fix CLOCK_BOOTTIME use on kernels not having it

When the libc headers used to build mosquitto define CLOCK_BOOTTIME but the kernel where mosquitto runs does not implement CLOCK_BOOTTIME, all timestamps are wrong (uninitialized data), because there is no check for the success of the clock_gettime() calls. This adds probing for the availability of CLOCK_BOOTTIME from mosquitto_lib_init(), falling back to CLOCK_MONOTONIC, and then modifies mosquitto_time() to use the selected clock. Probing at init time avoids having to do two clock_gettime() calls for every timestamp if CLOCK_BOOTTIME is not available. It also fixes a similar problem in mosquitto_lib_init(). Signed-off-by: Diego Santa Cruz <[email protected]>
eclipse-mosquitto · Sep 6, 2024 · 688fa86 · 688fa86
1 parent a87b5ff
commit 688fa86
Show file tree

Hide file tree

Showing 3 changed files with 30 additions and 9 deletions.
diff --git a/lib/mosquitto.c b/lib/mosquitto.c
@@ -38,6 +38,7 @@ SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
 #include "mqtt_protocol.h"
 #include "net_mosq.h"
 #include "packet_mosq.h"
+#include "time_mosq.h"
 #include "will_mosq.h"
 
 static unsigned int init_refcount = 0;
@@ -57,15 +58,15 @@ int mosquitto_lib_init(void)
 	int rc;
 
 	if (init_refcount == 0) {
+		mosquitto_time_init();
 #ifdef WIN32
 		srand((unsigned int)GetTickCount64());
 #elif _POSIX_TIMERS>0 && defined(_POSIX_MONOTONIC_CLOCK)
 		struct timespec tp;
 #ifdef CLOCK_BOOTTIME
-		clock_gettime(CLOCK_BOOTTIME, &tp);
-#else
-		clock_gettime(CLOCK_MONOTONIC, &tp);
+		if (clock_gettime(CLOCK_BOOTTIME, &tp) != 0)
 #endif
+		clock_gettime(CLOCK_MONOTONIC, &tp);
 		srand((unsigned int)tp.tv_nsec);
 #elif defined(__APPLE__)
 		uint64_t ticks;

diff --git a/lib/time_mosq.c b/lib/time_mosq.c
@@ -36,19 +36,38 @@ SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
 #include "mosquitto.h"
 #include "time_mosq.h"
 
+#if _POSIX_TIMERS>0 && defined(_POSIX_MONOTONIC_CLOCK)
+static clockid_t time_clock;
+#endif
+
+void mosquitto_time_init(void)
+{
+#if _POSIX_TIMERS>0 && defined(_POSIX_MONOTONIC_CLOCK)
+	struct timespec tp;
+
+#ifdef CLOCK_BOOTTIME
+	if (clock_gettime(CLOCK_BOOTTIME, &tp) == 0) {
+		time_clock = CLOCK_BOOTTIME;
+	} else {
+		time_clock = CLOCK_MONOTONIC;
+	}
+#else
+	time_clock = CLOCK_MONOTONIC;
+#endif
+#endif
+}
+
 time_t mosquitto_time(void)
 {
 #ifdef WIN32
 	return GetTickCount64()/1000;
 #elif _POSIX_TIMERS>0 && defined(_POSIX_MONOTONIC_CLOCK)
 	struct timespec tp;
 
-#ifdef CLOCK_BOOTTIME
-	clock_gettime(CLOCK_BOOTTIME, &tp);
-#else
-	clock_gettime(CLOCK_MONOTONIC, &tp);
-#endif
-	return tp.tv_sec;
+	if (clock_gettime(time_clock, &tp) == 0)
+		return tp.tv_sec;
+
+	return (time_t) -1;
 #elif defined(__APPLE__)
 	static mach_timebase_info_data_t tb;
     uint64_t ticks;

diff --git a/lib/time_mosq.h b/lib/time_mosq.h
@@ -19,6 +19,7 @@ SPDX-License-Identifier: EPL-2.0 OR BSD-3-Clause
 #ifndef TIME_MOSQ_H
 #define TIME_MOSQ_H
 
+void mosquitto_time_init(void);
 time_t mosquitto_time(void);
 
 #endif