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Wireshark-dev: Re: [Wireshark-dev] ASN.1 enumeration extension coding question

From: "Nichols, Roger" <Roger.Nichols@xxxxxxxxxxxx>
Date: Mon, 17 Dec 2007 15:25:08 -0500
Is anyone aware of an ITU specification using enumerated 
values not in the root besides T.38?  This code change is 
in a generic prototcol handler, and could have unintended 
consequences.  I am willing to believe I am wrong, I am 
just looking for an ITU document which clarifies whether 
the extended values should be encoded on a byte boundary.

--roger

-----Original Message-----
From: wireshark-dev-bounces@xxxxxxxxxxxxx [mailto:wireshark-dev-bounces@xxxxxxxxxxxxx] On Behalf Of Kukosa, Tomas
Sent: Monday, December 17, 2007 2:57 PM
To: Developer support list for Wireshark; Developer support list for Wireshark
Subject: Re: [Wireshark-dev] ASN.1 enumeration extension coding question

Hi,
 
it seems that it was implemented by me (rev 17530, March 2006) but I do not remember why.
 
I will fix it.
 
Tomas
 

________________________________

Od: wireshark-dev-bounces@xxxxxxxxxxxxx za uživatele Anders Broman
Odesláno: po 17.12.2007 20:36
Komu: 'Developer support list for Wireshark'
Předmět: Re: [Wireshark-dev] ASN.1 enumeration extension coding question



Hi,
After reading your previous post on the subject I did a quick check Of the ITU spec and it looks like you are right...I'm not sure why the Check is there - Tomas? Ronny?
Regards
Anders

-----Ursprungligt meddelande-----
Fran: wireshark-dev-bounces@xxxxxxxxxxxxx
[mailto:wireshark-dev-bounces@xxxxxxxxxxxxx] För Nichols, Roger
Skickat: den 17 december 2007 20:06
Till: wireshark-dev@xxxxxxxxxxxxx
Ämne: [Wireshark-dev] ASN.1 enumeration extension coding question


Hi,

Is this the proper forum to ask a question about 'why' something is coded the way it is?

We are developing a V.34 enabled T.38 end point, and are confused by the Wireshark decoding.  It seems the Wireshark decoder is aligning fields which are extension values.  For example, the 2002 T.38 ASN.1 notation for V.34 Data Field values.  We are not aligning these enumeration values, but Wireshark does.  See line 1211 of packet-per.c, a comment which says to align without giving a reference, and 1214 which does the alignment.  Reading ITU X.691 section 13, I would not expect this beahvior.  As Wireshark community is the only place I know of an existing product which handles the V.34 additions to T.38, it seems a good place to ask.  Why are these values aligned?  We could not find an ITU reference giving us reason to do so.

Thanks,

Roger Nichols
Firmware Engineer

Cantata Technology, Inc. (a Dialogic company)
15 Crawford Street
Needham, MA 02494
USA

Tel:    781 292 9399
Fax:    781 453 3521
Email:  roger.nichols@xxxxxxxxxxxx
Web:    www.dialogic.com

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