Re: [Caml-list] IPv6 packet parsing

[Anil Madhavapeddy <anil@recoil.org>]

On Fri, Oct 18, 2013 at 02:16:12PM +0200, rixed@happyleptic.org wrote:
> -[ Fri, Oct 18, 2013 at 12:59:55PM +0100, Anil Madhavapeddy ]----
> > One feature I'd really like to see in Bitstring is support for Bigarray,
> > since that avoids a copy into the OCaml heap and lets us do quite high
> > performance parsing.  If I remember right, there was a patch on the
> > Bitstring issue tracker, but it wasn't parameterised (so it's either
> > Bistring+string or Bitstring+bigarray, which isn't ideal).
> 
> Pardon my lack of familiarity with bigarrays, but I can't see what's the
> difference between copying packets from pcap ring buffer into a bigarray
> or into a string. Or do you mean using Bigarray.map_file on the whole
> raw ring buffer and handle it without pcap help?

We have a number of use-cases that run OCaml in kernel mode, directly
operating on packets read from a network driver that's also written in
OCaml.  Bigarrays are used as the mechanism for passing around externally
allocated memory (i.e. network card buffers) directly, whereas inspecting
them with a string-based Bigarray requires an expensive data copy.

See: http://anil.recoil.org/papers/2013-asplos-mirage.pdf
or http://www.openmirage.org

-- 
Anil Madhavapeddy                                 http://anil.recoil.org