While using FreeBSD 11 on Google Compute engine creating a vpn with openvpn & l2tp (mpd), I notice that the network speed was extreamly slow, first I disable the TSO:
ifconfig vtnet0 -tso
But didn't work, therefore I disable the full vtnet checksum offload by adding this line to the /boot/loader.conf file:
hw.vtnet.csum_disable="1"
After doing that network speed boosted noticeable.
But wondering if this could raise other issues or is totally fine to disable it been an virtual environment?
In short, i don't see any downside in your case disabling CSUM.
That setting helps when you use a network card with support for hardware checksuming. On virtualized guests that means that if the host supports that your guest's virtual network driver will ask the host's driver to handle that job.
Disabling it means that your virtual CPU(s) will do that work.
As long as you're getting better performance just keep it off.