The outbound unicast traffic of VMS with security group enabled is broadcast

[weichun ren]

I encountered using openstack Security Group,If security groups are enabled for virtual nics on cloud hosts, The outgoing traffic of the VMS enabled in the security group should be unicast traffic, but it is eventually forwarded to all ports belong to the vlan on the ovs br-int bridge.

  The following is my debugging process in detail.
  The unicast packet sent by the remote virtual machine 172.83.160.63 to the local virtual machine 172.83.160.74 is passed to the br-ex->br-int-> VM,
  Because the security group is enabled on the VM NIC, The br-int cannot learn the entry whose port is patch-ex and mac address is vm2.
  Therefore those packets sent from vm1 to vm2 are broadcast in vlans because they fail to match mac address entries.

                          patch-int
     vm1 --- ovs(br-int) ------ ovs(br-ex)--- tor(physical switch) ......vm2
                   patch-ex

  The following is the ovs kernel flow table. The mac address of vm1 is fa:16:3e:6c:f3:09,The mac address of vm2 is fa:16:3e:d2:14:b5, the action of the flow table is multiple ports.
  recirc_id(0x314123),in_port(8),ct_state(-new+est-rel-rpl),eth(src=fa:16:3e:d2:14:b5,dst=fa:16:3e:6c:f3:09),eth_type(0x0800),ipv4(proto=6,frag=no),tcp(dst=2048/0xf800), packets:60100, bytes:14257193, used:2.035s, flags:P., actions:push_vlan(vid=5,pcp=0),3,pop_vlan,push_vlan(vid=1732,pcp=0),1,pop_vlan,7,9,10,15,5,18
     recirc_id(0x314123),in_port(8),ct_state(-new+est-rel+rpl-inv+trk),ct_zone(0x5),ct_mark(0),eth(src=fa:16:3e:d2:14:b5,dst=fa:16:3e:6c:f3:09),eth_type(0x0800),ipv4(frag=no), packets:1, bytes:54, used:2.037s, flags:., actions:push_vlan(vid=5,pcp=0),3,pop_vlan,push_vlan(vid=1732,pcp=0),1,pop_vlan,7,9,10,15,5,18

     After careful debugging analysis, the openflow action in the flow table 82 added by neutron is the VM port instead of normal.
  As a result, the ovs br-int bridge cannot learn the mac entry of vm2.

  table=82, priority=77,ct_state=+new-est,tcp,reg5=0x9,tp_dst=0x4/0xfffc actions=ct(commit,zone=NXM_NX_REG6[0..15]),output:9
     table=82, priority=77,ct_state=+est-rel-rpl,tcp,reg5=0x9,tp_dst=0x4/0xfffc actions=output:9

thank you

[LIU Yulong (dragon889)]

You may have a try to set explicitly_egress_direct=True for your ovs-agent.

See this for details:
https://docs.openstack.org/neutron/latest/contributor/internals/openvswitch_firewall.html#openflow-rules

And this is the original bug:
https://bugs.launchpad.net/neutron/+bug/1732067

[Lajos Katona (lajos-katona)]

@renwc: Do you have any feedback if with explicitly_egress_direct=True your issue is solved?