Ethereal-dev: Re: [Ethereal-dev] ASN.1 over SCTP

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From: Matthijs Melchior <[email protected]>
Date: Wed, 28 Jul 2004 00:03:52 +0200
Thomas Steffen wrote:


I am trying to use ethereal 0.10.5 for debugging a network application. We use a custom protocol (in ASN.1) over SCTP. It nearly works, but there are three outstanding issues:
1. I can't get ethereal to analyse the data sent over SCTP (beyond 
giving a hex dump). If I send the same date over TCP, I can use 
Decode-as->Transport and select ASN1. However, for an SCTP stream, the 
Transport tab is not show. I guess this is a simple issue, but I don't 
know where to look for it.
2. Is it possible to make ethereal recognise the ASN1 data automatically?

3. Is it possble to autodetect the PDU type? We have several different message types, and they are defined as separate ASN.1 types.
Any suggestion would be very much appreciated. If changes to the code 
are necessary, I should be able to do that, if someone could point me 
into the correct direction...
I have a new version of packet-asn1.c available that also allows the
use of sctp.

This modification, and support for multiple ports with ASN.1 messages,
have been sitting on my disk for some time now, waiting for more testing...
And this seems to be a good opportunity.

To answer your questions:
1) this is possible with the new packet-asn1.c
2) yes, please read the text in the beginning of packet-asn1.c.
   Just specify the port numbers used for your messages.
   Using the ASN.1 sources, you can use the SNACC ASN.1 compiler to
   build a 'type-table' that can be read by the ethereal asn1 plugin.
   That will than display your messages with appropriate annotations.
3) I presume there is only 1 top level PDU type that is a choice
   of all your different messages....  You have to specify that
   PDU type as well.

I'll see if I can compile it with the current ethereal version
and send you the diff by a separate message, If successful, I will
submit it for inclusion in ethereal.

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Matthijs Melchior                                       Maarssen  /\\
[email protected]                                  Netherlands _\_v
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