Bug#991613: DHCPv6 problem in our image: needs "-D LL" when spawning dhclient

[Thomas Goirand <zigo@debian.org>]

Hi Bastian,

Thanks for replying.

On 7/30/21 10:03 AM, Bastian Blank wrote:
> Hi
> 
> On Wed, Jul 28, 2021 at 05:22:43PM +0200, Thomas Goirand wrote:
>> - Initial boot:
>> 2021-07-28T12:26:38.804683+00:00 pub1-network-3 dnsmasq-dhcp[3765807]: DHCPSOLICIT(tap67fa8c3f-8d) 00:01:00:01:28:94:09:7b:fa:16:3e:f1:a9:da
>> 2021-07-28T12:26:38.805023+00:00 pub1-network-3 dnsmasq-dhcp[3765807]: DHCPADVERTISE(tap67fa8c3f-8d) 00:01:00:01:28:94:09:7b:fa:16:3e:f1:a9:da no addresses available
>>
>> - Server side:
>> /var/lib/neutron/dhcp/dcf25c41-9057-4bc2-8475-a2e3c5d8c662/host:fa:16:3e:f1:a9:da,tag:dhcpv6,host-<redacted>--143.dc3-a.pub1.infomaniak.cloud.,[<redacted>::143]
>> /var/lib/neutron/dhcp/dcf25c41-9057-4bc2-8475-a2e3c5d8c662/leases:1627481056 1056025050 2001:1600:10:100::143 host-<redacted>--143 00:01:00:01:28:94:03:11:fa:16:3e:f1:a9:da
> 
> So dnsmasq is wrongly configured to take the DUID into account, even if
> it does not matter for the address selection, because the address is
> fixed?

Do you have any suggestion on how to start dnsmasq, so it doesn't take
DUID into account? Is there any parameter to do that?

> 
>> We see here that DHCPv6 fails because the DUID sent by the distro isn't the
>> same as the initial build of the VM:
> 
> Well, the pending change in network machinery will scramble the DUID
> anyway.  So you can't rely on it.

Ok, so probably I can fix the way dnsmasq start. In OpenStack, there's
enough options to add whatever I want.

Here's how currently, dnsmasq starts for me (anonymised though...):

dnsmasq --no-hosts --no-resolv \

--pid-file=/var/lib/neutron/dhcp/dcf25c41-9057-4bc2-8475-a2e3c5d8c662/pid --dhcp-hostsfile=/var/lib/neutron/dhcp/<UUID>/host
\
  --addn-hosts=/var/lib/neutron/dhcp/<UUID>/addn_hosts \
  --dhcp-optsfile=/var/lib/neutron/dhcp/<uuid>/opts \
  --dhcp-leasefile=/var/lib/neutron/dhcp/<uuid>/leases \
  --dhcp-match=set:ipxe,175 \
  --dhcp-userclass=set:ipxe6,iPXE \
  --local-service \
  --bind-dynamic \

--dhcp-range=set:subnet-<subnet-uuid>,<public-ipv4>,static,255.255.255.0,86400s
\

--dhcp-range=set:subnet-<ipv4-subnet-uuid>,<public-ipv6>::,static,64,86400s
\
  --dhcp-option-force=option:mtu,1500 \
  --dhcp-lease-max=16777216 \
  --conf-file=/dev/null \
  --domain=something.example.com.

In dhcp_agent.ini it's possible to set dnsmasq_config_file = to some
value, and then if I can set anything that avoids the problem there...

So far, I haven't found a way (even after reading dnsmasq's man page,
but I may have missed something...).

FYI, I've just opened a thread in the openstack-discuss list to see if
this can be fixed. Though ideally, it'd be nice to have both my
deployment AND the image fixed for this problem, so nobody can ever
encounter the issue again.

Cheers,

Thomas Goirand (zigo)