Hi Ashwin,
So, basically, to get the ordered list within the SG, we can apply diff 
priorities for the rules also for the dataplane, right? At the same time, each 
SG will need a diff prio range, so that all rules within a given SG can be in 
consecutive priorities, whereas all rules within a diff SG, can be in a diff 
set of prios. This means we could break up the prio space into 2 sets, with 
MSBs getting assigned to SGs, and LSBs getting assigned to the rules themselves.
It reduces the number of rules/groups we can support overall though, to achieve 
this correctness.

Thanks,
daya

From: Aswin Suryanarayanan [mailto:asury...@redhat.com]
Sent: Friday, October 14, 2016 2:22 PM
To: Dayavanti Gopal Kamath <dayavanti.gopal.kam...@ericsson.com>
Cc: Somashekar Byrappa <somasheka...@altencalsoftlabs.com>; 
jozef.baci...@pantheon.tech; netvirt-...@lists.opendaylight.org; 
openflowplugin-dev@lists.opendaylight.org
Subject: Re: [netvirt-dev] [openflowplugin-dev] Need inputs on handling 
deletion of flows which have common attributes

Daya/Som,
We can think of deterministic implementation as well since it will solve 
problem we are facing now.  As mentioned in one of the solution of changing the 
priority based on SG can make it more deterministic. But we need to have 
priority associated with the SG itself as otherwise it will be challenging to 
identify first and last SG as we can add and remove them randomly. Since 
openstack does not provide any sequencing , we  require a logic which can 
associate the priority to the SG in netvirt.
This will not solve the issue Vishal mentioned where two SR( security rule )in 
a SG with one rule being the subset of other, we will not able to predict which 
will be hit first as all SR in a SG still have same priority.
Thanks
Aswin



On Thu, Oct 13, 2016 at 6:00 PM, Dayavanti Gopal Kamath 
<dayavanti.gopal.kam...@ericsson.com<mailto:dayavanti.gopal.kam...@ericsson.com>>
 wrote:
Hi som,
while SG may work this way, and ordering might not matter, as a service ACL 
should definitely implement it as an ordered list, to be more generic, and be 
able to support other classifier based features with minimal changes. There was 
goal for SGs at some point (long back, I think during G or H ), to add deny 
acl’s, but I don’t know the latest status.

Question for all, how does the netvirt community feel about changing SG impl to 
be an ordered list for Carbon.

Prio-wise, we do get some uncertainty between different SGs applied on a port, 
since Openstack does not provide any sequencing between SGs but that’s a 
problem for the operator to solve I think,the code should only ensure default 
SG has the lowest priority, and we could apply SGs in reduced priority order as 
and when they are applied, ie first group gets highest prio, and last group 
gets lowest prio.

Thanks,
daya



From: Somashekar B 
[mailto:somasheka...@altencalsoftlabs.com<mailto:somasheka...@altencalsoftlabs.com>]
Sent: Thursday, October 13, 2016 4:53 PM
To: Dayavanti Gopal Kamath 
<dayavanti.gopal.kam...@ericsson.com<mailto:dayavanti.gopal.kam...@ericsson.com>>;
 jozef.baci...@pantheon.tech<mailto:jozef.baci...@pantheon.tech>; 
netvirt-...@lists.opendaylight.org<mailto:netvirt-...@lists.opendaylight.org>; 
openflowplugin-dev@lists.opendaylight.org<mailto:openflowplugin-dev@lists.opendaylight.org>

Subject: RE: [netvirt-dev] [openflowplugin-dev] Need inputs on handling 
deletion of flows which have common attributes

Hi Daya,

Currently, all the flows corresponding to SG rules (irrespective of SG) have 
same priority.
One basic question here, does ordering at a SG level or SG rules level really 
matter? Becoz whatever we specify in SG rules are for allow traffic only. There 
are no deny rules. So I believe sequencing shouldn't matter unless if we are 
specifically looking for flow statistics.  Also there are no attributes in 
openstack which specifically mention about the sequence numbers. SG and rules 
are just passed as an array to ODL. So in case if we have to maintain 
sequencing, we will be following the array indexing.

With your inputs on making use of priority, I think we can have different 
priorities based on port + SG. This would create multiple flows on switch. So 
the issue doesn’t arise.
Hope SG priorities doesn’t matter.

Please share your thoughts.

Thanks,
Somashekar


From: Dayavanti Gopal Kamath [mailto:dayavanti.gopal.kam...@ericsson.com]
Sent: Thursday, October 13, 2016 2:18 PM
To: Somashekar Byrappa 
<somasheka...@altencalsoftlabs.com<mailto:somasheka...@altencalsoftlabs.com>>; 
jozef.baci...@pantheon.tech<mailto:jozef.baci...@pantheon.tech>; 
netvirt-...@lists.opendaylight.org<mailto:netvirt-...@lists.opendaylight.org>; 
openflowplugin-dev@lists.opendaylight.org<mailto:openflowplugin-dev@lists.opendaylight.org>
Subject: RE: [netvirt-dev] [openflowplugin-dev] Need inputs on handling 
deletion of flows which have common attributes

Hi som,
I would question the need for this usecase itself.

sg rules would be an ordered list, which need to be applied in sequence, so 
when these rules are programmed in the tables, we cannot have any interleaving 
between rules from different SGs. I think this is a contract that cannot be 
violated. For e.g
if SG1 has rule1, rule2, rule3 and SG2 has rule4,rule2, rule5. We need to make 
sure the tables contain 2 instances of rule 2, in both these ordered lists. The 
relative priority between all rules of SG1 and all rules of SG2 is a separate 
issue of course, and a separate discussion on whether these prios are 
deterministic.
Basic point is, we need to ensure the sequencing is intact within a group, 
either by adjusting the priorities or adding more specific match criteria, for 
different SGs.

2ndly, and more broadly, this does not sound typical to apply multiple SGs to 
the same VM, and additionally have the same rule in each such SG. This would 
call for some re-organization of the SG rules themselves, so from my 
perspective, we need not have huge design changes in the code to support such a 
use case.

Thanks,
daya

From: 
netvirt-dev-boun...@lists.opendaylight.org<mailto:netvirt-dev-boun...@lists.opendaylight.org>
 [mailto:netvirt-dev-boun...@lists.opendaylight.org] On Behalf Of Somashekar B
Sent: Thursday, October 13, 2016 12:49 PM
To: jozef.baci...@pantheon.tech<mailto:jozef.baci...@pantheon.tech>; 
netvirt-...@lists.opendaylight.org<mailto:netvirt-...@lists.opendaylight.org>; 
openflowplugin-dev@lists.opendaylight.org<mailto:openflowplugin-dev@lists.opendaylight.org>
Subject: Re: [netvirt-dev] [openflowplugin-dev] Need inputs on handling 
deletion of flows which have common attributes

Thanks Jozef for your inputs.
Maybe a common module needs to be written which can handle this scenario 
instead of every application module handling on their own.

Anymore inputs from others? Or else for time being, I will handle this in 
security groups module itself.

Thanks,
Somashekar

From: Jozef Bacigál [mailto:jozef.baci...@pantheon.tech]
Sent: Friday, October 7, 2016 3:58 PM
To: Somashekar B 
<somasheka...@altencalsoftlabs.com<mailto:somasheka...@altencalsoftlabs.com>>; 
netvirt-...@lists.opendaylight.org<mailto:netvirt-...@lists.opendaylight.org>; 
openflowplugin-dev@lists.opendaylight.org<mailto:openflowplugin-dev@lists.opendaylight.org>
Subject: RE: [openflowplugin-dev] Need inputs on handling deletion of flows 
which have common attributes

Hi Somashekar,

from Plugin POV it is quite impossible to handle this use case without a 
performance impact. On the device you can’t store two identical flows and you 
can’t store flow id as you mentioned below. But the plugins reconciliation 
working on change event so if you delete one flow on configuration it will be 
deleted on switch and reconciliation won’t start check all configuration unless 
you disconnect device. So yes, it would be better approach to handle this use 
case from the application side instead to let the plugin always check 
everything on each event.

Jozef

From: Somashekar B [mailto:somasheka...@altencalsoftlabs.com]
Sent: Thursday, October 6, 2016 1:09 PM
To: 
netvirt-...@lists.opendaylight.org<mailto:netvirt-...@lists.opendaylight.org>; 
openflowplugin-dev@lists.opendaylight.org<mailto:openflowplugin-dev@lists.opendaylight.org>
Subject: [openflowplugin-dev] Need inputs on handling deletion of flows which 
have common attributes

Hi All,

I am looking for all your inputs for the below issue.

Issue: Create multiple flows with different flowId, keeping rest of the 
attributes same.
In this case, there will be multiple flow entries in config DS, but a single 
flow on the switch.
When we delete one of this overlapping flow, flow gets deleted on the switch.

Use case:

We can associate multiple security groups to a VM from Openstack.
Each rule in the security group (SG) generally gets translated to a flow in one 
of the ACL tables (41/252) based on the direction (ingress/egress).
Let’s say we create multiple SGs having few overlapping rules (highlighted in 
yellow) among each other like below:

| sg1     | ingress, IPv4, 22/tcp, remote_ip_prefix: 
20.20.20.0/24<http://20.20.20.0/24>               |
|            | ingress, IPv4, icmp, remote_ip_prefix: 
20.20.20.0/24<http://20.20.20.0/24>                  |
| sg2     | ingress, IPv4, 22/tcp, remote_ip_prefix: 
20.20.20.0/24<http://20.20.20.0/24>               |


When we associate both SGs (sg1 and sg2) to a VM, ACL module creates three flow 
entries totally in config DS.
For the above two overlapping rules, two flow entries are created in config DS 
with different flowId, rest all the other attributes remains same.
This would result in a single flow on the switch as flowId is not a flow 
attribute on the switch.

cookie=0x6900000, duration=11.895s, table=252, n_packets=0, n_bytes=0, 
priority=61010,ct_state=+new+trk,tcp,metadata=0x10000000000/0x1fffff0000000000,nw_src=20.20.20.0/24<http://20.20.20.0/24>,tp_dst=22
 actions=ct(commit,zone=5000),resubmit(,220)
cookie=0x6900000, duration=75.237s, table=252, n_packets=0, n_bytes=0, 
priority=61010,ct_state=+new+trk,icmp,metadata=0x10000000000/0x1fffff0000000000,nw_src=20.20.20.0/24<http://20.20.20.0/24>
 actions=ct(commit,zone=5000),resubmit(,220)

Problem arises when we dissociate one of the SGs (let’s say, sg2) from the VM. 
In this case, we delete one of the overlapping flow from config DS.
This would result in deletion of flow from the switch. Even though there is 
another flow entry (having same data with different flow ID) in the config DS, 
this flow gets deleted from the switch.
This is how we generally handle all DCN/DTCN.

This is a common problem which might occur in other situations as well.

Question is how to handle this kind of scenario?
Which module should handle this? Plugin or applications?

In case, if we need to handle it from the applications side, we could think of 
below option:


1.       When adding a flow to config DS,

a.       Construct the flow id using the match criteria which would generate 
same flow ID for all the overlapping rules. So that only one flow will be 
created for all overlapping rules.

b.       With the constructed flowId, query config DS to check if flow already 
exists.

                                                               i.      If no, 
add this flow with flow name something like: ACL-<counter>. Counter would 
signify the number of overlapping flows configured.

                                                             ii.      If yes,  
update the flow name by incrementing the counter. Eg: ACL-2

2.       In case of deleting flow from config DS,

a.       Construct the flow ID as mentioned in 1.a

b.        With the constructed flowId, query config DS to check if flow already 
exists.

                                                               i.      If no, 
ignore.

                                                             ii.      If yes,  
check the counter value in the flow name (ACL-2), if its value is 1, delete the 
flow else decrement the counter and update the flow in config DS.

Cons of this approach:
                One additional read call to config DS during addition/deletion 
of every flow.

Please share your thoughts to handle it optimally.


Thanks,
Somashekar
JozefBacigál
Software Engineer

Sídlo / Mlynské Nivy 56 / 821 05 Bratislava / Slovakia
R&D centrum / Janka Kráľa 9 /  974 01 Banská Bystrica / Slovakia
+421 908 766 972 / 
jozef.baci...@pantheon.tech<mailto:jozef.baci...@pantheon.tech>
reception: +421 2 206 65 114 / www.pantheon.sk<http://www.pantheon.sk>



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