On Jan 17, 2011, at 8:11 AM, Jens Grimmer wrote:

> Hi wireshark community,

(Actually, this list is more like "the tcpdump and libpcap community", but, not 
surprisingly, there's some overlap between the two communities.)

> I would like to ask for a new encapsulation type for libpcap files 
> (WTAP_ENCAP_xx as well as DLT_xx value).

WCAP_ENCAP_ values aren't necessarily fixed values; unlike LINKTYPE_ values, 
they don't appear in files.  There's no reservation-in-advance procedure for 
them; you'd get a new one when contributing a Wireshark dissector patch.

DLT_ values and the corresponding LINKTYPE_ values are assigned here by 
tcpdump.org, as the LINKTYPE_ value *does* appear in files.

> [note: If I'm not wrong we would nee a new, unique DLT_NG40 (>=230) value in 
> pcap/bpf.h as well as new WTAP_ENCAP_NG40 (>=129) and WTAP_FILE_NG40 (>=61) 
> in wiretap/wtap.h.
> - Sure these values need to bee unique, so I have to ask to get them 
> reserved.]
> 
> I'm a developer at the NG4T GmbH – a start-up in Berlin, Germany founded by 
> former Tektronix employees. We provide protocol test software, mainly running 
> on Linux machines. For a customer project we have to integrate ATM 
> hard/software which is not yet supported by libpcap/wireshark. Especially for 
> AAL2 and AAL5 monitoring we have to provide additional context information.
> In the past weeks I prepared (locally) a couple of files (for libpcap and 
> wireshark). What are the next steps to get these enhancements and new files 
> into the common development cycle for common use?

The first step is to assign the DLT_/LINKTYPE_ value; after that, just submit 
patches for libpcap to [email protected] or the libpcap SourceForge 
site's tracker, and submit patches for Wireshark to [email protected] 
or the Wireshark Bugzilla.

> If you need more information, please send me a mail.
> 
> [note: The network interface card is the XS2010 card from Xalyo (a company in 
> Switzerland) which carries ATM traffic. From my knowledge this card is not 
> yet supported by libpcap/wireshark. Currently we have to monitor mainly AAL5 
> traffic (e.g..: here we have to provide channel information like VPI,VCI) and 
> AAL2 traffic (e.g.: here we have to provide VPI,VCI, CID and additional 
> context information to the FP dissector like channel type, division, 
> direction – similar to the information provided by the Tektronix K12).

So presumably the packet data begins with a pseudo-header with that 
information; could you give a description of that pseudo-header?

> I checked out the libpcap and wireshark projects from svn.

(Presumably you mean "I checked out the libpcap project from Git and the 
Wireshark project from SVN"; libpcap and tcpdump went from CVS to Git without 
stopping at SVN first.)

> For the pcap library I wrote a new pcap-ng40.c/h similar to the pcap-dag.c/h. 
> For wireshark I made new epan/dissectors/packet-ng40.c/h and put the 
> necessary calls to file_access.c, pcap-common.c, wtap.c and defined the 
> pseudo- header-structure in wtap.h. So far on my test machines the modified 
> pcap-libray as well wireshark are running fine under 32bit and 64bit 
> Debian-Linux. Nevertheless I have to do some enhancements the next days. So I 
> expect to have a 'check-in candidate' about end of January. For sure, all 
> software we provide to integrate this card, is GNU public licensed.]

libpcap (and tcpdump) are under a BSD license - it's currently mostly the 
4-clause BSD license, which is considered incompatible with the GPL:

        http://www.gnu.org/licenses/gpl-faq.html#OrigBSD

Even if it were converted to the 3-clause BSD license, it might be better if 
the libpcap changes were BSD-licensed - Michael?

(Wireshark is GPLv2, so code for it should be GPLv2-licensed.)-
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