From 6010876e561b4345e569ffd11eaec9ea52725817 Mon Sep 17 00:00:00 2001
From: Pavel Zhukov <pzhukov@redhat.com>
Date: Wed, 24 Jul 2019 17:15:55 +0200
Subject: [PATCH] Detect system time jumps

In case if system time was changed backward it's possible to have ip
address dropped by the kernel due to lifetime expirity. Try to detect
this situation using either monotonic time or saved timestamp and execute
go_reboot() procedure to request lease extention
---
 lib/isc/include/isc/result.h    |  3 ++-
 lib/isc/include/isc/util.h      |  3 +++
 lib/isc/result.c                |  2 ++
 lib/isc/unix/app.c              | 39 +++++++++++++++++++++++++++++----
 lib/isc/unix/include/isc/time.h | 20 +++++++++++++++++
 lib/isc/unix/time.c             | 22 +++++++++++++++++++
 6 files changed, 84 insertions(+), 5 deletions(-)

diff --git a/lib/isc/include/isc/result.h b/lib/isc/include/isc/result.h
index 0389efa..149cde5 100644
--- a/lib/isc/include/isc/result.h
+++ b/lib/isc/include/isc/result.h
@@ -89,7 +89,8 @@
 #define ISC_R_DISCFULL			67	/*%< disc full */
 #define ISC_R_DEFAULT			68	/*%< default */
 #define ISC_R_IPV4PREFIX		69	/*%< IPv4 prefix */
-#define ISC_R_NRESULTS 			70
+#define ISC_R_TIMESHIFTED               70      /*%< system time changed */
+#define ISC_R_NRESULTS 			71
 
 ISC_LANG_BEGINDECLS
 
diff --git a/lib/isc/include/isc/util.h b/lib/isc/include/isc/util.h
index 973c348..8160dd3 100644
--- a/lib/isc/include/isc/util.h
+++ b/lib/isc/include/isc/util.h
@@ -289,6 +289,9 @@ extern void mock_assert(const int result, const char* const expression,
  * Time
  */
 #define TIME_NOW(tp) 	RUNTIME_CHECK(isc_time_now((tp)) == ISC_R_SUCCESS)
+#ifdef CLOCK_BOOTTIME
+#define TIME_MONOTONIC(tp) 	RUNTIME_CHECK(isc_time_boottime((tp)) == ISC_R_SUCCESS)
+#endif
 
 /*%
  * Alignment
diff --git a/lib/isc/result.c b/lib/isc/result.c
index a9db132..7c04831 100644
--- a/lib/isc/result.c
+++ b/lib/isc/result.c
@@ -105,6 +105,7 @@ static const char *description[ISC_R_NRESULTS] = {
 	"disc full",				/*%< 67 */
 	"default",				/*%< 68 */
 	"IPv4 prefix",				/*%< 69 */
+        "time changed",                         /*%< 70 */
 };
 
 static const char *identifier[ISC_R_NRESULTS] = {
@@ -178,6 +179,7 @@ static const char *identifier[ISC_R_NRESULTS] = {
 	"ISC_R_DISCFULL",
 	"ISC_R_DEFAULT",
 	"ISC_R_IPV4PREFIX",
+        "ISC_R_TIMESHIFTED",
 };
 
 #define ISC_RESULT_RESULTSET			2
diff --git a/lib/isc/unix/app.c b/lib/isc/unix/app.c
index a6e9882..52eb3e0 100644
--- a/lib/isc/unix/app.c
+++ b/lib/isc/unix/app.c
@@ -442,15 +442,48 @@ isc__app_ctxonrun(isc_appctx_t *ctx0, isc_mem_t *mctx, isc_task_t *task,
 static isc_result_t
 evloop(isc__appctx_t *ctx) {
 	isc_result_t result;
+        isc_time_t now;
+#ifdef CLOCK_BOOTTIME
+        isc_time_t monotonic;
+        uint64_t diff  = 0;
+#else
+        isc_time_t prev;
+        TIME_NOW(&prev);
+#endif
+
+
 
 	while (!ctx->want_shutdown) {
 		int n;
-		isc_time_t when, now;
+		isc_time_t when;
 		struct timeval tv, *tvp;
 		isc_socketwait_t *swait;
 		bool readytasks;
 		bool call_timer_dispatch = false;
-
+                uint64_t us;
+
+#ifdef CLOCK_BOOTTIME
+                // TBD macros for following three lines
+                TIME_NOW(&now);
+                TIME_MONOTONIC(&monotonic);
+                INSIST(now.seconds > monotonic.seconds)
+                us = isc_time_microdiff (&now, &monotonic);
+                if (us < diff){
+                  us = diff - us;
+                  if (us > 1000000){ // ignoring shifts less than one second
+                    return ISC_R_TIMESHIFTED;
+                  };
+                  diff = isc_time_microdiff (&now, &monotonic);
+                } else {
+                  diff = isc_time_microdiff (&now, &monotonic);
+                  // not implemented
+                }
+#else
+                TIME_NOW(&now);
+                if (isc_time_compare (&now, &prev) < 0)
+                  return ISC_R_TIMESHIFTED;
+                TIME_NOW(&prev);
+#endif
 		/*
 		 * Check the reload (or suspend) case first for exiting the
 		 * loop as fast as possible in case:
@@ -475,8 +508,6 @@ evloop(isc__appctx_t *ctx) {
 			if (result != ISC_R_SUCCESS)
 				tvp = NULL;
 			else {
-				uint64_t us;
-
 				TIME_NOW(&now);
 				us = isc_time_microdiff(&when, &now);
 				if (us == 0)
diff --git a/lib/isc/unix/include/isc/time.h b/lib/isc/unix/include/isc/time.h
index b864c29..5dd43c9 100644
--- a/lib/isc/unix/include/isc/time.h
+++ b/lib/isc/unix/include/isc/time.h
@@ -132,6 +132,26 @@ isc_time_isepoch(const isc_time_t *t);
  *\li	't' is a valid pointer.
  */
 
+#ifdef CLOCK_BOOTTIME
+isc_result_t
+isc_time_boottime(isc_time_t *t);
+/*%<
+ * Set 't' to monotonic time from previous boot
+ * it's not affected by system time change. It also
+ * includes the time system was suspended
+ *
+ * Requires:
+ *\li	't' is a valid pointer.
+ *
+ * Returns:
+ *
+ *\li	Success
+ *\li	Unexpected error
+ *		Getting the time from the system failed.
+ */
+#endif /* CLOCK_BOOTTIME */
+ 
+
 isc_result_t
 isc_time_now(isc_time_t *t);
 /*%<
diff --git a/lib/isc/unix/time.c b/lib/isc/unix/time.c
index 8edc9df..fe0bb91 100644
--- a/lib/isc/unix/time.c
+++ b/lib/isc/unix/time.c
@@ -498,3 +498,25 @@ isc_time_formatISO8601ms(const isc_time_t *t, char *buf, unsigned int len) {
 			 t->nanoseconds / NS_PER_MS);
 	}
 }
+
+
+#ifdef CLOCK_BOOTTIME
+isc_result_t
+isc_time_boottime(isc_time_t *t) {
+  struct timespec ts;
+  
+  char strbuf[ISC_STRERRORSIZE];
+
+  if (clock_gettime (CLOCK_BOOTTIME, &ts) != 0){
+    isc__strerror(errno, strbuf, sizeof(strbuf));
+    UNEXPECTED_ERROR(__FILE__, __LINE__, "%s", strbuf);
+    return (ISC_R_UNEXPECTED);    
+  }
+
+  t->seconds = ts.tv_sec;
+  t->nanoseconds = ts.tv_nsec;
+
+  return (ISC_R_SUCCESS);
+  
+};
+#endif
-- 
2.20.1