execute kuryr-cni failed if vif.network.mut is 0

[QingchuanHao]

If the MTU of the netowrk of interface is 0, "Netlink Error, invalid argument" will be raised, and kury-cni exits unexpectedly.

[Antoni Segura Puimedon (celebdor)]

what behavior would you expect in that case, @haoqingchuan-28?

[QingchuanHao (haoqingchuan-28)]

@Antoni Segura Puimedon, thank you for your question.

as far as I know, mtu of and interface to be 0 zero is invalid, but neutron do support this configuration and used as.

When mtu is 0,
1. dhcp-option-force of dnsmasq for is not set, and mtu of interface of vm is set to be 1500 by default
2. mtu of qvo-xxx and qvb-xxx is set to 1500, which is determined by configuration,network_device_mtu.

so I think we can set mtu of both veth devices to be 1500, and may I have your consideration?

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/552856

[Antoni Segura Puimedon (celebdor)]

We should set it dependant on the tunnelling for the net (1500 for vlan provided networks).

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/552856
Committed: https://git.openstack.org/cgit/openstack/kuryr-kubernetes/commit/?id=c00513bb6418b69e57cd4e9ae3823409f3574579
Submitter: Zuul
Branch: master

commit c00513bb6418b69e57cd4e9ae3823409f3574579
Author: QingchuanHao <email address hidden>
Date: Wed Mar 14 17:41:14 2018 +0800

    fix kury-cni exits unexpectedly when MTU of network is 0

    If the MTU of the netowrk of interface is 0,
    "Netlink Error, invalid argument" will be raised,
    and kury-cni exits unexpectedly.

    When mtu is 0,
    1. dhcp-option-force of dnsmasq for is not set,
       and mtu of interface of vm is set to be 1500 by default
    2. mtu of qvo-xxx and qvb-xxx is set to 1500,
       which is determined by configuration,network_device_mtu.

    Fix this by adding default network device MTU configuration,
    which is used instead if MTU of network is 0

    Change-Id: I7c1140b116aa6304aca13479a7d7eb82d828d16f
    Close-Bug: 1738812