Comment 5 for bug 1649845

Reviewed: https://review.openstack.org/412462
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=52f31b0ddbb978402f65850bf41ceb409c560d4f
Submitter: Jenkins
Branch: stable/newton

commit 52f31b0ddbb978402f65850bf41ceb409c560d4f
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
    (cherry picked from commit 5c8dffa7fb6c95a04a7b50c7d6e63c9a2729231b)