Re: RFD: New language to write dissectors

[Tyson Key <tyson.key () gmail com>]

Hmm,

What about implementing a compiler that generates C dissector source code,
from NPLt m, or WSGD dissector code? Or would that be overkill for what
we're trying to do?

Just my 0.02p...

Tyson.

2012/7/15 Jakub Zawadzki <darkjames-ws () darkjames pl>

> On Sat, Jul 14, 2012 at 03:31:06PM -0700, Guy Harris wrote:
> > On Jul 14, 2012, at 8:26 AM, Jakub Zawadzki wrote:
> >
> > > It'd be great if we have some abstract and pure (no C/assembly inline)
> language to write dissectors.
> > Or "to describe protocols and the way packets for those protocols are
> displayed" - the languages in question wouldn't be as procedural as
> C/Lua/etc, they'd be more descriptive.
> > > We could invent yet another protocol desciption language,
> >
> > ...but, as you suggest, we probably shouldn't.
>
> http://imgs.xkcd.com/comics/standards.png ;-)
>
> > I'm not sure it has to be a choice, though - we could implement both,
> resources permitting, of course.  (And, of course, given that there are
> many already-existing languages that describe protocols - ASN.1, {OSF
> IDL/MIDL/PIDL} for DCE RPC, rpcgen for ONC RPC, CORBA IDL, xcb for X11 - we
> will probably never have the One True Protocol Description Language.)
>
> I'd rather support one, and later have some compiler from language A to B.
>
>
> > > I'm bigger fan of NPL (...) but there might exists some legal (patents
> for grammar/implementation?!) issues.
> > That would be one concern - even having "our own" language, such as
> wsgd, runs the risk of infringing a patent, but, well, *writing software of
> just about any sort* runs the risk of infringing a patent;
> > however, we're dealing with a large corporation in the case of NPL, so
> there's probably a greater risk that some or all of it is covered by
> patents.
> > Were Microsoft to explicitly state that there are no patents on
> NPL-the-language or that they're granting a royalty-free license for all
> implementations (perhaps with a "mutual assured destruction" clause,
> > so that were we to patent some feature of Wireshark and sue Microsoft
> for violating that patent, our license for their patents would terminate),
> and the same applied to any patents they hold on their
> > implementation of NPL that would block independent useful
> implementations, that might help.
>
> I'm not sure if it was covered by recent Oracle vs Google lawsuits.
> Maybe Riverbed could help us with it? Gerald?
>
> > > With wsgd we could reuse some existing code of plugin.
> >
> > ...and we also have more freedom to extend the language, e.g. to support
> preferences for a protocol
>
> or support for columns/expert info.
>
> > Were there an "Open NPL Consortium" of some sort where multiple
> implementers of NPL could propose extensions, and perhaps a way an
> implementation could offer private extensions without worrying about
> colliding with other implementations or future standards, that might help.
>
> It'd also clear legal status of NPL language.
>
>
> > (It also raises the question of whether interpreted execution of that
> "machine code" or translation to C or machine language will be faster -
> interpreted execution *could* result in a smaller cache footprint if the
> interpreter is small enough and the code "high-level" enough to be fairly
> dense, although it does involve difficult-at-best-to-predict branches in
> the interpretive loop.)
>
> I was thinking to use LLVM. For built-in dissectors we could compile
> dissectors to object file/ assembly, for user dissectors we'll benefit from
> LLVM JIT.
> But anyway we need compiler to C. For prototype (does it work?) and later
> as fallback for people who don't have LLVM.
> ... Or can LLVM libraries be strong dependency?
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