Merge branches 'bug8185_031' and 'bug8185_diagnostic_032'

changes/8185_diagnostic

@@ -0,0 +1,4 @@
+  o Minor features (logging diagnostic):
+    - Log more circuit information whenever we are about to try to
+      package a relay cell on a circuit with a nonexistent n_chan.
+      Attempt to diagnose bug 8185.

changes/bug8185_025

@@ -0,0 +1,6 @@
+  o Minor bugfixes (logging, relay shutdown, annoyance):
+    - When a circuit is marked for close, do not attempt to package any cells
+      for channels on that circuit. Previously, we would detect this
+      condition lower in the call stack, when we noticed that the circuit had
+      no attached channel, and log an annoying message. Fixes bug 8185;
+      bugfix on 0.2.5.4-alpha.

src/or/relay.c

@@ -495,12 +495,25 @@ circuit_package_relay_cell(cell_t *cell, circuit_t *circ,
 {
   channel_t *chan; /* where to send the cell */
 
+  if (circ->marked_for_close) {
+    /* Circuit is marked; send nothing. */
+    return 0;
+  }
+
   if (cell_direction == CELL_DIRECTION_OUT) {
     crypt_path_t *thishop; /* counter for repeated crypts */
     chan = circ->n_chan;
     if (!chan) {
       log_warn(LD_BUG,"outgoing relay cell sent from %s:%d has n_chan==NULL."
-               " Dropping.", filename, lineno);
+               " Dropping. Circuit is in state %s (%d), and is "
+               "%smarked for close. (%s:%d, %d)", filename, lineno,
+               circuit_state_to_string(circ->state), circ->state,
+               circ->marked_for_close ? "" : "not ",
+               circ->marked_for_close_file?circ->marked_for_close_file:"",
+               circ->marked_for_close, circ->marked_for_close_reason);
+      if (CIRCUIT_IS_ORIGIN(circ)) {
+        circuit_log_path(LOG_WARN, LD_BUG, TO_ORIGIN_CIRCUIT(circ));
+      }
       log_backtrace(LOG_WARN,LD_BUG,"");
       return 0; /* just drop it */
     }
@@ -810,6 +823,12 @@ connection_edge_send_command(edge_connection_t *fromconn,
     return -1;
   }
 
+  if (circ->marked_for_close) {
+    /* The circuit has been marked, but not freed yet. When it's freed, it
+     * will mark this connection for close. */
+    return -1;
+  }
+
 #ifdef MEASUREMENTS_21206
   /* Keep track of the number of RELAY_DATA cells sent for directory
    * connections. */