Trap possible overflow in usec values to netem

If user asks for large usec value it could overflow 32 bits.
Signed-off-by: Stephen Hemminger <shemminger@osdl.org>

tc/q_netem.c

@@ -111,6 +111,11 @@ static int get_ticks(__u32 *ticks, const char *str)
 	if(get_usecs(&t, str))
 		return -1;
 	
+	if (tc_core_usec2big(t)) {
+		fprintf(stderr, "Illegal %d usecs (too large)\n", t);
+		return -1;
+	}
+
 	*ticks = tc_core_usec2tick(t);
 	return 0;
 }

tc/tc_core.c

@@ -27,6 +27,15 @@ static __u32 t2us=1;
 static __u32 us2t=1;
 static double tick_in_usec = 1;
 
+int tc_core_usec2big(long usec)
+{
+	__u64 t = usec;
+
+	t *= tick_in_usec;
+	return (t >> 32) != 0;
+}
+
+
 long tc_core_usec2tick(long usec)
 {
 	return usec*tick_in_usec;

tc/tc_core.h

@@ -4,6 +4,7 @@
 #include <asm/types.h>
 #include <linux/pkt_sched.h>
 
+int  tc_core_usec2big(long usec);
 long tc_core_usec2tick(long usec);
 long tc_core_tick2usec(long tick);
 unsigned tc_calc_xmittime(unsigned rate, unsigned size);