Add a mostly disabled feature to debug restarting in-process

For 23847, we want Tor to be able to shut down and then restart in
the same process.  Here's a patch to make the Tor binary do that.
To test it, you need to build with --enable-restart-debugging, and
then you need to set the environment variable TOR_DEBUG_RESTART.
With this option, Tor will then run for 5 seconds, then restart
itself in-process without exiting.  This only happens once.

You can change the 5-second interval using
TOR_DEBUG_RESTART_AFTER_SECONDS.

Implements ticket 24583.

1 files changed, 15 insertions, 1 deletions

diff --git a/src/or/tor_main.c b/src/or/tor_main.c
index c203d8248f..703669ac99 100644
--- a/src/or/tor_main.c
+++ b/src/or/tor_main.c
@@ -3,6 +3,11 @@
  * Copyright (c) 2007-2017, The Tor Project, Inc. */
 /* See LICENSE for licensing information */
 
+#include "orconfig.h"
+#ifdef ENABLE_RESTART_DEBUGGING
+#include <stdlib.h>
+#endif
+
 /**
  * \file tor_main.c
  * \brief Stub module containing a main() function.
@@ -19,9 +24,18 @@ int tor_main(int argc, char *argv[]);
 int
 main(int argc, char *argv[])
 {
-  int r = tor_main(argc, argv);
+  int r;
+#ifdef ENABLE_RESTART_DEBUGGING
+  int restart_count = getenv("TOR_DEBUG_RESTART") ? 1 : 0;
+ again:
+#endif
+  r = tor_main(argc, argv);
   if (r < 0 || r > 255)
     return 1;
+#ifdef ENABLE_RESTART_DEBUGGING
+  else if (r == 0 && restart_count--)
+    goto again;
+#endif
   else
     return r;
 }