Initial heartbeat subsystem commit.

Sets:
* Documentation
* Logging domain
* Configuration option
* Scheduled event
* Makefile
It also creates status.c and the log_heartbeat() function.

All code was written by Sebastian Hahn. Commit message was
written by me (George Kadianakis).

doc/tor.1.txt

@@ -928,6 +928,10 @@ is non-zero):
     seconds, we exit. If we get a second SIGINT, we exit immedi-
     ately. (Default: 30 seconds)
 
+**HeartbeatPeriod**  __N__ **minutes**|**hours**|**days**|**weeks**::
+    Log a heartbeat message every **HeartbeatPeriod** seconds. This is
+    a log level __info__ message, designed to let you know your Tor
+    instance is still alive and doing useful things. (Default: 6 hours)
 
 **AccountingMax** __N__ **bytes**|**KB**|**MB**|**GB**|**TB**::
     Never send more than the specified number of bytes in a given accounting

src/common/torlog.h

@@ -92,8 +92,10 @@
 #define LD_HIST     (1u<<18)
 /** OR handshaking */
 #define LD_HANDSHAKE (1u<<19)
+/** Heartbeat messages */
+#define LD_HEARTBEAT (1u<<20)
 /** Number of logging domains in the code. */
-#define N_LOGGING_DOMAINS 20
+#define N_LOGGING_DOMAINS 21
 
 /** This log message is not safe to send to a callback-based logger
  * immediately.  Used as a flag, not a log domain. */

src/or/Makefile.am

@@ -52,7 +52,8 @@ libtor_a_SOURCES = \
 	routerparse.c				\
 	$(evdns_source)				\
 	$(tor_platform_source)			\
-	config_codedigest.c
+	config_codedigest.c             \
+	status.c
 
 #libtor_a_LIBADD = ../common/libor.a ../common/libor-crypto.a \
 #	../common/libor-event.a

src/or/config.c

@@ -267,6 +267,7 @@ static config_var_t _option_vars[] = {
 #endif
   OBSOLETE("Group"),
   V(HardwareAccel,               BOOL,     "0"),
+  V(HeartbeatPeriod,             INTERVAL, "6 hours"),
   V(AccelName,                   STRING,   NULL),
   V(AccelDir,                    FILENAME, NULL),
   V(HashedControlPassword,       LINELIST, NULL),
@@ -2915,6 +2916,10 @@ compute_publishserverdescriptor(or_options_t *options)
  * will generate too many circuits and potentially overload the network. */
 #define MIN_CIRCUIT_STREAM_TIMEOUT 10
 
+/** Lowest allowable value for HeartbeatPeriod; if this is too low, we might
+ * expose more information than we're comfortable with. */
+#define MIN_HEARTBEAT_PERIOD (30*60)
+
 /** Return 0 if every setting in <b>options</b> is reasonable, and a
  * permissible transition from <b>old_options</b>. Else return -1.
  * Should have no side effects, except for normalizing the contents of
@@ -3376,6 +3381,14 @@ options_validate(or_options_t *old_options, or_options_t *options,
              "raising to %d seconds.", MIN_CIRCUIT_STREAM_TIMEOUT);
     options->CircuitStreamTimeout = MIN_CIRCUIT_STREAM_TIMEOUT;
   }
+  
+  if (options->HeartbeatPeriod &&
+      options->HeartbeatPeriod < MIN_HEARTBEAT_PERIOD) {
+    log_warn(LD_CONFIG, "HeartbeatPeriod option is too short; "
+             "raising to %d seconds.", MIN_HEARTBEAT_PERIOD);
+    options->HeartbeatPeriod = MIN_HEARTBEAT_PERIOD;
+  }
+
 
   if (options->KeepalivePeriod < 1)
     REJECT("KeepalivePeriod option must be positive.");

src/or/main.c

@@ -1050,6 +1050,7 @@ run_scheduled_events(time_t now)
   static time_t time_to_check_port_forwarding = 0;
   static int should_init_bridge_stats = 1;
   static time_t time_to_retry_dns_init = 0;
+  static time_t time_last_written_heartbeat = 0;
   or_options_t *options = get_options();
   int is_server = server_mode(options);
   int i;
@@ -1440,6 +1441,12 @@ run_scheduled_events(time_t now)
                               now);
     time_to_check_port_forwarding = now+PORT_FORWARDING_CHECK_INTERVAL;
   }
+  
+  /** 11. write the heartbeat message */
+  if (options->HeartbeatPeriod &&
+      time_last_written_heartbeat + options->HeartbeatPeriod < now)
+    log_heartbeat(now);
+    time_last_written_heartbeat = now;
 }
 
 /** Timer: used to invoke second_elapsed_callback() once per second. */

src/or/or.h

@@ -2718,6 +2718,9 @@ typedef struct {
   config_line_t *HidServAuth; /**< List of configuration lines for client-side
                                * authorizations for hidden services */
   char *ContactInfo; /**< Contact info to be published in the directory. */
+  
+  int HeartbeatPeriod; /**< Log heartbeat messages after this many seconds
+                        * have passed. */
 
   char *HTTPProxy; /**< hostname[:port] to use as http proxy, if any. */
   tor_addr_t HTTPProxyAddr; /**< Parsed IPv4 addr for http proxy, if any. */

src/or/status.c

+/* Copyright (c) 2010, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file status.c
+ * \brief Keep status information and log the heartbeat messages.
+ **/
+
+#include "or.h"
+
+
+/****************************************************************************/
+
+
+
+#define BEAT(x) log_fn(LOG_NOTICE, LD_HEARTBEAT, (x) )
+
+void
+log_heartbeat(time_t now) {
+  or_options_t *opt = get_options();
+
+  (void) now;
+  log_fn(LOG_NOTICE, LD_HEARTBEAT, "This is the Tor heartbeat message.");
+  if (!server_mode(opt))
+    BEAT("you are a client, hahaha");
+
+}