Re: Stack virtualization (was: running out of mbufs?)
From: Andre Oppermann (andre_at_freebsd.org)
Date: 08/10/05
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Date: Wed, 10 Aug 2005 13:16:11 +0200 To: Jeremie Le Hen <jeremie@le-hen.org>
Jeremie Le Hen wrote:
>
> > I haven't fully explored all applications and possible tie-ins with
> > jails, virtual stacks etc. but it looks very interesting.
> >
> > For example I want to have multiple routing tables within the same
> > stack. These routing tables can be opaque or fall-through and match
> > on the source and destination address (not at the same time though).
> > This way we get ultimate routing flexibility in using FreeBSD as
> > router. An incoming packet on interface em0 with group priority
> > would first match into routing table X, and if no match fall-through
> > to the default routing table. Or you could create a source matching
> > routing table Y sending matching packets further to table Z for
> > low priority routing.
>
> What you are saying clearly reminds me the way Linux does it.
> Basically they have about 256 routing tables available, one of them
> being the default one (254 IIRC). Once you have filled the those you
> want to use, you can assign a routing table to each packet with what
> they simply call "rules". The routing criteria are classical, such as
> "from", "to", "tos", "iif" (incoming interface)...
> (See the manpage [1] for more informations, the IPRoute2 framework is
> quite powerful.)
>
> One of the most powerful criteria it provides is "fwmark" which allows
> to match against a mark stamped on the skbuff (their mbuf) by the
> firewall. This leads to the ability to route packets based on the
> whole capabilities of the firewall framework (NetFilter in this case) :
> TCP/UDP ports, ICMP types, and so on...
This is mostly the direction I'll go. However any packet classification
other than on IP addresses is to be done by a packet filter (ipfw, pf,
ipfilter).
> This might appear a little bit hackish to networking guys, especially
> those ones that are working on backbone routers, but this flexibility
> is almost nothing to add (pf already has the ability to tag packets,
> IIRC) and it doesn't constrain the design at all, IMHO. FYI, this has
> already been discussed in this subthread [2].
The biggest problem for more complex IP routing setups is wrapping ones
head around the endless possibilities. The very concept of longest-
prefix match on a hop by hop basis is difficult to graps for too many
people unfortunatly. I have things in (very large) enterprise environments
you wouldn't believe...
-- Andre > I have to say that I was quite impressed by Linux networking > capabilities (this was in the 2.4 days), and that's why I would really > like to see FreeBSD to be able to do this. > > > It's hard to describe this textually to its full extent. That's why > > my upcoming paper will have mostly graphics depicting the packet flow > > and the processing options. > > I'm in haste to read your paper. > > [1] http://www.manpage.org/cgi-bin/man/man2html?8+ip > [2] http://lists.freebsd.org/pipermail/freebsd-net/2005-June/007743.html > > Regards, > -- > Jeremie Le Hen > < jeremie at le-hen dot org >< ttz at chchile dot org > _______________________________________________ freebsd-net@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-net To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org"
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