connection_edge.c

/* Copyright (c) 2001 Matej Pfajfar.
 * Copyright (c) 2001-2004, Roger Dingledine.
 * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson.
 * Copyright (c) 2007-2008, The Tor Project, Inc. */
/* See LICENSE for licensing information */

/**
 * \file connection_edge.c
 * \brief Handle edge streams.
 **/

#include "or.h"

#ifdef HAVE_LINUX_TYPES_H
#include <linux/types.h>
#endif
#ifdef HAVE_LINUX_NETFILTER_IPV4_H
#include <linux/netfilter_ipv4.h>
#define TRANS_NETFILTER
#endif

#if defined(HAVE_NET_IF_H) && defined(HAVE_NET_PFVAR_H)
#include <net/if.h>
#include <net/pfvar.h>
#define TRANS_PF
#endif

#define SOCKS4_GRANTED          90
#define SOCKS4_REJECT           91

static int connection_ap_handshake_process_socks(edge_connection_t *conn);
static int connection_ap_process_natd(edge_connection_t *conn);
static int connection_exit_connect_dir(edge_connection_t *exitconn);
static int address_is_in_virtual_range(const char *addr);
static int consider_plaintext_ports(edge_connection_t *conn, uint16_t port);
static void clear_trackexithost_mappings(const char *exitname);

/** An AP stream has failed/finished. If it hasn't already sent back
 * a socks reply, send one now (based on endreason). Also set
 * has_sent_end to 1, and mark the conn.
 */
void
_connection_mark_unattached_ap(edge_connection_t *conn, int endreason,
                               int line, const char *file)
{
  tor_assert(conn->_base.type == CONN_TYPE_AP);
  conn->edge_has_sent_end = 1; /* no circ yet */

  if (conn->_base.marked_for_close) {
    /* This call will warn as appropriate. */
    _connection_mark_for_close(TO_CONN(conn), line, file);
    return;
  }

  if (!conn->socks_request->has_finished) {
    if (endreason & END_STREAM_REASON_FLAG_ALREADY_SOCKS_REPLIED)
      log_warn(LD_BUG,
               "stream (marked at %s:%d) sending two socks replies?",
               file, line);

    if (SOCKS_COMMAND_IS_CONNECT(conn->socks_request->command))
      connection_ap_handshake_socks_reply(conn, NULL, 0, endreason);
    else if (SOCKS_COMMAND_IS_RESOLVE(conn->socks_request->command))
      connection_ap_handshake_socks_resolved(conn,
                                             RESOLVED_TYPE_ERROR_TRANSIENT,
                                             0, NULL, -1, -1);
    else /* unknown or no handshake at all. send no response. */
      conn->socks_request->has_finished = 1;
  }

  _connection_mark_for_close(TO_CONN(conn), line, file);
  conn->_base.hold_open_until_flushed = 1;
  conn->end_reason = endreason;
}

/** There was an EOF. Send an end and mark the connection for close.
 */
int
connection_edge_reached_eof(edge_connection_t *conn)
{
  if (buf_datalen(conn->_base.inbuf) &&
      connection_state_is_open(TO_CONN(conn))) {
    /* it still has stuff to process. don't let it die yet. */
    return 0;
  }
  log_info(LD_EDGE,"conn (fd %d) reached eof. Closing.", conn->_base.s);
  if (!conn->_base.marked_for_close) {
    /* only mark it if not already marked. it's possible to
     * get the 'end' right around when the client hangs up on us. */
    connection_edge_end(conn, END_STREAM_REASON_DONE);
    if (conn->socks_request) /* eof, so don't send a socks reply back */
      conn->socks_request->has_finished = 1;
    connection_mark_for_close(TO_CONN(conn));
  }
  return 0;
}

/** Handle new bytes on conn->inbuf based on state:
 *   - If it's waiting for socks info, try to read another step of the
 *     socks handshake out of conn->inbuf.
 *   - If it's waiting for the original destination, fetch it.
 *   - If it's open, then package more relay cells from the stream.
 *   - Else, leave the bytes on inbuf alone for now.
 *
 * Mark and return -1 if there was an unexpected error with the conn,
 * else return 0.
 */
int
connection_edge_process_inbuf(edge_connection_t *conn, int package_partial)
{
  tor_assert(conn);

  switch (conn->_base.state) {
    case AP_CONN_STATE_SOCKS_WAIT:
      if (connection_ap_handshake_process_socks(conn) < 0) {
        /* already marked */
        return -1;
      }
      return 0;
    case AP_CONN_STATE_NATD_WAIT:
      if (connection_ap_process_natd(conn) < 0) {
        /* already marked */
        return -1;
      }
      return 0;
    case AP_CONN_STATE_OPEN:
    case EXIT_CONN_STATE_OPEN:
      if (connection_edge_package_raw_inbuf(conn, package_partial) < 0) {
        /* (We already sent an end cell if possible) */
        connection_mark_for_close(TO_CONN(conn));
        return -1;
      }
      return 0;
    case EXIT_CONN_STATE_CONNECTING:
    case AP_CONN_STATE_RENDDESC_WAIT:
    case AP_CONN_STATE_CIRCUIT_WAIT:
    case AP_CONN_STATE_CONNECT_WAIT:
    case AP_CONN_STATE_RESOLVE_WAIT:
    case AP_CONN_STATE_CONTROLLER_WAIT:
      log_info(LD_EDGE,
               "data from edge while in '%s' state. Leaving it on buffer.",
               conn_state_to_string(conn->_base.type, conn->_base.state));
      return 0;
  }
  log_warn(LD_BUG,"Got unexpected state %d. Closing.",conn->_base.state);
  tor_fragile_assert();
  connection_edge_end(conn, END_STREAM_REASON_INTERNAL);
  connection_mark_for_close(TO_CONN(conn));
  return -1;
}

/** This edge needs to be closed, because its circuit has closed.
 * Mark it for close and return 0.
 */
int
connection_edge_destroy(circid_t circ_id, edge_connection_t *conn)
{
  if (!conn->_base.marked_for_close) {
    log_info(LD_EDGE,
             "CircID %d: At an edge. Marking connection for close.", circ_id);
    if (conn->_base.type == CONN_TYPE_AP) {
      connection_mark_unattached_ap(conn, END_STREAM_REASON_DESTROY);
      control_event_stream_status(conn, STREAM_EVENT_CLOSED,
                                  END_STREAM_REASON_DESTROY);
      conn->end_reason |= END_STREAM_REASON_FLAG_ALREADY_SENT_CLOSED;
    } else {
      /* closing the circuit, nothing to send an END to */
      conn->edge_has_sent_end = 1;
      conn->end_reason = END_STREAM_REASON_DESTROY;
      conn->end_reason |= END_STREAM_REASON_FLAG_ALREADY_SENT_CLOSED;
      connection_mark_for_close(TO_CONN(conn));
      conn->_base.hold_open_until_flushed = 1;
    }
  }
  conn->cpath_layer = NULL;
  conn->on_circuit = NULL;
  return 0;
}

/** Send a raw end cell to the stream with ID <b>stream_id</b> out over the
 * <b>circ</b> towards the hop identified with <b>cpath_layer</b>. If this
 * is not a client connection, set the relay end cell's reason for closing
 * as <b>reason</b> */
static int
relay_send_end_cell_from_edge(streamid_t stream_id, circuit_t *circ,
                              uint8_t reason, crypt_path_t *cpath_layer)
{
  char payload[1];

  if (CIRCUIT_PURPOSE_IS_CLIENT(circ->purpose)) {
    /* Never send the server an informative reason code; it doesn't need to
     * know why the client stream is failing. */
    reason = END_STREAM_REASON_MISC;
  }

  payload[0] = (char) reason;

  return relay_send_command_from_edge(stream_id, circ, RELAY_COMMAND_END,
                                      payload, 1, cpath_layer);
}

/** Send a relay end cell from stream <b>conn</b> down conn's circuit, and
 * remember that we've done so.  If this is not a client connection, set the
 * relay end cell's reason for closing as <b>reason</b>.
 *
 * Return -1 if this function has already been called on this conn,
 * else return 0.
 */
int
connection_edge_end(edge_connection_t *conn, uint8_t reason)
{
  char payload[RELAY_PAYLOAD_SIZE];
  size_t payload_len=1;
  circuit_t *circ;
  uint8_t control_reason = reason;

  if (conn->edge_has_sent_end) {
    log_warn(LD_BUG,"(Harmless.) Calling connection_edge_end (reason %d) "
             "on an already ended stream?", reason);
    tor_fragile_assert();
    return -1;
  }

  if (conn->_base.marked_for_close) {
    log_warn(LD_BUG,
             "called on conn that's already marked for close at %s:%d.",
             conn->_base.marked_for_close_file, conn->_base.marked_for_close);
    return 0;
  }

  circ = circuit_get_by_edge_conn(conn);
  if (circ && CIRCUIT_PURPOSE_IS_CLIENT(circ->purpose)) {
    /* If this is a client circuit, don't send the server an informative
     * reason code; it doesn't need to know why the client stream is
     * failing. */
    reason = END_STREAM_REASON_MISC;
  }

  payload[0] = (char)reason;
  if (reason == END_STREAM_REASON_EXITPOLICY &&
      !connection_edge_is_rendezvous_stream(conn)) {
    int addrlen;
    if (tor_addr_family(&conn->_base.addr) == AF_INET) {
      set_uint32(payload+1, tor_addr_to_ipv4n(&conn->_base.addr));
      addrlen = 4;
    } else {
      memcpy(payload+1, tor_addr_to_in6_addr8(&conn->_base.addr), 16);
      addrlen = 16;
    }
    set_uint32(payload+1+addrlen, htonl(dns_clip_ttl(conn->address_ttl)));
    payload_len += 4+addrlen;
  }

  if (circ && !circ->marked_for_close) {
    log_debug(LD_EDGE,"Sending end on conn (fd %d).",conn->_base.s);
    connection_edge_send_command(conn, RELAY_COMMAND_END,
                                 payload, payload_len);
  } else {
    log_debug(LD_EDGE,"No circ to send end on conn (fd %d).",
              conn->_base.s);
  }

  conn->edge_has_sent_end = 1;
  conn->end_reason = control_reason;
  return 0;
}

/** An error has just occured on an operation on an edge connection
 * <b>conn</b>.  Extract the errno; convert it to an end reason, and send an
 * appropriate relay end cell to the other end of the connection's circuit.
 **/
int
connection_edge_end_errno(edge_connection_t *conn)
{
  uint8_t reason;
  tor_assert(conn);
  reason = errno_to_stream_end_reason(tor_socket_errno(conn->_base.s));
  return connection_edge_end(conn, reason);
}

/** Connection <b>conn</b> has finished writing and has no bytes left on
 * its outbuf.
 *
 * If it's in state 'open', stop writing, consider responding with a
 * sendme, and return.
 * Otherwise, stop writing and return.
 *
 * If <b>conn</b> is broken, mark it for close and return -1, else
 * return 0.
 */
int
connection_edge_finished_flushing(edge_connection_t *conn)
{
  tor_assert(conn);

  switch (conn->_base.state) {
    case AP_CONN_STATE_OPEN:
    case EXIT_CONN_STATE_OPEN:
      connection_stop_writing(TO_CONN(conn));
      connection_edge_consider_sending_sendme(conn);
      return 0;
    case AP_CONN_STATE_SOCKS_WAIT:
    case AP_CONN_STATE_NATD_WAIT:
    case AP_CONN_STATE_RENDDESC_WAIT:
    case AP_CONN_STATE_CIRCUIT_WAIT:
    case AP_CONN_STATE_CONNECT_WAIT:
    case AP_CONN_STATE_CONTROLLER_WAIT:
      connection_stop_writing(TO_CONN(conn));
      return 0;
    default:
      log_warn(LD_BUG, "Called in unexpected state %d.",conn->_base.state);
      tor_fragile_assert();
      return -1;
  }
  return 0;
}

/** Connected handler for exit connections: start writing pending
 * data, deliver 'CONNECTED' relay cells as appropriate, and check
 * any pending data that may have been received. */
int
connection_edge_finished_connecting(edge_connection_t *edge_conn)
{
  connection_t *conn;

  tor_assert(edge_conn);
  tor_assert(edge_conn->_base.type == CONN_TYPE_EXIT);
  conn = TO_CONN(edge_conn);
  tor_assert(conn->state == EXIT_CONN_STATE_CONNECTING);

  log_info(LD_EXIT,"Exit connection to %s:%u (%s) established.",
           escaped_safe_str(conn->address),conn->port,
           fmt_addr(&conn->addr));

  conn->state = EXIT_CONN_STATE_OPEN;
  connection_watch_events(conn, EV_READ); /* stop writing, continue reading */
  if (connection_wants_to_flush(conn)) /* in case there are any queued relay
                                        * cells */
    connection_start_writing(conn);
  /* deliver a 'connected' relay cell back through the circuit. */
  if (connection_edge_is_rendezvous_stream(edge_conn)) {
    if (connection_edge_send_command(edge_conn,
                                     RELAY_COMMAND_CONNECTED, NULL, 0) < 0)
      return 0; /* circuit is closed, don't continue */
  } else {
    char connected_payload[20];
    int connected_payload_len;
    if (tor_addr_family(&conn->addr) == AF_INET) {
      set_uint32(connected_payload, tor_addr_to_ipv4n(&conn->addr));
      set_uint32(connected_payload+4,
                 htonl(dns_clip_ttl(edge_conn->address_ttl)));
      connected_payload_len = 8;
    } else {
      memcpy(connected_payload, tor_addr_to_in6_addr8(&conn->addr), 16);
      set_uint32(connected_payload+16,
                 htonl(dns_clip_ttl(edge_conn->address_ttl)));
      connected_payload_len = 20;
    }
    if (connection_edge_send_command(edge_conn,
                                 RELAY_COMMAND_CONNECTED,
                                 connected_payload, connected_payload_len) < 0)
      return 0; /* circuit is closed, don't continue */
  }
  tor_assert(edge_conn->package_window > 0);
  /* in case the server has written anything */
  return connection_edge_process_inbuf(edge_conn, 1);
}

/** Define a schedule for how long to wait between retrying
 * application connections. Rather than waiting a fixed amount of
 * time between each retry, we wait 10 seconds each for the first
 * two tries, and 15 seconds for each retry after
 * that. Hopefully this will improve the expected user experience. */
static int
compute_retry_timeout(edge_connection_t *conn)
{
  if (conn->num_socks_retries < 2) /* try 0 and try 1 */
    return 10;
  return 15;
}

/** Find all general-purpose AP streams waiting for a response that sent their
 * begin/resolve cell >=15 seconds ago. Detach from their current circuit, and
 * mark their current circuit as unsuitable for new streams. Then call
 * connection_ap_handshake_attach_circuit() to attach to a new circuit (if
 * available) or launch a new one.
 *
 * For rendezvous streams, simply give up after SocksTimeout seconds (with no
 * retry attempt).
 */
void
connection_ap_expire_beginning(void)
{
  edge_connection_t *conn;
  circuit_t *circ;
  time_t now = time(NULL);
  or_options_t *options = get_options();
  int severity;
  int cutoff;
  int seconds_idle;
  smartlist_t *conns = get_connection_array();

  SMARTLIST_FOREACH_BEGIN(conns, connection_t *, c) {
    if (c->type != CONN_TYPE_AP)
      continue;
    conn = TO_EDGE_CONN(c);
    /* if it's an internal linked connection, don't yell its status. */
    severity = (tor_addr_is_null(&conn->_base.addr) && !conn->_base.port)
      ? LOG_INFO : LOG_NOTICE;
    seconds_idle = (int)( now - conn->_base.timestamp_lastread );

    if (AP_CONN_STATE_IS_UNATTACHED(conn->_base.state)) {
      if (seconds_idle >= options->SocksTimeout) {
        log_fn(severity, LD_APP,
            "Tried for %d seconds to get a connection to %s:%d. "
            "Giving up. (%s)",
            seconds_idle, safe_str(conn->socks_request->address),
            conn->socks_request->port,
            conn_state_to_string(CONN_TYPE_AP, conn->_base.state));
        connection_mark_unattached_ap(conn, END_STREAM_REASON_TIMEOUT);
      }
      continue;
    }

    if (conn->_base.state == AP_CONN_STATE_OPEN)
      continue;

    /* We're in state connect_wait or resolve_wait now -- waiting for a
     * reply to our relay cell. See if we want to retry/give up. */

    cutoff = compute_retry_timeout(conn);
    if (seconds_idle < cutoff)
      continue;
    circ = circuit_get_by_edge_conn(conn);
    if (!circ) { /* it's vanished? */
      log_info(LD_APP,"Conn is waiting (address %s), but lost its circ.",
               safe_str(conn->socks_request->address));
      connection_mark_unattached_ap(conn, END_STREAM_REASON_TIMEOUT);
      continue;
    }
    if (circ->purpose == CIRCUIT_PURPOSE_C_REND_JOINED) {
      if (seconds_idle >= options->SocksTimeout) {
        log_fn(severity, LD_REND,
               "Rend stream is %d seconds late. Giving up on address"
               " '%s.onion'.",
               seconds_idle,
               safe_str(conn->socks_request->address));
        connection_edge_end(conn, END_STREAM_REASON_TIMEOUT);
        connection_mark_unattached_ap(conn, END_STREAM_REASON_TIMEOUT);
      }
      continue;
    }
    tor_assert(circ->purpose == CIRCUIT_PURPOSE_C_GENERAL);
    log_fn(cutoff < 15 ? LOG_INFO : severity, LD_APP,
           "We tried for %d seconds to connect to '%s' using exit '%s'."
           " Retrying on a new circuit.",
           seconds_idle, safe_str(conn->socks_request->address),
           conn->cpath_layer ?
             conn->cpath_layer->extend_info->nickname : "*unnamed*");
    /* send an end down the circuit */
    connection_edge_end(conn, END_STREAM_REASON_TIMEOUT);
    /* un-mark it as ending, since we're going to reuse it */
    conn->edge_has_sent_end = 0;
    conn->end_reason = 0;
    /* kludge to make us not try this circuit again, yet to allow
     * current streams on it to survive if they can: make it
     * unattractive to use for new streams */
    tor_assert(circ->timestamp_dirty);
    circ->timestamp_dirty -= options->MaxCircuitDirtiness;
    /* give our stream another 'cutoff' seconds to try */
    conn->_base.timestamp_lastread += cutoff;
    if (conn->num_socks_retries < 250) /* avoid overflow */
      conn->num_socks_retries++;
    /* move it back into 'pending' state, and try to attach. */
    if (connection_ap_detach_retriable(conn, TO_ORIGIN_CIRCUIT(circ),
                                       END_STREAM_REASON_TIMEOUT)<0) {
      if (!conn->_base.marked_for_close)
        connection_mark_unattached_ap(conn, END_STREAM_REASON_CANT_ATTACH);
    }
  } SMARTLIST_FOREACH_END(conn);
}

/** Tell any AP streams that are waiting for a new circuit to try again,
 * either attaching to an available circ or launching a new one.
 */
void
connection_ap_attach_pending(void)
{
  edge_connection_t *edge_conn;
  smartlist_t *conns = get_connection_array();
  SMARTLIST_FOREACH(conns, connection_t *, conn,
  {
    if (conn->marked_for_close ||
        conn->type != CONN_TYPE_AP ||
        conn->state != AP_CONN_STATE_CIRCUIT_WAIT)
      continue;
    edge_conn = TO_EDGE_CONN(conn);
    if (connection_ap_handshake_attach_circuit(edge_conn) < 0) {
      if (!edge_conn->_base.marked_for_close)
        connection_mark_unattached_ap(edge_conn,
                                      END_STREAM_REASON_CANT_ATTACH);
    }
  });
}

/** Tell any AP streams that are waiting for a onehop tunnel to
 * <b>failed_digest</b> that they are going to fail. */
/* XXX022 We should get rid of this function, and instead attach
 * onehop streams to circ->p_streams so they get marked in
 * circuit_mark_for_close like normal p_streams. */
void
connection_ap_fail_onehop(const char *failed_digest,
                          cpath_build_state_t *build_state)
{
  edge_connection_t *edge_conn;
  char digest[DIGEST_LEN];
  smartlist_t *conns = get_connection_array();
  SMARTLIST_FOREACH_BEGIN(conns, connection_t *, conn) {
    if (conn->marked_for_close ||
        conn->type != CONN_TYPE_AP ||
        conn->state != AP_CONN_STATE_CIRCUIT_WAIT)
      continue;
    edge_conn = TO_EDGE_CONN(conn);
    if (!edge_conn->want_onehop)
      continue;
    if (hexdigest_to_digest(edge_conn->chosen_exit_name, digest) < 0 ||
        memcmp(digest, failed_digest, DIGEST_LEN))
      continue;
    if (tor_digest_is_zero(digest)) {
      /* we don't know the digest; have to compare addr:port */
      tor_addr_t addr;
      if (!build_state || !build_state->chosen_exit ||
          !edge_conn->socks_request || !edge_conn->socks_request->address)
        continue;
      if (tor_addr_from_str(&addr, edge_conn->socks_request->address)<0 ||
          !tor_addr_eq(&build_state->chosen_exit->addr, &addr) ||
          build_state->chosen_exit->port != edge_conn->socks_request->port)
        continue;
    }
    log_info(LD_APP, "Closing onehop stream to '%s/%s' because the OR conn "
                     "just failed.", edge_conn->chosen_exit_name,
                     edge_conn->socks_request->address);
    connection_mark_unattached_ap(edge_conn, END_STREAM_REASON_TIMEOUT);
  } SMARTLIST_FOREACH_END(conn);
}

/** A circuit failed to finish on its last hop <b>info</b>. If there
 * are any streams waiting with this exit node in mind, but they
 * don't absolutely require it, make them give up on it.
 */
void
circuit_discard_optional_exit_enclaves(extend_info_t *info)
{
  edge_connection_t *edge_conn;
  routerinfo_t *r1, *r2;

  smartlist_t *conns = get_connection_array();
  SMARTLIST_FOREACH_BEGIN(conns, connection_t *, conn) {
    if (conn->marked_for_close ||
        conn->type != CONN_TYPE_AP ||
        conn->state != AP_CONN_STATE_CIRCUIT_WAIT)
      continue;
    edge_conn = TO_EDGE_CONN(conn);
    if (!edge_conn->chosen_exit_optional &&
        !edge_conn->chosen_exit_retries)
      continue;
    r1 = router_get_by_nickname(edge_conn->chosen_exit_name, 0);
    r2 = router_get_by_nickname(info->nickname, 0);
    if (!r1 || !r2 || r1 != r2)
      continue;
    tor_assert(edge_conn->socks_request);
    if (edge_conn->chosen_exit_optional) {
      log_info(LD_APP, "Giving up on enclave exit '%s' for destination %s.",
               safe_str(edge_conn->chosen_exit_name),
               escaped_safe_str(edge_conn->socks_request->address));
      edge_conn->chosen_exit_optional = 0;
      tor_free(edge_conn->chosen_exit_name); /* clears it */
      /* if this port is dangerous, warn or reject it now that we don't
       * think it'll be using an enclave. */
      consider_plaintext_ports(edge_conn, edge_conn->socks_request->port);
    }
    if (edge_conn->chosen_exit_retries) {
      if (--edge_conn->chosen_exit_retries == 0) { /* give up! */
        clear_trackexithost_mappings(edge_conn->chosen_exit_name);
        tor_free(edge_conn->chosen_exit_name); /* clears it */
        /* if this port is dangerous, warn or reject it now that we don't
         * think it'll be using an enclave. */
        consider_plaintext_ports(edge_conn, edge_conn->socks_request->port);
      }
    }
  } SMARTLIST_FOREACH_END(conn);
}

/** The AP connection <b>conn</b> has just failed while attaching or
 * sending a BEGIN or resolving on <b>circ</b>, but another circuit
 * might work. Detach the circuit, and either reattach it, launch a
 * new circuit, tell the controller, or give up as a appropriate.
 *
 * Returns -1 on err, 1 on success, 0 on not-yet-sure.
 */
int
connection_ap_detach_retriable(edge_connection_t *conn, origin_circuit_t *circ,
                               int reason)
{
  control_event_stream_status(conn, STREAM_EVENT_FAILED_RETRIABLE, reason);
  conn->_base.timestamp_lastread = time(NULL);
  if (!get_options()->LeaveStreamsUnattached || conn->use_begindir) {
    /* If we're attaching streams ourself, or if this connection is
     * a tunneled directory connection, then just attach it. */
    conn->_base.state = AP_CONN_STATE_CIRCUIT_WAIT;
    circuit_detach_stream(TO_CIRCUIT(circ),conn);
    return connection_ap_handshake_attach_circuit(conn);
  } else {
    conn->_base.state = AP_CONN_STATE_CONTROLLER_WAIT;
    circuit_detach_stream(TO_CIRCUIT(circ),conn);
    return 0;
  }
}

/** A client-side struct to remember requests to rewrite addresses
 * to new addresses. These structs are stored in the hash table
 * "addressmap" below.
 *
 * There are 5 ways to set an address mapping:
 * - A MapAddress command from the controller [permanent]
 * - An AddressMap directive in the torrc [permanent]
 * - When a TrackHostExits torrc directive is triggered [temporary]
 * - When a dns resolve succeeds [temporary]
 * - When a dns resolve fails [temporary]
 *
 * When an addressmap request is made but one is already registered,
 * the new one is replaced only if the currently registered one has
 * no "new_address" (that is, it's in the process of dns resolve),
 * or if the new one is permanent (expires==0 or 1).
 *
 * (We overload the 'expires' field, using "0" for mappings set via
 * the configuration file, "1" for mappings set from the control
 * interface, and other values for DNS and TrackHostExit mappings that can
 * expire.)
 */
typedef struct {
  char *new_address;
  time_t expires;
  addressmap_entry_source_t source:3;
  short num_resolve_failures;
} addressmap_entry_t;

/** Entry for mapping addresses to which virtual address we mapped them to. */
typedef struct {
  char *ipv4_address;
  char *hostname_address;
} virtaddress_entry_t;

/** A hash table to store client-side address rewrite instructions. */
static strmap_t *addressmap=NULL;
/**
 * Table mapping addresses to which virtual address, if any, we
 * assigned them to.
 *
 * We maintain the following invariant: if [A,B] is in
 * virtaddress_reversemap, then B must be a virtual address, and [A,B]
 * must be in addressmap.  We do not require that the converse hold:
 * if it fails, then we could end up mapping two virtual addresses to
 * the same address, which is no disaster.
 **/
static strmap_t *virtaddress_reversemap=NULL;

/** Initialize addressmap. */
void
addressmap_init(void)
{
  addressmap = strmap_new();
  virtaddress_reversemap = strmap_new();
}

/** Free the memory associated with the addressmap entry <b>_ent</b>. */
static void
addressmap_ent_free(void *_ent)
{
  addressmap_entry_t *ent = _ent;
  tor_free(ent->new_address);
  tor_free(ent);
}

/** Free storage held by a virtaddress_entry_t* entry in <b>ent</b>. */
static void
addressmap_virtaddress_ent_free(void *_ent)
{
  virtaddress_entry_t *ent = _ent;
  tor_free(ent->ipv4_address);
  tor_free(ent->hostname_address);
  tor_free(ent);
}

/** Free storage held by a virtaddress_entry_t* entry in <b>ent</b>. */
static void
addressmap_virtaddress_remove(const char *address, addressmap_entry_t *ent)
{
  if (ent && ent->new_address &&
      address_is_in_virtual_range(ent->new_address)) {
    virtaddress_entry_t *ve =
      strmap_get(virtaddress_reversemap, ent->new_address);
    /*log_fn(LOG_NOTICE,"remove reverse mapping for %s",ent->new_address);*/
    if (ve) {
      if (!strcmp(address, ve->ipv4_address))
        tor_free(ve->ipv4_address);
      if (!strcmp(address, ve->hostname_address))
        tor_free(ve->hostname_address);
      if (!ve->ipv4_address && !ve->hostname_address) {
        tor_free(ve);
        strmap_remove(virtaddress_reversemap, ent->new_address);
      }
    }
  }
}

/** Remove <b>ent</b> (which must be mapped to by <b>address</b>) from the
 * client address maps. */
static void
addressmap_ent_remove(const char *address, addressmap_entry_t *ent)
{
  addressmap_virtaddress_remove(address, ent);
  addressmap_ent_free(ent);
}

/** Unregister all TrackHostExits mappings from any address to
 * *.exitname.exit. */
static void
clear_trackexithost_mappings(const char *exitname)
{
  char *suffix;
  size_t suffix_len;
  if (!addressmap || !exitname)
    return;
  suffix_len = strlen(exitname) + 16;
  suffix = tor_malloc(suffix_len);
  tor_snprintf(suffix, suffix_len, ".%s.exit", exitname);
  tor_strlower(suffix);

  STRMAP_FOREACH_MODIFY(addressmap, address, addressmap_entry_t *, ent) {
    if (ent->source == ADDRMAPSRC_TRACKEXIT && !strcmpend(address, suffix)) {
      addressmap_ent_remove(address, ent);
      MAP_DEL_CURRENT(address);
    }
  } STRMAP_FOREACH_END;

  tor_free(suffix);
}

/** Remove all entries from the addressmap that were set via the
 * configuration file or the command line. */
void
addressmap_clear_configured(void)
{
  addressmap_get_mappings(NULL, 0, 0, 0);
}

/** Remove all entries from the addressmap that are set to expire, ever. */
void
addressmap_clear_transient(void)
{
  addressmap_get_mappings(NULL, 2, TIME_MAX, 0);
}

/** Clean out entries from the addressmap cache that were
 * added long enough ago that they are no longer valid.
 */
void
addressmap_clean(time_t now)
{
  addressmap_get_mappings(NULL, 2, now, 0);
}

/** Free all the elements in the addressmap, and free the addressmap
 * itself. */
void
addressmap_free_all(void)
{
  if (addressmap) {
    strmap_free(addressmap, addressmap_ent_free);
    addressmap = NULL;
  }
  if (virtaddress_reversemap) {
    strmap_free(virtaddress_reversemap, addressmap_virtaddress_ent_free);
    virtaddress_reversemap = NULL;
  }
}

/** Look at address, and rewrite it until it doesn't want any
 * more rewrites; but don't get into an infinite loop.
 * Don't write more than maxlen chars into address.  Return true if the
 * address changed; false otherwise.  Set *<b>expires_out</b> to the
 * expiry time of the result, or to <b>time_max</b> if the result does
 * not expire.
 */
int
addressmap_rewrite(char *address, size_t maxlen, time_t *expires_out)
{
  addressmap_entry_t *ent;
  int rewrites;
  char *cp;
  time_t expires = TIME_MAX;

  for (rewrites = 0; rewrites < 16; rewrites++) {
    ent = strmap_get(addressmap, address);

    if (!ent || !ent->new_address) {
      if (expires_out)
        *expires_out = expires;
      return (rewrites > 0); /* done, no rewrite needed */
    }

    cp = tor_strdup(escaped_safe_str(ent->new_address));
    log_info(LD_APP, "Addressmap: rewriting %s to %s",
             escaped_safe_str(address), cp);
    if (ent->expires > 1 && ent->expires < expires)
      expires = ent->expires;
    tor_free(cp);
    strlcpy(address, ent->new_address, maxlen);
  }
  log_warn(LD_CONFIG,
           "Loop detected: we've rewritten %s 16 times! Using it as-is.",
           escaped_safe_str(address));
  /* it's fine to rewrite a rewrite, but don't loop forever */
  if (expires_out)
    *expires_out = TIME_MAX;
  return 1;
}

/** If we have a cached reverse DNS entry for the address stored in the
 * <b>maxlen</b>-byte buffer <b>address</b> (typically, a dotted quad) then
 * rewrite to the cached value and return 1.  Otherwise return 0.  Set
 * *<b>expires_out</b> to the expiry time of the result, or to <b>time_max</b>
 * if the result does not expire. */
static int
addressmap_rewrite_reverse(char *address, size_t maxlen, time_t *expires_out)
{
  size_t len = maxlen + 16;
  char *s = tor_malloc(len), *cp;
  addressmap_entry_t *ent;
  int r = 0;
  tor_snprintf(s, len, "REVERSE[%s]", address);
  ent = strmap_get(addressmap, s);
  if (ent) {
    cp = tor_strdup(escaped_safe_str(ent->new_address));
    log_info(LD_APP, "Rewrote reverse lookup %s -> %s",
             escaped_safe_str(s), cp);
    tor_free(cp);
    strlcpy(address, ent->new_address, maxlen);
    r = 1;
  }

  if (expires_out)
    *expires_out = (ent && ent->expires > 1) ? ent->expires : TIME_MAX;

  tor_free(s);
  return r;
}

/** Return 1 if <b>address</b> is already registered, else return 0. If address
 * is already registered, and <b>update_expires</b> is non-zero, then update
 * the expiry time on the mapping with update_expires if it is a
 * mapping created by TrackHostExits. */
int
addressmap_have_mapping(const char *address, int update_expiry)
{
  addressmap_entry_t *ent;
  if (!(ent=strmap_get_lc(addressmap, address)))
    return 0;
  if (update_expiry && ent->source==ADDRMAPSRC_TRACKEXIT)
    ent->expires=time(NULL) + update_expiry;
  return 1;
}

/** Register a request to map <b>address</b> to <b>new_address</b>,
 * which will expire on <b>expires</b> (or 0 if never expires from
 * config file, 1 if never expires from controller, 2 if never expires
 * (virtual address mapping) from the controller.)
 *
 * <b>new_address</b> should be a newly dup'ed string, which we'll use or
 * free as appropriate. We will leave address alone.
 *
 * If <b>new_address</b> is NULL, or equal to <b>address</b>, remove
 * any mappings that exist from <b>address</b>.
 */
void
addressmap_register(const char *address, char *new_address, time_t expires,
                    addressmap_entry_source_t source)
{
  addressmap_entry_t *ent;

  ent = strmap_get(addressmap, address);