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[Miguel Lavalle <2069482@xxxxxxxxxxxxxxxxxx>]

Public bug reported:

VMs cannot access the metadata service when connected to a network with
only IPv6 subnets.

Neutron branch: master

Steps to reproduce:

1) Create a network with a single IPv6 subnet:

$ openstack network create ipv6-net-dhcpv6-slaac
$ openstack subnet create --subnet-range fdba:e036:9e22::/64 --ip-version 6 --gateway dba:e036:9e22::1 --ipv6-ra-mode slaac --ipv6-address-mode slaac --network ipv6-net-dhcpv6-slaac ipv6-subnet-dhcpv6-slaac

2) Create a VM using this network:

$ openstack server create --key-name my_key --flavor m1.small --image
ubuntu-20.04-minimal-cloudimg-amd64 --network ipv6-net-dhcpv6-slaac
--security-group sg1 my-vm-slaac

3) The following message is added to the metadata agent log file:

Jun 14 22:00:32 central neutron-ovn-metadata-agent[89379]: DEBUG
neutron.agent.ovn.metadata.agent [-] No valid VIF ports were found for
network 191a0539-edbc-4037-b973-dfa77e3208f6, tearing the namespace down
if needed {{(pid=89379) _get_provision_params
/opt/stack/neutron/neutron/agent/ovn/metadata/agent.py:720}}

which is produced here:

https://github.com/openstack/neutron/blob/79b2d709c80217830fed8ad73dcf6fbd3eea91b4/neutron/agent/ovn/metadata/agent.py#L719-L723

4) When an IPv4 subnet is added to the network and the VM is recreated,
the metadata service is accessible to it over IPv6:

$ openstack subnet create --network ipv6-net-dhcpv6-slaac ipv4-subnet-dhcpv6-slaac --subnet-range 10.2.0.0/24
$ openstack server delete my-vm-slaac
$ openstack server create --key-name my_key --flavor m1.small --image ubuntu-20.04-minimal-cloudimg-amd64 --network ipv6-net-dhcpv6-slaac --security-group sg1 my-vm-slaac

>From the VM:

ubuntu@my-vm-slaac:~$ curl http://[fe80::a9fe:a9fe%ens3]
1.0
2007-01-19
2007-03-01
2007-08-29
2007-10-10
2007-12-15
2008-02-01
2008-09-01
2009-04-04
latest

ubuntu@my-vm-slaac:~$ curl http://[fe80::a9fe:a9fe%ens3]/openstack
2012-08-10
2013-04-04
2013-10-17
2015-10-15
2016-06-30
2016-10-06
2017-02-22
2018-08-27
2020-10-14
latest


How reproducible: 100%

** Affects: neutron
     Importance: High
     Assignee: Miguel Lavalle (minsel)
         Status: New

** Changed in: neutron
   Importance: Undecided => High

** Changed in: neutron
     Assignee: (unassigned) => Miguel Lavalle (minsel)

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https://bugs.launchpad.net/bugs/2069482

Title:
  [OVN] VMs cannot access metadata when connected to a network with only
  IPv6 subnets

Status in neutron:
  New

Bug description:
  VMs cannot access the metadata service when connected to a network
  with only IPv6 subnets.

  Neutron branch: master

  Steps to reproduce:

  1) Create a network with a single IPv6 subnet:

  $ openstack network create ipv6-net-dhcpv6-slaac
  $ openstack subnet create --subnet-range fdba:e036:9e22::/64 --ip-version 6 --gateway dba:e036:9e22::1 --ipv6-ra-mode slaac --ipv6-address-mode slaac --network ipv6-net-dhcpv6-slaac ipv6-subnet-dhcpv6-slaac

  2) Create a VM using this network:

  $ openstack server create --key-name my_key --flavor m1.small --image
  ubuntu-20.04-minimal-cloudimg-amd64 --network ipv6-net-dhcpv6-slaac
  --security-group sg1 my-vm-slaac

  3) The following message is added to the metadata agent log file:

  Jun 14 22:00:32 central neutron-ovn-metadata-agent[89379]: DEBUG
  neutron.agent.ovn.metadata.agent [-] No valid VIF ports were found for
  network 191a0539-edbc-4037-b973-dfa77e3208f6, tearing the namespace
  down if needed {{(pid=89379) _get_provision_params
  /opt/stack/neutron/neutron/agent/ovn/metadata/agent.py:720}}

  which is produced here:

  https://github.com/openstack/neutron/blob/79b2d709c80217830fed8ad73dcf6fbd3eea91b4/neutron/agent/ovn/metadata/agent.py#L719-L723

  4) When an IPv4 subnet is added to the network and the VM is
  recreated, the metadata service is accessible to it over IPv6:

  $ openstack subnet create --network ipv6-net-dhcpv6-slaac ipv4-subnet-dhcpv6-slaac --subnet-range 10.2.0.0/24
  $ openstack server delete my-vm-slaac
  $ openstack server create --key-name my_key --flavor m1.small --image ubuntu-20.04-minimal-cloudimg-amd64 --network ipv6-net-dhcpv6-slaac --security-group sg1 my-vm-slaac

  From the VM:

  ubuntu@my-vm-slaac:~$ curl http://[fe80::a9fe:a9fe%ens3]
  1.0
  2007-01-19
  2007-03-01
  2007-08-29
  2007-10-10
  2007-12-15
  2008-02-01
  2008-09-01
  2009-04-04
  latest

  ubuntu@my-vm-slaac:~$ curl http://[fe80::a9fe:a9fe%ens3]/openstack
  2012-08-10
  2013-04-04
  2013-10-17
  2015-10-15
  2016-06-30
  2016-10-06
  2017-02-22
  2018-08-27
  2020-10-14
  latest

  
  How reproducible: 100%

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