Comment 10 for bug 1861032

Reviewed: https://review.opendev.org/713290
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=03e88cd72a8f547133563e4a7a0f099c303be6b0
Submitter: Zuul
Branch: stable/train

commit 03e88cd72a8f547133563e4a7a0f099c303be6b0
Author: Harald Jensås <email address hidden>
Date: Fri Jan 17 12:29:10 2020 +0100

    DHCPv6 - Use addr6_list in dnsmasq

    Adds a new bool option dnsmasq_enable_addr6_list, when
    enabled configuration for dnsmasq will be created with a
    single dhcp-host entry specifying a list of ip addresses
    allocated for a port.

    Previously the dnsmasq dhcp-agent driver would write a
    separate dhcp-host entry for each fixed-ip of a port in
    the dnsmasq hosts file. The result of the previous
    behaviour is that dnsmasq will only use one of the config
    entries, i.e the first one matching the mac identifier.

    The trade-off is that only a single dns_assignment will
    be used for IPv6 addresses within the same subnet. (But
    in practice, this was always the case since only the
    first config entry would be used by dnsmasq.)

    Why is this neccecary:
      This is done to enable ironic provisioning over IPv6
      using DHCPv6-stateful. For background info, please
      read dnsmasq-discuss thread:
    http://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2020q1/thread.html#13671

    Conflicts:
        neutron/cmd/sanity/checks.py

    Closes-Bug: #1861032
    Change-Id: I833840e7daed2efa7efaece27cfd1ba28e0feb90
    (cherry picked from commit 592c2f8d91c3172c75cc5a2464350891b0a303f1)