Comment 4 for bug 1832918

After the change ovs_use_veth=False we now have a tap device for the netns.

When we set charm MTU settings the tap device is set to jumbo frames (MTU 9000) we get truncated packets:

17:12:52.689179 IP truncated-ip - 464 bytes missing! (tos 0x0, ttl 64, id 38527, offset 0, flags [DF], proto TCP (6), length 1968)
    169.254.169.254.80 > 172.20.0.26.41838: Flags [P.], seq 0:1916, ack 1, win 219, options [nop,nop,TS val 2658401029 ecr 3658647933], length 1916: HTTP, length: 1916

Specifically with the HTTP request: http://169.254.169.254/openstack/2017-02-22/meta_data.json

It is not clear to me what is truncating the packets. In the netns the tap device states it has an MTU of 9000.

Manually setting the tap device MTU to 1500 seems to resolve this. Since we still have to manually setting the MTU of the dpdk-bond interfaces this is not that bad. But if the netns moves it will go back to 9000.