On Tue, May 07, 2024 at 10:06:07AM -0400, Numan Siddique wrote: > On Tue, May 7, 2024 at 5:24 AM Felix Huettner via dev > <ovs-dev@openvswitch.org> wrote: > > > > On Mon, May 06, 2024 at 11:03:42PM -0400, Numan Siddique wrote: > > > On Mon, Apr 22, 2024 at 9:02 AM Felix Huettner via dev > > > <ovs-dev@openvswitch.org> wrote: > > > > > > > > In most cases IPv4 packets are routed only over other IPv4 networks and > > > > IPv6 packets are routed only over IPv6 networks. However there is no > > > > inherent reason for this limitation. Routing IPv4 packets over IPv6 > > > > networks just requires the router to contain a route for an IPv4 network > > > > with an IPv6 nexthop. > > > > > > > > This was previously prevented in OVN in ovn-nbctl and northd. By > > > > removing these filters the forwarding will work if the mac addresses are > > > > prepopulated. > > > > > > > > If the mac addresses are not prepopulated we will attempt to resolve > > > > them using > > > > the original address family of the packet and not the address family of > > > > the > > > > nexthop. This will fail and we will not forward the packet. > > > > > > > > > > Thanks for adding this feature. > > > > > > If I understand correctly from the above commit message about > > > prepopulation, is it expected that > > > CMS/admin needs to add a static mac binding entry in the OVN > > > Northbound 'Static_MAC_Binding' table > > > for this feature to work ? Please correct me if I'm wrong. > > > If this is the case, then it needs to be documented properly (perhaps > > > in ovn-nb.xml) > > > > no the limitation is only that the CMS must not set > > dynamic_neigh_routers to true on the Logical_Routers. > > > > If there are other reasons that cause OVN to send ARP request to lookup > > the nexthop of a route then these will have that issue as well. I am > > just no aware of any such reason. > > Thanks. I'm still not clear what happens if OVN doesn't know the > nexthop mac address. > What happens in that case ? Normally, OVN would generate ARP request > for the next hop IP and > learn the mac. What happens in the mix route case ? > > Numan
So lets assume you run an ipv4 prefix and route that over an ipv6 network. If you then reach the Logical_Router you will reach the arp action in S_ROUTER_IN_ARP_REQUEST (build_arp_request_flows_for_lrouter). This will be handled by the node executing that action as a packet-in to pinctrl_handle_arp which is here actually inappropriate. We would need to reach pinctrl_handle_nd_na as we need to send a neighbor discovery packet. It could be changed in northd.c when using an additional register bit to store the nexthop address family and then using that bit to figure out what address family we need to lookup against, instead of relying on the packet address family. However if we end up in pinctrl_handle_nd_na we seem to reuse the existing ipv4 packet and patch the Neighbor Discovery packet over it. I thought this causes the lookup then to fail, as the address families missmatch. However i am no longer sure of that explanation after writing this :) Thanks Felix _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev
