Merge branch 'maint-0.4.8'

[tor.git] / src / core / or / policies.c

/* Copyright (c) 2001-2004, Roger Dingledine.
 * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
 * Copyright (c) 2007-2021, The Tor Project, Inc. */
/* See LICENSE for licensing information */

/**
 * \file policies.c
 * \brief Code to parse and use address policies and exit policies.
 *
 * We have two key kinds of address policy: full and compressed.  A full
 * policy is an array of accept/reject patterns, to be applied in order.
 * A short policy is simply a list of ports.  This module handles both
 * kinds, including generic functions to apply them to addresses, and
 * also including code to manage the global policies that we apply to
 * incoming and outgoing connections.
 **/

#define POLICIES_PRIVATE

#include "core/or/or.h"
#include "feature/client/bridges.h"
#include "app/config/config.h"
#include "core/or/policies.h"
#include "feature/dirparse/policy_parse.h"
#include "feature/nodelist/microdesc.h"
#include "feature/nodelist/networkstatus.h"
#include "feature/nodelist/nodelist.h"
#include "feature/relay/router.h"
#include "feature/relay/routermode.h"
#include "lib/geoip/geoip.h"
#include "ht.h"
#include "lib/crypt_ops/crypto_rand.h"
#include "lib/encoding/confline.h"
#include "trunnel/ed25519_cert.h"

#include "core/or/addr_policy_st.h"
#include "feature/dirclient/dir_server_st.h"
#include "feature/nodelist/microdesc_st.h"
#include "feature/nodelist/node_st.h"
#include "core/or/port_cfg_st.h"
#include "feature/nodelist/routerinfo_st.h"
#include "feature/nodelist/routerstatus_st.h"

/** Maximum length of an exit policy summary. */
#define MAX_EXITPOLICY_SUMMARY_LEN 1000

/** Policy that addresses for incoming SOCKS connections must match. */
static smartlist_t *socks_policy = NULL;
/** Policy that addresses for incoming directory connections must match. */
static smartlist_t *dir_policy = NULL;
/** Policy for incoming MetricsPort connections that must match. */
static smartlist_t *metrics_policy = NULL;
/** Policy that addresses for incoming router descriptors must match in order
 * to be published by us. */
static smartlist_t *authdir_reject_policy = NULL;
/** Policy that addresses for incoming router descriptors must match in order
 * to be marked as valid in our networkstatus. */
static smartlist_t *authdir_invalid_policy = NULL;
/** Policy that addresses for incoming router descriptors must <b>not</b>
 * match in order to not be marked as BadExit. */
static smartlist_t *authdir_badexit_policy = NULL;
/** Policy that addresses for incoming router descriptors must <b>not</b>
 * match in order to not be marked as MiddleOnly. */
static smartlist_t *authdir_middleonly_policy = NULL;

/** Parsed addr_policy_t describing which addresses we believe we can start
 * circuits at. */
static smartlist_t *reachable_or_addr_policy = NULL;
/** Parsed addr_policy_t describing which addresses we believe we can connect
 * to directories at. */
static smartlist_t *reachable_dir_addr_policy = NULL;

/** Element of an exit policy summary */
typedef struct policy_summary_item_t {
    uint16_t prt_min; /**< Lowest port number to accept/reject. */
    uint16_t prt_max; /**< Highest port number to accept/reject. */
    uint64_t reject_count; /**< Number of IP-Addresses that are rejected to
                                this port range. */
    unsigned int accepted:1; /** Has this port already been accepted */
} policy_summary_item_t;

/** Private networks.  This list is used in two places, once to expand the
 *  "private" keyword when parsing our own exit policy, secondly to ignore
 *  just such networks when building exit policy summaries.  It is important
 *  that all authorities agree on that list when creating summaries, so don't
 *  just change this without a proper migration plan and a proposal and stuff.
 */
static const char *private_nets[] = {
  "0.0.0.0/8", "169.254.0.0/16",
  "127.0.0.0/8", "192.168.0.0/16", "10.0.0.0/8", "172.16.0.0/12",
  "[::]/8",
  "[fc00::]/7", "[fe80::]/10", "[fec0::]/10", "[ff00::]/8", "[::]/127",
  NULL
};

static int policies_parse_exit_policy_internal(
                                      config_line_t *cfg,
                                      smartlist_t **dest,
                                      int ipv6_exit,
                                      int rejectprivate,
                                      const smartlist_t *configured_addresses,
                                      int reject_interface_addresses,
                                      int reject_configured_port_addresses,
                                      int add_default_policy,
                                      int add_reduced_policy);

/** Replace all "private" entries in *<b>policy</b> with their expanded
 * equivalents. */
void
policy_expand_private(smartlist_t **policy)
{
  uint16_t port_min, port_max;

  int i;
  smartlist_t *tmp;

  if (!*policy) /*XXXX disallow NULL policies? */
    return;

  tmp = smartlist_new();

  SMARTLIST_FOREACH_BEGIN(*policy, addr_policy_t *, p) {
     if (! p->is_private) {
       smartlist_add(tmp, p);
       continue;
     }
     for (i = 0; private_nets[i]; ++i) {
       addr_policy_t newpolicy;
       memcpy(&newpolicy, p, sizeof(addr_policy_t));
       newpolicy.is_private = 0;
       newpolicy.is_canonical = 0;
       if (tor_addr_parse_mask_ports(private_nets[i], 0,
                               &newpolicy.addr,
                               &newpolicy.maskbits, &port_min, &port_max)<0) {
         tor_assert_unreached();
       }
       smartlist_add(tmp, addr_policy_get_canonical_entry(&newpolicy));
     }
     addr_policy_free(p);
  } SMARTLIST_FOREACH_END(p);

  smartlist_free(*policy);
  *policy = tmp;
}

/** Expand each of the AF_UNSPEC elements in *<b>policy</b> (which indicate
 * protocol-neutral wildcards) into a pair of wildcard elements: one IPv4-
 * specific and one IPv6-specific. */
void
policy_expand_unspec(smartlist_t **policy)
{
  smartlist_t *tmp;
  if (!*policy)
    return;

  tmp = smartlist_new();
  SMARTLIST_FOREACH_BEGIN(*policy, addr_policy_t *, p) {
    sa_family_t family = tor_addr_family(&p->addr);
    if (family == AF_INET6 || family == AF_INET || p->is_private) {
      smartlist_add(tmp, p);
    } else if (family == AF_UNSPEC) {
      addr_policy_t newpolicy_ipv4;
      addr_policy_t newpolicy_ipv6;
      memcpy(&newpolicy_ipv4, p, sizeof(addr_policy_t));
      memcpy(&newpolicy_ipv6, p, sizeof(addr_policy_t));
      newpolicy_ipv4.is_canonical = 0;
      newpolicy_ipv6.is_canonical = 0;
      if (p->maskbits != 0) {
        log_warn(LD_BUG, "AF_UNSPEC policy with maskbits==%d", p->maskbits);
        newpolicy_ipv4.maskbits = 0;
        newpolicy_ipv6.maskbits = 0;
      }
      tor_addr_from_ipv4h(&newpolicy_ipv4.addr, 0);
      tor_addr_from_ipv6_bytes(&newpolicy_ipv6.addr,
          (const uint8_t *)"\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0");
      smartlist_add(tmp, addr_policy_get_canonical_entry(&newpolicy_ipv4));
      smartlist_add(tmp, addr_policy_get_canonical_entry(&newpolicy_ipv6));
      addr_policy_free(p);
    } else {
      log_warn(LD_BUG, "Funny-looking address policy with family %d", family);
      smartlist_add(tmp, p);
    }
  } SMARTLIST_FOREACH_END(p);

  smartlist_free(*policy);
  *policy = tmp;
}

/**
 * Given a linked list of config lines containing "accept[6]" and "reject[6]"
 * tokens, parse them and append the result to <b>dest</b>. Return -1
 * if any tokens are malformed (and don't append any), else return 0.
 *
 * If <b>assume_action</b> is nonnegative, then insert its action
 * (ADDR_POLICY_ACCEPT or ADDR_POLICY_REJECT) for items that specify no
 * action.
 */
static int
parse_addr_policy(config_line_t *cfg, smartlist_t **dest,
                  int assume_action)
{
  smartlist_t *result;
  smartlist_t *entries;
  addr_policy_t *item;
  int malformed_list;
  int r = 0;

  if (!cfg)
    return 0;

  result = smartlist_new();
  entries = smartlist_new();
  for (; cfg; cfg = cfg->next) {
    smartlist_split_string(entries, cfg->value, ",",
                           SPLIT_SKIP_SPACE|SPLIT_IGNORE_BLANK, 0);
    SMARTLIST_FOREACH_BEGIN(entries, const char *, ent) {
      log_debug(LD_CONFIG,"Adding new entry '%s'",ent);
      malformed_list = 0;
      item = router_parse_addr_policy_item_from_string(ent, assume_action,
                                                       &malformed_list);
      if (item) {
        smartlist_add(result, item);
      } else if (malformed_list) {
        /* the error is so severe the entire list should be discarded */
        log_warn(LD_CONFIG, "Malformed policy '%s'. Discarding entire policy "
                 "list.", ent);
        r = -1;
      } else {
        /* the error is minor: don't add the item, but keep processing the
         * rest of the policies in the list */
        log_debug(LD_CONFIG, "Ignored policy '%s' due to non-fatal error. "
                  "The remainder of the policy list will be used.",
                  ent);
      }
    } SMARTLIST_FOREACH_END(ent);
    SMARTLIST_FOREACH(entries, char *, ent, tor_free(ent));
    smartlist_clear(entries);
  }
  smartlist_free(entries);
  if (r == -1) {
    addr_policy_list_free(result);
  } else {
    policy_expand_private(&result);
    policy_expand_unspec(&result);

    if (*dest) {
      smartlist_add_all(*dest, result);
      smartlist_free(result);
    } else {
      *dest = result;
    }
  }

  return r;
}

/** Helper: parse the Reachable(Dir|OR)?Addresses fields into
 * reachable_(or|dir)_addr_policy.  The options should already have
 * been validated by validate_addr_policies.
 */
static int
parse_reachable_addresses(void)
{
  const or_options_t *options = get_options();
  int ret = 0;

  if (options->ReachableDirAddresses &&
      options->ReachableORAddresses &&
      options->ReachableAddresses) {
    log_warn(LD_CONFIG,
             "Both ReachableDirAddresses and ReachableORAddresses are set. "
             "ReachableAddresses setting will be ignored.");
  }
  addr_policy_list_free(reachable_or_addr_policy);
  reachable_or_addr_policy = NULL;
  if (!options->ReachableORAddresses && options->ReachableAddresses)
    log_info(LD_CONFIG,
             "Using ReachableAddresses as ReachableORAddresses.");
  if (parse_addr_policy(options->ReachableORAddresses ?
                          options->ReachableORAddresses :
                          options->ReachableAddresses,
                        &reachable_or_addr_policy, ADDR_POLICY_ACCEPT)) {
    log_warn(LD_CONFIG,
             "Error parsing Reachable%sAddresses entry; ignoring.",
             options->ReachableORAddresses ? "OR" : "");
    ret = -1;
  }

  addr_policy_list_free(reachable_dir_addr_policy);
  reachable_dir_addr_policy = NULL;
  if (!options->ReachableDirAddresses && options->ReachableAddresses)
    log_info(LD_CONFIG,
             "Using ReachableAddresses as ReachableDirAddresses");
  if (parse_addr_policy(options->ReachableDirAddresses ?
                          options->ReachableDirAddresses :
                          options->ReachableAddresses,
                        &reachable_dir_addr_policy, ADDR_POLICY_ACCEPT)) {
    if (options->ReachableDirAddresses)
      log_warn(LD_CONFIG,
               "Error parsing ReachableDirAddresses entry; ignoring.");
    ret = -1;
  }

  /* We ignore ReachableAddresses for relays */
  if (!server_mode(options)) {
    if (policy_is_reject_star(reachable_or_addr_policy, AF_UNSPEC, 0)
        || policy_is_reject_star(reachable_dir_addr_policy, AF_UNSPEC,0)) {
      log_warn(LD_CONFIG, "Tor cannot connect to the Internet if "
               "ReachableAddresses, ReachableORAddresses, or "
               "ReachableDirAddresses reject all addresses. Please accept "
               "some addresses in these options.");
    } else if (options->ClientUseIPv4 == 1
       && (policy_is_reject_star(reachable_or_addr_policy, AF_INET, 0)
           || policy_is_reject_star(reachable_dir_addr_policy, AF_INET, 0))) {
          log_warn(LD_CONFIG, "You have set ClientUseIPv4 1, but "
                   "ReachableAddresses, ReachableORAddresses, or "
                   "ReachableDirAddresses reject all IPv4 addresses. "
                   "Tor will not connect using IPv4.");
    } else if (reachable_addr_use_ipv6(options)
       && (policy_is_reject_star(reachable_or_addr_policy, AF_INET6, 0)
         || policy_is_reject_star(reachable_dir_addr_policy, AF_INET6, 0))) {
          log_warn(LD_CONFIG, "You have configured tor to use or prefer IPv6 "
                   "(or UseBridges 1), but "
                   "ReachableAddresses, ReachableORAddresses, or "
                   "ReachableDirAddresses reject all IPv6 addresses. "
                   "Tor will not connect using IPv6.");
    }
  }

  /* Append a reject *:* to reachable_(or|dir)_addr_policy */
  if (!ret && (options->ReachableDirAddresses ||
               options->ReachableORAddresses ||
               options->ReachableAddresses)) {
    append_exit_policy_string(&reachable_or_addr_policy, "reject *:*");
    append_exit_policy_string(&reachable_dir_addr_policy, "reject *:*");
  }

  return ret;
}

/* Return true iff ClientUseIPv4 0 or ClientUseIPv6 0 might block any OR or Dir
 * address:port combination. */
static int
firewall_is_fascist_impl(void)
{
  const or_options_t *options = get_options();
  /* Assume every non-bridge relay has an IPv4 address.
   * Clients which use bridges may only know the IPv6 address of their
   * bridge, but they will connect regardless of the ClientUseIPv6 setting. */
  return options->ClientUseIPv4 == 0;
}

/** Return true iff the firewall options, including ClientUseIPv4 0 and
 * ClientUseIPv6 0, might block any OR address:port combination.
 * Address preferences may still change which address is selected even if
 * this function returns false.
 */
int
firewall_is_fascist_or(void)
{
  return (reachable_or_addr_policy != NULL || firewall_is_fascist_impl());
}

/** Return true iff the firewall options, including ClientUseIPv4 0 and
 * ClientUseIPv6 0, might block any Dir address:port combination.
 * Address preferences may still change which address is selected even if
 * this function returns false.
 */
int
firewall_is_fascist_dir(void)
{
  return (reachable_dir_addr_policy != NULL || firewall_is_fascist_impl());
}

/** Return true iff <b>policy</b> (possibly NULL) will allow a
 * connection to <b>addr</b>:<b>port</b>.
 */
static int
addr_policy_permits_tor_addr(const tor_addr_t *addr, uint16_t port,
                            smartlist_t *policy)
{
  addr_policy_result_t p;
  p = compare_tor_addr_to_addr_policy(addr, port, policy);
  switch (p) {
    case ADDR_POLICY_PROBABLY_ACCEPTED:
    case ADDR_POLICY_ACCEPTED:
      return 1;
    case ADDR_POLICY_PROBABLY_REJECTED:
    case ADDR_POLICY_REJECTED:
      return 0;
    default:
      log_warn(LD_BUG, "Unexpected result: %d", (int)p);
      return 0;
  }
}

/** Return true iff we think our firewall will let us make a connection to
 * addr:port.
 *
 * If we are configured as a server, ignore any address family preference and
 * just use IPv4.
 * Otherwise:
 *  - return false for all IPv4 addresses:
 *    - if ClientUseIPv4 is 0, or
 *      if pref_only and pref_ipv6 are both true;
 *  - return false for all IPv6 addresses:
 *    - if reachable_addr_use_ipv6() is 0, or
 *    - if pref_only is true and pref_ipv6 is false.
 *
 * Return false if addr is NULL or tor_addr_is_null(), or if port is 0. */
STATIC int
reachable_addr_allows(const tor_addr_t *addr,
                                uint16_t port,
                                smartlist_t *firewall_policy,
                                int pref_only, int pref_ipv6)
{
  const or_options_t *options = get_options();
  const int client_mode = !server_mode(options);

  if (!addr || tor_addr_is_null(addr) || !port) {
    return 0;
  }

  /* Clients stop using IPv4 if it's disabled. In most cases, clients also
   * stop using IPv4 if it's not preferred.
   * Servers must have IPv4 enabled and preferred. */
  if (tor_addr_family(addr) == AF_INET && client_mode &&
      (!options->ClientUseIPv4 || (pref_only && pref_ipv6))) {
    return 0;
  }

  /* Clients and Servers won't use IPv6 unless it's enabled (and in most
   * cases, IPv6 must also be preferred before it will be used). */
  if (tor_addr_family(addr) == AF_INET6 &&
      (!reachable_addr_use_ipv6(options) || (pref_only && !pref_ipv6))) {
    return 0;
  }

  return addr_policy_permits_tor_addr(addr, port,
                                      firewall_policy);
}

/** Is this client configured to use IPv6?
 * Returns true if the client might use IPv6 for some of its connections
 * (including dual-stack and IPv6-only clients), and false if it will never
 * use IPv6 for any connections.
 * Use node_ipv6_or/dir_preferred() when checking a specific node and OR/Dir
 * port: it supports bridge client per-node IPv6 preferences.
 */
int
reachable_addr_use_ipv6(const or_options_t *options)
{
  /* Clients use IPv6 if it's set, or they use bridges, or they don't use
   * IPv4, or they prefer it.
   * ClientPreferIPv6DirPort is deprecated, but check it anyway. */
  return (options->ClientUseIPv6 == 1 || options->ClientUseIPv4 == 0 ||
          options->ClientPreferIPv6ORPort == 1 ||
          options->ClientPreferIPv6DirPort == 1 || options->UseBridges == 1);
}

/** Do we prefer to connect to IPv6, ignoring ClientPreferIPv6ORPort and
 * ClientPreferIPv6DirPort?
 * If we're unsure, return -1, otherwise, return 1 for IPv6 and 0 for IPv4.
 */
static int
reachable_addr_prefer_ipv6_impl(const or_options_t *options)
{
  /*
   Cheap implementation of config options ClientUseIPv4 & ClientUseIPv6 --
   If we're a server or IPv6 is disabled, use IPv4.
   If IPv4 is disabled, use IPv6.
   */

  if (server_mode(options) || !reachable_addr_use_ipv6(options)) {
    return 0;
  }

  if (!options->ClientUseIPv4) {
    return 1;
  }

  return -1;
}

/** Do we prefer to connect to IPv6 ORPorts?
 * Use node_ipv6_or_preferred() whenever possible: it supports bridge client
 * per-node IPv6 preferences.
 */
int
reachable_addr_prefer_ipv6_orport(const or_options_t *options)
{
  int pref_ipv6 = reachable_addr_prefer_ipv6_impl(options);

  if (pref_ipv6 >= 0) {
    return pref_ipv6;
  }

  /* We can use both IPv4 and IPv6 - which do we prefer? */
  if (options->ClientPreferIPv6ORPort == 1) {
    return 1;
  }

  return 0;
}

/** Do we prefer to connect to IPv6 DirPorts?
 *
 * (node_ipv6_dir_preferred() doesn't support bridge client per-node IPv6
 * preferences. There's no reason to use it instead of this function.)
 */
int
reachable_addr_prefer_ipv6_dirport(const or_options_t *options)
{
  int pref_ipv6 = reachable_addr_prefer_ipv6_impl(options);

  if (pref_ipv6 >= 0) {
    return pref_ipv6;
  }

  /* We can use both IPv4 and IPv6 - which do we prefer? */
  if (options->ClientPreferIPv6DirPort == 1) {
    return 1;
  }

  return 0;
}

/** Return true iff we think our firewall will let us make a connection to
 * addr:port. Uses ReachableORAddresses or ReachableDirAddresses based on
 * fw_connection.
 * If pref_only is true, return true if addr is in the client's preferred
 * address family, which is IPv6 if pref_ipv6 is true, and IPv4 otherwise.
 * If pref_only is false, ignore pref_ipv6, and return true if addr is allowed.
 */
int
reachable_addr_allows_addr(const tor_addr_t *addr, uint16_t port,
                                     firewall_connection_t fw_connection,
                                     int pref_only, int pref_ipv6)
{
  if (fw_connection == FIREWALL_OR_CONNECTION) {
    return reachable_addr_allows(addr, port,
                               reachable_or_addr_policy,
                               pref_only, pref_ipv6);
  } else if (fw_connection == FIREWALL_DIR_CONNECTION) {
    return reachable_addr_allows(addr, port,
                               reachable_dir_addr_policy,
                               pref_only, pref_ipv6);
  } else {
    log_warn(LD_BUG, "Bad firewall_connection_t value %d.",
             fw_connection);
    return 0;
  }
}

/** Return true iff we think our firewall will let us make a connection to
 * addr:port (ap). Uses ReachableORAddresses or ReachableDirAddresses based on
 * fw_connection.
 * pref_only and pref_ipv6 work as in reachable_addr_allows_addr().
 */
static int
reachable_addr_allows_ap(const tor_addr_port_t *ap,
                                   firewall_connection_t fw_connection,
                                   int pref_only, int pref_ipv6)
{
  tor_assert(ap);
  return reachable_addr_allows_addr(&ap->addr, ap->port,
                                              fw_connection, pref_only,
                                              pref_ipv6);
}

/** Return true iff we think our firewall will let us make a connection to
 * ipv4h_addr/ipv6_addr. Uses ipv4_orport/ipv6_orport/ReachableORAddresses or
 * ipv4_dirport/ipv6_dirport/ReachableDirAddresses based on IPv4/IPv6 and
 * <b>fw_connection</b>.
 * pref_only and pref_ipv6 work as in reachable_addr_allows_addr().
 */
static int
reachable_addr_allows_base(const tor_addr_t *ipv4_addr, uint16_t ipv4_orport,
                             uint16_t ipv4_dirport,
                             const tor_addr_t *ipv6_addr, uint16_t ipv6_orport,
                             uint16_t ipv6_dirport,
                             firewall_connection_t fw_connection,
                             int pref_only, int pref_ipv6)
{
  if (reachable_addr_allows_addr(ipv4_addr,
                                      (fw_connection == FIREWALL_OR_CONNECTION
                                       ? ipv4_orport
                                       : ipv4_dirport),
                                      fw_connection,
                                      pref_only, pref_ipv6)) {
    return 1;
  }

  if (reachable_addr_allows_addr(ipv6_addr,
                                      (fw_connection == FIREWALL_OR_CONNECTION
                                       ? ipv6_orport
                                       : ipv6_dirport),
                                      fw_connection,
                                      pref_only, pref_ipv6)) {
    return 1;
  }

  return 0;
}

/** Like reachable_addr_allows_base(), but takes ri. */
static int
reachable_addr_allows_ri_impl(const routerinfo_t *ri,
                                firewall_connection_t fw_connection,
                                int pref_only, int pref_ipv6)
{
  if (!ri) {
    return 0;
  }

  /* Assume IPv4 and IPv6 DirPorts are the same */
  return reachable_addr_allows_base(&ri->ipv4_addr, ri->ipv4_orport,
                                      ri->ipv4_dirport, &ri->ipv6_addr,
                                      ri->ipv6_orport, ri->ipv4_dirport,
                                      fw_connection, pref_only, pref_ipv6);
}

/** Like reachable_addr_allows_rs, but takes pref_ipv6. */
static int
reachable_addr_allows_rs_impl(const routerstatus_t *rs,
                                firewall_connection_t fw_connection,
                                int pref_only, int pref_ipv6)
{
  if (!rs) {
    return 0;
  }

  /* Assume IPv4 and IPv6 DirPorts are the same */
  return reachable_addr_allows_base(&rs->ipv4_addr, rs->ipv4_orport,
                                      rs->ipv4_dirport, &rs->ipv6_addr,
                                      rs->ipv6_orport, rs->ipv4_dirport,
                                      fw_connection, pref_only, pref_ipv6);
}

/** Like reachable_addr_allows_base(), but takes rs.
 * When rs is a fake_status from a dir_server_t, it can have a reachable
 * address, even when the corresponding node does not.
 * nodes can be missing addresses when there's no consensus (IPv4 and IPv6),
 * or when there is a microdescriptor consensus, but no microdescriptors
 * (microdescriptors have IPv6, the microdesc consensus does not). */
int
reachable_addr_allows_rs(const routerstatus_t *rs,
                           firewall_connection_t fw_connection, int pref_only)
{
  if (!rs) {
    return 0;
  }

  /* We don't have access to the node-specific IPv6 preference, so use the
   * generic IPv6 preference instead. */
  const or_options_t *options = get_options();
  int pref_ipv6 = (fw_connection == FIREWALL_OR_CONNECTION
                   ? reachable_addr_prefer_ipv6_orport(options)
                   : reachable_addr_prefer_ipv6_dirport(options));

  return reachable_addr_allows_rs_impl(rs, fw_connection, pref_only,
                                         pref_ipv6);
}

/** Return true iff we think our firewall will let us make a connection to
 * ipv6_addr:ipv6_orport based on ReachableORAddresses.
 * If <b>fw_connection</b> is FIREWALL_DIR_CONNECTION, returns 0.
 * pref_only and pref_ipv6 work as in reachable_addr_allows_addr().
 */
static int
reachable_addr_allows_md_impl(const microdesc_t *md,
                                firewall_connection_t fw_connection,
                                int pref_only, int pref_ipv6)
{
  if (!md) {
    return 0;
  }

  /* Can't check dirport, it doesn't have one */
  if (fw_connection == FIREWALL_DIR_CONNECTION) {
    return 0;
  }

  /* Also can't check IPv4, doesn't have that either */
  return reachable_addr_allows_addr(&md->ipv6_addr, md->ipv6_orport,
                                              fw_connection, pref_only,
                                              pref_ipv6);
}

/** Like reachable_addr_allows_base(), but takes node, and looks up pref_ipv6
 * from node_ipv6_or/dir_preferred(). */
int
reachable_addr_allows_node(const node_t *node,
                             firewall_connection_t fw_connection,
                             int pref_only)
{
  if (!node) {
    return 0;
  }

  node_assert_ok(node);

  const int pref_ipv6 = (fw_connection == FIREWALL_OR_CONNECTION
                         ? node_ipv6_or_preferred(node)
                         : node_ipv6_dir_preferred(node));

  /* Sometimes, the rs is missing the IPv6 address info, and we need to go
   * all the way to the md */
  if (node->ri && reachable_addr_allows_ri_impl(node->ri, fw_connection,
                                                  pref_only, pref_ipv6)) {
    return 1;
  } else if (node->rs && reachable_addr_allows_rs_impl(node->rs,
                                                         fw_connection,
                                                         pref_only,
                                                         pref_ipv6)) {
    return 1;
  } else if (node->md && reachable_addr_allows_md_impl(node->md,
                                                         fw_connection,
                                                         pref_only,
                                                         pref_ipv6)) {
    return 1;
  } else {
    /* If we know nothing, assume it's unreachable, we'll never get an address
     * to connect to. */
    return 0;
  }
}

/** Like reachable_addr_allows_rs(), but takes ds. */
int
reachable_addr_allows_dir_server(const dir_server_t *ds,
                                   firewall_connection_t fw_connection,
                                   int pref_only)
{
  if (!ds) {
    return 0;
  }

  /* A dir_server_t always has a fake_status. As long as it has the same
   * addresses/ports in both fake_status and dir_server_t, this works fine.
   * (See #17867.)
   * reachable_addr_allows_rs only checks the addresses in fake_status. */
  return reachable_addr_allows_rs(&ds->fake_status, fw_connection,
                                    pref_only);
}

/** If a and b are both valid and allowed by fw_connection,
 * choose one based on want_a and return it.
 * Otherwise, return whichever is allowed.
 * Otherwise, return NULL.
 * pref_only and pref_ipv6 work as in reachable_addr_allows_addr().
 */
static const tor_addr_port_t *
reachable_addr_choose_impl(const tor_addr_port_t *a,
                                     const tor_addr_port_t *b,
                                     int want_a,
                                     firewall_connection_t fw_connection,
                                     int pref_only, int pref_ipv6)
{
  const tor_addr_port_t *use_a = NULL;
  const tor_addr_port_t *use_b = NULL;

  if (reachable_addr_allows_ap(a, fw_connection, pref_only,
                                         pref_ipv6)) {
    use_a = a;
  }

  if (reachable_addr_allows_ap(b, fw_connection, pref_only,
                                         pref_ipv6)) {
    use_b = b;
  }

  /* If both are allowed */
  if (use_a && use_b) {
    /* Choose a if we want it */
    return (want_a ? use_a : use_b);
  } else {
    /* Choose a if we have it */
    return (use_a ? use_a : use_b);
  }
}

/** If a and b are both valid and preferred by fw_connection,
 * choose one based on want_a and return it.
 * Otherwise, return whichever is preferred.
 * If neither are preferred, and pref_only is false:
 *  - If a and b are both allowed by fw_connection,
 *    choose one based on want_a and return it.
 *  - Otherwise, return whichever is preferred.
 * Otherwise, return NULL. */
STATIC const tor_addr_port_t *
reachable_addr_choose(const tor_addr_port_t *a,
                                const tor_addr_port_t *b,
                                int want_a,
                                firewall_connection_t fw_connection,
                                int pref_only, int pref_ipv6)
{
  const tor_addr_port_t *pref = reachable_addr_choose_impl(
                                                                a, b, want_a,
                                                                fw_connection,
                                                                1, pref_ipv6);
  if (pref_only || pref) {
    /* If there is a preferred address, use it. If we can only use preferred
     * addresses, and neither address is preferred, pref will be NULL, and we
     * want to return NULL, so return it. */
    return pref;
  } else {
    /* If there's no preferred address, and we can return addresses that are
     * not preferred, use an address that's allowed */
    return reachable_addr_choose_impl(a, b, want_a, fw_connection,
                                                0, pref_ipv6);
  }
}

/** Copy an address and port into <b>ap</b> that we think our firewall will
 * let us connect to. Uses ipv4_addr/ipv6_addr and
 * ipv4_orport/ipv6_orport/ReachableORAddresses or
 * ipv4_dirport/ipv6_dirport/ReachableDirAddresses based on IPv4/IPv6 and
 * <b>fw_connection</b>.
 * If pref_only, only choose preferred addresses. In either case, choose
 * a preferred address before an address that's not preferred.
 * If both addresses could be chosen (they are both preferred or both allowed)
 * choose IPv6 if pref_ipv6 is true, otherwise choose IPv4. */
static void
reachable_addr_choose_base(const tor_addr_t *ipv4_addr,
                                     uint16_t ipv4_orport,
                                     uint16_t ipv4_dirport,
                                     const tor_addr_t *ipv6_addr,
                                     uint16_t ipv6_orport,
                                     uint16_t ipv6_dirport,
                                     firewall_connection_t fw_connection,
                                     int pref_only,
                                     int pref_ipv6,
                                     tor_addr_port_t* ap)
{
  const tor_addr_port_t *result = NULL;
  const int want_ipv4 = !pref_ipv6;

  tor_assert(ipv6_addr);
  tor_assert(ap);

  tor_addr_make_null(&ap->addr, AF_UNSPEC);
  ap->port = 0;

  tor_addr_port_t ipv4_ap;
  tor_addr_copy(&ipv4_ap.addr, ipv4_addr);
  ipv4_ap.port = (fw_connection == FIREWALL_OR_CONNECTION
                  ? ipv4_orport
                  : ipv4_dirport);

  tor_addr_port_t ipv6_ap;
  tor_addr_copy(&ipv6_ap.addr, ipv6_addr);
  ipv6_ap.port = (fw_connection == FIREWALL_OR_CONNECTION
                  ? ipv6_orport
                  : ipv6_dirport);

  result = reachable_addr_choose(&ipv4_ap, &ipv6_ap,
                                           want_ipv4,
                                           fw_connection, pref_only,
                                           pref_ipv6);

  if (result) {
    tor_addr_copy(&ap->addr, &result->addr);
    ap->port = result->port;
  }
}

/** Like reachable_addr_choose_base(), but takes <b>rs</b>.
 * Consults the corresponding node, then falls back to rs if node is NULL.
 * This should only happen when there's no valid consensus, and rs doesn't
 * correspond to a bridge client's bridge.
 */
void
reachable_addr_choose_from_rs(const routerstatus_t *rs,
                                   firewall_connection_t fw_connection,
                                   int pref_only, tor_addr_port_t* ap)
{
  tor_assert(ap);

  tor_addr_make_null(&ap->addr, AF_UNSPEC);
  ap->port = 0;

  if (!rs) {
    return;
  }

  const or_options_t *options = get_options();
  const node_t *node = node_get_by_id(rs->identity_digest);

  if (node) {
    reachable_addr_choose_from_node(node, fw_connection, pref_only, ap);
  } else {
    /* There's no node-specific IPv6 preference, so use the generic IPv6
     * preference instead. */
    int pref_ipv6 = (fw_connection == FIREWALL_OR_CONNECTION
                     ? reachable_addr_prefer_ipv6_orport(options)
                     : reachable_addr_prefer_ipv6_dirport(options));

    reachable_addr_choose_base(&rs->ipv4_addr, rs->ipv4_orport,
                                          rs->ipv4_dirport, &rs->ipv6_addr,
                                          rs->ipv6_orport, rs->ipv4_dirport,
                                          fw_connection, pref_only, pref_ipv6,
                                          ap);
  }
}

/** Like reachable_addr_choose_base(), but takes in a smartlist
 * <b>lspecs</b> consisting of one or more link specifiers. We assume
 * fw_connection is FIREWALL_OR_CONNECTION as link specifiers cannot
 * contain DirPorts.
 */
void
reachable_addr_choose_from_ls(const smartlist_t *lspecs,
                                   int pref_only, tor_addr_port_t* ap)
{
  int have_v4 = 0, have_v6 = 0;
  uint16_t port_v4 = 0, port_v6 = 0;
  tor_addr_t addr_v4, addr_v6;

  tor_assert(ap);

  if (lspecs == NULL) {
    log_warn(LD_BUG, "Unknown or missing link specifiers");
    return;
  }
  if (smartlist_len(lspecs) == 0) {
    log_warn(LD_PROTOCOL, "Link specifiers are empty");
    return;
  }

  tor_addr_make_null(&ap->addr, AF_UNSPEC);
  ap->port = 0;

  tor_addr_make_null(&addr_v4, AF_INET);
  tor_addr_make_null(&addr_v6, AF_INET6);

  SMARTLIST_FOREACH_BEGIN(lspecs, const link_specifier_t *, ls) {
    switch (link_specifier_get_ls_type(ls)) {
    case LS_IPV4:
      /* Skip if we already seen a v4. */
      if (have_v4) continue;
      tor_addr_from_ipv4h(&addr_v4,
                          link_specifier_get_un_ipv4_addr(ls));
      port_v4 = link_specifier_get_un_ipv4_port(ls);
      have_v4 = 1;
      break;
    case LS_IPV6:
      /* Skip if we already seen a v6, or deliberately skip it if we're not a
       * direct connection. */
      if (have_v6) continue;
      tor_addr_from_ipv6_bytes(&addr_v6,
          link_specifier_getconstarray_un_ipv6_addr(ls));
      port_v6 = link_specifier_get_un_ipv6_port(ls);
      have_v6 = 1;
      break;
    default:
      /* Ignore unknown. */
      break;
    }
  } SMARTLIST_FOREACH_END(ls);

  /* If we don't have IPv4 or IPv6 in link specifiers, log a bug and return. */
  if (!have_v4 && !have_v6) {
    if (!have_v6) {
      log_warn(LD_PROTOCOL, "None of our link specifiers have IPv4 or IPv6");
    } else {
      log_warn(LD_PROTOCOL, "None of our link specifiers have IPv4");
    }
    return;
  }

  /* Here, don't check for DirPorts as link specifiers are only used for
   * ORPorts. */
  const or_options_t *options = get_options();
  int pref_ipv6 = reachable_addr_prefer_ipv6_orport(options);
  /* Assume that the DirPorts are zero as link specifiers only use ORPorts. */
  reachable_addr_choose_base(&addr_v4, port_v4, 0,
                                       &addr_v6, port_v6, 0,
                                       FIREWALL_OR_CONNECTION,
                                       pref_only, pref_ipv6,
                                       ap);
}

/** Like reachable_addr_choose_base(), but takes <b>node</b>, and
 * looks up the node's IPv6 preference rather than taking an argument
 * for pref_ipv6. */
void
reachable_addr_choose_from_node(const node_t *node,
                                     firewall_connection_t fw_connection,
                                     int pref_only, tor_addr_port_t *ap)
{
  tor_assert(ap);

  tor_addr_make_null(&ap->addr, AF_UNSPEC);
  ap->port = 0;

  if (!node) {
    return;
  }

  node_assert_ok(node);

  const int pref_ipv6_node = (fw_connection == FIREWALL_OR_CONNECTION
                              ? node_ipv6_or_preferred(node)
                              : node_ipv6_dir_preferred(node));

  tor_addr_port_t ipv4_or_ap;
  node_get_prim_orport(node, &ipv4_or_ap);
  tor_addr_port_t ipv4_dir_ap;
  node_get_prim_dirport(node, &ipv4_dir_ap);

  tor_addr_port_t ipv6_or_ap;
  node_get_pref_ipv6_orport(node, &ipv6_or_ap);
  tor_addr_port_t ipv6_dir_ap;
  node_get_pref_ipv6_dirport(node, &ipv6_dir_ap);

  /* Assume the IPv6 OR and Dir addresses are the same. */
  reachable_addr_choose_base(&ipv4_or_ap.addr, ipv4_or_ap.port,
                                       ipv4_dir_ap.port, &ipv6_or_ap.addr,
                                       ipv6_or_ap.port, ipv6_dir_ap.port,
                                       fw_connection, pref_only,
                                       pref_ipv6_node, ap);
}

/** Like reachable_addr_choose_from_rs(), but takes <b>ds</b>. */
void
reachable_addr_choose_from_dir_server(const dir_server_t *ds,
                                           firewall_connection_t fw_connection,
                                           int pref_only,
                                           tor_addr_port_t *ap)
{
  tor_assert(ap);

  tor_addr_make_null(&ap->addr, AF_UNSPEC);
  ap->port = 0;

  if (!ds) {
    return;
  }

  /* A dir_server_t always has a fake_status. As long as it has the same
   * addresses/ports in both fake_status and dir_server_t, this works fine.
   * (See #17867.)
   * This function relies on reachable_addr_choose_from_rs looking up the
   * node if it can, because that will get the latest info for the relay. */
  reachable_addr_choose_from_rs(&ds->fake_status, fw_connection,
                                     pref_only, ap);
}

/** Return 1 if <b>addr</b> is permitted to connect to our dir port,
 * based on <b>dir_policy</b>. Else return 0.
 */
int
dir_policy_permits_address(const tor_addr_t *addr)
{
  return addr_policy_permits_tor_addr(addr, 1, dir_policy);
}

/** Return 1 if <b>addr</b> is permitted to connect to our socks port,
 * based on <b>socks_policy</b>. Else return 0.
 */
int
socks_policy_permits_address(const tor_addr_t *addr)
{
  return addr_policy_permits_tor_addr(addr, 1, socks_policy);
}

/** Return 1 if <b>addr</b> is permitted to connect to our metrics port,
 * based on <b>metrics_policy</b>. Else return 0.
 */
int
metrics_policy_permits_address(const tor_addr_t *addr)
{
  return addr_policy_permits_tor_addr(addr, 1, metrics_policy);
}

/** Return true iff the address <b>addr</b> is in a country listed in the
 * case-insensitive list of country codes <b>cc_list</b>. */
static int
addr_is_in_cc_list(const tor_addr_t *addr, const smartlist_t *cc_list)
{
  country_t country;
  const char *name;

  if (!cc_list)
    return 0;
  country = geoip_get_country_by_addr(addr);
  name = geoip_get_country_name(country);
  return smartlist_contains_string_case(cc_list, name);
}

/** Return 1 if <b>addr</b>:<b>port</b> is permitted to publish to our
 * directory, based on <b>authdir_reject_policy</b>. Else return 0.
 */
int
authdir_policy_permits_address(const tor_addr_t *addr, uint16_t port)
{
  if (!addr_policy_permits_tor_addr(addr, port, authdir_reject_policy))
    return 0;
  return !addr_is_in_cc_list(addr, get_options()->AuthDirRejectCCs);
}

/** Return 1 if <b>addr</b>:<b>port</b> is considered valid in our
 * directory, based on <b>authdir_invalid_policy</b>. Else return 0.
 */
int
authdir_policy_valid_address(const tor_addr_t *addr, uint16_t port)
{
  if (!addr_policy_permits_tor_addr(addr, port, authdir_invalid_policy))
    return 0;
  return !addr_is_in_cc_list(addr, get_options()->AuthDirInvalidCCs);
}

/** Return 1 if <b>addr</b>:<b>port</b> should be marked as a bad exit,
 * based on <b>authdir_badexit_policy</b>. Else return 0.
 */
int
authdir_policy_badexit_address(const tor_addr_t *addr, uint16_t port)
{
  if (!addr_policy_permits_tor_addr(addr, port, authdir_badexit_policy))
    return 1;
  return addr_is_in_cc_list(addr, get_options()->AuthDirBadExitCCs);
}

/** Return 1 if <b>addr</b>:<b>port</b> should be marked as MiddleOnly,
 * based on <b>authdir_middleonly_policy</b>. Else return 0.
 */
int
authdir_policy_middleonly_address(const tor_addr_t *addr, uint16_t port)
{
  if (!addr_policy_permits_tor_addr(addr, port, authdir_middleonly_policy))
    return 1;
  return addr_is_in_cc_list(addr, get_options()->AuthDirMiddleOnlyCCs);
}

#define REJECT(arg) \
  STMT_BEGIN *msg = tor_strdup(arg); goto err; STMT_END

/** Check <b>or_options</b> to determine whether or not we are using the
 * default options for exit policy. Return true if so, false otherwise. */
int
policy_using_default_exit_options(const or_options_t *or_options)
{
  return (or_options->ExitPolicy == NULL && or_options->ExitRelay == -1 &&
          or_options->ReducedExitPolicy == 0 && or_options->IPv6Exit == 0);
}

/** Config helper: If there's any problem with the policy configuration
 * options in <b>options</b>, return -1 and set <b>msg</b> to a newly
 * allocated description of the error. Else return 0. */
int
validate_addr_policies(const or_options_t *options, char **msg)
{
  /* XXXX Maybe merge this into parse_policies_from_options, to make sure
   * that the two can't go out of sync. */

  smartlist_t *addr_policy=NULL;
  *msg = NULL;

  if (policies_parse_exit_policy_from_options(options,0,NULL,&addr_policy)) {
    REJECT("Error in ExitPolicy entry.");
  }

  static int warned_about_nonexit = 0;

  if (public_server_mode(options) && !warned_about_nonexit &&
      policy_using_default_exit_options(options)) {
    warned_about_nonexit = 1;
    log_notice(LD_CONFIG, "By default, Tor does not run as an exit relay. "
               "If you want to be an exit relay, "
               "set ExitRelay to 1. To suppress this message in the future, "
               "set ExitRelay to 0.");
  }

  /* The rest of these calls *append* to addr_policy. So don't actually
   * use the results for anything other than checking if they parse! */
  if (parse_addr_policy(options->DirPolicy, &addr_policy, -1))
    REJECT("Error in DirPolicy entry.");
  if (parse_addr_policy(options->SocksPolicy, &addr_policy, -1))
    REJECT("Error in SocksPolicy entry.");
  if (parse_addr_policy(options->AuthDirReject, &addr_policy,
                        ADDR_POLICY_REJECT))
    REJECT("Error in AuthDirReject entry.");
  if (parse_addr_policy(options->AuthDirInvalid, &addr_policy,
                        ADDR_POLICY_REJECT))
    REJECT("Error in AuthDirInvalid entry.");
  if (parse_addr_policy(options->AuthDirBadExit, &addr_policy,
                        ADDR_POLICY_REJECT))
    REJECT("Error in AuthDirBadExit entry.");
  if (parse_addr_policy(options->AuthDirMiddleOnly, &addr_policy,
                        ADDR_POLICY_REJECT))
    REJECT("Error in AuthDirMiddleOnly entry.");

  if (parse_addr_policy(options->ReachableAddresses, &addr_policy,
                        ADDR_POLICY_ACCEPT))
    REJECT("Error in ReachableAddresses entry.");
  if (parse_addr_policy(options->ReachableORAddresses, &addr_policy,
                        ADDR_POLICY_ACCEPT))
    REJECT("Error in ReachableORAddresses entry.");
  if (parse_addr_policy(options->ReachableDirAddresses, &addr_policy,
                        ADDR_POLICY_ACCEPT))
    REJECT("Error in ReachableDirAddresses entry.");

 err:
  addr_policy_list_free(addr_policy);
  return *msg ? -1 : 0;
#undef REJECT
}

/** Parse <b>string</b> in the same way that the exit policy
 * is parsed, and put the processed version in *<b>policy</b>.
 * Ignore port specifiers.
 */
static int
load_policy_from_option(config_line_t *config, const char *option_name,
                        smartlist_t **policy,
                        int assume_action)
{
  int r;
  int killed_any_ports = 0;
  addr_policy_list_free(*policy);
  *policy = NULL;
  r = parse_addr_policy(config, policy, assume_action);
  if (r < 0) {
    return -1;
  }
  if (*policy) {
    SMARTLIST_FOREACH_BEGIN(*policy, addr_policy_t *, n) {
      /* ports aren't used in these. */
      if (n->prt_min > 1 || n->prt_max != 65535) {
        addr_policy_t newp, *c;
        memcpy(&newp, n, sizeof(newp));
        newp.prt_min = 1;
        newp.prt_max = 65535;
        newp.is_canonical = 0;
        c = addr_policy_get_canonical_entry(&newp);
        SMARTLIST_REPLACE_CURRENT(*policy, n, c);
        addr_policy_free(n);
        killed_any_ports = 1;
      }
    } SMARTLIST_FOREACH_END(n);
  }
  if (killed_any_ports) {
    log_warn(LD_CONFIG, "Ignoring ports in %s option.", option_name);
  }
  return 0;
}

/** Helper: Parse the MetricsPortPolicy option into the metrics_policy and set
 * the reject all by default.
 *
 * Return 0 on success else -1. */
static int
parse_metrics_port_policy(const or_options_t *options)
{
  if (load_policy_from_option(options->MetricsPortPolicy, "MetricsPortPolicy",
                              &metrics_policy, -1) < 0) {
    return -1;
  }
  /* It is a reject all by default. */
  append_exit_policy_string(&metrics_policy, "reject *:*");
  return 0;
}

/** Set all policies based on <b>options</b>, which should have been validated
 * first by validate_addr_policies. */
int
policies_parse_from_options(const or_options_t *options)
{
  int ret = 0;
  if (load_policy_from_option(options->SocksPolicy, "SocksPolicy",
                              &socks_policy, -1) < 0)
    ret = -1;
  if (load_policy_from_option(options->DirPolicy, "DirPolicy",
                              &dir_policy, -1) < 0)
    ret = -1;
  if (load_policy_from_option(options->AuthDirReject, "AuthDirReject",
                              &authdir_reject_policy, ADDR_POLICY_REJECT) < 0)
    ret = -1;
  if (load_policy_from_option(options->AuthDirInvalid, "AuthDirInvalid",
                              &authdir_invalid_policy, ADDR_POLICY_REJECT) < 0)
    ret = -1;
  if (load_policy_from_option(options->AuthDirBadExit, "AuthDirBadExit",
                              &authdir_badexit_policy, ADDR_POLICY_REJECT) < 0)
    ret = -1;
  if (load_policy_from_option(options->AuthDirMiddleOnly, "AuthDirMiddleOnly",
                         &authdir_middleonly_policy, ADDR_POLICY_REJECT) < 0)
    ret = -1;
  if (parse_metrics_port_policy(options) < 0) {
    ret = -1;
  }
  if (parse_reachable_addresses() < 0)
    ret = -1;
  return ret;
}

/** Compare two provided address policy items, and renturn -1, 0, or 1
 * if the first is less than, equal to, or greater than the second. */
static int
single_addr_policy_eq(const addr_policy_t *a, const addr_policy_t *b)
{
  int r;
#define CMP_FIELD(field) do {                   \
    if (a->field != b->field) {                 \
      return 0;                                 \
    }                                           \
  } while (0)
  CMP_FIELD(policy_type);
  CMP_FIELD(is_private);
  /* refcnt and is_canonical are irrelevant to equality,
   * they are hash table implementation details */
  if ((r=tor_addr_compare(&a->addr, &b->addr, CMP_EXACT)))
    return 0;
  CMP_FIELD(maskbits);
  CMP_FIELD(prt_min);
  CMP_FIELD(prt_max);
#undef CMP_FIELD
  return 1;
}

/** As single_addr_policy_eq, but compare every element of two policies.
 */
int
addr_policies_eq(const smartlist_t *a, const smartlist_t *b)
{
  int i;
  int len_a = a ? smartlist_len(a) : 0;
  int len_b = b ? smartlist_len(b) : 0;

  if (len_a != len_b)
    return 0;

  for (i = 0; i < len_a; ++i) {
    if (! single_addr_policy_eq(smartlist_get(a, i), smartlist_get(b, i)))
      return 0;
  }

  return 1;
}

/** Node in hashtable used to store address policy entries. */
typedef struct policy_map_ent_t {
  HT_ENTRY(policy_map_ent_t) node;
  addr_policy_t *policy;
} policy_map_ent_t;

/* DOCDOC policy_root */
static HT_HEAD(policy_map, policy_map_ent_t) policy_root = HT_INITIALIZER();

/** Return true iff a and b are equal. */
static inline int
policy_eq(policy_map_ent_t *a, policy_map_ent_t *b)
{
  return single_addr_policy_eq(a->policy, b->policy);
}

/** Return a hashcode for <b>ent</b> */
static unsigned int
policy_hash(const policy_map_ent_t *ent)
{
  const addr_policy_t *a = ent->policy;
  addr_policy_t aa;
  memset(&aa, 0, sizeof(aa));

  aa.prt_min = a->prt_min;
  aa.prt_max = a->prt_max;
  aa.maskbits = a->maskbits;
  aa.policy_type = a->policy_type;
  aa.is_private = a->is_private;

  if (a->is_private) {
    aa.is_private = 1;
  } else {
    tor_addr_copy_tight(&aa.addr, &a->addr);
  }

  return (unsigned) siphash24g(&aa, sizeof(aa));
}

HT_PROTOTYPE(policy_map, policy_map_ent_t, node, policy_hash,
             policy_eq);
HT_GENERATE2(policy_map, policy_map_ent_t, node, policy_hash,
             policy_eq, 0.6, tor_reallocarray_, tor_free_);

/** Given a pointer to an addr_policy_t, return a copy of the pointer to the
 * "canonical" copy of that addr_policy_t; the canonical copy is a single
 * reference-counted object. */
addr_policy_t *
addr_policy_get_canonical_entry(addr_policy_t *e)
{
  policy_map_ent_t search, *found;
  if (e->is_canonical)
    return e;

  search.policy = e;
  found = HT_FIND(policy_map, &policy_root, &search);
  if (!found) {
    found = tor_malloc_zero(sizeof(policy_map_ent_t));
    found->policy = tor_memdup(e, sizeof(addr_policy_t));
    found->policy->is_canonical = 1;
    found->policy->refcnt = 0;
    HT_INSERT(policy_map, &policy_root, found);
  }

  tor_assert(single_addr_policy_eq(found->policy, e));
  ++found->policy->refcnt;
  return found->policy;
}

/** Helper for compare_tor_addr_to_addr_policy.  Implements the case where
 * addr and port are both known. */
static addr_policy_result_t
compare_known_tor_addr_to_addr_policy(const tor_addr_t *addr, uint16_t port,
                                      const smartlist_t *policy)
{
  /* We know the address and port, and we know the policy, so we can just
   * compute an exact match. */
  SMARTLIST_FOREACH_BEGIN(policy, addr_policy_t *, tmpe) {
    if (tmpe->addr.family == AF_UNSPEC) {
      log_warn(LD_BUG, "Policy contains an AF_UNSPEC address, which only "
               "matches other AF_UNSPEC addresses.");
    }
    /* Address is known */
    if (!tor_addr_compare_masked(addr, &tmpe->addr, tmpe->maskbits,
                                 CMP_EXACT)) {
      if (port >= tmpe->prt_min && port <= tmpe->prt_max) {
        /* Exact match for the policy */
        return tmpe->policy_type == ADDR_POLICY_ACCEPT ?
          ADDR_POLICY_ACCEPTED : ADDR_POLICY_REJECTED;
      }
    }
  } SMARTLIST_FOREACH_END(tmpe);

  /* accept all by default. */
  return ADDR_POLICY_ACCEPTED;
}

/** Helper for compare_tor_addr_to_addr_policy.  Implements the case where
 * addr is known but port is not. */
static addr_policy_result_t
compare_known_tor_addr_to_addr_policy_noport(const tor_addr_t *addr,
                                             const smartlist_t *policy)
{
  /* We look to see if there's a definite match.  If so, we return that
     match's value, unless there's an intervening possible match that says
     something different. */
  int maybe_accept = 0, maybe_reject = 0;

  SMARTLIST_FOREACH_BEGIN(policy, addr_policy_t *, tmpe) {
    if (tmpe->addr.family == AF_UNSPEC) {
      log_warn(LD_BUG, "Policy contains an AF_UNSPEC address, which only "
               "matches other AF_UNSPEC addresses.");
    }
    if (!tor_addr_compare_masked(addr, &tmpe->addr, tmpe->maskbits,
                                 CMP_EXACT)) {
      if (tmpe->prt_min <= 1 && tmpe->prt_max >= 65535) {
        /* Definitely matches, since it covers all ports. */
        if (tmpe->policy_type == ADDR_POLICY_ACCEPT) {
          /* If we already hit a clause that might trigger a 'reject', than we
           * can't be sure of this certain 'accept'.*/
          return maybe_reject ? ADDR_POLICY_PROBABLY_ACCEPTED :
            ADDR_POLICY_ACCEPTED;
        } else {
          return maybe_accept ? ADDR_POLICY_PROBABLY_REJECTED :
            ADDR_POLICY_REJECTED;
        }
      } else {
        /* Might match. */
        if (tmpe->policy_type == ADDR_POLICY_REJECT)
          maybe_reject = 1;
        else
          maybe_accept = 1;
      }
    }
  } SMARTLIST_FOREACH_END(tmpe);

  /* accept all by default. */
  return maybe_reject ? ADDR_POLICY_PROBABLY_ACCEPTED : ADDR_POLICY_ACCEPTED;
}

/** Helper for compare_tor_addr_to_addr_policy.  Implements the case where
 * port is known but address is not. */
static addr_policy_result_t
compare_unknown_tor_addr_to_addr_policy(uint16_t port,
                                        const smartlist_t *policy)
{
  /* We look to see if there's a definite match.  If so, we return that
     match's value, unless there's an intervening possible match that says
     something different. */
  int maybe_accept = 0, maybe_reject = 0;

  SMARTLIST_FOREACH_BEGIN(policy, addr_policy_t *, tmpe) {
    if (tmpe->addr.family == AF_UNSPEC) {
      log_warn(LD_BUG, "Policy contains an AF_UNSPEC address, which only "
               "matches other AF_UNSPEC addresses.");
    }
    if (tmpe->prt_min <= port && port <= tmpe->prt_max) {
      if (tmpe->maskbits == 0) {
        /* Definitely matches, since it covers all addresses. */
        if (tmpe->policy_type == ADDR_POLICY_ACCEPT) {
          /* If we already hit a clause that might trigger a 'reject', than we
           * can't be sure of this certain 'accept'.*/
          return maybe_reject ? ADDR_POLICY_PROBABLY_ACCEPTED :
            ADDR_POLICY_ACCEPTED;
        } else {
          return maybe_accept ? ADDR_POLICY_PROBABLY_REJECTED :
            ADDR_POLICY_REJECTED;
        }
      } else {
        /* Might match. */
        if (tmpe->policy_type == ADDR_POLICY_REJECT)
          maybe_reject = 1;
        else
          maybe_accept = 1;
      }
    }
  } SMARTLIST_FOREACH_END(tmpe);

  /* accept all by default. */
  return maybe_reject ? ADDR_POLICY_PROBABLY_ACCEPTED : ADDR_POLICY_ACCEPTED;
}

/** Decide whether a given addr:port is definitely accepted,
 * definitely rejected, probably accepted, or probably rejected by a
 * given policy.  If <b>addr</b> is 0, we don't know the IP of the
 * target address.  If <b>port</b> is 0, we don't know the port of the
 * target address.  (At least one of <b>addr</b> and <b>port</b> must be
 * provided.  If you want to know whether a policy would definitely reject
 * an unknown address:port, use policy_is_reject_star().)
 *
 * We could do better by assuming that some ranges never match typical
 * addresses (127.0.0.1, and so on).  But we'll try this for now.
 */
MOCK_IMPL(addr_policy_result_t,
compare_tor_addr_to_addr_policy,(const tor_addr_t *addr, uint16_t port,
                                 const smartlist_t *policy))
{
  if (!policy) {
    /* no policy? accept all. */
    return ADDR_POLICY_ACCEPTED;
  } else if (addr == NULL || tor_addr_is_null(addr)) {
    if (port == 0) {
      log_info(LD_BUG, "Rejecting null address with 0 port (family %d)",
               addr ? tor_addr_family(addr) : -1);
      return ADDR_POLICY_REJECTED;
    }
    return compare_unknown_tor_addr_to_addr_policy(port, policy);
  } else if (port == 0) {
    return compare_known_tor_addr_to_addr_policy_noport(addr, policy);
  } else {
    return compare_known_tor_addr_to_addr_policy(addr, port, policy);
  }
}

/** Return true iff the address policy <b>a</b> covers every case that
 * would be covered by <b>b</b>, so that a,b is redundant. */
static int
addr_policy_covers(addr_policy_t *a, addr_policy_t *b)
{
  if (tor_addr_family(&a->addr) != tor_addr_family(&b->addr)) {
    /* You can't cover a different family. */
    return 0;
  }
  /* We can ignore accept/reject, since "accept *:80, reject *:80" reduces
   * to "accept *:80". */
  if (a->maskbits > b->maskbits) {
    /* a has more fixed bits than b; it can't possibly cover b. */
    return 0;
  }
  if (tor_addr_compare_masked(&a->addr, &b->addr, a->maskbits, CMP_EXACT)) {
    /* There's a fixed bit in a that's set differently in b. */
    return 0;
  }
  return (a->prt_min <= b->prt_min && a->prt_max >= b->prt_max);
}

/** Return true iff the address policies <b>a</b> and <b>b</b> intersect,
 * that is, there exists an address/port that is covered by <b>a</b> that
 * is also covered by <b>b</b>.
 */
static int
addr_policy_intersects(addr_policy_t *a, addr_policy_t *b)
{
  maskbits_t minbits;
  /* All the bits we care about are those that are set in both
   * netmasks.  If they are equal in a and b's networkaddresses
   * then the networks intersect.  If there is a difference,
   * then they do not. */
  if (a->maskbits < b->maskbits)
    minbits = a->maskbits;
  else
    minbits = b->maskbits;
  if (tor_addr_compare_masked(&a->addr, &b->addr, minbits, CMP_EXACT))
    return 0;
  if (a->prt_max < b->prt_min || b->prt_max < a->prt_min)
    return 0;
  return 1;
}

/** Add the exit policy described by <b>more</b> to <b>policy</b>.
 */
STATIC void
append_exit_policy_string(smartlist_t **policy, const char *more)
{
  config_line_t tmp;

  tmp.key = NULL;
  tmp.value = (char*) more;
  tmp.next = NULL;
  if (parse_addr_policy(&tmp, policy, -1)<0) {
    log_warn(LD_BUG, "Unable to parse internally generated policy %s",more);
  }
}

/** Add "reject <b>addr</b>:*" to <b>dest</b>, creating the list as needed. */
void
addr_policy_append_reject_addr(smartlist_t **dest, const tor_addr_t *addr)
{
  tor_assert(dest);
  tor_assert(addr);

  addr_policy_t p, *add;
  memset(&p, 0, sizeof(p));
  p.policy_type = ADDR_POLICY_REJECT;
  p.maskbits = tor_addr_family(addr) == AF_INET6 ? 128 : 32;
  tor_addr_copy(&p.addr, addr);
  p.prt_min = 1;
  p.prt_max = 65535;

  add = addr_policy_get_canonical_entry(&p);
  if (!*dest)
    *dest = smartlist_new();
  smartlist_add(*dest, add);
  log_debug(LD_CONFIG, "Adding a reject ExitPolicy 'reject %s:*'",
            fmt_addr(addr));
}

/* Is addr public for the purposes of rejection? */
static int
tor_addr_is_public_for_reject(const tor_addr_t *addr)
{
  return (!tor_addr_is_null(addr) && !tor_addr_is_internal(addr, 0)
          && !tor_addr_is_multicast(addr));
}

/* Add "reject <b>addr</b>:*" to <b>dest</b>, creating the list as needed.
 * Filter the address, only adding an IPv4 reject rule if ipv4_rules
 * is true, and similarly for ipv6_rules. Check each address returns true for
 * tor_addr_is_public_for_reject before adding it.
 */
static void
addr_policy_append_reject_addr_filter(smartlist_t **dest,
                                      const tor_addr_t *addr,
                                      int ipv4_rules,
                                      int ipv6_rules)
{
  tor_assert(dest);
  tor_assert(addr);

  /* Only reject IP addresses which are public */
  if (tor_addr_is_public_for_reject(addr)) {

    /* Reject IPv4 addresses and IPv6 addresses based on the filters */
    int is_ipv4 = tor_addr_is_v4(addr);
    if ((is_ipv4 && ipv4_rules) || (!is_ipv4 && ipv6_rules)) {
      addr_policy_append_reject_addr(dest, addr);
    }
  }
}

/** Add "reject addr:*" to <b>dest</b>, for each addr in addrs, creating the
  * list as needed. */
void
addr_policy_append_reject_addr_list(smartlist_t **dest,
                                    const smartlist_t *addrs)
{
  tor_assert(dest);
  tor_assert(addrs);

  SMARTLIST_FOREACH_BEGIN(addrs, tor_addr_t *, addr) {
    addr_policy_append_reject_addr(dest, addr);
  } SMARTLIST_FOREACH_END(addr);
}

/** Add "reject addr:*" to <b>dest</b>, for each addr in addrs, creating the
 * list as needed. Filter using */
static void
addr_policy_append_reject_addr_list_filter(smartlist_t **dest,
                                           const smartlist_t *addrs,
                                           int ipv4_rules,
                                           int ipv6_rules)
{
  tor_assert(dest);
  tor_assert(addrs);

  SMARTLIST_FOREACH_BEGIN(addrs, tor_addr_t *, addr) {
    addr_policy_append_reject_addr_filter(dest, addr, ipv4_rules, ipv6_rules);
  } SMARTLIST_FOREACH_END(addr);
}

/** Detect and excise "dead code" from the policy *<b>dest</b>. */
static void
exit_policy_remove_redundancies(smartlist_t *dest)
{
  addr_policy_t *ap, *tmp;
  int i, j;

  /* Step one: kill every ipv4 thing after *4:*, every IPv6 thing after *6:*
   */
  {
    int kill_v4=0, kill_v6=0;
    for (i = 0; i < smartlist_len(dest); ++i) {
      sa_family_t family;
      ap = smartlist_get(dest, i);
      family = tor_addr_family(&ap->addr);
      if ((family == AF_INET && kill_v4) ||
          (family == AF_INET6 && kill_v6)) {
        smartlist_del_keeporder(dest, i--);
        addr_policy_free(ap);
        continue;
      }

      if (ap->maskbits == 0 && ap->prt_min <= 1 && ap->prt_max >= 65535) {
        /* This is a catch-all line -- later lines are unreachable. */
        if (family == AF_INET) {
          kill_v4 = 1;
        } else if (family == AF_INET6) {
          kill_v6 = 1;
        }
      }
    }
  }

  /* Step two: for every entry, see if there's a redundant entry
   * later on, and remove it. */
  for (i = 0; i < smartlist_len(dest)-1; ++i) {
    ap = smartlist_get(dest, i);
    for (j = i+1; j < smartlist_len(dest); ++j) {
      tmp = smartlist_get(dest, j);
      tor_assert(j > i);
      if (addr_policy_covers(ap, tmp)) {
        char p1[POLICY_BUF_LEN], p2[POLICY_BUF_LEN];
        policy_write_item(p1, sizeof(p1), tmp, 0);
        policy_write_item(p2, sizeof(p2), ap, 0);
        log_debug(LD_CONFIG, "Removing exit policy %s (%d).  It is made "
            "redundant by %s (%d).", p1, j, p2, i);
        smartlist_del_keeporder(dest, j--);
        addr_policy_free(tmp);
      }
    }
  }

  /* Step three: for every entry A, see if there's an entry B making this one
   * redundant later on.  This is the case if A and B are of the same type
   * (accept/reject), A is a subset of B, and there is no other entry of
   * different type in between those two that intersects with A.
   *
   * Anybody want to double-check the logic here? XXX
   */
  for (i = 0; i < smartlist_len(dest)-1; ++i) {
    ap = smartlist_get(dest, i);
    for (j = i+1; j < smartlist_len(dest); ++j) {
      // tor_assert(j > i); // j starts out at i+1; j only increases; i only
      //                    // decreases.
      tmp = smartlist_get(dest, j);
      if (ap->policy_type != tmp->policy_type) {
        if (addr_policy_intersects(ap, tmp))
          break;
      } else { /* policy_types are equal. */
        if (addr_policy_covers(tmp, ap)) {
          char p1[POLICY_BUF_LEN], p2[POLICY_BUF_LEN];
          policy_write_item(p1, sizeof(p1), ap, 0);
          policy_write_item(p2, sizeof(p2), tmp, 0);
          log_debug(LD_CONFIG, "Removing exit policy %s.  It is already "
              "covered by %s.", p1, p2);
          smartlist_del_keeporder(dest, i--);
          addr_policy_free(ap);
          break;
        }
      }
    }
  }
}

/** Reject private helper for policies_parse_exit_policy_internal: rejects
 * publicly routable addresses on this exit relay.
 *
 * Add reject entries to the linked list *<b>dest</b>:
 * <ul>
 * <li>if configured_addresses is non-NULL, add entries that reject each
 *     tor_addr_t in the list as a destination.
 * <li>if reject_interface_addresses is true, add entries that reject each
 *     public IPv4 and IPv6 address of each interface on this machine.
 * <li>if reject_configured_port_addresses is true, add entries that reject
 *     each IPv4 and IPv6 address configured for a port.
 * </ul>
 *
 * IPv6 entries are only added if ipv6_exit is true. (All IPv6 addresses are
 * already blocked by policies_parse_exit_policy_internal if ipv6_exit is
 * false.)
 *
 * The list in <b>dest</b> is created as needed.
 */
void
policies_parse_exit_policy_reject_private(
                                      smartlist_t **dest,
                                      int ipv6_exit,
                                      const smartlist_t *configured_addresses,
                                      int reject_interface_addresses,
                                      int reject_configured_port_addresses)
{
  tor_assert(dest);

  /* Reject configured addresses, if they are from public netblocks. */
  if (configured_addresses) {
    addr_policy_append_reject_addr_list_filter(dest, configured_addresses,
                                               1, ipv6_exit);
  }

  /* Reject configured port addresses, if they are from public netblocks. */
  if (reject_configured_port_addresses) {
    const smartlist_t *port_addrs = get_configured_ports();

    SMARTLIST_FOREACH_BEGIN(port_addrs, port_cfg_t *, port) {

      /* Only reject port IP addresses, not port unix sockets */
      if (!port->is_unix_addr) {
        addr_policy_append_reject_addr_filter(dest, &port->addr, 1, ipv6_exit);
      }
    } SMARTLIST_FOREACH_END(port);
  }

  /* Reject local addresses from public netblocks on any interface. */
  if (reject_interface_addresses) {
    smartlist_t *public_addresses = NULL;

    /* Reject public IPv4 addresses on any interface */
    public_addresses = get_interface_address6_list(LOG_INFO, AF_INET, 0);
    addr_policy_append_reject_addr_list_filter(dest, public_addresses, 1, 0);
    interface_address6_list_free(public_addresses);

    /* Don't look for IPv6 addresses if we're configured as IPv4-only */
    if (ipv6_exit) {
      /* Reject public IPv6 addresses on any interface */
      public_addresses = get_interface_address6_list(LOG_INFO, AF_INET6, 0);
      addr_policy_append_reject_addr_list_filter(dest, public_addresses, 0, 1);
      interface_address6_list_free(public_addresses);
    }
  }

  /* If addresses were added multiple times, remove all but one of them. */
  if (*dest) {
    exit_policy_remove_redundancies(*dest);
  }
}

/**
 * Iterate through <b>policy</b> looking for redundant entries. Log a
 * warning message with the first redundant entry, if any is found.
 */
static void
policies_log_first_redundant_entry(const smartlist_t *policy)
{
  int found_final_effective_entry = 0;
  int first_redundant_entry = 0;
  tor_assert(policy);
  SMARTLIST_FOREACH_BEGIN(policy, const addr_policy_t *, p) {
    sa_family_t family;
    int found_ipv4_wildcard = 0, found_ipv6_wildcard = 0;
    const int i = p_sl_idx;

    /* Look for accept/reject *[4|6|]:* entries */
    if (p->prt_min <= 1 && p->prt_max == 65535 && p->maskbits == 0) {
      family = tor_addr_family(&p->addr);
      /* accept/reject *:* may have already been expanded into
       * accept/reject *4:*,accept/reject *6:*
       * But handle both forms.
       */
      if (family == AF_INET || family == AF_UNSPEC) {
        found_ipv4_wildcard = 1;
      }
      if (family == AF_INET6 || family == AF_UNSPEC) {
        found_ipv6_wildcard = 1;
      }
    }

    /* We also find accept *4:*,reject *6:* ; and
     * accept *4:*,<other policies>,accept *6:* ; and similar.
     * That's ok, because they make any subsequent entries redundant. */
    if (found_ipv4_wildcard && found_ipv6_wildcard) {
      found_final_effective_entry = 1;
      /* if we're not on the final entry in the list */
      if (i < smartlist_len(policy) - 1) {
        first_redundant_entry = i + 1;
      }
      break;
    }
  } SMARTLIST_FOREACH_END(p);

  /* Work out if there are redundant trailing entries in the policy list */
  if (found_final_effective_entry && first_redundant_entry > 0) {
    const addr_policy_t *p;
    /* Longest possible policy is
     * "accept6 ffff:ffff:..255/128:10000-65535",
     * which contains a max-length IPv6 address, plus 24 characters. */
    char line[TOR_ADDR_BUF_LEN + 32];

    tor_assert(first_redundant_entry < smartlist_len(policy));
    p = smartlist_get(policy, first_redundant_entry);
    /* since we've already parsed the policy into an addr_policy_t struct,
     * we might not log exactly what the user typed in */
    policy_write_item(line, TOR_ADDR_BUF_LEN + 32, p, 0);
    log_warn(LD_DIR, "Exit policy '%s' and all following policies are "
             "redundant, as it follows accept/reject *:* rules for both "
             "IPv4 and IPv6. They will be removed from the exit policy. (Use "
             "accept/reject *:* as the last entry in any exit policy.)",
             line);
  }
}

#define DEFAULT_EXIT_POLICY                                         \
  "reject *:25,reject *:119,reject *:135-139,reject *:445,"         \
  "reject *:563,reject *:1214,reject *:4661-4666,"                  \
  "reject *:6346-6429,reject *:6699,reject *:6881-6999,accept *:*"

#define REDUCED_EXIT_POLICY                                                   \
  "accept *:20-23,accept *:43,accept *:53,accept *:79-81,accept *:88,"        \
  "accept *:110,accept *:143,accept *:194,accept *:220,accept *:389,"         \
  "accept *:443,accept *:464,accept *:465,accept *:531,accept *:543-544,"     \
  "accept *:554,accept *:563,accept *:587,accept *:636,accept *:706,"         \
  "accept *:749,accept *:873,accept *:902-904,accept *:981,accept *:989-995," \
  "accept *:1194,accept *:1220,accept *:1293,accept *:1500,accept *:1533,"    \
  "accept *:1677,accept *:1723,accept *:1755,accept *:1863,"                  \
  "accept *:2082-2083,accept *:2086-2087,accept *:2095-2096,"                 \
  "accept *:2102-2104,accept *:3128,accept *:3389,accept *:3690,"             \
  "accept *:4321,accept *:4643,accept *:5050,accept *:5190,"                  \
  "accept *:5222-5223,accept *:5228,accept *:5900,accept *:6660-6669,"        \
  "accept *:6679,accept *:6697,accept *:8000,accept *:8008,accept *:8074,"    \
  "accept *:8080,accept *:8082,accept *:8087-8088,accept *:8232-8233,"        \
  "accept *:8332-8333,accept *:8443,accept *:8888,accept *:9418,"             \
  "accept *:9999,accept *:10000,accept *:11371,accept *:19294,"               \
  "accept *:19638,accept *:50002,accept *:64738,reject *:*"

/** Parse the exit policy <b>cfg</b> into the linked list *<b>dest</b>.
 *
 * If <b>ipv6_exit</b> is false, prepend "reject *6:*" to the policy.
 *
 * If <b>configured_addresses</b> contains addresses:
 *   - prepend entries that reject the addresses in this list. These may be the
 *     advertised relay addresses and/or the outbound bind addresses,
 *     depending on the ExitPolicyRejectPrivate and
 *     ExitPolicyRejectLocalInterfaces settings.
 * If <b>rejectprivate</b> is true:
 *   - prepend "reject private:*" to the policy.
 * If <b>reject_interface_addresses</b> is true:
 *   - prepend entries that reject publicly routable interface addresses on
 *     this exit relay by calling policies_parse_exit_policy_reject_private
 * If <b>reject_configured_port_addresses</b> is true:
 *   - prepend entries that reject all configured port addresses
 *
 * If cfg doesn't end in an absolute accept or reject and if
 * <b>add_default_policy</b> is true, add the default exit
 * policy afterwards.
 *
 * Return -1 if we can't parse cfg, else return 0.
 *
 * This function is used to parse the exit policy from our torrc. For
 * the functions used to parse the exit policy from a router descriptor,
 * see router_add_exit_policy.
 */
static int
policies_parse_exit_policy_internal(config_line_t *cfg,
                                    smartlist_t **dest,
                                    int ipv6_exit,
                                    int rejectprivate,
                                    const smartlist_t *configured_addresses,
                                    int reject_interface_addresses,
                                    int reject_configured_port_addresses,
                                    int add_default_policy,
                                    int add_reduced_policy)
{
  if (!ipv6_exit) {
    append_exit_policy_string(dest, "reject *6:*");
  }
  if (rejectprivate) {
    /* Reject IPv4 and IPv6 reserved private netblocks */
    append_exit_policy_string(dest, "reject private:*");
  }

  /* Consider rejecting IPv4 and IPv6 advertised relay addresses, outbound bind
   * addresses, publicly routable addresses, and configured port addresses
   * on this exit relay */
  policies_parse_exit_policy_reject_private(dest, ipv6_exit,
                                            configured_addresses,
                                            reject_interface_addresses,
                                            reject_configured_port_addresses);

  if (parse_addr_policy(cfg, dest, -1))
    return -1;

  /* Before we add the default policy and final rejects, check to see if
   * there are any lines after accept *:* or reject *:*. These lines have no
   * effect, and are most likely an error. */
  policies_log_first_redundant_entry(*dest);

  if (add_reduced_policy) {
    append_exit_policy_string(dest, REDUCED_EXIT_POLICY);
  } else if (add_default_policy) {
    append_exit_policy_string(dest, DEFAULT_EXIT_POLICY);
  } else {
    append_exit_policy_string(dest, "reject *4:*");
    append_exit_policy_string(dest, "reject *6:*");
  }
  exit_policy_remove_redundancies(*dest);

  return 0;
}

/** Parse exit policy in <b>cfg</b> into <b>dest</b> smartlist.
 *
 * Prepend an entry that rejects all IPv6 destinations unless
 * <b>EXIT_POLICY_IPV6_ENABLED</b> bit is set in <b>options</b> bitmask.
 *
 * If <b>EXIT_POLICY_REJECT_PRIVATE</b> bit is set in <b>options</b>:
 *   - prepend an entry that rejects all destinations in all netblocks
 *     reserved for private use.
 *   - prepend entries that reject the advertised relay addresses in
 *     configured_addresses
 * If <b>EXIT_POLICY_REJECT_LOCAL_INTERFACES</b> bit is set in <b>options</b>:
 *   - prepend entries that reject publicly routable addresses on this exit
 *     relay by calling policies_parse_exit_policy_internal
 *   - prepend entries that reject the outbound bind addresses in
 *     configured_addresses
 *   - prepend entries that reject all configured port addresses
 *
 * If <b>EXIT_POLICY_ADD_DEFAULT</b> bit is set in <b>options</b>, append
 * default exit policy entries to <b>result</b> smartlist.
 */
int
policies_parse_exit_policy(config_line_t *cfg, smartlist_t **dest,
                           exit_policy_parser_cfg_t options,
                           const smartlist_t *configured_addresses)
{
  int ipv6_enabled = (options & EXIT_POLICY_IPV6_ENABLED) ? 1 : 0;
  int reject_private = (options & EXIT_POLICY_REJECT_PRIVATE) ? 1 : 0;
  int add_default = (options & EXIT_POLICY_ADD_DEFAULT) ? 1 : 0;
  int reject_local_interfaces = (options &
                                 EXIT_POLICY_REJECT_LOCAL_INTERFACES) ? 1 : 0;
  int add_reduced = (options & EXIT_POLICY_ADD_REDUCED) ? 1 : 0;

  return policies_parse_exit_policy_internal(cfg,dest,ipv6_enabled,
                                             reject_private,
                                             configured_addresses,
                                             reject_local_interfaces,
                                             reject_local_interfaces,
                                             add_default,
                                             add_reduced);
}

/** Helper function that adds a copy of addr to a smartlist as long as it is
 * non-NULL and not tor_addr_is_null().
 *
 * The caller is responsible for freeing all the tor_addr_t* in the smartlist.
 */
static void
policies_copy_addr_to_smartlist(smartlist_t *addr_list, const tor_addr_t *addr)
{
  if (addr && !tor_addr_is_null(addr)) {
    tor_addr_t *addr_copy = tor_malloc(sizeof(tor_addr_t));
    tor_addr_copy(addr_copy, addr);
    smartlist_add(addr_list, addr_copy);
  }
}

/** Helper function that adds copies of or_options->OutboundBindAddresses
 * to a smartlist as tor_addr_t *, as long as or_options is non-NULL, and
 * the addresses are not tor_addr_is_null(), by passing them to
 * policies_add_addr_to_smartlist.
 *
 * The caller is responsible for freeing all the tor_addr_t* in the smartlist.
 */
static void
policies_copy_outbound_addresses_to_smartlist(smartlist_t *addr_list,
                                              const or_options_t *or_options)
{
  if (or_options) {
    for (int i=0;i<OUTBOUND_ADDR_MAX;i++) {
      for (int j=0;j<2;j++) {
        if (!tor_addr_is_null(&or_options->OutboundBindAddresses[i][j])) {
          policies_copy_addr_to_smartlist(addr_list,
                          &or_options->OutboundBindAddresses[i][j]);
        }
      }
    }
  }
}

/** Parse <b>ExitPolicy</b> member of <b>or_options</b> into <b>result</b>
 * smartlist.
 * If <b>or_options->IPv6Exit</b> is false, prepend an entry that
 * rejects all IPv6 destinations.
 *
 * If <b>or_options->ExitPolicyRejectPrivate</b> is true:
 *  - prepend an entry that rejects all destinations in all netblocks reserved
 *    for private use.
 *  - if ipv4_local_address is non-zero, treat it as a host-order IPv4 address,
 *    and add it to the list of configured addresses.
 *  - if ipv6_local_address is non-NULL, and not the null tor_addr_t, add it
 *    to the list of configured addresses.
 * If <b>or_options->ExitPolicyRejectLocalInterfaces</b> is true:
 *  - if or_options->OutboundBindAddresses[][0] (=IPv4) is not the null
 *    tor_addr_t, add it to the list of configured addresses.
 *  - if or_options->OutboundBindAddresses[][1] (=IPv6) is not the null
 *    tor_addr_t, add it to the list of configured addresses.
 *
 * If <b>or_options->BridgeRelay</b> is false, append entries of default
 * Tor exit policy into <b>result</b> smartlist.
 *
 * If or_options->ExitRelay is false, or is auto without specifying an exit
 * policy, then make our exit policy into "reject *:*" regardless.
 */
int
policies_parse_exit_policy_from_options(const or_options_t *or_options,
                                        const tor_addr_t *ipv4_local_address,
                                        const tor_addr_t *ipv6_local_address,
                                        smartlist_t **result)
{
  exit_policy_parser_cfg_t parser_cfg = 0;
  smartlist_t *configured_addresses = NULL;
  int rv = 0;

  /* Short-circuit for non-exit relays, or for relays where we didn't specify
   * ExitPolicy or ReducedExitPolicy or IPv6Exit and ExitRelay is auto. */
  if (or_options->ExitRelay == 0 ||
      policy_using_default_exit_options(or_options)) {
    append_exit_policy_string(result, "reject *4:*");
    append_exit_policy_string(result, "reject *6:*");
    return 0;
  }

  configured_addresses = smartlist_new();

  /* Configure the parser */
  if (or_options->IPv6Exit) {
    parser_cfg |= EXIT_POLICY_IPV6_ENABLED;
  }

  if (or_options->ExitPolicyRejectPrivate) {
    parser_cfg |= EXIT_POLICY_REJECT_PRIVATE;
  }

  if (!or_options->BridgeRelay) {
    if (or_options->ReducedExitPolicy)
      parser_cfg |= EXIT_POLICY_ADD_REDUCED;
    else
      parser_cfg |= EXIT_POLICY_ADD_DEFAULT;
  }

  if (or_options->ExitPolicyRejectLocalInterfaces) {
    parser_cfg |= EXIT_POLICY_REJECT_LOCAL_INTERFACES;
  }

  /* Copy the configured addresses into the tor_addr_t* list */
  if (or_options->ExitPolicyRejectPrivate) {
    policies_copy_addr_to_smartlist(configured_addresses, ipv4_local_address);
    policies_copy_addr_to_smartlist(configured_addresses, ipv6_local_address);
  }

  if (or_options->ExitPolicyRejectLocalInterfaces) {
    policies_copy_outbound_addresses_to_smartlist(configured_addresses,
                                                  or_options);
  }

  rv = policies_parse_exit_policy(or_options->ExitPolicy, result, parser_cfg,
                                  configured_addresses);

  SMARTLIST_FOREACH(configured_addresses, tor_addr_t *, a, tor_free(a));
  smartlist_free(configured_addresses);

  return rv;
}

/** Add "reject *:*" to the end of the policy in *<b>dest</b>, allocating
 * *<b>dest</b> as needed. */
void
policies_exit_policy_append_reject_star(smartlist_t **dest)
{
  append_exit_policy_string(dest, "reject *4:*");
  append_exit_policy_string(dest, "reject *6:*");
}

/** Replace the exit policy of <b>node</b> with reject *:* */
void
policies_set_node_exitpolicy_to_reject_all(node_t *node)
{
  node->rejects_all = 1;
}

/** Return 1 if there is at least one /8 subnet in <b>policy</b> that
 * allows exiting to <b>port</b>.  Otherwise, return 0. */
static int
exit_policy_is_general_exit_helper(smartlist_t *policy, int port)
{
  uint32_t mask, ip, i;
  /* Is this /8 rejected (1), or undecided (0)? */
  char subnet_status[256];

  memset(subnet_status, 0, sizeof(subnet_status));
  SMARTLIST_FOREACH_BEGIN(policy, addr_policy_t *, p) {
    if (tor_addr_family(&p->addr) != AF_INET)
      continue; /* IPv4 only for now */
    if (p->prt_min > port || p->prt_max < port)
      continue; /* Doesn't cover our port. */
    mask = 0;
    tor_assert(p->maskbits <= 32);

    if (p->maskbits)
      mask = UINT32_MAX<<(32-p->maskbits);
    ip = tor_addr_to_ipv4h(&p->addr);

    /* Calculate the first and last subnet that this exit policy touches
     * and set it as loop boundaries. */
    for (i = ((mask & ip)>>24); i <= (~((mask & ip) ^ mask)>>24); ++i) {
      tor_addr_t addr;
      if (subnet_status[i] != 0)
        continue; /* We already reject some part of this /8 */
      tor_addr_from_ipv4h(&addr, i<<24);
      if (tor_addr_is_internal(&addr, 0) &&
          !get_options()->DirAllowPrivateAddresses) {
        continue; /* Local or non-routable addresses */
      }
      if (p->policy_type == ADDR_POLICY_ACCEPT) {
        if (p->maskbits > 8)
          continue; /* Narrower than a /8. */
        /* We found an allowed subnet of at least size /8. Done
         * for this port! */
        return 1;
      } else if (p->policy_type == ADDR_POLICY_REJECT) {
        subnet_status[i] = 1;
      }
    }
  } SMARTLIST_FOREACH_END(p);
  return 0;
}

/** Return true iff <b>ri</b> is "useful as an exit node", meaning
 * it allows exit to at least one /8 address space for each of ports 80
 * and 443. */
int
exit_policy_is_general_exit(smartlist_t *policy)
{
  if (!policy) /*XXXX disallow NULL policies? */
    return 0;

  return (exit_policy_is_general_exit_helper(policy, 80) &&
          exit_policy_is_general_exit_helper(policy, 443));
}

/** Return false if <b>policy</b> might permit access to some addr:port;
 * otherwise if we are certain it rejects everything, return true. If no
 * part of <b>policy</b> matches, return <b>default_reject</b>.
 * NULL policies are allowed, and treated as empty. */
int
policy_is_reject_star(const smartlist_t *policy, sa_family_t family,
                      int default_reject)
{
  if (!policy)
    return default_reject;
  SMARTLIST_FOREACH_BEGIN(policy, const addr_policy_t *, p) {
    if (p->policy_type == ADDR_POLICY_ACCEPT &&
        (tor_addr_family(&p->addr) == family ||
         tor_addr_family(&p->addr) == AF_UNSPEC)) {
      return 0;
    } else if (p->policy_type == ADDR_POLICY_REJECT &&
               p->prt_min <= 1 && p->prt_max == 65535 &&
               p->maskbits == 0 &&
               (tor_addr_family(&p->addr) == family ||
                tor_addr_family(&p->addr) == AF_UNSPEC)) {
      return 1;
    }
  } SMARTLIST_FOREACH_END(p);
  return default_reject;
}

/** Write a single address policy to the buf_len byte buffer at buf.  Return
 * the number of characters written, or -1 on failure. */
int
policy_write_item(char *buf, size_t buflen, const addr_policy_t *policy,
                  int format_for_desc)
{
  size_t written = 0;
  char addrbuf[TOR_ADDR_BUF_LEN];
  const char *addrpart;
  int result;
  const int is_accept = policy->policy_type == ADDR_POLICY_ACCEPT;
  const sa_family_t family = tor_addr_family(&policy->addr);
  const int is_ip6 = (family == AF_INET6);

  tor_addr_to_str(addrbuf, &policy->addr, sizeof(addrbuf), 1);

  /* write accept/reject 1.2.3.4 */
  if (policy->is_private) {
    addrpart = "private";
  } else if (policy->maskbits == 0) {
    if (format_for_desc)
      addrpart = "*";
    else if (family == AF_INET6)
      addrpart = "*6";
    else if (family == AF_INET)
      addrpart = "*4";
    else
      addrpart = "*";
  } else {
    addrpart = addrbuf;
  }

  result = tor_snprintf(buf, buflen, "%s%s %s",
                        is_accept ? "accept" : "reject",
                        (is_ip6&&format_for_desc)?"6":"",
                        addrpart);
  if (result < 0)
    return -1;
  written += strlen(buf);
  /* If the maskbits is 32 (IPv4) or 128 (IPv6) we don't need to give it.  If
     the mask is 0, we already wrote "*". */
  if (policy->maskbits < (is_ip6?128:32) && policy->maskbits > 0) {
    if (tor_snprintf(buf+written, buflen-written, "/%d", policy->maskbits)<0)
      return -1;
    written += strlen(buf+written);
  }
  if (policy->prt_min <= 1 && policy->prt_max == 65535) {
    /* There is no port set; write ":*" */
    if (written+4 > buflen)
      return -1;
    strlcat(buf+written, ":*", buflen-written);
    written += 2;
  } else if (policy->prt_min == policy->prt_max) {
    /* There is only one port; write ":80". */
    result = tor_snprintf(buf+written, buflen-written, ":%d", policy->prt_min);
    if (result<0)
      return -1;
    written += result;
  } else {
    /* There is a range of ports; write ":79-80". */
    result = tor_snprintf(buf+written, buflen-written, ":%d-%d",
                          policy->prt_min, policy->prt_max);
    if (result<0)
      return -1;
    written += result;
  }
  if (written < buflen)
    buf[written] = '\0';
  else
    return -1;

  return (int)written;
}

/** Create a new exit policy summary, initially only with a single
 *  port 1-64k item */
/* XXXX This entire thing will do most stuff in O(N^2), or worse.  Use an
 *      RB-tree if that turns out to matter. */
static smartlist_t *
policy_summary_create(void)
{
  smartlist_t *summary;
  policy_summary_item_t* item;

  item = tor_malloc_zero(sizeof(policy_summary_item_t));
  item->prt_min = 1;
  item->prt_max = 65535;
  item->reject_count = 0;
  item->accepted = 0;

  summary = smartlist_new();
  smartlist_add(summary, item);

  return summary;
}

/** Split the summary item in <b>item</b> at the port <b>new_starts</b>.
 * The current item is changed to end at new-starts - 1, the new item
 * copies reject_count and accepted from the old item,
 * starts at new_starts and ends at the port where the original item
 * previously ended.
 */
static policy_summary_item_t*
policy_summary_item_split(policy_summary_item_t* old, uint16_t new_starts)
{
  policy_summary_item_t* new;

  new = tor_malloc_zero(sizeof(policy_summary_item_t));
  new->prt_min = new_starts;
  new->prt_max = old->prt_max;
  new->reject_count = old->reject_count;
  new->accepted = old->accepted;

  old->prt_max = new_starts-1;

  tor_assert(old->prt_min <= old->prt_max);
  tor_assert(new->prt_min <= new->prt_max);
  return new;
}

/* XXXX Nick says I'm going to hell for this.  If he feels charitably towards
 * my immortal soul, he can clean it up himself. */
#define AT(x) ((policy_summary_item_t*)smartlist_get(summary, x))

#define IPV4_BITS                (32)
/* Every IPv4 address is counted as one rejection */
#define REJECT_CUTOFF_SCALE_IPV4 (0)
/* Ports are rejected in an IPv4 summary if they are rejected in more than two
 * IPv4 /8 address blocks */
#define REJECT_CUTOFF_COUNT_IPV4 (UINT64_C(1) << \
                                  (IPV4_BITS - REJECT_CUTOFF_SCALE_IPV4 - 7))

#define IPV6_BITS                (128)
/* IPv6 /64s are counted as one rejection, anything smaller is ignored */
#define REJECT_CUTOFF_SCALE_IPV6 (64)
/* Ports are rejected in an IPv6 summary if they are rejected in more than one
 * IPv6 /16 address block.
 * This is roughly equivalent to the IPv4 cutoff, as only five IPv6 /12s (and
 * some scattered smaller blocks) have been allocated to the RIRs.
 * Network providers are typically allocated one or more IPv6 /32s.
 */
#define REJECT_CUTOFF_COUNT_IPV6 (UINT64_C(1) << \
                                  (IPV6_BITS - REJECT_CUTOFF_SCALE_IPV6 - 16))

/** Split an exit policy summary so that prt_min and prt_max
 * fall at exactly the start and end of an item respectively.
 */
static int
policy_summary_split(smartlist_t *summary,
                     uint16_t prt_min, uint16_t prt_max)
{
  int start_at_index;

  int i = 0;

  while (AT(i)->prt_max < prt_min)
    i++;
  if (AT(i)->prt_min != prt_min) {
    policy_summary_item_t* new_item;
    new_item = policy_summary_item_split(AT(i), prt_min);
    smartlist_insert(summary, i+1, new_item);
    i++;
  }
  start_at_index = i;

  while (AT(i)->prt_max < prt_max)
    i++;
  if (AT(i)->prt_max != prt_max) {
    policy_summary_item_t* new_item;
    new_item = policy_summary_item_split(AT(i), prt_max+1);
    smartlist_insert(summary, i+1, new_item);
  }

  return start_at_index;
}

/** Mark port ranges as accepted if they are below the reject_count for family
 */
static void
policy_summary_accept(smartlist_t *summary,
                      uint16_t prt_min, uint16_t prt_max,
                      sa_family_t family)
{
  tor_assert_nonfatal_once(family == AF_INET || family == AF_INET6);
  uint64_t family_reject_count = ((family == AF_INET) ?
                                  REJECT_CUTOFF_COUNT_IPV4 :
                                  REJECT_CUTOFF_COUNT_IPV6);

  int i = policy_summary_split(summary, prt_min, prt_max);
  while (i < smartlist_len(summary) &&
         AT(i)->prt_max <= prt_max) {
    if (!AT(i)->accepted &&
        AT(i)->reject_count <= family_reject_count)
      AT(i)->accepted = 1;
    i++;
  }
  tor_assert(i < smartlist_len(summary) || prt_max==65535);
}

/** Count the number of addresses in a network in family with prefixlen
 * maskbits against the given portrange. */
static void
policy_summary_reject(smartlist_t *summary,
                      maskbits_t maskbits,
                      uint16_t prt_min, uint16_t prt_max,
                      sa_family_t family)
{
  tor_assert_nonfatal_once(family == AF_INET || family == AF_INET6);

  int i = policy_summary_split(summary, prt_min, prt_max);

  /* The length of a single address mask */
  int addrbits = (family == AF_INET) ? IPV4_BITS : IPV6_BITS;
  tor_assert_nonfatal_once(addrbits >= maskbits);

  /* We divide IPv6 address counts by (1 << scale) to keep them in a uint64_t
   */
  int scale = ((family == AF_INET) ?
               REJECT_CUTOFF_SCALE_IPV4 :
               REJECT_CUTOFF_SCALE_IPV6);

  tor_assert_nonfatal_once(addrbits >= scale);
  if (maskbits > (addrbits - scale)) {
    tor_assert_nonfatal_once(family == AF_INET6);
    /* The address range is so small, we'd need billions of them to reach the
     * rejection limit. So we ignore this range in the reject count. */
    return;
  }

  uint64_t count = 0;
  if (addrbits - scale - maskbits >= 64) {
    tor_assert_nonfatal_once(family == AF_INET6);
    /* The address range is so large, it's an automatic rejection for all ports
     * in the range. */
    count = UINT64_MAX;
  } else {
    count = (UINT64_C(1) << (addrbits - scale - maskbits));
  }
  tor_assert_nonfatal_once(count > 0);
  while (i < smartlist_len(summary) &&
         AT(i)->prt_max <= prt_max) {
    if (AT(i)->reject_count <= UINT64_MAX - count) {
      AT(i)->reject_count += count;
    } else {
      /* IPv4 would require a 4-billion address redundant policy to get here,
       * but IPv6 just needs to have ::/0 */
      if (family == AF_INET) {
        tor_assert_nonfatal_unreached_once();
      }
      /* If we do get here, use saturating arithmetic */
      AT(i)->reject_count = UINT64_MAX;
    }
    i++;
  }
  tor_assert(i < smartlist_len(summary) || prt_max==65535);
}

/** Add a single exit policy item to our summary:
 *
 *  If it is an accept, ignore it unless it is for all IP addresses
 *  ("*", i.e. its prefixlen/maskbits is 0). Otherwise call
 *  policy_summary_accept().
 *
 *  If it is a reject, ignore it if it is about one of the private
 *  networks. Otherwise call policy_summary_reject().
 */
static void
policy_summary_add_item(smartlist_t *summary, addr_policy_t *p)
{
  if (p->policy_type == ADDR_POLICY_ACCEPT) {
    if (p->maskbits == 0) {
      policy_summary_accept(summary, p->prt_min, p->prt_max, p->addr.family);
    }
  } else if (p->policy_type == ADDR_POLICY_REJECT) {

     int is_private = 0;
     int i;
     for (i = 0; private_nets[i]; ++i) {
       tor_addr_t addr;
       maskbits_t maskbits;
       if (tor_addr_parse_mask_ports(private_nets[i], 0, &addr,
                                     &maskbits, NULL, NULL)<0) {
         tor_assert(0);
       }
       if (tor_addr_compare(&p->addr, &addr, CMP_EXACT) == 0 &&
           p->maskbits == maskbits) {
         is_private = 1;
         break;
       }
     }

     if (!is_private) {
       policy_summary_reject(summary, p->maskbits, p->prt_min, p->prt_max,
                             p->addr.family);
     }
  } else
    tor_assert(0);
}

/** Create a string representing a summary for an exit policy.
 * The summary will either be an "accept" plus a comma-separated list of port
 * ranges or a "reject" plus port-ranges, depending on which is shorter.
 *
 * If no exits are allowed at all then "reject 1-65535" is returned. If no
 * ports are blocked instead of "reject " we return "accept 1-65535". (These
 * are an exception to the shorter-representation-wins rule).
 */
char *
policy_summarize(smartlist_t *policy, sa_family_t family)
{
  smartlist_t *summary = policy_summary_create();
  smartlist_t *accepts, *rejects;
  int i, last, start_prt;
  size_t accepts_len, rejects_len;
  char *accepts_str = NULL, *rejects_str = NULL, *shorter_str, *result;
  const char *prefix;

  tor_assert(policy);

  /* Create the summary list */
  SMARTLIST_FOREACH_BEGIN(policy, addr_policy_t *, p) {
    sa_family_t f = tor_addr_family(&p->addr);
    if (f != AF_INET && f != AF_INET6) {
      log_warn(LD_BUG, "Weird family when summarizing address policy");
    }
    if (f != family)
      continue;
    policy_summary_add_item(summary, p);
  } SMARTLIST_FOREACH_END(p);

  /* Now create two lists of strings, one for accepted and one
   * for rejected ports.  We take care to merge ranges so that
   * we avoid getting stuff like "1-4,5-9,10", instead we want
   * "1-10"
   */
  i = 0;
  start_prt = 1;
  accepts = smartlist_new();
  rejects = smartlist_new();
  while (1) {
    last = i == smartlist_len(summary)-1;
    if (last ||
        AT(i)->accepted != AT(i+1)->accepted) {
      char buf[POLICY_BUF_LEN];

      if (start_prt == AT(i)->prt_max)
        tor_snprintf(buf, sizeof(buf), "%d", start_prt);
      else
        tor_snprintf(buf, sizeof(buf), "%d-%d", start_prt, AT(i)->prt_max);

      if (AT(i)->accepted)
        smartlist_add_strdup(accepts, buf);
      else
        smartlist_add_strdup(rejects, buf);

      if (last)
        break;

      start_prt = AT(i+1)->prt_min;
    };
    i++;
  };

  /* Figure out which of the two stringlists will be shorter and use
   * that to build the result
   */
  if (smartlist_len(accepts) == 0) { /* no exits at all */
    result = tor_strdup("reject 1-65535");
    goto cleanup;
  }
  if (smartlist_len(rejects) == 0) { /* no rejects at all */
    result = tor_strdup("accept 1-65535");
    goto cleanup;
  }

  accepts_str = smartlist_join_strings(accepts, ",", 0, &accepts_len);
  rejects_str = smartlist_join_strings(rejects, ",", 0, &rejects_len);

  if (rejects_len > MAX_EXITPOLICY_SUMMARY_LEN-strlen("reject")-1 &&
      accepts_len > MAX_EXITPOLICY_SUMMARY_LEN-strlen("accept")-1) {
    char *c;
    shorter_str = accepts_str;
    prefix = "accept";

    c = shorter_str + (MAX_EXITPOLICY_SUMMARY_LEN-strlen(prefix)-1);
    while (*c != ',' && c >= shorter_str)
      c--;
    tor_assert(c >= shorter_str);
    tor_assert(*c == ',');
    *c = '\0';

  } else if (rejects_len < accepts_len) {
    shorter_str = rejects_str;
    prefix = "reject";
  } else {
    shorter_str = accepts_str;
    prefix = "accept";
  }

  tor_asprintf(&result, "%s %s", prefix, shorter_str);

 cleanup:
  /* cleanup */
  SMARTLIST_FOREACH(summary, policy_summary_item_t *, s, tor_free(s));
  smartlist_free(summary);

  tor_free(accepts_str);
  SMARTLIST_FOREACH(accepts, char *, s, tor_free(s));
  smartlist_free(accepts);

  tor_free(rejects_str);
  SMARTLIST_FOREACH(rejects, char *, s, tor_free(s));
  smartlist_free(rejects);

  return result;
}

/** Convert a summarized policy string into a short_policy_t.  Return NULL
 * if the string is not well-formed. */
short_policy_t *
parse_short_policy(const char *summary)
{
  const char *orig_summary = summary;
  short_policy_t *result;
  int is_accept;
  int n_entries;
  short_policy_entry_t entries[MAX_EXITPOLICY_SUMMARY_LEN]; /* overkill */
  char *next;

  if (!strcmpstart(summary, "accept ")) {
    is_accept = 1;
    summary += strlen("accept ");
  } else if (!strcmpstart(summary, "reject ")) {
    is_accept = 0;
    summary += strlen("reject ");
  } else {
    log_fn(LOG_PROTOCOL_WARN, LD_DIR, "Unrecognized policy summary keyword");
    return NULL;
  }

  n_entries = 0;
  for ( ; *summary; summary = next) {
    if (n_entries == MAX_EXITPOLICY_SUMMARY_LEN) {
      log_fn(LOG_PROTOCOL_WARN, LD_DIR, "Impossibly long policy summary %s",
             escaped(orig_summary));
      return NULL;
    }

    unsigned low, high;
    int ok;
    low = (unsigned) tor_parse_ulong(summary, 10, 1, 65535, &ok, &next);
    if (!ok) {
      if (! TOR_ISDIGIT(*summary) || *summary == ',') {
        /* Unrecognized format: skip it. */
        goto skip_ent;
      } else {
        goto bad_ent;
      }
    }

    switch (*next) {
      case ',':
        ++next;
        FALLTHROUGH;
      case '\0':
        high = low;
        break;
      case '-':
        high = (unsigned) tor_parse_ulong(next+1, 10, low, 65535, &ok, &next);
        if (!ok)
          goto bad_ent;

        if (*next == ',')
          ++next;
        else if (*next != '\0')
          goto bad_ent;

        break;
      default:
        goto bad_ent;
    }

    entries[n_entries].min_port = low;
    entries[n_entries].max_port = high;
    n_entries++;

    continue;
  skip_ent:
    next = strchr(next, ',');
    if (!next)
      break;
    ++next;
  }

  if (n_entries == 0) {
    log_fn(LOG_PROTOCOL_WARN, LD_DIR,
           "Found no port-range entries in summary %s", escaped(orig_summary));
    return NULL;
  }

  {
    size_t size = offsetof(short_policy_t, entries) +
      sizeof(short_policy_entry_t)*(n_entries);
    result = tor_malloc_zero(size);

    tor_assert( (char*)&result->entries[n_entries-1] < ((char*)result)+size);
  }

  result->is_accept = is_accept;
  result->n_entries = n_entries;
  memcpy(result->entries, entries, sizeof(short_policy_entry_t)*n_entries);
  return result;

 bad_ent:
  log_fn(LOG_PROTOCOL_WARN, LD_DIR,"Found bad entry in policy summary %s",
         escaped(orig_summary));
  return NULL;
}

/** Write <b>policy</b> back out into a string. */
char *
write_short_policy(const short_policy_t *policy)
{
  int i;
  char *answer;
  smartlist_t *sl = smartlist_new();

  smartlist_add_asprintf(sl, "%s", policy->is_accept ? "accept " : "reject ");

  for (i=0; i < policy->n_entries; i++) {
    const short_policy_entry_t *e = &policy->entries[i];
    if (e->min_port == e->max_port) {
      smartlist_add_asprintf(sl, "%d", e->min_port);
    } else {
      smartlist_add_asprintf(sl, "%d-%d", e->min_port, e->max_port);
    }
    if (i < policy->n_entries-1)
      smartlist_add_strdup(sl, ",");
  }
  answer = smartlist_join_strings(sl, "", 0, NULL);
  SMARTLIST_FOREACH(sl, char *, a, tor_free(a));
  smartlist_free(sl);
  return answer;
}

/** Release all storage held in <b>policy</b>. */
void
short_policy_free_(short_policy_t *policy)
{
  tor_free(policy);
}

/** See whether the <b>addr</b>:<b>port</b> address is likely to be accepted
 * or rejected by the summarized policy <b>policy</b>.  Return values are as
 * for compare_tor_addr_to_addr_policy.  Unlike the regular addr_policy
 * functions, requires the <b>port</b> be specified. */
addr_policy_result_t
compare_tor_addr_to_short_policy(const tor_addr_t *addr, uint16_t port,
                                 const short_policy_t *policy)
{
  int i;
  int found_match = 0;
  int accept_;

  tor_assert(port != 0);

  if (addr && tor_addr_is_null(addr))
    addr = NULL; /* Unspec means 'no address at all,' in this context. */

  if (addr && get_options()->ClientRejectInternalAddresses &&
      (tor_addr_is_internal(addr, 0) || tor_addr_is_loopback(addr)))
    return ADDR_POLICY_REJECTED;

  for (i=0; i < policy->n_entries; ++i) {
    const short_policy_entry_t *e = &policy->entries[i];
    if (e->min_port <= port && port <= e->max_port) {
      found_match = 1;
      break;
    }
  }

  if (found_match)
    accept_ = policy->is_accept;
  else
    accept_ = ! policy->is_accept;

  /* ???? are these right? -NM */
  /* We should be sure not to return ADDR_POLICY_ACCEPTED in the accept
   * case here, because it would cause clients to believe that the node
   * allows exit enclaving. Trying it anyway would open up a cool attack
   * where the node refuses due to exitpolicy, the client reacts in
   * surprise by rewriting the node's exitpolicy to reject *:*, and then
   * an adversary targets users by causing them to attempt such connections
   * to 98% of the exits.
   *
   * Once microdescriptors can handle addresses in special cases (e.g. if
   * we ever solve ticket 1774), we can provide certainty here. -RD */
  if (accept_)
    return ADDR_POLICY_PROBABLY_ACCEPTED;
  else
    return ADDR_POLICY_REJECTED;
}

/** Return true iff <b>policy</b> seems reject all ports */
int
short_policy_is_reject_star(const short_policy_t *policy)
{
  /* This doesn't need to be as much on the lookout as policy_is_reject_star,
   * since policy summaries are from the consensus or from consensus
   * microdescs.
   */
  tor_assert(policy);
  /* Check for an exact match of "reject 1-65535". */
  return (policy->is_accept == 0 && policy->n_entries == 1 &&
          policy->entries[0].min_port == 1 &&
          policy->entries[0].max_port == 65535);
}

/** Decide whether addr:port is probably or definitely accepted or rejected by
 * <b>node</b>.  See compare_tor_addr_to_addr_policy for details on addr/port
 * interpretation. */
addr_policy_result_t
compare_tor_addr_to_node_policy(const tor_addr_t *addr, uint16_t port,
                                const node_t *node)
{
  if (node->rejects_all)
    return ADDR_POLICY_REJECTED;

  if (addr && tor_addr_family(addr) == AF_INET6) {
    const short_policy_t *p = NULL;
    if (node->ri)
      p = node->ri->ipv6_exit_policy;
    else if (node->md)
      p = node->md->ipv6_exit_policy;
    if (p)
      return compare_tor_addr_to_short_policy(addr, port, p);
    else
      return ADDR_POLICY_REJECTED;
  }

  if (node->ri) {
    return compare_tor_addr_to_addr_policy(addr, port, node->ri->exit_policy);
  } else if (node->md) {
    if (node->md->exit_policy == NULL)
      return ADDR_POLICY_REJECTED;
    else
      return compare_tor_addr_to_short_policy(addr, port,
                                              node->md->exit_policy);
  } else {
    return ADDR_POLICY_PROBABLY_REJECTED;
  }
}

/**
 * Given <b>policy_list</b>, a list of addr_policy_t, produce a string
 * representation of the list.
 * If <b>include_ipv4</b> is true, include IPv4 entries.
 * If <b>include_ipv6</b> is true, include IPv6 entries.
 */
char *
policy_dump_to_string(const smartlist_t *policy_list,
                      int include_ipv4,
                      int include_ipv6)
{
  smartlist_t *policy_string_list;
  char *policy_string = NULL;

  policy_string_list = smartlist_new();

  SMARTLIST_FOREACH_BEGIN(policy_list, addr_policy_t *, tmpe) {
    char *pbuf;
    int bytes_written_to_pbuf;
    if ((tor_addr_family(&tmpe->addr) == AF_INET6) && (!include_ipv6)) {
      continue; /* Don't include IPv6 parts of address policy */
    }
    if ((tor_addr_family(&tmpe->addr) == AF_INET) && (!include_ipv4)) {
      continue; /* Don't include IPv4 parts of address policy */
    }

    pbuf = tor_malloc(POLICY_BUF_LEN);
    bytes_written_to_pbuf = policy_write_item(pbuf,POLICY_BUF_LEN, tmpe, 1);

    if (bytes_written_to_pbuf < 0) {
      log_warn(LD_BUG, "policy_dump_to_string ran out of room!");
      tor_free(pbuf);
      goto done;
    }

    smartlist_add(policy_string_list,pbuf);
  } SMARTLIST_FOREACH_END(tmpe);

  policy_string = smartlist_join_strings(policy_string_list, "\n", 0, NULL);

 done:
  SMARTLIST_FOREACH(policy_string_list, char *, str, tor_free(str));
  smartlist_free(policy_string_list);

  return policy_string;
}

/** Implementation for GETINFO control command: knows the answer for questions
 * about "exit-policy/..." */
int
getinfo_helper_policies(control_connection_t *conn,
                        const char *question, char **answer,
                        const char **errmsg)
{
  (void) conn;
  (void) errmsg;
  if (!strcmp(question, "exit-policy/default")) {
    *answer = tor_strdup(DEFAULT_EXIT_POLICY);
  } else if (!strcmp(question, "exit-policy/reject-private/default")) {
    smartlist_t *private_policy_strings;
    const char **priv = private_nets;

    private_policy_strings = smartlist_new();

    while (*priv != NULL) {
      /* IPv6 addresses are in "[]" and contain ":",
       * IPv4 addresses are not in "[]" and contain "." */
      smartlist_add_asprintf(private_policy_strings, "reject %s:*", *priv);
      priv++;
    }

    *answer = smartlist_join_strings(private_policy_strings,
                                     ",", 0, NULL);

    SMARTLIST_FOREACH(private_policy_strings, char *, str, tor_free(str));
    smartlist_free(private_policy_strings);
  } else if (!strcmp(question, "exit-policy/reject-private/relay")) {
    const or_options_t *options = get_options();
    int err = 0;
    const routerinfo_t *me = router_get_my_routerinfo_with_err(&err);

    if (!me) {
      *errmsg = routerinfo_err_to_string(err);
      return routerinfo_err_is_transient(err) ? -1 : 0;
    }

    if (!options->ExitPolicyRejectPrivate &&
        !options->ExitPolicyRejectLocalInterfaces) {
      *answer = tor_strdup("");
      return 0;
    }

    smartlist_t *private_policy_list = smartlist_new();
    smartlist_t *configured_addresses = smartlist_new();

    /* Copy the configured addresses into the tor_addr_t* list */
    if (options->ExitPolicyRejectPrivate) {
      policies_copy_addr_to_smartlist(configured_addresses, &me->ipv4_addr);
      policies_copy_addr_to_smartlist(configured_addresses, &me->ipv6_addr);
    }

    if (options->ExitPolicyRejectLocalInterfaces) {
      policies_copy_outbound_addresses_to_smartlist(configured_addresses,
                                                    options);
    }

    policies_parse_exit_policy_reject_private(
      &private_policy_list,
      options->IPv6Exit,
      configured_addresses,
      options->ExitPolicyRejectLocalInterfaces,
      options->ExitPolicyRejectLocalInterfaces);
    *answer = policy_dump_to_string(private_policy_list, 1, 1);

    addr_policy_list_free(private_policy_list);
    SMARTLIST_FOREACH(configured_addresses, tor_addr_t *, a, tor_free(a));
    smartlist_free(configured_addresses);
  } else if (!strcmpstart(question, "exit-policy/")) {
    int include_ipv4 = 0;
    int include_ipv6 = 0;

    int err = 0;
    const routerinfo_t *me = router_get_my_routerinfo_with_err(&err);

    if (!me) {
      *errmsg = routerinfo_err_to_string(err);
      return routerinfo_err_is_transient(err) ? -1 : 0;
    }

    if (!strcmp(question, "exit-policy/ipv4")) {
      include_ipv4 = 1;
    } else if (!strcmp(question, "exit-policy/ipv6")) {
      include_ipv6 = 1;
    } else if (!strcmp(question, "exit-policy/full")) {
      include_ipv4 = include_ipv6 = 1;
    } else {
      return 0; /* No such key. */
    }

    *answer = router_dump_exit_policy_to_string(me,include_ipv4,
                                                include_ipv6);
  }

  return 0;
}

/** Release all storage held by <b>p</b>. */
void
addr_policy_list_free_(smartlist_t *lst)
{
  if (!lst)
    return;
  SMARTLIST_FOREACH(lst, addr_policy_t *, policy, addr_policy_free(policy));
  smartlist_free(lst);
}

/** Release all storage held by <b>p</b>. */
void
addr_policy_free_(addr_policy_t *p)
{
  if (!p)
    return;

  if (--p->refcnt <= 0) {
    if (p->is_canonical) {
      policy_map_ent_t search, *found;
      search.policy = p;
      found = HT_REMOVE(policy_map, &policy_root, &search);
      if (found) {
        tor_assert(p == found->policy);
        tor_free(found);
      }
    }
    tor_free(p);
  }
}

/** Release all storage held by policy variables. */
void
policies_free_all(void)
{
  addr_policy_list_free(reachable_or_addr_policy);
  reachable_or_addr_policy = NULL;
  addr_policy_list_free(reachable_dir_addr_policy);
  reachable_dir_addr_policy = NULL;
  addr_policy_list_free(socks_policy);
  socks_policy = NULL;
  addr_policy_list_free(dir_policy);
  dir_policy = NULL;
  addr_policy_list_free(metrics_policy);
  metrics_policy = NULL;
  addr_policy_list_free(authdir_reject_policy);
  authdir_reject_policy = NULL;
  addr_policy_list_free(authdir_invalid_policy);
  authdir_invalid_policy = NULL;
  addr_policy_list_free(authdir_badexit_policy);
  authdir_badexit_policy = NULL;
  addr_policy_list_free(authdir_middleonly_policy);
  authdir_middleonly_policy = NULL;

  if (!HT_EMPTY(&policy_root)) {
    policy_map_ent_t **ent;
    int n = 0;
    char buf[POLICY_BUF_LEN];

    log_warn(LD_MM, "Still had %d address policies cached at shutdown.",
             (int)HT_SIZE(&policy_root));

    /* Note the first 10 cached policies to try to figure out where they
     * might be coming from. */
    HT_FOREACH(ent, policy_map, &policy_root) {
      if (++n > 10)
        break;
      if (policy_write_item(buf, sizeof(buf), (*ent)->policy, 0) >= 0)
        log_warn(LD_MM,"  %d [%d]: %s", n, (*ent)->policy->refcnt, buf);
    }
  }
  HT_CLEAR(policy_map, &policy_root);
}