Ethereal-dev: [Ethereal-dev] Cisco SM and isup patches

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From: Cvetan Ivanov <zezo@xxxxxxxxx>
Date: Sat, 02 Apr 2005 21:02:45 +0300
Hello,

I got chance to do some SS7 traces with ethereal recently, and I must say I'm amazed of the functionality. Great work.
There are few minor issues that don't really decrease the usability but 
generate a big amount of packets, tagged as malformed, so I've written 
two small patches to the cisco SM and iusp dissectors to fix that.
I'm new to the list and to the ethereal code itserlf, so please take a 
good look at those, and excuse me if I've done some terribly wrong.
The SM poblem is that:
1) not all SM frames are PDU
2) not all PDU frames are MTP3

Non-pdu frames are shorter than PDU(message type 0x8000) so the decode fails in the SM dissector
Then part of the PDU frames seem to be mtp2-mtp3 management - like 
acttivate/deactivate link
So I've added checks for PDU message types, and then for the messages 
types that contain MTP3. This reduces the clutter and allows for proper 
mtp3 filtering
I may be able to produce some traces+cisco debug traces at later time, 
becaues we use the AS5350 integrated SLT feature, and that's got enough 
CPU power to do debugging on production system, but I'm quite busy with 
the SS7 itself right now.
The isup patch concerns a case where Connected line information is 
requested, and the softswitch returns the information element with 
indication that the number is unavailable, and then the number part of 
the IE is missing. the current code does not expect that empty field and 
tags the message as malformed.
I suspect that this could happen with the calling party number too, and 
possibly even with the called party number in case of overlap signaling, 
but haven't checked what the ITU books say about that.
Best regards,

Cvetan