Ah, didn't read this before my previous reply.

dhcp_release is getting called, but dnsmasq is not getting the packet
(dhcp_release works by faking up a DHCP message as if it's coming from
the DHCP client, which tells the server to release the lease.)

If you can't see the packet in your packet dump, then that's significant.

Note that dhcp_release needs an "interface" parameter. That has to be
correct.

Cheers,

Simon.




On 17/05/17 19:12, Graeme Peterson wrote:
> I found the following entry in /var/log/auth.log which shows neutron as
> root (sudo) calling dhcp_release on IP: 132.16.0.13, MAC: 
> fa:16:3e:8e:83:97 two minutes after the DHCPACK and two minutes before
> the dnsmasq-dhcp log failure saying: "not using configured address
> 132.16.0.13 because it is leased to fa:16:3e:8e:83:97". Looks to me like
> Openstack is calling dhcp_release correctly. The dnsmask log is in a
> folder named "34705fcf-4f9c-48eb-b0bc-ac5091e181c8", same as the arg to
> ip netns exec without the "qdhcp-" prefix. So far it looks like a
> dhcp_release/dnsmasq issue to my untrained eye. I have been able to work
> around it somewhat by setting the max lease time to 30 seconds, although
> that seems to be introducing other issues, more investigation required
> there.
> 
> ./auth.log:May 16 16:55:21 my-ucs-69 sudo:  neutron : TTY=unknown ;
> PWD=/var/lib/neutron ; USER=root ; COMMAND=/usr/bin/neutron-rootwrap
> /etc/neutron/rootwrap.conf ip netns exec
> qdhcp-34705fcf-4f9c-48eb-b0bc-ac5091e181c8 dhcp_release tapc5399cce-70
> 132.16.0.13 fa:16:3e:8e:83:97
> 
> Thanks again,
> Graeme
> 
> On 2017-05-17 12:24, Graeme Peterson wrote:
> 
>> Hi all.
>>
>> Sorry if this issue has been discussed and resolved, I am new to the
>> list. I tried to find it in the list, and came across this reference
>> to the issue from Jan 2016:
>>
>> http://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2016q1/010273.html
>>
>>
>> What I am seeing is with OpenStack Newton on Ubuntu 16.10
>> (4.8.0-49-generic), with force_dhcp_release=True in
>> /etc/nova/nova.conf, using tcpdump on the netns for the relevant
>> Openstack network, I see dnsmasq receives the dhcp request, issues an
>> IP, and that IP should be released (Openstack should be calling
>> dhcp_release, I need to figure out how to verify that it is or is not
>> happening, however force_dhcp_release=True is explicitly set in
>> /etc/nova/nova.conf) , but it seems like the dhcp entry isn't being
>> entirely released. The odd thing is that when a new VM wants an IP,
>> tcpdump shows the request coming in for an address, but no reply, and
>> OpenStack thinks it got an IP - the same one that used to belong to
>> the recently terminated VM - but there is no dhcp offer in the
>> tcpdump, and the dnsmasq log shows:
>>
>> May 16 16:53:15 dnsmasq-dhcp[40394]: 3306068020
>> DHCPREQUEST(tapc5399cce-70) 132.16.0.13 fa:16:3e:8e:83:97
>> May 16 16:53:15 dnsmasq-dhcp[40394]: 3306068020 tags: tag0, known,
>> tapc5399cce-70
>> May 16 16:53:15 dnsmasq-dhcp[40394]: 3306068020
>> DHCPACK(tapc5399cce-70) 132.16.0.13 fa:16:3e:8e:83:97 host-132-16-0-13
>> ...
>> ...
>> ...
>> May 16 16:57:12 dnsmasq-dhcp[40394]: 461988430 available DHCP subnet:
>> 132.16.0.0/255.255.0.0
>> May 16 16:57:12 dnsmasq-dhcp[40394]: not using configured address
>> 132.16.0.13 because it is leased to fa:16:3e:8e:83:97
>> May 16 16:57:12 dnsmasq-dhcp[40394]: 461988430
>> DHCPDISCOVER(tapc5399cce-70) 192.168.0.51 fa:16:3e:31:de:d3 no address
>> available
>>
>> I don't see a log entry for a release of 132.16.0.13, not sure if
>> there should be one.
>>
>>
>> Is this a known and hopefully fixed issue? Can I provide further info
>> to help investigate it?
>>
>> Thanks,
>> Graeme
>>
>>
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>> http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
> 
> 
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