On Wed, May 06, 2020 at 02:16:32PM +0800, Jason Wang wrote: > We tried to reserve space for vnet header before > xdp.data_hard_start. But this is useless since the packet could be > modified by XDP which may invalidate the information stored in the > header and there's no way for XDP to know the existence of the vnet > header currently.
What do you mean? Doesn't XDP_PASS use the header in the buffer? > So let's just not reserve space for vnet header in this case. In any case, we can find out XDP does head adjustments if we need to. > Cc: Jesper Dangaard Brouer <bro...@redhat.com> > Signed-off-by: Jason Wang <jasow...@redhat.com> > --- > drivers/net/virtio_net.c | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c > index 11f722460513..98dd75b665a5 100644 > --- a/drivers/net/virtio_net.c > +++ b/drivers/net/virtio_net.c > @@ -684,8 +684,8 @@ static struct sk_buff *receive_small(struct net_device > *dev, > page = xdp_page; > } > > - xdp.data_hard_start = buf + VIRTNET_RX_PAD + vi->hdr_len; > - xdp.data = xdp.data_hard_start + xdp_headroom; > + xdp.data_hard_start = buf + VIRTNET_RX_PAD; > + xdp.data = xdp.data_hard_start + xdp_headroom + vi->hdr_len; > xdp.data_end = xdp.data + len; > xdp.data_meta = xdp.data; > xdp.rxq = &rq->xdp_rxq; > @@ -845,7 +845,7 @@ static struct sk_buff *receive_mergeable(struct > net_device *dev, > * the descriptor on if we get an XDP_TX return code. > */ > data = page_address(xdp_page) + offset; > - xdp.data_hard_start = data - VIRTIO_XDP_HEADROOM + vi->hdr_len; > + xdp.data_hard_start = data - VIRTIO_XDP_HEADROOM; > xdp.data = data + vi->hdr_len; > xdp.data_end = xdp.data + (len - vi->hdr_len); > xdp.data_meta = xdp.data; > -- > 2.20.1
