[Openstack-operators] Raising the degree of the scandal

Kevin Benton blak111 at gmail.com
Mon May 18 08:40:24 UTC 2015

This whole discussion is basically pointless because the ebtables work
isn't even done. There is no merged ebtables fix to back-port.

>Additionally, some of us don’t want to run OVS

Well OVS is the reference right now. If you choose to use something
else, there are going to be feature gaps like this. Did you consider
this before trying to remove OVS?

>so an OVS only solution is effectively imho - crap

You mean for people that choose not to use the gate-tested reference driver?

Anyone can just as easily argue that an ebtables solution is crap
because it assumes a filtering bridge so it doesn't work with any
direct plugging setups. However, we try to discourage attacking
contributions that didn't happen to fit a narrow use-case. It's
unproductive and poisonous behavior that discourages people from doing

>you need to run OVS - seems like a stretch if you aren't using GRE/vxlan tunneling for all of your guests.

Tunneling has little to do with OVS. Linux bridge also supports vxlan
and GRE. You can just say why you don't like OVS (e.g. hard to debug,
tooling is different, admins don't know how to use it, etc). This can
help motivate the movement to restart development on the linux bridge

>Since, flat networks are a 100% supported

Who is supporting Linux bridge used as a backend for shared networks
and is claiming they are secure? Whoever is doing that should be on
the receiving end of your complaints.

Please be clear about what you really want here. It sounds like you
want ARP filtering support in the Linux bridge driver. Is that

On Mon, May 18, 2015 at 12:22 AM, Kris G. Lindgren
<klindgren at godaddy.com> wrote:
> I always thought that ebtables was below the stack in the iptables schema -
> but still part of netfilter - thus should be reasonably fast (I would argue
> faster than a user space lookup to openvswitchd).  Considering the rules
> being added are small in number and trivial (on this port allow src/dst mac
> of blah).  Do you have any performance data showing that its slow?  A quick
> google search shows nothing relevant :-).  Additionally, libvirt
> anti-spoofing rules configured via nova using nwfilter uses ebtables to do
> the anti spoofing rules.  No one seems to complain about the performance of
> that...
> Additionally, some of us don’t want to run OVS, so an OVS only solution is
> effectively imho - crap.  We are actively looking at removing OVS from our
> environment due to a number of reasons.  So saying if you run neutron and
> care to have *REAL* network protection - you need to run OVS - seems like a
> stretch if you aren't using GRE/vxlan tunneling for all of your guests.
> I personally agree with George, this stance of "We never said that neutron
> would provide anti-spoofing on flat networks thus we wont backport this,
> because it now brings into scope ebtables", seems to be a pretty huge gap in
> what neutron says it does and the protection it actually provides.  We
> supply security group rules, but stealing someone else's IP or the gateway
> that doesn't belong to you - yep that totally cool with us.  It strikes me
> that neutrons goal to deliver networking is basically two fold. 1.) Provide
> multi-tenant networking 2.) Make sure tenants cant stomp on each other.
> Without number 2 (anti-spoofing) you kinda fail to provide number 1.  Since,
> flat networks are a 100% supported and viable way of doing tenant networking
> I would say that this is a bug and should be backported to kilo/juno.
> I don’t personly buy the new dependency reason, new to neutron - maybe - but
> not new to people running nova/libvirt.  Ebtables is used by libvirt for
> nwfilter, assuming an pretty standard libvirt install ebtables should be
> installed by default.  Additionally, this would have already been a
> dependency in nova-compute due to anti-spoofing support there.
> ____________________________________________
> Kris Lindgren
> Senior Linux Systems Engineer
> GoDaddy, LLC.
> From: Miguel Ángel Ajo <majopela at redhat.com>
> Date: Sunday, May 17, 2015 at 6:33 AM
> To: George Shuklin <george.shuklin at gmail.com>
> Cc: "openstack-operators at lists.openstack.org"
> <openstack-operators at lists.openstack.org>
> Subject: Re: [Openstack-operators] Raising the degree of the scandal
> Probably the solution is not selected to be backported because:
>   * It’s an intrusive change
>   * Introduces new dependencies
>   * Probably it’s going to introduce a performance penalty because eatables
> is slow.
> I’m asking in reviews for this feature to be enabled/disabled via a flag.
> In the future I hope OVS with connection tracking to be merged, so then we
> can
> finally have a proper openvswitch_firewall_driver supporting stateful
> firewalling
> without reflective rules or flag matching (one is slow, the other is
> insecure…)
> Miguel Ángel Ajo
> On Saturday, 16 de May de 2015 at 23:28, George Shuklin wrote:
> On 05/15/2015 07:48 PM, Jay Pipes wrote:
> On 05/15/2015 12:38 PM, George Shuklin wrote:
> Just to let everyone know: broken antispoofing is not an 'security
> issue' and the fix is not planned to be backported to Juno/kilo.
> https://bugs.launchpad.net/bugs/1274034
> What can I say? All hail devstack! Who care about production?
> George, I can understand you are frustrated with this issue and feel
> strongly about it. However, I don't think notes like this are all that
> productive.
> Would a more productive action be to tell the operator community a bit
> about the vulnerability and suggest appropriate remedies to take?
> Ok, sorry.
> Short issue: If few tenants use same network (shared network) one tenant
> may disrupt network activities of other tenant by sending a specially
> crafted ARP packets on behave of the victim. Normally, Openstack
> prohibit usage of unauthorized addresses (this feature is called
> 'antispoofing' and it is essential for multi-tenant clouds). This
> feature were subtly broken (malicious tenant may not use other addresses
> but still may disrupt activities of other tenants).
> Finally, that bug has been fixed. But now they says 'oh, it is not that
> important, we will not backport it to current releases, only to
> "Libery"' because of new etables dependency.
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Kevin Benton

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