Comment 2 for bug 1951816

Reviewed: https://review.opendev.org/c/openstack/neutron/+/822843
Committed: https://opendev.org/openstack/neutron/commit/4a06685098cc2e9b69c1b961eecef957314faf85
Submitter: "Zuul (22348)"
Branch: master

commit 4a06685098cc2e9b69c1b961eecef957314faf85
Author: yatinkarel <email address hidden>
Date: Thu Dec 23 21:22:35 2021 +0530

    [OVN] Correctly set dns_server in dhcpv4/v6 options

    When ovn/dns_servers consist of IPv6 dns nameservers,
    it was getting added to IPv4 dhcp options also, and due to
    this an invalid nameserver(last 4 octets of an IPv6 address)
    is set in the instances.

    This patch filters IPv4/IPv6 dns nameservers and set
    dhcpv4/dhcpv6 options accordingly.

    Also when dns_nameservers are not set for IPv6 subnets,
    get those from ovn/dns_servers config or system nameservers
    just like it's done with the IPv4 subnets. Updated
    get_system_dns_resolvers to pick both IPv4/IPv6 valid
    ips, this also requires bump of oslo.utils minimum version
    to 4.8.0 to use strict option for IPv4[1].

    Additionally fix some unit tests which were setting IPv4 dns
    nameservers on the IPv6 subnets, this is not allowed with api.

    [1] https://github.com/openstack/oslo.utils/commit/3288539

    Closes-Bug: #1951816
    Change-Id: I9f914e721201072e43a8c6c266ed97ca85fcc13d