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Wow. Real problem. I check it - it allows one tenant to interrupt 
traffic on other. I was not able to intercept TCP traffic, victim lost 
connection and TCP  was struggling with retransmissions, but it was not 
good.

But idea of 'no routers in software' is too appealing. I think I'll 
stick with this idea (and wait for fix). Plus, I think, OVS can provide 
some kind of excellent antispoofing mechanism (OVS can use nw_src/nw_dst 
for arp filtering) - if no fix will be available, I'll do some crude fix 
on neutron/nova with OVS (I don't really like etables).

On 01/09/2015 09:25 PM, Kris G. Lindgren wrote:
> Also, If you are running this configuration you should be aware of the
> following bug:
>
> https://bugs.launchpad.net/neutron/+bug/1274034
>
> And the corresponding fix: https://review.openstack.org/#/c/141130/
>
> Basically - Neutron security group rules do nothing to protect against arp
> spoofing/poisoning from vm's.  So its possible under a shared network
> configuration for a vm to arp for another vm's ip address and temporarily
> knock that vm offline.  The above commit - which is still a WIP adds
> ebtable rules to allow neutron to filter protocols other than IP (eg arp).
>
> ____________________________________________
>   
> Kris Lindgren
> Senior Linux Systems Engineer
> GoDaddy, LLC.
>
>
>
> On 1/8/15, 9:50 AM, "Kris G. Lindgren" <klindgren at godaddy.com> wrote:
>
>>
>> On 1/8/15, 4:34 AM, "Antonio Messina" <antonio.s.messina at gmail.com> wrote:
>>
>>> On Thu, Jan 8, 2015 at 12:12 PM, gustavo panizzo (gfa) <gfa at zumbi.com.ar>
>>> wrote:
>>>>
>>>> On 01/08/2015 07:01 PM, Antonio Messina wrote:
>>>>> On Thu, Jan 8, 2015 at 11:53 AM, gustavo panizzo (gfa)
>>>>> <gfa at zumbi.com.ar>
>>>>> wrote:
>>>>
>>>>>> i may be wrong as i haven't tested that on juno, but in icehouse and
>>>>>> havana
>>>>>> i've setup external/provider networks one for each tenant
>>>>>
>>>>> Ah, ok, this is the point. What I would like to have instead is
>>>>>
>>>>> 1) one big external network with routable, private IPs, to be used by
>>>>> *any*
>>>>>      tenant (where any tenant can plug ports)
>>>>
>>>> neutron net-create --shared should do the trick
>>> I guess the problem is that I was creating *external* _and_ *shared*
>>> network, but if I don't want to use floating IPs from that network I
>>> probably don't need the network to be external, right?
>> Correct.  We have our "external networks" (private ip) only configured as
>> shared so any vm from any tenant can create a port on it.  External means
>> it's meant to be plugged into a router/l3 agent.
>>
>>
>>>>> 3) small external networks dedicated to a tenant
>>>>
>>>> neutron net-create --tenant-id XXXXX-XXXXXX
>>>>
>>>>
>>>> i've made that mix (also add tenantn networks) in my lab running
>>>> icehouse
>>>> (2014.1.2) worked fine, i've upgraded it to juno but i haven't test
>>>> that yet
>>> Thank you, I will test it further.
>>>
>>>> do you run more than one l3 agent? are you floating ips configured on
>>>> br-ex?
>>>> i think if you fix the policy.json on nova you should get it working
>>> I currently have only 1 l3-agent running, but it's suboptimal. I would
>>> like to have L3-HA for the floating IPs and DVR for the shared and
>>> tenant networks, but as far as I know it's not currently supported. I
>>> plan to deploy the production cloud after Kilo release, and crossing
>>> my fingers...
>>>
>>> Floating IPs are currently configured on br-ex.
>> You have floating ips working under this configuration?
>>
>> If so then that means you are using the neutron router as the gateway for
>> all of your vm's and not the gateway provided by your network device.  As
>> soon as you created a router and attached the the shared network to it the
>> router got configured with the gateway address that you configured in your
>> network.  You may want to make sure that you don¹t have traffic flapping
>> between your real network gateway and your neutron gateway on your l3
>> router.
>>
>> The reason why floating ip's won't work under this configuration (using a
>> real network device for the gateway) is the fact that the floating ip is
>> applied at the router as a nat so the traffic flows like: Client (4.2.2.1)
>> -> floating ip (8.8.8.8) -> external port on router -> The router changes
>> the destination IP from the floating ip to the private IP of the vm
>> (172.23.2.40) and send the traffic out to the vm via the routers
>> connection on the shared network.  The VM responds to the client traffic
>> which is not in its subnet directly to the default gateway (172.23.0.1).
>> The gateway (if it is a neutron gateway) will then undo the nat and send
>> the traffic back to the client.
>>
>> Where this breaks down with a physical network gateway is when the traffic
> >from the VM is sent to the real network gateway - the gateway doesn't know
>> anything about the nat and does not re-map the vm ip to the floating ip.
>> IE The client ip never gets changed to the floating ip and sent back to
>> the client IP.  The Response would be seen as coming directly from
>> 172.23.2.40, instead of 8.8.8.8.  So you will never establish a tcp
>> connection.
>>
>> If you have this working somehow - please let me know.  When we attempted
>> to run this configuration we ran into the above issues with floating ips
>> when using a real gateway on a network device.
>>
>> Note: this is also why you need to create your shared network with a
>> specific router to the metadata service.  Most likely on your real network
>> gateway you haven't added a route for 169.254.169.254 to a specific ip.
>>
>>> .a.
>>>
>>> -- 
>>> antonio.s.messina at gmail.com
>>> antonio.messina at uzh.ch                     +41 (0)44 635 42 22
>>> S3IT: Service and Support for Science IT   http://www.s3it.uzh.ch/
>>> University of Zurich
>>> Winterthurerstrasse 190
>>> CH-8057 Zurich Switzerland
>>>
>>> _______________________________________________
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>>> OpenStack-operators at lists.openstack.org
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