Thomas Graf wrote:
* Nicolas DICHTEL <426E06F1.9000105@xxxxxxxxx> 2005-04-26 11:16
I set CONFIG_NET_SCH_CLK_GETTIMEOFDAY in my kernel. The macro
PSCHED_TDIFF_SAFE calculates
the difference between two timestamps and uses the function
psched_tod_diff() to do this.
If the clock is readjusted (due to ntp for example), this function can
return a negative number
(if bound > 1000000) and then the flow is blocked by the kernel. Am I
right ?
do_gettimeofday takes care of ntp adjustments so we _should_ be safe,
however, it might be wise to enforce a range of 0..bound instead of
INT_MIN..bound because qdiscs like red are relying on this. Assuming
we have a delta of -4 seconds and return -4e6 red will horribly
crash when acccessing the array with idle_time>>cell_log.
You can have the same kind of problem with a ingress filter. I propose the
following patch to fix the range to 0..bound
[SCHED] Fix range in psched_tod_diff() to 0..bound
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@xxxxxxxxx>
diff -Nru linux-2.6-a/include/net/pkt_sched.h
linux-2.6-b/include/net/pkt_sched.h
--- linux-2.6-a/include/net/pkt_sched.h 2005-04-26 15:45:07.074124664 +0200
+++ linux-2.6-b/include/net/pkt_sched.h 2005-04-26 15:47:26.215971888 +0200
@@ -140,7 +140,7 @@
if (bound <= 1000000 || delta_sec > (0x7FFFFFFF/1000000)-1)
return bound;
delta = delta_sec * 1000000;
- if (delta > bound)
+ if (delta > bound || delta < 0)
delta = bound;
return delta;
}
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