Re: Request for new Link-layer header type

[<HPfrommer () hilscher com>]

Cool, thanks alot!


-----Ursprüngliche Nachricht-----
Von: tcpdump-workers-owner () lists tcpdump org [mailto:tcpdump-workers-owner () lists tcpdump org] Im Auftrag von Guy 
Harris
Gesendet: Mittwoch, 14. September 2011 10:17
An: tcpdump-workers () lists tcpdump org
Betreff: Re: [tcpdump-workers] Request for new Link-layer header type


On Sep 14, 2011, at 12:31 AM, <HPfrommer () hilscher com> wrote:

> Yes, that's right, these are the sequences described in sections 3.2.1 and 3.2.2. Even though, in hexadecimal 
> notation this would be 0x55 0x55 0x55 0x55 0x55 0x55 0x55 and 0xd5, respectively (as denoted in section 3.3)

Sigh.  I guess the bottommost bit is shown first because it's the first bit transmitted, which probably makes sense to 
hardware people; I guess we software people who usually see the high-order bit shown first just have to remember that 
IEEE standards do things differently.

In any case, I've assigned 240 as DLT_ETHERNET_HILSCHER/LINKTYPE_ETHERNET_HILSCHER, for non-transparent packets (with 
the 4-byte pseudo-header before the Ethernet header, but without the preamble or SFD), and 241 as 
DLT_ETHERNET_HILSCHER_TRANSPARENT/LINKTYPE_ETHERNET_HILSCHER_TRANSPARENT, for transparent packets (with the 4-byte 
pseudo-header followed by the 7-byte preamble, followed by the 1-byte SFD, followed by the Ethernet header), and 
checked that, including filter support, into the libpcap trunk and 1.2 branch.

(That's 11110000 and 11110001, not 00001111 and 10001111. :-) :-) :-))

I'll add tcpdump support for printing those packets (it'll ignore the pseudo-header and, for 
DLT_ETHERNET_HILSCHER_TRANSPARENT, the preamble and SFD), and add the two new link-layer types to

        http://www.tcpdump.org/linktypes.html

along with a page containing your description of the pseudo-header (but I'll leave the "transparent" bit out, as that's 
indicated by the link-layer header type).-
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