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:[email protected]] Sent: Thursday, October 6, 2016 1:09 PM To: [email protected]; [email protected] 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 | | | ingress, IPv4, icmp, remote_ip_prefix: 20.20.20.0/24 | | sg2 | ingress, IPv4, 22/tcp, remote_ip_prefix: 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,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 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 / [email protected] reception: +421 2 206 65 114 / www.pantheon.sk [logo]
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