[Bug 1069570] Re: 1 MAC Address, two IPs - DNS is "out of sync" with DHCP leases databases

[Matt Rae]

I see for precise-proposed, the patch is to add a 30 second lease for
pxe agents. This is resulting the lease during pxe being added to the
leases file with a 30 second expiration as expected, but the expiration
is not being honored.

We are seeing machines given the ip from the 30 second lease long after
it had expired.

It appears dhcpd is not respecting the 30 second lease and still giving
the wrong ip to nodes.

Example:

Below are the leases for a machine that came up with the wrong ip. The
lease for 172.21.66.24 is supposed to be for 30 seconds, but it appears
it was not being respected, since the node would come up with .24 after
rebooting long after the lease should be expired.

host 172.21.66.24 {
  dynamic;
  hardware ethernet 52:54:00:e3:1d:47;
  fixed-address 172.21.66.24;
}
lease 172.21.66.24 {
  starts 4 2013/09/05 01:40:28;
  ends 4 2013/09/05 01:40:58;
  tstp 4 2013/09/05 01:40:58;
  cltt 4 2013/09/05 01:40:28;
  binding state free;
  hardware ethernet 52:54:00:e3:1d:47;
  uid "\001RT\000\343\035G";
}
lease 172.21.66.29 {
  starts 4 2013/09/05 01:40:40;
  ends 4 2013/09/05 13:40:40;
  tstp 4 2013/09/05 13:40:40;
  cltt 4 2013/09/05 01:40:40;
  binding state active;
  next binding state free;
  hardware ethernet 52:54:00:e3:1d:47;
  client-hostname "maas-enlist";
}

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https://bugs.launchpad.net/bugs/1069570

Title:
  1 MAC Address, two IPs - DNS is "out of sync" with DHCP leases
  databases

Status in juju-core:
  Invalid
Status in MAAS:
  Fix Released
Status in MAAS 1.3 series:
  Fix Released
Status in “isc-dhcp” package in Ubuntu:
  Fix Released
Status in “maas” package in Ubuntu:
  Fix Released
Status in “isc-dhcp” source package in Precise:
  New
Status in “maas” source package in Precise:
  Fix Committed
Status in “isc-dhcp” source package in Raring:
  Fix Released
Status in “maas” source package in Raring:
  Confirmed
Status in “isc-dhcp” source package in Saucy:
  Fix Released
Status in “maas” source package in Saucy:
  Fix Released

Bug description:
  [Impact] 
   During my new tests, I tried to create two nodes simultaneously (both via DHCP + PXE, not by clicking "+Add node") and I hit this problem:

   Same MAC Address, two different IPs:

  # The format of this file is documented in the dhcpd.leases(5) manual page.
  # This lease file was written by isc-dhcp-4.2.4

  server-duid "\000\001\000\001\030\023\243\007RT\000\360\236\231";

  lease 192.168.50.1 {
    starts 5 2012/10/19 06:31:21;
    ends 5 2012/10/19 18:31:21;
    cltt 5 2012/10/19 06:31:21;
    binding state active;
    next binding state free;
    rewind binding state free;
    hardware ethernet 52:54:00:cd:6b:a2;
    uid "\001RT\000\315k\242";
  }
  lease 192.168.50.2 {
    starts 5 2012/10/19 06:31:43;
    ends 5 2012/10/19 18:31:43;
    cltt 5 2012/10/19 06:31:43;
    binding state active;
    next binding state free;
    rewind binding state free;
    hardware ethernet 52:54:00:cd:6b:a2;
    client-hostname "maas-enlist";
  }
  lease 192.168.50.2 {
    starts 5 2012/10/19 06:31:43;
    ends 5 2012/10/19 18:31:43;
    cltt 5 2012/10/19 06:31:43;
    binding state active;
    next binding state free;
    rewind binding state free;
    hardware ethernet 52:54:00:cd:6b:a2;
    client-hostname "maas-enlist";
  }
  host 192.168.50.1 {
    dynamic;
    hardware ethernet 52:54:00:cd:6b:a2;
    fixed-address 192.168.50.1;
  }
  lease 192.168.50.1 {
    starts 5 2012/10/19 06:31:21;
    ends 5 2012/10/19 06:34:48;
    tstp 5 2012/10/19 06:34:48;
    cltt 5 2012/10/19 06:31:21;
    binding state free;
    hardware ethernet 52:54:00:cd:6b:a2;
    uid "\001RT\000\315k\242";
  }

   1- DHCP gives address 192.168.50.1 to my machine on its first boot;

   2- After some time, I think that after some "reboots / elist /
  don'know for sure or even after commissioning" it; the IP have changed
  to 192.168.50.2 and got registered at DNS (192-168-50-2.test.com) that
  way;

   3- In the end of the day, after allocate it to root and start using
  it (the nodes), the DHCP gives again the IP 192.168.50.1 to my node,
  but DNS still remains with 192.158.50.2...

   ---

   My second node, first starts with 192.168.50.3, got registered with
  192.168.50.4 at DNS (and at MaaS Web GUI) but the DHCP finish with
  192.168.50.3...

  [Test Case]
  In a virtual environment: 
  - Add 2 nodes 
  - PXE boot the instances
  - verify dhcp leases have 1 mac address for 2 different IPs

  After applying latest debdiff alter the following:

     * modify /etc/maas/dhcpd.conf to include 'ignore-client-uids true'

  re-test by adding 2 additional nodes to verify the mac address is
  unique between both nodes.

  [Regression Potential]
  Low, as it adds another optional arguement to disable checking client-uids

  -- snip --

   I'll not try maas-dns again... Too many bugs...   =(

   I think that MaaS needs some kind of "glue" between DHCP and DNS to
  keep it in sync.

  Tks!
  Thiago

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