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[OpenStack Infra <1722126@xxxxxxxxxxxxxxxxxx>]

Reviewed:  https://review.openstack.org/630951
Committed: https://git.openstack.org/cgit/openstack/neutron/commit/?id=4747de23d80ab32eea073846221adf94987f755b
Submitter: Zuul
Branch:    master

commit 4747de23d80ab32eea073846221adf94987f755b
Author: Rodolfo Alonso Hernandez <ralonsoh@xxxxxxxxxx>
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


** Changed in: neutron
       Status: In Progress => Fix Released

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https://bugs.launchpad.net/bugs/1722126

Title:
  Incorrect IPv6 lease entries cause DHCPNAKs from Dnsmasq in dual stack
  DHCPv6 stateful  network configuration

Status in neutron:
  Fix Released

Bug description:
  In a dual stack network with DHCPv6 stateful network configuration, Neutron DHCP Agent
  uses the IPv4 lease entry format to write IPv6 lease entries in the fake lease file
  used to bootstrap Dnsmasq after agent is restarted or migrated from one node to the
  other. As a result,  the lease file gets corrupted and overwritten by Dnsmasq after encountering the
  invalid IPv6 lease entries and this causes a DHCPNAK when IPv4 clients try to renew
  their leases with the Dnsmasq process.

  From the Dnsmasq mailing list, a lease entry for DHCPv4 consists of these fields
  seperated by spaces:

  - The expiration time (seconds since unix epoch) or duration
    (if dnsmasq is compiled with HAVE_BROKEN_RTC) of the lease.
    0 means infinite.

  - The link address, in format XX-YY:YY:YY[...], where XX is the ARP
    hardware type.  "XX-" may be omitted for Ethernet.

  - The IPv4 address

  - The hostname (sent by the client or assigned by dnsmasq)
    or '*' for none.

  - The client identifier (colon-separated hex bytes)
    or '*' for none.

  While a DHCPv6 lease entry has these fields:

  - The expiration time or duration

  - The IAID as a Big Endian decimal number, prefixed by T for
    IA_TAs (temporary addresses).

  - The IPv6 address

  - The hostname or '*'

  - The client DUID (colon-separated hex bytes) or '*' if unknown.[1]

  For DHCPv6, there must also be exactly one special entry indicating
  the DUID of the server.  This line contains two fields:

  - The string "duid".

  - The DUID of the server.

  See http://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2016q2/010595.html for
  more info about the discussion.

  Symptoms:
  ---------
  Currently, the _output_init_lease_file function in neutron/agent/linux/dhcp.py
  writes lease entries for both IPv4 and IPv6 like this:

  1506979604 fa:16:3e:07:b4:26 10.0.1.128 * *
  1506979604 fa:16:3e:07:b4:26 [2404:130:21:4000::24c] * *
  1506979604 fa:16:3e:20:20:a9 10.0.1.83 * *
  1506979604 fa:16:3e:26:cf:8a 10.0.1.135 * *

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