Requirements

1. Supports Connection Tracking feature using OVS

2. Separates routing flow rules from switching rules for simplicity

3. Supports complete tenant isolation

Limitations

A tenant cannot create more than one subnet with same IP address range even in different virtual network. However, the same subnet can be defined across tenants.

High level table design

• VNI tables
  - Tag the src VNI to the packet according to the in-port of the packet  

• ACL tables
  - Flow rules for Security Group
  - Flow rules for Connection Tracking : due to the architecture of the OVS connection tracking feature the ACL should be located to prior to the switching tables.

• Routing table
  - Check if routing is required by looking at the eth_dst. If not go to switching table.
  - Flow rules for routing between different subnets
  - Flow rules for external network connections, i.e rules to gateway nodes.

• Switching table
  - Flow rules to forwarding packets to VM ports
  - Flow rules to forwarding packets to VxLAN tunnel port.

Flow rule designs

• VNI tables
  - Tag the VNI of source IP address (by looking at the in-port ??)

  table=0,ip,in_port=1, actions=set_field:0x402->tun_id,goto_table:1

• ACI tables

table=2,ip,nw_src=10.10.0.10,nw_dst=10.10.0.12 actions=goto_table:4
table=3,in_port=4,ip,ct_state=+trk+new,nw_dst=10.10.0.13/32,action=ct(commit),goto_table:4

(3) Routing table

• Check if the eth_dst = virtual gateway mac (fa:00:00:00:00:00). If not, go to switching table.

• Allow packets with source VNI and src subnet and dest subnet connected via routers.

• Change the VNI using the destination if packets are from different subnet, which is because all of flow rules in the switching table forward packets using VNI of destination VM.

table=5,ip,tun_id=0x402,nw_src=10.10.0.0/24,dl_src=00:00:00:00:04:02,nw_dst=10.10.0.0/24, actions=set_field:0x402->tun_id, action=goto_table:5

(4) Switching table

• Sets the destination MAC address according to the destination IP address.

• It is required for routing, but we do not want to create another table only for the action.

• We believe that the additional action would not degrade the overall performance.

• However, if it does, it needs to moved to a separate routing table.

table=5,ip,nw_dst=10.10.0.13 actions=set_field:fa:16:3e:b8:92:fe->eth_dst

,output:5

table=5,ip,nw_dst=10.10.0.10 actions=set_field:10.0.0.166->tun_dst,output:1