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[Adam Gandelman <1345947@xxxxxxxxxxxxxxxxxx>]

** Changed in: neutron/juno
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1345947

Title:
  DHCPNAK after neutron-dhcp-agent restart

Status in Grenade - OpenStack upgrade testing:
  In Progress
Status in OpenStack Neutron (virtual network service):
  Fix Released
Status in neutron icehouse series:
  Fix Released
Status in neutron juno series:
  Fix Released

Bug description:
  After rolling out a configuration change, we restarted neutron-dhcp-agent service, and then dnsmasq logs start flooding: DHCPNAK ... lease not found.
  DHCPNAK is replied by dnsmasq for all DHCPREQUEST renews from all VMs. However the MAC and IP pairs exist in host files.
  The log flooding increases when more and more VMs start renewing and they keep retrying until IP expire and send DHCPDISCOVER and reinit the IP.
  The log flooding gradually disappears when the VMs IP expire and send DHCPDISCOVER, to which dnsmasq respond DHCPOFFER properly.

  Analysis:  
  I noticed that option --leasefile-ro is used in dnsmasq command when started by neutron dhcp-agent. According to dnsmasq manual, this option should be used together with --dhcp-script to customize the lease database. However, the option --dhcp-script was removed when fixing bug 1202392.
  Because of this, dnsmasq will not save lease information in persistent storage, and when it is restarted, lease information is lost.

  Solution:
  Simply replace --leasefile-ro by --dhcp-leasefile=<path to dhcp runtime files>/lease would solve the problem. (patch attached)

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