[openstack-dev] [Openstack-security] Neutron security groups for L2 networks in Havana

Kanthi P pavuluri.kanthi at gmail.com
Fri Nov 8 09:45:54 UTC 2013


Hi Aaron,

Thanks for the reply !
Yes security groups are mapped to L3/L4 headers, these security rules are
being converted to iptables.

If we remove the subnet check, we will be able to launch instances without
ipaddress, they just have the mac address.
Users can configure their own ipaddress after they are booted.

If we use neutron security groups, it provides a default group (on port
basis) which blocks all ingress and allows all egress traffic.

Later users can configure security groups based on the ip address what they
provided to the vnics.

I mean to say, ports will have subnet but just that this subnet is not
known to openstack during the instance boot time.




On Fri, Nov 8, 2013 at 9:42 AM, Aaron Rosen <arosen at nicira.com> wrote:

>
>
>
> On Thu, Nov 7, 2013 at 12:23 PM, Kanthi P <pavuluri.kanthi at gmail.com>wrote:
>
>> Hi,
>>
>> I am trying to boot a VM which has a network without subnet in Havana,
>> but it throws an exception saying that subnet is mandatory if quantum
>> security groups are enabled.
>>
>> Here are the commands I used.
>>
>> neutron net-create testNet
>> neutron net-show testNet
>> +---------------------------+--------------------------------------+
>> | Field                     | Value                                |
>> +---------------------------+--------------------------------------+
>> | admin_state_up            | True                                 |
>> | id                        | 47208beb-2801-4729-bc7b-6532717232fc |
>> | name                      | testNet                              |
>> | provider:network_type     | local                                |
>> | provider:physical_network |                                      |
>> | provider:segmentation_id  |                                      |
>> | router:external           | False                                |
>> | shared                    | False                                |
>> | status                    | ACTIVE                               |
>> | subnets                   |                                      |
>> | tenant_id                 | b5b591dcda2645cd9d15a4fe3eb1b50d     |
>> +---------------------------+--------------------------------------+
>>
>> nova boot --flavor 2 --image 30c1984c-8a4f-4e3f-8c9a-7de0b321caa2 --nic
>> net-id=47208beb-2801-4729-bc7b-6532717232fc testServer1
>>
>> Here is the piece of code which generated this exception
>>
>> nova/network/neutronv2/api.py
>>
>>             if (security_groups and not (
>>                     network['subnets']
>>                     and network.get('port_security_enabled', True))):
>>
>>                 raise exception.SecurityGroupCannotBeApplied()
>>
>>
>> Can someone please explain why do we need this check?
>>
>
> Hi Kanthi,
>
> We need this check because because in order to enforce security groups the
> port needs to have an ip_address (i.e: network needs a subnet) since
> Security groups only map to L3/4 headers. Today, nova automatically adds a
> default security group to all instances when booted. Hopefully we can punt
> this task off to neutron in this release by moving the port-creation up on
> the stack to nova-api instead of nova-compute though this isn't the case
> right now.
>
> Aaron
>
>>
>> To my understanding subnet is used for two purposes in terms of security
>> groups
>> 1. To allow dhcp traffic if dhcp is enabled on the subnet, example given
>> below
>>         -A quantum-openvswi-i7bf776d2-b -s 192.168.1.3/32 -p udp -m udp
>> --sport 67 --dport 68 -j RETURN
>> 2. To avoid ip spoof
>>         -A quantum-openvswi-o7bf776d2-b ! -s 192.168.1.2/32 -j DROP
>>
>> Can we remove this so that we can have guests which has nic with just MAC
>> address, guest can configure its own ipaddress. Later if needed they can
>> enable their own security rules via quantum api.
>>
>> _______________________________________________
>> Openstack-security mailing list
>> Openstack-security at lists.openstack.org
>> http://lists.openstack.org/cgi-bin/mailman/listinfo/openstack-security
>>
>>
>
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