tcpdump mailing list archives

Re: Reserving a libpcap DLT value


From: Kent Dahlgren <kent () praesum com>
Date: Wed, 09 Oct 2002 05:57:59 -0700

Guy

My goal here is not to get into the great debate about file
formats, but to make Ethereal useful for debugging some
new interfaces.

If you absolutely have a problem with the named transport
approach, then I need three new transports defined for
libpcap:

        DLT_RIO         for RapidIO
        DLT_PCI_EXP     for PCI Express
        DLT_AURORA      for the Xilinx Aurora link layer

How do you want to go about adding these?

Kent

At 01:10 AM 10/9/2002 -0700, Guy Harris wrote:
On Wed, Oct 09, 2002 at 10:00:31AM +0200, Hannes Gredler wrote:
> IMHO changing protocols/formats once code is shipping is clearly a thing
> to avoid;

I.e., we can never ever ever introduce a new libpcap format to add new
capabilities?  I don't agree with that at all.  It's not as if the new
format would use the same magic number, so it's not as if you've changed
*the* libpcap format, so that new programs can't read old files.

(And as for never changing protocols, well, so much for NFSv3, NFSv4,
and IPv6....)

> the DLT_private type would fiz both problems at the expense of
> a few extra bytes ...

It "fixes" the problem of changing the file format by, in effect,
changing the file format - if only the DLT_private type can have
extensions, then only versions of libpcap that support the DLT_private
type *and* applications that support it can handle files with
extensions, which means that, for all intents and purposes, you've
changed the file format (i.e., you've made a file format that older code
can't read, which is the *ONLY* problem I see with introducing a
second-generation libpcap format).


-
This is the TCPDUMP workers list. It is archived at
http://www.tcpdump.org/lists/workers/index.html
To unsubscribe use mailto:tcpdump-workers-request () tcpdump org?body=unsubscribe


Current thread: