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Re: [libvirt] [PATCH 0/13] [RFC] Network filtering (ACL) extensions for libvirt




"Daniel P. Berrange" <berrange redhat com> wrote on 03/17/2010 10:40:36 AM:


>
> On Thu, Mar 11, 2010 at 08:06:04AM -0500, Stefan Berger wrote:
> > Hi!
> >
> > The following set of patches add network filtering (ACL) extensions to
> > libvirt and enable network traffic filtering for VMs using ebtables and,
> > depending on the networking technology being used (tap, but not
> > macvtap), also iptables. Usage of either is optional and controlled
> > through filters that a VM is referencing.
> >
> > The ebtables-level filtering is based on the XML derived from the CIM
> > network slide 10 (filtering) from the DMTF website
> > (
http://www.dmtf.org/standards/cim/cim_schema_v2230/CIM_Network.pdf).
> > The XML we derived from this was discussed on the list before. On the
> > ebtables level we currently handle filtering of IPv4 and ARP traffic.
>
> It is planned to cover IPv6 too, either at ebtables or ip6tables
> level ?


Well, the code should be able to handle it and we at least thought about it. I am not an IPv6 expert myself ... currently ... yet. :-)

>
>
> I've not looked at the actual code in detail yet, but the public API,
> virsh commands, XML etc all looks generally good to me. I'll try and
> get you a detailed code review friday/monday once I get through my
> current work items.


Let me post another series later today with the fixes that I have made following your reviews and changes I did make myself.

>
> > One comment about the instantiation of the rules: Since the XML allows
> > to create nearly any possible combination of parameters to ebtables or
> > iptables commands, I haven't used the ebtables or iptables wrappers.
> > Instead, I am writing ebtables/iptables command into a buffer, add
> > command line options to each one of them as described in the rule's XML,
> > write the buffer into a file and run it as a script. For those commands
> > that are not allowed to fail I am using the following format to run
> > them:
> >
> > cmd="ebtables <some options>"
> > r=`${cmd}`
> > if [ $? -ne 0 ]; then
> > echo "Failure in command ${cmd}."
> > exit 1
> > fi
> >
> > cmd="..."
> > [...]
> >
> > If one of the command fails in such a batch, the libvirt code is going
> > pick up the error code '1', tear down anything previously established
> > and report an error back. The actual error message shown above is
> > currently not reported back, but can be later on with some changes to
> > the commands running external programs that need to read the script's
> > stdout.
>
> I understand why you can't use the ebtables/iptables APIs we currently
> have there, but I'm not much of a fan of using the shell script. Isn't
> it just as easy to directly call  virRun() with each set of ARGV to be
> exec'd ?


I hadn't thought about calling that function... I would want to call a function that can handle something like bash scripts, i.e., multiple concatenated fragments as those shown above just to be more 'efficient'. If virRun() can handle that and $? for example would be treated there as the return value (which I think is bash-dependent), I'd be happy to call it as well.

   Stefan

>
>
> Regards,
> Daniel
> --
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