On 3/25/24 13:22, Aaron Conole wrote: > Eelco Chaudron <echau...@redhat.com> writes: > >> On 22 Mar 2024, at 20:06, Aaron Conole wrote: >> >>> Open vSwitch is originally intended to switch at layer 2, only dealing with >>> Ethernet frames. With the introduction of l3 tunnels support, it crossed >>> into the realm of needing to care a bit about some routing details when >>> making forwarding decisions. If an oversized packet would need to be >>> fragmented during this forwarding decision, there is a chance for pmtu >>> to get involved and generate a routing exception. This is gated by the >>> skbuff->pkt_type field. >>> >>> When a flow is already loaded into the openvswitch module this field is >>> set up and transitioned properly as a packet moves from one port to >>> another. In the case that a packet execute is invoked after a flow is >>> newly installed this field is not properly initialized. This causes the >>> pmtud mechanism to omit sending the required exception messages across >>> the tunnel boundary and a second attempt needs to be made to make sure >>> that the routing exception is properly setup. To fix this, we set the >>> outgoing packet's pkt_type to PACKET_OUTGOING, since it can only get >>> to the openvswitch module via a port device or packet command. >> >> Is this not a problem when the packet comes from the bridge port in the >> kernel? > > It very well may be an issue there as well, but the recommendation is to > operate with the bridge port down as far as I know, so I don't know if > this issue has been observed happening from the bridge port.
FWIW, bridge ports are typically used as an entry point for tunneled traffic so it can egress from a physical port attached to OVS. It means they are pretty much always UP in most common setups like OpenStack or ovn-kubernetes and handle a decent amount of traffic. They are also used to direct some other types of traffic to the host kernel. Unless I misunderstood which ports we're talking about here. Best regards, Ilya Maximets. _______________________________________________ dev mailing list d...@openvswitch.org https://mail.openvswitch.org/mailman/listinfo/ovs-dev
