relay.c

关于tor匿名通信的源代码

    log_debug(domain,"yes, at-origin. stopped.");
    for (conn = TO_ORIGIN_CIRCUIT(circ)->p_streams; conn;
         conn=conn->next_stream)
      if (conn->cpath_layer == layer_hint)
        connection_stop_reading(TO_CONN(conn));
    return 1;
  }
  return 0;
}

/** Check if the deliver_window for circuit <b>circ</b> (at hop
 * <b>layer_hint</b> if it's defined) is low enough that we should
 * send a circuit-level sendme back down the circuit. If so, send
 * enough sendmes that the window would be overfull if we sent any
 * more.
 */
static void
circuit_consider_sending_sendme(circuit_t *circ, crypt_path_t *layer_hint)
{
//  log_fn(LOG_INFO,"Considering: layer_hint is %s",
//         layer_hint ? "defined" : "null");
  while ((layer_hint ? layer_hint->deliver_window : circ->deliver_window) <
          CIRCWINDOW_START - CIRCWINDOW_INCREMENT) {
    log_debug(LD_CIRC,"Queueing circuit sendme.");
    if (layer_hint)
      layer_hint->deliver_window += CIRCWINDOW_INCREMENT;
    else
      circ->deliver_window += CIRCWINDOW_INCREMENT;
    if (relay_send_command_from_edge(0, circ, RELAY_COMMAND_SENDME,
                                     NULL, 0, layer_hint) < 0) {
      log_warn(LD_CIRC,
               "relay_send_command_from_edge failed. Circuit's closed.");
      return; /* the circuit's closed, don't continue */
    }
  }
}

/** Stop reading on edge connections when we have this many cells
 * waiting on the appropriate queue. */
#define CELL_QUEUE_HIGHWATER_SIZE 256
/** Start reading from edge connections again when we get down to this many
 * cells. */
#define CELL_QUEUE_LOWWATER_SIZE 64

#ifdef ACTIVE_CIRCUITS_PARANOIA
#define assert_active_circuits_ok_paranoid(conn) \
     assert_active_circuits_ok(conn)
#else
#define assert_active_circuits_ok_paranoid(conn)
#endif

/** The total number of cells we have allocated from the memory pool. */
static int total_cells_allocated = 0;

#ifdef ENABLE_CELL_POOL /* Defined in ./configure. True by default. */
/* XXX021 make cell pools the only option once we know they work and improve
 * matters? -RD */
static mp_pool_t *cell_pool = NULL;
/** Allocate structures to hold cells. */
void
init_cell_pool(void)
{
  tor_assert(!cell_pool);
  cell_pool = mp_pool_new(sizeof(packed_cell_t), 128*1024);
}

/** Free all storage used to hold cells. */
void
free_cell_pool(void)
{
  /* Maybe we haven't called init_cell_pool yet; need to check for it. */
  if (cell_pool) {
    mp_pool_destroy(cell_pool);
    cell_pool = NULL;
  }
}

/** Free excess storage in cell pool. */
void
clean_cell_pool(void)
{
  tor_assert(cell_pool);
  mp_pool_clean(cell_pool, 0, 1);
}

/** Release storage held by <b>cell</b>. */
static INLINE void
packed_cell_free(packed_cell_t *cell)
{
  --total_cells_allocated;
  mp_pool_release(cell);
}

/** Allocate and return a new packed_cell_t. */
static INLINE packed_cell_t *
packed_cell_alloc(void)
{
  ++total_cells_allocated;
  return mp_pool_get(cell_pool);
}
void
dump_cell_pool_usage(int severity)
{
  circuit_t *c;
  int n_circs = 0;
  int n_cells = 0;
  for (c = _circuit_get_global_list(); c; c = c->next) {
    n_cells += c->n_conn_cells.n;
    if (!CIRCUIT_IS_ORIGIN(c))
      n_cells += TO_OR_CIRCUIT(c)->p_conn_cells.n;
    ++n_circs;
  }
  log(severity, LD_MM, "%d cells allocated on %d circuits. %d cells leaked.",
      n_cells, n_circs, total_cells_allocated - n_cells);
  mp_pool_log_status(cell_pool, severity);
}
#else
/* ENABLE_CELL_POOL isn't defined: here are some stubs to use tor_malloc()
 * and tor_free() instead. */
void
init_cell_pool(void)
{
}

void
free_cell_pool(void)
{
}

void
clean_cell_pool(void)
{
}

static INLINE void
packed_cell_free(packed_cell_t *cell)
{
  --total_cells_allocated;
  tor_free(cell);
}

static INLINE packed_cell_t *
packed_cell_alloc(void)
{
  ++total_cells_allocated;
  return tor_malloc(sizeof(packed_cell_t));
}
void
dump_cell_pool_usage(int severity)
{
  (void) severity;
}
#endif

/** Allocate a new copy of packed <b>cell</b>. */
static INLINE packed_cell_t *
packed_cell_copy(const cell_t *cell)
{
  packed_cell_t *c = packed_cell_alloc();
  cell_pack(c, cell);
  c->next = NULL;
  return c;
}

/** Append <b>cell</b> to the end of <b>queue</b>. */
void
cell_queue_append(cell_queue_t *queue, packed_cell_t *cell)
{
  if (queue->tail) {
    tor_assert(!queue->tail->next);
    queue->tail->next = cell;
  } else {
    queue->head = cell;
  }
  queue->tail = cell;
  cell->next = NULL;
  ++queue->n;
}

/** Append a newly allocated copy of <b>cell</b> to the end of <b>queue</b> */
void
cell_queue_append_packed_copy(cell_queue_t *queue, const cell_t *cell)
{
  cell_queue_append(queue, packed_cell_copy(cell));
}

/** Remove and free every cell in <b>queue</b>. */
void
cell_queue_clear(cell_queue_t *queue)
{
  packed_cell_t *cell, *next;
  cell = queue->head;
  while (cell) {
    next = cell->next;
    packed_cell_free(cell);
    cell = next;
  }
  queue->head = queue->tail = NULL;
  queue->n = 0;
}

/** Extract and return the cell at the head of <b>queue</b>; return NULL if
 * <b>queue</b> is empty. */
static INLINE packed_cell_t *
cell_queue_pop(cell_queue_t *queue)
{
  packed_cell_t *cell = queue->head;
  if (!cell)
    return NULL;
  queue->head = cell->next;
  if (cell == queue->tail) {
    tor_assert(!queue->head);
    queue->tail = NULL;
  }
  --queue->n;
  return cell;
}

/** Return a pointer to the "next_active_on_{n,p}_conn" pointer of <b>circ</b>,
 * depending on whether <b>conn</b> matches n_conn or p_conn. */
static INLINE circuit_t **
next_circ_on_conn_p(circuit_t *circ, or_connection_t *conn)
{
  tor_assert(circ);
  tor_assert(conn);
  if (conn == circ->n_conn) {
    return &circ->next_active_on_n_conn;
  } else {
    or_circuit_t *orcirc = TO_OR_CIRCUIT(circ);
    tor_assert(conn == orcirc->p_conn);
    return &orcirc->next_active_on_p_conn;
  }
}

/** Return a pointer to the "prev_active_on_{n,p}_conn" pointer of <b>circ</b>,
 * depending on whether <b>conn</b> matches n_conn or p_conn. */
static INLINE circuit_t **
prev_circ_on_conn_p(circuit_t *circ, or_connection_t *conn)
{
  tor_assert(circ);
  tor_assert(conn);
  if (conn == circ->n_conn) {
    return &circ->prev_active_on_n_conn;
  } else {
    or_circuit_t *orcirc = TO_OR_CIRCUIT(circ);
    tor_assert(conn == orcirc->p_conn);
    return &orcirc->prev_active_on_p_conn;
  }
}

/** Add <b>circ</b> to the list of circuits with pending cells on
 * <b>conn</b>.  No effect if <b>circ</b> is already unlinked. */
void
make_circuit_active_on_conn(circuit_t *circ, or_connection_t *conn)
{
  circuit_t **nextp = next_circ_on_conn_p(circ, conn);
  circuit_t **prevp = prev_circ_on_conn_p(circ, conn);

  if (*nextp && *prevp) {
    /* Already active. */
    return;
  }

  if (! conn->active_circuits) {
    conn->active_circuits = circ;
    *prevp = *nextp = circ;
  } else {
    circuit_t *head = conn->active_circuits;
    circuit_t *old_tail = *prev_circ_on_conn_p(head, conn);
    *next_circ_on_conn_p(old_tail, conn) = circ;
    *nextp = head;
    *prev_circ_on_conn_p(head, conn) = circ;
    *prevp = old_tail;
  }
  assert_active_circuits_ok_paranoid(conn);
}

/** Remove <b>circ</b> to the list of circuits with pending cells on
 * <b>conn</b>.  No effect if <b>circ</b> is already unlinked. */
void
make_circuit_inactive_on_conn(circuit_t *circ, or_connection_t *conn)
{
  circuit_t **nextp = next_circ_on_conn_p(circ, conn);
  circuit_t **prevp = prev_circ_on_conn_p(circ, conn);
  circuit_t *next = *nextp, *prev = *prevp;

  if (!next && !prev) {
    /* Already inactive. */
    return;
  }

  tor_assert(next && prev);
  tor_assert(*prev_circ_on_conn_p(next, conn) == circ);
  tor_assert(*next_circ_on_conn_p(prev, conn) == circ);

  if (next == circ) {
    conn->active_circuits = NULL;
  } else {
    *prev_circ_on_conn_p(next, conn) = prev;
    *next_circ_on_conn_p(prev, conn) = next;
    if (conn->active_circuits == circ)
      conn->active_circuits = next;
  }
  *prevp = *nextp = NULL;
  assert_active_circuits_ok_paranoid(conn);
}

/** Remove all circuits from the list of circuits with pending cells on
 * <b>conn</b>. */
void
connection_or_unlink_all_active_circs(or_connection_t *orconn)
{
  circuit_t *head = orconn->active_circuits;
  circuit_t *cur = head;
  if (! head)
    return;
  do {
    circuit_t *next = *next_circ_on_conn_p(cur, orconn);
    *prev_circ_on_conn_p(cur, orconn) = NULL;
    *next_circ_on_conn_p(cur, orconn) = NULL;
    cur = next;
  } while (cur != head);
  orconn->active_circuits = NULL;
}

/** Block (if <b>block</b> is true) or unblock (if <b>block</b> is false)
 * every edge connection that is using <b>circ</b> to write to <b>orconn</b>,
 * and start or stop reading as appropriate. */
static void
set_streams_blocked_on_circ(circuit_t *circ, or_connection_t *orconn,
                            int block)
{
  edge_connection_t *edge = NULL;
  if (circ->n_conn == orconn) {
    circ->streams_blocked_on_n_conn = block;
    if (CIRCUIT_IS_ORIGIN(circ))
      edge = TO_ORIGIN_CIRCUIT(circ)->p_streams;
  } else {
    circ->streams_blocked_on_p_conn = block;
    tor_assert(!CIRCUIT_IS_ORIGIN(circ));
    edge = TO_OR_CIRCUIT(circ)->n_streams;
  }

  for (; edge; edge = edge->next_stream) {
    connection_t *conn = TO_CONN(edge);
    conn->edge_blocked_on_circ = block;

    if (!conn->read_event) {
      /* This connection is a placeholder for something; probably a DNS
       * request.  It can't actually stop or start reading.*/
      continue;
    }

    if (block) {
      if (connection_is_reading(conn))
        connection_stop_reading(conn);
    } else {
      /* Is this right? */
      if (!connection_is_reading(conn))
        connection_start_reading(conn);
    }
  }
}

/** Pull as many cells as possible (but no more than <b>max</b>) from the
 * queue of the first active circuit on <b>conn</b>, and write then to
 * <b>conn</b>-&gt;outbuf.  Return the number of cells written.