The OVN Northbound DB Schema at this point supports only a single route per
Logical Router Port.
Openstack/Neutron supports multiple routes per router interface and we need to
support this use case in the Neutron OVN Plugin.
To solve the multiple route (per router interface) issue while working within
this OVN NB model restriction, I created multiple lport and lrouter port for
each subnet supported by a router interface.
For e.g. let’s say a router interface supports both 192.168.1.0/24 and
2001:db8:cafe::/64 routes, I added 2 lport and 2 lrouter ports in the OVN NB.
Logical Router Table:
UUID-PA ["fa:16:3e:59:80:ad 192.168.1.1"] "port-1"
{router-port="UUID-RA"} ["fa:16:3e:59:80:ad"] router
UUID-PB ["fa:16:3e:59:80:ad 2001:db8:cafe::1"] "port-2"
{router-port="UUID-RB"} ["fa:16:3e:59:80:ad"] router
Logical Router Port Table:
UUID-RA "fa:16:3e:59:80:ad" "port-1" "192.168.1.1/24" []
UUID-RB "fa:16:3e:59:80:ad" "port-2" "2001:db8:cafe::1/64" []
Note that both ports (in both tables) have the same MAC corresponding to the
neutron router interface MAC.
This results in the following logical flow:
...
table=3(switch_in_l2_lkup), priority= 50, match=(eth.dst ==
fa:16:3e:59:80:ad), action=(outport = "port-2"; output;)
table=3(switch_in_l2_lkup), priority= 50, match=(eth.dst ==
fa:16:3e:59:80:ad), action=(outport = "port-1"; output;)
As we can see there are 2 conflicting/overlapping rules for the MAC in table 3
and the packet could be sent to the wrong output port.
To support the multiple route per interface feature, we need to propose that
OVN NB allow multiple routes per logical router port in ovs-dev or ovs-discuss.
Additionally it seems that the MAC must be unique in the Logical Router Table
per Logical Flow and this is not stated explicitly in the spec.
—Amitabha
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