Comment 10 for bug 1722126

Reviewed: https://review.openstack.org/633201
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=828daf9f133c51fb18b0147760c5a2d4f3b9f663
Submitter: Zuul
Branch: stable/queens

commit 828daf9f133c51fb18b0147760c5a2d4f3b9f663
Author: Rodolfo Alonso Hernandez <email address hidden>
Date: Mon Jan 14 18:47:21 2019 +0000

    Remove IPv6 addresses in dnsmasq leases file

    IPv6 address format in dnsmasq leases file is incorrect (correct format
    is described in bug description). This bad formatting generates the
    following error when initializing dnsmasq:
      dnsmasq[20603]: failed to parse lease database, invalid line: \
        1547121093 fa:16:3e:a0:3a:9a [fd5b:1fd5:8295:5339::43] * ...

    This patch removes the IPv6 addresses from the leases file, as proposed
    in the bug, because the DHCP agent does not have the IAID (identity
    association identifier) of each IPv6 address assigned.

    In case of agent restart, dnsmasq won't have any IPv6 address in the
    leases file, but the hosts file and the additional hosts file will
    contain all MAC/IPv6 previous assignations. When the IPv6 client sends
    a DHCPDISCOVER, dnsmasq will offer the same IPv6 address to this client.
    At the same time, the client will request to the server the same address:
      DHCPDISCOVER(tap2c14823a-e6) fa:16:3e:54:c6:8e
      DHCPOFFER(tap2c14823a-e6) fd5b:1fd5:8295:5339::43 fa:16:3e:54:c6:8e
      DHCPREQUEST(tap2c14823a-e6) fd5b:1fd5:8295:5339::43 fa:16:3e:54:c6:8e
      DHCPACK(tap2c14823a-e6) fd5b:1fd5:8295:5339::43 fa:16:3e:54:c6:8e \
        host-fd5b-1fd5-8295-5339--43

    Once dnsmasq updates the leases database, rewrites the leases file with the
    new IPv6 address (including the IAID) and the server DUID (if not present).

    Change-Id: Ib1b2f284ab81f1c4af7b08b5257b45a3f6e79c3e
    Closes-Bug: #1722126
    (cherry picked from commit 4747de23d80ab32eea073846221adf94987f755b)