Race condition for auto assigned addresses in Nova networking

[Phil Day]

The allocate_for_instance() code in Nova networking FlatDHCPManager for auto assigning a floating IP splits the allocation and setting of the auto assigned column into two steps:

 if CONF.auto_assign_floating_ip:
            # allocate a floating ip
            floating_address = self.allocate_floating_ip(context, project_id,
                True)
            LOG.debug(_("floating IP allocation for instance "
                        "|%(floating_address)s|") % locals(),
                        instance_uuid=instance_uuid, context=context)
            # set auto_assigned column to true for the floating ip
            self.db.floating_ip_set_auto_assigned(context, floating_address)

In the (very) short window between allocation and floating_ip_set_auto_assigned the about to be auto assigned address becomes visible to the user, and if they're quick enough they can de-allocate it just before the allocate_for_instance call goes ahead and sets the auto assigned flag and associates it to the fixed IP of the instance, leaving the DB in an inconsistent state (the address is in use but not allocated to a project).

The fix would be to set the auto_assigned attribute as part of the initial allocation.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/37842

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/37842
Committed: http://github.com/openstack/nova/commit/9c328a1128278c9e11c5ccfeac4e7a1f086b49f4
Submitter: Jenkins
Branch: master

commit 9c328a1128278c9e11c5ccfeac4e7a1f086b49f4
Author: Jiajun Liu <email address hidden>
Date: Tue Jul 30 10:39:15 2013 +0800

    handle auto assigned flag on allocate floating ip

    Set auto_assigned field to the right value on allocating floating ip to
    avoid potential race condition in nova-network.

    fix bug 1190585

    Change-Id: I8ee34924439d2a29b1b5a966b92856e63cc1afdc