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Diffstat (limited to 'tutorial/OVN-Tutorial.md')
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diff --git a/tutorial/OVN-Tutorial.md b/tutorial/OVN-Tutorial.md index 4fc06eb47..5dd5da21d 100644 --- a/tutorial/OVN-Tutorial.md +++ b/tutorial/OVN-Tutorial.md @@ -628,6 +628,87 @@ see it output to OpenFlow ports 5 and 6 only. $ ovn/env5/packet2.sh +6) Stateful ACLs +---------------- + +ACLs provide a way to do distributed packet filtering for OVN networks. One +example use of ACLs is that OpenStack Neutron uses them to implement security +groups. ACLs are implemented using conntrack integration with OVS. + +Start with a simple logical switch with 2 logical ports. + +[View ovn/env6/setup.sh][env6setup]. + + $ ovn/env6/setup.sh + +A common use case would be the following policy applied for `sw0-port1`: + +* Allow outbound IP traffic and associated return traffic. +* Allow incoming ICMP requests and associated return traffic. +* Allow incoming SSH connections and associated return traffic. +* Drop other incoming IP traffic. + +The following script applies this policy to our environment. + +[View ovn/env6/add-acls.sh][env6acls]. + + $ ovn/env6/add-acls.sh + +We can view the configured ACLs on this network using the `ovn-nbctl` command. + + $ ovn-nbctl acl-list sw0 + from-lport 1002 (inport == “sw0-port1” && ip) allow-related + to-lport 1002 (outport == “sw0-port1” && ip && icmp) allow-related + to-lport 1002 (outport == “sw0-port1” && ip && tcp && tcp.dst == 22) allow-related + to-lport 1001 (outport == “sw0-port1” && ip) drop + +Now that we have ACLs configured, there are new entries in the logical flow +table in the stages `switch_in_pre_acl`, switch_in_acl`, `switch_out_pre_acl`, +and `switch_out_acl`. + + $ ovn-sbctl lflow-list + +Let’s look more closely at `switch_out_pre_acl` and `switch_out_acl`. + +In `switch_out_pre_acl`, we match IP traffic and put it through the connection +tracker. This populates the connection state fields so that we can apply policy +as appropriate. + + table=0(switch_out_pre_acl), priority= 100, match=(ip), action=(ct_next;) + table=1(switch_in_pre_acl), priority= 0, match=(1), action=(next;) + +In `switch_out_acl`, we allow packets associated with existing connections. We +drop packets that are deemed to be invalid (such as non-SYN TCP packet not +associated with an existing connection). + + table=1(switch_out_acl), priority=65535, match=(!ct.est && ct.rel && !ct.new && !ct.inv), action=(next;) + table=1(switch_out_acl), priority=65535, match=(ct.est && !ct.rel && !ct.new && !ct.inv), action=(next;) + table=1(switch_out_acl), priority=65535, match=(ct.inv), action=(drop;) + +For new connections, we apply our configured ACL policy to decide whether to +allow the connection or not. In this case, we’ll allow ICMP or SSH. Otherwise, +we’ll drop the packet. + + table=1(switch_out_acl), priority= 2002, match=(ct.new && (outport == “sw0-port1” && ip && icmp)), action=(ct_commit; next;) + table=1(switch_out_acl), priority= 2002, match=(ct.new && (outport == “sw0-port1” && ip && tcp && tcp.dst == 22)), action=(ct_commit; next;) + table=1(switch_out_acl), priority= 2001, match=(outport == “sw0-port1” && ip), action=(drop;) + +When using ACLs, the default policy is to allow and track IP connections. Based +on our above policy, IP traffic directed at `sw0-port1` will never hit this flow +at priority 1. + + table=1(switch_out_acl), priority= 1, match=(ip), action=(ct_commit; next;) + table=1(switch_out_acl), priority= 0, match=(1), action=(next;) + +Note that conntrack integration is not yet supported in ovs-sandbox, so the +OpenFlow flows will not represent what you’d see in a real environment. The +logical flows described above give a very good idea of what the flows look like, +though. + +[This blog post][openstack-ovn-acl-blog] discusses OVN ACLs from an OpenStack +perspective and also provides an example of what the resulting OpenFlow flows +look like. + [ovn-architecture(7)]:http://openvswitch.org/support/dist-docs/ovn-architecture.7.html [Tutorial.md]:./Tutorial.md [ovn-nb(5)]:http://openvswitch.org/support/dist-docs/ovn-nb.5.html @@ -659,3 +740,6 @@ see it output to OpenFlow ports 5 and 6 only. [env5setup]:./ovn/env5/setup.sh [env5packet1]:./ovn/env5/packet1.sh [env5packet2]:./ovn/env5/packet2.sh +[env6setup]:./ovn/env6/setup.sh +[env6acls]:./ovn/env6/add-acls.sh +[openstack-ovn-acl-blog]:http://blog.russellbryant.net/2015/10/22/openstack-security-groups-using-ovn-acls/ |