[openstack-dev] [OSSN 0020] Disassociating floating IPs does not terminate NAT connections with Neutron L3 agent

Nathan Kinder nkinder at redhat.com
Mon Sep 15 23:49:17 UTC 2014

Hash: SHA1

Disassociating floating IPs does not terminate NAT connections with
Neutron L3 agent
- ---

### Summary ###
Every virtual instance is automatically assigned a private IP address.
You may optionally assign public IP addresses to instances. OpenStack
uses the term "floating IP" to refer to an IP address (typically
public) that can be dynamically added to a running virtual instance.
The Neutron L3 agent uses Network Address Translation (NAT) to assign
floating IPs to virtual instances. Floating IPs can be dynamically
released from a running virtual instance but any active connections are
not terminated with this release as expected when using the Neutron L3

### Affected Services / Software ###
Neutron, Icehouse, Havana, Grizzly, Folsom

### Discussion ###
When creating a virtual instance, a floating IP address is not
allocated by default. After a virtual instance is created, a user can
explicitly associate a floating IP address to that instance. Users can
create connections to the virtual instance using this floating IP
address. Also, this floating IP address can be disassociated from any
running instance without shutting that instance down.

If a user initiates a connection using the floating IP address, this
connection remains alive and accessible even after the floating IP
address is released from that instance. This potentially violates
restrictive policies which are only being applied to new connections.
These policies are ignored for pre-existing connections and the virtual
instance remains accessible from the public network.

This issue is only known to affect Neutron when using the L3 agent.
Nova networking is not affected.

### Recommended Actions ###
There is unfortunately no easy way to detect which connections were
made over a floating IP address from a virtual instance, as the NAT is
performed at the Neutron router. The only safe way of terminating all
connections made over a floating IP address is to terminate the virtual
instance itself.

The following recommendations should be followed when using the Neutron
L3 agent:

- - Only attach a floating IP address to a virtual instance when that
instance should be accessible from networks outside the cloud.
- - Terminate or stop the instance along with disassociating the floating
IP address to ensure that all connections are closed.

The Neutron development team plans to address this issue in a future
version of Neutron.

### Contacts / References ###
This OSSN : https://wiki.openstack.org/wiki/OSSN/OSSN-0020
Original LaunchPad Bug : https://bugs.launchpad.net/neutron/+bug/1334926
OpenStack Security ML : openstack-security at lists.openstack.org
OpenStack Security Group : https://launchpad.net/~openstack-ossg
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