Never queue a cell on a marked circuit

changes/bug1184

@@ -4,4 +4,6 @@
       it may have been possible for a few queued cells to get relayed,
       even though they would have been immediately dropped by the next
       OR in the circuit.  Fix 1184; bugfix on 0.2.0.1-alpha.
+    - Never queue a cell for a circuit that's already been marked
+      for close.
 

src/or/relay.c

@@ -2272,6 +2272,9 @@ append_cell_to_circuit_queue(circuit_t *circ, or_connection_t *orconn,
 {
   cell_queue_t *queue;
   int streams_blocked;
+  if (circ->marked_for_close)
+    return;
+
   if (direction == CELL_DIRECTION_OUT) {
     queue = &circ->n_conn_cells;
     streams_blocked = circ->streams_blocked_on_n_conn;