On Wed, Nov 26, 2025 at 5:46 AM Jon Kohler <[email protected]> wrote: > > Commit a2fb4bc4e2a6 ("net: implement virtio helpers to handle UDP > GSO tunneling.") inadvertently altered checksum offload behavior > for guests not using UDP GSO tunneling. > > Before, tun_put_user called tun_vnet_hdr_from_skb, which passed > has_data_valid = true to virtio_net_hdr_from_skb. > > After, tun_put_user began calling tun_vnet_hdr_tnl_from_skb instead, > which passes has_data_valid = false into both call sites. > > This caused virtio hdr flags to not include VIRTIO_NET_HDR_F_DATA_VALID > for SKBs where skb->ip_summed == CHECKSUM_UNNECESSARY. As a result, > guests are forced to recalculate checksums unnecessarily. > > Restore the previous behavior by ensuring has_data_valid = true is > passed in the !tnl_gso_type case, but only from tun side, as > virtio_net_hdr_tnl_from_skb() is used also by the virtio_net driver, > which in turn must not use VIRTIO_NET_HDR_F_DATA_VALID on tx. > > Cc: Paolo Abeni <[email protected]> > Fixes: a2fb4bc4e2a6 ("net: implement virtio helpers to handle UDP GSO > tunneling.") > Signed-off-by: Jon Kohler <[email protected]> > ---
Acked-by: Jason Wang <[email protected]> (Should this go -stable?) Thanks
