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SubjectRe: Bug in IP accounting's output (2.0.30): a nibble is missing
Date
Hi,

> I have seen/reported/looked in the sources for the source of
> _exactly_the_same_problem_. In my case, I do IP accounting on every
> machine we have, and they all email me the data every night. When I used
> ipfwadm -lAz, I'd get occasional address bits dropped on some systems, and
> very frequent bits dropped on a virtual web server that (at the time)
> probably had around 50-60 virtuals with an output accounting rule for
> each. I think the last time I looked, I'd always get the corruption in
> just one address, and it was always the 10th rule, but I'd have to scan my
> files again to be certain.
>
> Your example is also in the 10th rule...cue the twilight zone music.
>
> The only solution I could come up with was what you did...-lA in pass one,
> and -Az in a second pass. Not quite optimal.

Someone else tested it with a Perl script, reading "raw" date from /proc
(opening the file in R/W mode, so that the counters are reset too) and
found exactly the same data corruption. We now know for sure that
the /proc file returns the wrong data (that is, a few bits are zeroed)
in some cases. We didn't find the solution yet, but this observation
makes it more easy to debug, I hope. At least we don't have to look at
the ipfwadm code anymore (that is, for this problem ;-)).

I'll look at it, but have very little time. If someone has more info
about this problem, has done some tracing, etc., please let me know!
I'll try to debug it using 2.0.30, as I also have to solve another
problem introduced in 2.0.30 (transparent proxying is broken...).

B.t.w., the corrupted data problem is there since long, probably forever.
I received the first problem report about this long ago, but I then
convinced that person that he probably had a memory hardware problem ;-).

--
-- Jos Vos <jos@xos.nl>
-- X/OS Experts in Open Systems BV | Phone: +31 20 6938364
-- Amsterdam, The Netherlands | Fax: +31 20 6948204
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