OVN Neutron network MTU never get applied

[Lucas Alvares Gomes]

Reported at https://bugzilla.redhat.com/show_bug.cgi?id=1673690

Basically when you update the MTU from a Neutron network, that change is not being propagated to OVN. The reason is because OVN sets the MTU in the DHCP_Options table (which translates to Neutron subnets) and updating the network in Neutron does not triggers an update to the DHCP_Options table (only to the Logical_Switch one).

How to reproduce

1. Update the MTU in the Neutron network:

$ openstack network set --mtu 1400 TENANT_NET

2. Check the changes in OVN:

$ ovn-nbctl list DHCP_Options

You will see that it hasn't changed in OVN.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/645483
Committed: https://git.openstack.org/cgit/openstack/networking-ovn/commit/?id=1daffa9634a813ccbcf00a4c4c9dbd2c504d326d
Submitter: Zuul
Branch: master

commit 1daffa9634a813ccbcf00a4c4c9dbd2c504d326d
Author: Kamil Sambor <email address hidden>
Date: Fri Mar 22 07:53:47 2019 +0100

    Propagate mtu to all subnets

    In networking-ovn we map subnets to OVN DHCP_Options
    rows (where we store the MTU), but from neutron API perspective,
    the MTU is applied per network. So we need update all subnets
    thats belong to network to propagade correctly MTU for network.

    Closes-Bug: #1816449
    Change-Id: Ieddc16e607bccef84316f9ee908e884539c7ed39

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/stein
Review: https://review.opendev.org/669624

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/rocky
Review: https://review.opendev.org/669626

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/669624
Committed: https://git.openstack.org/cgit/openstack/networking-ovn/commit/?id=87ecdd8e0b3a7564ac9bc003debe0afad0782f46
Submitter: Zuul
Branch: stable/stein

commit 87ecdd8e0b3a7564ac9bc003debe0afad0782f46
Author: Kamil Sambor <email address hidden>
Date: Fri Mar 22 07:53:47 2019 +0100

    Propagate mtu to all subnets

    In networking-ovn we map subnets to OVN DHCP_Options
    rows (where we store the MTU), but from neutron API perspective,
    the MTU is applied per network. So we need update all subnets
    thats belong to network to propagade correctly MTU for network.

    Closes-Bug: #1816449
    Change-Id: Ieddc16e607bccef84316f9ee908e884539c7ed39
    (cherry picked from commit 1daffa9634a813ccbcf00a4c4c9dbd2c504d326d)

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/669626
Committed: https://git.openstack.org/cgit/openstack/networking-ovn/commit/?id=017c49ecd59a0173e6cbdbeb874a8673b38e46b4
Submitter: Zuul
Branch: stable/rocky

commit 017c49ecd59a0173e6cbdbeb874a8673b38e46b4
Author: Kamil Sambor <email address hidden>
Date: Fri Mar 22 07:53:47 2019 +0100

    Propagate mtu to all subnets

    In networking-ovn we map subnets to OVN DHCP_Options
    rows (where we store the MTU), but from neutron API perspective,
    the MTU is applied per network. So we need update all subnets
    thats belong to network to propagade correctly MTU for network.

    Closes-Bug: #1816449
    Change-Id: Ieddc16e607bccef84316f9ee908e884539c7ed39
    (cherry picked from commit 87ecdd8e0b3a7564ac9bc003debe0afad0782f46)

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/networking-ovn 7.0.0.0b1 development milestone.

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/networking-ovn 6.0.1 release.

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/networking-ovn 5.1.0 release.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: stable/queens
Review: https://review.opendev.org/710765

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.opendev.org/710765
Committed: https://git.openstack.org/cgit/openstack/networking-ovn/commit/?id=18e3d76fb8bcd803bb6b0f2fbff600044880abf9
Submitter: Zuul
Branch: stable/queens

commit 18e3d76fb8bcd803bb6b0f2fbff600044880abf9
Author: Kamil Sambor <email address hidden>
Date: Fri Mar 22 07:53:47 2019 +0100

    Propagate mtu to all subnets

    In networking-ovn we map subnets to OVN DHCP_Options
    rows (where we store the MTU), but from neutron API perspective,
    the MTU is applied per network. So we need update all subnets
    thats belong to network to propagade correctly MTU for network.

    Closes-Bug: #1816449
    Change-Id: Ieddc16e607bccef84316f9ee908e884539c7ed39
    (cherry picked from commit 87ecdd8e0b3a7564ac9bc003debe0afad0782f46)
    (cherry picked from commit 017c49ecd59a0173e6cbdbeb874a8673b38e46b4)

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/networking-ovn queens-eol release.