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; }
