[Bug 1927868] Re: vRouter not working after update to 16.3.1

[Jared Baker]

Our order of operations went as such:

- All packages get updated to latest available Ussuri (16.3.1) for Bionic via apt-get dist-upgrade
- Stop services (systemctl stop neutron-dhcp-agent; systemctl stop neutron-metadata-agent; systemctl stop neutron-ovs-cleanup; systemctl stop neutron-l3-agent; systemctl stop neutron-openvswitch-agent; systemctl stop neutron-server)
- Upgrade database (neutron-db-manage current; neutron-db-manage upgrade heads)
- Start services back up (systemctl start neutron-dhcp-agent; systemctl start neutron-metadata-agent; systemctl start neutron-ovs-cleanup; systemctl start neutron-l3-agent; systemctl start neutron-openvswitch-agent; systemctl start neutron-server)
- All L3 agents for all routers elect to be down
- Rebooted control plane several times while troubleshooting, L3 agents stay down
- Found that 16.3.2 was available on staging repository, installed it, all L3 agents go to standby
- Install 16.0.0 for Focal (all I could find during my scramble to fix the outage), L3 agents start to elect a master for each router
- Later that week, re-attempt 16.3.1, all L3 agents go to standby
- Find 16.2.0 for Bionic and downgrade to it, all L3 agents begin to elect masters

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Title:
  vRouter not working after update to 16.3.1

Status in neutron:
  New
Status in neutron package in Ubuntu:
  Triaged

Bug description:
  We run a juju managed Openstack Ussuri on Bionic. After updating
  neutron packages from 16.3.0 to 16.3.1 all virtual routers stopped
  working. It seems that most (not all) namespaces are created but have
  only the lo interface and sometime the ha-XYZ interface in DOWN state.
  The underlying tap interfaces are also in down.

  neutron-l3-agent has many logs similar to the following:
  2021-05-08 15:01:45.286 39411 ERROR neutron.agent.l3.ha_router [-] Gateway interface for router 02945b59-639b-41be-8237-3b7933b4e32d was not set up; router will not work properly

  and journal logs report at around the same time
  May 08 15:01:40 lar1615.srv-louros.grnet.gr neutron-keepalived-state-change[18596]: 2021-05-08 15:01:40.765 18596 INFO neutron.agent.linux.ip_lib [-] Failed sending gratuitous ARP to 62.62.62.62 on qg-5a6efe8c-6b in namespace qrouter-02945b59-639b-41be-8237-3b7933b4e32d: Exit code: 2; Stdin: ; Stdout: Interface "qg-5a6efe8c-6b" is down
  May 08 15:01:40 lar1615.srv-louros.grnet.gr neutron-keepalived-state-change[18596]: 2021-05-08 15:01:40.767 18596 INFO neutron.agent.linux.ip_lib [-] Interface qg-5a6efe8c-6b or address 62.62.62.62 in namespace qrouter-02945b59-639b-41be-8237-3b7933b4e32d was deleted concurrently

  
  The neutron packages installed are:

  ii  neutron-common                         2:16.3.1-0ubuntu1~cloud0                                    all          Neutron is a virtual network service for Openstack - common
  ii  neutron-dhcp-agent                     2:16.3.1-0ubuntu1~cloud0                                    all          Neutron is a virtual network service for Openstack - DHCP agent
  ii  neutron-l3-agent                       2:16.3.1-0ubuntu1~cloud0                                    all          Neutron is a virtual network service for Openstack - l3 agent
  ii  neutron-metadata-agent                 2:16.3.1-0ubuntu1~cloud0                                    all          Neutron is a virtual network service for Openstack - metadata agent
  ii  neutron-metering-agent                 2:16.3.1-0ubuntu1~cloud0                                    all          Neutron is a virtual network service for Openstack - metering agent
  ii  neutron-openvswitch-agent              2:16.3.1-0ubuntu1~cloud0                                    all          Neutron is a virtual network service for Openstack - Open vSwitch plugin agent
  ii  python3-neutron                        2:16.3.1-0ubuntu1~cloud0                                    all          Neutron is a virtual network service for Openstack - Python library
  ii  python3-neutron-lib                    2.3.0-0ubuntu1~cloud0                                       all          Neutron shared routines and utilities - Python 3.x
  ii  python3-neutronclient                  1:7.1.1-0ubuntu1~cloud0                                     all          client API library for Neutron - Python 3.x


  Downgrading to 16.3.0 resolves the issues.

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