Set up for eBPF-based bridge

I finally succeeded in running netperf under this configuration.
To make the network (UDP/TCP) work correctly, I had to turn off *hardware checksum
offload" on guest's network interface with
$ ethtool --offload enp0s1 rx off tx off
(probably, "tx off" is mandatory.)

I'm afraid that this restriction might impose negative impacts on network performance
under heavy traffic with large data.
Though I have seen little difference in values in the table above as the test environment
is quite simple.