[PATCH] replacing gettimeofday with clock_gettime in xenconsoled

[PATCH] replacing gettimeofday with clock_gettime in xenconsoled

[Stefano Stabellini]

Hi all,
currently if someone changes the date on the host, xenconsoled may behave
incorrectly due to the use of gettimeofday for the rate control algorithm.
For example I was able to hang the console connected to a guest just setting
the date forward 20 years.
To solve the problem we need to use a time source that doesn't change start
point, that is clock_gettime with CLOCK_MONOTONIC.
The only bad side effect is that it introduces a dependency to librt, but I
think is well worth it.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>

---

diff -r a538185695ed tools/console/Makefile
--- a/tools/console/Makefile	Tue Jul 29 15:10:58 2008 +0100
+++ b/tools/console/Makefile	Tue Jul 29 15:47:29 2008 +0100
@@ -21,7 +21,7 @@ clean:
 
 xenconsoled: $(patsubst %.c,%.o,$(wildcard daemon/*.c))
 	$(CC) $(CFLAGS) $^ -o $@ $(LDFLAGS) \
-              $(UTIL_LIBS) $(SOCKET_LIBS)
+              $(UTIL_LIBS) $(SOCKET_LIBS) -lrt
 
 xenconsole: $(patsubst %.c,%.o,$(wildcard client/*.c))
 	$(CC) $(CFLAGS) $^ -o $@ $(LDFLAGS) \
diff -r a538185695ed tools/console/daemon/io.c
--- a/tools/console/daemon/io.c	Tue Jul 29 15:10:58 2008 +0100
+++ b/tools/console/daemon/io.c	Tue Jul 29 15:44:59 2008 +0100
@@ -622,9 +622,9 @@ static struct domain *create_domain(int 
 {
 	struct domain *dom;
 	char *s;
-	struct timeval tv;
-
-	if (gettimeofday(&tv, NULL) < 0) {
+	struct timespec ts;
+
+	if (clock_gettime(CLOCK_MONOTONIC, &ts) < 0) {
 		dolog(LOG_ERR, "Cannot get time of day %s:%s:L%d",
 		      __FILE__, __FUNCTION__, __LINE__);
 		return NULL;
@@ -666,7 +666,7 @@ static struct domain *create_domain(int 
 	dom->buffer.capacity = 0;
 	dom->buffer.max_capacity = 0;
 	dom->event_count = 0;
-	dom->next_period = (tv.tv_sec * 1000) + (tv.tv_usec / 1000) + RATE_LIMIT_PERIOD;
+	dom->next_period = (ts.tv_sec * 1000) + (ts.tv_nsec / 1000000) + RATE_LIMIT_PERIOD;
 	dom->next = NULL;
 
 	dom->ring_ref = -1;
@@ -971,7 +971,7 @@ void handle_io(void)
 		struct domain *d, *n;
 		int max_fd = -1;
 		struct timeval timeout;
-		struct timeval tv;
+		struct timespec ts;
 		long long now, next_timeout = 0;
 
 		FD_ZERO(&readfds);
@@ -985,9 +985,9 @@ void handle_io(void)
 			max_fd = MAX(xc_evtchn_fd(xce_handle), max_fd);
 		}
 
-		if (gettimeofday(&tv, NULL) < 0)
+		if (clock_gettime(CLOCK_MONOTONIC, &ts) < 0)
 			return;
-		now = (tv.tv_sec * 1000) + (tv.tv_usec / 1000);
+		now = (ts.tv_sec * 1000) + (ts.tv_nsec / 1000000);
 
 		/* Re-calculate any event counter allowances & unblock
 		   domains with new allowance */