creating ipv6 subnet on ipv6 vm will cause loss of connectivity

[Doug Wiegley]

The gate is all clogged, as any DSVM test using neutron (most of them), when it gets an IPv6 only OSIC node, seems to lose connectivity when devstack creates the internal neutron ipv6.

Not sure of root cause yet, but starting this bug here.

Please see starting at 01:48:

http://eavesdrop.openstack.org/irclogs/%23openstack-infra/%23openstack-infra.2016-08-24.log.html

[Doug Wiegley (dougwig)]

From clarks, see also: http://paste.openstack.org/show/562831/

[Armando Migliaccio (armando-migliaccio)]

Do we know how to trigger/repro this, exactly?

[Armando Migliaccio (armando-migliaccio)]

fwiw I witnessed the resets on stable/mitaka changes too.

[Armando Migliaccio (armando-migliaccio)]

fwiw I witnessed the resets on stable/liberty changes as well.

[Sean M. Collins (scollins)]

The failure is related to RFC 6204. If we are launching nodes on an IPv6 cloud that uses RA adverts, and we are forwarding packets from the virtual infrastructure that exists on the node, we need to use the special sysctl flag accept_ra, and set it to 2. By default, Linux when ipv6 forwarding is enabled, will ignore RAs from other devices. Check out the RFC for details. The accept_ra = 2 is the workaround used for customer premises equipment which recieves RAs from upstream sources (like their ISP) and forwards packets.

[Sean M. Collins (scollins)]

http://eavesdrop.openstack.org/irclogs/%23openstack-infra/%23openstack-infra.2016-08-23.log.html#t2016-08-23T23:49:55

carries over into the next day in the logs

http://eavesdrop.openstack.org/irclogs/%23openstack-infra/%23openstack-infra.2016-08-24.log.html

[Armando Migliaccio (armando-migliaccio)]

https://review.openstack.org/#/c/359490/

[Brian Haley (brian-haley)]

Forgot to put the bug number in that review, but I'm not touching it now, will update if I re-spin.

[Doug Wiegley (dougwig)]

359490 is now in the merge queue. Also not fixing the commit header.

[Armando Migliaccio (armando-migliaccio)]

I added the bug # in the stable backports commit message, if that's any help.

[Armando Migliaccio (armando-migliaccio)]

All patches have merged:

https://review.openstack.org/#/q/Ia044fff2a1731ab6c04f82aea47096b425e0c0a0,n,z

[Richard Theis (rtheis)]

This also impacted the networking-ovn native L3 job and was fixed by https://review.openstack.org/#/c/361420/.