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Anthony and Robert,<br>
<br>
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. <br>
<br>
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<a href="http://linux.die.net/man/8/arping">http://linux.die.net/man/8/arping</a><br>
<br>
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<a
href="https://review.openstack.org/#/c/114437/2/neutron/agent/l3_agent.py">https://review.openstack.org/#/c/114437/2/neutron/agent/l3_agent.py</a><br>
<br>
Thoughts?<br>
<br>
Xu Han<br>
<br>
<br>
<div class="moz-cite-prefix">On 08/27/2014 10:01 PM, Veiga, Anthony
wrote:<br>
</div>
<blockquote
cite="mid:D0235C60.2554%25anthony_veiga@cable.comcast.com"
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<div><br>
Hi Xuhan,</div>
<div><br>
</div>
<div>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?</div>
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<div><br>
</div>
<div>I agree that this is no longer necessary.</div>
<div><br>
</div>
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<div><br>
</div>
<div>There is an abandoned patch that disabled the arping
for ipv6 gateway port: <a moz-do-not-send="true"
href="https://review.openstack.org/#/c/77471/3/neutron/agent/l3_agent.py">https://review.openstack.org/#/c/77471/3/neutron/agent/l3_agent.py</a></div>
<div><br>
</div>
<div>thanks,</div>
<div>Robert</div>
<div><br>
</div>
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<div>
<div>On 8/27/14, 1:03 AM, "Xuhan Peng" <<a
moz-do-not-send="true"
href="mailto:pengxuhan@gmail.com">pengxuhan@gmail.com</a>>
wrote:</div>
</div>
<div><br>
</div>
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<div>
<div>
<div dir="ltr">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.
<div><br>
</div>
<div style="">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.</div>
<div style=""><br>
</div>
<div style="">My thought to solve this problem
turns into how to send out<font color="#000000"
face="sans-serif"> neighbor advertisement for
IPv6 routers just like sending ARP reply for
IPv4 routers after reading the comments on
code review [2].</font></div>
<div style=""><font color="#000000"
face="sans-serif"><br>
</font></div>
<div style=""><font color="#000000"
face="sans-serif">I searched for utilities
which can do this and only find a utility
called ndsend [3] as part of vzctl </font><span
style="color:rgb(0,0,0);font-family:sans-serif">on ubuntu. I could not
find similar tools on other linux
distributions. </span></div>
<div style=""><br>
</div>
<div style="">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. </div>
</div>
</div>
</div>
</blockquote>
</span></div>
</blockquote>
</span>
<div><br>
</div>
<div>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.</div>
<div><br>
</div>
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<div>
<div>
<div dir="ltr">
<div style=""><br>
</div>
<div style="">Can you comment your thoughts about
how to solve this problem in this thread,
please?</div>
<div style=""><br>
</div>
<div style="">[1] <a moz-do-not-send="true"
href="https://bugs.launchpad.net/neutron/+bug/1357068">https://bugs.launchpad.net/neutron/+bug/1357068</a></div>
<div style=""><br>
</div>
<div style="">[2] <a moz-do-not-send="true"
href="https://review.openstack.org/#/c/114437/">https://review.openstack.org/#/c/114437/</a></div>
<div style=""><br>
</div>
<div style="">[3] <a moz-do-not-send="true"
href="http://manpages.ubuntu.com/manpages/oneiric/man8/ndsend.8.html">
http://manpages.ubuntu.com/manpages/oneiric/man8/ndsend.8.html</a></div>
<div style=""><br>
</div>
<div style="">Thanks,</div>
<div style="">Xu Han </div>
</div>
</div>
</div>
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<div><br>
</div>
<div><br>
</div>
<div>-Anthony</div>
<br>
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