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Re: [Wireshark-dev] Hi. regarding 'visited' bit
From: Ari Yoskovitz <ariyosko_at_nospam>Date: Thu May 20 2010 - 10:14:37 GMT
To: Developer support list for Wireshark <wireshark-dev@wireshark.org>
Hi. Thanks for your reply.
I removed my assignment to this bit, but now things act funny.
For example, i am using the re-assembling mechanism, including the hash
table.
I added DISSECTOR_ASSERTS for cases when the 'get' operation return a NULL.
This should never happen because I am inserting to the hash on the first
pass, using the 'visited' bit, and extracting from it on other passes
(visited != 0).
However, sometimes, not always, those asserts fails. If that's not odd
enough, saving to a file and re-loading it make the problems go away.
Maybe I don't really understand how the 'visited' bit works, or do I?
Thanks.
On Sun, May 16, 2010 at 7:16 PM, Jaap Keuter <jaap.keuter@xs4all.nl> wrote:
> On 05/16/2010 03:36 PM, Ari Yoskovitz wrote:
> > Hi.
> >
> > I am using the pinfo->fd->flags.visited bit in my dissector.
> > I have discovered (after a lot of debugging...) the sometimes this bit
> > is asserted even on the first run, namely when the packet was not
> visited...
> > It happens very rarely, but when it does the results are destructive.
> >
> > Am I missing anything? Is this a bug?
>
> This should never happen. If this is true, that's a bug.
> Now the question is, can you define the circumstances when this happens?
>
> > Thanks.
> >
> > BTW It looks to me that this bit has to be manually set to 1 when the
> > packet is being visited for the first time. Again, am I wrong here?
> Thanks.
> >
>
> This is *incorrect*
> The EPAN dissection engine handles setting of this bit after the frame was
> handed off to the frame dissector. See dissect_packet() in epan/packet.c.
> You're
> supposed to treat this as a readonly value. Maybe this is the cause for the
> bug
> you see?
>
> Thanks,
> Jaap
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-- Use the source, Luke!
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