[net-next PATCH v4 5/6] virtio_net: add XDP_TX support

@@ -330,12 +330,43 @@ 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;
+	int err;
+
+	/* 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);
+
+	num_sg = 1;
+	sg_init_one(sq->sg, xdp->data, xdp->data_end - xdp->data);
+	err = virtqueue_add_outbuf(sq->vq, sq->sg, num_sg,
+				   xdp->data, GFP_ATOMIC);
+	if (unlikely(err))
+		put_page(virt_to_head_page(xdp->data));
+	else
+		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 +384,15 @@ 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;

@@ -391,8 +428,16 @@ static struct sk_buff *receive_big(struct net_device *dev,
 		if (unlikely(hdr->hdr.gso_type || hdr->hdr.flags))
 			goto err_xdp;
 		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();
 

@@ -407,6 +452,7 @@ static struct sk_buff *receive_big(struct net_device *dev,
 err:
 	dev->stats.rx_dropped++;
 	give_pages(rq, page);
+xdp_xmit:
 	return NULL;
 }
 

@@ -425,6 +471,8 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 	struct bpf_prog *xdp_prog;
 	unsigned int truesize;
 
+	head_skb = NULL;
+
 	rcu_read_lock();
 	xdp_prog = rcu_dereference(rq->xdp_prog);
 	if (xdp_prog) {

@@ -449,8 +497,16 @@ static struct sk_buff *receive_mergeable(struct net_device *dev,
 			goto err_xdp;
 
 		act = do_xdp_prog(vi, xdp_prog, page, offset, 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();
 

@@ -528,6 +584,7 @@ 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;
 }