Re: vtnet rxcsum broken for forwarding RELENG_13 ?

On Mon, Apr 11, 2022 at 7:15 PM mike tancsa <mike@sentex.net> wrote:

> I was setting up a VM pf firewall and noticed I was not able to nat out
> for some reason. Looking at the pcap, it seems when the vm is in
> forwarding mode, I get tcp checksum errors. If I do a
>
> ifconfig vtnet1 -rxcsum
>
> ifconfig vtnet0 -rxcsum
>
> nat then seems to work fine
>
> The setup is a simple VM with the hypervisor libvirt/KVM ubuntu 20 LTS.
> Guest is RELENG_13 from Apr 11/2022. If I change to em nics in the VM,
> all is fine out of the box.
>
>
> I opened up https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=263229



Unless someone knows otherwise, I’ve been under the impression that PF — or
potentially any of the other FreeBSD firewalls (?), but I use PF — has been
“broken” in that regard on Linux KVM-based FreeBSD guests for years. As
such I’ve always needed to use csum_disable flags on the vtnet interfaces
or suffer *extremely* poor network performance, even for servers not doing
NAT forwarding.

E.g., see:

https://serverfault.com/questions/817664/slow-network-fixed-adding-hw-vtnet-csum-disable-1-what-are-the-posible-side-effe

https://forum.proxmox.com/threads/poor-virtio-network-performance-on-freebsd-guests.26289/



—Matt

<https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=263229>