Reported-At: https://bugs.launchpad.net/networking-ovn/+bug/1539347
Reported-By: na...@cn.ibm.com
Co-Authored-By: na...@cn.ibm.com,rua...@cn.ibm.com
---
openstack-neutron (CMS) allows the configuration of
"static-routes" on a router as shown below.
neutron router-update --route
destination=192.168.3.0/24,nexthop=192.168.1.100 router1
The static route gets implemented (in openstack) by adding a route in
the router-namespace using a command such as: ip route add to
destination-cidr via nexthop.
The next-hop is a port known to the CMS, and so, the CMS knows the
IP->mac mapping
of the nexthop port.
The usecases addressed by static route includes a VPN router. A VPN
router is a VM that has interfaces on a private network, and on a
provider network.
The static route allows other VMs on the private network to reach the
VPN-network via
the VPN router.
Example:
Private networks are 192.168.1.0/24 and 192.168.2.0/24
VPN-router has an interface (192.168.1.100) on private network
(192.168.1.0/24)
VPN connects to 192.168.3.0/24 over the provider network
the following static route is needed to allow VMs private networks
to reach the VPN network
destination=192.168.3.0/24, nexthop=192.168.1.100
An approach to implement static routes in OVN follows:
1) A new column called static route is added to the Logical Router table
* the static route column may in turn refer to a new
Logical_Router_Static_Route table whose columns include
destination, nexthop
OR for simplicity,
* the static route column may contain the static routes as a string
with formatting to denote separation - for example,
"destination=192.168.3.0/24,nexthop=192.168.1.100;destination=192.168.2.0/24,nexthop=10.0.1.4"
2) Based on the presence of the "static route" field in the logical
router, OVN northd programs a logical flow corresponding to the each
static route as follow:
actions : "ip.ttl--; reg0 = nexthop; next;"
external_ids : {stage-name=lr_in_ip_routing}
match : "ip4.dst == destination cidr"
pipeline : ingress
The lr_in_arp stage would have already have an arp-resolution-entry for
the nexthop since the nexthop (IP,Mac) is already added as a logical
port.
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