Introduce circpad free_all() function.

src/app/main/shutdown.c

@@ -139,6 +139,7 @@ tor_free_all(int postfork)
   dos_free_all();
   circuitmux_ewma_free_all();
   accounting_free_all();
+  circpad_free_all();
 
   if (!postfork) {
     config_free_all();

src/core/or/circuitpadding.c

@@ -37,6 +37,13 @@
  * When a padding machine reaches the END state, it gets wiped from the circuit
  * so that other padding machines can take over if needed (see
  * circpad_machine_spec_transitioned_to_end()).
+ *
+ ****************************
+ * General notes:
+ *
+ * All used machines should be heap allocated and placed into
+ * origin_padding_machines/relay_padding_machines so that they get correctly
+ * cleaned up by the circpad_free_all() function.
  **/
 
 #define CIRCUITPADDING_PRIVATE
@@ -2885,6 +2892,36 @@ circpad_handle_padding_negotiated(circuit_t *circ, cell_t *cell,
   return 0;
 }
 
+/** Free memory allocated by this machine spec. */
+STATIC void
+machine_spec_free_(circpad_machine_spec_t *m)
+{
+  if (!m) return;
+
+  tor_free(m->states);
+  tor_free(m);
+}
+
+/** Free all memory allocated by the circuitpadding subsystem. */
+void
+circpad_free_all(void)
+{
+  if (origin_padding_machines) {
+    SMARTLIST_FOREACH_BEGIN(origin_padding_machines,
+                            circpad_machine_spec_t *, m) {
+      machine_spec_free(m);
+    } SMARTLIST_FOREACH_END(m);
+    smartlist_free(origin_padding_machines);
+  }
+  if (relay_padding_machines) {
+    SMARTLIST_FOREACH_BEGIN(relay_padding_machines,
+                            circpad_machine_spec_t *, m) {
+      machine_spec_free(m);
+    } SMARTLIST_FOREACH_END(m);
+    smartlist_free(relay_padding_machines);
+  }
+}
+
 /* Serialization */
 // TODO: Should we use keyword=value here? Are there helpers for that?
 #if 0

src/core/or/circuitpadding.h

@@ -738,7 +738,13 @@ circpad_machine_spec_transition, (circpad_machine_runtime_t *mi,
 circpad_decision_t circpad_send_padding_cell_for_callback(
                                  circpad_machine_runtime_t *mi);
 
+void circpad_free_all(void);
+
 #ifdef CIRCUITPADDING_PRIVATE
+STATIC void  machine_spec_free_(circpad_machine_spec_t *m);
+#define machine_spec_free(chan) \
+  FREE_AND_NULL(circpad_machine_spec_t,machine_spec_free_, (m))
+
 STATIC circpad_delay_t
 circpad_machine_sample_delay(circpad_machine_runtime_t *mi);