** Changed in: neutron
Status: Incomplete => Invalid
** Changed in: neutron
Status: Invalid => Fix Released
** Changed in: tripleo
Status: Triaged => Fix Released
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https://bugs.launchpad.net/bugs/1271344
Title:
neutron-dhcp-agent doesn't hand out leases for recently used addresses
Status in OpenStack Neutron (virtual network service):
Fix Released
Status in tripleo - openstack on openstack:
Fix Released
Bug description:
Hi, last two days on ci-overcloud.tripleo.org, the neutron-dhcp-agent
has stopped answering properly for new VMs - new VMs don't get IP
addresses until neutron-dhcp-agent is restarted (we see cloud-init
waiting in nova console-log)
There is a bunch of rabbit disconnect messages in the log, but they
are not correlated with the fault.
Existing VMs can DHCP successfully, and the overlay network seems
fine.
I've checked the dhcp agent host file and it is being updated.
restarting the neutron-dhcp-agent 'fixes' the problem.
kill -HUPing the dnsmasqs doesn't seem to fix things
-> The issue is that a prior VM gets (say ) 192.168.1.25, then is shutdown.
-> we then issue 1.25 to a new VM, but the dnsmasq process still has 1.25 in
its in-memory leases table as being for the other adress.
- DHCPRELEASE *is* being issued, perhaps sporadic failures or some
other condition/
# WORKAROUNDS:
- restart the agent in a cronjob
- change reload_allocations to return self.restart(), avoiding the cache in
dnsmasq but introducing short interrupts in DHCP on each new VM deployed.
# POSSIBLE SOLUTIONS
- change dnsmasq to discard leases that were statically allocated and no
longer have that MAC address (e.g. to trust the config more)
- change neutron to only recycle port addresses when the discarded MAC has
been deleted more than (lease time).
- use dnsmasqs multiple-MAC feature to tell dnsmasq that a handover is
happening.[1]
- the lease change script is apparently called for all leases when SIGHUP is
received, so maybe we can terminate dead leases there? [2]
[1] " As a special case, in DHCPv4, it is possible to
include more than one hardware address. eg:
--dhcp-host=11:22:33:44:55:66,12:34:56:78:90:12,192.168.0.2
This allows an IP address to be associated with multiple hardware
addresses, and gives dnsmasq permission to abandon a DHCP lease to one of the
hardware addresses when another one asks for a lease. Beware that this is a
dangerous thing to do, it will only work reliably if only one of the
hardware addresses is active at any time and there is no way for dnsmasq to
enforce this. It is, for instance, useful to allocate a stable IP address to a
laptop which has both wired and wireless interfaces.
"
[2] "When it receives a SIGHUP, dnsmasq clears its cache and then re-
loads /etc/hosts and /etc/ethers and any file given by --dhcp-
hostsfile, --dhcp-optsfile or --addn-hosts. The dhcp lease change
script is called for all existing DHCP leases."
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