tor

policies.c (110614B)

---

/* 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 *:18080-18081,accept *:18089,"                                      \
 "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);
}