Reduce sensitivity to system clock instability

and backtracks.


git-svn-id: http://svn.openvpn.net/projects/openvpn/branches/BETA21/openvpn@799 e7ae566f-a301-0410-adde-c780ea21d3b5

9 files changed, 119 insertions, 11 deletions

diff --git a/init.c b/init.c
index 0c9a509..53d1851 100644
--- a/init.c
+++ b/init.c
@@ -2160,9 +2160,11 @@ do_setup_fast_io (struct context *c)
 	msg (M_INFO, "NOTE: --fast-io is disabled since we are not using UDP");
       else
 	{
+#ifdef HAVE_GETTIMEOFDAY
 	  if (c->options.shaper)
 	    msg (M_INFO, "NOTE: --fast-io is disabled since we are using --shaper");
 	  else
+#endif
 	    {
 	      c->c2.fast_io = true;
 	    }
diff --git a/interval.h b/interval.h
index 9845066..f56ed4d 100644
--- a/interval.h
+++ b/interval.h
@@ -213,13 +213,13 @@ static inline void
 usec_timer_start (struct usec_timer *obj)
 {
   CLEAR (*obj);
-  gettimeofday (&obj->start, NULL);
+  openvpn_gettimeofday (&obj->start, NULL);
 }
 
 static inline void
 usec_timer_end (struct usec_timer *obj)
 {
-  gettimeofday (&obj->end, NULL);
+  openvpn_gettimeofday (&obj->end, NULL);
 }
 
 #endif /* HAVE_GETTIMEOFDAY */
diff --git a/multi.c b/multi.c
index f72d73b..f0b630b 100644
--- a/multi.c
+++ b/multi.c
@@ -1667,7 +1667,7 @@ multi_process_post (struct multi_context *m, struct multi_instance *mi, const un
       if (!IS_SIG (&mi->context))
 	{
 	  /* calculate an absolute wakeup time */
-	  ASSERT (!gettimeofday (&mi->wakeup, NULL));
+	  ASSERT (!openvpn_gettimeofday (&mi->wakeup, NULL));
 	  tv_add (&mi->wakeup, &mi->context.c2.timeval);
 
 	  /* tell scheduler to wake us up at some point in the future */
diff --git a/multi.h b/multi.h
index da1e471..c796c23 100644
--- a/multi.h
+++ b/multi.h
@@ -376,7 +376,7 @@ multi_get_timeout (struct multi_context *m, struct timeval *dest)
   m->earliest_wakeup = (struct multi_instance *) schedule_get_earliest_wakeup (m->schedule, &tv);
   if (m->earliest_wakeup)
     {
-      ASSERT (!gettimeofday (&current, NULL));
+      ASSERT (!openvpn_gettimeofday (&current, NULL));
       tv_delta (dest, &current, &tv);
       if (dest->tv_sec >= REAP_MAX_WAKEUP)
 	{
diff --git a/otime.c b/otime.c
index ad9cbbf..fbef02d 100644
--- a/otime.c
+++ b/otime.c
@@ -34,7 +34,54 @@
 
 #include "memdbg.h"
 
-volatile time_t now; /* GLOBAL */
+time_t now = 0;            /* GLOBAL */
+
+#if TIME_BACKTRACK_PROTECTION
+
+static time_t now_adj = 0; /* GLOBAL */
+
+/*
+ * Try to filter out time instability caused by the system
+ * clock backtracking or jumping forward.
+ */
+
+void
+update_now (const time_t system_time)
+{
+  const int threshold = 86400; /* threshold at which to dampen forward jumps */
+  time_t real_time = system_time + now_adj;
+  if (real_time > now)
+    {
+      const time_t overshoot = real_time - now - 1;
+      if (overshoot > threshold && now_adj >= overshoot)
+        {
+          now_adj -= overshoot;
+          real_time -= overshoot;
+        }
+      now = real_time;
+    }
+  else if (real_time < now)
+    {
+      now_adj += (now - real_time);
+    }
+}
+
+#ifdef HAVE_GETTIMEOFDAY
+
+time_t now_usec = 0;       /* GLOBAL */
+
+void
+update_now_usec (struct timeval *tv)
+{
+  const time_t last = now;
+  update_now (tv->tv_sec);
+  if (now > last || tv->tv_usec > now_usec)
+    now_usec = tv->tv_usec;
+}
+
+#endif
+
+#endif
 
 /* 
  * Return a numerical string describing a struct timeval.
diff --git a/otime.h b/otime.h
index 974d0af..6744c4d 100644
--- a/otime.h
+++ b/otime.h
@@ -54,7 +54,39 @@ const char* time_string (time_t t, int usec, bool show_usec, struct gc_arena *gc
 const char *tv_string (const struct timeval *tv, struct gc_arena *gc);
 const char *tv_string_abs (const struct timeval *tv, struct gc_arena *gc);
 
-extern volatile time_t now; /* updated frequently to time(NULL) */
+extern time_t now; /* updated frequently to time(NULL) */
+
+#if TIME_BACKTRACK_PROTECTION
+
+void update_now (const time_t system_time);
+
+static inline void
+update_time (void)
+{
+  update_now (time (NULL));
+}
+
+#ifdef HAVE_GETTIMEOFDAY
+
+extern time_t now_usec;
+void update_now_usec (struct timeval *tv);
+
+static inline int
+openvpn_gettimeofday (struct timeval *tv, void *tz)
+{
+  const int status = gettimeofday (tv, tz);
+  if (!status)
+    {
+      update_now_usec (tv);
+      tv->tv_sec = now;
+      tv->tv_usec = now_usec;
+    }
+  return status;
+}
+
+#endif
+
+#else
 
 static inline void
 update_time (void)
@@ -64,6 +96,27 @@ update_time (void)
     now = real_time;
 }
 
+#ifdef HAVE_GETTIMEOFDAY
+
+static inline int
+openvpn_gettimeofday (struct timeval *tv, void *tz)
+{
+  return gettimeofday (tv, tz);
+}
+
+#endif
+
+#endif
+
+static inline time_t
+openvpn_time (time_t *t)
+{
+  update_time ();
+  if (t)
+    *t = now;
+  return now;
+}
+
 static inline void
 tv_clear (struct timeval *tv)
 {
diff --git a/pkcs11-helper.c b/pkcs11-helper.c
index 9eb074e..181c31f 100644
--- a/pkcs11-helper.c
+++ b/pkcs11-helper.c
@@ -870,7 +870,7 @@ _pkcs11h_getSession (
 				}
 				else {
 					(*session)->timePINExpire = (
-						time (NULL) +
+						openvpn_time (NULL) +
 						(time_t)nPINCachePeriod
 					);
 					(*session)->nPINCachePeriod = nPINCachePeriod;
@@ -1095,7 +1095,7 @@ _pkcs11h_validateSession (
 
 	if (
 		session->timePINExpire != (time_t)0 &&
-		session->timePINExpire < time (NULL)
+		session->timePINExpire < openvpn_time (NULL)
 	) {
 		_pkcs11h_logout (session);
 	}
@@ -1195,7 +1195,7 @@ _pkcs11h_login (
 				}
 				else {
 					session->timePINExpire = (
-						time (NULL) +
+						openvpn_time (NULL) +
 						(time_t)session->nPINCachePeriod
 					);
 				}
diff --git a/shaper.h b/shaper.h
index 3aba241..975e825 100644
--- a/shaper.h
+++ b/shaper.h
@@ -109,7 +109,7 @@ shaper_delay (struct shaper* s)
 
   if (tv_defined (&s->wakeup))
     {
-      ASSERT (!gettimeofday (&tv, NULL));
+      ASSERT (!openvpn_gettimeofday (&tv, NULL));
       delay = tv_subtract (&s->wakeup, &tv, SHAPER_MAX_TIMEOUT);
 #ifdef SHAPER_DEBUG
       dmsg (D_SHAPER_DEBUG, "SHAPER shaper_delay delay=%d", delay);
@@ -143,7 +143,7 @@ shaper_wrote_bytes (struct shaper* s, int nbytes)
 
   if (tv.tv_usec)
     {
-      ASSERT (!gettimeofday (&s->wakeup, NULL));
+      ASSERT (!openvpn_gettimeofday (&s->wakeup, NULL));
       tv_add (&s->wakeup, &tv);
 
 #ifdef SHAPER_DEBUG
diff --git a/syshead.h b/syshead.h
index 4c79286..9737a4b 100644
--- a/syshead.h
+++ b/syshead.h
@@ -472,4 +472,10 @@ socket_defined (const socket_descriptor_t sd)
  */
 #define ENABLE_INLINE_FILES 1
 
+/*
+ * Reduce sensitivity to system clock instability
+ * and backtracks.
+ */
+#define TIME_BACKTRACK_PROTECTION 1
+
 #endif