[PATCH RFC 5/9] veth: Handle xdp_frame in xdp napi ring

[Toshiaki Makita]

From: Toshiaki Makita <makita.toshi...@lab.ntt.co.jp>

This is preparation for XDP TX and ndo_xdp_xmit.

Now the napi ring accepts both skb and xdp_frame. When xdp_frame is
enqueued, skb will not be allocated until XDP program on veth returns
PASS. This will speedup the XDP processing when ndo_xdp_xmit is
implemented and xdp_frame is enqueued by the peer device.

Signed-off-by: Toshiaki Makita <makita.toshi...@lab.ntt.co.jp>
---
 drivers/net/veth.c | 79 ++++++++++++++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 77 insertions(+), 2 deletions(-)

diff --git a/drivers/net/veth.c b/drivers/net/veth.c
index 452771f31c30..89c91c1c9935 100644
--- a/drivers/net/veth.c
+++ b/drivers/net/veth.c
@@ -27,6 +27,7 @@
 #define DRV_NAME       "veth"
 #define DRV_VERSION    "1.0"
 
+#define VETH_XDP_FLAG          0x1UL
 #define VETH_RING_SIZE         256
 #define VETH_XDP_HEADROOM      (XDP_PACKET_HEADROOM + NET_IP_ALIGN)
 
@@ -48,6 +49,16 @@ struct veth_priv {
        struct xdp_rxq_info     xdp_rxq;
 };
 
+static bool veth_is_xdp_frame(void *ptr)
+{
+       return (unsigned long)ptr & VETH_XDP_FLAG;
+}
+
+static void *veth_ptr_to_xdp(void *ptr)
+{
+       return (void *)((unsigned long)ptr & ~VETH_XDP_FLAG);
+}
+
 /*
  * ethtool interface
  */
@@ -117,7 +128,14 @@ static void veth_ptr_free(void *ptr)
 {
        if (!ptr)
                return;
-       dev_kfree_skb_any(ptr);
+
+       if (veth_is_xdp_frame(ptr)) {
+               struct xdp_frame *frame = veth_ptr_to_xdp(ptr);
+
+               xdp_return_frame(frame);
+       } else {
+               dev_kfree_skb_any(ptr);
+       }
 }
 
 static void veth_xdp_flush(struct veth_priv *priv)
@@ -263,6 +281,60 @@ static struct sk_buff *veth_build_skb(void *head, int 
headroom, int len,
        return skb;
 }
 
+static struct sk_buff *veth_xdp_rcv_one(struct veth_priv *priv,
+                                       struct xdp_frame *frame)
+{
+       struct bpf_prog *xdp_prog;
+       unsigned int headroom;
+       struct sk_buff *skb;
+       int len, delta = 0;
+
+       rcu_read_lock();
+       xdp_prog = rcu_dereference(priv->xdp_prog);
+       if (xdp_prog) {
+               struct xdp_buff xdp;
+               u32 act;
+
+               xdp.data_hard_start = frame->data - frame->headroom;
+               xdp.data = frame->data;
+               xdp.data_end = frame->data + frame->len;
+               xdp.data_meta = frame->data - frame->metasize;
+               xdp.rxq = &priv->xdp_rxq;
+
+               act = bpf_prog_run_xdp(xdp_prog, &xdp);
+
+               switch (act) {
+               case XDP_PASS:
+                       delta = frame->data - xdp.data;
+                       break;
+               default:
+                       bpf_warn_invalid_xdp_action(act);
+               case XDP_ABORTED:
+                       trace_xdp_exception(priv->dev, xdp_prog, act);
+               case XDP_DROP:
+                       goto err_xdp;
+               }
+       }
+       rcu_read_unlock();
+
+       headroom = frame->data - delta - (void *)frame;
+       len = frame->len + delta;
+       skb = veth_build_skb(frame, headroom, len, 0);
+       if (!skb) {
+               xdp_return_frame(frame);
+               goto err;
+       }
+
+       skb->protocol = eth_type_trans(skb, priv->dev);
+err:
+       return skb;
+err_xdp:
+       rcu_read_unlock();
+       xdp_return_frame(frame);
+
+       return NULL;
+}
+
 static struct sk_buff *veth_xdp_rcv_skb(struct veth_priv *priv,
                                        struct sk_buff *skb)
 {
@@ -372,7 +444,10 @@ static int veth_xdp_rcv(struct veth_priv *priv, int budget)
                if (!ptr)
                        break;
 
-               skb = veth_xdp_rcv_skb(priv, ptr);
+               if (veth_is_xdp_frame(ptr))
+                       skb = veth_xdp_rcv_one(priv, veth_ptr_to_xdp(ptr));
+               else
+                       skb = veth_xdp_rcv_skb(priv, ptr);
 
                if (skb)
                        napi_gro_receive(&priv->xdp_napi, skb);
-- 
2.14.3