This changes the 'plug' and 'plug_new' interfaces of the
LinuxInterfaceDriver to accept an MTU argument. It then
updates the dhcp agent and l3 agent to pass the MTU that
is set on the network that the port belongs to. This allows
it to take into account the overhead calculations that are
done for encapsulation types.
It's necessary for the L3 agent to have the MTU because it
must recognize when fragmentation is needed so it can fragment
or generate an ICMP error.
It's necessary for the DHCP agent to have the MTU so it doesn't
interfere when it plugs into a bridge with a larger than 1500
MTU (the bridge would reduce its MTU to match the agent).
If an operator sets 'network_device_mtu', the value of that
will be used instead to preserve previous behavior.
Closes-Bug: #1549470
Closes-Bug: #1542108
Closes-Bug: #1542475
DocImpact: Neutron agents now support arbitrary MTU
configurations on each network (including
jumbo frames). This is accomplished by checking
the MTU value defined for each network on which
it is wiring VIFs.
Co-Authored-By: Matt Kassawara <mkassawara@gmail.com>
Change-Id: Ic091fa78dfd133179c71cbc847bf955a06cb248a
4df8d9a701