Open Stack

Hi,

As we talked in last IPv6 sub-team meeting, I was able to construct and 
send IPv6 unsolicited neighbor advertisement for external gateway 
interface by python tool *scapy*:

http://www.secdev.org/projects/scapy/

http://www.idsv6.de/Downloads/IPv6PacketCreationWithScapy.pdf


However, I am having trouble to send this unsolicited neighbor 
advertisement in a given namespace. All the current namespace operations 
leverage ip netns exec and shell command. But we cannot do this to scapy 
since it's python code. Can anyone advise me on this?

Thanks,
Xu Han

On 09/05/2014 05:46 PM, Xu Han Peng wrote:
> Carl,
>
> Seem so. I think internal router interface and external gateway port 
> GARP are taken care by keepalived during failover. And if HA is not 
> enable, _send_gratuitous_arp is called to send out GARP.
>
> I think we will need to take care IPv6 for both cases since keepalived 
> 1.2.0 support IPv6. May need a separate BP. For the case HA is enabled 
> externally, we still need unsolicited neighbor advertisement for 
> gateway failover. But for internal router interface, since Router 
> Advertisement is automatically send out by RADVD after failover, we 
> don't need to send out neighbor advertisement anymore.
>
> Xu Han
>
>
> On 09/05/2014 03:04 AM, Carl Baldwin wrote:
>> Hi Xu Han,
>>
>> Since I sent my message yesterday there has been some more discussion
>> in the review on that patch set.  See [1] again.  I think your
>> assessment is likely correct.
>>
>> Carl
>>
>> [1] 
>> https://review.openstack.org/#/c/70700/37/neutron/agent/l3_ha_agent.py
>>
>> On Thu, Sep 4, 2014 at 3:32 AM, Xu Han Peng <pengxuhan at gmail.com> wrote:
>>> Carl,
>>>
>>> Thanks a lot for your reply!
>>>
>>> If I understand correctly, in VRRP case, keepalived will be 
>>> responsible for
>>> sending out GARPs? By checking the code you provided, I can see all the
>>> _send_gratuitous_arp_packet call are wrapped by "if not is_ha" 
>>> condition.
>>>
>>> Xu Han
>>>
>>>
>>>
>>> On 09/04/2014 06:06 AM, Carl Baldwin wrote:
>>>
>>> It should be noted that "send_arp_for_ha" is a configuration option
>>> that preceded the more recent in-progress work to add VRRP controlled
>>> HA to Neutron's router.  The option was added, I believe, to cause the
>>> router to send (default) 3 GARPs to the external gateway if the router
>>> was removed from one network node and added to another by some
>>> external script or manual intervention.  It did not send anything on
>>> the internal network ports.
>>>
>>> VRRP is a different story and the code in review [1] sends GARPs on
>>> internal and external ports.
>>>
>>> Hope this helps avoid confusion in this discussion.
>>>
>>> Carl
>>>
>>> [1] 
>>> https://review.openstack.org/#/c/70700/37/neutron/agent/l3_ha_agent.py
>>>
>>> On Mon, Sep 1, 2014 at 8:52 PM, Xu Han Peng <pengxuhan at gmail.com> 
>>> wrote:
>>>
>>> Anthony,
>>>
>>> Thanks for your reply.
>>>
>>> If HA method like VRRP are used for IPv6 router, according to the 
>>> VRRP RFC
>>> with IPv6 included, the servers should be auto-configured with the 
>>> active
>>> router's LLA as the default route before the failover happens and still
>>> remain that route after the failover. In other word, there should be 
>>> no need
>>> to use two LLAs for default route of a subnet unless load balance is
>>> required.
>>>
>>> When the backup router become the master router, the backup router 
>>> should be
>>> responsible for sending out an unsolicited ND neighbor advertisement 
>>> with
>>> the associated LLA (the previous master's LLA) immediately to update 
>>> the
>>> bridge learning state and sending out router advertisement with the 
>>> same
>>> options with the previous master to maintain the route and bridge 
>>> learning.
>>>
>>> This is shown in http://tools.ietf.org/html/rfc5798#section-4.1 and the
>>> actions backup router should take after failover is documented here:
>>> http://tools.ietf.org/html/rfc5798#section-6.4.2. The need for 
>>> immediate
>>> messaging sending and periodic message sending is documented here:
>>> http://tools.ietf.org/html/rfc5798#section-2.4
>>>
>>> Since the keepalived manager support for L3 HA is merged:
>>> https://review.openstack.org/#/c/68142/43. And keepalived release 1.2.0
>>> supports VRRP IPv6 features ( 
>>> http://www.keepalived.org/changelog.html, see
>>> Release 1.2.0 | VRRP IPv6 Release). I think we can check if 
>>> keepalived can
>>> satisfy our requirement here and if that will cause any conflicts with
>>> RADVD.
>>>
>>> Thoughts?
>>>
>>> Xu Han
>>>
>>>
>>> On 08/28/2014 10:11 PM, Veiga, Anthony wrote:
>>>
>>>
>>>
>>> Anthony and Robert,
>>>
>>> Thanks for your reply. I don't know if the arping is there for NAT, 
>>> but I am
>>> pretty sure it's for HA setup to broadcast the router's own change 
>>> since the
>>> arping is controlled by "send_arp_for_ha" config. By checking the 
>>> man page
>>> of arping, you can find the "arping -A" we use in code is sending 
>>> out ARP
>>> REPLY instead of ARP REQUEST. This is like saying "I am here" 
>>> instead of
>>> "where are you". I didn't realized this either until Brain pointed 
>>> this out
>>> at my code review below.
>>>
>>>
>>> That’s what I was trying to say earlier.  Sending out the RA is the 
>>> same
>>> effect.  RA says “I’m here, oh and I’m also a router” and should 
>>> supersede
>>> the need for an unsolicited NA.  The only thing to consider here is 
>>> that RAs
>>> are from LLAs.  If you’re doing IPv6 HA, you’ll need to have two 
>>> gateway IPs
>>> for the RA of the standby to work.  So far as I know, I think 
>>> there’s still
>>> a bug out on this since you can only have one gateway per subnet.
>>>
>>>
>>>
>>> http://linux.die.net/man/8/arping
>>>
>>> https://review.openstack.org/#/c/114437/2/neutron/agent/l3_agent.py
>>>
>>> Thoughts?
>>>
>>> Xu Han
>>>
>>>
>>> On 08/27/2014 10:01 PM, Veiga, Anthony wrote:
>>>
>>>
>>> Hi Xuhan,
>>>
>>> What I saw is that GARP is sent to the gateway port and also to the 
>>> router
>>> ports, from a neutron router. I’m not sure why it’s sent to the 
>>> router ports
>>> (internal network). My understanding for arping to the gateway port 
>>> is that
>>> it is needed for proper NAT operation. Since we are not planning to 
>>> support
>>> ipv6 NAT, so this is not required/needed for ipv6 any more?
>>>
>>>
>>> I agree that this is no longer necessary.
>>>
>>>
>>> There is an abandoned patch that disabled the arping for ipv6 
>>> gateway port:
>>> https://review.openstack.org/#/c/77471/3/neutron/agent/l3_agent.py
>>>
>>> thanks,
>>> Robert
>>>
>>> On 8/27/14, 1:03 AM, "Xuhan Peng" <pengxuhan at gmail.com> wrote:
>>>
>>> As a follow-up action of yesterday's IPv6 sub-team meeting, I would 
>>> like to
>>> start a discussion about how to support l3 agent HA when IP version 
>>> is IPv6.
>>>
>>> This problem is triggered by bug [1] where sending gratuitous arp 
>>> packet for
>>> HA doesn't work for IPv6 subnet gateways. This is because neighbor 
>>> discovery
>>> instead of ARP should be used for IPv6.
>>>
>>> My thought to solve this problem turns into how to send out neighbor
>>> advertisement for IPv6 routers just like sending ARP reply for IPv4 
>>> routers
>>> after reading the comments on code review [2].
>>>
>>> I searched for utilities which can do this and only find a utility 
>>> called
>>> ndsend [3] as part of vzctl on ubuntu. I could not find similar 
>>> tools on
>>> other linux distributions.
>>>
>>> There are comments in yesterday's meeting that it's the new router's 
>>> job to
>>> send out RA and there is no need for neighbor discovery. But we 
>>> didn't get
>>> enough time to finish the discussion.
>>>
>>>
>>> Because OpenStack runs the l3 agent, it is the router. Instead of 
>>> needing
>>> to do gratuitous ARP to alert all clients of the new MAC, a simple 
>>> RA from
>>> the new router for the same prefix would accomplish the same, 
>>> without having
>>> to resort to a special package to generate unsolicited NA packets.  
>>> RAs must
>>> be generated from the l3 agent anyway if it’s the gateway, and we’re 
>>> doing
>>> that via radvd now.  The HA failover simply needs to start the 
>>> proper radvd
>>> process on the secondary gateway and resume normal operation.
>>>
>>>
>>> Can you comment your thoughts about how to solve this problem in this
>>> thread, please?
>>>
>>> [1] https://bugs.launchpad.net/neutron/+bug/1357068
>>>
>>> [2] https://review.openstack.org/#/c/114437/
>>>
>>> [3] http://manpages.ubuntu.com/manpages/oneiric/man8/ndsend.8.html
>>>
>>> Thanks,
>>> Xu Han
>>>
>>>
>>>
>>> -Anthony
>>>
>>>
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