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Hi Kanthi,

The issue is that the nova-api says that by default every instance needs to
be in a default security group that blocks all ingress traffic from outside
and allows all ingress from instances that belong to the same security
group. If an instance does not have an ip address we are unable to enforce
the instance->instance communication of members that are part of the same
security group (or at least the iptables implementation in place doesn't).

There is an extension in neutron that implements port_security that allows
one to disable this so that one can do L2 networking as you want to. Though
unfortunately, this does not work correctly at this time with nova as
currently it's calling into neutron to create the security group and attach
it to the instance anways. See: https://bugs.launchpad.net/nova/+bug/1175464 .
I'm hoping to resolve this issue in the next few weeks.

Best,

Aaron


On Fri, Nov 8, 2013 at 1:45 AM, Kanthi P <pavuluri.kanthi at gmail.com> wrote:

> 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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