On Tue, Nov 29, 2016 at 12:11:08PM -0800, John Fastabend wrote:
> This adds support for the XDP_TX action to virtio_net. When an XDP
> program is run and returns the XDP_TX action the virtio_net XDP
> implementation will transmit the packet on a TX queue that aligns
> with the current CPU that the XDP packet was processed on.
>
> Before sending the packet the header is zeroed. Also XDP is expected
> to handle checksum correctly so no checksum offload support is
> provided.
>
> Signed-off-by: John Fastabend <john.r.fastab...@intel.com>
> ---
> drivers/net/virtio_net.c | 59
> ++++++++++++++++++++++++++++++++++++++++++++--
> 1 file changed, 56 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index a1bfa99..9604e55 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -330,12 +330,40 @@ static struct sk_buff *page_to_skb(struct virtnet_info
> *vi,
> return skb;
> }
>
> +static void virtnet_xdp_xmit(struct virtnet_info *vi,
> + unsigned int qnum, struct xdp_buff *xdp)
> +{
> + struct send_queue *sq = &vi->sq[qnum];
> + struct virtio_net_hdr_mrg_rxbuf *hdr;
> + unsigned int num_sg, len;
> + void *xdp_sent;
> +
> + /* Free up any pending old buffers before queueing new ones. */
> + while ((xdp_sent = virtqueue_get_buf(sq->vq, &len)) != NULL) {
> + struct page *page = virt_to_head_page(xdp_sent);
> +
> + put_page(page);
> + }
> +
> + /* Zero header and leave csum up to XDP layers */
> + hdr = xdp->data;
> + memset(hdr, 0, vi->hdr_len);
> + hdr->hdr.gso_type = VIRTIO_NET_HDR_GSO_NONE;
> + hdr->hdr.flags = VIRTIO_NET_HDR_F_DATA_VALID;
Do we really want this?
This is CHECKSUM_UNNECESSARY.
Does not XDP pass checksummed packets?
> +
> + num_sg = 1;
> + sg_init_one(sq->sg, xdp->data, xdp->data_end - xdp->data);
> + virtqueue_add_outbuf(sq->vq, sq->sg, num_sg, xdp->data, GFP_ATOMIC);
This might fail. If it does, you want to at least free up the memory.
> + virtqueue_kick(sq->vq);
> +}
> +
> static u32 do_xdp_prog(struct virtnet_info *vi,
> struct bpf_prog *xdp_prog,
> struct page *page, int offset, int len)
> {
> int hdr_padded_len;
> struct xdp_buff xdp;
> + unsigned int qp;
> u32 act;
> u8 *buf;
>
> @@ -353,9 +381,15 @@ static u32 do_xdp_prog(struct virtnet_info *vi,
> switch (act) {
> case XDP_PASS:
> return XDP_PASS;
> + case XDP_TX:
> + qp = vi->curr_queue_pairs -
> + vi->xdp_queue_pairs +
> + smp_processor_id();
> + xdp.data = buf + (vi->mergeable_rx_bufs ? 0 : 4);
> + virtnet_xdp_xmit(vi, qp, &xdp);
> + return XDP_TX;
> default:
> bpf_warn_invalid_xdp_action(act);
> - case XDP_TX:
> case XDP_ABORTED:
> case XDP_DROP:
> return XDP_DROP;
> @@ -387,8 +421,16 @@ static struct sk_buff *receive_big(struct net_device
> *dev,
> if (xdp_prog) {
> u32 act = do_xdp_prog(vi, xdp_prog, page, 0, len);
>
> - if (act == XDP_DROP)
> + switch (act) {
> + case XDP_PASS:
> + break;
> + case XDP_TX:
> + rcu_read_unlock();
> + goto xdp_xmit;
> + case XDP_DROP:
> + default:
> goto err_xdp;
> + }
> }
> rcu_read_unlock();
>
> @@ -403,6 +445,7 @@ static struct sk_buff *receive_big(struct net_device *dev,
> err:
> dev->stats.rx_dropped++;
> give_pages(rq, page);
> +xdp_xmit:
> return NULL;
> }
>
> @@ -421,6 +464,8 @@ static struct sk_buff *receive_mergeable(struct
> net_device *dev,
> struct sk_buff *head_skb, *curr_skb;
> struct bpf_prog *xdp_prog;
>
> + head_skb = NULL;
> +
> rcu_read_lock();
> xdp_prog = rcu_dereference(rq->xdp_prog);
> if (xdp_prog) {
> @@ -432,8 +477,15 @@ static struct sk_buff *receive_mergeable(struct
> net_device *dev,
> }
>
> act = do_xdp_prog(vi, xdp_prog, page, offset, len);
> - if (act == XDP_DROP)
> + switch (act) {
> + case XDP_PASS:
> + break;
> + case XDP_TX:
> + goto xdp_xmit;
> + case XDP_DROP:
> + default:
> goto err_xdp;
> + }
> }
> rcu_read_unlock();
>
> @@ -510,6 +562,7 @@ static struct sk_buff *receive_mergeable(struct
> net_device *dev,
> err_buf:
> dev->stats.rx_dropped++;
> dev_kfree_skb(head_skb);
> +xdp_xmit:
> return NULL;
> }
>
