Restart dhcp-agent cause IPv6 vm can't renew IP address, will lost minutes or hours

[zhang sheng]

In this patch https://bugs.launchpad.net/neutron/+bug/1722126 when restart neutron-dhcp-agent, all ipv6 lease line will be removed.

problem step:
. set dhcp_lease_duration=200 in neutron.conf and restart neutron-dhcp-agent
. create ipv6 subnet
. boot a vm in this subnet, login and get an ipv6 address
. in /var/lib/neutron/dhcp/xxx-xxx-xxx/leases, you will find
   "1562308744 1045083158 100:200::1a ***"
. restart neutron-dhcp-agent, /var/lib/neutron/dhcp/xxx-xxx-xxx/leases file will be cleaned
. wait 200 seconds, the vm will lost ipv6 address

[Bernard Cafarelli (bcafarel)]

Marking incomplete for now, but potentially high. Can you give additional details on the setup, I suppose this is with DHCPv6-stateful? (as other states should not depend on leases file)

Also logs from client VM and DHCP agent when renewing the address would be interesting

I would expect the VM to ask for same previous IP and get it back, but let's see what dnsmasq/ipv6 folks say

[Brian Haley (brian-haley)]

Is the client trying to renew it's lease? Do you have logs or a tcpdump trace of that?

[zhang sheng (langyxxl)]

yes, this subnet is DHCPv6-stateful and connect to a router.
 1. neutron router-create r1
 2. neutron net-create n1
 3. neutron subnet-create --ip-version 6 --ipv6-ra-mode dhcpv6-stateful --ipv6-address-mode dhcpv6-stateful n1 8888::0/64
 4. neutron router-interface-add r1 subnetID

tcpdump from dhcp namespace, send 4 renew and 2 rebind but no dnsmasq send reply:
09:38:19.693546 fa:16:3e:d7:a3:19 > 33:33:00:01:00:02, ethertype IPv6 (0x86dd), length 170: fe80::f816:3eff:fed7:a319.dhcpv6-client > ff02::1:2.dhcpv6-server: dhcp6 renew
09:38:30.192265 fa:16:3e:d7:a3:19 > 33:33:00:01:00:02, ethertype IPv6 (0x86dd), length 170: fe80::f816:3eff:fed7:a319.dhcpv6-client > ff02::1:2.dhcpv6-server: dhcp6 renew
09:38:51.388599 fa:16:3e:d7:a3:19 > 33:33:00:01:00:02, ethertype IPv6 (0x86dd), length 170: fe80::f816:3eff:fed7:a319.dhcpv6-client > ff02::1:2.dhcpv6-server: dhcp6 renew
09:39:32.968586 fa:16:3e:d7:a3:19 > 33:33:00:01:00:02, ethertype IPv6 (0x86dd), length 170: fe80::f816:3eff:fed7:a319.dhcpv6-client > ff02::1:2.dhcpv6-server: dhcp6 renew
09:39:34.756542 fa:16:3e:d7:a3:19 > 33:33:00:01:00:02, ethertype IPv6 (0x86dd), length 152: fe80::f816:3eff:fed7:a319.dhcpv6-client > ff02::1:2.dhcpv6-server: dhcp6 rebind
09:39:45.292952 fa:16:3e:d7:a3:19 > 33:33:00:01:00:02, ethertype IPv6 (0x86dd), length 152: fe80::f816:3eff:fed7:a319.dhcpv6-client > ff02::1:2.dhcpv6-server: dhcp6 rebind

[Launchpad Janitor (janitor)]

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