Hi We're currently trying to debug an issue we're seeing when using OpenStack with OVS 2.8.1 (see [0]).
When using GRE tunnels, we're seeing broken/slow performance due to what appears to be an incorrect MTU setting on the gre_sys device; for previous OVS releases (2.6.1 specifically but I think this applies back to 2.5.x as well) this device was created with an MTU of 65490; however under 2.8.1 it gets created with an MTU of 1472, which when used with GRE networks with larger MTU settings causes problems with fragmentation and broken path MTU discovery. I've tested under Linux 4.4 and 4.13 and see the problem with both kernels. Its possible to workaround the issue by setting the MTU on the gre_sys device directly, but this change will get reset back to 1472 on a restart of openvswitch. I know the mtu_request feature was introduced around 2.7.0 - groking the code I can't see where the MTU of this device is actually configured... Any help much appreciated James [0] https://bugs.launchpad.net/ubuntu/+source/openvswitch/+bug/1742505 _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
