Re: [PATCH net] virtio_net: reject XDP programs using header adjustment

On 16-12-20 04:30 AM, Jakub Kicinski wrote:

On Mon, Dec 19, 2016 at 5:50 PM, John Fastabend
[off-list ref] wrote:

quoted

On 16-12-19 07:05 AM, Jakub Kicinski wrote:

quoted

commit 17bedab27231 ("bpf: xdp: Allow head adjustment in XDP prog")
added a new XDP helper to prepend and remove data from a frame.
Make virtio_net reject programs making use of this helper until
proper support is added.

Signed-off-by: Jakub Kicinski <redacted>
---
 drivers/net/virtio_net.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
index 08327e005ccc..db761f37783e 100644
--- a/drivers/net/virtio_net.c
+++ b/drivers/net/virtio_net.c

@@ -1677,6 +1677,11 @@ static int virtnet_xdp_set(struct net_device *dev, struct bpf_prog *prog)
      u16 xdp_qp = 0, curr_qp;
      int i, err;

+     if (prog && prog->xdp_adjust_head) {
+             netdev_warn(dev, "Does not support bpf_xdp_adjust_head()\n");
+             return -EOPNOTSUPP;
+     }
+
      if (virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO4) ||
          virtio_has_feature(vi->vdev, VIRTIO_NET_F_GUEST_TSO6)) {
              netdev_warn(dev, "can't set XDP while host is implementing LRO, disable LRO first\n");

Acked-by: John Fastabend <redacted>

Thanks patch looks good. Alternatively we could push a "bug fix" to
support the adjust header feature depending on how DaveM and MST feel
about that. I don't have a strong opinion but I have the patch on my
queue it just needs some more testing.

Cool!  I thought to ask you what your plans are but then this patch is so
trivial I decided to just post it :) I'm perfectly happy with dropping it
for now and reposting after ~rc5 if needed.

Hi Jakub,

I just posted a RFC take a look if you get a chance. Notice though Jason
fixed up my linearize path a bunch so it will need to be pushed on top
of that series.

Thanks,
John