Update MTU on existing devices

[OpenStack Infra]

https://review.openstack.org/405532
Dear bug triager. This bug was created since a commit was marked with DOCIMPACT.
Your project "openstack/neutron" is set up so that we directly report the documentation bugs against it. If this needs changing, the docimpact-group option needs to be added for the project. You can ask the OpenStack infra team (#openstack-infra on freenode) for help if you need to.

commit 5c8dffa7fb6c95a04a7b50c7d6e63c9a2729231b
Author: Ihar Hrachyshka <email address hidden>
Date: Tue Nov 29 22:24:29 2016 +0000

    Update MTU on existing devices

    This patch makes OVS and Linuxbridge interface drivers to set MTU on
    plug() attempt if the device already exists. This helps when network MTU
    changes (which happens after some configuration file changes).

    This will allow to update MTU values on agent restart, without the need
    to bind all ports to new nodes, that would involve migrating agents. It
    will also help in case when you have no other nodes to migrate to (in
    single node mode).

    Both OVS and Linuxbridge interface drivers are updated.

    Other drivers (in-tree IVS as well as 3party drivers) will use the
    default set_mtu implementation, that only warns about the missing
    feature (once per process startup).

    DocImpact suggest to restart agents after MTU config changes instead of
              rewiring router/DHCP ports.

    Related: If438e4816b425e6c5021a55567dcaaa77d1fffff
    Related: If09eda334cddc74910dda7a4fb498b7987714be3
    Closes-Bug: #1649845
    Change-Id: I3c6d6cb55c5808facec38f87114c2ddf548f05f1

[John Davidge (john-davidge)]

The MTU Considerations page of the Networking Guide[1] will need to be updated.

[1] http://docs.openstack.org/newton/networking-guide/config-mtu.html

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/430212

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/430212
Committed: https://git.openstack.org/cgit/openstack/openstack-manuals/commit/?id=d7c4804de6fb945b35e4e1c2a586259a7908d886
Submitter: Jenkins
Branch: master

commit d7c4804de6fb945b35e4e1c2a586259a7908d886
Author: John Davidge <email address hidden>
Date: Tue Feb 7 11:34:01 2017 +0000

    [networking] MTU updates on l3-agent restart

    Note that new MTU calculations will propogate after l3-agent restart
    when using certain drivers.

    Change-Id: I5adc9b19cf9e9dfbcd221a3012839a4ffa68afde
    Closes-Bug: #1651126

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/openstack-manuals 15.0.0 release.