[WLANware] pmacct

[Stefan Braun]

Hello Jan, hello list

Am Donnerstag, den 13.08.2009, 07:06 +0200 schrieb Jan Groenewald:
> Sometimes pmacct acts strangely.  I cannot repeat or isolate
> this, but it happens once or twice a month.
> 
> I have a single entry which will suddenly drop. I notice
> because I Know the top 5 entries. One dropped yesterday from 4G to
> 800M or so. It is not always 4G, it does not seem to be some kind 
> wrapping. I have looked in curr.pmacct, the numbers have in fact changed
> so it is not just a display problem.

Do you have any entry higher than 4GByte?

In the german thread
<http://thread.gmane.org/gmane.org.freifunk.wlanware/4823> Marco Tedaldi
reported counter overflows, the entries with higher amount than 4GByte
start from zero again.


In the answer I assumed a 32Bit counter in the Linux kernel. There was
no other opinion in this thread, so it must be true. ;-)


I can reproduce it on my Linux box (Ubuntu 8.04) by transfering data via
Netcat from the loopback interface to the loopback interface:

In first shell (regard the "RX bytes" and "TX bytes" values):
$ watch ifconfig lo

In second shell:
$ nc -l -p 9999 >/dev/null

In third shell:
$ nc -v -v localhost 9999 </dev/zero


> regards,
> Jan

Greetings,
Stefan Braun.