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What should be done when detecting faulty frames?

asked 2019-01-24 11:01:03 +0000

MaxiKoh95 gravatar image

Hey Guys, Should I issue a message and if so, how? The current solution used is:

return 0;

But the frame falsely looks good.

Thanks a lot!

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answered 2019-01-24 19:54:36 +0000

JeffMorriss gravatar image

I assume you mean that you've decided that the frame in question isn't really your protocol?

In that case, yes, you should return 0. An example from README.dissector:

static int
dissect_dnp3_tcp(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data)
{
    if (!check_dnp3_header(tvb, FALSE)) {
        return 0;

Note that you should return 0 before adding anything to the protocol tree or modifying any columns.

If, on the other hand, you're in the middle of dissecting a frame when you realize something's wrong then generally you'd want to add an expert info indicating that/why you're giving up dissection.

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Thank you so much, I didn't know the difference until now.

MaxiKoh95 gravatar imageMaxiKoh95 ( 2019-01-25 06:56:46 +0000 )edit

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Asked: 2019-01-24 11:01:03 +0000

Seen: 49 times

Last updated: Jan 24