[tempest] No metadata route in test_dualnet* family

[Evgeny Antyshev]

We run tempest in such an environment that all ssh keys, personality files, etc. go through metadata service.
Which requires metadata route to 169.254.169.254 being provided by DHCP.

We faced rather complicated problem in scenario/test_network_v6.py:

Networking configuration comprises of 4 steps:
1) Private network creation
2) Router creation and plugging it as a gateway in external network
3) Subnet creation
4) Adding router interface to the subnet

This sequence leads to that DHCP service provides static metadata route, and our scenario works.
That's how it is done in create_networks() from tempest/scenario/manager.py (which used in the majority of tests).

But, prepare_network() of scenario/test_network_v6.py first creates subnet, and after that it creates router (1-3-2-4).
DHCP service configuration in neutron regards this subnet isolated then (which is what I don't understand), therefore,
doesn't provide it with metadata route by default (force_metadata=False, enable_isolated_metadata=False).

It really seems like Neutron has a bug handling such scenario: it doesn't update DHCP service configuration when router is created for subnet.

Also, AFAIU, all the upstream Jenkins dsvm tempest jobs running test_dualnet* get metadata from config drive,
 that's possibly why they aren't affected.

[Ihar Hrachyshka (ihar-hrachyshka)]

Confirming. Once you kill dnsmasq and DHCP agent, and restart the agent, new configuration files are generated for the network that serve proper static routes pointing to router IP.

[Mark Rawlings (mark-rawlings)]

Simply because this appears to be happening on what would be the transition from a network appearing to be isolated, to it appearing to be non-isolated. Is there a potential relationship here to Bug: #1450548 ? That issue indicates issues for VMs caught in the transitions between isolation states.

Is a symptom that 'some' VM's created before 4 in you second sequence do not receive metadata, but VMs created after 4 do?
(I accept that I'm looking for more examples of the other issue and I'll back away peacefully if I'm off base.)

[Evgeny Antyshev (eantyshev)]

Strictly speaking, your last question has no answer: I was describing how networking is created, and it doesn't matter when VMs are connected (since it AFAIU doesn't trigger dhcp server reconfiguration).

But the above bug is about the same problem: detection of whether subnet is isolated is or not is done in unreliable fashion.

[Launchpad Janitor (janitor)]

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