Re: [PATCH v2] network: add rule to nftables backend that zeroes checksum of DHCP responses

On Tue, Oct 29, 2024 at 01:09:00PM +0000, Andrea Bolognani wrote: > On Tue, Oct 29, 2024 at 12:46:55PM +0000, Daniel P. Berrangé wrote: > > A key difference that is probably relevant is that netbsd is > > using an e1000 NIC in QEMU, while openbsd is using a virtio-net > > NIC. At least when created by virt-manager. > > > > AFAIR, QEMU's magic checksum offload only happens for virtio-net, > > so presumably our rules are incompatible with non-virtio-net NICs > > in someway. > > Yes, that's it! The GNU/Hurd and Haiku guests are also using e1000, > since virtio drivers are not available there; moreover, if I switch a > random Linux guest from virtio-net to e1000 I can reproduce the issue > there as well. Incidentally, I think this has crossed the threshold where the cure is worse than the disease. We cannot ship the forthcoming libvirt release with a checksum "fix" that breaks all usage of NICs that aren't virtio-net, as that guarantees brokeness for all historical OS. If we can't quickly find a way to improve this, I think we need to revert (or disable) the checksum zero'ing fix for this release and spend more time investigating it.