) {
+    int is_trusted;
+    int is_overloaded;
+    const routerstatus_t *status = node->rs;
+    const country_t country = node->country;
+    if (!status)
+      continue;
+
+    if (!node->is_running || !node_is_dir(node) || !node->is_valid)
+      continue;
+    if (requireother && router_digest_is_me(node->identity))
+      continue;
+
+    SKIP_MISSING_TRUSTED_EXTRAINFO(type, node->identity);
+
+    if (try_excluding &&
+        routerset_contains_routerstatus(options->ExcludeNodes, status,
+                                        country)) {
+      ++n_excluded;
+      continue;
+    }
+
+    if (router_is_already_dir_fetching_(status->addr,
+                                        &status->ipv6_addr,
+                                        status->dir_port,
+                                        no_serverdesc_fetching,
+                                        no_microdesc_fetching)) {
+      ++n_busy;
+      continue;
+    }
+
+    is_overloaded = status->last_dir_503_at + DIR_503_TIMEOUT > now;
+    is_trusted = router_digest_is_trusted_dir(node->identity);
+
+    /* Clients use IPv6 addresses if the server has one and the client
+     * prefers IPv6.
+     * Add the router if its preferred address and port are reachable.
+     * If we don't get any routers, we'll try again with the non-preferred
+     * address for each router (if any). (To ensure correct load-balancing
+     * we try routers that only have one address both times.)
+     */
+    if (!fascistfirewall || skip_or_fw ||
+        fascist_firewall_allows_node(node, FIREWALL_OR_CONNECTION,
+                                     try_ip_pref))
+      smartlist_add(is_trusted ? trusted_tunnel :
+                    is_overloaded ? overloaded_tunnel : tunnel, (void*)node);
+    else if (!must_have_or && (skip_dir_fw ||
+             fascist_firewall_allows_node(node, FIREWALL_DIR_CONNECTION,
+                                          try_ip_pref)))
+      smartlist_add(is_trusted ? trusted_direct :
+                    is_overloaded ? overloaded_direct : direct, (void*)node);
+  } SMARTLIST_FOREACH_END(node);
+
+  if (smartlist_len(tunnel)) {
+    result = node_sl_choose_by_bandwidth(tunnel, WEIGHT_FOR_DIR);
+  } else if (smartlist_len(overloaded_tunnel)) {
+    result = node_sl_choose_by_bandwidth(overloaded_tunnel,
+                                                 WEIGHT_FOR_DIR);
+  } else if (smartlist_len(trusted_tunnel)) {
+    /* FFFF We don't distinguish between trusteds and overloaded trusteds
+     * yet. Maybe one day we should. */
+    /* FFFF We also don't load balance over authorities yet. I think this
+     * is a feature, but it could easily be a bug. -RD */
+    result = smartlist_choose(trusted_tunnel);
+  } else if (smartlist_len(direct)) {
+    result = node_sl_choose_by_bandwidth(direct, WEIGHT_FOR_DIR);
+  } else if (smartlist_len(overloaded_direct)) {
+    result = node_sl_choose_by_bandwidth(overloaded_direct,
+                                         WEIGHT_FOR_DIR);
+  } else {
+    result = smartlist_choose(trusted_direct);
+  }
+  smartlist_free(direct);
+  smartlist_free(tunnel);
+  smartlist_free(trusted_direct);
+  smartlist_free(trusted_tunnel);
+  smartlist_free(overloaded_direct);
+  smartlist_free(overloaded_tunnel);
+
+  RETRY_ALTERNATE_IP_VERSION(retry_search);
+
+  RETRY_WITHOUT_EXCLUDE(retry_search);
+
+  if (n_busy_out)
+    *n_busy_out = n_busy;
+
+  router_picked_poor_directory_log(result ? result->rs : NULL);
+
+  return result ? result->rs : NULL;
+}
+
+/** Given an array of double/uint64_t unions that are currently being used as
+ * doubles, convert them to uint64_t, and try to scale them linearly so as to
+ * much of the range of uint64_t. If <b>total_out</b> is provided, set it to
+ * the sum of all elements in the array _before_ scaling. */
+STATIC void
+scale_array_elements_to_u64(uint64_t *entries_out, const double *entries_in,
+                            int n_entries,
+                            uint64_t *total_out)
+{
+  double total = 0.0;
+  double scale_factor = 0.0;
+  int i;
+
+  for (i = 0; i < n_entries; ++i)
+    total += entries_in[i];
+
+  if (total > 0.0) {
+    scale_factor = ((double)INT64_MAX) / total;
+    scale_factor /= 4.0; /* make sure we're very far away from overflowing */
+  }
+
+  for (i = 0; i < n_entries; ++i)
+    entries_out[i] = tor_llround(entries_in[i] * scale_factor);
+
+  if (total_out)
+    *total_out = (uint64_t) total;
+}
+
+/** Pick a random element of <b>n_entries</b>-element array <b>entries</b>,
+ * choosing each element with a probability proportional to its (uint64_t)
+ * value, and return the index of that element.  If all elements are 0, choose
+ * an index at random. Return -1 on error.
+ */
+STATIC int
+choose_array_element_by_weight(const uint64_t *entries, int n_entries)
+{
+  int i;
+  uint64_t rand_val;
+  uint64_t total = 0;
+
+  for (i = 0; i < n_entries; ++i)
+    total += entries[i];
+
+  if (n_entries < 1)
+    return -1;
+
+  if (total == 0)
+    return crypto_rand_int(n_entries);
+
+  tor_assert(total < INT64_MAX);
+
+  rand_val = crypto_rand_uint64(total);
+
+  return select_array_member_cumulative_timei(
+                           entries, n_entries, total, rand_val);
+}
+
+/** Return bw*1000, unless bw*1000 would overflow, in which case return
+ * INT32_MAX. */
+static inline int32_t
+kb_to_bytes(uint32_t bw)
+{
+  return (bw > (INT32_MAX/1000)) ? INT32_MAX : bw*1000;
+}
+
+/** Helper function:
+ * choose a random element of smartlist <b>sl</b> of nodes, weighted by
+ * the advertised bandwidth of each element using the consensus
+ * bandwidth weights.
+ *
+ * If <b>rule</b>==WEIGHT_FOR_EXIT. we're picking an exit node: consider all
+ * nodes' bandwidth equally regardless of their Exit status, since there may
+ * be some in the list because they exit to obscure ports. If
+ * <b>rule</b>==NO_WEIGHTING, we're picking a non-exit node: weight
+ * exit-node's bandwidth less depending on the smallness of the fraction of
+ * Exit-to-total bandwidth.  If <b>rule</b>==WEIGHT_FOR_GUARD, we're picking a
+ * guard node: consider all guard's bandwidth equally. Otherwise, weight
+ * guards proportionally less.
+ */
+static const node_t *
+smartlist_choose_node_by_bandwidth_weights(const smartlist_t *sl,
+                                           bandwidth_weight_rule_t rule)
+{
+  double *bandwidths_dbl=NULL;
+  uint64_t *bandwidths_u64=NULL;
+
+  if (compute_weighted_bandwidths(sl, rule, &bandwidths_dbl, NULL) < 0)
+    return NULL;
+
+  bandwidths_u64 = tor_calloc(smartlist_len(sl), sizeof(uint64_t));
+  scale_array_elements_to_u64(bandwidths_u64, bandwidths_dbl,
+                              smartlist_len(sl), NULL);
+
+  {
+    int idx = choose_array_element_by_weight(bandwidths_u64,
+                                             smartlist_len(sl));
+    tor_free(bandwidths_dbl);
+    tor_free(bandwidths_u64);
+    return idx < 0 ? NULL : smartlist_get(sl, idx);
+  }
+}
+
+/** When weighting bridges, enforce these values as lower and upper
+ * bound for believable bandwidth, because there is no way for us
+ * to verify a bridge's bandwidth currently. */
+#define BRIDGE_MIN_BELIEVABLE_BANDWIDTH 20000  /* 20 kB/sec */
+#define BRIDGE_MAX_BELIEVABLE_BANDWIDTH 100000 /* 100 kB/sec */
+
+/** Return the smaller of the router's configured BandwidthRate
+ * and its advertised capacity, making sure to stay within the
+ * interval between bridge-min-believe-bw and
+ * bridge-max-believe-bw. */
+static uint32_t
+bridge_get_advertised_bandwidth_bounded(routerinfo_t *router)
+{
+  uint32_t result = router->bandwidthcapacity;
+  if (result > router->bandwidthrate)
+    result = router->bandwidthrate;
+  if (result > BRIDGE_MAX_BELIEVABLE_BANDWIDTH)
+    result = BRIDGE_MAX_BELIEVABLE_BANDWIDTH;
+  else if (result < BRIDGE_MIN_BELIEVABLE_BANDWIDTH)
+    result = BRIDGE_MIN_BELIEVABLE_BANDWIDTH;
+  return result;
+}
+
+/** Given a list of routers and a weighting rule as in
+ * smartlist_choose_node_by_bandwidth_weights, compute weighted bandwidth
+ * values for each node and store them in a freshly allocated
+ * *<b>bandwidths_out</b> of the same length as <b>sl</b>, and holding results
+ * as doubles. If <b>total_bandwidth_out</b> is non-NULL, set it to the total
+ * of all the bandwidths.
+ * Return 0 on success, -1 on failure. */
+static int
+compute_weighted_bandwidths(const smartlist_t *sl,
+                            bandwidth_weight_rule_t rule,
+                            double **bandwidths_out,
+                            double *total_bandwidth_out)
+{
+  int64_t weight_scale;
+  double Wg = -1, Wm = -1, We = -1, Wd = -1;
+  double Wgb = -1, Wmb = -1, Web = -1, Wdb = -1;
+  guardfraction_bandwidth_t guardfraction_bw;
+  double *bandwidths = NULL;
+  double total_bandwidth = 0.0;
+
+  tor_assert(sl);
+  tor_assert(bandwidths_out);
+
+  /* Can't choose exit and guard at same time */
+  tor_assert(rule == NO_WEIGHTING ||
+             rule == WEIGHT_FOR_EXIT ||
+             rule == WEIGHT_FOR_GUARD ||
+             rule == WEIGHT_FOR_MID ||
+             rule == WEIGHT_FOR_DIR);
+
+  *bandwidths_out = NULL;
+
+  if (total_bandwidth_out) {
+    *total_bandwidth_out = 0.0;
+  }
+
+  if (smartlist_len(sl) == 0) {
+    log_info(LD_CIRC,
+             "Empty routerlist passed in to consensus weight node "
+             "selection for rule %s",
+             bandwidth_weight_rule_to_string(rule));
+    return -1;
+  }
+
+  weight_scale = networkstatus_get_weight_scale_param(NULL);
+
+  if (rule == WEIGHT_FOR_GUARD) {
+    Wg = networkstatus_get_bw_weight(NULL, "Wgg", -1);
+    Wm = networkstatus_get_bw_weight(NULL, "Wgm", -1); /* Bridges */
+    We = 0;
+    Wd = networkstatus_get_bw_weight(NULL, "Wgd", -1);
+
+    Wgb = networkstatus_get_bw_weight(NULL, "Wgb", -1);
+    Wmb = networkstatus_get_bw_weight(NULL, "Wmb", -1);
+    Web = networkstatus_get_bw_weight(NULL, "Web", -1);
+    Wdb = networkstatus_get_bw_weight(NULL, "Wdb", -1);
+  } else if (rule == WEIGHT_FOR_MID) {
+    Wg = networkstatus_get_bw_weight(NULL, "Wmg", -1);
+    Wm = networkstatus_get_bw_weight(NULL, "Wmm", -1);
+    We = networkstatus_get_bw_weight(NULL, "Wme", -1);
+    Wd = networkstatus_get_bw_weight(NULL, "Wmd", -1);
+
+    Wgb = networkstatus_get_bw_weight(NULL, "Wgb", -1);
+    Wmb = networkstatus_get_bw_weight(NULL, "Wmb", -1);
+    Web = networkstatus_get_bw_weight(NULL, "Web", -1);
+    Wdb = networkstatus_get_bw_weight(NULL, "Wdb", -1);
+  } else if (rule == WEIGHT_FOR_EXIT) {
+    // Guards CAN be exits if they have weird exit policies
+    // They are d then I guess...
+    We = networkstatus_get_bw_weight(NULL, "Wee", -1);
+    Wm = networkstatus_get_bw_weight(NULL, "Wem", -1); /* Odd exit policies */
+    Wd = networkstatus_get_bw_weight(NULL, "Wed", -1);
+    Wg = networkstatus_get_bw_weight(NULL, "Weg", -1); /* Odd exit policies */
+
+    Wgb = networkstatus_get_bw_weight(NULL, "Wgb", -1);
+    Wmb = networkstatus_get_bw_weight(NULL, "Wmb", -1);
+    Web = networkstatus_get_bw_weight(NULL, "Web", -1);
+    Wdb = networkstatus_get_bw_weight(NULL, "Wdb", -1);
+  } else if (rule == WEIGHT_FOR_DIR) {
+    We = networkstatus_get_bw_weight(NULL, "Wbe", -1);
+    Wm = networkstatus_get_bw_weight(NULL, "Wbm", -1);
+    Wd = networkstatus_get_bw_weight(NULL, "Wbd", -1);
+    Wg = networkstatus_get_bw_weight(NULL, "Wbg", -1);
+
+    Wgb = Wmb = Web = Wdb = weight_scale;
+  } else if (rule == NO_WEIGHTING) {
+    Wg = Wm = We = Wd = weight_scale;
+    Wgb = Wmb = Web = Wdb = weight_scale;
+  }
+
+  if (Wg < 0 || Wm < 0 || We < 0 || Wd < 0 || Wgb < 0 || Wmb < 0 || Wdb < 0
+      || Web < 0) {
+    log_debug(LD_CIRC,
+              "Got negative bandwidth weights. Defaulting to naive selection"
+              " algorithm.");
+    Wg = Wm = We = Wd = weight_scale;
+    Wgb = Wmb = Web = Wdb = weight_scale;
+  }
+
+  Wg /= weight_scale;
+  Wm /= weight_scale;
+  We /= weight_scale;
+  Wd /= weight_scale;
+
+  Wgb /= weight_scale;
+  Wmb /= weight_scale;
+  Web /= weight_scale;
+  Wdb /= weight_scale;
+
+  bandwidths = tor_calloc(smartlist_len(sl), sizeof(double));
+
+  // Cycle through smartlist and total the bandwidth.
+  static int warned_missing_bw = 0;
+  SMARTLIST_FOREACH_BEGIN(sl, const node_t *, node) {
+    int is_exit = 0, is_guard = 0, is_dir = 0, this_bw = 0;
+    double weight = 1;
+    double weight_without_guard_flag = 0; /* Used for guardfraction */
+    double final_weight = 0;
+    is_exit = node->is_exit && ! node->is_bad_exit;
+    is_guard = node->is_possible_guard;
+    is_dir = node_is_dir(node);
+    if (node->rs) {
+      if (!node->rs->has_bandwidth) {
+        /* This should never happen, unless all the authorities downgrade
+         * to 0.2.0 or rogue routerstatuses get inserted into our consensus. */
+        if (! warned_missing_bw) {
+          log_warn(LD_BUG,
+                 "Consensus is missing some bandwidths. Using a naive "
+                 "router selection algorithm");
+          warned_missing_bw = 1;
+        }
+        this_bw = 30000; /* Chosen arbitrarily */
+      } else {
+        this_bw = kb_to_bytes(node->rs->bandwidth_kb);
+      }
+    } else if (node->ri) {
+      /* bridge or other descriptor not in our consensus */
+      this_bw = bridge_get_advertised_bandwidth_bounded(node->ri);
+    } else {
+      /* We can't use this one. */
+      continue;
+    }
+
+    if (is_guard && is_exit) {
+      weight = (is_dir ? Wdb*Wd : Wd);
+      weight_without_guard_flag = (is_dir ? Web*We : We);
+    } else if (is_guard) {
+      weight = (is_dir ? Wgb*Wg : Wg);
+      weight_without_guard_flag = (is_dir ? Wmb*Wm : Wm);
+    } else if (is_exit) {
+      weight = (is_dir ? Web*We : We);
+    } else { // middle
+      weight = (is_dir ? Wmb*Wm : Wm);
+    }
+    /* These should be impossible; but overflows here would be bad, so let's
+     * make sure. */
+    if (this_bw < 0)
+      this_bw = 0;
+    if (weight < 0.0)
+      weight = 0.0;
+    if (weight_without_guard_flag < 0.0)
+      weight_without_guard_flag = 0.0;
+
+    /* If guardfraction information is available in the consensus, we
+     * want to calculate this router's bandwidth according to its
+     * guardfraction. Quoting from proposal236:
+     *
+     *    Let Wpf denote the weight from the 'bandwidth-weights' line a
+     *    client would apply to N for position p if it had the guard
+     *    flag, Wpn the weight if it did not have the guard flag, and B the
+     *    measured bandwidth of N in the consensus.  Then instead of choosing
+     *    N for position p proportionally to Wpf*B or Wpn*B, clients should
+     *    choose N proportionally to F*Wpf*B + (1-F)*Wpn*B.
+     */
+    if (node->rs && node->rs->has_guardfraction && rule != WEIGHT_FOR_GUARD) {
+      /* XXX The assert should actually check for is_guard. However,
+       * that crashes dirauths because of #13297. This should be
+       * equivalent: */
+      tor_assert(node->rs->is_possible_guard);
+
+      guard_get_guardfraction_bandwidth(&guardfraction_bw,
+                                        this_bw,
+                                        node->rs->guardfraction_percentage);
+
+      /* Calculate final_weight = F*Wpf*B + (1-F)*Wpn*B */
+      final_weight =
+        guardfraction_bw.guard_bw * weight +
+        guardfraction_bw.non_guard_bw * weight_without_guard_flag;
+
+      log_debug(LD_GENERAL, "%s: Guardfraction weight %f instead of %f (%s)",
+                node->rs->nickname, final_weight, weight*this_bw,
+                bandwidth_weight_rule_to_string(rule));
+    } else { /* no guardfraction information. calculate the weight normally. */
+      final_weight = weight*this_bw;
+    }
+
+    bandwidths[node_sl_idx] = final_weight;
+    total_bandwidth += final_weight;
+  } SMARTLIST_FOREACH_END(node);
+
+  log_debug(LD_CIRC, "Generated weighted bandwidths for rule %s based "
+            "on weights "
+            "Wg=%f Wm=%f We=%f Wd=%f with total bw %f",
+            bandwidth_weight_rule_to_string(rule),
+            Wg, Wm, We, Wd, total_bandwidth);
+
+  *bandwidths_out = bandwidths;
+
+  if (total_bandwidth_out) {
+    *total_bandwidth_out = total_bandwidth;
+  }
+
+  return 0;
+}
+
+/** For all nodes in <b>sl</b>, return the fraction of those nodes, weighted
+ * by their weighted bandwidths with rule <b>rule</b>, for which we have
+ * descriptors.
+ *
+ * If <b>for_direct_connect</b> is true, we intend to connect to the node
+ * directly, as the first hop of a circuit; otherwise, we intend to connect
+ * to it indirectly, or use it as if we were connecting to it indirectly. */
+double
+frac_nodes_with_descriptors(const smartlist_t *sl,
+                            bandwidth_weight_rule_t rule,
+                            int for_direct_conn)
+{
+  double *bandwidths = NULL;
+  double total, present;
+
+  if (smartlist_len(sl) == 0)
+    return 0.0;
+
+  if (compute_weighted_bandwidths(sl, rule, &bandwidths, &total) < 0 ||
+      total <= 0.0) {
+    int n_with_descs = 0;
+    SMARTLIST_FOREACH(sl, const node_t *, node, {
+      if (node_has_preferred_descriptor(node, for_direct_conn))
+        n_with_descs++;
+    });
+    tor_free(bandwidths);
+    return ((double)n_with_descs) / smartlist_len(sl);
+  }
+
+  present = 0.0;
+  SMARTLIST_FOREACH_BEGIN(sl, const node_t *, node) {
+    if (node_has_preferred_descriptor(node, for_direct_conn))
+      present += bandwidths[node_sl_idx];
+  } SMARTLIST_FOREACH_END(node);
+
+  tor_free(bandwidths);
+
+  return present / total;
+}
+
+/** Choose a random element of status list <b>sl</b>, weighted by
+ * the advertised bandwidth of each node */
+const node_t *
+node_sl_choose_by_bandwidth(const smartlist_t *sl,
+                            bandwidth_weight_rule_t rule)
+{ /*XXXX MOVE */
+  return smartlist_choose_node_by_bandwidth_weights(sl, rule);
+}
+
+/** Given a <b>router</b>, add every node_t in its family (including the
+ * node itself!) to <b>sl</b>.
+ *
+ * Note the type mismatch: This function takes a routerinfo, but adds nodes
+ * to the smartlist!
+ */
+static void
+routerlist_add_node_and_family(smartlist_t *sl, const routerinfo_t *router)
+{
+  /* XXXX MOVE ? */
+  node_t fake_node;
+  const node_t *node = node_get_by_id(router->cache_info.identity_digest);
+  if (node == NULL) {
+    memset(&fake_node, 0, sizeof(fake_node));
+    fake_node.ri = (routerinfo_t *)router;
+    memcpy(fake_node.identity, router->cache_info.identity_digest, DIGEST_LEN);
+    node = &fake_node;
+  }
+  nodelist_add_node_and_family(sl, node);
+}
+
+/** Return a random running node from the nodelist. Never
+ * pick a node that is in
+ * <b>excludedsmartlist</b>, or which matches <b>excludedset</b>,
+ * even if they are the only nodes available.
+ * If <b>CRN_NEED_UPTIME</b> is set in flags and any router has more than
+ * a minimum uptime, return one of those.
+ * If <b>CRN_NEED_CAPACITY</b> is set in flags, weight your choice by the
+ * advertised capacity of each router.
+ * If <b>CRN_NEED_GUARD</b> is set in flags, consider only Guard routers.
+ * If <b>CRN_WEIGHT_AS_EXIT</b> is set in flags, we weight bandwidths as if
+ * picking an exit node, otherwise we weight bandwidths for picking a relay
+ * node (that is, possibly discounting exit nodes).
+ * If <b>CRN_NEED_DESC</b> is set in flags, we only consider nodes that
+ * have a routerinfo or microdescriptor -- that is, enough info to be
+ * used to build a circuit.
+ * If <b>CRN_PREF_ADDR</b> is set in flags, we only consider nodes that
+ * have an address that is preferred by the ClientPreferIPv6ORPort setting
+ * (regardless of this flag, we exclude nodes that aren't allowed by the
+ * firewall, including ClientUseIPv4 0 and fascist_firewall_use_ipv6() == 0).
+ */
+const node_t *
+router_choose_random_node(smartlist_t *excludedsmartlist,
+                          routerset_t *excludedset,
+                          router_crn_flags_t flags)
+{ /* XXXX MOVE */
+  const int need_uptime = (flags & CRN_NEED_UPTIME) != 0;
+  const int need_capacity = (flags & CRN_NEED_CAPACITY) != 0;
+  const int need_guard = (flags & CRN_NEED_GUARD) != 0;
+  const int weight_for_exit = (flags & CRN_WEIGHT_AS_EXIT) != 0;
+  const int need_desc = (flags & CRN_NEED_DESC) != 0;
+  const int pref_addr = (flags & CRN_PREF_ADDR) != 0;
+  const int direct_conn = (flags & CRN_DIRECT_CONN) != 0;
+  const int rendezvous_v3 = (flags & CRN_RENDEZVOUS_V3) != 0;
+
+  smartlist_t *sl=smartlist_new(),
+    *excludednodes=smartlist_new();
+  const node_t *choice = NULL;
+  const routerinfo_t *r;
+  bandwidth_weight_rule_t rule;
+
+  tor_assert(!(weight_for_exit && need_guard));
+  rule = weight_for_exit ? WEIGHT_FOR_EXIT :
+    (need_guard ? WEIGHT_FOR_GUARD : WEIGHT_FOR_MID);
+
+  SMARTLIST_FOREACH_BEGIN(nodelist_get_list(), node_t *, node) {
+    if (node_allows_single_hop_exits(node)) {
+      /* Exclude relays that allow single hop exit circuits. This is an
+       * obsolete option since 0.2.9.2-alpha and done by default in
+       * 0.3.1.0-alpha. */
+      smartlist_add(excludednodes, node);
+    } else if (rendezvous_v3 &&
+               !node_supports_v3_rendezvous_point(node)) {
+      /* Exclude relays that do not support to rendezvous for a hidden service
+       * version 3. */
+      smartlist_add(excludednodes, node);
+    }
+  } SMARTLIST_FOREACH_END(node);
+
+  /* If the node_t is not found we won't be to exclude ourself but we
+   * won't be able to pick ourself in router_choose_random_node() so
+   * this is fine to at least try with our routerinfo_t object. */
+  if ((r = router_get_my_routerinfo()))
+    routerlist_add_node_and_family(excludednodes, r);
+
+  router_add_running_nodes_to_smartlist(sl, need_uptime, need_capacity,
+                                        need_guard, need_desc, pref_addr,
+                                        direct_conn);
+  log_debug(LD_CIRC,
+           "We found %d running nodes.",
+            smartlist_len(sl));
+
+  smartlist_subtract(sl,excludednodes);
+  log_debug(LD_CIRC,
+            "We removed %d excludednodes, leaving %d nodes.",
+            smartlist_len(excludednodes),
+            smartlist_len(sl));
+
+  if (excludedsmartlist) {
+    smartlist_subtract(sl,excludedsmartlist);
+    log_debug(LD_CIRC,
+              "We removed %d excludedsmartlist, leaving %d nodes.",
+              smartlist_len(excludedsmartlist),
+              smartlist_len(sl));
+  }
+  if (excludedset) {
+    routerset_subtract_nodes(sl,excludedset);
+    log_debug(LD_CIRC,
+              "We removed excludedset, leaving %d nodes.",
+              smartlist_len(sl));
+  }
+
+  // Always weight by bandwidth
+  choice = node_sl_choose_by_bandwidth(sl, rule);
+
+  smartlist_free(sl);
+  if (!choice && (need_uptime || need_capacity || need_guard || pref_addr)) {
+    /* try once more -- recurse but with fewer restrictions. */
+    log_info(LD_CIRC,
+             "We couldn't find any live%s%s%s routers; falling back "
+             "to list of all routers.",
+             need_capacity?", fast":"",
+             need_uptime?", stable":"",
+             need_guard?", guard":"");
+    flags &= ~ (CRN_NEED_UPTIME|CRN_NEED_CAPACITY|CRN_NEED_GUARD|
+                CRN_PREF_ADDR);
+    choice = router_choose_random_node(
+                     excludedsmartlist, excludedset, flags);
+  }
+  smartlist_free(excludednodes);
+  if (!choice) {
+    log_warn(LD_CIRC,
+             "No available nodes when trying to choose node. Failing.");
+  }
+  return choice;
+}
+
+/** Try to find a running directory authority. Flags are as for
+ * router_pick_directory_server.
+ */
+const routerstatus_t *
+router_pick_trusteddirserver(dirinfo_type_t type, int flags)
+{
+  return router_pick_dirserver_generic(
+                                  router_get_trusted_dir_servers_mutable(),
+                                  type, flags);
+}
+
+/** Try to find a running fallback directory. Flags are as for
+ * router_pick_directory_server.
+ */
+const routerstatus_t *
+router_pick_fallback_dirserver(dirinfo_type_t type, int flags)
+{
+  return router_pick_dirserver_generic(
+                                  router_get_fallback_dir_servers_mutable(),
+                                  type, flags);
+}
+
+/** Pick a random element from a list of dir_server_t, weighting by their
+ * <b>weight</b> field. */
+static const dir_server_t *
+dirserver_choose_by_weight(const smartlist_t *servers, double authority_weight)
+{
+  int n = smartlist_len(servers);
+  int i;
+  double *weights_dbl;
+  uint64_t *weights_u64;
+  const dir_server_t *ds;
+
+  weights_dbl = tor_calloc(n, sizeof(double));
+  weights_u64 = tor_calloc(n, sizeof(uint64_t));
+  for (i = 0; i < n; ++i) {
+    ds = smartlist_get(servers, i);
+    weights_dbl[i] = ds->weight;
+    if (ds->is_authority)
+      weights_dbl[i] *= authority_weight;
+  }
+
+  scale_array_elements_to_u64(weights_u64, weights_dbl, n, NULL);
+  i = choose_array_element_by_weight(weights_u64, n);
+  tor_free(weights_dbl);
+  tor_free(weights_u64);
+  return (i < 0) ? NULL : smartlist_get(servers, i);
+}
+
+/** Choose randomly from among the dir_server_ts in sourcelist that
+ * are up. Flags are as for router_pick_directory_server_impl().
+ */
+static const routerstatus_t *
+router_pick_trusteddirserver_impl(const smartlist_t *sourcelist,
+                                  dirinfo_type_t type, int flags,
+                                  int *n_busy_out)
+{
+  const or_options_t *options = get_options();
+  smartlist_t *direct, *tunnel;
+  smartlist_t *overloaded_direct, *overloaded_tunnel;
+  const routerinfo_t *me = router_get_my_routerinfo();
+  const routerstatus_t *result = NULL;
+  time_t now = time(NULL);
+  const int requireother = ! (flags & PDS_ALLOW_SELF);
+  const int fascistfirewall = ! (flags & PDS_IGNORE_FASCISTFIREWALL);
+  const int no_serverdesc_fetching =(flags & PDS_NO_EXISTING_SERVERDESC_FETCH);
+  const int no_microdesc_fetching =(flags & PDS_NO_EXISTING_MICRODESC_FETCH);
+  const double auth_weight =
+    (sourcelist == router_get_fallback_dir_servers()) ?
+    options->DirAuthorityFallbackRate : 1.0;
+  smartlist_t *pick_from;
+  int n_busy = 0;
+  int try_excluding = 1, n_excluded = 0;
+  int try_ip_pref = 1;
+
+  if (!sourcelist)
+    return NULL;
+
+ retry_search:
+
+  direct = smartlist_new();
+  tunnel = smartlist_new();
+  overloaded_direct = smartlist_new();
+  overloaded_tunnel = smartlist_new();
+
+  const int skip_or_fw = router_skip_or_reachability(options, try_ip_pref);
+  const int skip_dir_fw = router_skip_dir_reachability(options, try_ip_pref);
+  const int must_have_or = directory_must_use_begindir(options);
+
+  SMARTLIST_FOREACH_BEGIN(sourcelist, const dir_server_t *, d)
+    {
+      int is_overloaded =
+          d->fake_status.last_dir_503_at + DIR_503_TIMEOUT > now;
+      if (!d->is_running) continue;
+      if ((type & d->type) == 0)
+        continue;
+
+      SKIP_MISSING_TRUSTED_EXTRAINFO(type, d->digest);
+
+      if (requireother && me && router_digest_is_me(d->digest))
+        continue;
+      if (try_excluding &&
+          routerset_contains_routerstatus(options->ExcludeNodes,
+                                          &d->fake_status, -1)) {
+        ++n_excluded;
+        continue;
+      }
+
+      if (router_is_already_dir_fetching_(d->addr,
+                                          &d->ipv6_addr,
+                                          d->dir_port,
+                                          no_serverdesc_fetching,
+                                          no_microdesc_fetching)) {
+        ++n_busy;
+        continue;
+      }
+
+      /* Clients use IPv6 addresses if the server has one and the client
+       * prefers IPv6.
+       * Add the router if its preferred address and port are reachable.
+       * If we don't get any routers, we'll try again with the non-preferred
+       * address for each router (if any). (To ensure correct load-balancing
+       * we try routers that only have one address both times.)
+       */
+      if (!fascistfirewall || skip_or_fw ||
+          fascist_firewall_allows_dir_server(d, FIREWALL_OR_CONNECTION,
+                                             try_ip_pref))
+        smartlist_add(is_overloaded ? overloaded_tunnel : tunnel, (void*)d);
+      else if (!must_have_or && (skip_dir_fw ||
+               fascist_firewall_allows_dir_server(d, FIREWALL_DIR_CONNECTION,
+                                                  try_ip_pref)))
+        smartlist_add(is_overloaded ? overloaded_direct : direct, (void*)d);
+    }
+  SMARTLIST_FOREACH_END(d);
+
+  if (smartlist_len(tunnel)) {
+    pick_from = tunnel;
+  } else if (smartlist_len(overloaded_tunnel)) {
+    pick_from = overloaded_tunnel;
+  } else if (smartlist_len(direct)) {
+    pick_from = direct;
+  } else {
+    pick_from = overloaded_direct;
+  }
+
+  {
+    const dir_server_t *selection =
+      dirserver_choose_by_weight(pick_from, auth_weight);
+
+    if (selection)
+      result = &selection->fake_status;
+  }
+
+  smartlist_free(direct);
+  smartlist_free(tunnel);
+  smartlist_free(overloaded_direct);
+  smartlist_free(overloaded_tunnel);
+
+  RETRY_ALTERNATE_IP_VERSION(retry_search);
+
+  RETRY_WITHOUT_EXCLUDE(retry_search);
+
+  router_picked_poor_directory_log(result);
+
+  if (n_busy_out)
+    *n_busy_out = n_busy;
+  return result;
+}