Merge branch 'bug1653'

changes/bug1653

@@ -0,0 +1,8 @@
+  o Major bugfixes:
+    - When the exit relay gets a circuit-level sendme cell, it started
+      reading on the exit streams, even if had 500 cells queued in our
+      circuit queue already, so our circuit queue just grew and grew
+      in some cases.  We fix this by not re-enabling reading on SENDME
+      while the cell queue is blocked.  Fixes bug 1653.  Bugfix on
+      0.2.0.1-alpha.  Detected by Mashael AlSabah.  Original patch by
+      "yetonetime".

changes/detect-full-queues

@@ -0,0 +1,8 @@
+  o Major bugfixes:
+    - Newly created streams were allowed to read cells onto circuits,
+      even if the circuit's cell queue was blocked and waiting to drain.
+      This created potential unfairness, as older streams would be
+      blocked, but newer streams would gladly fill the queue completely.
+      We add code to detect this situation and prevent any stream from
+      getting more than one free cell.  Bugfix on 0.2.0.1-alpha.
+      Possible partial fix for bug 1298.

src/or/circuitbuild.c

@@ -1752,7 +1752,7 @@ circuit_deliver_create_cell(circuit_t *circ, uint8_t cell_type,
   cell.circ_id = circ->n_circ_id;
 
   memcpy(cell.payload, payload, ONIONSKIN_CHALLENGE_LEN);
-  append_cell_to_circuit_queue(circ, circ->n_conn, &cell, CELL_DIRECTION_OUT);
+  append_cell_to_circuit_queue(circ, circ->n_conn, &cell, CELL_DIRECTION_OUT, 0);
 
   if (CIRCUIT_IS_ORIGIN(circ)) {
     /* mark it so it gets better rate limiting treatment. */
@@ -2329,7 +2329,7 @@ onionskin_answer(or_circuit_t *circ, uint8_t cell_type, const char *payload,
   circ->is_first_hop = (cell_type == CELL_CREATED_FAST);
 
   append_cell_to_circuit_queue(TO_CIRCUIT(circ),
-                               circ->p_conn, &cell, CELL_DIRECTION_IN);
+                               circ->p_conn, &cell, CELL_DIRECTION_IN, 0);
   log_debug(LD_CIRC,"Finished sending 'created' cell.");
 
   if (!is_local_addr(&circ->p_conn->_base.addr) &&

src/or/relay.c

@@ -52,6 +52,7 @@ circuit_resume_edge_reading_helper(edge_connection_t *conn,
                                    crypt_path_t *layer_hint);
 static int
 circuit_consider_stop_edge_reading(circuit_t *circ, crypt_path_t *layer_hint);
+static int circuit_queue_streams_are_blocked(circuit_t *circ);
 
 /** Cache the current hi-res time; the cache gets reset when libevent
  * calls us. */
@@ -268,7 +269,7 @@ circuit_receive_relay_cell(cell_t *cell, circuit_t *circ,
                                   * we might kill the circ before we relay
                                   * the cells. */
 
-  append_cell_to_circuit_queue(circ, or_conn, cell, cell_direction);
+  append_cell_to_circuit_queue(circ, or_conn, cell, cell_direction, 0);
   return 0;
 }
 
@@ -365,7 +366,7 @@ relay_crypt(circuit_t *circ, cell_t *cell, cell_direction_t cell_direction,
 static int
 circuit_package_relay_cell(cell_t *cell, circuit_t *circ,
                            cell_direction_t cell_direction,
-                           crypt_path_t *layer_hint)
+                           crypt_path_t *layer_hint, uint16_t on_stream)
 {
   or_connection_t *conn; /* where to send the cell */
 
@@ -409,7 +410,7 @@ circuit_package_relay_cell(cell_t *cell, circuit_t *circ,
   }
   ++stats_n_relay_cells_relayed;
 
-  append_cell_to_circuit_queue(circ, conn, cell, cell_direction);
+  append_cell_to_circuit_queue(circ, conn, cell, cell_direction, on_stream);
   return 0;
 }
 
@@ -624,8 +625,8 @@ relay_send_command_from_edge(uint16_t stream_id, circuit_t *circ,
     }
   }
 
-  if (circuit_package_relay_cell(&cell, circ, cell_direction, cpath_layer)
+  if (circuit_package_relay_cell(&cell, circ, cell_direction, cpath_layer,
-      < 0) {
+                                 stream_id) < 0) {
     log_warn(LD_BUG,"circuit_package_relay_cell failed. Closing.");
     circuit_mark_for_close(circ, END_CIRC_REASON_INTERNAL);
     return -1;
@@ -1236,6 +1237,10 @@ connection_edge_process_relay_cell(cell_t *cell, circuit_t *circ,
       conn->package_window += STREAMWINDOW_INCREMENT;
       log_debug(domain,"stream-level sendme, packagewindow now %d.",
                 conn->package_window);
+      if (circuit_queue_streams_are_blocked(circ)) {
+        /* Still waiting for queue to flush; don't touch conn */
+        return 0;
+      }
       connection_start_reading(TO_CONN(conn));
       /* handle whatever might still be on the inbuf */
       if (connection_edge_package_raw_inbuf(conn, 1) < 0) {
@@ -1436,7 +1441,10 @@ connection_edge_consider_sending_sendme(edge_connection_t *conn)
 static void
 circuit_resume_edge_reading(circuit_t *circ, crypt_path_t *layer_hint)
 {
-
+  if (circuit_queue_streams_are_blocked(circ)) {
+    log_debug(layer_hint?LD_APP:LD_EXIT,"Too big queue, no resuming");
+    return;
+  }
   log_debug(layer_hint?LD_APP:LD_EXIT,"resuming");
 
   if (CIRCUIT_IS_ORIGIN(circ))
@@ -2092,12 +2100,19 @@ connection_or_unlink_all_active_circs(or_connection_t *orconn)
 
 /** 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. */
+ * and start or stop reading as appropriate.
-static void
+ *
+ * If <b>stream_id</b> is nonzero, block only the edge connection whose
+ * stream_id matches it.
+ *
+ * Returns the number of streams whose status we changed.
+ */
+static int
 set_streams_blocked_on_circ(circuit_t *circ, or_connection_t *orconn,
-                            int block)
+                            int block, uint16_t stream_id)
 {
   edge_connection_t *edge = NULL;
+  int n = 0;
   if (circ->n_conn == orconn) {
     circ->streams_blocked_on_n_conn = block;
     if (CIRCUIT_IS_ORIGIN(circ))
@@ -2110,7 +2125,13 @@ set_streams_blocked_on_circ(circuit_t *circ, or_connection_t *orconn,
 
   for (; edge; edge = edge->next_stream) {
     connection_t *conn = TO_CONN(edge);
-    edge->edge_blocked_on_circ = block;
+    if (stream_id && edge->stream_id != stream_id)
+      continue;
+
+    if (edge->edge_blocked_on_circ != block) {
+      ++n;
+      edge->edge_blocked_on_circ = block;
+    }
 
     if (!conn->read_event) {
       /* This connection is a placeholder for something; probably a DNS
@@ -2127,6 +2148,8 @@ set_streams_blocked_on_circ(circuit_t *circ, or_connection_t *orconn,
         connection_start_reading(conn);
     }
   }
+
+  return n;
 }
 
 /** Pull as many cells as possible (but no more than <b>max</b>) from the
@@ -2252,7 +2275,7 @@ connection_or_flush_from_first_active_circuit(or_connection_t *conn, int max,
   /* Is the cell queue low enough to unblock all the streams that are waiting
    * to write to this circuit? */
   if (streams_blocked && queue->n <= CELL_QUEUE_LOWWATER_SIZE)
-    set_streams_blocked_on_circ(circ, conn, 0); /* unblock streams */
+    set_streams_blocked_on_circ(circ, conn, 0, 0); /* unblock streams */
 
   /* Did we just run out of cells on this circuit's queue? */
   if (queue->n == 0) {
@@ -2269,7 +2292,8 @@ connection_or_flush_from_first_active_circuit(or_connection_t *conn, int max,
  * transmitting in <b>direction</b>. */
 void
 append_cell_to_circuit_queue(circuit_t *circ, or_connection_t *orconn,
-                             cell_t *cell, cell_direction_t direction)
+                             cell_t *cell, cell_direction_t direction,
+                             uint16_t fromstream)
 {
   cell_queue_t *queue;
   int streams_blocked;
@@ -2291,7 +2315,12 @@ append_cell_to_circuit_queue(circuit_t *circ, or_connection_t *orconn,
   /* If we have too many cells on the circuit, we should stop reading from
    * the edge streams for a while. */
   if (!streams_blocked && queue->n >= CELL_QUEUE_HIGHWATER_SIZE)
-    set_streams_blocked_on_circ(circ, orconn, 1); /* block streams */
+    set_streams_blocked_on_circ(circ, orconn, 1, 0); /* block streams */
+
+  if (streams_blocked && fromstream) {
+    /* This edge connection is apparently not blocked; block it. */
+    set_streams_blocked_on_circ(circ, orconn, 1, fromstream);
+  }
 
   if (queue->n == 1) {
     /* This was the first cell added to the queue.  We need to make this
@@ -2405,3 +2434,15 @@ assert_active_circuits_ok(or_connection_t *orconn)
   tor_assert(n == smartlist_len(orconn->active_circuit_pqueue));
 }
 
+/** Return 1 if we shouldn't restart reading on this circuit, even if
+ * we get a SENDME.  Else return 0.
+*/
+static int
+circuit_queue_streams_are_blocked(circuit_t *circ)
+{
+  if (CIRCUIT_IS_ORIGIN(circ)) {
+    return circ->streams_blocked_on_n_conn;
+  } else {
+    return circ->streams_blocked_on_p_conn;
+  }
+}

src/or/relay.h

@@ -45,7 +45,8 @@ void cell_queue_append(cell_queue_t *queue, packed_cell_t *cell);
 void cell_queue_append_packed_copy(cell_queue_t *queue, const cell_t *cell);
 
 void append_cell_to_circuit_queue(circuit_t *circ, or_connection_t *orconn,
-                                  cell_t *cell, cell_direction_t direction);
+                                  cell_t *cell, cell_direction_t direction,
+                                  uint16_t fromstream);
 void connection_or_unlink_all_active_circs(or_connection_t *conn);
 int connection_or_flush_from_first_active_circuit(or_connection_t *conn,
                                                   int max, time_t now);