On Fri, May 14, 2021 at 10:16 AM Jason Wang <jasowang@xxxxxxxxxx> wrote: > > On Fri, May 14, 2021 at 4:35 AM Willem de Bruijn > <willemdebruijn.kernel@xxxxxxxxx> wrote: > > > > > > But surprisingly when TUN receives TUN_F_UFO it does not propagate it > > > > anywhere, there is no corresponding NETIF flag. > > > > > > (It looks like I drop the community and other ccs accidentally, adding > > > them back and sorry) > > > > > > Actually, there is one, NETIF_F_GSO_UDP. > > > > > > Kernel used to have NETIF_F_UFO, but it was removed due to bugs and > > > the lack of real hardware support. Then we found it breaks uABI, so > > > Willem tries to make it appear for userspace again, and then it was > > > renamed to NETIF_F_GSO_UDP. > > > > > > But I think it's a bug that we don't proporate TUN_F_UFO to NETIF > > > flag, this is a must for the driver that doesn't support > > > VIRTIO_NET_F_GUEST_UFO. I just try to disable all offloads and > > > mrg_rxbuf, then netperf UDP_STREAM from host to guest gives me bad > > > length packet in the guest. > > > > > > Willem, I think we probably need to fix this. > > > > We had to add back support for the kernel to accept UFO packets from > > userspace over tuntap. > > > > The kernel does not generate such packets, so a guest should never be > > concerned of receiving UFO packets. > > That's my feeling as well. > > But when I: > > 1) turn off all guest gso feature and mrg rx buffers, in this case > virtio-net will only allocate 1500 bytes for each packet > 2) doing netperf (UDP_STREAM) from local host to guest, I see packet > were truncated in the guest Is it possible that the virtio-net does not disable UFO offload? IMO it sets NETIF_F_LRO too bravely. > > > > > Perhaps i'm misunderstanding the problem here. > > > > I will re-check and get back to you. > (probably need a while since I will not be online for the next week). > > Thanks > _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
