Comment 11 for bug 2032817
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| Julia Kreger (juliaashleykreger) wrote Re: OVN: Distributed FIP packet drops when provider network MTU exceeds tenant network MTU | #11 |
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0e1f616
(Get the code!)
For what it is worth, I hit a similar issue attempting to set up an OVN job for ironic. Except the packet size on the far side of OVN's internals seemed to end up being 1430 bytes, as opposed to the configured interface sizes and MTUs of 1400 bytes.
Aug 21 15:44:55 np0035005087 kernel: ovs-node-0i1: dropped over-mtu packet: 1430 > 1400
Keep in mind, this was:
Devstack-host http service -> host kernel -> ip route to OVN router (also, local)-> OVN router -> OVN tenant networking -> OVS tap interface bridge and bridges connecting to static vtep (so we can packet capture) (all configured at 1400 bytes, afaik).
I'm assuming it silently dropped because the kernel had no IP interface to emit the packet on based on it's origin, which actually makes sense, albeit is annoying, and ended up getting dropped after OVN bits in the kernel networking itself handing off to the VM. I guess that is not *really* OVN's direct fault, but that there does seem to be a lack of awareness of the destination MTU.
With that, it also looks like the back side of the ovn code plugged into br-ex is on a 1500 bytes in my case, so it might be reasonable for it to assume it could send 1500 bytes not directly being on the same networking. Hope that makes sense and provides another mental data point.