XDP i40e driver testing

[williamtu]

I observed 2 issues.

1. no xdp adjust head support

/**
 * i40e_xdp_setup - Add/remove an XDP program to a VSI
 * @vsi: the VSI to add the program
 * @prog: the XDP program
 **/
int i40e_xdp_setup(struct i40e_vsi *vsi, 
                          struct bpf_prog *prog)
{
        struct i40e_pf *pf = vsi->back;
        struct net_device *netdev = vsi->netdev;
        int i, frame_size = netdev->mtu + ETH_HLEN + ETH_FCS_LEN + VLAN_HLEN;
        bool need_reset;
        struct bpf_prog *old_prog;

        if (prog && prog->xdp_adjust_head)
                return -EOPNOTSUPP;

2. When dropping packets from XDP, it still counts as rx_receive++, not rx_dropped++
   return XDP_DROP

static bool i40e_run_xdp(struct i40e_ring *rx_ring,
                         struct i40e_rx_buffer *rx_buffer,
                         union i40e_rx_desc *rx_desc,
                         unsigned int size,
                         struct bpf_prog *xdp_prog)
{
...
        case XDP_DROP:
do_drop:
                if (likely(i40e_page_is_reusable(rx_buffer->page))) {
                        i40e_reuse_rx_page(rx_ring, rx_buffer);
                        rx_ring->rx_stats.page_reuse_count++;
                        break;
                }
                dma_unmap_page(rx_ring->dev, rx_buffer->dma, PAGE_SIZE,
                               DMA_FROM_DEVICE);
                __free_pages(rx_buffer->page, 0);
                break;
        default:
                bpf_warn_invalid_xdp_action(xdp_action);
                goto do_drop;
        }

        /* clear contents of buffer_info */
        rx_buffer->page = NULL;
        return true; /* Swallowed by XDP */

return true will add packets stats to txdp_consumed_bytes

static int i40e_clean_rx_irq(struct i40e_ring *rx_ring, int budget)
{
...
                skb = i40e_fetch_rx_buffer(rx_ring, rx_desc, skb,
                                           &xdp_consumed_bytes);
                if (xdp_consumed_bytes) {
                        cleaned_count++;

                        i40e_update_rx_next_to_clean(rx_ring);

                        total_rx_bytes += xdp_consumed_bytes;
                        total_rx_packets++;