[OVN] packet drops when provider network MTU exceeds tenant network MTU
Affects | Status | Importance | Assigned to | Milestone | |
---|---|---|---|---|---|
neutron |
Confirmed
|
High
|
Unassigned |
Bug Description
At the moment, we have a provider network running 1500 MTU and then some tenant networks running 1450 MTU.
We've noticed that southbound traffic from the provider network to the tenant network will result in packets being dropped since the MTU is smaller.
So, the VM would not be able to get any traffic if the packet size > 1450, since the provider network operates at 1500 and hands over 1500 packets to the tap interface which gets dropped by the kernel:
[Wed Aug 23 14:33:19 2023] tapdf9341b0-6d: dropped over-mtu packet: 1456 > 1450
...
It seems that OVN should fragment packets when it notices the MTU of the target NAT is smaller than it's own, otherwise traffic goes into a nowhere.
OVN: 23.03.0
Note: the external (provider) network type is VLAN (as commented in IRC)