Re: Reserving a libpcap DLT value

[Guy Harris <gharris () sonic net>]

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).
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